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1
Seo, Younghoon, Kwanghyun Cho i Kanghyun Nam. "Integrated Yaw Stability Control of Electric Vehicle Equipped with Front/Rear Steer-by-Wire Systems and Four In-Wheel Motors". Electronics 11, nr 8 (18.04.2022): 1277. http://dx.doi.org/10.3390/electronics11081277.
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This paper presents the integrated motion control method for an electric vehicle (EV) equipped with a front/rear steer-by-wire (SbW) system and four in-wheel motor (IWM). The proposed integrated motion control method aims to maintain stable cornering. To maintain vehicle agility and stability, the lateral force and yaw rate commands of the vehicle are generated by referring to the neutral steering characteristics. The driver’s driving force command, the lateral force command based on the bicycle model, and the yaw moment generated by the high-level controller are distributed into the driving force of each wheel and the lateral force of the front and rear wheels by the yaw moment distribution. Finally, the distributed forces are directly controlled by a low-level controller. To directly control the forces, a driving force observer and a lateral force observer were introduced via driving force estimation in the IWMs and rack force estimation in the SbW system. The control performance is verified through computer simulations.
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Fu, Yaomin, i Sheldon Cherry. "Simplified seismic code design procedure for friction-damped steel frames". Canadian Journal of Civil Engineering 26, nr 1 (1.02.1999): 55–71. http://dx.doi.org/10.1139/l98-043.
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This paper describes the development of a proposed seismic design procedure for friction-damped steel structures, which employs the lateral force provisions used in many modern building codes. Closed-form expressions are first derived that relate the normalized response of a single degree of freedom friction-damped system with the system parameters, such as bracing stiffness ratio, damper slip ratio, and frame member ductility. A parametric analysis is then used to reveal that the seismic displacement of a friction-damped frame can be controlled by combining the frame stiffness with the bracing stiffness of the friction damper component, while the seismic force can be controlled by the damper slip force. A force modification factor (equivalent to the code R-factor) and displacement estimate for a friction-damped system are next determined. The single degree of freedom results are subsequently used to develop expressions for dealing with the multi degree of freedom situation, which permits the seismic lateral force design procedure adopted by many current building codes to be applied to friction-damped systems. The proposed procedure allows the frame response to be controlled so that the displacement can be limited to small magnitudes and the overall structural shape to an essentially straight-line deformation. Design examples illustrate that friction-damped frame systems are economical and offer a better overall response performance than that provided by conventional systems under the design earthquake.Key words: passive energy dissipation system, friction damper, steel frame, design procedure, static analysis.
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Terashima, Kazuhiko, Takanori Miyoshi, Keisuke Mouri, Hideo Kitagawa i Panya Minyong. "Hybrid Impedance Control of Massage Considering Dynamic Interaction of Human and Robot Collaboration Systems". Journal of Robotics and Mechatronics 21, nr 1 (20.02.2009): 146–55. http://dx.doi.org/10.20965/jrm.2009.p0146.
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This paper proposes an intelligent massage control system that uses a multi-fingered robot hand with hybrid impedance control, which is able to recreate the movement and force of a human massage therapist. Therefore, various massage points, such as changes in the stiffness of human skin muscle, can be controlled by using an impedance control method. A hybrid impedance control, comprised of position-based and force-based control methods, was developed. The position-based impedance control is used to control the lateral position of massage on the human skin muscle. On the other hand, the force-based impedance control is used to control the force of the vertical direction on human skin muscle. This paper also identifies human skin muscle through robot perception of impedance to decide on the parameters of the impedance controller. A strategy using impedance control to implement an adaptive control system is presented, under the conditions of both soft and hard skin and muscle. The effectiveness of this massage control system using a multi-fingered robot hand with hybrid impedance control is demonstrated through realistic massage experiments involving pushing and rubbing motions.
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Dinarelli, Simone, Andrzej Sikora, Angela Sorbo, Marco Rossi i Daniele Passeri. "Atomic force microscopy as a tool for mechanical characterizations at the nanometer scale". Nanomaterials and Energy 12, nr 2 (1.06.2023): 1–10. http://dx.doi.org/10.1680/jnaen.23.00016.
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The design, optimization, and realization of innovative nanocomposite materials for advanced applications in a broad range of fields, from energy, automotive, photonics, to biology and nanomedicine require the capability to characterize their physical (e.g., mechanical, electric, magnetic...) properties from a multiscale perspective, in particular, not only at the macroscopic scale, but also at the nanometer one. In particular, methods are needed to characterize mechanical properties with nanometer lateral resolution, in order to understand the contribution of the nanosized features of the materials and the related phenomena. Atomic force microscopy (AFM) has been evolved from a tool for the morphological analysis of the sample surface to an integrated platform for the physicochemical characterization of samples. Current AFM systems host several advanced techniques for the mechanical characterization of materials with high speed and high lateral resolution in a broad range of mechanical moduli, e.g., from stiff samples (e.g., coatings, crystals…) to soft materials (e.g., polymers, biological samples...), in different environments (e.g., air, vacuum, liquid), and conditions (controlled humidity, controlled temperature). Here, short review of AFM based methods for the nanomechanical characterization of materials, in particular force spectroscopy, is reported, with emphasis on the materials which can be analyzed.
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Zheng, Liang, i Jun Ye. "Analysis of the Lateral Stability for Four-Wheel Independent Driving Electric Vehicles". Applied Mechanics and Materials 590 (czerwiec 2014): 394–98. http://dx.doi.org/10.4028/www.scientific.net/amm.590.394.
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The four-wheel independent driving EVs have been considered as the hot spot due to their excellent controlling capability of the driving force distribution in recent years. In order to achieve the excellent control capability of electric drive systems, the mechanical properties and performance need to be investigated and evaluated. In this paper, the lateral stability of four-wheel independent driving EVs is studied and the major factors are investigated. Results of the analysis indicate that the sideslip angle of the vehicle should be controlled at a small value. Under this condition, the yaw rate plays a key role on the lateral stability of the vehicle. The results in this research provide a solid guidance to considerably improve the lateral stability and the active safety of the EVs, in both theoretical and practical aspects.
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Volk, János, János Radó, Zsófia Baji i Róbert Erdélyi. "Mechanical Characterization of Two-Segment Free-Standing ZnO Nanowires Using Lateral Force Microscopy". Nanomaterials 12, nr 23 (22.11.2022): 4120. http://dx.doi.org/10.3390/nano12234120.
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Mechanical characterization of quasi one-dimensional nanostructures is essential for the design of novel nanoelectromechanical systems. However, the results obtained on basic mechanical quantities, such as Young’s modulus and fracture strength, show significant standard deviation in the literature. This is partly because of diversity in the quality of the nanowire, and partly because of inappropriately performed mechanical tests and simplified mechanical models. Here we present orientation-controlled bending and fracture studies on wet chemically grown vertical ZnO nanowires, using lateral force microscopy. The lateral force signal of the atomic force microscope was calibrated by a diamagnetic levitation spring system. By acquiring the bending curves of 14 nanowires, and applying a two-segment mechanical model, an average bending modulus of 108 ± 17 GPa was obtained, which was 23% lower than the Young’s modulus of bulk ZnO in the [0001] direction. It was also found that the average fracture strain and stress inside the nanowire was above 3.1 ± 0.3 % and 3.3 ± 0.3 GPa, respectively. However, the fracture of the nanowires was governed by the quality of the nanowire/substrate interface. The demonstrated technique is a relatively simple and productive way for the accurate mechanical characterization of vertical nanowire arrays.
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Rajput, Harsh Raj. "Stresses & Strains in Plate Girder with Different Bracing Systems under Combination of Loadings". International Journal for Research in Applied Science and Engineering Technology 9, nr 10 (31.10.2021): 722–28. http://dx.doi.org/10.22214/ijraset.2021.38485.
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Abstract: Lateral buckling is one of the most important factors in the design of steel plate girder. This buckling in the girder can be controlled by many methods. The most popular method is to add the intermediate bracing systems along the length of girder. The unsafely designed intermediate bracing systems can easily lead to serious consequences in the construction stage due to lateral buckling by torsion which happens rapidly and suddenly when the internal force in girder exceeds the ultimate value. Reversely, if the intermediate bracing systems are designed excessively, their specific stiffness will be larger than the required one then it is very costly in both material and installing process In the present study different types of torsional bracing systems are used in twin plate girder of span 8m. As the behavior of plate girders with different type of bracing system changes differently along the length and depth. Changing the layout of bracing systems could also make the design easy and more economical. Keywords: Cross-frame Bracings, Horizontal Bracings, Plate Girder, Finite Element Analysis
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Haghshenas-Jaryani, Mahdi. "Dynamics and Computed-Muscle-Force Control of a Planar Muscle-Driven Snake Robot". Actuators 11, nr 7 (16.07.2022): 194. http://dx.doi.org/10.3390/act11070194.
