A hybrid position/force control scheme for the control of two force constrained cooperating robots transporting a workpiece

Includes bibliographical references (pages [108]-109)The coordination of two robots transporting a workpiece jointly, needs a certain form of hybrid position/force control. In this thesis an efficient hybrid position/ force control scheme for the control of two cooperating robots transporting a work- piece is developed. This is done by first transforming the end-effector forces to a net force and moment in the center of mass of the workpiece and then comparing the position, angle, force and moment of the workpiece to their desired values in the task space. These task space errors are then transformed to joint space where the control execution takes place. The control problem is solved as a design problem for an almost linear system by compensating the centrifugal, coriolis and gravity forces and introducing velocity controllers at the joints. The velocity controllers ensure the stability of the system in the face of inadequate compensation. This control scheme allows for various types of tasks to be achieved using the same control structure by planning the appropriate force and position trajectories in the task space.M.S. (Master of Science