Journal articles: 'Stationary obstacles'

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Burnett, Nicholas P., Marc A. Badger, and Stacey A. Combes. "Wind and obstacle motion affect honeybee flight strategies in cluttered environments." Journal of Experimental Biology 223, no. 14 (June 19, 2020): jeb222471. http://dx.doi.org/10.1242/jeb.222471.

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ABSTRACTBees often forage in habitats with cluttered vegetation and unpredictable winds. Navigating obstacles in wind presents a challenge that may be exacerbated by wind-induced motions of vegetation. Although wind-blown vegetation is common in natural habitats, we know little about how the strategies of bees for flying through clutter are affected by obstacle motion and wind. We filmed honeybees Apis mellifera flying through obstacles in a flight tunnel with still air, headwinds or tailwinds. We tested how their ground speeds and centering behavior (trajectory relative to the midline between obstacles) changed when obstacles were moving versus stationary, and how their approach strategies affected flight outcome (successful transit versus collision). We found that obstacle motion affects ground speed: bees flew slower when approaching moving versus stationary obstacles in still air but tended to fly faster when approaching moving obstacles in headwinds or tailwinds. Bees in still air reduced their chances of colliding with obstacles (whether moving or stationary) by reducing ground speed, whereas flight outcomes in wind were not associated with ground speed, but rather with improvement in centering behavior during the approach. We hypothesize that in challenging flight situations (e.g. navigating moving obstacles in wind), bees may speed up to reduce the number of wing collisions that occur if they pass too close to an obstacle. Our results show that wind and obstacle motion can interact to affect flight strategies in unexpected ways, suggesting that wind-blown vegetation may have important effects on foraging behaviors and flight performance of bees in natural habitats.

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Haug, E. J., F. A. Adkins, and D. Coroian. "Domains of Mobility for a Planar Body Moving Among Obstacles." Journal of Mechanical Design 120, no. 3 (September 1, 1998): 462–67. http://dx.doi.org/10.1115/1.2829174.

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A formulation is presented for defining domains of mobility for a planar convex body moving with three degrees-of-freedom among convex planar obstacles. Applications included are determination of areas of a factory floor or material storage facility in which objects can he manipulated without impacting fixed obstacles. Mobility of the moving body is defined to encompass (1) dexterous mobility of the body; i.e., points that can be reached by a reference point on the body and at which the body can be rotated through a specified range of admissible orientations without penetrating any stationary obstacle, and (2) limited mobility of the body; i.e., points that can be reached by the reference point and at which the body does not penetrate any stationary obstacle, for some admissible orientation. Analytical criteria for points on boundaries of domains of mobility are derived and numerical methods suitable for mapping these boundaries are summarized. An elementary example involving a moving and a stationary ellipse, with and without orientation restrictions, is solved analytically to illustrate the method. A more general application with one moving body and three stationary obstacles is solved numerically.

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Wu, Chia-Pin, Tsu-Tian Lee, and Chau-Ren Tsai. "Obstacle avoidance motion planning for mobile robots in a dynamic environment with moving obstacles." Robotica 15, no. 5 (September 1997): 493–510. http://dx.doi.org/10.1017/s0263574797000593.

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A new real-time obstacle avoidance method for mobile robots has been developed. This method, namely the vector-distance function method, permits the detection of obstacles (both moving and stationary) and generates a path that can avoid collisions. The proposed approach expresses the distance information in a vector form. Then the notion of weighting is introduced to describe relationship between sensors of mobile robots and the target to be reached. Furthermore, R-mode, L-mode and T-mode are introduced to generate a safe path for the mobile robot in a dynamic environment filled with both stationary and moving obstacles. The algorithm can deal with a complicated obstacle environment, such as multiple concave and convex obstacles. Simulation results are included to demonstrate the applicability and effectiveness of the developed algorithm.

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Finaev, V. I., M. Yu Medvedev, V. Kh Pshikhopov, V. A. Pereverzev, and V. V. Soloviev. "Unmanned Powerboat Motion Terminal Control in an Environment with Moving Obstacles." Mekhatronika, Avtomatizatsiya, Upravlenie 22, no. 3 (March 2, 2021): 145–54. http://dx.doi.org/10.17587/mau.22.145-154.

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The major point for consideration throughout this paper is controlling the motion of an unmanned powerboat in an obstructed environment with stationary and moving objects. It offers a procedure for the terminal control law development based on the powerboat programmed motion trajectory in a polynomial form and proposes position-trajectory-based control algorithms. A hybrid method based on virtual fields and unstable driving modes, taking into account powerboat speeds and obstacles, is used to plan motion trajectories for obstacle avoidance. There were experiments carried out to test the developed methods and algorithms meanwhile estimating the energy consumption for control, the length of the trajectory and the safety indicator for obstacle avoidance. The novelty of the proposed approach lies in the method used to develop a local movement trajectory in the field with obstacles and in the hybridization of trajectory scheduling methods. This approach allows us to achieve a given safe distance when avoiding obstacles and virtually eliminate the chances of an emergency collision. The presented results can be used in systems of boats autonomous motion control and allow safe stationary and dynamic obstacles avoidance.

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Das, Subir Kumar, Ajoy Kumar Dutta, and Subir Kumar Debnath. "OperativeCriticalPointBug algorithm-local path planning of mobile robot avoiding obstacles." Indonesian Journal of Electrical Engineering and Computer Science 18, no. 3 (June 1, 2020): 1646. http://dx.doi.org/10.11591/ijeecs.v18.i3.pp1646-1656.

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<span>For Autonomous Mobile Robot one of the biggest and interesting issues is path planning. An autonomous mobile robot should be able determine its own path to reach destination. This paper offers a new algorithm for mobile robot to plan a path in local environments with stationary as well as moving obstacles. For movable robots’ path planning OperativeCriticalPointBug (OCPB) algorithm, is a new Bug algorithm. This algorithm is carried out by the robot throughout the movement from source to goal, hence allowing the robot to rectify its way if a new obstacle comes into the route or any existing obstacle changes its route. According as, not only the robot tries to avoid clash with other obstacle but also tries a series of run time adjustment in its way to produce roughly a best possible path. During journey the robot is believed to be capable to act in an unknown location by acquiring information perceived locally. Using this algorithm the robot can avoid obstacle by considering its own as well as the obstacle’s dimension. The obstacle may be static or dynamic. The algorithm belongs to bug family.</span>

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Fahimi, Farbod, C. Nataraj, and Hashem Ashrafiuon. "Real-time obstacle avoidance for multiple mobile robots." Robotica 27, no. 2 (March 2009): 189–98. http://dx.doi.org/10.1017/s0263574708004438.

