General formulation for force distribution in power grasp

A general formulation of the force distribution equations for three-dimensional power grasp is presented. It allows for any number of contacts on the finger surfaces and the palm. The formulation not only includes the active forces and moments applied at the contacts, but also the passive forces resulting from frictional and geometric constraints, such as wedging effects. A grasp matrix is developed for the power grasp case and a new approach is taken to define the hand Jacobian matrix. Contact conditions are modeled to consider both constrained and unconstrained directions for the forces. A stability analysis for power grasp is performed in order to evaluate its stability properties. Due to the inherently stable nature of power grasps, the main objective is not the determination of optimum contact locations, but is the determination of joint torques for optimum force distribution. The stability region is defined and used as a measure to study and compare the different stability aspects of power grasps. Results of stability analysis for power grasps, using the DIGITS Grasping System as a model, are also provided