Research On Energy Regulation Based Variable-speed Electrohydraulic Valve-controlled Motor Drive System

Variable-speed electrohydraulic drive is the technique that changing the pump's output flowrate via changing the motor's speed. It has been greatly studied and improved these years. And it has been used in hydraulic elevator, injection machine and fan drive et al. Variable-speed electrohydraulic drive is very popular because of its high efficiency. But it also has some disadvantages such as slow response, poor low-speed performance due to the big inertia of motor-pump. The main disadvantage is slow-response, which makes it only be used in the situations of low response and low control precision. To solve these problems, a flow control valve is added to realize the compound control drive composing of variable-speed control and valve control. The compound control drive can improve control precision, low-speed performance, and the deceleration response. But it is helpless to improving the acceleration response.Energy regulation based variable-speed electrohydraulic drive technique through adding an energy regulation device (ERD) into the compound drive system, is a good solution to this problem. If the system is accelerating while the pump can't accelerate quickly due to its big interia, the ERD releases energy in order to improve response. If the system is decelerating while the pump can't decelerate quickly, the ERD is open to absorb system redundant hydraulic oil. It decreases restriction loss and overflow loss. In other cases, the ERD is closed. Energy regulation based variable-speed electrohydraulic drive technique has been applied in cylinder control. The simulations and experiments results have shown that it can improve the acceleration response greatly and gain a good energy-saving effect. But all experiments were implemented under no-load condition. Load experiments have not accomplished yet.This dissertation discusses the application of energy regulation based variable-speed electrohydraulic drive technique to the hydraulic motor's speed control. After modeling and analyzing the ERD and the total system, the hierarchical control strategy is proposed, which realizes the coordinate control together with the erergy regulation idea. A large number of simulations and experiments, which include no-load and load conditions, have been carried out. The results show that the energy regulation based variable-speed electrohydraulic valve-controlled motor drive can improve the hydraulic motor's acceleration response on the base of high efficiency as the conventional variable-speed electrohydraulic drive and it has a good anti-load-interference ability. At the same time, the modification works will be small due to the ERD's simple structure. And the energy regulation based variable-speed electrohydraulic drive has a very good application prospect.The Chapter 1 introduces the two basic speed-regulation modes, the valve resistance technique and the pump displacement control technique, in hydraulic drive firstly. Then, from the development of frequency control technique, the background and the present state of the variable-speed electrohydraulic drive are discussed in detail. The accumulator is an important component of the ERD. So the accumulator's main functions and some typical application examples were given. The control strategy is very important too, sepecially to the MIMO system. The frequent control strategies are also discussed in the Chapter 1.The Chapter 2 discusses the ERD thoroughly. The ERD can display two aspects of effect, which are the auxiliary power sourse and the role of absorbing pulse ripple. And this chapter gives a detailed description about the ERD's use in the open-loop or close-loop hydraulic systems. The main effect of the ERD to this system is its purpose of auxiliary power sourse. Also, the Chapter 2 discusses the reason why the ERD can absorb pulse ripple.The Chapter 3 firstly introduces the principles of energy regulation based variable-speed electrohydraulic valve-controlled motor drive, the structure of the testrig. It introduces emphatically the design of the controller based on ARM. Then the mathematical model of the whole system was deduced. After linearization, the system's control performance was discussed. The Chapter 3 also discussed qualitatively the influence of adding ERD to the valve-controlled motor drive system.The Chapter 4 proposed the hierarchical control structure on the base of energy regulation idea. It also discussed the principles and implementations of the energy layer, the control layer and the feedback layer. The control strategies of the other three contrast system were also discussed in this chapter.The Chapter 5 is the simulation discussiones, which not only includes the constant-load simulations, but also the varying-load simulations. To analyzing the system's performances generally, various input speed forms, like as step, sinusoldai, rectangle et al, are designed. The disturbed simulations are also implemented. The simulations of ERD's main parameters are also carried out in this chapter for the purpose of the design rule of the ERD.The Chapter 6 is the experiment discussiones, which also include the constant-load and the varying-load experiments. It also has various input speed forms as the Chapter 5. The simulations and experiments results show that the discussed system in this paper can improve the hydraulic motor's acceleration response on the base of high efficiency like as conventional variable-speed electrohydraulic drive. And the energy regulation based vairvble-speed drive has a good anti-load-interference ability.The Chapter 7 is the conclusions. It also gives the suggestions for the further research.