Patent ID: 7953509

Claim:
A control method for a power assist apparatus that comprises a workpiece holding apparatus having a plurality of holding portions for holding a workpiece; an arm for supporting the workpiece holding apparatus; a joint portion for supporting the workpiece holding apparatus rotatably relative to the arm; a brake for restricting rotation of the joint portion; a control apparatus for controlling a state of restriction established by the brake; a plurality of pressing force detection sensors which are provided respectively in the plurality of holding portions and detect a pressing force acting on the workpiece held by the workpiece holding apparatus; and a dead man switch provided on the workpiece holding apparatus, wherein the control method comprises: a pressing force detection step in which the pressing force acting on the workpiece held by the workpiece holding apparatus is detected by the pressing force detection sensors, and a detection result is input to the control apparatus; a pressing force determination step in which the control apparatus determines whether or not the pressing force detected by the pressing force detection sensors exceeds a preset threshold; a dead man switch determination step in which the control apparatus determines whether or not the dead man switch is ON; and a brake release determination step in which the control apparatus determines whether or not to release rotation restriction applied to the joint portions by the brake in accordance with a detection result of the pressing force detection step, a determination result of the dead man switch determination step, wherein, in the pressing force determination step, the control apparatus determines whether at least one pressing force of a plurality of pressing forces detected by the pressing force detection sensors of the plurality of holding portions exceeds a preset first threshold, and determines whether a sum total of the plurality of pressing forces detected by the pressing force detection sensors of the plurality of holding portions exceeds a preset second threshold.