Design And Control Strategy Of Pump-controlled Direct-drive Electro-hydraulic Single-rod Actuator

DD-EHSA(Direct Drive Electro-Hydrostatic-Single-rod Actuator)has the advantages of high output power,high reliability,small space occupied,easy to produce,etc.,and has good application prospects.Many domestic research institutes have done a lot of research on electro-hydraulic actuator(EHA)for aviation,but most of them use double-rod cylinder for related mechanism research,while pump-controlled direct-drive single-rod actuator research is less,and the different volume change rates of rodless cavity and rod cavity during the reciprocating motion of hydraulic cylinder in closed oil circuit lead to the difficulty of accurate compensation of pump delivery flow,and the product integration is not high.Based on the project of "Research and Application of Pump-Controlled Direct Drive Electrohydrostatic Differential Actuator" in the State Key Laboratory of Fluid Dynamics and Mechatronic Systems,Zhejiang University,this paper develops a new type of highly integrated pump-controlled direct drive electrohydraulic single rod actuator(EHSA)unit.This paper aims to improve the efficiency,energy saving and light weight of DD-EHSA,and researches the flow compensation method of single rod hydraulic cylinder,the overall compact and integrated design of actuator and the intelligent control strategy suitable for direct-drive servo system,which lays a theoretical foundation for the productization and application of DD-EHSA.The main research contents are as follows:(1)Different flow compensation methods and variable control methods for pumpcontrolled single rod actuators are described,the advantages and disadvantages of each scheme are analyzed and compared,and the hydraulic circuit conforming to DD-EHSA is selected and designed and its principle is analyzed and verified.The results show that the adopted hydraulic circuit of variable speed motor with dosing pump using accumulator and liquid-controlled check valve to balance the asymmetric flow can realize the direct pump control of DD-EHSA.(2)With the research objective of modular integration of multi-body structure of DDEHSA,the structure of actuator is designed,optimized and integrated,and the effective connection of motor,pump,integrated valve group and accumulator is realized;the selection analysis of key parts of DD-EHSA is carried out,the organic interface of machine-electrichydraulic is designed and the prototype is built;the strength calibration,modal analysis and internal flow field optimization were carried out for key parts of DD-EHSA.The results show that the designed actuator structure is feasible.(3)In order to realize the accurate displacement control of DD-EHSA,the auto disturbance rejection control method is used to provide position feedback to the system,and the joint simulation of AMESim and MATLAB/Simulink is carried out for the designed electro-mechanical-hydraulic control system of DD-EHSA,and position tracking performance of the ADRC with the fourth order linear extended state observer to the system is analyzed.The results show that it can not only meet the normal position servo control of pump-controlled direct-drive electro-hydraulic single-rod actuator,but also make the system have higher control accuracy when encountering external disturbances.