Patent ID: 8425436

Claim:
A motion assistive device comprising a drive unit configured to aid or execute an operation of a joint, and a control unit configured to control the drive unit, the drive unit including: a motor configured to provide an inputted driving force; and a circuit board on which a controller is mounted, the controller producing a drive signal supplied to the motor based on a control signal sent from the control unit, wherein the controller includes: a motor monitoring unit configured to monitor an operational status of the motor; and a motor control unit configured to limit the drive signal supplied to the motor based on a result of monitoring by the motor monitoring unit in order to prevent an overload state of the motor; wherein the drive unit further includes: a case housing the motor; a rotating body housed within the case and having a circumferential surface that rotates relative to the case when the motor is driven; a fluorescent band disposed on and extending along the circumferential surface of the rotating body while inclined with respect to a circumferential direction of the rotating body; a light-emitting portion configured to irradiate the fluorescent band with light; a detecting unit that remains stationary relative to the case and includes a light-receiving surface opposite the fluorescent band, the detecting unit being configured to detect position information about the fluorescent band in an axial direction of the rotating body by receiving light emitted by the fluorescent band; and a calculating unit configured to calculate a relative rotation angle between the case and the rotating body based on the position information about the fluorescent band detected by the detecting unit.