Characteristics study of electro-hydraulic load-sensing control system for mobile machines

The hydro-mechanical load-sensing control is an efficient system solution to working function of mobile machines since the system pressure always adapts to the highest load pressure. The main issue of this system is its instability problem caused by hydro-mechanical feedback control. Moreover the pressure margin between system and load pressure set by the load-sensing compensator is usually fixed and has less control flexibility. Therefore, an electro-hydraulic load-sensing control system occurs, where the load pressure is sensed by pressure transducer and load-sensing control is achieved electronically. It eliminates the hydro-mechanical feedback control loop and has more control flexibility. The previous studies mainly focus on the system function, controller design and system efficiency. However the quantitative analysis of system characteristics has not yet been studied. Therefore, in this paper a method is provided to investigate the influences of pump displacement dynamics and preset pressure margin on system control performance. A hydraulic load-sensing control test rig is developed. Results show a good agreement between simulation and test results. The pressure margin fluctuation is reduced by using a pump with faster displacement dynamics and a larger cut-off frequency of load velocity control is obtained with a larger preset pressure margin however this results in lower system efficiency.