Hydraulic hybrid system coupling traction motor and working hydraulics of electric wheel loader

Electrification drives and enables the design of productive and energy efficient solutions for heavy mobile machines. While components should be properly sized, the multifunctional use of components is vital to fully utilize their capabilities and maximize the overall performance of the machine. This multifunctional use of components can reduce their size and additionally increase the performance of the machine. In this paper, a hydraulic hybrid system coupling a traction motor and working hydraulics is proposed. The analysis focuses on the simultaneous operation of a traction drive and working hydraulics in a wheel loader application. Simulations utilizing a recorded work cycle are used to analyze the system. The energy efficiency of the hydraulic hybrid system is compared to a reference system where the electric motors are separated and working independently. Additionally, the hydraulic coupling system is compared to a mechanically coupled electric motor system. The results indicate that the proposed system offers a more flexible way to couple the electric motors of a traction drive and working hydraulics compared to the mechanical coupling. Also, the single-pump single-actuator mode can reduce the overall energy consumption of the system by 6 percent in Y-cycle operation compared to the reference system. • Hydraulic coupling of the electric motors of an electric wheel loader is proposed • Motor sizing is flexible because load can be distributed between electric motors • The single-pump single-actuator mode increases energy-efficiency by 6 % • The system is effective when hydraulics and traction motor operate simultaneously