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Journal articles on the topic 'Asymmetric braking'
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1
Chen, Xiaolei, Zhiyong Dai, Hui Lin, Yanan Qiu, and Xiaogeng Liang. "Asymmetric Barrier Lyapunov Function-Based Wheel Slip Control for Antilock Braking System." International Journal of Aerospace Engineering 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/917807.
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As an important device of the aircraft landing system, the antilock braking system (ABS) has a function to avoid aircraft wheels self-locking. To deal with the strong nonlinear characteristics, complex nonlinear control schemes are applied in ABS. However, none of existing control schemes focus on the braking operating status, which directly reflects wheels self-locking degree. In this paper, the braking operating status region is divided into three regions: the healthy region, the light slip region, and the deep slip region. An ABLF-based wheel slip controller is proposed for ABS to constrain the braking system operating status in the healthy region and the light slip region. Therefore the ABS will be prevented from operating in the deep slip region. Under the proposed control scheme, self-locking is avoided completely and zero steady state error tracking of the wheel optimal slip ratio is implemented. The Hardware-In-Loop (HIL) experiments have validated the effectiveness of the proposed controller.
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He, Youguo, Chuandao Lu, Jie Shen, and Chaochun Yuan. "Design and Analysis of Output Feedback Constraint Control for Antilock Braking System with Time-Varying Slip Ratio." Mathematical Problems in Engineering 2019 (January 3, 2019): 1–11. http://dx.doi.org/10.1155/2019/8193134.
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This paper is concerned with the problem of constraint control for an Antilock Braking System (ABS) with time-varying asymmetric slip ratio constraints. A quarter vehicle braking model with system uncertainties and a Burckhardt’s tire model are considered. The Time-varying Asymmetric Barrier Lyapunov Function (TABLF) is embedded into the controllers for handling the time-varying asymmetric slip ratio constraint problems. Two adaptive nonlinear control methods (TABLF1 and TABLF2) based on TABLF are proposed not only to track the optimal slip ratio but also to guarantee no violation on the slip ratio constraints. Simulation results show that the proposed controllers can guarantee no violation on slip ratio constraints and avoid self-locking. In the meantime, TABLF1 controller can achieve a faster convergence rate, shorter stopping time, and shorter distance, compared to TABLF2 controller with the same control parameters.
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Dementyev, Y. V., A. V. Krutashov, and O. I. Deev. "Efficiency of a hybrid power plant at emergency braking." Izvestiya MGTU MAMI 9, no. 1-1 (January 10, 2015): 39–43. http://dx.doi.org/10.17816/2074-0530-67203.
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Zhulay, Vladimir, Yuriy Ustinov, Vitaliy Tyunin, and Aleksey Shchienkо. "Operation of a traction machine’s wheel mover with a locked asymmetrical balance bar." MATEC Web of Conferences 341 (2021): 00011. http://dx.doi.org/10.1051/matecconf/202134100011.
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The problems of determining the parameters of a traction machine’s wheel mover with a locked asymmetrical balance bar operation, taking into account the kinematic mismatch arising from the redistribution of the vertical reactions at the driving wheels due to off-center pushing force, have been considered. An algorithm for calculating traction and braking forces, as well as drive wheels’ slippage and skid of an asymmetric balance bar based on their traction balance and the condition of equal actual speeds under a variable vertical load, have been presented. As a result of research it has been found that the greatest additional loads in the drive and tire wear of the wheel mover with a locked asymmetric balance bar will occur when it moves in transport mode on a support surface with high traction properties.
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He, Youguo, Chuandao Lu, Jie Shen, and Chaochun Yuan. "Design and analysis of output feedback constraint control for antilock braking system based on Burckhardt’s model." Assembly Automation 39, no. 4 (September 2, 2019): 497–513. http://dx.doi.org/10.1108/aa-08-2018-0119.
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Purpose The purpose of this study is to improve vehicles’ brake stability, the problem of constraint control for an antilock braking system (ABS) with asymmetric slip ratio constraints is concerned. A nonlinear control method based on barrier Lyapunov function (BLF) is proposed not only to track the optimal slip ratio but also to guarantee no violation on slip ratio constraints. Design/methodology/approach A quarter vehicle braking model and Burckhardt’s tire model are considered. The asymmetric BLF is introduced into the controller for solving asymmetric slip ratio constraint problems. Findings The proposed controller can implement ABS zero steady-state error tracking of the optimal wheel slip ratio and make slip ratio constraints flexible for various runway surfaces and runway transitions. Simulation and experimental results show that the control scheme can guarantee no violation on slip ratio constraints and avoid self-locking. Originality/value The slip rate equation with uncertainties is established, and BLF is introduced into the design process of the constrained controller to realize the slip rate constrained control.
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Steczek, Marcin, Piotr Chudzik, and Adam Szeląg. "Application of a Non-carrier-Based Modulation for Current Harmonics Spectrum Control during Regenerative Braking of the Electric Vehicle." Energies 13, no. 24 (December 18, 2020): 6686. http://dx.doi.org/10.3390/en13246686.
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The regenerative braking of railway vehicles is widely used in DC railway systems all over the world. This mode of operation provides an opportunity to reuse part of the energy consumed by vehicles, and makes the railway system more energy efficient. During regenerative braking, not only energy management is an issue, but also Electromagnetic Compatibility EMC issues, such as interference of generated current harmonics with a railway signaling system. In this paper, the selective harmonic elimination modulation technique (SHE-PWM) was introduced to the traction drive with a three-level inverter to reduce specific catenary current harmonics generated during regenerative braking. The simulation model of a traction drive appropriate for harmonics analysis was proposed and verified by the measurements in the low-power laboratory drive system. The model was re-scaled to the 3 kV DC system for further study. The model of an induction motor with electromotive force and the method of its calculation was proposed. Furthermore, an analysis of the braking chopper operation was carried out. The asymmetric control of braking chopper was proposed to reduce the current harmonics below limits during chopper operation.
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Partono, Fuad Indra Kusuma, Sumarli, and Hasan Ismail. "Differences in braking time in symmetric and asymmetric tire tread pattern type." IOP Conference Series: Materials Science and Engineering 1034, no. 1 (February 1, 2021): 012117. http://dx.doi.org/10.1088/1757-899x/1034/1/012117.
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Zhou, Xu-Zhi, Vassilis Angelopoulos, Jiang Liu, Andrei Runov, and Dong-Xiao Pan. "Asymmetric braking and dawnward deflection of dipolarization fronts: Effects of ion reflection." Geophysical Research Letters 41, no. 20 (October 20, 2014): 6994–7001. http://dx.doi.org/10.1002/2014gl061794.
