Performance analysis of an automatic idle speed control system with a hydraulic accumulator for pure electric construction machinery

To reduce the energy consumption and emissions of a hydraulic excavator (HE), an electric motor (EM) is employed to replace the internal combustion engine (ICE) that powers the hydraulic pumps. Owing to the excellent control characteristics and high efficiency of the EM, a two-level idle speed control system with a hydraulic accumulator (HA) for a HE is proposed to reduce energy consumption and improve the control performance of the actuator when the idle speed control (ISC) is switched off. A mathematical model is established and key parameters are analyzed and optimized. A simulation is performed using AMESim, and a control strategy for the two-level idle speed control is developed by using a co-simulation between AMESim and Simulink. A test rig is built based on the optimized parameters and simulation results. Experimental results show that the EM speed can be automatically switched between the first idle speed, second idle speed, and normal operating speed. Although the idle speed of the EM in the novel ISC system can be reduced more than that in a conventional ISC system, the proposed ISC system can still build actuator pressure more quickly in a working mode when the ISC is switched off. Compared to a system without idle speed control, the energy saving of the proposed system is approximately 36.06%. The proposed two-level idle speed control system with a HA can achieve high energy efficiency and excellent control performance, and it can be also applied to engine-driven construction machinery.