Abstract: Aiming at the problem of low tracking accuracy in trajectory tracking control of 5-degree of freedom (DOF) parallel mechanisms caused by model uncertainties, external disturbances, and input saturation, we proposed a discrete integral sliding mode control algorithm with time-varying disturbance compensation considering input saturation. Firstly, to address the problem of input saturation,  while considering the limitations of  input assignment and input rate of change, we designed a discrete saturation compensation auxiliary system to  eliminate the input saturation characteristics. Secondly, we designed a time-varying disturbance compensation discrete integral sliding mode controller to  achieve real-time compensation for lumped disturbances, thereby reducing system steady-state error while suppressing chattering. Finally, through simulation experiments, a comparative analysis was conducted between the proposed method and the disturbance compensation discrete sliding mode control algorithm, 
considering both with and without input saturation. The experimental results show that the proposed algorithm outperforms the comparative algorithms in terms of control accuracy and saturation constraints, and can effectively achieve high-precision trajectory tracking control of parallel mechanisms considering both lumped disturbances and input saturation, with high engineering application value.

Key words: parallel mechanism, input saturation, anti-saturation auxiliary system, discrete integral sliding mode control, disturbance compensation approaching rate