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Rödönyi, G., and J. Bokor. "Identification of LPV vehicle models for steering control involving asymmetric front wheel braking." IFAC Proceedings Volumes 37, no. 13 (September 2004): 519–24. http://dx.doi.org/10.1016/s1474-6670(17)31276-4.
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Tahouni, Amin, Mehdi Mirzaei, and Behrouz Najjari. "Applied nonlinear control of vehicle stability with control and state constraints." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, no. 1 (May 17, 2019): 191–211. http://dx.doi.org/10.1177/0954407019848858.
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For the vehicle dynamic control system, to guarantee directional stability in risky maneuvers, the side-slip angle should be restricted to the admissible range when the yaw rate tracks the proposed desired response for enhanced steerability. Meanwhile, the control input of the external yaw moment produced by asymmetric braking forces should be calculated in the practical range according to the capacity of tire forces. In the present study, a novel constrained controller with input and state constraints is developed. To this aim, a cost function consisting of predicted continuous response of yaw rate tracking error is expanded in terms of current control signal. Concurrently, the state constraint of side slip is transformed to the equivalent constraint of control signal by a novel nonlinear prediction approach. After that, the expanded performance index is analytically minimized in the presence of all input constraints to obtain the control law. The computed yaw moment is optimally distributed to asymmetric braking forces by designing a wheel slip control system. Simulation studies are conducted to evaluate the performance of proposed constrained controller compared with the unconstrained controller and a conventional nonlinear model predictive controller developed in the recent papers using a 14-degree-of-freedom vehicle model which includes suspension system dynamics. The results show that the proposed controller is much faster and easy to solve and implement.
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Yan, Shi Rong, and Shi Zhong Li. "Study on an EV Traction Control Strategy." Applied Mechanics and Materials 141 (November 2011): 605–10. http://dx.doi.org/10.4028/www.scientific.net/amm.141.605.
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According to an electrical vehicle (EV) construction and working principle, a dynamic model governing its motion was established. A built-in permanent magnet synchronous motor was selected as its driving motor and a mathematical model about the motor working principle was described also. To get good motion effect, a motor driving control system with a current loop and a speed loop was developed. The current loop consists of maximum torque per ampere control and field weakening control. The speed loop is based on a sliding mode control. To make the EV working more smooth, stable and safer, its traction control includes driving motor control and wheel braking control. During some acceleration or cornering, wheel braking control is introduced to keep driving wheels in good slip states, especially to make the car in a good stable and safe state. Simulation study based on MATLAB/Simulink showed the control strategy developed here can make the EV work well, even when it runs on some asymmetric road.
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Scholtz, Pieter Antonie, and Michael Njoroge Gitau. "Asymmetric Neutral Point Diode Clamped Topology with Reduced Component Count for Switched Reluctance Machine Drive." Energies 15, no. 7 (March 27, 2022): 2468. http://dx.doi.org/10.3390/en15072468.
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The Reduced Asymmetric Neutral Point Clamped converter topology for unipolar driven, multiphase switched reluctance machines is proposed in this paper. This topology shares similarities with the conventional NPC and Asymmetric-NPC topologies, however it is unique in that the components for the capacitor string and outer semiconductor switches are shared among all the phases for a reduced component count. Some switching state combinations are not possible during commutation overlap between motor phases, resulting in minor torque transients during regenerative braking. A custom modulation scheme is implemented with fixed frequency, phase-shifted carrier waveforms that allow for automatic balancing of the neutral point voltage and interleaved switching of the semiconductor switches. A simple torque observer control architecture is used with minor adjustments for arbitrating torque contribution priorities between phases during handover.
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Chen, Xiuqi, Wei Wei, Hongbin Mu, Xu Liu, Zhuo Wang, and Qingdong Yan. "Numerical Investigation and Experimental Verification of the Fluid Cooling Process of Typical Stator–Rotor Machinery with a Plate-Type Heat Exchanger." Machines 10, no. 10 (October 2, 2022): 887. http://dx.doi.org/10.3390/machines10100887.
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This paper discusses the heat transfer process for a typical stator–rotor machinery-hydrodynamic retarder from the perspective of computational fluid dynamics and experimental means. Fluid cooling is an essential step in the working process of hydrodynamic retarders, and changes in viscosity along with temperature rise will affect the performance of braking. To investigate the heat transfer process of stator–rotor machinery, a novel computational fluid dynamics (CFD) method, combined with a dynamic thermophysical property transfer algorithm, is proposed. A heat-flow coupling numerical method with experimental verification is proposed, in which the density and the viscosity are variable with the temperature in an effectiveness–number of transfer units (P-NTU) method. The results show that the numerical results are in good agreement with the experimental data, with a 0.1–2.5% error. The influence of an asymmetric structure on heat transfer characteristics is discussed. The results show that the optimal braking performance, along with the liquid cooling performance, is achieved under outlets with an inlet passage set as 90 degrees.
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Soh, H. J., and J.-H. Yoo. "Optimal shape design of a brake calliper for squeal noise reduction considering system instability." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 224, no. 7 (May 14, 2010): 909–25. http://dx.doi.org/10.1243/09544070jauto1385.
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Squeal is a noise phenomenon occurring in the last stage of automobile braking with a high-frequency sound. It is very difficult to express the phenomenon using a mathematical model, since the origin of squeal noise is physically complex. However, the possibility of squeal generation can be predicted by solving the vibration equation of the self-excited system using the complex eigenvalue analysis method. The results of the method are expressed as the magnitude of the unstable mode, and the generation of squeal noise can be prevented by reducing the magnitude of the unstable mode of the brake system. The objective of this research is to determine the optimal design process focused on the calliper housing shape to suppress squeal noise generation by reducing the system instability. The objective function is set to minimize the real part of the complex eigenvalue, i.e. the instability index. In the optimization design process, the design variable for topology optimization is established by focusing on the finger part of the calliper housing, which transmits the braking pressure to the pad lining. To supplement the complex shape generated by the topology optimization process, parametric design variables are selected for the subsequent process. Parameters are set to adjust the housing finger stiffness and are defined by considering the topology optimization result. Finally, the asymmetric shape of the calliper housing is obtained to reduce squeal noise generation.
