Leader-follower formation tracking for differential-drive wheeled mobile robots with uncertainties and disturbances based on immune fuzzy quasi-sliding mode control

Mobile robotics has drawn attention of researchers due to its variety of applications. In this paper, for nonholonomic differential-drive wheeled mobile robots with an embedded proportional-derivative dynamic controller, a robust kinematic controller based on sliding mode theory is designed considering the trajectory tracking problem and its extension to the formation control by multiple robots using the leader-follower separation-bearing strategy. A classical sliding mode control has some drawbacks such as the chattering phenomenon and the requirement of a priori knowledge of the boundaries of disturbances for its design. Thus, this paper aims to propose the design of an approach inspired by an immune regulation mechanism, also using a simple fuzzy boundary layer method, in replacement of the discontinuous portion of the controller, adjusting its gains with no need to know the boundaries of the uncertainties and disturbances as well as suppressing the chattering. The effectiveness of the proposed controller is shown by simulation results, and its stability is proved by the Lyapunov theorem.