Observer-Based Trajectory Tracking Control of Nonholonomic Wheeled Mobile Robots

This brief addresses the trajectory tracking problem for nonholonomic wheeled mobile robots (WMRs) without attitude measurement. Using only position and velocity information, we propose a kinematic control law combined with an exponential attitude observer, steering the robot to track a time-varying reference trajectory from any initial states. The effectiveness of the proposed observer-based control law relies on maintaining the linear velocity being greater than zero. Lyapunov’s theory is employed to prove the stability of a closed-loop system. Experiments performed on a real robot illustrate the proposed control scheme.

I. Introduction

The wheeled mobile robots (WMRs) in the forms of unicycles have been widely studied in the past decades owing to interesting nonlinearities brought by model underactuation and nonholonomic constraint [1], [2], and due to potential applications in areas such as autonomous vehicles and robotic transportation [3].