Abstract: A rotation angle detection apparatus includes a driving gear, two driven gears, two sensors, and an arithmetic circuit. The two driven gears have different numbers of teeth and each are in mesh with the driving gear. The arithmetic circuit is configured to compute a rotation angle of the driving gear based on the rotation angles of the two driven gears, detected through the two sensors. The arithmetic circuit is configured to, when a relationship between the rotation angles of the two driven gears, detected through the two sensors, is different from the relationship when the rotation angle of the driving gear, computed by the arithmetic circuit, is normal, detect an abnormality in the rotation angle of the driving gear, computed by the arithmetic circuit.

Abstract: 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.

Abstract: A rotation angle detection apparatus includes a driving gear, two driven gears, two sensors, and an arithmetic circuit. The two driven gears have different numbers of teeth and each are in mesh with the driving gear. The arithmetic circuit is configured to compute a rotation angle of the driving gear based on the rotation angles of the two driven gears, detected through the two sensors. The arithmetic circuit is configured to, when a relationship between the rotation angles of the two driven gears, detected through the two sensors, is different from the relationship when the rotation angle of the driving gear, computed by the arithmetic circuit, is normal, detect an abnormality in the rotation angle of the driving gear, computed by the arithmetic circuit.

Abstract: 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.