Displacements that null forces

Experimental results indicate that the inner product defined by stiffness does in fact provide the correct force-error nulling directions along which to move a robotic end-effector. These directions, which are defined as the twists of compliance, form the [K]-orthogonal complement to the twists of freedom of a partially constrained gripper (where the matrix [K] describes the stiffness of the robot and not its task). This implementation of kinestatic control is accomplished via the synthesis of two scalar gains to effect the six-dimensional, simultaneous control of force and displacement