At present, there are still many difficulties in directly driving the hydraulic pump by high-power servo motors, mainly because the speed range of the hydraulic pump is required to be very large. The minimum speed of the general hydraulic pump is 600 r/min, and the hydraulic pump can work normally even if it is below 10 r/min.
High-power AC servo motor and its control technology The emergence of high-power AC servo motor is a new product produced in the past 10 years. At present, switched reluctance motor (SMR) is mainly used in technology, which has the advantages of simple and reliable, high-efficiency operation in a wide speed and torque range, four-quadrant operation, fast response speed and low cost. The disadvantages are: large torque fluctuation and large vibration; the system has nonlinear characteristics, high control cost, and low power density.
The AC servo motor drive control unit is composed of large-scale integrated circuits, high-power rectifier modules and other electronic power components. With the development of electronic technology, the performance of high-power AC servo motor drive control unit has been continuously improved, and the price has been continuously reduced, which has promoted the realization and promotion of high-power AC servo drive technology, and provided the possibility of using AC servo drive in the field of forging equipment. The focus of the research is to concentrate scientific research strength, develop high-power AC servo motor control technology and related application technology with independent intellectual property rights, and provide a solid foundation for the development of servo hydraulic presses.
The closed-loop control technology of hydraulic pressure and position of hydraulic press is not mature enough through servo motor. Traditional hydraulic presses control hydraulic pressure and position through proportional valves and proportional servo valves. Special control algorithms need to be studied, so that the hydraulic pressure has high stability and high precision between 1 and 25 MPa.
In order to save more energy and reduce energy loss as much as possible, it is necessary to recover and reuse the potential energy of the sliding block's dead weight and the energy generated by the pressure relief of the oil cylinder. At present, there is no mature practice and experience in this area. In terms of energy management, since the instantaneous power is many times larger than the average power, energy allocation should be done well in large servo hydraulic presses to avoid impact on the power grid.
Because most of the existing hydraulic presses are controlled by PLC, but the servo hydraulic press adopts hydraulic pressure and speed closed-loop program control, and the amount of calculation is large, and it is difficult for ordinary PLC to meet the needs. The control system of the servo hydraulic press is controlled by an industrial PC, and a special control system must be developed.
The material and shape of each stamping part are different, resulting in a completely different stamping process. For example, the silent punching process, the control of the speed change point is the key; for the reverse extrusion forming of the magnesium alloy cup-shaped part, the slider needs to undergo 4 kinds of work in one working cycle. Different speeds, in which the extrusion process is still controlled by constant pressure. Therefore, the servo hydraulic press can only exert its superiority when it is optimized and combined with various forming processes. It is very important to study the forming mechanism of various forming processes and establish the optimal parameters suitable for the forming process to improve product quality, production efficiency and reduce production costs.