Control Strategy of Speed Segmented Variable Constant Power Powertrain of Electric Construction Machinery

Abstract

Energy conservation and emission reduction have become a global development consensus. Traditional construction machinery driven by an engine has high energy consumption and poor emission. Electric construction machinery is considered to be one of the main trends in the future due to its zero emissions by canceling the engine and using the motor-driven hydraulic system. However, most of the existing electric construction machinery works through the motor to simulate the engine without considering the regulation characteristics of the motor. Therefore, although the existing electric construction machinery improves the emission and the energy efficiency of the power system to a certain extent, the control of the motor and hydraulic systems can still be further optimized. The energy efficiency of the whole machine can be maximized. Based on the LUDV system of construction machinery, a control strategy based on motor speed classification and variable constant power can automatically identify the actual working conditions of the electric excavator and adjust the starting pressure of the constant power valve, to change the constant power range of hydraulic pump and achieve the goal of adapting to the working conditions of power system, is proposed. Simulation and experiments are carried out to verify the feasibility of the proposed control strategy. The results show that the speed classification and variable constant power control system can effectively realize the hierarchical regulation of motor speed and provide relatively stable speed input for the hydraulic system. Moreover, the current working condition can be identified through the pump outlet pressure. The adaption of the working conditions can be realized through the proportional reducing valve by adjusting the starting pressure of the variable constant power valve.