Study On A High-speed And Integrated Electro-hydraulic Control System For Punching

High speed CNC punch press is a kind of CNC flexible sheet punch processing equipment. The hydraulic CNC punch press has the merits of high frequency, good stabilization, low noises, adjustable speed and stroke, nice static and dynamic response property, alterable stamping force, adapt to many stamping technique and so on. It is widely used in every walk of life at present. Recently, the high speed hydraulic control system, which is the core of the punch press, relies on importation in my country. So is necessary to develop a high speed hydraulic control system to break the importation situation.Firstly, the dissertation introduces the current status of development and the developing direction at home and abroad. Then, present the main transmission system and its developing direction. This paper bring forward to three kinds hydraulic scheme: numeric-cylinder controlled mechanical-hydraulic-valve hydraulic control system;numeric-cylinder controlled hydraulic control system and servo valve controlled hydraulic control system, and then give exhaustive analysis to the three scheme. Based on it, the third scheme is chosen for the hydraulic control system. Then calculates the static property of the selecting scheme, and choose the main hydraulic components.Mathematic models of servo valve controlling asymmetrical cylinder hydraulic system are established. In the process of the modeling of servo valve, theoretical modeling and simplified practice modeling which is used in engineering practice frequently are used together. Accordingly, so many parameters, which is used in the theoretical modeling but they aren't supplied by manufacturers for secret, are avoided. In additions, the effects form the variation of the press on the parameters are taken into account, so different transfer functions are established for different work status base on them.A good controller is designed for the servo-hydraulic system. Two general programme are built using matlab software to realize the Ziegler-Nichols method fordecide the PID parameters and to change general transfer function into inertia transfer function with transport delay. After decided by the Ziegler-Nichols method, the PID parameters are tuned by the simpler optimization method by adopting matlab's optimization control toolbox.Build simulation models using the simulink tool of matlab soft according to the mathematic models in three work stations. Then research the stability of the hydraulic system and the effect of tuned PID parameters. The analysis and simulation of the servo-hydraulic system shows that the design of the servo-hydraulic system can meet the design requirement and that the PID control capability and the dynamic characteristics of the servo-hydraulic system is improved after the PID parameters obtained using Ziegler-Nichols method and then tuned using the simpler optimization method . So the two methods provide a quickly and convenient method to decide effective PID parameters.