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Hwang, Kyu Yun, Baik Kee Song, and Byung Il Kwon. "Asymmetric dual winding three‐phase PMSM for fault tolerance of overheat in electric braking system of autonomous vehicle." IET Electric Power Applications 13, no. 12 (October 7, 2019): 1891–98. http://dx.doi.org/10.1049/iet-epa.2018.5973.
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Le Gigan, Gaël, Magnus Ekh, Tore Vernersson, and Roger Lundén. "Modelling of grey cast iron for application to brake discs for heavy vehicles." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 231, no. 1 (August 5, 2016): 35–49. http://dx.doi.org/10.1177/0954407016632090.
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Cast iron brake discs are commonly used in the automotive industry, and efforts are being made to gain a better understanding of the thermal and mechanical phenomena occurring at braking. The high thermomechanical loading at braking arises from interaction between the brake disc and the brake pads. Frictional heating generates elevated temperatures with a non-uniform spatial distribution often in the form of banding or hot spotting. These phenomena contribute to material fatigue and wear and possibly also to cracking. The use of advanced calibrated material models is one important step towards a reliable analysis of the mechanical behaviour and the life of brake discs. In the present study, a material model of the Gurson–Tvergaard–Needleman type is adopted, which accounts for asymmetric yielding in tension and compression, kinematic hardening effects, viscoplastic response and temperature dependence. The material model is calibrated using specimens tested in uniaxial cyclic loading for six different temperatures ranging from room temperature to 650 °C. A special testing protocol is followed which is intended to activate the different features of the material model. Validation of the model is performed by using tensile tests and thermomechanical experiments. An application example is given where a 10° sector of a brake disc is analysed using the commercial finitie element code Abaqus under a uniformly applied heat flux on the two friction surfaces. The results indicate that the friction surface of the hat side and the neck can be critical areas with respect to fatigue for the uniform heating studied.
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Schaefer, Bradley E. "Sudden and steady orbital period changes across the classical nova eruptions of DQ Her and BT Mon." Monthly Notices of the Royal Astronomical Society 492, no. 3 (January 24, 2020): 3323–42. http://dx.doi.org/10.1093/mnras/stz3325.
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ABSTRACT I report two new measures of the sudden change in the orbital period (P) across the nova eruption (ΔP) and the steady period change in quiescence ($\dot{P}$) for classical novae (CNe) DQ Her and BT Mon. The fractional changes (ΔP/P) in parts per million (ppm) are −4.46 ± 0.03 for DQ Her and +39.6 ± 0.5 for BT Mon. For BT Mon, the ΔP/P value is not large enough (i.e. >1580 ppm) to allow for hibernation in this system. The negative ΔP/P for DQ Her is a confident counterexample of the hibernation model for the evolution of cataclysmic variables. Further, published models of period changes by nova eruptions do not allow for such a negative value, so some additional mechanism is required, with this perhaps being due to asymmetric ejection of material. My program has also measured the first long-term $\dot{P}$ for CNe, with 0.00 ± 0.02 for DQ Her and −2.3 ± 0.1 for BT Mon, all with units of 10−11 d cycle−1. These can be directly compared to the predictions of the magnetic braking model, where the long-term average $\dot{P}$ is a single universal function of P. The predicted values are −0.027 for DQ Her and −0.33 for BT Mon. For both novae, the measured $\dot{P}$ is significantly far from the predictions for magnetic braking. Further, the observed ΔP for BT Mon imposes an additional positive period change of +0.60 × 10−11 d cycle−1 when averaged over the eruption cycle, so this system actually has a long-term rise in P.
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Tak, Sehyun, Sunghoon Kim, Donghoun Lee, and Hwasoo Yeo. "A Comparison Analysis of Surrogate Safety Measures with Car-Following Perspectives for Advanced Driver Assistance System." Journal of Advanced Transportation 2018 (November 1, 2018): 1–14. http://dx.doi.org/10.1155/2018/8040815.
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Surrogate Safety Measure (SSM) is one of the most widely used methods for identifying future threats, such as rear-end collision. Various SSMs have been proposed for the application of Advanced Driver Assistance Systems (ADAS), including Forward Collision Warning System (FCWS) and Emergency Braking System (EBS). The existing SSMs have been mainly used for assessing criticality of a certain traffic situation or detecting critical actions, such as severe braking maneuvers and jerking before an accident. The ADAS shows different warning signals or movements from drivers’ driving behaviours depending on the SSM employed in the system, which may lead to low reliability and low satisfaction. In order to explore the characteristics of existing SSMs in terms of human driving behaviours, this study analyzes collision risks estimated by three different SSMs, including Time-To-Collision (TTC), Stopping Headway Distance (SHD), and Deceleration-based Surrogate Safety Measure (DSSM), based on two different car-following theories, such as action point model and asymmetric driving behaviour model. The results show that the estimated collision risks of the TTC and SHD only partially match the pattern of human driving behaviour. Furthermore, the TTC and SHD overestimate the collision risk in deceleration process, particularly when the subject vehicle is faster than its preceding vehicle. On the other hand, the DSSM shows well-matched results to the pattern of the human driving behaviour. It well represents the collision risk even when the preceding vehicle moves faster than the follower one. Moreover, unlike other SSMs, the DSSM shows a balanced performance to estimate the collision risk in both deceleration and acceleration phase. These research findings suggest that the DSSM has a great potential to enhance the driver’s compliance to the ADAS, since it can reflect how the driver perceives the collision risks according to the driving behaviours in the car-following situation.
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Yang, Yuangui, Huiyu Yuan, Shuang Wang, and Haifeng Dai. "Magnetic Activity on Four Short-period Contact Binaries: V0576 Peg, KW Psc, V0873 Per, and FY Boo." Astronomical Journal 163, no. 6 (May 5, 2022): 250. http://dx.doi.org/10.3847/1538-3881/ac63c0.
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Abstract We presented new photometry for four short-period late-type binaries, observed by three small telescopes in China from 2020 September to 2021 December. Seven sets of light curves (including the TESS data for FY Boo) were analyzed by using the W-D method. Three binaries (V0576 Peg, V0873 Per, and FY Boo) are W-type binaries with q ≃ 2.5, while KW Psc is an A-type binary with q ≃ 0.43. Max.I−Max.II is up to 10% of variable light amplitude for the asymmetric light curves, which are modeled by a dark spot on the surface of the more massive component. Photometric results imply the existence of movement and evolution of the cool spot. From the temperature−luminosity and mass–luminosity diagrams, the more massive components are a bit evolved main-sequence stars, while the less massive ones are oversized and overluminous owing to energy exchange. Orbital period analyses indicate that the cyclic oscillations occur in the (O − C) curves. Their modulated periods approach 11 yr, which may preferably result from the magnetic activity cycle for four late-type contact binaries. With angular momentum loss through magnetic braking, these short-period contact binaries may evolve into deep-contact configurations.
