Time delay control of hydraulic manipulators with continuous nonsingular terminal sliding mode

For the position tracking control of hydraulic manipulators, a novel method of time delay control (TDC) with continuous nonsingular terminal sliding mode (CNTSM) was proposed in this work. Complex dynamics of the hydraulic manipulator is approximately canceled by time delay estimation (TDE), which means the proposed method is model-free and no prior knowledge of the dynamics is required. Moreover, the CNTSM term with a fast-TSM-type reaching law ensures fast convergence and high-precision tracking control performance under heavy lumped uncertainties. Despite its considerable robustness against lumped uncertainties, the proposed control scheme is continuous and chattering-free and no pressure sensors are required in practical applications. Theoretical analysis and experimental results show that faster and higher-precision position tracking performance is achieved compared with the traditional CNTSM-based TDC method using boundary layers.