The Virtual Linkage: A Model for Internal Forces in Multi-Grasp Manipulation

W e propose a model t o characierize internal forces and moments during multi-grasp manipulation. The proposed approach i s based on construction of a physical model, called the virtual linkage, which is a closed chain mechanism thai represents the object being manipulated. Forces and moments applied at the grasp points of this linkage cause joint forces and torques at i ts actuators. When these actuators are subjected t o the opposing forces and torques, the virtual linkage becomes a locked structure. Internal forces in the object are then characterized by these forces and torques. This approach was used in a multi-arm robot sysiem to manipulate objects while performing accurate control of in temal forces.