Steering control system

1. A steering control system that is connectable to a motor configured to control a steering and a LAN (Local Area Network) and is allowed to receive a control signal for controlling the motor from the LAN is received, said steering control system comprising:

a main calculation unit that is directly connectable to the LAN via a LAN transceiver;

a motor drive circuit that is directly connected to the main calculation unit and configured to drive the motor;

a sub calculation unit that is directly connectable to the LAN via a LAN transceiver; and

a motor drive limiting unit that is directly connected to the sub calculation unit and the motor drive circuit, wherein the motor drive limiting unit is configured to limit a drive of the motor.

2. The steering control system according to claim 1 , wherein the sub calculation unit is configured to operate the motor drive limiting unit to limit the driving of the motor, based on at least information obtained from the LAN.

3. The steering control system according to claim 1 , wherein the main calculation unit and the sub calculation unit are connected via one common LAN transceiver to the LAN.

4. The steering control system according to claim 1 , wherein the main calculation unit and the sub calculation unit are configured to directly communicate to each other, and

wherein the sub calculation unit is configured to operate the motor drive limiting unit to limit the driving of the motor, based on a comparison result between a value based on at least information obtained from the LAN and a value sent from the main calculation unit.

5. The steering control system according to claim 1 , wherein the main calculation unit and the sub calculation unit are configured to directly communicate to each other, and

wherein the main calculation unit is configured to compute a control amount of the motor, based on at least information obtained from the LAN,

wherein the sub calculation unit is configured to compute a control amount of the motor, based on at least information obtained from the LAN, and

wherein the sub calculation unit is configured to operate the motor drive limiting unit to limit the driving of the motor, if the deviation between the control amount sent from the main calculation unit and the control amount computed by the sub calculation unit is greater than or equal to a predetermined value.

6. The steering control system according to claim 1 , wherein the sub calculation unit is configured to compute a drive direction of the motor, based on at least information obtained from the LAN, and to operate the motor drive limiting unit to inhibit the drive of the motor in an opposite direction to the computation result.

7. The steering control system according to claim 1 , wherein the main calculation unit and the sub calculation unit are configured to directly communicate to each other, and

wherein at least one of the main calculation unit and the sub calculation unit is configured to determine an abnormality of the LAN, based on a comparison result between a value received from the LAN by own calculation unit and a value received from the LAN and sent by other calculation unit.

8. The steering control system according to claim 1 , wherein the main calculation unit and the sub calculation unit are configured to directly communicate to each other, and

wherein each of the main calculation unit and the sub calculation unit is configured to determine the abnormality of the LAN, based on the comparison result between the value received from the LAN by own calculation unit and the value received from the LAN and sent by other calculation unit.

9. The steering control system according to claim 7 , wherein the main calculation unit is configured to control the motor without using information obtained from the LAN, if it is determined that the LAN is abnormal.

10. The steering control system according to claim 7 , wherein the sub calculation unit is configured to operate the motor drive limiting unit to limit the drive of the motor without using information obtained from the LAN, if it is determined that the LAN is abnormal.

11. The steering control system according to claim 1 , further comprising a torque detection unit configured to detect a steering effort of the driver,

wherein the main calculation unit and the sub calculation unit are configured to compute the control amount of the motor, based on an output of the torque detection unit and information obtained from the LAN.

12. The steering control system according to claim 11 , wherein the sub calculation unit is configured to:

compute at least the drive direction of the motor, based on information obtained from the torque detection unit and the LAN signal; and

operate the motor drive limiting unit to limit the driving of the motor in an opposite direction to the computation result.

13. The steering control system according to claim 12 , wherein the sub calculation unit is configured to change a drive limited area of the motor, based on information obtained from the LAN signal.

14. The steering control system according to claim 1 , further comprising a steering wheel angle detection unit configured to detect a steering wheel angle of the driver,

wherein the main calculation unit and the sub calculation unit are configured to compute a control amount of the motor, based on an output of the steering wheel angle detection unit and information obtained from the LAN.

15. The steering control system according to claim 1 , further comprising a motor position detection unit configured to detect the motor position,

wherein the main calculation unit and the sub calculation unit are configured to compute a control amount of the motor, based on an output of the motor position detection unit and information obtained from the LAN.