| The space manipulator on-orbit platform has high use value and has a wide range of application scenarios.This topic has carried out research and analysis on the two actual needs of the space manipulator on-orbit platform.In order to improve the comprehensive performance of the trajectory executed by the space manipulator,this paper studies the multi-target trajectory planning of the manipulator in the joint space.In this paper,firstly,the criterion function of five relatively important performance indicators,such as time optimal,energy consumption optimal,smoothness optimal,singularity avoidance optimal,and base disturbance optimal is established,and then the four-degree polynomial curve is used to construct the criterion function.Time parameterized trajectory,from which the necessary parameters such as optimization items and constraint items required by the optimization model are obtained.After that,based on the single-objective particle swarm optimization algorithm and the multi-objective particle swarm optimization algorithm,this paper has completed the optimization of any of the above goals and the comprehensive optimization of any combination of goals.The combination optimization can output the Pareto optimal solution set and increase the flexibility of the multi-target trajectory planning.In addition,in order to expand the continuous path planning ability of space manipulators in complex environments,this paper also studies the obstacle avoidance trajectory planning of manipulators in Cartesian space.This paper decomposes the problem into two major issues: obstacle avoidance trajectory planning at the end of the manipulator and obstacle avoidance trajectory planning for the manipulator body.In response to problem 1,this paper introduces the Kinodynamic RRTstar algorithm,which regards the end of the manipulator as a moving mass point,and uses the best feasible connection between the sampling nodes to replace the straight line connection of the traditional RRT algorithm.This method can effectively solve the the problem of not having both safety and smoothness.In order to improve the efficiency of the algorithm,this paper also derives and establishes an analytical solution of the best feasible connection.To solve the second problem,this paper uses the gradient projection method based on singular robustness inverse to solve the problem.It uses the singular robustness inverse to solve the stability problem of the manipulator and uses the gradient projection method to reasonably apply the seven degrees of freedom to realizes the body avoidance during the inverse solution process.In this process,this paper proposes a self-moving obstacle avoidance method based on escape velocity to improve the difficulty of derivation and large amount of calculation when the traditional solution directly solves the gradient.At the same time,this paper also designs optimization methods such as optimal damping algorithm,closed-loop correction algorithm and speed weight distribution algorithm,which are used to solve the main task tracking accuracy problem and the joint angular velocity overrun problem.All of the optimization methods achieves ideal results.Finally,this paper focuses on the comprehensive simulation verification of the Cartesian space obstacle avoidance trajectory planning of the manipulator.Based on the simulation results of the self-developed manipulator in the laboratory,under the premise of ensuring that the joint speed does not exceed the limit and at a discrete frequency of50 hz,the maximum position error of the end of the robotic arm is 0.0020 m,the maximum attitude error is 0.0009 rad,and the distance to the internal obstacle is always near the warning threshold 0.2000 m.In addition,it is worth noting that although the research object of this article is a spatially redundant 7-DOF manipulator,the related theoretical results can be transferred to other redundant 7-DOF manipulators.The simulation experiment on Baxter’s manipulator in this article has proved this feature. |
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