State-Dependent Riccati Equation Control for Motion Planning of SpaceManipulator Carrying a Heavy Payload

Abstract

In this paper, a nonlinear optimal control approach is proposed to plan the motion of a redundant free-floating space manipulator (FFSM) when carrying a heavy payload. Optimal joint trajectories are determined to track a desired end-effector path, for which limitations of the manipulator's load-carrying capacity and tracking accuracy are simultaneously considered. In this method, FFSM is described as a nonlinear system using the dynamics equation. The integrated performance indicator is proposed as the cost function, which includes tracking error punishment of the end- effector, joint-torques optimization, total energy improvement and instability avoidance of the base. Then the state- dependent Riccati equation (SDRE) is established and solved by Taylor series approximation method. The motion planning algorithm is presented, subject to multi-constraints. Simulations are performed for a 7-DOF space manipulator and the results are discussed to illustrate the effectiveness of the proposed approach.