Diagnostic apparatus and diagnostic method for rotational angle sensor, and control apparatus for actuator

A diagnostic method of a rotational angle sensor, comprising the steps of:

• operatively coupling a processor to a rotational angle sensor;
• obtaining, with the processor two correlated signals, corresponding to a rotational angle, a reference value from the two correlated signals;
• and then
• diagnosing, with the processor, whether or not a failure has occurred in the rotational angle sensor based on whether or not a numerical value obtained from the two signals is within a predetermined range including the reference value, wherein
• the reference value is obtained during a learning process, during which multiple values of the reference value are measured, the multiple values including a lowermost value and an uppermost value, the lowermost value and the uppermost value defining the predetermined range,
• the reference value is obtained at each predetermined angle during the learning process,
• the lowermost value is smaller than the uppermost value,
• the predetermined range is obtained by taking a variation due to temperature characteristics, or a variation due to degradation into account, and
• the processor is configured to diagnose that the rotational angle sensor is normal when the numerical value is within the predetermined range, whereas processor diagnoses that a failure has occurred in the rotational angle sensor when the numerical value is out of the predetermined range.

A system comprising:

• an actuator;
• a rotational angle sensor;
• and
• a processor operatively coupled to the rotational angle sensor and to the actuator, wherein the actuator is configured to rotate a rotating body, the processor is configured to control the actuator so that an output value of the rotational angle sensor that outputs two correlated signals, corresponding to a rotational angle of the rotating body, converges to a target angle,
• wherein the processor is configured to diagnose whether or not a failure has occurred in the rotational angle sensor based on whether or not a numerical value obtained from the two correlated signals is within a predetermined range including a reference value obtained from the two correlated signals beforehand, wherein
• the reference value is obtained during a learning process, during which multiple values of the reference value are measured, the multiple values including a lowermost value and an uppermost value, the lowermost value and the uppermost value defining the predetermined range,
• the reference value is obtained at each predetermined angle during the learning process,
• the lowermost value is smaller than the uppermost value,
• the predetermined range is obtained by taking a variation due to temperature characteristics, or a variation due to degradation into account, and
• the processor is configured to diagnose that the rotational angle sensor is normal when the numerical value is within the predetermined range, whereas processor diagnoses that a failure has occurred in the rotational angle sensor when the numerical value is out of the predetermined range.