Energy Saving Analysis Using Pulse Width Modulation Techniques Controlling Electromagnetic Clutch in EPS System

This paper deals with energy-saving advantage in a electric power steering system. Currently, electric power steering systems are commonly used for mini-sized vehicles, and reduction of electric energy of the electromagnetic clutch under non-steering condition is important for energy-savings of the EPS system to improve fuel economy. This paper describes a newly designed method using pulse width modulation techniques controlling the electromagnetic clutch and its experimental results. The electromagnetic clutch has lower energy loss with the advantage of changing with the assist characteristic in the electric power steering system. In addition, relationships between the motor current and electromagnetic clutch current in the system are analyzed for the basis of the electromagnetic clutch model, which accurately predicts the electromagnetic clutch transmitting torque through the motor to the steering rack.