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SUMMARYAn efficient, simple, and practical real time path planning method for multiple mobile robots in dynamic environments is introduced. Harmonic potential functions are utilized along with the panel method known in fluid mechanics. First, a complement to the traditional panel method is introduced to generate a more effective harmonic potential field for obstacle avoidance in dynamically changing environments. Second, a group of mobile robots working in an environment containing stationary and moving obstacles is considered. Each robot is assigned to move from its current position to a goal position. The group is not forced to maintain a formation during the motion. Every robot considers the other robots of the group as moving obstacles and hence the physical dimensions of the robots are also taken into account. The path of each robot is planned based on the changing position of the other robots and the position of stationary and moving obstacles. Finally, the effectiveness of the scheme is shown by modeling an arbitrary number of mobile robots and the theory is validated by several computer simulations and hardware experiments.

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Soltan, Reza A., Hashem Ashrafiuon, and Kenneth R. Muske. "ODE-based obstacle avoidance and trajectory planning for unmanned surface vessels." Robotica 29, no. 5 (October 4, 2010): 691–703. http://dx.doi.org/10.1017/s0263574710000585.

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SUMMARYA new method for real-time obstacle avoidance and trajectory planning of underactuated unmanned surface vessels is presented. In this method, ordinary differential equations (ODEs) are used to define transitional trajectories that can avoid obstacles and reach a final desired target trajectory using a robust tracking control law. The obstacles are approximated and enclosed by elliptical shapes. A transitional trajectory is then defined by a set of ordinary differential equations whose solution is a stable elliptical limit cycle defining the nearest obstacle on the vessel's path to the target. When no obstacle blocks the vessel's path to its target, the transitional trajectory is defined by exponentially stable ODE whose solution is the target trajectory. The planned trajectories are tracked by the vessel through a sliding mode control law that is robust to environmental disturbances and modeling uncertainties and can be computed in real time. The method is illustrated using a complex simulation example with a moving target and multiple moving and rotating obstacles and a simpler experimental example with stationary obstacles.

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Zamirian, M., and A. V. Kamyad. "Fuzzy Path Planning In A Plane With Stationary Obstacles." Journal of Mathematics and Computer Science 02, no. 03 (April 10, 2011): 417–24. http://dx.doi.org/10.22436/jmcs.02.03.03.

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Foux, G., M. Heymann, and A. Bruckstein. "Two-dimensional robot navigation among unknown stationary polygonal obstacles." IEEE Transactions on Robotics and Automation 9, no. 1 (1993): 96–102. http://dx.doi.org/10.1109/70.210800.

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Boukari, D., R. Djouadi, and D. Teniou. "Free surface flow over an obstacle. Theoretical study of the fluvial case." Abstract and Applied Analysis 6, no. 7 (2001): 413–29. http://dx.doi.org/10.1155/s1085337501000677.

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The two-dimensional stationary flow of a fluid over an obstacle lying on the bottom of a stream is discussed. We take into account the gravity and we neglect the effects of the surface tension. An existence theory for the solution of this problem is established by the implicit function theorem, for small obstacles and Froude numbers in an interval included in]0,1[.

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Nurul Khotimah, Siti, Bergas Bimo Branarto, Sparisoma Viridi, and Idam Arif. "Permeability and Porosity of Two-Dimensional Porous Media Microchannels using Lattice Gas Cellular Automata." Indonesian Journal of Physics 23, no. 1 (July 1, 2012): 5–9. http://dx.doi.org/10.5614/itb.ijp.2012.23.1.2.

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In this study, lattice-gas cellular automata were used to solve the flow of incompressible Newtonian-fluid in porous media microchannels. We discuss fluid flow between two stationary parallel plates. By applying a constant pressure gradient, volumetric flux was determined as a function of time until a steady condition is achieved. For steady laminar flow, its velocity profile is parabolic. For flow in porous media between two stationary parallel plates, the results show that medium permeability depends on porosity and obstacle configurations. For a single obstacle, the permeability is a parabolic function with respect to positions of an obstacle in the direction perpendicular to the flow. The permeability is smallest when the obstacle is at the central line along the flow. A maximum permeability may be achieved when the obstacles attached to the channel wall. Other obstacle structures give lower permeability, even zero permeability for dead end microchannels.

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Ho, Yu-Tsung, Nobuyoshi Kawabata, Miho Seike, Masato Hasegawa, Shen-Wen Chien, and Tzu-Sheng Shen. "Scale Model Experiments and Simulations to Investigate the Effect of Vehicular Blockage on Backlayering Length in Tunnel Fire." Buildings 12, no. 7 (July 13, 2022): 1006. http://dx.doi.org/10.3390/buildings12071006.

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This study used model experiments and numerical simulations to investigate the backlayering length of a vehicle-blocked tunnel fire. The experimental setup included two types of obstacles (low obstacles and high obstacles), as well as three configurations: no obstacles, one side with a car obstacle, and two sides with a car obstacle. If there were vehicles on one side of a lane, it would have little effect on the elongation of the backlayer length. When there were vehicles on both sides of a lane, the elongation of the backlayer length was greatly reduced. In addition, the effects of the vehicular blockage ratio and blockage configuration on the properties of the backlayering length were investigated. We created Pattern A, where fire is was in the center, and Pattern B, where fire was on the side of the tunnel. In Pattern A, almost all obstacles could be approximated using the formula. When the vehicle blockage ratio of a single lane was small, an approximation formula for Pattern B was applicable. However, if the distance between stationary vehicles on the upstream side of the fire source was small, the backlayering length could have been longer than in the case with no vehicular blockage.

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Lee, Ki-Ahm, and Se-Chan Lee. "Viscosity method for random homogenization of fully nonlinear elliptic equations with highly oscillating obstacles." Advances in Nonlinear Analysis 12, no. 1 (September 8, 2022): 266–303. http://dx.doi.org/10.1515/anona-2022-0273.

