Asymmetric Barrier Function-based Adaptive Control of a Four-Wheel-Steering Mobile Robot

Four-wheel-steering mobile robots (FMR) are extensively-adopted for manufacturing applications. However, the robust trajectory tracking of FMR is hard to achieve due to the complex disturbances. For addressing the challenge, an asymmetric barrier function-based adaptive control (ABFAC) method is presented here for obtaining a robust direct yaw moment control scheme for the FMR. The praiseworthy features of the proposed ABFAC method are twofold: (a) It does not need the information concerning the upper boundary information of the unknown uncertainties; (b) By introducing the barrier function, the output signals are guaranteed to be within the desired neighborhood since the sliding mode gains will grow once the disturbance derivatives increase. In this context, the proposed ABFAC method drives the resultant trajectory tracks the variation tendency of the disturbances, guaranteeing robust closed-loop responses. The global stability of the FMR can be ensured theoretically. Finally, experimental results of real-time FMR are provided to validate the applicability of our ABFAC method.