Patent US 4,882,837

A precision automatic assembly apparatus for inserting an insertable part into a hole formed in a member includes a movable hand incorporating a movable body to which the insertable part is attached, and an electromagnetic wrist mechanism having a plurality of electromagnetic devices including air core coils and magnetic poles for supporting the movable body and controlling the movable body along a plurality of axes. When the part is inserted into the hole formed in the member, an external force which acts upon the part and the position of a point at which the part contacts the member are estimated by a control unit via position sensing means incorporated in the hand. Currents supplied to the excitation coils of the electromagnetic devices are controlled on the basis of the estimate to adjust the state (position and attitude) of the insertable part, whereby the part is fitted into the hole smoothly and automatically.