FAIL-SAFE CONTROL APPARATUS AND CONTROL METHOD FOR ELECTRIC POWER STEERING SYSTEM, AND STEERING SYSTEM

1 . A fail-safe control apparatus of an electric power steering system, the fail-safe control apparatus comprising:

a first sensing unit configured to sense motor position information, which is rotor position information of a motor that supplies an auxiliary steering force for a vehicle, and motor direction information, which is rotation direction information of the motor;

a second sensing unit configured to sense steering torque information or steering angle information of the vehicle;

a failure determination unit configured to compute a difference for the motor position information, estimate a direction value of the motor direction information, and perform computation between the motor position information and the steering torque information or the steering angle information to determine whether a failure has occurred; and

a steering control unit configured to reduce or block an electric current output of the motor according to a result of the determination.

2 . The fail-safe control apparatus of claim 1 , wherein when an error is detected through a first motor position sensor or a second motor position sensor, the failure determination unit computes a difference between a current value and a previous value of each of the first motor position information and the second motor position information.

3 . The fail-safe control apparatus of claim 2 , wherein the failure determination unit determines that a failure has occurred when the differences are greater than or equal to a threshold value and estimates direction values of the first motor direction information and the second motor direction information when the differences are less than the threshold value.

4 . The fail-safe control apparatus of claim 3 , wherein the failure determination unit determines that a failure has occurred when each of the direction values has non-sequential values for a certain time and calculates a first steering angle corresponding to the first motor position information and a second steering angle corresponding to the second motor position information when each of the direction values has sequential values for a certain time.

5 . The fail-safe control apparatus of claim 4 , wherein the failure determination unit computes a difference between at least one of the sensed steering angle information and steering torque information and the first steering angle and computes a difference between at least one of the sensed steering angle information and steering torque information and the second steering angle.

6 . The fail-safe control apparatus of claim 5 , wherein the failure determination unit determines that a failure has occurred when the differences are greater than or equal to a threshold angle.

7 . A fail-safe control method for an electric power steering system, the fail-safe control method comprising:

a first sensing step for sensing motor position information, which is rotor position information of a motor that supplies an auxiliary steering force for a vehicle, and motor direction information, which is rotation direction information of the motor;

a second sensing step for sensing steering torque information or steering angle information of the vehicle;

a failure determination step for computing a difference for the motor position information, estimating a direction value of the motor direction information, and performing computation between the motor position information and the steering torque information or the steering angle information to determine whether a failure has occurred; and

a steering control step for reducing or blocking an electric current output of the motor according to a result of the determination.

8 . The fail-safe control method of claim 7 , further comprising a storage step for storing the motor position information in real time, matching the steering torque information or the steering angle information to correspond to the motor position information, and storing the matched information.

9 . The fail-safe control method of claim 7 , wherein the first sensing step comprises sensing first motor position information and first motor direction information through a first motor position sensor and sensing second motor position information and second motor direction information through a second motor position sensor.

10 . The fail-safe control method of claim 9 , wherein the first sensing step comprises sensing an error through the first motor position sensor and the second motor position sensor.

11 . The fail-safe control method of claim 10 , wherein the steering control step comprises blocking an electric current of the motor to stop the motor when it is determined that a failure has occurred and reducing an electric current output of the motor when it is determined that an error has occurred but is determined to be normal.

12 . A steering system comprising a fail-safe control apparatus configured to control operation of a motor, wherein the fail-safe control apparatus determines an error of at least one motor position sensor and controls operation of the motor on the basis of steering angle information according to a result of the determination.

13 . The steering system of claim 12 , further comprising:

at least one motor position sensor configured to measure a state of the motor to acquire motor state information; and

at least one steering angle sensor configured to measure a steering angle state of a steering wheel to acquire steering angle information,

wherein the fail-safe control apparatus determines an error of the motor position sensor on the basis of the motor state information and the steering angle information and controls operation of the motor on the basis of the steering angle information when it is determined that the motor position sensor has failed.

14 . The steering system of claim 13 ,

wherein the at least one motor position sensor comprises a first motor position sensor configured to measure the state of the motor and acquire first motor state infatuation, and

wherein the fail-safe control apparatus determines an error of the first motor position sensor on the basis of the first motor state information and the steering angle information and wherein the fail-safe control apparatus calculates a reduced assistive electric-current value on the basis of the steering angle information when it is determined that the first motor position sensor has failed and controls operation of the motor on the basis of the calculated electric-current value.

15 . The steering system of claim 13 ,

wherein the at least one motor position sensor comprises a first motor position sensor configured to measure the state of the motor to acquire first motor state information and a second motor position sensor configured to acquire second motor state information, and

wherein the fail-safe control apparatus determines an error of the first motor position sensor and the second motor position sensor on the basis of the first motor state information and the second motor state information and controls operation of the motor on the basis of the steering angle information when it is determined that either the first motor position sensor or the second motor position sensor has failed.