A series electric hybrid wheel loader powertrain with independent electric load-sensing system

Electric hybrid powertrain is a promising way for wheel loader electrification. However, the widely used centralized load-sensing working hydraulic system has low efficiency with imbalance load. A novel electric hydraulic system configuration making good use of the electric drive is needed. An independent electric load-sensing hydraulic system for series hybrid wheel loaders is proposed in this study. The lift/tilt functions are powered by speed-controlled fixed displacement pump and controlled by proportional control valves. The independent electric load-sensing hydraulic system eliminates the system inherent power losses of the multi-actuator hydraulic system and combines the high efficiency of variable speed fixed displacement pump and high dynamic performance of valve control. Simulation study on energy efficiency comparison among the proposed powertrain, the existing hybrid powertrain and the non-hybrid powertrain is carried out to check its potential on fuel saving. Results show that the independent electric load-sensing system improves the working hydraulic system efficiency from 34.0% to 54.9% compared to the centralized load-sensing system. The proposed hybrid powertrain saves 11.8% of the fuel consumption compared to the existing hybrid solution, and 41.9% lower than non-hybrid powertrain.