An Improved Adaptive Sliding Mode Control Based on Time-Delay Control for Robot Manipulators

This article proposes a new adaptive sliding mode control (ASMC) scheme for robot manipulators not only by designing a sliding variable and an adaptive law but also by compensating a time-delay estimation (TDE) error induced by time-delay control (TDC). Based on the operating cycle, because TDC utilizes the previous angular acceleration and input torque for the estimation of the dynamics of the manipulators, TDC produces an inevitable TDE error and this article compensates the present TDE error by using the previous TDE error. For the ASMC, this article constructs the sliding variable by additionally utilizing the previous error and its derivative. Also, this article proposes an adaptive law, which guarantees the positive condition of the adaptive parameter, by using the current adaptive parameter value and the sampling period. For the stability analysis, this article shows uniformly ultimately bounded stability of the sliding variable for the manipulators controlled by the proposed ASMC scheme. The simulation and experimental results present the effectiveness of the proposed control schemes.