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Abstract In this article, we establish a viscosity method for random homogenization of an obstacle problem with nondivergence structure. We study the asymptotic behavior of the viscosity solution u ε {u}_{\varepsilon } of fully nonlinear equations in a perforated domain with the stationary ergodic condition. By capturing the behavior of the homogeneous solution, analyzing the characters of the corresponding obstacle problem, and finding the capacity-like quantity through the construction of appropriate barriers, we prove that the limit profile u u of u ε {u}_{\varepsilon } satisfies a homogenized equation without obstacles.

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KLYMAK, JODY M., SONYA M. LEGG, and ROBERT PINKEL. "High-mode stationary waves in stratified flow over large obstacles." Journal of Fluid Mechanics 644 (February 10, 2010): 321–36. http://dx.doi.org/10.1017/s0022112009992503.

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Simulations of steady two-dimensional stratified flow over an isolated obstacle are presented where the obstacle is tall enough so that the topographic Froude number, Nhm/Uo ≫ 1. N is the buoyancy frequency, hm the height of the topography from the channel floor and Uo the flow speed infinitely far from the obstacle. As for moderate Nhm/Uo (~1), a columnar response propagates far up- and downstream, and an arrested lee wave forms at the topography. Upstream, most of the water beneath the crest is blocked, while the moving layer above the crest has a mean velocity Um = UoH/(H−hm). The vertical wavelength implied by this velocity scale, λo = 2πUm/N, predicts dominant vertical scales in the flow. Upstream of the crest there is an accelerated region of fluid approximately λo thick, above which there is a weakly oscillatory flow. Downstream the accelerated region is thicker and has less intense velocities. Similarly, the upstream lift of isopycnals is greatest in the first wavelength near the crest, and weaker above and below. Form drag on the obstacle is dominated by the blocked response, and not on the details of the lee wave, unlike flows with moderate Nhm/Uo.Directly downstream, the lee wave that forms has a vertical wavelength given by λo, except for the deepest lobe which tends to be thicker. This wavelength is small relative to the fluid depth and topographic height, and has a horizontal phase speed cpx = −Um, corresponding to an arrested lee wave. When considering the spin-up to steady state, the speed of vertical propagation scales with the vertical component of group velocity cgz = αUm, where α is the aspect ratio of the topography. This implies a time scale = tNα/2π for the growth of the lee waves, and that steady state is attained more rapidly with steep topography than shallow, in contrast with linear theory, which does not depend on the aspect ratio.

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Huang, Tingting, and Hee-Chang Lim. "Simulation of Lid-Driven Cavity Flow with Internal Circular Obstacles." Applied Sciences 10, no. 13 (July 1, 2020): 4583. http://dx.doi.org/10.3390/app10134583.

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The Lattice Boltzmann method (LBM) has been applied for the simulation of lid-driven flows inside cavities with internal two-dimensional circular obstacles of various diameters under Reynolds numbers ranging from 100 to 5000. With the LBM, a simplified square cross-sectional cavity was used and a single relaxation time model was employed to simulate complex fluid flow around the obstacles inside the cavity. In order to made better convergence, well-posed boundary conditions should be defined in the domain, such as no-slip conditions on the side and bottom solid-wall surfaces as well as the surface of obstacles and uniform horizontal velocity at the top of the cavity. This study focused on the flow inside a square cavity with internal obstacles with the objective of observing the effect of the Reynolds number and size of the internal obstacles on the flow characteristics and primary/secondary vortex formation. The current LBM has been successfully used to precisely simulate and visualize the primary and secondary vortices inside the cavity. In order to validate the results of this study, the results were compared with existing data. In the case of a cavity without any obstacles, as the Reynolds number increases, the primary vortices move toward the center of the cavity, and the secondary vortices at the bottom corners increase in size. In the case of the cavity with internal obstacles, as the Reynolds number increases, the secondary vortices close to the internal obstacle become smaller owing to the strong primary vortices. In contrast, depending on the sizes of the obstacles ( R / L = 1/16, 1/6, 1/4, and 2/5), secondary vortices are induced at each corner of the cavity and remain stationary, but the secondary vortices close to the top of the obstacle become larger as the size of the obstacle increases.

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Azizi, Aydin, Farshid Entesari, Kambiz Ghaemi Osgouie, and Mostafa Cheragh. "Intelligent Mobile Robot Navigation in an Uncertain Dynamic Environment." Applied Mechanics and Materials 367 (August 2013): 388–92. http://dx.doi.org/10.4028/www.scientific.net/amm.367.388.

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This paper presents a modified sensor-based online method for mobile robot navigation generating paths in dynamic environments. The core of the navigation algorithm is based on the velocity obstacle avoidance method and the guidance-based tracking algorithm. A fuzzy decision maker is designed to combine the two mentioned algorithms intelligently. Hence the robot will be able to decide intelligently in various situations when facing the moving obstacles and moving target. A noble noise cancellation algorithm using Neural Network is designed to navigate the robot in an uncertain dynamic environment safely. The results show that the robot can track a moving target while maneuvering safely in dynamic environment and avoids stationary and moving obstacles.

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Blaxter, J. H. S., and R. S. Batty. "Herring Behaviour in the Dark: Responses to Stationary and Continuously Vibrating Obstacles." Journal of the Marine Biological Association of the United Kingdom 65, no. 4 (November 1985): 1031–49. http://dx.doi.org/10.1017/s0025315400019494.

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The behaviour of herring subjected to stationary and vibrating obstacles in their swimming path was recorded in daylight and darkness using an infra-red sensitive TV system. The herring avoided stationary obstacles using visual stimuli and usually collided with such obstacles in darkness. They showed strong avoidance to a continuously vibrating sound source in darkness but the speed of turning was relatively slow and there was no evidence for habituation. As they approached the source they usually responded when the sound pressure reached 10–20 Pa, about 70 dB above the threshold. Particle velocity within the lateral line canals was calculated and was 40–60 dB above threshold. Herring seem to be able to adapt their avoidance behaviour to suit the urgency of the situation.

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Tuvshinjargal, Doopalam, Byambaa Dorj, and Deok Jin Lee. "Hybrid Motion Planning Method for Autonomous Robots Using Kinect Based Sensor Fusion and Virtual Plane Approach in Dynamic Environments." Journal of Sensors 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/471052.

