Fixed-Time Stabilization for Nonholonomic Wheeled Mobile Robots by Differential Flatness and Active Disturbance Rejection Control

In this paper, the stabilization problem is concerned for a class of nonholonomic wheel mobile robots (WMRs). The main aim is to achieve control performance in sense of fixed-time stability in presence of uncertainties. Firstly, by virtue of differential flatness theory, the underactuated system is transformed to a dual-input-dual-output one. Taking advantages of tracking differentiator (TD), the moving trajectory is reasonably planned from initial to stabilization points. Secondly, considering lumped unmodeled dynamics and external disturbances, a reduced-order fixed-time extended state observer (FxTESO) is introduced for uncertainty estimation. Then, a FxTESO-based active disturbance rejection control law is developed for dynamic model, in which disturbance compensation is presented to attenuate uncertainty influence in real time. Finally, the effectiveness and advantages of the proposed methods are illustrated by numerical example. Consequently, not only the stabilization purpose, but also the transient performance can be desirably achieved for nonholonomic WMRs subject to uncertianties.