Fixed-Time Tracking Control of Uncertain Nonholonomic Mobile Robots without Velocity Measurements

This paper studies the fixed-time tracking control problem of uncertain nonholonomic mobile robots without velocity measurements. Firstly, the tracking error system is decomposed into a second-order subsystem and a third-order subsystem, respectively. Secondly, a novel auxiliary variable is introduced, with the help of which new fixed-time extended-state observers are designed to achieve exact estimation of the velocities as well as the disturbances. Then, based on the proposed extended-state observers, a fixed-time output feedback tracking controller is proposed for the mobile robots, which can guarantee that the tracking errors can converge to zero in fixed time independent of system initial conditions even in the presence of disturbances and unmeasurable velocities. Finally, simulation results illustrate the advantages of the proposed controller.