Features Of The Control Structure Of The Synchronous Lifting Hydraulic System

2021-04-06 12:33

The existing hoisting equipment series products are full hydraulic transmission and control structure. The composition and working principle of the hydraulic system are basically the same, and the core part is the hydraulic drive system.

The hydraulic drive system is a hydraulic system with high-power, time-varying load and viscosity. The hydraulic circuit of the variable pump controlling the quantitative motor has the characteristics of simple structure, working efficiency and constant torque output. The output flow of this kind of variable system can follow the input signal-the displacement of the pressure reducing proportional valve spool to make continuous proportional changes. During the working process of the hydraulic lifting equipment, the driver operates the pressure reducing proportional control valve and inputs a gradually changing pressure oil to the proportional hydraulic cylinder of the variable control system. The displacement of the proportional hydraulic cylinder controls the displacement of the spool of the servo valve, and the servo valve passes through the differential. The hydraulic cylinder controls the swing cylinder body to change the swash plate inclination angle of the variable pump, so that the flow of hydraulic oil input to the hydraulic motor is gradually changed, thereby controlling the rotation speed of the hydraulic motor, and realizing the acceleration start and deceleration operation of the lifting container, and it can move up and down at a constant speed and crawl at a low speed. In the stage, the driver keeps the operating handle still, thus completing a lifting cycle.

The hydraulic drive system is a variable hydraulic pump with direct feedback displacement adjustment variable control structure, and an open loop plus simple manual operation proportional pressure reducing valve control method. In this control method, the output flow of the hydraulic pump is easily affected by the load and is unstable. The volumetric efficiency of the pump changes with the working pressure of the system and the viscosity of the hydraulic oil. The output flow of the hydraulic pump is affected by the load and oil temperature. Due to the compressibility of the hydraulic oil, the elasticity of the pipeline, the leakage of hydraulic components, etc. In addition, the system does not have a motor output speed detection and feedback control loop, and the system cannot automatically clean up the output speed error of the hydraulic motor caused by various factors such as load changes. Therefore, the speed control accuracy of the existing hydraulic drive system is relatively low. When it comes to the performance of hydraulic lifting equipment, it cannot meet the performance requirements of modern hydraulic lifting equipment such as control and ride comfort.

Therefore, it is urgent for the hydraulic drive system control scheme to realize the computer control of the hydraulic lifting equipment to change its comprehensive performance, improve the speed rigidity of the system, shorten the load disturbance adjustment time, and maintain the system efficiency of the high-power, large-inertia load pump control motor servo system The control scheme to improve the performance of hydraulic lifting equipment.