Steering control apparatus and steering control method

1. A steering control apparatus comprising:

a first sensing unit configured to sense a steering torque using a torque sensor;

a high frequency output unit configured to input a steering torque to a high pass filter and output high frequency steering torques in which low frequency steering torques are eliminated;

a detection unit configured to detect a first frequency corresponding to a maximum steering torque among high frequency steering torques;

a calculation unit configured to calculate a high frequency steering torque change rate, which is the rate of change in the high frequency steering torques over time;

a band frequency output unit configured to input the high frequency steering torque change rate to a band pass filter that passes a first frequency band including the first frequency, so as to output a first frequency band steering torque change rate; and

a compensation unit configured to compensate an assist current of a steering motor on the basis of a rejection gain corresponding to the first frequency and the first frequency band steering torque change rate,

wherein when a frequency has a value of being equal to or smaller than a first frequency threshold value, the rejection gain is defined as a value of “1”, when a frequency has a value exceeding the first frequency threshold value and being equal to or smaller than the second frequency threshold value, the rejection gain is inversely proportional to the frequency and defined as a value between “1” and “0”, and when the frequency exceeds the second frequency threshold value, the rejection gain is defined as a value of “0”,

wherein the steering control apparatus further comprises:

a second sensing unit configured to sense a vehicle speed using a vehicle speed sensor, wherein the compensation unit compensates the assist current on the basis of the rejection gain, the first frequency band steering torque change rate, and a speed gain corresponding to the vehicle speed, wherein, when the vehicle speed has a value of being equal to or smaller than a first speed threshold value, the speed gain is defined as a value of “0”, and when the vehicle speed has a value exceeding the first speed threshold value, the speed gain is defined as being proportional to the vehicle speed, and

wherein the steering control apparatus further comprises:

a third sensing unit configured to sense a steering angle using an angle sensor, wherein the compensation unit compensates the assist current on the basis of the rejection gain, the first frequency band steering torque change rate, and an angle gain corresponding to the steering angle, wherein, when the steering angle has a value of being equal to or smaller than a first angle threshold value, the angle gain is defined as a value of “1”, when the steering angle has a value exceeding the first angle threshold value and being equal to or smaller than a second angle threshold value, the angle gain is inversely proportional to the frequency and defined as a value between “1” and “0”, and when the steering angle has a value exceeding the second angle threshold value, the angle gain is defined as a value of “0”.

2. The steering control apparatus of claim 1 , further comprising:

a second sensing unit configured to sense a vehicle speed using a vehicle speed sensor,

wherein the high pass filter outputs the high frequency steering torques equal to or higher than a cut-off frequency corresponding to the vehicle speed.

3. The steering control apparatus of claim 2 , wherein the cut-off frequency is inversely proportional to the vehicle speed.

4. The steering control apparatus of claim 1 , further comprising:

a second sensing unit configured to sense a vehicle speed using a vehicle speed sensor,

wherein the high pass filter outputs the high frequency steering torques equal to or higher than a cut-off frequency corresponding to the vehicle speed, and

the compensation unit compensates the assist current on the basis of the rejection gain, the first frequency band steering torque change rate, and a speed gain corresponding to the vehicle speed.

5. The steering control apparatus of claim 1 , further comprising:

a second sensing unit configured to sense a vehicle speed using a vehicle speed sensor and a third sensing unit configured to sense a steering angle using an angle sensor,

wherein the compensation unit compensates the assist current on the basis of the rejection gain, the first frequency band steering torque change rate, a speed gain corresponding to the vehicle speed, and an angle gain corresponding to the steering angle.

6. The steering control apparatus of claim 5 , wherein the high pass filter outputs the high frequency steering torque equal to or higher than a cut-off frequency corresponding to the vehicle speed.

7. A steering control method comprising:

sensing a steering torque using a torque sensor;

inputting the steering torque to a high pass filter and outputting high frequency steering torques in which low frequency steering torques are eliminated;

detecting a first frequency corresponding to a maximum steering torque among the high frequency steering torques;

calculating a high frequency steering torque change rate, which is the rate of change in the high frequency steering torques over time;

inputting the high frequency steering torque change rate to a band pass filter that passes a first frequency band including the first frequency, so as to output a first frequency band steering torque change rate; and

compensating an assist current of a steering motor on the basis of a rejection gain corresponding to the first frequency and the first frequency band steering torque change rate,

wherein when a frequency has a value of being equal to or smaller than a first frequency threshold value, the rejection gain is defined as a value of “1”, when a frequency has a value exceeding the first frequency threshold value and being equal to or smaller than the second frequency threshold value, the rejection gain is inversely proportional to the frequency and defined as a value between “1” and “0”, and when the frequency exceeds the second frequency threshold value, the rejection gain is defined as a value of “0”,

wherein the steering control method further comprises:

sensing, by a second sensing unit, a vehicle speed using a vehicle speed sensor, wherein the compensation unit compensates the assist current on the basis of the rejection gain, the first frequency band steering torque change rate, and a speed gain corresponding to the vehicle speed, wherein, when the vehicle speed has a value of being equal to or smaller than a first speed threshold value, the speed gain is defined as a value of “0”, and when the vehicle speed has a value exceeding the first speed threshold value, the speed gain is defined as being proportional to the vehicle speed, and

wherein the steering control method further comprises:

sensing, by a third sensing unit, a steering angle using an angle sensor, wherein compensating of the assist current comprises compensating the assist current on the basis of the rejection gain, the first frequency band steering torque change rate, and an angle gain corresponding to the steering angle, wherein, when the steering angle has a value of being equal to or smaller than a first angle threshold value, the angle gain is defined as a value of “1”, when the steering angle has a value exceeding the first angle threshold value and being equal to or smaller than a second angle threshold value, the angle gain is inversely proportional to the frequency and defined as a value between “1” and “0”, and when the steering angle has a value exceeding the second angle threshold value, the angle gain is defined as a value of “0”.

8. The steering control method of claim 7 , wherein outputting of the high frequency steering torques comprises: outputting of the high frequency steering torques equal to or higher than a cut-off frequency corresponding to a vehicle speed.

9. The steering control method of claim 8 , wherein the cut-off frequency is inversely proportional to the vehicle speed.