Dynamic Simulation Of Hydraulic Servo-Control System Of Ring Rolling Mill

Ring Rolling Mill is a kind of machine processing ring shape workpiece. With the guide roll, local plastic deformation is taken place on the workpiece, and this makes the workpiece thinner and the diameter of it bigger. Finally the required shape is got. Ring Rolling is widely applied in areas of machine, automotive, metallurgy, ships and aviation, etc. And so as the Ring Rolling Mill.The main work parts of Ring Rolling Mill are the guide roll and its feed system, mandrel roll, detectable roll, etc. When the machine is working, the ring shape workpiece is on the mandrel roll, and the guide roll is rotating and moving to the mandrel roll with the help of feed system, so as to make the workpiece thinner and its diameter bigger. When the shape of the workpiece is fit to the set value of the detectable roll, the feed system stops work and the process is finished.It is seen from this that the precision of the feed system is one of the most important factors which will influence the precision of the workpiece shape. The feed system's power of old Ring Rolling Mill is pneumatic cylinder and the both the Sensitiveness-Responsiveness and the precision is not so good. While the hydraulic servo-control system is used to control the feed system, not only the position and velocity precision is improved, but also the value of them can be controlled effectively. And because of the hydraulic servo-control system, the Ring Rolling Mill machine can be connected to computer to make the processing automation control, thus the processing time is shorter and the labor intensity was lessened, finally the production cost dropped down and the precision of workpiece is improved.In this paper, the software ADAMS and MATLAB is used to study the hydraulic servo-control system of Ring Rolling mill. The main contents and results are as follows:1) The mathematic model is built and the open bode diagram and step response diagram are obtained through programming in the MATLAB work space. From the diagrams it is known that the stability and overshoot of the hydraulic control system are not reasonable, so the system correction is required and finally the dynamic response of the system is achieved the requirement.2) The virtual prototyping of hydraulic model is built in the ADAMS software and adjustment is applied to make the system meet the work condition. The curves of cylinder's position, velocity, acceleration and pressure and the inner connection between them are analyzed. The following measures can be used to lower the pressure impact of the system:①Increasing the open, switch or close time of the servo-valve;②Increasing the diameter of the pipe and using flexible hose to absorb the impact energy;③Using a back pressure valve in the Hydraulic Circuit to improve the back pressure suitably.④An accumulator should be used in the link which is easy to have pressure impact.3) The control model of the hydraulic servo-control system is built in the MATLAB/Simulink software, and is connected to the virtual prototyping to simulation. The position precision of the system is about±0.0003mm after adjustment and the main factors that influence the position precision are analyzed.4) As the load is increasing, the stable position deviation become bigger towards the negative orientation and the velocity become lower so the time from the system started to stable is longer without other hydraulic parameters changed. Amplifier parameter has an influence on the position overshoot. The bigger the parameter, the smaller the value of the stable deviation, and the time from the system started to stable become shorter. But when the amplifier parameter increases to some degree, the velocity becomes unstable and fluctuating. The slope of the input signal has no influence on the position precision of the piston,but the velocity changed with different slope signals, namely, the velocity increasing with the slope value increasing, and the time become shorter. But there is a limit of this relationship. And as the slope value become bigger, the overshoot of the cylinder velocity become lower at the moment that the load is on, but the velocity fluctuation become more terrible before the required position is reached.