The authors derive the object-based effective stiffness of antagonistically actuated, backdrivable, parallel linkages and show how to use this result to synthesize the generalized input loads required to create a desired system stiffness. They investigate the open-loop stability characteristics of such antagonistically actuated systems as a simple four-bar linkage, a dual-arm system, and a multifingered hand. In addition, they compare object-based and joint-based load distribution schemes in terms of their effect on system stability and input load requirements for an overconstrained planar mechanism. These investigations show an extreme interdependence between system geometry, actuation mode, and stability.>

A modeling procedure for a completely general kinematic system and a stiffness formulation technique for antagonistically actuated systems are given, in a format which is directly applicable to the design of high-stiffness robotic manipulator controllers. The formulation is developed in terms of kinematic influence coefficients. This involves some generalization of an existing modeling technique so that hybrid manipulator systems (combinations of parallel and serial manipulator systems) can be systematically treated. Antagonistic stiffness, which is developed extensively, is seen to be very promising for the design and control of future manipulators with high precision requirements under various operational disturbances.>