Whole-body control of a mobile manipulator using feedback linearization and dual quaternion algebra

This master thesis presents the whole-body control of a nonholonomic mobile manipulator using feedback linearization and dual quaternion algebra. The controller, whose reference is a unit dual quaternion representing the desired end-effector pose, acts as a dynamictrajectory generator for the end-effector, and input signals for both nonholonomic mobile base and manipulator arm are generated by using the pseudoinverse of the whole-body Jacobian matrix. In order to deal with the nonholonomic constraints, the input signal to the mobile base generated by the whole-body motion control is properly remapped toensure feasibility. Joint constraints, which are present in the real platform, are treated by means of constraints in the Jacobian matrix. The Lyapunov stability for the closed-loop system is presented, utilizing Lyapunov's Direct Method and Matrosov's theorem, and experimental results on a real platform are performed in order to compare the proposed scheme to a traditional classic whole-body linear kinematic controller. The results show that, for similar convergence rate, the nonlinear controller is capable of generating smoother movements while having lower control effort than the linear controller.