Abstract: A control unit (14) makes an end effector (10) compliant with respect to an x-axis and a y-axis which are perpendicular to a z-axis parallel to a direction in which a shaft (20) is moved for insertion and makes the end effector (10) produce a pressing force acting in a direction parallel to the z-axis to press the shaft (20) against an internally toothed disk (22). The control unit (14) moves the compliance center of the shaft (20) along a predetermined groping route in a state where the pressing force acting in the direction parallel to the z-axis is produced by the end effector (10). The shaft (20) gripped by the end effector (10) repeats radially outward movement from a position near the center of the center opening (22b) of the internally toothed disk (22) in different phases in an xy plane defined by the x-axis and the y-axis to find a position where the splines (20a) of the shaft (20) are able to engage the internal teeth (22a) of the outermost internally toothed disk (22).

Abstract: A control unit (14) makes an end effector (10) compliant with respect to an x-axis and a y-axis which are perpendicular to a z-axis parallel to a direction in which a shaft (20) is moved for insertion and makes the end effector (10) produce a pressing force acting in a direction parallel to the z-axis to press the shaft (20) against an internally toothed disk (22) . The control unit (14) moves the compliance center of the shaft (20) along a predetermined groping route in a state where the pressing force lo acting in the direction parallel to the i-axis ifs produced by the end effector (10). The shaft (20) gripped by the end effector (10) repeats radially outward movement from a position near the center of the center opening (22b) of the internally toothed disk (22) in different phases in an xy plane defined by the x-axis and the y-axis to find a position where the splines (20a) of the shaft (20) are able to engage the internal teeth (22a) of the outermost internally toothed disk (22).