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Heishman, Aaron, Bryce Daub, Ryan Miller, Brady Brown, Eduardo Freitas, and Michael Bemben. "Countermovement Jump Inter-Limb Asymmetries in Collegiate Basketball Players." Sports 7, no. 5 (April 30, 2019): 103. http://dx.doi.org/10.3390/sports7050103.
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The purpose of the present study was to establish the intrasession and intersession reliability of variables obtained from a force plate that was used to quantitate lower extremity inter-limb asymmetry during the bilateral countermovement jump (CMJ). Secondarily, a comparison was performed to determine the influence of the jump protocol CMJ with or without an arm swing (CMJ AS and CMJ NAS, respectively) on inter-limb asymmetries. Twenty-two collegiate basketball players performed three CMJ AS and three CMJ NAS on dual force platforms during two separate testing sessions. A majority of variables met the acceptable criterion of intersession and intrasession relative reliability (ICC > 0.700), while fewer than half met standards established for absolute reliability (CV < 10%). CMJ protocol appeared to influence asymmetries; Concentric Impulse-100 ms, Eccentric Braking Rate of Force Development, Eccentric Deceleration, and Force at Zero velocity were significantly different between jumping conditions (CMJAS versus CMJ NAS; p < 0.05). The present data establish the reliability and smallest worthwhile change of inter-limb asymmetries during the CMJ, while also identifying the influence of CMJ protocol on inter-limb asymmetries, which can be useful to practitioners and clinicians in order to effectively monitor changes associated with performance, injury risk, and return-to-play strategies.
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Gou, Hongye, Yannian He, Wen Zhou, Yi Bao, and Genda Chen. "Experimental and numerical investigations of the dynamic responses of an asymmetrical arch railway bridge." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 232, no. 9 (April 11, 2018): 2309–23. http://dx.doi.org/10.1177/0954409718766929.
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The dynamic responses of an asymmetrical arch railway bridge subjected to moving trains are experimentally and numerically investigated in this study. The strains, displacements and accelerations at critical sections of the bridge were measured at different speeds of trains. A three-dimensional finite element model of the bridge–vehicle coupling system was established to understand the measured dynamic responses and was validated against the experimental results. The numerical model was used to analyze the influence of asymmetry on the dynamic responses of the bridge and the safety and ride comfort of trains. The results indicate that the dynamic responses of the bridge increase with the train speed. Braking of the train has the largest impact on the vertical dynamic displacement of the bridge. The maximum dynamic strain is in the arch rib. The longer half arch demonstrated much larger counterforce and dynamic responses than those of the shorter half arch, while the symmetrical structures tend to exhibit good symmetry. The asymmetrical arrangement of the bridge reduces the structural stiffness.
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Furtlehner, Cyril, Jean-Marc Lasgouttes, and Maxim Samsonov. "One-Dimensional Particle Processes with Acceleration/Braking Asymmetry." Journal of Statistical Physics 147, no. 6 (June 19, 2012): 1113–44. http://dx.doi.org/10.1007/s10955-012-0521-y.
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Potdevin, François, Christophe Gillet, Franck Barbier, Yann Coello, and Pierre Moretto. "Propulsion and Braking in the Study of Asymmetry in Able-Bodied Men's Gaits." Perceptual and Motor Skills 107, no. 3 (December 2008): 849–61. http://dx.doi.org/10.2466/pms.107.3.849-861.
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POTDEVIN, FRANCOIS. "PROPULSION AND BRAKING IN THE STUDY OF ASYMMETRY IN ABLE-BODIED MEN'S GAITS." Perceptual and Motor Skills 107, no. 7 (2008): 849. http://dx.doi.org/10.2466/pms.107.7.849-861.
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Scherbakova, O. V. "Substantiation of the design scheme of forces acting on the truck train at braking and factors causing the braking forces asymmetry along the sides of the truck train." Вестник гражданских инженеров 15, no. 6 (2018): 208–13. http://dx.doi.org/10.23968/1999-5571-2018-15-6-208-213.
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Diederich, Alexander, Christophe Bastien, Karthikeyan Ekambaram, and Alexis Wilson. "Occupant pre-crash kinematics in rotated seat arrangements." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 235, no. 10-11 (March 25, 2021): 2818–42. http://dx.doi.org/10.1177/09544070211004504.
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The introduction of automated L5 driving technologies will revolutionise the design of vehicle interiors and seating configurations, improving occupant comfort and experience. It is foreseen that pre-crash emergency braking and swerving manoeuvres will affect occupant posture, which could lead to an interaction with a deploying airbag. This research addresses the urgent safety need of defining the occupant’s kinematics envelope during that pre-crash phase, considering rotated seat arrangements and different seatbelt configurations. The research used two different sets of volunteer tests experiencing L5 vehicle manoeuvres, based in the first instance on 22 50th percentile fit males wearing a lap-belt (OM4IS), while the other dataset is based on 87 volunteers with a BMI range of 19 to 67 kg/m2 wearing a 3-point belt (UMTRI). Unique biomechanics kinematics corridors were then defined, as a function of belt configuration and vehicle manoeuvre, to calibrate an Active Human Model (AHM) using a multi-objective optimisation coupled with a Correlation and Analysis (CORA) rating. The research improved the AHM omnidirectional kinematics response over current state of the art in a generic lap-belted environment. The AHM was then tested in a rotated seating arrangement under extreme braking, highlighting that maximum lateral and frontal motions are comparable, independent of the belt system, while the asymmetry of the 3-point belt increased the occupant’s motion towards the seatbelt buckle. It was observed that the frontal occupant kinematics decrease by 200 mm compared to a lap-belted configuration. This improved omnidirectional AHM is the first step towards designing safer future L5 vehicle interiors.
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Maknickas, Algirdas, Oleg Ardatov, Marijonas Bogdevičius, and Rimantas Kačianauskas. "Modelling the Interaction between a Laterally Deflected Car Tyre and a Road Surface." Applied Sciences 12, no. 22 (November 8, 2022): 11332. http://dx.doi.org/10.3390/app122211332.
