Motor control device
A motor control device is configured to control a motor as a dynamic force source depending on a position of a rotation detection object that rotates while interlocking with the motor, the motor and the rotation detection object being included in a mechanical apparatus including a plurality of constituent elements that interlock with each other. The motor control device includes a computation circuit configured to compute an absolute rotation angle of the rotation detection object, using a relative rotation angle of a first constituent element of the mechanical apparatus that is detected through a relative angle sensor provided in the mechanical apparatus, and a rotation number conversion value resulting from converting an absolute rotation angle of a second constituent element of the mechanical apparatus that is detected through an absolute angle sensor provided in the mechanical apparatus, into a rotation number of the first constituent element.
1. A motor control device configured to control a motor depending on a position of a rotation detection object, the motor being a dynamic force source, the rotation detection object rotating while interlocking with the motor, the motor and the rotation detection object being included in a mechanical apparatus, the mechanical apparatus including a plurality of constituent elements that interlock with each other, the motor control device comprising:
a computation circuit configured to compute an absolute rotation angle of the rotation detection object, using a relative rotation angle of a first constituent element of the mechanical apparatus and a rotation number conversion value, the relative rotation angle of the first constituent element being detected through a relative angle sensor that is provided in the mechanical apparatus, the rotation number conversion value being a value resulting from converting an absolute rotation angle of a second constituent element of the mechanical apparatus into a rotation number of the first constituent element, the absolute rotation angle of the second constituent element being detected through an absolute angle sensor that is provided in the mechanical apparatus, wherein
the computation circuit includes a correction processing unit configured to correct the rotation number conversion value, based on comparison between the relative rotation angle of the first constituent element and a rotation angle conversion value, on a premise that a difference between the relative rotation angle of the first constituent element and the rotation angle conversion value is within a rotation angle equivalent to half rotation of the first constituent element and that the relative rotation angle of the first constituent element is correct, the rotation angle conversion value being a value resulting from converting a rotation angle correspondence value into the relative rotation angle of the first constituent element, the rotation angle correspondence value corresponding to the relative rotation angle of the first constituent element that is obtained when the rotation number conversion value is evaluated.
2. The motor control device according to claim 1 , wherein:
the computation circuit includes
a first conversion unit configured to compute a first rotation angle conversion value resulting from converting the absolute rotation angle of the second constituent element into the relative rotation angle of the first constituent element based on a reduction ratio between the first constituent element and the second constituent element, and
a second conversion unit configured to compute the rotation number conversion value by dividing the first rotation angle conversion value by 360°, 360° being a rotation angle equivalent to one rotation of the first constituent element; and
the correction processing unit includes
a first processing unit configured to separate the rotation number conversion value into an integer part and a decimal part as the rotation angle correspondence value, the integer part corresponding to the rotation number of the first constituent element, the decimal part corresponding to the relative rotation angle of the first constituent element,
a second processing unit configured to compute a correction value for the integer part, based on comparison between the relative rotation angle of the first constituent element and a second rotation angle conversion value, in view of the premise, the second rotation angle conversion value being a value resulting from transforming the decimal part into the relative rotation angle of the first constituent element, and
a third processing unit configured to compute a final rotation number of the first constituent element by adding a value of the integer part and the correction value, the final rotation number of the first constituent element being used for the computation of the absolute rotation angle of the rotation detection object.
3. The motor control device according to claim 1 , wherein
the computation circuit includes
a rotation number computation unit configured to compute the rotation number of the first constituent element based on the relative rotation angle of the first constituent element that is detected through the relative angle sensor,
a subtractor configured to compute a correction value for the rotation number of the first constituent element that is computed by the rotation number computation unit, by subtracting the rotation number of the first constituent element that is computed by the rotation number computation unit, from a final rotation number that is computed by the correction processing unit, and
an absolute angle computation unit configured to compute the absolute rotation angle of the rotation detection object, based on the relative rotation angle of the first constituent element that is detected through the relative angle sensor and a final rotation number of the first constituent element after the correction value is reflected in the rotation number of the first constituent element that is computed by the rotation number computation unit.
4. The motor control device according to claim 1 , wherein:
the first constituent element is an assist motor configured to generate a steering assistance force, the steering assistance force being a torque that is given to a steering mechanism of a vehicle and that is in the same direction as a steering direction;
the second constituent element is a pinion shaft that engages with a turning shaft, the turning shaft being a shaft by which a turning wheel of the vehicle is turned; and
the rotation detection object is a steering shaft that is coupled to the turning shaft through the pinion shaft.
5. The motor control device according to claim 1 , wherein:
the first constituent element is a reaction motor configured to generate a steering reaction force, the steering reaction force being a torque that is given to a steering shaft and that is in an opposite direction of a steering direction, dynamic force transmission between the steering shaft and a turning shaft being separated, the turning shaft being a shaft by which a turning wheel of a vehicle is turned;
the second constituent element is a pinion shaft that engages with the turning shaft; and
the rotation detection object is the steering shaft.
6. The motor control device according to claim 1 , wherein:
the first constituent element is a turning motor configured to generate a turning force that is given to a turning shaft and by which a turning wheel of a vehicle is turned, the turning shaft being a shaft by which the turning wheel of the vehicle is turned;
the second constituent element is a first pinion shaft that engages with the turning shaft; and
the rotation detection object is a second pinion shaft that engages with the turning shaft.