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A new reactive motion planning method for an autonomous vehicle in dynamic environments is proposed. The new dynamic motion planning method combines a virtual plane based reactive motion planning technique with a sensor fusion based obstacle detection approach, which results in improving robustness and autonomy of vehicle navigation within unpredictable dynamic environments. The key feature of the new reactive motion planning method is based on a local observer in the virtual plane which allows the effective transformation of complex dynamic planning problems into simple stationary in the virtual plane. In addition, a sensor fusion based obstacle detection technique provides the pose estimation of moving obstacles by using a Kinect sensor and a sonar sensor, which helps to improve the accuracy and robustness of the reactive motion planning approach in uncertain dynamic environments. The performance of the proposed method was demonstrated through not only simulation studies but also field experiments using multiple moving obstacles even in hostile environments where conventional method failed.

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TATEBE, Kenji, and Hajimu NAKAJIMA. "AVOIDANCE BEHAVIOR AGAINST A STATIONARY OBSTACLE UNDER SINGLE WALKING : A study on pedestrian behavior of avoiding obstacles (I)." Journal of Architecture, Planning and Environmental Engineering (Transactions of AIJ) 418 (1990): 51–57. http://dx.doi.org/10.3130/aijax.418.0_51.

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Li, Zhi, Lei Liu, Jiaqiang Wang, Li Lin, Jichang Dong, and Zhi Dong. "Design and Analysis of an Effective Multi-Barriers Model Based on Non-Stationary Gaussian Random Fields." Electronics 12, no. 2 (January 9, 2023): 345. http://dx.doi.org/10.3390/electronics12020345.

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In this paper, we propose an extension to the barrier model, i.e., the Multi-Barriers Model, which could characterize an area of interest with different types of obstacles. In the proposed model, the area of interest is divided into two or more areas, which include a general area of interest with sampling points and the rest of the area with different types of obstacles. Firstly, the correlation between the points in space is characterized by the obstruction degree of the obstacle. Secondly, multiple Gaussian random fields are constructed. Then, continuous Gaussian fields are expressed by using stochastic partial differential equations (SPDEs). Finally, the integrated nested Laplace approximation (INLA) method is employed to calculate the posterior mean of parameters and the posterior parameters to establish a spatial regression model. In this paper, the Multi-Barriers Model is also verified by using the geostatistical model and log-Gaussian Cox model. Furthermore, the stationary Gaussian model, the barrier model and the Multi-Barriers Model are investigated in the geostatistical data, respectively. Real data sets of burglaries in a certain area are used to compare the performance of the stationary Gaussian model, barrier model and Multi-Barriers Model. The comparison results suggest that the three models achieve similar performance in the posterior mean and posterior distribution of the parameters, as well as the deviance information criteria (DIC) value. However, the Multi-Barriers Model can better interpret the spatial model established based on the spatial data of the research areas with multiple types of obstacles, and it is closer to reality.

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Shen, Junjie, Yiwen Chen, and Hideyuki Sawada. "A Wearable Assistive Device for Blind Pedestrians Using Real-Time Object Detection and Tactile Presentation." Sensors 22, no. 12 (June 16, 2022): 4537. http://dx.doi.org/10.3390/s22124537.

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Nowadays, improving the traffic safety of visually impaired people is a topic of widespread concern. To help avoid the risks and hazards of road traffic in their daily life, we propose a wearable device using object detection techniques and a novel tactile display made from shape-memory alloy (SMA) actuators. After detecting obstacles in real-time, the tactile display attached to a user’s hands presents different tactile sensations to show the position of the obstacles. To implement the computation-consuming object detection algorithm in a low-memory mobile device, we introduced a slimming compression method to reduce 90% of the redundant structures of the neural network. We also designed a particular driving circuit board that can efficiently drive the SMA-based tactile displays. In addition, we also conducted several experiments to verify our wearable assistive device’s performance. The results of the experiments showed that the subject was able to recognize the left or right position of a stationary obstacle with 96% accuracy and also successfully avoided collisions with moving obstacles by using the wearable assistive device.

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Khaled, Nassim, and Rami Alkhatib. "Novel Formulation for Line of Sight Guidance and Obstacle Avoidance for Under-actuated Ships." WSEAS TRANSACTIONS ON CIRCUITS AND SYSTEMS 20 (March 16, 2021): 1–9. http://dx.doi.org/10.37394/23201.2021.20.1.

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Automatic control of under-actuated ships is a challenging task due to the external factors and limited actuators onboard a ship. It is even more so when the controller needs to seamlessly integrate with a guidance system and obstacle avoidance for the purpose of autonimity. In this paper, line of sight guidance system for marine surface vessels is augmented to include obstacle avoidance. The process of directing the ship movement to avoid a stationary and moving obstacles is tackled by introducing an iterative mathematical formulation for the circle of avoidance algorithm. Unlike learning based guidance system, the proposed formulation has an explicit solution that is updated at each instant in time. Three simulations are conducted to assess the performance of the overall guidance and avoidance system. The developed algorithm is validated through simulation results of a 6-degree of freedom model of a ship. The simulation results prove the effectiveness of the developed technique to converge the ship to the desired trajectory autonomously while avoiding obstacles along the path.

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Çetin, Ender, Cristina Barrado, and Enric Pastor. "Counter a Drone in a Complex Neighborhood Area by Deep Reinforcement Learning." Sensors 20, no. 8 (April 18, 2020): 2320. http://dx.doi.org/10.3390/s20082320.

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Counter-drone technology by using artificial intelligence (AI) is an emerging technology and it is rapidly developing. Considering the recent advances in AI, counter-drone systems with AI can be very accurate and efficient to fight against drones. The time required to engage with the target can be less than other methods based on human intervention, such as bringing down a malicious drone by a machine-gun. Also, AI can identify and classify the target with a high precision in order to prevent a false interdiction with the targeted object. We believe that counter-drone technology with AI will bring important advantages to the threats coming from some drones and will help the skies to become safer and more secure. In this study, a deep reinforcement learning (DRL) architecture is proposed to counter a drone with another drone, the learning drone, which will autonomously avoid all kind of obstacles inside a suburban neighborhood environment. The environment in a simulator that has stationary obstacles such as trees, cables, parked cars, and houses. In addition, another non-malicious third drone, acting as moving obstacle inside the environment was also included. In this way, the learning drone is trained to detect stationary and moving obstacles, and to counter and catch the target drone without crashing with any other obstacle inside the neighborhood. The learning drone has a front camera and it can capture continuously depth images. Every depth image is part of the state used in DRL architecture. There are also scalar state parameters such as velocities, distances to the target, distances to some defined geofences and track, and elevation angles. The state image and scalars are processed by a neural network that joints the two state parts into a unique flow. Moreover, transfer learning is tested by using the weights of the first full-trained model. With transfer learning, one of the best jump-starts achieved higher mean rewards (close to 35 more) at the beginning of training. Transfer learning also shows that the number of crashes during training can be reduced, with a total number of crashed episodes reduced by 65%, when all ground obstacles are included.

