A New Electro-hydraulic system for controlling the rolling mill operation

Rolling mill automation systems have played an important role in the past sixty years when the servo system was introduced to the metal forming industry. With the rapid development of the measurement devices, the computers, and modeling techniques, rolling mill automation has made significant progress in those years.

To control the rolling mill operation, we'll introduce a new and simple electro-hydraulic system for you. This proposed system featured as less number of components, compactness, and it also eases of installation as well as maintenance. In terms of exhibits, it can exhibit the same rolling mill control performance as obtained as well, when equipped with the conventional control systems. The system simulation is experimentally validated, presented, discussed as well.

Symbolic representation of the hydraulic control system

Metal forming and rolling mills are nowadays highly dependent, in the intermediate stages of the rolling mills, both of rolling speed and rolling load must be controlled. For control the rolling speed and rolling force, the hydraulic system contains a variable displacement pump and a pressure compensator, both of them controlled electrically. The first one controls the rolling speed, while the other one controls the rolling force. Double negative control schemes consist of each of them. And the proposed system has been simulated, realized and tested experimentally. It revealed the features of the rolling mill as following.

schematic of the pressure compensator

First, the pump control system makes the rolling speed constant despite the changes in the rolling torque with the assumption of negligible internal leakage of the pump and the hydraulic motor.

Second, the rolling load is kept constant whenever the pressure difference across the compensator is more than 4% of the upstream pressure.

Third, rolling load experiences shocks at the transient periods of the stepwise change of the rolling torque, and results that the harmonic change of the, is compensated and lead to a constant rolling load as the reference value.

From all the above, we have a conclusion that both rolling speed and rolling load reference values are assumed constants. 

pump swash plate attached to the pump control unit