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This paper presents the dynamic formulation of an artificial-muscle-driven and computed-muscle–force control for the planar locomotion of a snake robot. The snake robot uses a series of antagonistic pneumatic artificial muscles, assembled at the joints, to generate the locomotion. Kinematics of the artificial-muscle-driven robot in the joint and Cartesian spaces was derived with respect to the muscles’ motion. The Lagrangian mechanics was employed for the formulation of the dynamic model of the robot and deriving the equations of motion. A model-based computed-muscle-force control was designed to track the desired paths/trajectories in Cartesian space. The feedback linearization method based on a change of coordinate was utilized to determine an equivalent linear (input-to-state) system. Then, a full state feedback control law was designed, which satisfies the stability and tracking problems. The performance of the dynamic model and the controller were successfully demonstrated in simulation studies for tracking a circle-shape path and a square-shape path with a constant linear velocity while generating the lateral undulation gait. The results indicate a low magnitude of tracking errors where the controlled muscle force are bounded to the actual pneumatic artificial muscle’s limitations.
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Thompson, J. Michael T. "Advances in Shell Buckling: Theory and Experiments". International Journal of Bifurcation and Chaos 25, nr 01 (styczeń 2015): 1530001. http://dx.doi.org/10.1142/s0218127415300013.
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In a recent feature article in this journal, coauthored by Gert van der Heijden, I described the static-dynamic analogy and its role in understanding the localized post-buckling of shell-like structures, looking exclusively at integrable systems. We showed the true significance of the Maxwell energy criterion load in predicting the sudden onset of "shock sensitivity" to lateral disturbances. The present paper extends the survey to cover nonintegrable systems, such as thin compressed shells. These exhibit spatial chaos, generating a multiplicity of localized paths (and escape routes) with complex snaking and laddering phenomena. The final theoretical contribution shows how these concepts relate to the response and energy barriers of an axially compressed cylindrical shell. After surveying NASA's current shell-testing programme, a new nondestructive technique is proposed to estimate the "shock sensitivity" of a laboratory specimen that is in a compressed metastable state before buckling. A probe is used to measure the nonlinear load-deflection characteristic under a rigidly applied lateral displacement. Sensing the passive resisting force, it can be plotted in real time against the displacement, displaying an equilibrium path along which the force rises to a maximum and then decreases to zero: having reached the free state of the shell that forms a mountain-pass in the potential energy. The area under this graph gives the energy barrier against lateral shocks. The test is repeated at different levels of the overall compression. If a symmetry-breaking bifurcation is encountered on the path, computer simulations show how this can be suppressed by a controlled secondary probe tuned to deliver zero force on the shell.
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Switkes, Joshua P., Eric J. Rossetter, Ian A. Coe i J. Christian Gerdes. "Handwheel Force Feedback for Lanekeeping Assistance: Combined Dynamics and Stability". Journal of Dynamic Systems, Measurement, and Control 128, nr 3 (21.11.2005): 532–42. http://dx.doi.org/10.1115/1.2229256.
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Lanekeeping assistance could save thousands of lives each year by maintaining lane position in the absence of driver steering commands. In order to work smoothly with the driver, handwheel force feedback must be an integral part of such a system. Here we combine force feedback with a lanekeeping controller based on lateral and heading error. In addition to force feedback replicating the feel in a conventional vehicle, the force can be based on the level of lanekeeping assistance being given. This coupling of the force feedback and assistance systems can destabilize the vehicle if not designed properly. Linear modeling verified by experiments shows the effect of varying the gains on both the force feedback and the lanekeeping assistance itself. In this analysis we show that within a range of values that feel reasonable to the driver, changes to the lanekeeping controller or force feedback can have marked effects on the response of the vehicle. It also shows that stability of the system can be ensured by injecting artificial damping or reproducing the on-center characteristics of a conventional vehicle. The analysis allows the force feedback designer to determine a range of stable force feedback gains, from which a set most acceptable to the driver can be chosen.
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Kligerman, Y., i O. Gottlieb. "Dynamics of a Rotating System With a Nonlinear Eddy-Current Damper". Journal of Vibration and Acoustics 120, nr 4 (1.10.1998): 848–53. http://dx.doi.org/10.1115/1.2893910.
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We investigate the nonlinear dynamics and stability of a rotating system with an electromagnetic noncontact eddy-current damper. The damper is modeled by a thin nonmagnetic disk that is translating and rotating with a shaft in an air gap of a direct current electromagnet. The damper dissipates energy of the rotating system lateral vibration through induced eddy-currents. The dynamical system also includes a cubic restoring force representing nonlinear behavior of rubber o-rings supporting the shaft. The equilibrium state of the balanced rotating system with an eddy-current damper becomes unstable via a Hopf bifurcation and exact solutions for the limit cycle radius and frequency of the self-excited oscillation are obtained analytically. Forced vibration induced by the rotating system mass imbalance is also investigated analytically and numerically. System response includes periodic and quasiperiodic solutions. Stability of the periodic solutions obtained from the balanced self-excited motion and the imbalance forced response is analyzed by use of Floquet theory. This analysis enables an explanation of the nonlinear dynamics and stability phenomena documented for rotating systems controlled by electromagnetic eddy-current dampers.
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Jenck, Orianne, Armita Obaei, Fabrice Emeriault i Christophe Dano. "Effect of Horizontal Multidirectional Cyclic Loading on Piles in Sand: A Numerical Analysis". Journal of Marine Science and Engineering 9, nr 2 (23.02.2021): 235. http://dx.doi.org/10.3390/jmse9020235.
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Foundations of offshore and nearshore wind energy production systems are subjected to multidirectional and cyclic loads, due to the combined action of wind and waves and in the particular case of mutualized anchor foundations for floating wind turbines, to the phase shift between the loads generated in the adjacent anchored turbines. This article presents a three-dimensional numerical model developed with FLAC3D to analyse the impact of the change in direction of the horizontal load during the cycles. The typical case of a 1.7 m diameter and 10 m-long pile founded in a dense homogeneous sand is considered. A specific procedure has been implemented to apply force-controlled cycles with a change in lateral load direction. The results are compared to mono-directional lateral cyclic loads with the same average and cyclic forces. The results of the parametric study highlight the effect of the average value and amplitude of the cyclic loading on the accumulation of pile head horizontal displacements during the cycles. When a multidirectional cyclic loading is applied, it also leads to an accumulation of the deviated horizontal displacements, and the resulting accumulated horizontal displacements are larger than for a mono-directional cyclic loading of the same amplitude.
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Ferrara, Marco. "Amplitude controlled oscillator for lateral force microscopy. High sensitivity and cheap and compact design without the use of lock-in detection systems". Nanotechnology 14, nr 4 (14.02.2003): 427–32. http://dx.doi.org/10.1088/0957-4484/14/4/304.
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Singh, Rahul Kumar, Mayank Tiwari, Anpeksh Ambreesh Saksena i Aman Srivastava. "Analysis of a Compact Squeeze Film Damper with Magneto Rheological Fluid". Defence Science Journal 70, nr 2 (9.03.2020): 122–30. http://dx.doi.org/10.14429/dsj.70.12788.
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Rotor systems play vital role in many modern day machinery such as turbines, pumps, aeroengines, gyroscopes, to name a few. Due to unavoidable unbalance in the rotor systems, there are lateral and torsional vibrations. Ignoring these effects may cause the system serious damages, which sometimes lead to catastrophic failures. Vibration level in rotor systems is acceptable within a range. Focus in this work is to minimize the vibration level to the acceptable range. One of the ways vibration level can be minimised is by means of providing damping. To accomplish this task in this work a new concept squeeze film damper is made by electro discharge machining which is compact in configuration, is filled with magneto-rheological (MR) fluid and tested out on one support of a Jeffcott rotor. This compact squeeze film damper (SFD) produces damping in a compact volume of the device compared to a conventional SFD. MR fluid is a smart fluid, for which apparent viscosity changes with the application of external magnetic field. This compact damper with MR fluid provides the variable damping force, controlled by an external magnetic field. In this work, proportional controller has been used for providing the control feedback. This MR damper is seen to reduce vibrations in steady state and transient input to the Jeffcott rotor. Parametric study for important design parameters has been done with the help of the simulation model. These controlled dampers can be used for reducing vibrations under different operating conditions and also crossing critical speed.
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Shmerling, Assaf, i Matthias Gerdts. "A Design Methodology for the Seismic Retrofitting of Existing Frame Structures Post-Earthquake Incident Using Nonlinear Control Systems". Buildings 12, nr 11 (4.11.2022): 1886. http://dx.doi.org/10.3390/buildings12111886.
