Steering torque control using variable impedance models for a steer-by-wire system

  • D. S. Cheon
  • K. H. NamEmail author


This paper presents a novel sensor-less steering torque control method for applications to the steer-by-wire system. A steer-by-wire system has not any mechanical link to connect a steering wheel and a rack and pinion gear module. Instead of mechanical devices, two electric motors are used on each side. A one motor is attached to the steering wheel and the other is set on rack and pinion. The motor on the steering wheel works as a deliverer between a steering torque and load torque from the road. In this paper, we focus on motion control related to the steering feel based on impedance control. Therefore, the model of rack and pinion is not considered in this work. In most power steering systems, a torque sensor is used to set impedance effect on driver’s steering feel. In this paper, we proposed a novel steering control method without using any torque sensors. The effectiveness of a proposed method is confirmed from experimental results.

Key Words

Sensor-less force control Disturbance observer Steer-by-wire Impedance control 



impedance ratio


friction coefficient of steering axis


friction coefficient of steering wheel motor


friction coefficient of nominal model


friction coefficient of steering wheel


velocity coefficient


\(\widehat d\)

estimated disturbance by disturbance observer


different angle (steering wheel, steering wheel motor)


coulomb friction


friction force


static friction


inertia moment of steering wheel motor


inertia moment of nominal model


inertia moment of steering wheel


spring coefficient of steering axis


I gain of feedback controller


P gain of feedback controller




nominal model


inverse nominal model


Q filter of disturbance observer


input of disturbance observer


reaction torque of steering axis


torque of steering wheel motor


torque of steering wheel observer


estimated torque of steering wheel


angle of steering wheel motor


angular velocity of steering wheel motor


angular acceleration of steering wheel motor


angle of steering wheel


angular velocity of steering wheel


angular acceleration of steering wheel


velocity threshold


bandwidth of feedforward


bandwidth of Q filter


output of disturbance observer


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Copyright information

© The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.School of Mechanical EngineeringYeungnam UniversityGyeongbukKorea

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