An investigation on the energy-saving effect of a hybrid electric-power steering system for commercial vehicles

This article describes an investigation on the energy consumption of an alternative hybrid electric power steering system. The conventional hydraulic power steering system that is widely used in commercial vehicles can provide high steering-feel and reliability performances. However, since the combustion engine drives the pump, the hydraulic power steering system is energetically inefficient. To cope with this disadvantage of the hydraulic power steering system and to provide a technical base for the steering-related advanced driver assistance system, the Hybrid electric power steering system offers a solution for heavy commercial vehicles. The “Hybrid” of the title means that, for heavy commercial vehicles, the electric power steering system and electro-hydraulic power steering system are integrated in a ball-nut steering system. In this paper, to verify the energy-saving effect of the Hybrid electric power steering system, a dynamic model of the Hybrid electric power steering system was developed to estimate the energy consumption in the steering system. Furthermore, the fuel-efficiency test for the Hybrid electric power steering system were conducted while replacing the two steering systems (the conventional hydraulic power steering and Hybrid electric power steering system) in one vehicle on the chassis dynamometer for the proposed driving cycle. The driving cycle including the steering-angle profile has been developed to clearly investigate the effect on the energy-saving potential by the types of the steering system (hydraulic power steering and Hybrid electric power steering). The simulation results of the energy-consumption estimation showed that the hybrid electric power steering system can reduce the steering-system energy consumption by more than 50% under the proposed driving cycle. Also, the vehicle testing of the chassis dynamometer revealed that the Hybrid electric power steering system can improve the fuel efficiency of the vehicle by 1% for the specified driving cycle.