Almost smooth time-invariant control of planar space multibody systems

We address the configuration control problem in free-flying planar space robots. Such multibody systems are nonholonomic in nature due to conservation of angular momentum. We develop an almost smooth and time-invariant control strategy that guarantees Lyapunov stability and convergence of the states to the desired configuration. The controller suffers from a slow rate of convergence when the desired configuration is close to the locus of dynamic singularities. This problem can be remedied by modifying the controller, and two modified controllers are proposed in this paper. The stability of the desired configuration and convergence of closed loop system trajectories are mathematically established for the original controller. Simulations of the closed loop system have been carried out with the original controller and the modified controllers.