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The interaction between a deflected car tyre and a road surface was modelled under normal and overloaded conditions. The model incorporates the detailed geometry of the car wheel, including a metallic rim reinforcement, a hyper-elastic composite tyre and tyre treads, as well as the geometry of the road surface. The finite element method was used to investigate the nonlinear dynamics of the model and study the influence of tyre deflection on the friction coefficient of the tyre tread. The results were compared under different internal tyre pressures and external wheel loads, including underloaded, normal and overloaded states. The skewness of the distribution of friction coefficients was calculated under these different conditions. The results show that overloading and nonoptimal internal tyre pressure cause reduced and skewed friction, with the asymmetry in the tyre–road contact zone resulting in a moving instability of the car during braking.
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Sun, Jing, and Xin Wang. "Design and Research of Switched Reluctance Motor Converter Used in Electric Vehicle." Applied Mechanics and Materials 40-41 (November 2010): 277–82. http://dx.doi.org/10.4028/www.scientific.net/amm.40-41.277.
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In recent years, there has been a growing interest in switched reluctance motor when it is widely used in the field of electric vehicles for its simple structure, low cost, high reliability, wide speed range, high response speed, high operating efficiency and strong renewable braking ability. The performance and structure of the power converter will directly affect the efficiency, cost and reliability of SRM, so the reasonable design of SRM power converter is the key to increase the cost performance of the whole SRM speed control system. Based on the principle and advantages of SRM, an improved asymmetrical half-bridge structure power converter with soft-switching is proposed for SRD in the paper. The DC / DC switching mode power supply for switched reluctance motor drive system is also successfully designed based on LT1247 integrated chip. Experiment results show that the new type of power converter and the DC / DC switching mode power supply can work better on electric vehicles.
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Dos Santos, Luciana Oliveira, Andréia Abud da Silva Costa, and Renato Moraes. "Effect of lower limb dominance on walking adaptations in young adults when stepping into a hole." Brazilian Journal of Motor Behavior 13, no. 5 (February 20, 2020): 133–43. http://dx.doi.org/10.20338/bjmb.v13i5.141.
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Background. Depending on the dimensions of a hole, the characteristics of the walking surface, and the position of the hole relative to normal walking, individuals may need to step into the hole with the dominant or non-dominant limb. Aim. We investigated the effect of the lower limb dominance in walking adaptations in the presence of a hole on the ground. Methods: Twenty young adults walked and stepped into a hole positioned in the middle of the pathway using the dominant and non-dominant lower limbs. Results. For the trailing limb, the impulses were not affected by the lower limb dominance, but for the leading limb, the non-dominant leg increased the braking and propulsive impulses compared to the dominant leg. On the other hand, toe-off velocity increased when the non-dominant leg was used as trailing and leading limbs. Stride speed increased when the non-dominant leg was the trailing limb. Interpretation. Our results were consistent with asymmetrical behavior between dominant and non-dominant legs. Although the differences between the dominant and non-dominant legs have not affected the success in the task, they can put the individual at higher risk of stumbling and consequently a fall when stepping with the non-dominant leg into the hole.
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Liu and Zhong. "Research on an Electromagnetic Interference Test Method Based on Fast Fourier Transform and Dot Frequency Scanning for New Energy Vehicles under Dynamic Conditions." Symmetry 11, no. 9 (September 1, 2019): 1092. http://dx.doi.org/10.3390/sym11091092.
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In recent years, electromagnetic interference (EMI) of new energy vehicles, including difference mode symmetric interference and common mode asymmetry interference, has attracted the attention of many scholars. So far, EMI tests for new energy vehicles under steady conditions cannot reflect the actual EMI of the running vehicle. The results of EMI test methods based on fast Fourier transform (FFT) under dynamic conditions have worse frequency resolutions, and frequency/amplitude accuracy has low precision. Therefore, this paper proposes an EMI test method based on FFT and dot frequency scanning (DFS) for new energy vehicles under dynamic conditions. The identification method for accelerating, sliding, and braking conditions is studied. A comprehensive EMI key evaluation index system for new energy vehicles is built, including characteristic points with maximum amplitude, area, ratio, and density coefficients for high-amplitude characteristic points. Among them, the maximum amplitude is an index to evaluate extreme values. The ratio of high-amplitude characteristic points is a comprehensive index to evaluate the overall region. The density coefficient is an index to evaluate the local region. Finally, this method is applied to three vehicles. With the same instruments, by reducing the FFT frequency span, the frequency resolution and frequency accuracy increase. The results indicate that the EMI of new energy vehicles can be tested under dynamic conditions with high accuracy according to the operable evaluation indexes.
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BURLAKA, Serhiy. "ALGORITHM OF FUNCTIONING OF A MACHINE-TRACTOR UNIT USING A FUEL MIXER SUPPLY SYSTEM." Herald of Khmelnytskyi National University 305, no. 1 (February 23, 2022): 136–40. http://dx.doi.org/10.31891/2307-5732-2022-305-1-136-140.
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The switching scheme of operation of the machine-tractor unit with the use of the power supply system with the fuel mixer and the electronic control unit on the basis of Arduino Uno is presented. This scheme provides a fully adaptive power supply system for biofuels and their mixtures depending on the load-speed indicators and operating modes. The selection of circuit components is carried out. A linear algorithm for writing a control program for the engine power system has been developed, which ensures its energy efficiency and efficiency of the machine-tractor unit. During the operation of the machine-tractor unit there is a constant change of thermal, loading and speed modes. Internal combustion engines during operation usually operate in unstable modes – start, warm up, acceleration, braking, increase and decrease the load, stop. There is a need to develop a method of controlling the work processes of the diesel engine for its operation on a mixture of BF and PSU with electronic control of the fuel mixture depending on the operating modes. Engines are dynamically asymmetrical objects, ie the processes that take place when increasing and decreasing the load on the crankshaft, when starting and stopping the engine, differ from each other. The development of the algorithm for controlling the working processes of the diesel engine when working on a mixture of BF and PSU with electronic control of the fuel mixture depending on the operating modes of the engine will differ. Technical parameters of the diesel engine and power supply system that must be controlled during operation: torque, crankshaft speed, power, coolant temperature, PSU temperature, percentage of fuel mixture. Fuel consumption refers to economic indicators, to environmental – the composition and amount of harmful emissions. The value of these indicators directly depends on the modes of operation.
