Electric power steering system and method for verifying steering angle thereof

1. An electric power steering system comprising:

a torque sensor including a first rotor connected to an input shaft, a second rotor connected to an output shaft, a first angle element for measuring an absolute steering angle of the first rotor, and second and third angle elements for measuring relative steering angles of the first rotor; and

an electronic control unit for determining a reference steering angle based on the absolute steering angle and the relative steering angles received from the torque sensor, tracing and accumulating first and second absolute steering angles rotated from the reference steering angle based on the relative steering angles received from the second and third angle elements, and averaging the first and second absolute steering angles to provide the calculated final absolute steering angle when the difference between the accumulated first and second steering angles is within the preset reference difference.

2. The electric power steering system as claimed in claim 1 , wherein when the difference between the first and second absolute steering angles exceeds the reference difference, the electronic control unit maintains the first and second absolute steering angles accumulated before the exceeding.

3. The electric power steering system as claimed in claim 2 , wherein the electronic control unit counts a number of times by which the difference between the first and second absolute steering angles exceeds the reference difference, and outputs preset alarm information when the counted number of times exceeds a predetermined number of times.

4. A method for verifying a steering angle of an electric power steering system including a torque sensor including a first rotor connected to an input shaft, a second rotor connected to an output shaft, a first angle element for measuring an absolute steering angle of the first rotor, and second and third angle elements for measuring relative steering angles of the first rotor, the method comprising the steps of:

determining a reference steering angle based on the absolute steering angle and the relative steering angles received from the torque sensor;

tracing and accumulating first and second absolute steering angles rotated from the reference steering angle based on the relative steering angles received from the second and third angle elements;

determining whether the difference between the accumulated first and second absolute steering angles is within a preset reference difference; and

averaging the first and second absolute steering angles to provide the calculated final absolute steering angle when it is determined in the determining step that the difference between the accumulated first and second steering angles is within the preset reference difference.

5. The method as claimed in claim 4 , further comprising, after the determining step, the step of, when the difference between the first and second absolute steering angles exceeds the reference angle, maintaining the first and second absolute steering angles before the exceeding.

6. The method as claimed in claim 5 , wherein the providing step comprises the steps of:

counting a number of times by which the difference between the first and second absolute steering angles exceeds the reference difference; and

outputting preset alarm information when the counted number of times exceeds a predetermined number of times.