Adaptive Control of Electrically Driven Space Robots Based on Virtual Decomposition

Abstract

A systematic approach named virtual decomposition is presented for adaptive control of space robots incorporating motor dynamics. Virtual decomposition imposes a modular structure on both control design and stability analysis. In the control design, the control problem of the complete system is converted into the control problem of each subsystem (rigid body or joint ), whereas the nonholonomic constraints are represented by a set of constraint equations imposed on the required acceleration. Two alternative joint control modes, namely, motor current control and motor voltage control, are considered. Parameter adaptation can be carried out independently for each subsystem, which makes decentralized parameter adaptation possible. In the stability analysis, each subsystem (rigid body or joint ) is assigned a nonnegative accompanying function. The dynamic interaction between every two physically connected subsystems is completely represented by a virtual power e ow through their connection. The system Lyapunov function is formed by merely adding all nonnegative accompanying functions assigned to the subsystems. Lyapunov stability is ensured and computer simulations are conducted. The proposed approach is a general one that can be extended to treat a variety of space robotic systems due to its modular structure.