Distributed Pump Controlled System For Active Disturbance Rejection Control And Its Application On Excavators

Hydraulic excavator is currently one of the most widely used construction machinery,the current traditional hydraulic excavator is driven by valve control hydraulic system,there are many problems such as large volume,oil usage and large energy consumption,with the development of frequency conversion technology,pump-controlled direct drive hydraulic system has become a major research hotspot.The executive components of hydraulic excavators are mostly differential cylinders,and the use of single pump control differential cylinder system alone can not well solve the problem of speed fluctuations caused by load force changes during excavation,coupled with the influence of high-order nonlinearity of the pump control system and mechanical coupling between working devices,external interference,etc.the traditional control method is difficult to obtain better control performance,so it is of great significance to improve the structure and control design of the pump control system of the excavator.Aiming at the problems of flow imbalance and speed fluctuation under multi-quadrant working conditions in the differential cylinder of the excavator working device,a single-double pump hybrid distributed pump-controlled excavator hydraulic system is proposed: the boom is a single-pump differential cylinder system,and the stick and bucket are double-pump parallel pumpcontrolled differential cylinder systems.And the active disturbance rejection control strategy is used to feedback control the position of the pump control system to improve the tracking accuracy and immunity of each actuator.The main research contents are as follows:(1)The working principle of single-pump controlled differential cylinder system and double-pump parallel pump-controlled differential cylinder system and four-quadrant working conditions are analyzed theoretically,and each component is selected according to the technical parameters of the 1-ton excavator,the quality information of the pump control unit is obtained and the corresponding mechanical model is established.Considering the influence of the quality of the pump control unit on the overall excavator structure,the excavator model was simulated with multibody dynamics and checked the strength of key components.(2)In order to compare the control characteristics and energy consumption of the hydraulic system of valve-controlled excavator and the hydraulic system of distributed pump-controlled excavator,the mechanical model of excavator,the mathematical model of load-sensitive valve control system and two types of pump-controlled differential cylinder system were established and the parameters were matched.(3)Considered the influence of high-order nonlinearity of the pump control system itself and external disturbances such as load changes,the active disturbance rejection control strategy is proposed.The transfer function of the pump control system was derived,its order was clarified,and the extended state observer of the corresponding order was established,and the PID controller,linear active disturbance rejection controller(LADRC)and fuzzy linear active disturbance rejection controller(F-LADRC)were designed for comparison to verify the effectiveness of each algorithm.(4)The overall simulation model of excavator is established in MATLAB,and the hydraulic system of PID load-sensitive valve-controlled excavator and the hydraulic system of PID distributed pump-controlled excavator are simulated under typical excavation cycles,and the simulation results show that the double-pump parallel pump-controlled differential cylinder system can effectively suppress the speed fluctuation caused by the four-quadrant working condition.Compared with the valve control system,the root mean square error and maximum error average of the three cylinders are increased by 2.5mm and 7.5mm,respectively,but the system efficiency is increased from 21% to 60%.Compared with the traditional PID,the designed LADRC controller has higher tracking accuracy,77.5% lower error,and 3% higher system efficiency.F-LADRC can effectively suppress signal overshoot and oscillation,further reduce the tracking error by 18%,and achieve tracking performance similar to that of valve control systems,with a system efficiency of 67%.