Robot system employing force/position control

Claim 1

In a robotic assembly system including a robotic device composed of a base member, a plurality of movable members and joint means coupling the members in a sequence extending from the base member such that a first one of the movable members is supported by the base member and is rotatable relative to the base member about a respective axis and each of the other movable members is supported by, and rotatable about a respective axis relative to, a respective preceding movable member in the sequence, with the last movable member in the sequence being an end member for supporting a workpiece which is to be brought to a selected position relative to a fixed body by movement along a surface defining a reference plane associated with the body, the selected position corresponding to a set of reference angular positions each of which defines an angular position of a respective movable member about the respective axis thereof; computer driven displacement means coupled to the joint means for rotating each movable member about the respective axis thereof in a manner to bring the workpiece to the selected position while displacing the workpiece generally along the reference plane and pressing the workpiece against the surface defining the reference plane with a force approaching a selected value; first monitoring means associated with the end member and coupled to the displacement means for producing a signal representative of the force with which the workpiece is being pressed against the reference plane; and second monitoring means coupled to the joint means and the displacement means for providing signals indicating the current angular position of each movable member about the respective axis thereof, the improvement wherein said displacement means comprise means coupled to said joint means for effecting rotation of only one of said movable members in direct response to the signal produced by said first monitoring means.