Hierarchical Terminal Sliding Mode Control for Underactuated Space Robots

In this paper, the position control problem of the underactuated space robot is addressed, and a new sliding mode control scheme is proposed. The underactuated system was hierarchically divided into active subsystem and passive subsystem, and combining with the subsystems’ sliding planes constructed by terminal sliding mode method a new global sliding plane is constructed, then using the Lyapunov function and exponential approximation law with saturation function the control law is derived. The control system is designed and simulated by proposed algorithm for two degrees of freedom underactuated space robot, and the simulation results show that the proposed algorithm not only can effectively implement the position control of the active and passive joints, but also can make the convergent rate controllable.