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A structural design methodology for retrofitting weakened frame systems following earthquakes is developed and presented. The design procedure refers to frame systems in their degraded strength and stiffness states and restores their dynamic performance using nonlinear control systems. The control law associated with the employed systems regards the gains between the negative state feedback and the control force, which consists of linear, nonlinear, and hysteretic portions. Structural optimization is introduced in designing the nonlinear control systems, and the controller gains are optimized using the fixed-point iteration to improve the frame system’s dynamic performance. The fixed-point iteration method relates to first-order PDE equations; hence, a new state-space formulation for weakened inelastic frame systems is developed and presented using the frame system’s lateral force equilibrium equation. The design scheme and optimization strategy differ from designing passive control systems, given that the nonlinear control system’s force consists of linear, nonlinear, and hysteretic portions. The utilization of the fixed-point iteration in the structural design area is by itself a novel application due to its robustness in addressing the gains of any type of nonlinear control system. This paper’s nonlinear control system chosen to exhibit the application is Buckling Restrained Braces (BRBs) since force consists of linear and hysteretic portions. The implementation of hysteretic control force is rare in structural control applications. In the case of BRBs, the fixed-point iteration optimizes the cross-sectional areas. Two system optimization examples of 3-story and 15-story inelastic frames are provided and described. The examples demonstrate the fixed-point iteration’s applicability and robustness in optimizing control gains of nonlinear systems and regulating the dynamic response of weakened frame structures.
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Godbolt, Bryan, i Alan F. Lynch. "An unmanned helicopter control with partial small body force compensation: Experimental results". Robotica 36, nr 10 (3.07.2018): 1436–53. http://dx.doi.org/10.1017/s0263574718000486.
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SUMMARYA generally accepted helicopter model used for control includes the effect of Small Body Forces (SBF) which couple the vehicle's rotational subsystem inputs to its translational dynamics. SBF result from tail rotor thrust and lateral forces due to main rotor flapping. It is well-known that SBF lead to a theoretically challenging stabilization problem for the tracking error dynamics. Hence, much of the existing work has neglected SBF in order to simplify control design. We design a controller that directly compensates the influence of the tail rotor component of the SBF. The design is validated in simulation and flight tests.
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Chien, Pai-Chen, i Chih-Keng Chen. "Integrated Chassis Control and Control Allocation for All Wheel Drive Electric Cars with Rear Wheel Steering". Electronics 10, nr 22 (22.11.2021): 2885. http://dx.doi.org/10.3390/electronics10222885.
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This study investigates a control strategy for torque vectoring (TV) and active rear wheel steering (RWS) using feedforward and feedback control schemes for different circumstances. A comprehensive vehicle and combined slip tire model are used to determine the secondary effect and to generate desired yaw acceleration and side slip angle rate. A model-based feedforward controller is designed to improve handling but not to track an ideal response. A feedback controller based on close loop observation is used to ensure its cornering stability. The fusion of two controllers is used to stabilize a vehicle’s lateral motion. To increase lateral performance, an optimization-based control allocation distributes the wheel torques according to the remaining tire force potential. The simulation results show that a vehicle with the proposed controller exhibits more responsive lateral dynamic behavior and greater maximum lateral acceleration. The cornering safety is also demonstrated using a standard stability test. The driving performance and stability are improved simultaneously by the proposed control strategy and the optimal control allocation scheme.
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Wang, Junyang, Hongyu Zheng i Changfu Zong. "Longitudinal and lateral dynamics control of automatic lane change system". Transactions of the Institute of Measurement and Control 41, nr 15 (25.06.2019): 4322–38. http://dx.doi.org/10.1177/0142331219856196.
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The urgency of extending functionalities of current advanced driver assistance systems (ADAS), and eventually progressing to highly automated highway driving necessitates the design of automatic lane change system. This paper presents an automatic lane change system targeting on discretional lane change scenario in highway driving. Assuming motion signals of all participants to be available, the MOBIL model is employed as the decision module. The functionality of the adaptive cruise controller is extended to realize dual-target tracking, so as to prevent abrupt acceleration change provoked by the sudden switch of the leading vehicle during the lane change. For the lateral part, a hierarchical trajectory planning algorithm, which combines parametric function and learning-based technique, is proposed to account for uncertainties of driver characteristics in different traffic situations. The trajectory is then tracked by a low-level controller based on model predictive control (MPC) theory, which employs a force input model to predict the motion of the vehicle, and formulates environment envelope and handling limits as constraints. The proposed algorithm is validated through simulations of typical scenarios. Overall, this paper lays a solid foundation for the prototype of ADAS regarding lane change.
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Zhu, Limeng, Haipeng Yan, Po-Chien Hsiao i Jianhua Zhang. "Hysteretic Behavior of Composite Vertical Connection Structures used in Prefabricated Shear Wall Systems". International Journal of Structural Stability and Dynamics 20, nr 06 (czerwiec 2020): 2040007. http://dx.doi.org/10.1142/s0219455420400076.
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An innovative composite vertical connecting structure (CVC) with capacity carrying and energy-dissipating ability is proposed in this study, which could be used in prefabricated composite shear wall structural systems to enhance the resilience and seismic performance of structural system. The CVC structure is mainly composed of three parts, including the connecting zone, the capacity bearing zone characterized by high strength and elastic deforming ability, and the energy-dissipating zone assembled by replaceable metal dampers. The low-yield strength steel and high-strength steel are used, respectively, for the metal dampers in the energy-dissipating zone and the concrete-filled high-strength steel tubes in the bearing capacity zone to enhance the energy dissipation and self-centering abilities of CVC structures. The working mechanism is analyzed and validated through finite element models built in ABAQUS. The hysteretic behavior is simulated to evaluate their performance. First, the metal dampers are designed. The theoretical and finite elemental parametric analysis are carried out. According to the simulation results, the “Z-shaped” metal dampers exhibit better energy-dissipating ability than the rectangular shape, in which the “Z-shaped” metal dampers with 45∘ show the best performance. Simultaneously, the results of the models calculated by the finite element method and theoretical analysis work very well with each other. Furthermore, seven FE models of shear walls with CVC structures are designed. Monotonic and cyclic loading simulations are conducted. The failure modes and comprehensive mechanical performance are investigated and evaluated according to their calculated force–displacement curves, skeleton curves, and ductility coefficients. The results indicate that the CVC structure delivered preferable lateral-bearing capacity and displacement ductility. Finally, according to available design standards, the lateral stiffness of CVC structures could be conventionally controlled and some practical design recommendations are discussed.
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Qian, Xingguo, Chunyan Wang i Wanzhong Zhao. "Rollover prevention and path following control of integrated steering and braking systems". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, nr 6 (3.01.2020): 1644–59. http://dx.doi.org/10.1177/0954407019896502.
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In the process of preventing rollover, the expected path of the driver to achieve better anti-rollover effect is often ignored, which may lead to the deviation of vehicle from the original path. Aiming at this problem, this paper considers both anti-rollover and path tracking performance, and proposes an integrated controller based on active steering and active braking. On the one hand, it can reduce the lateral acceleration and rollover risk by restraining the front wheel angle as tracking the driver’s expected path. On the other hand, through reasonably distributing the braking force of the four tires, it can offset the additional yaw moment caused by uneven distribution and reduce the impact on vehicle trajectory as the risk of rollover occurs. In addition, an improved index of rollover is put forward to give early warning to the future moment and to prevent rollover accident effectively. Simulation and hardware-in-the-loop test results show that the proposed integrated controller can ensure that the vehicle tracks the expected path well and achieves rollover prevention effectively.
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Acosta, M., S. Kanarachos i M. Blundell. "Virtual tyre force sensors: An overview of tyre model-based and tyre model-less state estimation techniques". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 232, nr 14 (11.10.2017): 1883–930. http://dx.doi.org/10.1177/0954407017728198.
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This paper presents a comprehensive literature review on tyre force estimation and road grip recognition approaches. With the development of modern automotive control systems, a precise estimation of a large number of vehicle states is necessary to guarantee a robust actuation of the controller. Moreover, the estimation of these states must be carried out in a cost-effective and reliable way. The aim of this work is to provide a solid base for the development of automotive virtual sensors, and in particular, virtual tyre force sensors. An initial overview of the tyre force estimation problem is provided in the first section. Tyre and vehicle modelling, as well as observers for vehicle state estimation, are covered in detail in the second section. The third section introduces a brief discussion regarding the main limitations of direct tyre force measurement approaches. In the following sections, relevant works regarding three-axis tyre force estimation and road grip recognition are discussed. The review is structured around longitudinal force estimation, lateral force estimation, combined tyre force estimation, tyre self-alignment torque estimation and vertical tyre force estimation. Within each section, the most significant road grip identification approaches are introduced. An additional section, Road slope and bank angle compensation, describes relevant work on estimation methods for global chassis orientation. A brief summary of the presented approaches is provided in the section Summary of presented approaches. Finally, relevant conclusions and further research steps are given in the last section.
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Whidborne, James F., Arthur P. Mendez i Alastair Cooke. "Effect of Rotor Tilt on the Gust Rejection Properties of Multirotor Aircraft". Drones 6, nr 10 (18.10.2022): 305. http://dx.doi.org/10.3390/drones6100305.
