Decentralized Control of a Slow Moving Mobile Manipulator

In this paper, motion control of slow moving Mobile Manipulators (MM) using decentralized control method is discussed. Slow moving robots are used for applications which require more accuracy, robustness, and reliability so that they can be used in hazardous environments which are unsafe for humans. For proper control, these manipulators have to track the reference trajectory with a constant heading angle and velocity while avoiding the manipulator singularities. In this paper, the movable-platform and the manipulator are considered as two different subsystems and separate kinematic models are developed. By introducing the platform mobility, the singularities of the manipulator can be avoided by keeping its leading configuration in the tracking process, and thus solves the problem of redundancy of the system. Two separate controllers are designed for the movable-platform and the manipulator, and these two controllers are related using the velocities between the two subsystems. Lyapunov approach is used to develop the control law which ensures the asymptotical stability of the system. Effectiveness of the proposed controllers is evident from the simulation results. The analysis of manipulability measure indicates that the MM is capable of doing the task without singularities.