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Karageorghis, Andreas, and Daniel Lesnic. "Identification of obstacles immersed in a stationary Oseen fluid via boundary measurements." Inverse Problems in Science and Engineering 28, no. 7 (November 6, 2019): 950–67. http://dx.doi.org/10.1080/17415977.2019.1686498.

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Orbach, Dara N., and Brock Fenton. "Vision Impairs the Abilities of Bats to Avoid Colliding with Stationary Obstacles." PLoS ONE 5, no. 11 (November 9, 2010): e13912. http://dx.doi.org/10.1371/journal.pone.0013912.

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Ramabalan, S., V. Sathiya, and M. Chinnadurai. "Wheeled Mobile Robot Trajectory Planning Using Evolutionary Techniques." INTERNATIONAL JOURNAL OF ADVANCED PRODUCTION AND INDUSTRIAL ENGINEERING 5, no. 3 (July 5, 2020): 34–38. http://dx.doi.org/10.35121/ijapie202007346.

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This paper proposes two multi-objective trajectory planning optimization algorithms namely Multi-Objective Differential Evolution (MODE) and Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II). They are applied for a differential drive wheels mobile robot (WMR). A cubic NURBS curve is used to constitute the mobile robot’s path. The objective functions considered are travel time, traveled length, and actuators' efforts. All objective functions are to be minimized. The constraints considered are the mobile robot’s kinematic limits, obstacle avoidance, and dynamic limits. Two Stationary and five moving obstacles are present around the robot. Experimental and numerical simulation results are examined and compared.

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Mitsch, Stefan, Khalil Ghorbal, David Vogelbacher, and André Platzer. "Formal verification of obstacle avoidance and navigation of ground robots." International Journal of Robotics Research 36, no. 12 (October 2017): 1312–40. http://dx.doi.org/10.1177/0278364917733549.

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This article answers fundamental safety questions for ground robot navigation: under which circumstances does which control decision make a ground robot safely avoid obstacles? Unsurprisingly, the answer depends on the exact formulation of the safety objective, as well as the physical capabilities and limitations of the robot and the obstacles. Because uncertainties about the exact future behavior of a robot’s environment make this a challenging problem, we formally verify corresponding controllers and provide rigorous safety proofs justifying why the robots can never collide with the obstacle in the respective physical model. To account for ground robots in which different physical phenomena are important, we analyze a series of increasingly strong properties of controllers for increasingly rich dynamics and identify the impact that the additional model parameters have on the required safety margins. We analyze and formally verify: (i) static safety, which ensures that no collisions can happen with stationary obstacles; (ii) passive safety, which ensures that no collisions can happen with stationary or moving obstacles while the robot moves; (iii) the stronger passive-friendly safety, in which the robot further maintains sufficient maneuvering distance for obstacles to avoid collision as well; and (iv) passive orientation safety, which allows for imperfect sensor coverage of the robot, i.e., the robot is aware that not everything in its environment will be visible. We formally prove that safety can be guaranteed despite sensor uncertainty and actuator perturbation. We complement these provably correct safety properties with liveness properties: we prove that provably safe motion is flexible enough to let the robot navigate waypoints and pass intersections. To account for the mixed influence of discrete control decisions and the continuous physical motion of the ground robot, we develop corresponding hybrid system models and use differential dynamic logic theorem-proving techniques to formally verify their correctness. Since these models identify a broad range of conditions under which control decisions are provably safe, our results apply to any control algorithm for ground robots with the same dynamics. As a demonstration, we also synthesize provably correct runtime monitor conditions that check the compliance of any control algorithm with the verified control decisions.

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Al-Salah, Abdalla, and Saleh Zein-Sabatto. "Development a Real Time Stationary Obstacles Avoidance Scheme for Autonomous Vehicle Navigation System." International Journal of Industrial Control Systems Security 3, no. 1 (June 30, 2020): 83–89. http://dx.doi.org/10.20533/ijicss.9781.9083.20346.2020.0009.

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TOMITA, Masaaki, and Motoji YAMAMOTO. "A Navigation Algorithm for Avoidance of Moving and Stationary Obstacles for Mobile Robot." Transactions of the Japan Society of Mechanical Engineers Series C 74, no. 748 (2008): 2976–84. http://dx.doi.org/10.1299/kikaic.74.2976.

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van der Sman, R. G. M. "Effects of confinement on hydrodynamic interactions between a suspended sphere and stationary obstacles." Computers & Fluids 58 (April 2012): 63–69. http://dx.doi.org/10.1016/j.compfluid.2012.01.003.

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Dondl, Patrick W., Michael Scheutzow, and Sebastian Throm. "Pinning of interfaces in a random elastic medium and logarithmic lattice embeddings in percolation." Proceedings of the Royal Society of Edinburgh: Section A Mathematics 145, no. 3 (June 2015): 481–512. http://dx.doi.org/10.1017/s0308210512001291.

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For a model of a driven interface in an elastic medium with random obstacles we prove the existence of a stationary positive supersolution at non-vanishing driving force. This shows the emergence of a rate-independent hysteresis through the interaction of the interface with the obstacles despite a linear (force = velocity) microscopic kinetic relation. We also prove a percolation result, namely, the possibility to embed the graph of an only logarithmically growing function in a next-nearest neighbour site percolation cluster at a non-trivial percolation threshold.

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Rostane, Brahim, and Said Abboudi. "Numerical Study of Laminar Fluid Flow Around Two Heated Wall-Mounted Perforated Cubes in Tandem Arrangement." International Journal of Heat and Technology 40, no. 1 (February 28, 2022): 157–66. http://dx.doi.org/10.18280/ijht.400119.