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In order to operate safely in windy and gusty conditions, multirotor VTOL aircraft require gust resilience. This paper shows that their gust rejection properties can be improved by applying a small amount of fixed outward rotor tilt. Standard aerodynamic models of the rotors are incorporated into two dynamic models to assess the gust rejection properties. The first case is a conceptual birotor planar VTOL aircraft. The dependence of the trim and stability on the tilt angle are analyzed. The aircraft is stabilized using a pole-placement approach in order to obtain consistent closed-loop station-keeping performance in still air. The effect of gusts on the resulting response is determined by simulation. The second case study is for a quadrotor with a 10° outward rotor tilt. The aerodynamic coefficients are analyzed for trimmed station-keeping over a range of steady wind speeds. An LQR controller is used to apply station-keeping that includes integral action, and the gust responses are again obtained using simulation. The results show that the outward rotor tilt causes the aircraft to pitch down into a lateral gust, providing lateral force that opposes the gust and so significantly improving the gust rejection properties.
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Abbas Zaidi, Nayyer, i Shafaat Ahmed Bazaz. "Development of a reliable microgripper system based on failure analysis". Industrial Robot: An International Journal 41, nr 3 (13.05.2014): 318–26. http://dx.doi.org/10.1108/ir-04-2014-0322.
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Purpose – The purpose of this paper is to present the design of a microgripper system that comprises a dual jaw actuation mechanism with contact sensing. Design/methodology/approach – Interdigitated lateral comb-drive-based electrostatic actuator is used to move the gripper arms. Simultaneous contact sensing of the gripper jaws has been achieved through transverse comb-based capacitive sensor. The fabricated microgripper produces a displacement of 16 μm at gripper jaws for an applied actuation voltage of 45 V. Findings – It is observed that the microgripper fails to operate for the maximum performance limits (70 μm jaws displacement) and produces uncontrolled force at the tip of the jaws > 45 V. Originality/value – A novel behavioral model of the microgripper system is proposed using the fabricated dimensions of the system to carry out a detailed analysis to understand the cause of this failure. The failure analysis shows that the microgripper system failed to operate in its designed limits due to the presence of side instability in the designed combs structure. Our proposed failure model helps in redesigning the actuator to ensure its operation above 45 V so that the gripper jaw can be displaced to its maximum limit of 70 μm and also result in the increase of the controlled force from 250 to 303 μN at the microgripper jaws.
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Hosseini-Pishrobat, Mehran, Mirali Seyedzavvar i Mohammad Ali Hamed. "Robust dynamic surface control of vehicle lateral dynamics using disturbance estimation". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, nr 5 (1.03.2018): 1081–99. http://dx.doi.org/10.1177/0954407018757619.
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This paper reports a disturbance estimation-based dynamic surface control method for stabilizing vehicle lateral dynamics through yaw moment control. Based on the single track vehicle model, an uncertain model of the vehicle lateral dynamics is developed which represents the effect of parametric uncertainty and lateral tire force nonlinearity by mismatched, lumped total disturbances. In this model, the longitudinal velocity of the vehicle is considered as a time-varying parameter. Using the developed mathematical vehicle model, an extended state observer is proposed to estimate the total disturbance signals. Next, a dynamic surface controller is designed with the objective of tracking the desired lateral velocity generated by a linear two-degrees-of-freedom vehicle dynamics. The dynamic surface controller uses the estimated disturbances of the extended state observer as feedforward inputs to compensate for the effects of the total disturbances. To achieve an improved robust performance against disturbance estimation errors, the [Formula: see text] control technique is incorporated into the DSC design. To this end, using a norm-bounded representation of the longitudinal velocity, the control design is formulated as the feasibility of a finite number of linear matrix inequalities. The stability and robustness of the extended state observer and the dynamic surface control systems are analyzed in a Lyapunov framework and the required mathematical proofs are presented. Considering a lane change and a J-turn maneuver, extensive numerical simulations are performed to show the effectiveness of the proposed control system. The results confirm the improved performance of the closed-loop system compared to the open-loop one, in various driving and road conditions.
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Artigue, F., M. Y. Amirat i J. Pontnau. "Isoelastic behavior of parallel robots". Robotica 7, nr 4 (październik 1989): 323–25. http://dx.doi.org/10.1017/s0263574700006718.
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SUMMARYThis paper presents a particular architecture of a parallel robot which is characterized by a diagonal stiffness matrix. This result suggests the use of a parallel robot in the final phase of insertion as a passive compliance device. The stiffness rate of this device is controlled by the gain of the feedback loop. As the correction of small angular misalignments due to contact forces do not generate lateral errors and vice versa, we have the equivalent of an isoelastic swivel.
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Yao, Jialing, Meng Wang, Zhihong Li i Yunyi Jia. "Research on Model Predictive Control for Automobile Active Tilt Based on Active Suspension". Energies 14, nr 3 (28.01.2021): 671. http://dx.doi.org/10.3390/en14030671.
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To improve the handling stability of automobiles and reduce the odds of rollover, active or semi-active suspension systems are usually used to control the roll of a vehicle. However, these kinds of control systems often take a zero-roll-angle as the control target and have a limited effect on improving the performance of the vehicle when turning. Tilt control, which actively controls the vehicle to tilt inward during a curve, greatly benefits the comprehensive performance of a vehicle when it is cornering. After analyzing the advantages and disadvantages of the tilt control strategies for narrow commuter vehicles by combining the structure and dynamic characteristics of automobiles, a direct tilt control (DTC) strategy was determined to be more suitable for automobiles. A model predictive controller for the DTC strategy was designed based on an active suspension. This allowed the reverse tilt to cause the moment generated by gravity to offset that generated by the centrifugal force, thereby significantly improving the handling stability, ride comfort, vehicle speed, and rollover prevention. The model predictive controller simultaneously tracked the desired tilt angle and yaw rate, achieving path tracking while improving the anti-rollover capability of the vehicle. Simulations of step-steering input and double-lane change maneuvers were performed. The results showed that, compared with traditional zero-roll-angle control, the proposed tilt control greatly reduced the occupant’s perceived lateral acceleration and the lateral load transfer ratio when the vehicle turned and exhibited a good path-tracking performance.
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Menendez-Aponte, Pablo, Xiangling Kong i Yunjun Xu. "An Approximated, Control Affine Model for a Strawberry Field Scouting Robot Considering Wheel–Terrain Interaction". Robotica 37, nr 9 (5.03.2019): 1545–61. http://dx.doi.org/10.1017/s0263574719000134.
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SummaryRecently, autonomous field robots have been investigated as a labor-reducing means to scout through commercial strawberry fields for disease detection or fruit harvesting. To achieve accurate over-bed and cross-bed motions, it is preferred to design the motion controller based on a precise dynamic model. Here, a dynamic model is developed for a custom-designed strawberry field robot considering terramechanic wheel–terrain interaction. Different from existing models, a torus geometry is considered for the wheels. In order to obtain a control affine model, the longitudinal force is curve-fitted using a polynomial function of the slip/skid ratio, while the lateral force is curve-fitted using an exponential function of both the slip/skid ratio and slip angle. An extended Kalman filter (EKF) is then developed to estimate the unknown parameters in the approximated model such that the state variables propagated by such a model can match experimental data. The approximated model and the EKF-based parameter estimation method are then validated in a commercial strawberry farm.
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Yang, Guang, Faxing Lu i Junfei Xu. "Research on Lateral Maneuverability of a Supercavitating Vehicle Based on RBFNN Adaptive Sliding Mode Control with Rolling Restriction and Planing Force Avoidance". Machines 11, nr 8 (19.08.2023): 845. http://dx.doi.org/10.3390/machines11080845.
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This paper addresses the lateral motion control of a supercavitating vehicle and studies its ability to maneuver. According to the unique hydrodynamic characteristics of the supercavitating vehicle, highly coupled nonlinear 6-degree-of-freedom (DOF) dynamic and kinematic models are constructed considering time-delay effects. A control scheme utilizing radial basis function (RBF) neural-network-(NN)-based adaptive sliding with planing force avoidance is proposed to simultaneously control the longitudinal stability and lateral motion of the supercavitating vehicle in the presence of external ocean-induced disturbances. The online estimation of nonlinear disturbances is conducted in real time by the designed NN and compensated for the dynamic control laws. The adaptive laws of the NN weights and control parameters are introduced to improve the performance of the NN. The least squares method is utilized to solve the actuator control efforts with rolling restriction in real-time online. Rigorous theoretical proofs based on the Lyapunov theory prove the globally asymptotic stability of the proposed controller. Finally, numerical simulations were performed to obtain maximum maneuverability and verify the effectiveness and robustness of the proposed control scheme.
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Zheng, Lufeng, Yongjie Lu, Haoyu Li i Junning Zhang. "Anti-Rollover Control and HIL Verification for an Independently Driven Heavy Vehicle Based on Improved LTR". Machines 11, nr 1 (14.01.2023): 117. http://dx.doi.org/10.3390/machines11010117.
