Open-loop stability of overconstrained parallel robotic systems

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