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In this study, the forced convection of a stationary laminar flow over two heated wall-mounted perforated cubes are presented. These two cubes are placed in a tandem arrangement on a flat plate. The equations of continuity, momentum and energy are solved using the finite volume method based on the Rhie and Chow method for velocity-pressure coupling. The influence of the perforation volume of the cubes is studied and compared with the case of obstacles without holes for a constant heat flux subjected to the solid part. The results of mean Nusselt number and drag coefficients are presented at the levels of the two obstacles and the plane plate for different Reynolds numbers and different distances between them. The results showed that the insertion of holes in the cubes improves heat transfer from the diameter D/H=0.62, and this transfer rises with increasing diameter of the perforation of the cubes. The results showed also a decrease in the drag coefficient for the first obstacle with rising volume of the perforation.

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Kardan, Iman, Alireza Akbarzadeh, and Ali Mousavi Mohammadi. "Real-time velocity scaling and obstacle avoidance for industrial robots using fuzzy dynamic movement primitives and virtual impedances." Industrial Robot: An International Journal 45, no. 1 (January 15, 2018): 110–26. http://dx.doi.org/10.1108/ir-02-2017-0035.

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Purpose This paper aims to increase the safety of the robots’ operation by developing a novel method for real-time implementation of velocity scaling and obstacle avoidance as the two widely accepted safety increasing concepts. Design/methodology/approach A fuzzy version of dynamic movement primitive (DMP) framework is proposed as a real-time trajectory generator with imbedded velocity scaling capability. Time constant of the DMP system is determined by a fuzzy system which makes decisions based on the distance from obstacle to the robot’s workspace and its velocity projection toward the workspace. Moreover, a combination of the DMP framework with a human-like steering mechanism and a novel configuration of virtual impedances is proposed for real-time obstacle avoidance. Findings The results confirm the effectiveness of the proposed method in real-time implementation of the velocity scaling and obstacle avoidance concepts in different cases of single and multiple stationary obstacles as well as moving obstacles. Practical implications As the provided experiments indicate, the proposed method can effectively increase the real-time safety of the robots’ operations. This is achieved by developing a simple method with low computational loads. Originality/value This paper proposes a novel method for real-time implementation of velocity scaling and obstacle avoidance concepts. This method eliminates the need for modification of original DMP formulation. The velocity scaling concept is implemented by using a fuzzy system to adjust the DMP’s time constant. Furthermore, the novel impedance configuration makes it possible to obtain a non-oscillatory convergence to the desired path, in all degrees of freedom.

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Shi, Pu, and Jian Ning Hua. "Mobile Robot Dynamic Path Planning Based on Artificial Potential Field Approach." Advanced Materials Research 490-495 (March 2012): 994–98. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.994.

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Artificial potential field based mobile robot path planning approaches have been widely used. However, most methods are applied in the static environment where the target and the obstacles are stationary. In this paper, a potential field approach used in dynamic situation is proposed. Its major characteristics include a new attractive potential function as well as a repulsive potential function. The former takes the relative position and velocity between the robot and the target into consideration; the latter takes into account the relative position and velocity between the robot and the obstacles. The proposed approach guarantees the robot can track the moving target while escape from moving obstacles. Simulation experiments are carried out and the results demonstrate the effectiveness of the new potential field method.

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Hoy, Michael, Alexey S. Matveev, and Andrey V. Savkin. "Algorithms for collision-free navigation of mobile robots in complex cluttered environments: a survey." Robotica 33, no. 3 (March 4, 2014): 463–97. http://dx.doi.org/10.1017/s0263574714000289.

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SUMMARYWe review a range of techniques related to navigation of unmanned vehicles through unknown environments with obstacles, especially those that rigorously ensure collision avoidance (given certain assumptions about the system). This topic continues to be an active area of research, and we highlight some directions in which available approaches may be improved. The paper discusses models of the sensors and vehicle kinematics, assumptions about the environment, and performance criteria. Methods applicable to stationary obstacles, moving obstacles and multiple vehicles scenarios are all reviewed. In preference to global approaches based on full knowledge of the environment, particular attention is given to reactive methods based on local sensory data, with a special focus on recently proposed navigation laws based on model predictive and sliding mode control.

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Makarenko, N. I., and V. K. Kostikov. "Non-linear water waves generated by impulsive motion of submerged obstacles." Natural Hazards and Earth System Sciences 14, no. 4 (April 8, 2014): 751–56. http://dx.doi.org/10.5194/nhess-14-751-2014.

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Abstract. A fully non-linear problem on unsteady water waves generated by an impulsively moving obstacle is studied analytically. Our method involves reduction of the Euler equations to the integral-differential system for the wave elevation together with normal and tangential fluid velocities at a free surface. Exact model equations are derived in explicit form in a case where an isolated obstacle is presented by a totally submerged elliptic cylinder. A small-time asymptotic solution is constructed for a cylinder which starts with constant acceleration from rest. It is demonstrated that the leading-order solution terms describe several wave regimes such as the formation of non-stationary splash jets by vertical rising or vertical submersion of the obstacle; the generation of diverging waves is also observed.

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Вараскин and A. Varaskin. "Physical Modeling of Tornadoes." Safety in Technosphere 2, no. 5 (October 25, 2013): 3–11. http://dx.doi.org/10.12737/1572.

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The principal possibility of tornadoes physical modeling in vitro without use of mechanical twisting devices has been shown. The results of experiments on studying related to opportunities of whirlwinds control are given. The offered and approved method of impact on whirlwinds (tornado), consisting in an arrangement of obstacles in the form of vertical grids in a way of vortex structures distribution, has been described. The method efficiency is verified in vitro by studying of specified obstacles influence on dynamics of the free non-stationary whirlwinds having structure, similar to real tornadoes. The main physical mechanisms related to impact on tornadoes of the offered passive and active method have been briefly considered.

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Mehmood, Asif, Rashid Mahmood, Afraz Hussain Majeed, and Farah Jabeen Awan. "Flow of the Bingham-Papanastasiou Regularized Material in a Channel in the Presence of Obstacles: Correlation between Hydrodynamic Forces and Spacing of Obstacles." Modelling and Simulation in Engineering 2021 (April 27, 2021): 1–14. http://dx.doi.org/10.1155/2021/5583110.

