Research On Gravitation Potential Energy Recovery System In Hydraulic Lifting Device

In hydraulic transmission,due to the merits of high power density and simple structure,hydraulic lifting devices are widely used in extensive applications,such as hydraulic lifting platform,hydraulic forging equipment,hydraulic excavators,forklifts and other engineering machinery,and so on.These hydraulic lifting devices usually control the working parts descent velocity and lock themselves in any position by balance circuit.However,traditional balance circuit adopts the throttling effect of balance valve to dissipate gravitation potential energy of load,so during the frequent lifting and descending process of hydraulic lifting device,most of the gravitation potential energy is converted into heat at the valve port,which leads to the rise of system temperature,the reduce of hydraulic oil viscosity,and the increase of system leakage,and seriously affects the working efficiency and the equipment service life.To solve this problem,the recovery of the gravitation potential energy in hydraulic lifting device descending process is researched in this paper.The main contents are introduced as follows :According to the analysis and summary of energy recovery system research status at home and abroad,a new-type full hydraulic gravitation potential energy recovery system principle with fixed displacement motor and variable displacement pump is proposed,and then,the descending process of the system is analyzed,the result shows that the variable displacement pump as the key component in the system should use swash-plate axial piston pump with constant power control.Based on the analysis and summary of existing constant power control mechanism of the swash-plate axial piston pump,a new-type constant power control principle is proposed,and the new-type constant power control mechanism is designed.Then,mathematical model of the mechanism is established,and simulation model of swash-plate axial piston pump using the new-type constant power control mechanism is built in ADAMS and AMESim.The output response in different conditions of the model is studied.The simulation results show that the new-type constant power control mechanism has the advantages of fast response,small overshoot and steady-state error.The driving power of pump can be well-controlled by control pressure.Finally,to obtain better performance,the influence of key parameters on the mechanism performance is analyzed.On the basis of the new constant power control mechanism,the integer gravitation potential energy recovery system is proposed.The mathematical model of the system is established,and the key parameters of accumulator,variable displacement pump,fixed displacement motor and constant power control mechanism are matched.Simulation model of the new gravity potential energy recovery system is built in ADAMS and AMESim,then system performance and energy recovery efficiency in different conditions are analyzed.The results show that the hydraulic cylinder can keep steady descent speed under different load conditions.The load is smaller,the pressure in hydraulic cylinder rod chamber is greater to compensate decrease of the motor efficiency,resulting in gravity potential energy recovery efficiency of the system decreases with the reduction of load.The influence of key parameters of accumulator,fixed displacement motor and variable displacement pump on the dynamic performance and the recovery efficiency of the system are analyzed.The results show accumulator parameters have an effect on the energy recovery efficiency,but have no effect on the dynamic performance of the system.The parameters of fixed displacement motor and variable displacement pump affect both energy recovery efficiency and dynamic performance of the system: the displacement has great influence on the energy recovery efficiency,while the rotary inertia has great influence on the dynamic performance of the system.