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The rollover evaluation index provides an important threshold basis for the anti-rollover control system of vehicle. Regarding the rollover risk of independently driven heavy-duty vehicles, a new rollover evaluation index is proposed, and the feasibility of the improved index was verified through hierarchical control and HIL (hardware-in-the-loop) experiments. Based on an 18-DOF spatial dynamics model of a heavy-duty vehicle, the improved LTR (load transfer rate) index was obtained to describe the dynamic change in the tire’s vertical load. It replaces the suspension force and the vertical inertia force of the unsprung load mass. It avoids the problem of directly measuring or estimating the vertical load in the LTR index. Under the conditions of fishhooking and angle stepping, three types of rollover indicators were compared, and the proposed index can more sensitively identify the likelihood of rollover. In order to apply the improved rollover index to a rollover control well, a hierarchical controller based on the identification of the slip rate of the road surface, ABS control with sliding mode, variable structure and differential braking was designed. Simulations and HIL tests proved that the designed controller can accurately predict the rollover risk and avoid the rollover in time. Under the condition of J-turning, the yaw rate, slip angle and maximum lateral acceleration are reduced by 9%, 16% and 3%, respectively; under the condition of fishhooking, the maximum yaw rate, slip angle and lateral acceleration are reduced by 12%, 18% and 3%, respectively.
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Lee, Eun-Hyuk, Sang-Hoon Kim i Kwang-Seok Yun. "Three-Axis Pneumatic Haptic Display for the Mechanical and Thermal Stimulation of a Human Finger Pad". Actuators 10, nr 3 (17.03.2021): 60. http://dx.doi.org/10.3390/act10030060.
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Haptic displays have been developed to provide operators with rich tactile information using simple structures. In this study, a three-axis tactile actuator capable of thermal display was developed to deliver tactile senses more realistically and intuitively. The proposed haptic display uses pneumatic pressure to provide shear and normal tactile pressure through an inflation of the balloons inherent in the device. The device provides a lateral displacement of ±1.5 mm for shear haptic feedback and a vertical inflation of the balloon of up to 3.7 mm for normal haptic feedback. It is designed to deliver thermal feedback to the operator through the attachment of a heater to the finger stage of the device, in addition to mechanical haptic feedback. A custom-designed control module is employed to generate appropriate haptic feedback by computing signals from sensors or control computers. This control module has a manual gain control function to compensate for the force exerted on the device by the user’s fingers. Experimental results showed that it could improve the positional accuracy and linearity of the device and minimize hysteresis phenomena. The temperature of the device could be controlled by a pulse-width modulation signal from room temperature to 90 °C. Psychophysical experiments show that cognitive accuracy is affected by gain, and temperature is not significantly affected.
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Lian, Yunxiao, Yong Zhou, Jianxin Zhang, Shangjun Ma i Shuai Wu. "An Intelligent Nonlinear Control Method for the Multistage Electromechanical Servo System". Applied Sciences 12, nr 10 (17.05.2022): 5053. http://dx.doi.org/10.3390/app12105053.
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In order to meet the requirements of servo systems, including sensitive and rapid adjustment, high control and motion accuracy, and strong working adaptability, in special application fields, such as high thrust and long travel, an adaptive inversion control method is proposed for the lateral force and other nonlinear factors of multistage electromechanical servo system (MEMSS). The position tracking controller of permanent magnet synchronous motor (PMSM), based on an improved adaptive inversion method, was designed and its stability was analyzed, and the Luenberger load torque observer model of PMSM was established. The EMESS simulation model of an adaptive inversion controller was built using the Simulink platform, and the motor multibody dynamics model was established in ADAMS software. Through the joint simulation of Simulink and ADAMS software, the results of EMESS under adaptive inversion controller and traditional PID controller were compared, and the feasibility and reliability of the designed adaptive inversion controller were verified. Finally, the designed controller was tested based on the experimental platform. The experimental results show that the adaptive inversion controller designed in this paper has better robustness and stability than the traditional PID controller.
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Kreimeier, D., J. Zhu, V. Smukala, B. Buff i C. Magnus. "CAM-Solution for Two Robots Based Incremental Sheet Metal Forming". Key Engineering Materials 473 (marzec 2011): 889–96. http://dx.doi.org/10.4028/www.scientific.net/kem.473.889.
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Robot based incremental sheet metal forming (Roboforming)is a new dieless forming process, which is suitable for cost-effective manufacture of prototype parts and small batch sizes.The principle of Roboforming is based on flexible shaping through a freely programmable path-synchronous movement of two industrial robots. These two robots, which are connected to a cooperating robot system, hold respectively a forming and a supporting tool. Similar to other incremental forming methods, the final shape is produced bythe movement of the forming toolalongthe lateral direction and its gradual infeed in the depth direction. In Roboforming, there are twodifferent strategies for the synchronous movement of the supporting tool, eitheralong the outer contour onbacksideof the sheet or directly opposed to the forming tool building a forming gap.The second strategy can be combined with a force controlled method to increase the surface quality and geometricaccuracy. MThe most existing CAM systems used in numerous incremental forming approaches are only applicable for milling machines. In this paper, with the use of self-programmed postprocessors and an Application Programming Interface (API) in a CAM system, movement programs for two cooperating robots can be generated for both forming strategies to produce sheet metal parts with different sizes and complex freeform structures. This CAM-solution for Roboforming is validated bythe forming experiments.
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Zhang, Pandeng, Zhao Liu, Tao Jin, Weiqiang Chen, Yutian Zhu i Zhengzhong Zheng. "Design and analysis of five-link-rod rigid constraint support scheme for engine–accessory system vibration control". Advances in Mechanical Engineering 11, nr 10 (październik 2019): 168781401988128. http://dx.doi.org/10.1177/1687814019881281.
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Vibration generated by engine and its accessories deteriorates product performance. At present, lacking global model, mounting design of engine and accessories are separate, not conductive to solving the vibration of engine, belt, and accessories as a whole. In this article, three problems of the typical structure are analyzed, that is, the belt tension is unstable, static preloading makes engine mount design deviate, and the belt is prone to lateral vibration. Then, a rigid constraint rod is proposed to fix the center distance. The vibrational motion equation is established. By matrix analysis, the accessory mount along the rod is canceled. Then, engine and accessories can be analyzed as independent systems. Among them, the vibration isolation of the engine tends to be good, and for accessories and belts, the influences of the accessory mount stiffness on the force and torque transmission rate and belt vibration response were comprehensively evaluated, and that the infinite stiffness is presented. The innovative design of five-rod structure mainly composed of two connecting rods is obtained which does not transfer vibration perpendicular to rod and the vibration of engine, belt, and accessories are all well controlled. This experiment proves the five-link structure as a useful solution.
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Baradaran, Milad Farahanchi, i Farhad Behnamfar. "A modal seismic design procedure based on a selected level of ductility demand". Bulletin of the New Zealand Society for Earthquake Engineering 52, nr 2 (30.06.2019): 78–94. http://dx.doi.org/10.5459/bnzsee.52.2.78-94.
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Determination of seismic design forces of structures is performed by the building codes usually using response reduction (or behaviour) factors that incorporate indeterminacy and ductility capacity of lateral bearing systems. In this procedure story drifts are checked as a final design step approximately preventing stories from assuming excessive ductility demands, or seismic damage. If this procedure is reversed, a more logical seismic design approach may be developed by starting with a ductility-controlled procedure. It is the incentive of this research in which by using a large number of earthquakes, first nonlinear acceleration spectra are developed for different levels of ductility demand. Then an energy-based modal procedure is developed in which the system ductility demand is distributed between the important vibration modes based on their contribution. Finally, the developed method is applied to seismic design of several buildings selected from both regular and irregular structural systems. Comparison with a sample code design establishes success of the method in developing a more rational seismic design.
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Fradelos, Yiannis, Olga Thalla, Irene Biliani i Stathis Stiros. "Study of Lateral Displacements and the Natural Frequency of a Pedestrian Bridge Using Low-Cost Cameras". Sensors 20, nr 11 (5.06.2020): 3217. http://dx.doi.org/10.3390/s20113217.
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Vision-based techniques are frequently used to compute the dynamic deflections of bridges but they are rather computationally complicated and require demanding instrumentation. In this article, we show that it is possible to reconstruct the 2-D kinematics of flexible bridges using a simplified algorithm to analyze common video imagery. The only requirements are that the movement of the control points is clearly visible on the images and that next to each control point, there exist vertical and horizontal bridge elements defining the image scale. We applied this technique during controlled, forced excitations of a timber bridge that was stiff in the vertical but very flexible in the lateral axis because of cumulated damage. We used videos from low-cost cameras, in which the changes of the pixel coordinates of several control points during excitation events and their attenuation were clear. These videos were obtained during two annual structural health monitoring surveys using numerous sensors (Global Navigation Satellite Systems (GNSS), robotic total station (RTS), accelerometers), and hence the output of the video analysis was fully controlled. Because of various errors, the transformation of the video image coordinates into bridge coordinates yielded spurious deflections along the main axis of the bridge, which were used to control the uncertainty of our results. We found that the computed lateral deflections (i) were statistically significant, (ii) satisfied structural constraints, and (iii) were consistent with structural estimates derived from other sensors. Additionally, they provided accurate estimates of the natural frequency and the damping factor of the bridge. This approach can be applied in other cases of monitoring of flexible structures if the requirements for planar deformation, pixel resolution and scale definition are satisfied.
