Modeling and piecewise integral terminal sliding mode control for the lower hook mechanism of fishing net weaving machine

The lower hook mechanism has the characteristics of long motion path, high moving speed and high external disturbance, significantly impacting the weaving efficiency of the fishing net weaving machine. The multi-motor-based lower hook mechanism exhibits higher moving speed and lesser cam wear compared with the traditional lower hook mechanism, but it requires a high-precision and high-robust control system. In this study, we established a dynamic model for the multi-motor lower hook mechanism using the Lagrange equation. Based on this model, we developed a control system using linear extended state observer (LESO) and piecewise integral terminal sliding mode controller (PITSMC). By introducing a piecewise integral sliding surface, PISMC solved the slow convergence issue of linear sliding surfaces and the singularity problem of integral terminal sliding surfaces. Simulation results for the multi-motor-based lower hook mechanism demonstrate that the proposed PISMC outperforms the nonsingular terminal sliding mode controller and the conventional integral sliding mode controller in terms of control precision and disturbance rejection capability.