Hybrid super‐twisting fractional‐order terminal sliding mode control for rolling spherical robot

Abstract

Abstract The unmodeled parameters, uncertainties, chattering, and disturbances can be serious problems for a controller. These issues decrease the performance of the controller and make it difficult to have a satisfactory movement path as well. This paper presents a novel hybrid super‐twisting fractional‐order terminal sliding mode controller (HSTFOTSMC) for a rolling spherical robot (RSR) considering bounded model uncertainties for robot dynamics in presence of external disturbances and noise. The controller is based on a new adaptive fractional‐order terminal sliding surface. The stability of the proposed controller is proved by the Lyapunov theory, and then, it is tuned by a novel extended grey wolf optimizing (EGWO) algorithm to adjust the controller parameters, and assure to achieve the precise robot performance. The results of the optimized controller (EGWO‐HSTFOTSMC) are compared with the typical sliding mode controller (SMC), fractional‐order terminal sliding mode controller (FOTSMC), and super‐twisting fractional‐order terminal sliding mode controller (STFOTSMC), which demonstrate the effectiveness of the controller scheme. The controller implementation can potently eliminate the impacts of disturbances, noise, and uncertainties; meanwhile, it decreases the tracking error and increases the convergence speed of robot responses.