Hydraulic servo system of bilateral rolling shears for thick and wide plate

The hydraulic system of a bilateral rolling shear for a thick and wide plate is a nonlinear system. The sudden loading on the hydraulic cylinders caused by the collision between the steel plate and the upper blade is huge at the beginning. The system response may be unable to meet the requirements of actual production, thereby resulting in low cutting quality or failure to shear the steel plate. To solve these issues, we propose a preloaded hydraulic system in which some amount of pressure is preloaded in the rodless chamber before the hydraulic cylinders contact the load. Then, the pressure held in the rodless chamber of the hydraulic cylinder is immediately released as the load applied, compensating for the inadequacies in the response time of the system and providing a sufficiently large supplementary flow to the hydraulic cylinder. A cascade controller based on a disturbance observer is designed, which includes a position outer loop and a pressure inner loop. The new electrohydraulic servo system improves the shearing precision and power of the bilateral rolling shears and increases the load tolerance of the system, thereby improving the system stability.