Steering device and steering method

A steering device comprising:

• two motors each configured to generate a drive force that steers a steerable wheel of a vehicle;
• and
• two controllers respectively corresponding to the two motors, each of the two controllers being configured to individually control a corresponding one of the motors, wherein
• one of the two controllers is a first controller and the other one of the two controllers is a second controller,
• the first controller is configured to calculate a command value corresponding to a total torque that should be generated in the two motors,
• the command value is divided into individual command values using a changeable distribution ratio set for each of the motors, the individual command values respectively corresponding to the motors,
• the two controllers are configured to respectively supply the motors with current corresponding to the individual command values, and
• the steering device further comprising:
• a steering rod configured to steer the steerable wheel;
• two transmission mechanisms each configured to individually transmit the drive force of a corresponding one of the two motors to the steering rod;
• and
• an external controller arranged outside of the two controllers, wherein
• when an execution condition that has been preset for an anomaly detection process is satisfied, the external controller is configured to:
• set the distribution ratios of the command value to an uneven distribution ratio;
• interchange the set distribution ratios between the two motors;
• and
• detect an anomalous increase in friction of the transmission mechanisms by comparing a total value of current in the two motors prior to interchanging the distribution ratios with a total value of current in the two motors subsequent to interchanging the distribution ratios.

A steering method for individually controlling two motors each configured to generate a drive force that steers a steerable wheel of a vehicle, the steerable wheel being coupled to a steering rod, the steering rod being coupled to two transmission mechanisms each configured to individually transmit the drive force of a corresponding one of the two motors to the steering rod, and the steering method comprising:

• calculating a command value corresponding to a total torque that should be generated in the two motors;
• dividing the command value into individual command values using a changeable distribution ratio set for each of the motors, the individual command values respectively corresponding to the motors;
• respectively supplying the motors with current corresponding to the individual command value;
• and
• when an execution condition that has been preset for an anomaly detection process is satisfied,
• setting the distribution ratios of the command value to an uneven distribution ratio;
• interchanging the set distribution ratios between the two motors;
• and
• detecting an anomalous increase in friction of the transmission mechanisms by comparing a total value of current in the two motors prior to interchanging the distribution ratios with a total value of current in the two motors subsequent to interchanging the distribution ratios.