Electric power steering apparatus and control method for current thereof

#1. Field of the Invention

#The present invention relates to an electric power steering apparatus. More particularly, the present invention relates to an electric power steering apparatus capable of controlling a current thereof and a method of controlling the current, which can compensate for a current of a motor so as to increase auxiliary steering power of a vehicle in response to an increase of friction caused by contraction or an increase of viscosity at a low temperature, such as in the winter season.

#2. Description of the Prior Art

#The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

#FIG. 1 is a view illustrating the electric power steering apparatus according to a prior art; and

#FIG. 2 is a block diagram illustrating a part of an electric power steering apparatus capable of controlling the current according to the present invention.

#Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same elements will be designated by the same reference numerals although they are shown in different drawings. In the following description, detailed explanation of known related functions and constitutions may be omitted to avoid unnecessarily obscuring the subject manner of the present invention.

#An electric power steering apparatus according to the present invention includes, as shown in FIG. 1, the steering system 100 receiving the steering torque of the steering wheel 101 so as to steer the wheels 108 and the auxiliary power mechanism 120 including the torque sensor 121, the ECU 123, the motor 130, and the electric power apparatus 140 for applying the auxiliary steering power to the steering system 100.

#FIG. 2 is a block diagram illustrating a part of the electric power steering apparatus capable of controlling the current according to the present invention. As shown in FIG. 2, the electric power steering apparatus according to the present invention includes a temperature sensor for measuring a temperature at the starting of a car, the temperature sensor being located within the ECU 123, a motor position sensor for detecting a relative steering angle of the motor 130, the motor position sensor being mounted in the motor 130, a cumulative transfer quantity calculation unit for calculating a cumulative transfer quantity of the rack bar 109 by using information detected in the motor position sensor, a counter for calculating an elapsed passage from a starting time, the counter being located within the ECU 123, a friction coefficient determination unit for determining a friction coefficient by using a setting map of a friction coefficient according to information inputted from the temperature sensor, the cumulative transfer quantity calculation unit, and the counter, respectively, and a target current calculation unit for calculating a compensation quantity for the friction by using the friction coefficient determined in the friction coefficient determination unit and determining a target current.