Research On Direct Drive Pump-controlled Servo Hydraulic System And Its Energy-saving Mechanism

Direct drive pump-controlled servo hydraulic technology is a new transmission technology with advantages such as energy-saving, high efficiency, wide timing range, high reliability, low noise and being easy to realize digital control, and it has broad and potential application in forming equipment field. But direct drive pump-controlled servo hydraulic system is a kind of volume velocity governing, along with including the part of driver and motor, it has main key problems of long response time and imperfect control performance. Deep and systematic researches have been done centered on the difficult problems, and the applications of direct drive pump-controlled servo hydraulic technology in forming equipment and its energy-saving mechanism have been thoroughly exploredThe mathematical model of direct drive pump-controlled servo hydraulic system was built, simulations and open-loop step experiments were held to analyze and research the affect that main parameters exert on the performance of direct drive pump-controlled servo hydraulic system. The energy consumption analysis and experiment of the two systems, which are pump-controlled speed governing system and hydraulic speed governing system with inlet throttle, are given. The applications of intelligent control strategies, including extension control and neural network predictive control, were studied. The application of direct drive pump-controlled servo hydraulic technology in hydraulic press was researched, a pump-controlled servo hydraulic press was designed and its dynamic performance and energy consumption simulation and experiment was made. The application of direct drive pump-controlled servo hydraulic technology in retrofitting traditional die casting machines are given, and the simulation and experiment were made. Concretely, the dissertation's main contributions are as follows:(1) Aiming at the contradiction between rapid response, stability and accuracy in position control of pump-controlled electro-hydraulic servo system, a multi-mode extension control electro-hydraulic servo system was proposed. According to the characteristic information of the system, correlation function was established by multi-mode extension control switch. The movement process was divided into three parts according to correlative degree, different control mode is used in different domain to realize subsection control. Every control mode could get ideal result in its effective control domain. Multiple requirements of control system are considered and the goals of rapid, smooth and accurate positioning could be got. The system had rapid response and strong robustness, and can realize high precision control. It provides a new way for the intelligent control of electro-hydraulic system.(2) Aiming at the hysteresis of traditional control strategy and the strong nonlinearity and time-varying parameters of hydraulic systems, neural network model predictive control was applied to direct drive pump-controlled servo hydraulic system, the structure of control system was designed and the simulation research was carried out. The system can realize on-line self-learning, compared with traditional PID control and fuzzy control, it has better self-adaptive ability and control precision.(3) Mathematical model and energy consumption simulation method for direct drive pump-controlled servo hydraulic system have been built, and the measures to improve its dynamic performance have been proposed on the basis of analyzing its response speed and precision stability theoretically; the energy-saving mechanism of direct drive pump-controlled servo hydraulic system have been researched. Unlike cutting, load of forming process presents periodical peak-like feature, to fit it, the traditional hydraulic drive system exists energy loss inevitably no matter volume speed governing or cutting speed governing are adopted; however, relying on controlling speed and torque to fit actively the varying load, direct drive pump-controlled servo hydraulic system can save energy to the full.(4) The hydraulic system of the2000kN multi function direct drive pump-controlled servo hydraulic press was designed and the first prototype was developed. Taking a specific metal sheet deep-drawing process as an example, the working principle and energy-saving mechanism were analyzed theoretically and simulated numerically and researched by experiment. The main energy-saving links lies in reducing the overflow in keeping pressure stage and stopping the motor in standby stage. The study shows the hydraulic press can realize position (speed) and pressure double closed-loop control, and can optimize the process program. Compared to same type of traditional hydraulic press, over20%energy can be saved, the simulations were in agreement with the experiments.(5) The direct drive pump-controlled servo retrofitting scheme for8000kN die casting machine was given and carried out. The energy-saving mechanism was researched by simulation and experiment. The experiment shows that the retrofitted die casting machine can save46.3%energy and improve production efficiency by5%. The simulation was identical with the experiment. The main energy-saving links lays that direct drive pump-controlled servo hydraulic technology solved the problem of the match between the power source and the varying load, lowering the throttling loss and the overflow loss; the main reason for improving the production was speeding up the motor during the accumulator adding oil.Given at present there are not commercial direct drive pump-controlled servo hydraulic presses and die casting machines in China, the research of the paper provides theoretical basis and technological guidance for the development of such new products and possesses important theory and application value.