Velocity Estimation for Mobile Robots Using Caster Odometer and Nonlinear Observer

Abstract

In this paper, a novel nonlinear observer for caster wheel odometers is proposed which estimates the translational and the rotational velocities of the mobile robots. The proposed method is shown to be applicable to generic mechanism of caster wheel odometers. In addition, for the extended linearized system with respect to the estimation error, exponential convergence of the estimation error is proved, which guarantees that the proposed observer is robust against measurement noise and unmodeled dynamics. The advantage over the conventional approximated differentiator is shown in numerical simulation, which indicates that the estimation error is much smaller and less sensitive to both the external disturbance and the motion of the vehicle. Finally, an experiment on velocity tracking control is conducted for a leg / wheel omnidirectional mobile robot to show that the tracking performance can be obviously improved by the proposed nonlinear observer.