Research On Low Energy Consumption VBHF System

Blank holder force(BHF) is one of most fundamental and predominant parameters of blank holding which is an important technologic measure for deep drawing in sheet metal forming processes. Blank holding with controlled variable blank holder force(CVBHF) is can further improve deep drawing forming limits and geometrical precision of sheet metal parts,compared with blank holding with constant and uncontrolled BHF. Hydraulic CVBHF has become major development direction of blank holding with VBHF, because it can not only provide greater BHF, but also achieve high performance when controlled by computer. The energy consumption in providing BHF is not taken into enough consideration, and the energy saving blank holding will have great significance for the increasingly severe condition of energy sources. In this paper, a low energy consumption VBHF system is proposed, and the energy saving mechanism and the control strategy for the system are researched into by methods of theoretical analysis, numerical simulation and experiment, aiming at achieving energy saving blank holding and high performance Hydraulic CVBHF control.The energy consumption of the low energy consumption VBHF system is analyzed theoretically using the energy method, and the blank holding energy consumption is compared between the low energy consumption VBHF system and hydraulic cushion blank holding system, clarifying the energy saving mechanism of low energy consumption VBHF system.Base on two control modes, the closed chamber controlled by a servo valve and the closed chamber controlled by a servo valve through servo cylinder of low energy consumption VBHF system, for high nonlinearity of the system, the nonlinear mathematical models and the PID controlled fundamental simulation models of closed-loop system are built, and a series of researches including the response characteristics, the main parameters and its influence, the tracking performance to typical VBHF loading curves, and the blank holding energy consumption of the system are carried out to confirm the energy saving and VBHF control feasibility of the system.Because the low energy consumption VBHF system includes uncertain parameters, the Fuzzy controller, Fuzzy-PID switch controller, Fuzzy-PID hybrid controller and Fuzzy-PID adaptive controller are designed by using the fuzzy intelligent control theory, and corresponding simulation models are established. The relative best control strategy is determined by comparing the control effects of them.In order to realize energy saving and high performance VBHF control of the low energy consumption VBHF system, an Affine Nonlinear mathematical model for this system is established, a exact linearization of the model is made by using the differential geometry theory, and the linear quadratic state regulator is presented, finally simulation model of the system base on LQR optimal control is set up to gain the system optimal control method considering both minimum energy and optimal performance.A low energy consumption VBHF experiment system is built by integrating physical simulation equipment, a real-time data acquisition and control program on LabVIEW and other correlative control hardware. The results from experiments and the simulations are in a reasonable agreement, and the validity of simulation research is confirmed.The research results demonstrate that the low energy consumption VBHF system has remarkable energy saving effect, static and dynamic characteristics conforming to the application requirements, and a high value for engineering application. The works lay a foundation for the engineering application of low energy consumption VBHF system in some aspects of principle, method and physical realization.