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The numerical modeling and simulation for the stationary Bingham fluid flow around two confined circular cylinders with various gap ratios are studied. The singularity in the model’s apparent viscosity is dealt by Papanastasiou’s regularization. The model equations are discretized by adopting the methodology based on finite element method (FEM) by choosing a mixed higher order LBB-stable P 2 − P 1 finite element pair. The direct solver PARADISO has been utilized to solve the linearized system of equations. Hydrodynamic forces represented by drag and lift coefficients are computed, and a correlation coefficient is calculated for the gap ratios 0.1 ≤ G p ≤ 0.3 and for several values of the Bingham number 0 ≤ B n ≤ 50 . Line graphs for horizontal and vertical velocities are drawn. Moreover, velocity and pressure profiles are plotted for pertinent values of the parameters. Plug and shear zones are revealed via velocity snapshots in the domain. Pressure is nonlinear in the vicinity of the obstacles and becomes linear downstream in the cylinders as expected in channel flows.

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Ciallella, Alessandro, and Emilio N. M. Cirillo. "Linear Boltzmann dynamics in a strip with large reflective obstacles: Stationary state and residence time." Kinetic & Related Models 11, no. 6 (2018): 1475–501. http://dx.doi.org/10.3934/krm.2018058.

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Kim, Dugyu, and Hyunseok Kim. "Very weak solutions of the stationary Navier–Stokes equations for an incompressible fluid past obstacles." Nonlinear Analysis: Theory, Methods & Applications 147 (December 2016): 145–68. http://dx.doi.org/10.1016/j.na.2016.08.017.

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Gómez, Delfina, Miguel Lobo, and María‐Eugenia Pérez‐Martínez. "Asymptotics for models of non‐stationary diffusion in domains with a surface distribution of obstacles." Mathematical Methods in the Applied Sciences 42, no. 1 (October 23, 2018): 403–13. http://dx.doi.org/10.1002/mma.5323.

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Shinde, Vijaysingh, Ashish Dutta, and Anupam Saxena. "Experiments on multi-agent capture of a stochastically moving object using modified projective path planning." Robotica 31, no. 2 (May 24, 2012): 267–84. http://dx.doi.org/10.1017/s0263574712000239.

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SUMMARYMost of the past research in swarm robotics has considered object capture and transport using a specified and very large number of agents. The objects therein were either stationary or moving deterministically (i.e., along a known path). In most previous efforts, the obstacles were also considered stationary. Here we present a modified projective path planning algorithm and illustrate via laboratory experiments that an object exhibiting stochastic (unplanned) but low-speed motion can be restrained by a limited number of agents guided in real-time across randomly moving obstacles. Relaxation of certain restrictions in the grasping objective allows for the determination of a minimum number and placement of agents around the perimeter of any generically shaped prismatic object. A closed loop experiment is designed using a single overhead camera that provides the visual feedback and helps determine the instantaneous positions of all entities in the workspace. Control signals are sent to the robots via wireless modules by a central processing unit to navigate and guide them to their respective new positions in the subsequent time-step. Agents continue to receive signals until they restrict the moving object in form closure.

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Chadi, Kamel, Nourredine Belghar, Belhi Guerira, and Driss Zied. "Numerical Study in Three Dimensions of Influence of the Fluids Nature and Obstacle Position on the Electronic Component Cooling." Defect and Diffusion Forum 406 (January 2021): 110–21. http://dx.doi.org/10.4028/www.scientific.net/ddf.406.110.

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In this work, we have studied numerically the influence of the nature of nanofluids and the obstacle position, within the mini-channel of dimensions (10 x 10 x 108 mm3) on the electronic component cooling. The power of the electronic component is constant. In these simulations we have considered the Al2O3-water, SiO2-water and TiO2-water as coolants. The numerical results are obtained by choosing a Reynolds number (Re) between 300 and 500 and considering that the flow regime is stationary. The simulation was performed using the software, ANSYS FLUENT.The analysis of the simulation results shows that the position of obstacles within the mini-channel has considerable effects on the improvement of the electronic component temperature. The results also showed that among the nanofluids studied, the liquid containing nanoparticles Al2O3-water is the best for the electronic component cooling.

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44

Chadi, Kamel, Nourredine Belghar, Belhi Guerira, and Driss Zied. "Numerical Study in Three Dimensions of Influence of the Fluids Nature and Obstacle Position on the Electronic Component Cooling." Defect and Diffusion Forum 406 (January 2021): 110–21. http://dx.doi.org/10.4028/www.scientific.net/ddf.406.110.

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In this work, we have studied numerically the influence of the nature of nanofluids and the obstacle position, within the mini-channel of dimensions (10 x 10 x 108 mm3) on the electronic component cooling. The power of the electronic component is constant. In these simulations we have considered the Al2O3-water, SiO2-water and TiO2-water as coolants. The numerical results are obtained by choosing a Reynolds number (Re) between 300 and 500 and considering that the flow regime is stationary. The simulation was performed using the software, ANSYS FLUENT.The analysis of the simulation results shows that the position of obstacles within the mini-channel has considerable effects on the improvement of the electronic component temperature. The results also showed that among the nanofluids studied, the liquid containing nanoparticles Al2O3-water is the best for the electronic component cooling.

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Zhang, Lin, Taoyun Zhou, and Baowang Lian. "Integrated IMU with Faster R-CNN Aided Visual Measurements from IP Cameras for Indoor Positioning." Sensors 18, no. 9 (September 17, 2018): 3134. http://dx.doi.org/10.3390/s18093134.

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Considering the radio-based indoor positioning system pertaining to signal degradation due to the environmental factors, and rising popularity of IP (Internet Protocol) cameras in cities, a novel fusion of inertial measurement units (IMUs) with external IP cameras to determine the positions of moving users in indoor environments is presented. This approach uses a fine-tuned Faster R-CNN (Region Convolutional Neural Network) to detect users in images captured by cameras, and acquires visual measurements including ranges and angles of users with respect to the cameras based on the proposed monocular vision relatively measuring (MVRM) method. The results are determined by integrating the positions predicted by each user’s inertial measurement unit (IMU) and visual measurements using an EKF (Extended Kalman Filter). The results experimentally show that the ranging accuracy is affected by both the detected bounding box’s by Faster R-CNN height errors and diverse measuring distances, however, the heading accuracy is solely interfered with bounding box’s horizontal biases. The indoor obstacles including stationary obstacles and a pedestrian in our tests more significantly decrease the accuracy of ranging than that of heading, and the effect of a pedestrian on the heading errors is greater than stationary obstacles on that. We implemented a positioning test for a single user and an external camera in five indoor scenarios to evaluate the performance. The robust fused IMU/MVRM solution significantly decreases the positioning errors and shows better performance in dense multipath scenarios compared with the pure MVRM solution and ultra-wideband (UWB) solution.

