This paper studies the optimal trajectory optimization of a space robot for maintenance operations. A new trajectory planning algorithm is proposed to solve the problems of low maintenance efficiency and poor stationarity of space robots on-orbit. Firstly, considering the constraint conditions such as the speed, acceleration and secondary acceleration of each joint of the space robots, the cubic spline curve is used to plan the trajectory of the space robots in the joint space. Then, a comprehensive optimal planning model for time-jerk is established, and the optimal problem of space maintenance efficiency and stationarity is described as a nonlinear constrained optimization problem. Finally, a hybrid optimization algorithm is proposed to solve the trajectory optimization problem of space robots by combining genetic algorithm and particle swarm optimization method. The simulation results show that, compared with several classic optimization algorithms, the proposed hybrid optimization algorithm can obtain a better maintenance trajectory of the space robots under the constraints, which solves the low efficiency and poor stability of the space robots on-orbit maintenance problem.
This paper studies the calibration of industrial robots. Aiming at the problems of cumbersome industrial robot modeling and poor calibration effects, this paper proposes a new calibration method for determining the DH frame and DH parameters of industrial robots by measuring first and modeling afterwards. Firstly, the theory of Fixed Axis-Invariant is proposed, the Axis-Invariant is determined based on dual-vectors, and the origin of Fixed Axis-Invariant is determined by intersection obtained through the projection from one measuring point to the Axis-Invariant. Secondly, a method for solving the D-H frame and D-H parameters of industrial robots based on Fixed Axis-Invariant is proposed. Then, combined with laser tracker and industrial robot control software for secondary development, the developed software can be used to automatically measure and obtain the D-H frame and D-H parameters of industrial robot. Finally, compared with other calibration methods, it can be seen that the calibration method based on Fixed Axis-Invariant proposed in this paper can obtain better results. It can improve the absolute positioning accuracy of industrial robots to less than 0.28 mm, which can solve the problems of cumbersome industrial robot modeling and poor calibration effects.
This paper investigates the on-orbit maintenance task planning of large-scale space solar power station. The research is of great significance for the normal operation of large-scale space equipment. Space robots are very maneuverable, which makes space maintenance possible. A new task planning algorithm is proposed for the on-orbit maintenance of space robots. Firstly, based on the discretization method, the modified clustering method is used to cluster the maintenance area of large-scale space solar power stations. Secondly, the hierarchical structure principle is used to assign tasks to the space robot, the inner layer plans the shortest path within the cluster set, and the outer layer plans the optimal path between the cluster sets. Finally, based on the optimal path of the outer layer of the maintenance task, a hybrid optimization algorithm based on tabu algorithm and modified ant colony algorithm is proposed. The algorithm can meet the space machine task allocation requirements and analyze the maintenance path under certain energy conditions. The simulation results show that the proposed algorithm can effectively solve the optimal problem of space robot mission planning under resource constraints. INDEX TERMS Space robot, task clustering, hybrid optimization algorithm, task planning.
This paper studies the Cartesian point-to-point optimal trajectory planning for space robots oriented to space maintenance operations. Aiming at the problems of poor stability, large base disturbance, and large joint variation in the motion planning of point-to-point maintenance in space, a planning method is proposed to minimize the base disturbance and the total joint angle variation under the jerk constraint on the premise of ensuring the accuracy of the end pose. First, the attitude of the space robot is described by the unit quaternion, and the velocity relationship between the joint angle, the end effector, and the base posture is introduced. Then, the joint trajectories were parameterized by a fifth degree polynomial, and a trajectory planning model with the minimum perturbation of the base and the minimum variation of the joint of the manipulator was established under the condition that the end effector satisfied the pose and the jerk constraint. Finally, a multi-objective optimization algorithm is proposed to deal with the trajectory optimization problem under nonlinear constraints. The simulation results show that the proposed trajectory planning method can optimize the base attitude and joint angle of the space manipulator under the premise of the optimal trajectory and stability of the terminal execution tool, which ensures the stability of the space robot’s on-orbit service and reduces the energy consumption.
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