Simultaneous tracking and stabilization of mobile robots without velocity measurement

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.