An Independent Electro-Hydraulic Variable Speed Drive to Improve Energy Efficiency of Electric Wheel Loader Working System

Powertrain electrification is an effective solution to reducing emissions of construction machinery. However, working hydraulic system of existing electric wheel loaders are centralized load-sensing (LS) system. The LS system suffers from low energy efficiency because of valve throttling losses. Therefore, an independent electro-hydraulic variable speed drive (VSD) with separate layout, normal pump speed and closed circuit is proposed to increase the efficiency of working hydraulic system and electric wheel loader. The VSD is powered by a variable-speed electric motor and a fixed pump without throttle control valve, eliminating throttling losses. Besides, the separate VSD utilizes commercially available electric motor and pump, interconnecting actuator via hydraulic pipelines. The system components are modeled in detail and the influence of pipeline is considered in simulation analysis. A mode-based control strategy for the proposed powertrain is developed. The simulation study is carried out to verify the feasibility of the proposed separate design and control strategy. The powertrain operation and energy comparison between proposed powertrain and baseline powertrain are conducted. Results demonstrate the efficiency of independent electro-hydraulic variable speed drive improves from 36.9% to 70.6% compared to centralized LS system. Furthermore, the proposed powertrain reduces energy consumption by 32.3% compared with baseline powertrain.