scholarly journals Fuzzy Risk Evaluation and Collision Avoidance Control of Unmanned Surface Vessels

2021 ◽  
Vol 11 (14) ◽  
pp. 6338
Author(s):  
Yung-Yue Chen ◽  
Ming-Zhen Ellis-Tiew ◽  
Wei-Chun Chen ◽  
Chong-Ze Wang
Keyword(s):  
Optimal Control ◽  
Collision Avoidance ◽  
Trajectory Tracking ◽  
Nonlinear Optimal Control ◽  
Control Law ◽  
Risk Indicator ◽  
Collision Avoidance Control ◽  
Surface Vessels ◽  
Tracking Ability ◽  
Avoidance Control

In this investigation, a smart collision avoidance control design, which integrates a collision avoidance navigation and a nonlinear optimal control method, is developed for unmanned surface vessels (USVs) under randomly incoming ships and fixed obstacle encounter situations. For achieving collision avoidance navigation, a fuzzy collision risk indicator and a fuzzy collision avoidance acting timing indicator are developed. These two risk indicators can offer effective pre-alarms for making the controlled USVs to perform dodge actions in time when obstacles appear. As to nonlinear optimal control law, it provides a precise trajectory tracking ability for the controlled USVs to follow a collision avoidance trajectory, which is generated via a smart collision avoidance trajectory generator. Finally, a power allocation method is used to transform the desired control law into available actuator outputs to guide the USVs to follow a desired collision avoidance trajectory. From simulation results, the proposed collision avoidance strategy reveals a promising collision avoidance performance and an accurate trajectory tracking ability with respect to fixed objects and randomly moving ships under the effect of environmental ocean disturbances.

scholarly journals Nonlinear Optimal Control Law of Autonomous Unmanned Surface Vessels

2020 ◽  
Vol 10 (5) ◽  
pp. 1686
Author(s):  
Yung-Yue Chen ◽  
Chun-Yen Lee ◽  
Shao-Han Tseng ◽  
Wei-Min Hu
Keyword(s):  
Optimal Control ◽  
Closed Form ◽  
Closed Form Solution ◽  
Nonlinear Optimal Control ◽  
Form Solution ◽  
Control Law ◽  
Tracking Problem ◽  
Optimal Tracking ◽  
Surface Vessels ◽  
Marine Surface

For energy conservation, nonlinear-optimal-control-law design for marine surface vessels has become a crucial ocean technology for the current ship industry. A well-controlled marine surface vessel with optimal properties must possess accurate tracking capability for accomplishing sailing missions. To achieve this design target, a closed-form nonlinear optimal control law for the trajectory- and waypoint-tracking problem of autonomous marine surface vessels (AUSVs) is presented in this investigation. The proposed approach, based on the optimal control concept, can be effectively applied to generate control commands on marine surface vessels operating in sailing scenarios where ocean environmental disturbances are random and unpredictable. In general, it is difficult to directly obtain a closed-form solution from this optimal tracking problem. Fortunately, by having the adequate choice of state-variable transformation, the nonlinear optimal tracking problem of autonomous marine surface vessels can be converted into a solvable nonlinear time-varying differential equation. The solved closed-form solution can also be acquired with an easy-to-implement control structure for energy-saving purposes.

scholarly journals Research on Flight Collision Avoidance Control on The Sun-Earth Libration Points Based on Barrier Theory

2018 ◽  
Vol 36 (2) ◽  
pp. 252-257
Author(s):  
Ke Zhang ◽  
Zhenqi He ◽  
Meibo Lü ◽  
Jingyu Wang
Keyword(s):  
Optimal Control ◽  
Formation Flight ◽  
Control Law ◽  
The Sun ◽  
Hamilton Function ◽  
Spacecraft Formation ◽  
Collision Avoidance Control ◽  
Avoidance Control ◽  
Simulation Results ◽  
Perturbation Effect

In the spacecraft formation task, a spacecraft failure or formation of the mission to change the need for reconstruction of the formation. In the process of reconstruction, how to carry out spacecraft anti-collision has been widespread concern. In this paper, barrier theory is adopted. By establishing Hamilton function, the optimal control law is obtained. According to the theory of barrier construction, the corresponding barrier trajectory is constructed. Then, the barrier is divided into collision area and non-collision area, so as to realize the formation flight anti-collision design. The simulation results show that the method can avoid the perturbation effect and has a certain theoretical value for the anti-collision between the spacecrafts during the formation process.

scholarly journals Adaptive Obstacle Avoidance for a Class of Collaborative Robots

Machines ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 113
Author(s):  
Giorgia Chiriatti ◽  
Giacomo Palmieri ◽  
Cecilia Scoccia ◽  
Matteo Claudio Palpacelli ◽  
Massimo Callegari
Keyword(s):  
Collision Avoidance ◽  
Computational Effort ◽  
Control Law ◽  
Cylindrical Shape ◽  
Control Techniques ◽  
Planar Manipulators ◽  
Collision Avoidance Control ◽  
Avoidance Control ◽  
Human Robot Collaboration ◽  
Operator Safety

In a human–robot collaboration scenario, operator safety is the main problem and must be guaranteed under all conditions. Collision avoidance control techniques are essential to improve operator safety and robot flexibility by preventing impacts that can occur between the robot and humans or with objects inadvertently left within the operational workspace. On this basis, collision avoidance algorithms for moving obstacles are presented in this paper: inspired by algorithms already developed by the authors for planar manipulators, algorithms are adapted for the 6-DOF collaborative manipulators by Universal Robots, and some new contributions are introduced. First, in this work, the safety region wrapping each link of the manipulator assumes a cylindrical shape whose radius varies according to the speed of the colliding obstacle, so that dynamical obstacles are avoided with increased safety regions in order to reduce the risk, whereas fixed obstacles allow us to use smaller safety regions, facilitating the motion of the robot. In addition, three different modalities for the collision avoidance control law are proposed, which differ in the type of motion admitted for the perturbation of the end-effector: the general mode allows for a 6-DOF perturbation, but restrictions can be imposed on the orientation part of the avoidance motion using 4-DOF or 3-DOF modes. In order to demonstrate the effectiveness of the control strategy, simulations with dynamic and fixed obstacles are presented and discussed. Simulations are also used to estimate the required computational effort in order to verify the transferability to a real system.

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