Event-triggered sliding mode kinematic control for a four-wheeled steerable mobile robot using barrier-function-based variable gain

Limited communication resources pose challenges to the stable control of uncertain mobile robots, especially for a four-wheeled steerable mobile robot (FSMR) with multiple sensors and actuators. This paper proposes an event-triggered sliding mode kinematic control scheme using barrier-function (BF)-based variable gain for FSMR under kinematic uncertainties and communication resources constraints. First, a novel positive-defined adjustable BF (PABF) is designed, confining the sliding variables within the predefined barrier. The given BF accommodates the aperiodic sampling, eliminating the necessity of small sampling intervals in the existing sliding mode. Then, a mixed event trigger mechanism includes the guarantees of stability and boundness of sliding variable errors, which reduces the frequency of control updates and serves as a critical element for ensuring the existence of a practical sliding mode (PSM). The preset bandwidth of PSM can be adjusted by the predefined barrier. Comparative analysis verify that the PABF enlarges the state-barrier margin, removing the need for small sampling steps. Finally, simulations and experiments demonstrate the proposed method achieves the predefined PSM band with smaller state errors. The total communication resources usage ratio is less than the compared method through a reduced number of events.