Steering controller

1. A steering controller comprising:

a first shaft connected to a steering member, the steering member being configured to receive a steering torque which is inputted to the steering member by a driver;

a second shaft connected to the first shaft and that transmits the steering torque to a steerable wheel;

a first detector configured to detect a turning angle of the first shaft, the turning angle of the first shaft being defined as a first detection value;

a second detector configured to detect a turning angle of the second shaft, the turning angle of the second shaft being defined as a second detection value;

a torque detector disposed between the first shaft and the second shaft and configured to detect the steering torque, the steering torque being defined as a third detection value;

a power-steering device disposed on a side of the torque detector that is closer to the steerable wheel than the steering member and having an electric motor configured to output a supplemental torque that assists a steering of the steering member by the driver; and

a control section including

a first rotation angle calculator configured to calculate a first turning angle that is a turning angle of the first shaft based on the first detection value,

a second rotation angle calculator configured to calculate a second turning angle that is a turning angle of the second shaft based on the second detection value,

a steering torque calculator configured to calculate a steering torque detection value based on the third detection value,

a drive controller configured to control a drive of the electric motor based on the steering torque detection value,

a steering torque estimator that is configured to calculate a steering torque estimation value based on the first turning angle and the second turning angle, and

an abnormality determiner configured to determine abnormalities of the steering torque detection value based on the first turning angle and the second turning angle, and

by comparing the steering torque estimation value with the steering torque detection value, wherein

when the abnormality determiner determines that abnormalities exit in the steering torque detection value, the drive controller is configured to control the drive of the electric motor based on the steering torque estimation value instead of the steering torque detection value, and

the control section has a learning component configured to learn at least one of a conversion coefficient used for a calculation of the steering torque estimation value based on the first turning angle and the second turning angle or a zero point correction value based on the first turning angle and the second turning angle.

2. The steering controller of claim 1 , wherein

when a travel distance after a previous learning by the learning component is equal to or greater than a preset distance, or when a number of times of turning ON and OFF of an ignition switch after the previous learning is more than a preset number of times, the learning component is configured to re-learn at least one of the conversion coefficient or the zero point correction value.

3. The steering controller of claim 1 , wherein

the second detector is configured to detect an electric motor rotation angle detection value concerning a turning angle of the electric motor as the second detection value.

4. The steering controller of claim 1 , wherein

the steering torque calculator is configured to calculate plural steering torque detection values based on two third detection values, and based on (i) a comparison result of the plural steering torque detection values or (ii) on the first turning angle and the second turning angle, and

the abnormality determiner is configured to determine the abnormality in at least one of the plural steering torque detection values.

5. The steering controller of claim 4 , wherein

the drive controller is configured to control the drive of the electric motor based on the normal steering torque detection value.

6. The steering controller of claim 1 , wherein

when the abnormality determiner determines that abnormalities exist in the steering torque detection value, the drive controller is configured to control the drive of the electric motor so that the supplemental torque is outputted as an abnormal-time supplemental torque that is equal to or less than a normal-time supplemental torque which is a supplemental torque at a time when the steering torque detection value is normal.

7. The steering controller of claim 6 , wherein

the abnormal-time supplemental torque has a value which is calculated as a product of the normal-time supplemental torque and a predetermined coefficient that is equal to or less than 1.

8. The steering controller of claim 6 , wherein

the drive controller is configured to gradually decrease the supplemental torque at a time of having abnormalities.

9. The steering controller of claim 1 , wherein

when the abnormality determiner determines that abnormalities exist in the steering torque detection value, the drive controller is configured to control the drive of the electric motor so that the supplemental torque is outputted as a predetermined torque according to a steering direction of the steering member.

10. The steering controller of claim 1 , further comprising:

an abnormality notifier, in the control section, that is configured to notify the driver of abnormalities in the steering torque detection value when the abnormality determiner determines that the abnormalities exist in the steering torque detection value.

11. The steering controller of claim 1 , wherein

the second detector is configured to directly detect the turning angle of the second shaft.

12. The steering controller of claim 1 , wherein

the learning component is based on a difference between the first turning angle and the second turning angle, and based on the steering torque detection value.