Linear quadratic control design in electric power steering system

Electric power steering (EPS) is gradually replacing the conventional hydraulic power steering system in modern cars. The main advantages of EPS system are the ability to minimize energy consumption and its applicability to autonomous driving. This paper discusses the linear quadratic (LQ) control to reduce effort- and time-consuming manual tuning and improve steering feel compared to conventional map control. Moreover, a disturbance observer is introduced to estimate and suppress disturbances due to the mechanical resonance and the self-aligning torque. The effectiveness of combinations of these controllers is evaluated by simulations and HIL simulations.