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Meyer, G., i K. H. Rieder. "Lateral Manipulation of Single Adsorbates and Substrate Atoms With the Scanning Tunneling Microscope". MRS Bulletin 23, nr 1 (styczeń 1998): 28–32. http://dx.doi.org/10.1557/s0883769400031432.
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The stability and precision of modern scanning-tunneling-microscope (STM) systems allow positioning of the tip on a subnanometer scale. This advancement has stimulated diverse efforts on surface modifications in the nanometer and even atomic range, as recently reviewed by Avouris. The lateral movement of individual adatoms and molecules in a controlled manner on solid surfaces and the construction of structures on a nanoscale were first demonstrated by Eigler and collaborators at 4 K. The reason for operating the STM at low temperatures (apart from increased stability and sensitivity of the STM setup itself) is the necessity to freeze the motion of single adsorbates, which are very often mobile at ambient temperatures. By selecting strongly bonded adsorbate/substrate combinations and large molecules, it was possible to extend the lateral manipulation technique even to room temperature. In the case of large molecules, not only their translational motion but also internal flexure of the molecule during the positioning process must be considered. In general, different physical and chemical interaction mechanisms between tip and sample can be exploited for atomic-scale manipulation. We will concentrate in the following on lateral manipulation where solely the forces that act on the adsorbate because of the proximity of the tip are used. This means that long-range van der Waals and short-range chemical forces can be used to move atoms or molecules along the surface. No bias voltage or tunneling current is necessary. Apart from this technique, additional advances using the effects caused by the electric field generated by the bias voltage between tip and sample and by the current flowing through the gap region can be used for atomic or molecular modification.
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Booth, P. J., R. H. Templer, A. R. Curran i S. J. Allen. "Can we identify the forces that drive the folding of integral membrane proteins?" Biochemical Society Transactions 29, nr 4 (1.08.2001): 408–13. http://dx.doi.org/10.1042/bst0290408.
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Protein folding has been at the forefront of molecular cell biology research for several years. However, integral membrane proteins have eluded detailed molecular level study until recently. One reason is the often apparently insurmountable problem of mimicking the natural membrane bilayer with lipid or detergent mixtures. There is nevertheless a large body of information on lipid properties and in particular on phosphatidylcholine and phosphatidylethanolamine lipids, which are common to many biological membranes. We have exploited this knowledge to design efficient in vitro, lipid-bilayer folding systems for membrane proteins. Bacteriorhodopsin has been used as a model system for our initial studies: we have shown that a rate-limiting apoprotein folding step and the overall folding efficiency seem to be controlled by particular properties of the lipid bilayer. The properties of interest are the stored curvature elastic energy within the bilayer and the lateral pressure that the lipid chains exert on their neighbouring folding protein. These are generic properties of the bilayer that can be achieved with simple mixtures of many types of biological lipid and seem to be important in vivo.
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Kumar, Parichit, Saksham Malik, Ehsan Toyserkani i Mir Behrad Khamesee. "Development of an Electromagnetic Micromanipulator Levitation System for Metal Additive Manufacturing Applications". Micromachines 13, nr 4 (9.04.2022): 585. http://dx.doi.org/10.3390/mi13040585.
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Magnetism and magnetic levitation has found significant interest within the field of micromanipulation of objects. Additive manufacturing (AM), which is the computer-controlled process for creating 3D objects through the deposition of materials, has also been relevant within the academic environment. Despite the research conducted individually within the two fields, there has been minimal overlapping research. The non-contact nature of magnetic micromanipulator levitation systems makes it a prime candidate within AM environments. The feasibility of integrating magnetic micromanipulator levitation system, which includes two concentric coils embedded within a high permeability material and carrying currents in opposite directions, for additive manufacturing applications is presented in this article. The working principle, the optimization and relevant design decisions pertaining to the micromanipulator levitation system are discussed. The optimized dimensions of the system allow for 920 turns in the inner coil and 800 turns in the outer coil resulting in a Ninnercoil:Noutercoil ratio of 1.15. Use of principles of free levitation, which is production of levitation and restoration forces with the coils, to levitate non-magnetic conductive materials with compatibility and applications within the AM environment are discussed. The Magnetomotive Force (MMF) ratio of the coils are adjusted by incorporation of an resistor in parallel to the outer coil to facilitate sufficient levitation forces in the axial axis while producing satisfactory restoration forces in the lateral axes resulting in the levitation of an aluminum disc with a levitation height of 4.5 mm. An additional payload of up to 15.2 g (59% of mass of levitated disc) was added to a levitated aluminum disk of 26 g showing the system capability coping with payload variations, which is crucial in AM process to gradually deploy masses. The final envisioned system is expected to have positional stability within the tolerance range of a few μm. The system performance is verified through the use of simulations (ANSYS Maxwell) and experimental analyses. A novel method of using the ratio of conductivity (σ) of the material to density (ρ) of the material to determine the compatibility of the levitation ability of non-magnetic materials with magnetic levitation application is also formulated. The key advantage of this method is that it does not rely on experimental analyses to determine the levitation ability of materials.
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Tena-Colunga, Arturo, Consuleo Gómez-Soberón i Abel Mun~oz-Loustaunau. "Seismic Isolation of Buildings Subjected to Typical Subduction Earthquake Motions for the Mexican Pacific Coast". Earthquake Spectra 13, nr 3 (sierpień 1997): 505–32. http://dx.doi.org/10.1193/1.1585960.
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An analytical study on the application of different base isolation systems for original design or retrofit of typical building structures of the Mexican Pacific Coast is presented. The subject hypothetical buildings are located on hard soil conditions at Acapulco. Typical accelerograms for the Mexican subduction zone recorded during recent earthquakes were used for 3-D time-history analyses. Bidirectional input was used for the time-history analyses. The studied base isolation systems reported in this study are lead-rubber bearings (LRB) and steel-hysteretic dampers (SHD). For the original design case studies, the superstructures were designed: a) according to the seismic provisions of the building code of Guerrero state (RCGS-90) for the fixed-base condition and, b) according to an elastic design based upon a 3-D lateral force distribution consistent with dominant mode shapes for the isolated structure to yield the peak dynamic base shear transmitted by the isolation system. Material volumes for the superstructure were estimated for both the fixed-base code designs and the base-isolation designs. Important savings on the volume of concrete and steel reinforcement can be attained for the base isolated designs with respect to their counterpart fixed-base designs. Dynamic responses for the isolated structures compare favorably with those for the fixed-base structures. The study confirms many findings published in the literature regarding the effectiveness of base isolation and the effect of torsional responses. However, the study also shows that the dynamic stability of isolators is not always achieved using rational design procedures. The dynamic stability and design of the studied base isolators can be controlled by acceleration records associated to moderate earthquakes when these records are near the fault plane and by torsional responses.
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Çapa, Yuşa Uğur, Ali Ruzi Özuygur i Zekai Celep. "A study on earthquake performances of reinforced concrete buildings with various number of stories". Journal of Structural Engineering & Applied Mechanics 4, nr 2 (30.06.2021): 83–98. http://dx.doi.org/10.31462/jseam.2021.04083098.
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Seismic codes generally require that the Equivalent Seismic Load Method or the Modal Response Spectrum Method is adopted in the design of buildings. In the equivalent seismic load method, the equivalent seismic static force applied to the building is determined depending on the seismicity of the region where the building is located, the usage class of the building, the fundamental period of the building and the building mass. Later, this equivalent seismic load is reduced by the seismic load reduction factor to take into account the increase in the capacity of the system and the decrease in the seismic demand due to the nonlinear and inelastic behavior of the system, i.e., by accepting limited inelastic deformations in the building subjected to the design earthquake. Then, structural system of the building is analyzed under the reduced seismic forces in addition to the vertical loads by using the load combinations given in the design codes. The process is completed by designing the sections and the structural elements of the building. Similar processes can be implemented by using the modal response spectrum method. The difference between these two methods is consideration of the higher modes of the building instead of the first mode only and the use of the modal masses of the building for each mode, instead of the total mass of the building. In the latter method, the contributions of the higher mode are combined by using specific superposition rules. The codes assume that the structural systems designed in this way will exhibit the almost same level of inelastic deformation, i.e., the controlled damage state, regardless of the building parameters, such as the number of stories. In this study, an attempt is made to investigate the validity of this implicit acceptance. For this purpose, the buildings with a various number of stories are designed by satisfying the bare minimum requirements of the code only, as much as possible. The seismic behavior and the lateral load capacity of these buildings are examined by the static and dynamic nonlinear analyses. The ratio of the nonlinear load capacity to the reduced equivalent seismic load is evaluated depending on the number of the stories of the buildings. The results which are presented in detail yield that the buildings with a low number of stories have relatively larger nonlinear lateral load capacity-to-the reduced elastic seismic load ratio, which is not compatible with the general implicit assumption made in the seismic codes.
