Vibration-suppressed trajectory planning for flexible space manipulators during on-orbit operations

Space manipulators are frequently employed to efficiently and flexibly perform complex tasks in orbit. A multi-degree-of-freedom (DOF) manipulator in space typically features two long links, making vibration suppression particularly crucial due to the inherent flexibility of these links. However, current research predominantly addresses trajectory planning for planar manipulators in joint space and seldom explores multi-DOF manipulators in 3D Cartesian space when considering link flexibility due to the model complexity and high computational demands. This paper introduces a Cartesian-space trajectory optimization method for multi-DOF space manipulators, with a focus on vibration suppression. First, a flexible link model is developed using the assumed mode method, and the system’s flexible vibration model is further established using the Lagrangian method. Next, an improved particle swarm optimization algorithm is proposed, incorporating crossover and mutation techniques. The proposed algorithm optimizes the time allocation of multiple waypoints and generates Cartesian trajectories using the minimum-jerk method. The cooperation between the optimizer and the trajectory generator ultimately determines the optimal trajectory. Finally, numerical simulations and physical experiments are conducted to validate the effectiveness of the trajectory optimization method. The results demonstrate that the proposed method effectively reduces trajectory tracking errors caused by link flexibility during motion and suppresses residual vibrations post-movement.