| In recent years,there are more and more researches on pump control system which is more energy-saving than valve control system.Integrated electro Hydrostatic Actuator(EHA)has the advantages of traditional hydraulic actuator system and direct drive electromechanical actuator system.It is easy to modularize and has the characteristics of high power density,high torque or large force.In order to solve the problem of flow balance between the two chambers of the pump controlled asymmetric hydraulic cylinder system,experts and scholars at home and abroad have put forward solutions such as oil replenishment circuit,single motor driven special pump or double pump,multi pump drive and so on.Among them,in the research of the asymmetric hydraulic cylinder system driven by two pumps,the commutation and two-way linear motion are realized by changing the forward and reverse rotation of the motor of the driving pump hydraulic motor unit.In view of this research situation,this paper proposes a dual servo motor pump coupling drive asymmetric hydraulic cylinder control system(hereinafter referred to as the new EHA system).Firstly,the hydraulic principle,overall structure and hardware control system of the new EHA system are introduced.The new EHA system does not use the traditional system of electromagnetic directional valve or servo motor reverse direction,but uses an independent "servo motor +quantitative hydraulic pump" to supply oil to the two cavities of the asymmetric hydraulic cylinder,with the help of two pressure self-control two position three-way valves to realize the two-way linear movement of the asymmetric hydraulic cylinder.In the working process of the system,the two groups of servo motors are always in the low speed standby state,which reduces the starting time of the servo motor,and can quickly complete the unloading of the hydraulic pump,with the characteristics of fast response speed and high control precision.Secondly,through theoretical derivation,the mathematical model of the new EHA system is established,and the transfer function of the system is obtained.The basic characteristics of the related system are studied by MATLAB,and based on AMESim and Simulink The co-simulation of the two softwares determines the parameters of the key hydraulic components,studies and verifies the feasibility of the system mechanism,and explores the influence of the relevant parameters on the performance of the new EHA system;through mathematical derivation and simulation verification,it provides theoretical support for the control strategy,the construction of the experimental platform and the experimental test.Then,a sliding mode backstepping control method is proposed to suppress the mismatched disturbance of the new EHA system.By combining sliding mode control theory with backstepping recursive control theory,a smooth and continuous sliding mode control law is designed.Through theoretical and quantitative analysis of the proposed control algorithm,the stability of the algorithm and the convergence of tracking error are verified,and the feasibility and effectiveness of the control algorithm are verified by joint simulation.The experimental results show that the proposed control algorithm can effectively suppress the unknown matching interference in the new EHA system.Finally,the feasibility of the new EHA system is verified and the actual performance of the sliding mode backstepping control strategy in the operation of the new EHA system is analyzed.The experimental results show that the control strategy can effectively suppress the non matching interference,and the tracking effect is better than that of PID controller.Combined with three parts of theoretical analysis,simulation calculation and experimental verification,this paper expounds the working principle of the new EHA system,analyzes the feasibility of the new EHA system,and verifies that the new EHA system has a good performance of restraining the non matching interference under the sliding mode backstepping control strategy. |