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Verliat, Antoine, Patrick Hennebelle, Anaëlle J. Maury, and Mathilde Gaudel. "Protostellar disk formation by a nonrotating, nonaxisymmetric collapsing cloud: model and comparison with observations." Astronomy & Astrophysics 635 (March 2020): A130. http://dx.doi.org/10.1051/0004-6361/201936394.
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Context. Planet-forming disks are fundamental objects that are thought to be inherited from large scale rotation through the conservation of angular momentum during the collapse of a prestellar dense core. Aims. We investigate the possibility for a protostellar disk to be formed from a motionless dense core that contains nonaxisymmetric density fluctuations. The rotation is thus generated locally by the asymmetry of the collapse. Methods. We study the evolution of the angular momentum in a nonaxisymmetric collapse of a dense core from an analytical point of view. To test the theory, we performed three-dimensional simulations of a collapsing prestellar dense core using adaptative mesh refinement. We started from a nonaxisymmetrical situation, considering a dense core with random density perturbations that follow a turbulence spectrum. We analyzed the emerging disk by comparing the angular momentum it contains with the one expected from our analytic development. We studied the velocity gradients at different scales in the simulation as is done with observations. Results. We show that the angular momentum in the frame of a stellar object, which is not located at the center of mass of the core, is not conserved due to inertial forces. Our simulations of such nonaxisymmetrical collapse quickly produce accretion disks at the small scales in the core. The analysis of the kinematics at different scales in the simulated core reveals projected velocity gradients of amplitudes similar to the ones observed in protostellar cores and for which directions vary, sometimes even reversing when small and large scales are compared. These complex kinematics patterns appear in recent observations and could be a discriminating feature with models where rotation is inherited from large scales. Our results from simulations without initial rotation are more consistent with these recent observations than when solid-body rotation is initially imprinted. Lastly, we show that the disks that formed in this scenario of nonaxisymmetrical gravitational collapse grow to reach sizes larger than those that are observed, and then fragment. We show that including a magnetic field in these simulations reduces the size of the outcoming disks and it prevents them from fragmenting, as is shown by previous studies. Conclusions. We show that in a nonaxisymmetrical collapse, the formation of a disk can be induced by small perturbations of the initial density field in the core, even in the absence of global large-scale rotation of the core. In this scenario, large disks are generic features that are natural consequences of the hydrodynamical fluid interactions and self-gravity. Since recent observations have shown that most disks are significantly smaller and have a size of a few tens of astronomical units, our study suggests that magnetic braking is the most likely explanation. The kinematics of our model are consistent with typically observed values of velocity gradients and specific angular momentum in protostellar cores. These results open a new avenue in which our understanding of the early phases of disk formation can be explored since they suggest that a fraction of the protostellar disks could be the product of nonaxisymmetrical collapse, rather than directly resulting from the conservation of preexisting large scale angular momentum in rotating cores.
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Ji, Zhongying, Shiyu Qin, Shuanhong Ma, Xin Jia, Xiaolong Wang, and Feng Zhou. "Bio-inspired smart surface to achieve controllable locomotion through adjustable anisotropic friction." Friction, July 31, 2021. http://dx.doi.org/10.1007/s40544-021-0520-6.
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AbstractAnisotropic friction generated by microstructured surfaces is crucial for performing functions such as directional locomotion and adhesion in biological systems. Hence, an epoxy-based shape memory polymer (SMP) incorporating Fe3O4 nanoparticles is used in this study to create a smart surface with oriented structures to mimic anisotropic friction and exploit human-developed controllable locomotion systems. Applying the specific properties of the epoxy-based SMP, fast switching friction can be achieved by adjusting the topography and stiffness of the microstructures on the surface. In addition, the photothermogenesis effect of Fe3O4 nanoparticles induces changes in the asymmetric topography and stiffness on the SMP surface under the irradiation of near-infrared (NIR) light, thereby inducing a rapid switching of the friction force. Furthermore, a microbot is created to demonstrate remotely controlled locomotion, such as unidirectional and round-trip movements, and braking by switching the friction force under NIR light. These results are promising for the design of new intelligent surfaces and interfaces; additionally, they may facilitate the investigation of biological structures and processes.
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Echim, Marius, Mirela Voiculescu, Costel Munteanu, Eliza Teodorescu, Gabriel Voitcu, Cătălin Negrea, Simona Condurache-Bota, and Emilian Bujor Dănilă. "On the phenomenology of magnetosheath jets with insight from theory, modelling, numerical simulations and observations by Cluster spacecraft." Frontiers in Astronomy and Space Sciences 10 (February 17, 2023). http://dx.doi.org/10.3389/fspas.2023.1094282.
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Introduction: During recent years magnetosheath plasma structures called “jets” are identified in spacecraft data as localized regions in the magnetosheath where the dynamic pressure is enhanced compared to the background. Although the nomenclature and detection algorithms vary from author to author, magnetosheath jets are part of a larger class of phenomena which can be globally called magnetosheath irregularities. In this review we focus on elements of jets phenomenology less discussed in the literature, though sustained by theoretical models for solar wind magnetosphere interaction, numerical studies based on Vlasov equilibrium models or kinetic numerical simulations.Methods: The self-consistency of magnetosheath jets and the preservation of their physical identity (shape and physical properties), implicitly assumed in many recent experimental studies, is discussed in modelling and simulations studies and results as a consequence of kinetic processes at the edges of the jets. These studies provide evidence for the fundamental role played by a polarization electric field sustaining the forward motion of the jet with respect to the background plasma. Another natural consequence is the backward motion of surrounding magnetosheath plasma at the edges of jets. The conservation of magnetic moment of ions leads to a decrease of jets forward speed when it moves into increasing magnetic field. Our review is complemented by an analysis of magnetosheath data recorded by Cluster in 2007 and 2008. We applied an algorithm to detect jets based on searching localized enhancements of the dynamic pressure.Results: This algorithm identifies a number of 960 magnetosheath jets (354 events in 2007 versus 606 events in 2008). A statistical analysis of jet plasma properties reveals an asymmetric distribution of the number of jets as well as a dawn-dusk asymmetry of jets temperature and density. The perturbative effects of jets on the background magnetosheath density/temperature are stronger in the dusk/dawn flank. We also found evidence for deceleration and perpendicular heating of jets with decreasing distance to the Earth. The braking of jets is correlated with the variation of the magnetic field intensity: the stronger the magnetic field gradient, the more efficient is the jet breaking.
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Schaefer, Bradley E. "The recurrent nova U Scorpii from the 2010.1 to 2022.4 eruptions; the missed eruption of 2016.78 ± 0.10 and the critical complex period changes." Monthly Notices of the Royal Astronomical Society, September 9, 2022. http://dx.doi.org/10.1093/mnras/stac2511.
