Variable Speed Triple-pump Controlled Differential Cylinder System And Its Application

With the continuous development and application of hydraulic technology,the hydraulic system used to complete the transmission and control functions is becoming more and more complex,and the accuracy and stability of the system have been put forward higher requirements.All modern products require greater precision and depth in the design and manufacture of modern hydraulic systems.The direct-drive pump-controlled servo hydraulic press adopts quantitative pump and AC permanent magnet synchronous motor as the power unit.The servo hydraulic system realizes the system flow regulation by changing the motor speed,so as to realize the control of the hydraulic system.Unlike traditional valve control system,servo motor and quantitative pump instead of the combination of asynchronous motor and variable pump,have the characteristics of small volume,high efficiency and energy saving,high reliability,is recognized as the hydraulic control system is one of the most important development direction of,but a direct-drive pump control system dynamic characteristics is not higher question limits its wider application.Therefore,it is very necessary to study the dynamic characteristics of hydraulic transmission and control system and improve the dynamic characteristics of hydraulic system in order to further improve and perfect the hydraulic system.The main task of this paper is to put forward a three pump controlled differential cylinder hydraulic system based on the dual pump controlled direct drive differential cylinder hydraulic system and carry on the research,elaborated the principle,composition and characteristics of the system,and studied the dynamic characteristics and energy efficiency of the system.Based on PID position control and PID speed control,a compound speed/position control method with MPC position prediction compensation is proposed.The specific research contents are as follows:(1)This paper analyzes the working principle and stability of the single and double pump controlled direct drive differential cylinder hydraulic system,puts forward the variable speed three pump controlled differential cylinder system,and analyzes its structure and working principle.(2)According to the parameters of excavator boom hydraulic cylinder,the main components of variable speed three pump control differential cylinder system are matched;the mathematical models of each hydraulic component are established,and the models of variable speed double pump control system and variable speed three pump control system are established in MATLAB / Simulink,and the simulation research is carried out;the speed error and position error,pressure change and recovery after load change of the two systems are analyzed The recovery time was compared and analyzed.(3)Integrating three control methods: PID speed control,PID position control and model predictive control,a speed / position compound control with model predictive compensation is proposed.The proposed control method and PID position control method are modeled and simulated,and the tracking performance of position and speed is analyzed.(4)The three-dimensional model of excavator is established and imported into Simulink to obtain the multi-body dynamic mechanical model.The dynamic characteristics of the excavator are analyzed and compared by CO simulation with the variable speed three pump control system.The research results show that: compared with the dual pump control direct drive differential cylinder hydraulic system,the proposed three pump control direct drive differential cylinder hydraulic system can obtain good system stability under no-load and variable load conditions.When the load force and direction change and the speed direction change,the speed vibration amplitude of the differential cylinder is small and the recovery stability time is short.Compared with PID position control,the speed / position compound control system with MPC compensation can not only improve the system stability,accelerate the system response speed,but also reduce the overshoot of position control.In the co simulation of mechanical model and hydraulic system,there are large fluctuations under the influence of multi-body dynamics,but it can still reflect the good dynamic characteristics of the three pump control differential cylinder system.