Research On Closed Oil Circuit Energy Saving Hydraulic Elevator And Its Speed Control Strategy

Hydraulic elevator is an indispensable transportation equipment in vertical building.In recent years,with the rise of elevator projects and household elevators in the renovation of old houses,the installation probability and market demand of hydraulic elevator are increasing day by day.Aiming at the problems of high energy consumption and difficult speed control in the hydraulic elevator system,this paper designs a closed oil circuit energy-saving hydraulic elevator,and explores the energy-saving characteristics and speed control strategy of the system with the methods of theoretical design,simulation analysis and experimental research.The main research contents and achievements are as follows:(1)The traditional hydraulic elevator has the disadvantages of high power of dressing machine and high energy consumption of the system.In this paper,the technology of frequency control,piston cylinder pulling and hydraulic counterweight is integrated.A closed oil circuit energy-saving hydraulic elevator system is proposed,and its mechanical lifting system,hydraulic system and electrical system are designed.The theoretical and simulation results show that the system has the advantages of simple structure,less effective oil consumption and low energy consumption,and under the same working conditions,the installed power of the system is less than that of the traditional valve controlled speed regulating hydraulic elevator,basically reaching the level of traction elevator.(2)The closed-loop speed control block diagram is built,the mathematical model of each main link of the system is established,and the open-loop transfer function of the system is derived.The results show that the system is a fourth-order zero type system,which can not keep stable in the unit closed-loop feedback state.According to the root locus method,only reducing the value of open-loop gain can obtain stable phase and amplitude margin,but no matter how the gain changes,the steady-state error of the system in the closed-loop state is large.(3)The integral correction method is used to change the original system from a zero type system to a type I system,but the system lags behind seriously,which proves that the integral correction method is no longer applicable to the system.The influence of small closed-loop feedback on the system stability is analyzed,and the results show that the effect of small closed-loop feedback on improving the system stability is higher than that of large closed-loop feedback,and the greater the system damping is,the more obvious the effect is obvious.(4)PD control and feedforward-feedback control are integrated,and a feedforward-feedback PD control strategy is proposed.Based on the theory of fuzzy control and expert system,the online adjustment of control parameters is realized.The simulation model of hydraulic elevator system based on three control strategies is built,and the control effect of the three controllers is simulated.The results show that: feedforward-feedback fuzzy PD control and the accuracy of feedforward-feedback fuzzy PD control based on expert system is better than that of feedforward-feedback PD control,and the accuracy of feedforward-feedback fuzzy PD control based on expert system is higher than that of feedforward-feedback fuzzy PD control.