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Abstract U Sco is a recurrent nova with eleven observed eruptions, most recently in 2010.1 and 2022.4. I report on my program (running since 1989) of measuring eclipse times and brightnesses of U Sco in quiescence, from 2010 to 2022. The orbital period suddenly increased by +22.4 ± 1.0 parts-per-million across the 2010.1 eruption. This period change is greater than the near-zero period change (+3.9 ± 6.1 parts-per-million) across the 1999.2 eruption. This period change cannot come from any of the usual mechanisms, whereas the one remaining possibility is that the period changes are dominated by the little-known mechanism of the nova ejecting asymmetric shells. From 2010.1 to 2016.78, the O − C curve showed a steady period change that was large, with $\dot{P}$=(−21.0 ± 3.2) × 10−9. This is greatly higher than the steady period changes in the two previous inter-eruption intervals (−3.2 ± 1.9 and −1.1 ± 1.1 times 10−9). This large, variable, and negative $\dot{P}$ apparently comes from magnetic braking of the companion star’s rotation. Starting in 2016.9 ± 0.6, the O − C curve showed a strong kink that is a unique characteristic of the sudden period change (+35.4 ± 7.1 parts-per-million) across a nova event. The brightness in quiescence after 2010.4 shows that the white dwarf accreted the trigger mass for the next nova event in the year 2017.1 ± 0.6. Photometric records show the only possible time for the eruption to peak (such that its total duration of 60 days was undetectable by any observation) is during a 75 day interval inside the 2016 solar gap, thus constraining the missed eruption to 2016.78 ± 0.10.
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Brough, Lydia G., Steven A. Kautz, and Richard R. Neptune. "Muscle contributions to pre-swing biomechanical tasks influence swing leg mechanics in individuals post-stroke during walking." Journal of NeuroEngineering and Rehabilitation 19, no. 1 (June 3, 2022). http://dx.doi.org/10.1186/s12984-022-01029-z.
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Abstract Background Successful walking requires the execution of the pre-swing biomechanical tasks of body propulsion and leg swing initiation, which are often impaired post-stroke. While excess rectus femoris activity during swing is often associated with low knee flexion, previous work has suggested that deficits in propulsion and leg swing initiation may also contribute. The purpose of this study was to determine underlying causes of propulsion, leg swing initiation and knee flexion deficits in pre-swing and their link to stiff knee gait in individuals post-stroke. Methods Musculoskeletal models and forward dynamic simulations were developed for individuals post-stroke (n = 15) and healthy participants (n = 5). Linear regressions were used to evaluate the relationships between peak knee flexion, braking and propulsion symmetry, and individual muscle contributions to braking, propulsion, knee flexion in pre-swing, and leg swing initiation. Results Four out of fifteen of individuals post-stroke had higher plantarflexor contributions to propulsion and seven out of fifteen had higher vasti contributions to braking on their paretic leg relative to their nonparetic leg. Higher gastrocnemius contributions to propulsion predicted paretic propulsion symmetry (p = 0.005) while soleus contributions did not. Higher vasti contributions to braking in pre-swing predicted lower knee flexion (p = 0.022). The rectus femoris had minimal contributions to lower knee flexion acceleration in pre-swing compared to contributions from the vasti. However, for some individuals with low knee flexion, during pre-swing the rectus femoris absorbed more power and the iliopsoas contributed less power to the paretic leg. Total musculotendon work done on the paretic leg in pre-swing did not predict knee flexion during swing. Conclusions These results emphasize the multiple causes of propulsion asymmetry in individuals post-stroke, including low plantarflexor contributions to propulsion, increased vasti contributions to braking and reliance on compensatory mechanisms. The results also show that the rectus femoris is not a major contributor to knee flexion in pre-swing, but absorbs more power from the paretic leg in pre-swing in some individuals with stiff knee gait. These results highlight the need to identify individual causes of propulsion and knee flexion deficits to design more effective rehabilitation strategies.
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Kempter, Fabian, Lorena Lantella, Norman Stutzig, Jörg Fehr, and Tobias Siebert. "Role of Rotated Head Postures on Volunteer Kinematics and Muscle Activity in Braking Scenarios Performed on a Driving Simulator." Annals of Biomedical Engineering, October 12, 2022. http://dx.doi.org/10.1007/s10439-022-03087-9.
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AbstractOccupants exposed to low or moderate crash events can already suffer from whiplash-associated disorders leading to severe and long-lasting symptoms. However, the underlying injury mechanisms and the role of muscle activity are not fully clear. Potential increases in injury risk of non-nominal postures, i.e., rotated head, cannot be evaluated in detail due to the lack of experimental data. Examining changes in neck muscle activity to hold and stabilize the head in a rotated position during pre-crash scenarios might provide a deeper understanding of muscle reflex contributions and injury mechanisms. In this study, the influence of two different head postures (nominal vs. rotation of the head by about 63 ± 9° to the right) on neck muscle activity and head kinematics was investigated in simulated braking experiments inside a driving simulator. The braking scenario was implemented by visualization of the virtual scene using head-mounted displays and a combined translational-rotational platform motion. Kinematics of seventeen healthy subjects was tracked using 3D motion capturing. Surface electromyography were used to quantify muscle activity of left and right sternocleidomastoideus (SCM) and trapezius (TRP) muscles. The results show clear evidence that rotated head postures affect the static as well as the dynamic behavior of muscle activity during the virtual braking event. With head turned to the right, the contralateral left muscles yielded higher base activation and delayed muscle onset times. In contrast, right muscles had much lower activations and showed no relevant changes in muscle activation between nominal and rotated head position. The observed delayed muscle onset times and increased asymmetrical muscle activation patterns in the rotated head position are assumed to affect injury mechanisms. This could explain the prevalence of rotated head postures during a crash reported by patients suffering from WAD. The results can be used for validating the active behavior of human body models in braking simulations with nominal and rotated head postures, and to gain a deeper understanding of neck injury mechanisms.
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Sobczyk, Artur, and Marek Kasprzak. "Late Cenozoic Tectonic Activity of the Śnieżnik Massif Area (Sudetes, Sw Poland)in the Light of Lidar Dem Morphometric Analysis." Studia Geomorphologica Carpatho-Balcanica 48, no. 1 (January 1, 2014). http://dx.doi.org/10.1515/sgcb-2015-0003.
