The development of optimum control strategy for hybrid EPS system using Taguchi Method

Recently hydraulic power steering systems are commonly used for heavy duty vehicles. The hydraulic pump is driven by belt connected to engine crank shaft. The main disadvantage of this steering system is that energy loss occurs in the case of straight-line driving situation (few or no steering situation). This fact is directly connected to reducing fuel efficiency of heavy duty vehicle equipped the hydraulic power steering systems. To improve the fuel efficiency, it is necessary to consider application of EHPS (Electro Hydraulic Power Steering system) or MDPS (Motor Driven Power Steering system) which have been developed for passenger cars. This paper introduces the research about Hybrid Electro Power Steering (Hybrid EPS) system which combines EHPS and MDPS for heavy duty vehicles. Also the dynamic model and control strategy for the Hybrid EPS are proposed to improve the fuel efficiency by minimizing the energy consumption in steering system using robust design method called “Taguchi Method”.