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Mohammadi, Sajjad, Abd-ol-Reza Sarvghad Moghaddam i Alireza Faroughi. "The effect of number and position of braced frames on column behavior of the dual steel structural system (MRF and EBF) (With a view on amplified seismic load)". Ciência e Natura 37 (21.12.2015): 277. http://dx.doi.org/10.5902/2179460x20858.
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In seismic design of structures, determination of number and position of braced frames, considering the architectural scheme of projects, is usually confronted by obstacles. Due to this fact, in some cases, selecting the best location and number of braced bays has led to mistakes in determination of their adjacent members (columns) design loads. One of the seismic design requirements of lateral resisting system is to control the columns adjacent to braced bays for load combinations of amplified seismic load, which is a function of over-strength factor of the structure. This research aims to present and introduce the best structural model of number and position of braced frames in a structural system, such as steel moment resisting frame and eccentric braces dual system; because in 3rd revision of Iranian 2800 standard of seismic provision, there are statements and criteria provided only for capacity of moment frame, not for braces. Though the amplified seismic load function is controlled in models which columns are connected to braces in 2 directions, and seismic loads are applied in those 2 directions, number of damage hinges (Exceeding CP) is significantly increased in comparison to the models with straggly braces. As the increase in axial force of these columns leads to decrease in their moment capacity (despite controlling the amplified seismic load provision), columns in dual systems that resist flexure, would be damaged and exceed the collapse threshold much sooner than other columns. This important fact is not presented in Iranian or even American codes and provisions.
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Sar, Hubert, Mateusz Brukalski i Krzysztof Rokicki. "Simulation of curvilinear motion of automobile with the use of two-degree-of-freedom flat model". Archives of Automotive Engineering – Archiwum Motoryzacji 87, nr 1 (30.03.2020): 19–32. http://dx.doi.org/10.14669/am.vol87.art2.
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Development of active safety systems of automobiles is nowadays based not only on road tests, but also on computer simulation of vehicle's curvilinear motion. To properly perform simulation, all required model parameters have to be properly estimated. The less complicated model is, the less parameters it requires. So that, it makes no sense to apply too complicated models, if we are not able to estimate parameters with relatively low error. One of the most popular is two- degree-of-freedom flat model to describe curvilinear motion of automobile. It is widely used in design and improvement of active safety systems. The article discusses the application of simple two- degree-of-freedom flat model of automobile, which requires only several parameters. These parameters are: mass of a vehicle, location of center of gravity of a vehicle, yaw mass moment of inertia of a vehicle, side-slip characteristics. Furthermore, to be able to compare simulation and measurement results, it is necessary to know some input signals such as steering wheel angle and velocity of a vehicle, recorded during road tests. In this article signal of steering wheel angle was taken from Controller Area Network (CAN) bus. In case of model of a vehicle, the Authors decided to compare the results of simulation using two different side slip characteristics known as the dependence between lateral reaction force and side slip angle: linear characteristic (constant cornering stiffness) and the characteristic represented by Pacejka’s Magic Formula in steady-state version.
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Booth, Paula J., A. Rachael Curran, Richard H. Templer, Hui Lu i Wim Meijberg. "Manipulating the folding of membrane proteins: using the bilayer to our advantage". Biochemical Society Symposia 68 (1.08.2001): 27–33. http://dx.doi.org/10.1042/bss0680027.
Pełny tekst źródłaStreszczenie:
The folding mechanisms of integral membrane proteins have largely eluded detailed study. This is owing to the inherent difficulties in folding these hydrophobic proteins in vitro, which, in turn, reflects the often apparently insurmountable problem of mimicking the natural membrane bilayer with lipid or detergent mixtures. There is, however, a large body of information on lipid properties and, in particular, on phosphatidylcholine and phosphatidylethanolamine lipids, which are common to many biological membranes. We have exploited this knowledge to develop efficient in vitro lipid-bilayer folding systems for the membrane protein, bacteriorhodopsin. Furthermore, we have shown that a rate-limiting apoprotein folding step and the overall folding efficiency appear to be controlled by particular properties of the lipid bilayer. The properties of interest are the stored curvature elastic energy within the bilayer, and the lateral pressure that the lipid chains exert on the their neighbouring folding proteins. These are generic properties of the bilayer that can be achieved with simple mixtures of biological lipids, and are not specific to the lipids studied here. These bilayer properties also seem to be important in modulating the function of several membrane proteins, as well as the function of membranes in vivo. Thus, it seems likely that careful manipulations of lipid properties will shed light on the forces that drive membrane protein folding, and will aid the development of bilayer folding systems for other membrane proteins.
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Alçiçek, Haluk E., i Cüneyt Vatansever. "Experimental investigation of link beams with perforated web section in eccentrically braced frames". Advances in Structural Engineering 25, nr 6 (17.01.2022): 1268–82. http://dx.doi.org/10.1177/13694332211073637.
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Eccentrically braced frame (EBF) system is one of the most effective lateral loads resisting systems for steel structures. In these systems, links are designed in such a way that they yield in shear not only to provide high ductility and rigidity but also to provide a high energy dissipation capacity. In particular, as the internal forces to be considered for the design of the members outside of the links must be calculated with the amplification factor based on the yielding of the links, the magnitude of the internal forces may become so large that they may not be met by the adjacent members. Therefore, it is challenging to develop an economic design for adjacent members and connections because of the high level of design loads obtained by the amplification factor. This paper studies the effect of the perforation arrangement in the web of shear link beams in eccentrically braced frames. Both experimental and numerical investigation were conducted to demonstrate the effectiveness of the link beam with slotted perforations in the web portion. Seven equivalent isolated link beam specimens with various slot-hole patterns were tested under quasi-static cyclic loading. The results of the study indicate that using slot-holes in the web portion reduces the link shear capacity significantly. The results also show that the failure mechanism of reduced link sections was controlled by fracture at end of the slot-holes and inelastic rotation capacities were varying between 0.025 rad and 0.065 rad depending on the slot-hole patterns.
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Desmond, Paula A., Peter A. Hancock i Janelle L. Monette. "Fatigue and Automation-Induced Impairments in Simulated Driving Performance". Transportation Research Record: Journal of the Transportation Research Board 1628, nr 1 (styczeń 1998): 8–14. http://dx.doi.org/10.3141/1628-02.
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A driving simulator study investigated the effect of automation of the driving task on performance under fatiguing driving conditions. In the study, drivers performed both a manual drive, in which they had full control over the driving task, and an automated drive, in which the vehicle was controlled by an automated driving system. During both drives, three perturbing events occurred at early, intermediate, and late phases in the drives: in the automated drive, a failure in automation caused the vehicle to drift toward the edge of the road; in the manual drive, wind gusts resulted in the vehicle drifting in the same direction and magnitude as the “drifts” in the automated drive. Following automation failure, drivers were forced to control the vehicle manually until the system became operational again. Drivers’ lateral control of the vehicle was assessed during three phases of manual control in both drives. The results indicate that performance recovery was better when drivers had full manual control of the vehicle throughout the drive, rather than when drivers were forced to drive manually following automation failure. Drivers also experienced increased tiredness, and physical and perceptual fatigue symptoms following both drives. The findings have important implications for the design of intelligent transportation systems. Systems that reduce the driver’s perceptions of task demands of driving are likely to undermobilize effort in fatigued drivers. Thus, the results strongly support the contention that human-centered transportation strategies, in which the driver is involved in the driving task, are superior to total automation.
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Pearle, Andrew D., Daniel J. Solomon, Tony Wanich, Alexandre Moreau-Gaudry, Carinne C. Granchi, Thomas L. Wickiewicz i Russell F. Warren. "Reliability of Navigated Knee Stability Examination". American Journal of Sports Medicine 35, nr 8 (sierpień 2007): 1315–20. http://dx.doi.org/10.1177/0363546507300821.
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Background Clinical examination remains empirical and may be confusing in the setting of rotatory knee instabilities. Computerized navigation systems provide the ability to visualize and quantify coupled knee motions during knee stability examination. Hypothesis An image-free navigation system can reliably register and collect multiplanar knee kinematics during knee stability examination. Study Design Controlled laboratory study. Methods Coupled knee motions were determined by a robotic/UFS testing system and by an image-free navigation system in 6 cadaveric knees that were subjected to (1) isolated varus stress and (2) combined varus and external rotation force at 0°, 30°, and 60°. This protocol was performed in intact knees and after complete sectioning of the posterolateral corner (lateral collateral ligament, popliteus tendon, and popliteofibular ligament). The correlation between data from the surgical navigation system and the robotic positional sensor was assessed using the intraclass correlation coefficient. The 3-dimensional motion paths of the intact and sectioned knees were assessed qualitatively using the navigation display system. Results Intraclass correlation coefficients between the robotic sensor and the navigation system for varus and external rotation at 0°, 30°, and 60° were all statistically significant at P < .01. The overall intraclass correlation coefficient for all tests was 0.9976 (P < .0001). Real-time visualization of the coupled motions was possible with the navigation system. Post hoc analysis of the knee motion paths during loading distinguished distinct rotatory patterns. Conclusion Surgical navigation is a precise intraoperative tool to quantify knee stability examination and may help delineate pathologic multiplanar or coupled knee motions, particularly in the setting of complex rotatory instability patterns. Repeatability of load application during clinical stability testing remains problematic. Clinical Relevance Surgical navigation may refine the diagnostic evaluation of knee instability.