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AbstractŚnieżnik Massif represents a prominent morphological feature in the East Sudetes, which is bounded by a system of faults controlling its differential uplift. Vertical movements originated at least during the Oligocene times, with culmination phase in Pliocene times, whereas estimated total uplift was in the range of 500-1000 meters. This study presents a qualitative (geomorphometric) and quantitative (morphotectonic) approach that combines Late Cenozoic tectonic uplift model with landscape evolution theories. Application of basin asymmetry factor (AF) and hypsometric integral (Hi) analyses allowed recognizing a NW trending tilted fault blocks. They originated as a result of Palaeogene planation surface braking and differential uplift. Uplift and later fault-block tilting in the Śnieżnik Massif morphotectonic unit, were generally realized along NE-SW striking Wilkanow fault to the west and WNW-ESE striking southern fault zone, as expressed here e.g. by Potoczek-Branna, Herˇmranice and Pisary faults.
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Pan, Gongyu, and Xu Luo. "Mechanism research and structure optimization of brake noise based on contact overlap degree." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, December 27, 2022, 095440702211445. http://dx.doi.org/10.1177/09544070221144578.
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Brake noise can endanger the psychological and physiological health of passengers, as well as cause noise pollution. Therefore, it is important to suppress the noise from the design stage of the braking system. Based on the establishment of a complex modal finite element model of the brake and verification of the validity of the model through bench test, the mechanism of “contact overlap degree” is proposed, that is, the influence of the brake disc-block friction contact overlap degree on the brake noise. In order to better simulate the real situation during brake friction contact, a face-spring distributed contact model of the brake is developed and the key influencing factors of contact overlap degree are selected. Based on the asymmetry and unevenness of contact overlap degree distribution, the structural optimization schemes of brake backplane and friction lining are proposed respectively, and the complex modal analysis is re-performed. The analysis results show that the noise incidence is reduced after structural optimization, which verifies the effectiveness of the above two structural optimization schemes in reducing brake noise.
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Muhammad, Zaka, Md Mahbub Alam, and Bernd R. Noack. "Efficient thrust enhancement by modified pitching motion." Journal of Fluid Mechanics 933 (December 21, 2021). http://dx.doi.org/10.1017/jfm.2021.1040.
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Thrust and/or efficiency of a pitching foil (mimicking a tail of swimming fish) can be enhanced by tweaking the pitching waveform. The literature, however, show that non-sinusoidal pitching waveforms can enhance either thrust or efficiency but not both simultaneously. With the knowledge and inspiration from nature, we devised and implemented a novel asymmetrical sinusoidal pitching motion that is a combination of two sinusoidal motions having periods T1 and T2 for the forward and retract strokes, respectively. The motion is represented by period ratio $\mathrm{\mathbb{T}} = {T_1}/T$ , where T = (T1 + T2)/2, with $\mathrm{\mathbb{T}} > 1.00$ giving the forward strokes (from equilibrium to extreme position) slower than the retract strokes (from extreme to equilibrium position) and vice versa. The novel pitching motion enhances both thrust and efficiency for $\mathrm{\mathbb{T}} > 1.00$ . The enhancement results from the resonance between the shear-layer roll up and the increased speed of the foil. Four swimming regimes, namely normal swimming, undesirable, floating and ideal are discussed, based on instantaneous thrust and power. The results from the novel pitching motion display similarities with those from fish locomotion (e.g. fast start, steady swimming and braking). The $\mathrm{\mathbb{T}} > 1.00$ motion in the faster stroke has the same characteristics and results as the fast start of prey to escape from a predator while $\mathrm{\mathbb{T}} < 1.00$ imitates braking locomotion. While $\mathrm{\mathbb{T}} < 1.00$ enhances the wake deflection at high amplitude-based Strouhal numbers (StA = fA/U∞, where f and A are the frequency and peak-to-peak amplitude of the pitching, respectively, and U∞ is the freestream velocity), $\mathrm{\mathbb{T}} > 1.00$ improves the wake symmetry, suppressing the wake deflection. The wake characteristics including wake width, jet velocity and vortex structures are presented and connected with $S{t_d}( = fd/{U_\infty })$ , ${A^{\ast}}( = A/d)$ and $\mathrm{\mathbb{T}}$ , where d is the maximum thickness of the foil.
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Fey, Nicholas P., Glenn K. Klute, and Richard R. Neptune. "Optimization of Prosthetic Foot Stiffness to Reduce Metabolic Cost and Intact Knee Loading During Below-Knee Amputee Walking: A Theoretical Study." Journal of Biomechanical Engineering 134, no. 11 (October 26, 2012). http://dx.doi.org/10.1115/1.4007824.
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Unilateral below-knee amputees develop abnormal gait characteristics that include bilateral asymmetries and an elevated metabolic cost relative to non-amputees. In addition, long-term prosthesis use has been linked to an increased prevalence of joint pain and osteoarthritis in the intact leg knee. To improve amputee mobility, prosthetic feet that utilize elastic energy storage and return (ESAR) have been designed, which perform important biomechanical functions such as providing body support and forward propulsion. However, the prescription of appropriate design characteristics (e.g., stiffness) is not well-defined since its influence on foot function and important in vivo biomechanical quantities such as metabolic cost and joint loading remain unclear. The design of feet that improve these quantities could provide considerable advancements in amputee care. Therefore, the purpose of this study was to couple design optimization with dynamic simulations of amputee walking to identify the optimal foot stiffness that minimizes metabolic cost and intact knee joint loading. A musculoskeletal model and distributed stiffness ESAR prosthetic foot model were developed to generate muscle-actuated forward dynamics simulations of amputee walking. Dynamic optimization was used to solve for the optimal muscle excitation patterns and foot stiffness profile that produced simulations that tracked experimental amputee walking data while minimizing metabolic cost and intact leg internal knee contact forces. Muscle and foot function were evaluated by calculating their contributions to the important walking subtasks of body support, forward propulsion and leg swing. The analyses showed that altering a nominal prosthetic foot stiffness distribution by stiffening the toe and mid-foot while making the ankle and heel less stiff improved ESAR foot performance by offloading the intact knee during early to mid-stance of the intact leg and reducing metabolic cost. The optimal design also provided moderate braking and body support during the first half of residual leg stance, while increasing the prosthesis contributions to forward propulsion and body support during the second half of residual leg stance. Future work will be directed at experimentally validating these results, which have important implications for future designs of prosthetic feet that could significantly improve amputee care.