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Sadegh, Nader. "Dual objective motion planning subject to state constraints." Robotica 35, no. 5 (December 14, 2015): 1157–75. http://dx.doi.org/10.1017/s026357471500106x.

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SUMMARYThis paper presents a novel motion planning approach inspired by the Dynamic Programming (DP) applicable to multi degree of freedom robots (mobile or stationary) and autonomous vehicles. The proposed discrete–time algorithm enables a robot to reach its destination through an arbitrary obstacle field in the fewest number of time steps possible while minimizing a secondary objective function. Furthermore, the resulting optimal trajectory is guaranteed to be globally optimal while incorporating state constraints such as velocity, acceleration, and jerk limits. The optimal trajectories furnished by the algorithm may be further updated in real time to accommodate changes in the obstacle field and/or cost function. The algorithm is proven to terminate in a finite number of steps without its computational complexity increasing with the type or number of obstacles. The effectiveness of the global and replanning algorithms are demonstrated on a planar mobile robot with three degrees of freedom subject to velocity and acceleration limits. The computational complexity of the two algorithms are also compared to that of an A*–type search.

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Li, Kene, Chengzhi Yuan, Jingjing Wang, and Xiaonan Dong. "Four-Direction Search Scheme of Path Planning for Mobile Agents." Robotica 38, no. 3 (June 13, 2019): 531–40. http://dx.doi.org/10.1017/s0263574719000821.

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SummaryThis paper presents a neural network-based four-direction search scheme of path planning for mobile agents, given a known environmental map with stationary obstacles. Firstly, the map collision energy is modeled for all the obstacles based on neural network. Secondly, for the shorted path-search purpose, the path energy is considered. Thirdly, to decrease the path-search time, a variable step-length is designed with respect to collision energy of the previous iteration path. Simulation results demonstrate that the variable step-length is effective and can decrease the iteration time substantially. Lastly, experimental results show that the mobile agent tracks the generated path well. Both the simulation and experiment results substantiate the feasibility and realizability of the presented scheme.

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De Stefano, Giuliano, Alireza Nejadmalayeri, and Oleg V. Vasilyev. "Wall-resolved wavelet-based adaptive large-eddy simulation of bluff-body flows with variable thresholding." Journal of Fluid Mechanics 788 (January 5, 2016): 303–36. http://dx.doi.org/10.1017/jfm.2015.708.

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The wavelet-based eddy-capturing approach with variable thresholding is extended to bluff-body flows, where the obstacle geometry is enforced through Brinkman volume penalization. The use of a spatio-temporally varying threshold allows one to perform adaptive large-eddy simulations with the prescribed fidelity on a near optimal computational mesh. The space–time evolution of the threshold variable is achieved by solving a transport equation based on the Lagrangian path-line diffusive averaging methodology. The coupled wavelet-collocation/volume-penalization approach with variable thresholding is illustrated for a turbulent incompressible flow around an isolated stationary prism with square cross-section. Wavelet-based adaptive large-eddy simulations supplied with the one-equation localized dynamic kinetic energy-based model are successfully performed at moderately high Reynolds number. The present study demonstrates that the proposed variable thresholding methodology for wavelet-based modelling of turbulent flows around solid obstacles is feasible, accurate and efficient.

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Mansuri, Arif Ali, Aditi Singh, Manas Singh, and Ujjawal Goel. "AI Integrated Vehicular Robot Having Accident Prevention System from Static Obstacles." International Journal for Research in Applied Science and Engineering Technology 10, no. 5 (May 31, 2022): 2227–32. http://dx.doi.org/10.22214/ijraset.2022.42701.

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Abstract: Transportation plays an increasingly vital role in our lives these days, and its advancement has made our lives much easier. However, in recent years, we have seen people attempt to circumvent traffic signals, resulting in devastating road accidents and fatalities. Dozing and alcohol use produce intrusiveness, necessitating immediate action before a mistake occurs. In this study, a prototype is created utilising an Arduino Uno, a camera, and ultrasonic sensors for monitoring, with the goal of preventing accidents and providing drivers with safety aid.[10]. For recognising the front side and averting an accident, the system uses Internet of Things, machine learning, and artificial intelligence (AI) in automobiles. Several lives have been saved by vehicles stopping whenever they perceive a red light or a stationary obstruction in front of them, as well as warning the driver via a sound system. The device has been put to the test, and the findings demonstrate that it is efficient and effective. Keywords: Arduino Uno, Camera, Machine Learning, Artificial Intelligence, Ultrasonic sensor

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Guio, P., and H. L. Pécseli. "Phase space structures generated by absorbing obstacles in streaming plasmas." Annales Geophysicae 23, no. 3 (March 30, 2005): 853–65. http://dx.doi.org/10.5194/angeo-23-853-2005.

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Abstract. The dynamic behavior of a collisionless plasma flowing around an obstacle is investigated by numerical methods. In the present studies, the obstacle is formed by an absorbing cylinder, and a 2-D electrostatic particle-in-cell simulation is used to study the flow characteristics, with extensions to a fully 3-D generalization of the problem demonstrated as well. The formation of irregular filamented density depletions, oblique to the flow, is observed. The structures form behind the obstacle, in a region with a strong velocity shear, but also other instability mechanisms can be identified. The dynamics of these structures is highly dependent on the physical parameters of the plasma, and they can either be quasi-stationary or undergo a dynamic evolution. The structures are found to be associated with phase-space vortices, observed especially in the phase space spanned by the velocity direction perpendicular to the flow and the spatial coordinate in the same direction. The bias of the obstacle with respect to the plasma potential is found to be an important parameter for the dynamics of the structures, but seemingly not for their formation as such. The results can be of interest in the interpretation of structures in space plasmas as observed by instrumented spacecrafts.

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Journal articles on the topic 'Stationary obstacles'

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