Modélisation et commande d’un manipulateur mobile à roues

Abstract

This dissertation addresses the problems of modeling, motion planning and tracking control design for Wheeled Mobile Manipulators (WMMs). WMMs are typical examples of nonlinear systems with both holonomic and non-holonomic constraints with highly coupled dynamics. The proposed control approach is based on two main concepts: (i) the flatness property of WMM and (ii) the Sliding Mode Control (SMC) theory. Using the fact that the WMM is differentially flat system, the motion control design is relatively simplified by defining the desired motions of the robot in the flat output space of the system. The accurate and the robust trajectories tracking are provided firstly, by imposing the sliding manifold from the flat output space of the system. Secondly, a State-Dependent Gain discontinuous control law is introduced to drive to zero in finite time such sliding manifold, despite model uncertainties and external disturbances. The system stability is proven using the Lyapunov theory. Compared with classical Feedback control algorithms, the proposed controller is applied to the mobile robot and then to the mobile manipulator compound of 2 dof robot manipulator mounted on a mobile platform. Simulation and practical tests are presented to illustrate the performances of the proposed approach in the presence of unknown external disturbances.