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Fukuzawa, Kenji, Satoshi Hamaoka, Mitsuhiro Shikida, Shintaro Itoh i Hedong Zhang. "Lateral-deflection-controlled friction force microscopy". Journal of Applied Physics 116, nr 8 (28.08.2014): 084311. http://dx.doi.org/10.1063/1.4894250.
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Bedingham, W., i W. G. Tatton. "Kinematic representation of imposed forearm movements by pericruciate neurons (areas 4 and 3a) in the awake cat". Journal of Neurophysiology 53, nr 4 (1.04.1985): 886–909. http://dx.doi.org/10.1152/jn.1985.53.4.886.
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In eight awake cats, elbow flexion movements were imposed by a computer-controlled torque motor using three different classes of angular displacement inputs: force step-load displacements; sinusoidal displacements; and constant-velocity ramp displacements. Microelectrode recordings were obtained from 309 pericruciate neurons in areas 4 and 3a. Average response histograms for single-unit activity coupled with computer simulation of the imposed movements have shown in a neuronal population (n = 81), selected for receptive fields that were directly related to elbow movements, that both the magnitude and temporal features of the responses can be characterized by the coefficients of a third-order differential equation describing the movement's angular kinematics (i.e., position, velocity, acceleration, and jerk). To compare the responses of different neurons the coefficients were normalized to the angular velocity coefficient, which was assigned a weighted value of 1.0. The neurons' average responses were "predictable" by the normalized coefficients regardless of the imposed movements' temporal characteristics. Two distinct and spatially separate pericruciate areas containing neurons that responded to the imposed forearm movements were located: 1) one within area 4 at the lateral extent of the cruciate sulcus, which contained neurons that responded with predominant jerk and acceleration coefficients, exhibited either cutaneous or deep receptive fields, and demonstrated low microstimulation current thresholds to activate forelimb muscles; 2) a second, more laterally located area near the 3a/4 border in the postsygmoid gyrus, which contained neurons that responded with predominant velocity coefficients, and comparatively small jerk acceleration, and position coefficients, exhibited either cutaneous or deep receptive fields, and demonstrated high microstimulation thresholds (greater than 20 microA). Due to the sensitivity of the higher derivatives to changes in motion, the relative magnitude and time course of the average firing probability of area 4 neurons with prominent acceleration and jerk coefficients were dominated by these kinematic features during the more rapidly imposed movements. The findings are in accord with a hypothesis proposing that motor cortical neurons in area 4 form a sufficient substrate for a "predictive" feedback organization, and may constitute an essential component of a system capable of regulating errors in angular joint movements despite the relatively long conduction delays and the slow time course of muscle tension production inherent to mammalian neuromuscular systems.
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Moghimi, Negar, Sabrina Jedlicka i Svetlana Tatic-Lucic. "Micro-Electro-Mechanical System for Measuring Mechanical Properties of Cell Aggregates". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2015, DPC (1.01.2015): 001701–20. http://dx.doi.org/10.4071/2015dpc-wp36.
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This paper presents design and finite element analysis (FEA) modeling of a novel micro-electro-mechanical system for determining mechanical properties of cell aggregates. The main components of this system are the electrostatic actuator array for applying force onto the cell aggregate and piezoresistive sensor for measuring it. A novel actuator array that allows for a set of five predefined displacements up to 100 μm was designed and modeled. FEA modeling of the components was performed to optimize the design and performance. While the device described is specifically designed for on-chip mechanical characterization of cell aggregates in vitro, it could also be translated to other applications. Application of MEMS in biomedical devices has expanded vastly over the last few decades. MEMS devices have been developed to measure different characteristics of cells. The study of cell biomechanics is of growing importance in biology and medical science, as mechanical properties of cells can be related to the cause, progress and cure of certain diseases [1]. The key motivation is to develop systems for controlled mechanical stimulation and characterization of cells. Previously we have developed BioMEM device for measuring mechanical characteristics of single cells [2]. Our new study is focused on a novel method to measure biomechanical properties of cell aggregates, which are commonly used in stem cell culture. The biomechanical measurement of cell aggregates could elucidate how cellular aggregates change with age, differentiation, and other cellular processes or states [3, 4]; which could further inform decisions regarding future use of the cells of interest. The actuation in this work is done by comb drive actuators [5] because of a relatively large displacement and independency of the electrostatic force from displacement. The springs need to be properly designed to achieve the maximum range of stable displacement. Folded flexure spring design combined with initially bent beams was used in our design because of great compliance in lateral direction, larger linear deflection range, lower side instability and minimal area usage [6, 7]. Coupled electromechanical modeling was performed to verify the actuator design. The actuator array consists of a central shuttle and five pairs of comb drives each provide different displacements ranging from 52 μm to 100 μm which correspond to 5 % to 25 % deformation of the targeted cell aggregate. Custom-designed springs that will support the central actuator shuttle and allow for the large displacements were designed and the ratio of shuttle stiffness in perpendicular direction to actuation direction was maximized in order to increase the stable range of shuttle forward movement. FEA of sensor part was also done to maximize the sensor sensitivity by modeling different designs with varied design parameters. This paper presents design of a novel MEMS actuator and sensor system. FEA modeling and optimization of device components was performed and the device is currently being fabricated.
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Su, Ho-Jeen, i Ali H. Dogru. "Modeling of Equalizer Production System and Smart-Well Applications in Full-Field Studies". SPE Reservoir Evaluation & Engineering 12, nr 02 (14.04.2009): 318–28. http://dx.doi.org/10.2118/111288-pa.
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Summary Equalizer production systems and inflow control devices are used to mitigate water or gas-coning problems for mature fields. We have developed new modeling methods to simulate equalizer and interval control valve (ICV) performance in full-field multimillion-cell reservoir models under a parallel computational environment. The authors present single-well performance predictions with and without an equalizer, and the results are significantly different in some cases. Full-field modeling with equalizers and ICV controls for several examples has been conducted. In such cases, many individual wells would have significantly improved performance. At full-field level, however, using equalizers or smart well applications without total field optimization would not improve performance much, for reasons discussed in this paper. The frictional pressure loss across an equalizer can be considered as a skin, and we have developed an analytical well equation to include it. With this theoretical development, it is now possible to confirm or monitor equalizer performance in terms of pressure drop from pressure transient analysis. Introduction With high oil prices prevailing, producers are more willing than ever to buy advanced wellbore equipment to improve well performance (Salamy et al. 2006; Lorentz et al. 2006; Williamson et al. 2000). Fig. 1 illustrates an equalizer production system, sometimes called an inflow control device (ICD). At sandface, fluids are forced to go through some kind of flow-restriction mechanism before entering the production tubing. Flow restriction is achieved by different means, such as spiral channels and narrow-gauge orifice to artificially generate extra frictional pressure drop at chosen downhole locations where early water or gas breakthrough may occur. Current equalizer production systems are built into the tubing or casing and cannot be adjusted or moved once installed. Because the exact well-completion interval (where early water or gas breakthrough occurs) cannot be predicted, most manufacturers recommend a uniform design (e.g., an equalizer device every 40 or 80 feet [ft]). The manufacturers claim a uniform design has a self-regulating function; whereby, high-producing zones are cut back automatically to allow a higher influx from low-producing zones. The self-regulating property comes from the rate-dependent skin characteristics of the ICD. The flow resistence provided by constrictions is exponentially proportional to the flow rate. However, the authors illustrate that equalizer placement can be optimized to have a more uniform production profile if the reservoir permeability along the wellbore can be quantified by means of an openhole flowmeter survey shortly after drilling. Gamma ray log, drillstem testing (DST) tests, and modular formation dynamics tester (MDT) tests also provide useful permeability data. In general, equalizer application can result in a more uniform production profile, with better reservoir drainage for a very long horizontal well penetrating multiple isolated compartments. Some field trials have shown that equalizer application can improve the well productivity index (PI). A twofold oil production rate increase had been reported (Al-Qudaihy et al. 2006). In theory, this observation does not reflect reality, because an equalizer introduces extra pressure losses, causing the total pressure drawdown for a given rate to be greater than before. The only reasonable explanation for improved PI is a formation damage cleaning effect (i.e., equalizer application promotes flow from low-production [damaged] zones) thus helping remove debris from drilling mud and completion fluids. A typical smart-well application for multilateral wells is to control lateral flow rates by a downhole choke (Fig. 2). If water cut or gas/oil ratio (GOR) values exceed a preset value in any lateral, then the downhole choke is controlled remotely to cut down production in the affected lateral. For horizontal wells, we can group completion intervals into different sections. As in lateral control, the section ICV reduces production if a given section registers a high water cut or GOR value. If the well performance does not improve after several rate-reduction actions, the operator may shut down production completely for a given lateral or section if the economical limit, such as 95% water cut, is reached.