Simultaneous tracking and stabilization of mobile robots without velocity measurements

We present a time-varying global output-feedback controller that solves both tracking and stabilization for mobile robots simultaneously at the torque level. A coordinate transformation is first derived to cancel the velocity quadratic terms. A passive observer is then designed to globally exponentially estimate the unmeasured velocities. The controller synthesis is based on Lyapunov´s direct method and backstepping technique. Simulations illustrate the effectiveness of the proposed controller.