A solid mechanics approach to robotic grasp analysis

Wrench space formulations and grasp quality measures based on wrench space are widely used in robotics community to evaluate the stability of robotic grasps. However, many simplifying assumptions are used in this approach in order to make the analysis feasible. For example, both the object and the hand are assumed to be rigid and the contacts are represented by their resultant forces and moments (wrenches), as a result of which most of the grasps identified by them fail in experiments. In this work, we discuss the discrepancies present in the wrench space analysis due to these assumptions and propose a Finite Element (FE)-based grasp synthesis methodology, which evaluates the grasp stability based on the well-established foundations of deformable solid mechanics. Using a spring-mass-damper model, we demonstrate the versatility of our FE-framework in analyzing the stability of robotic grasps during external perturbation. By performing several FE simulations of grasping an object of different masses, squeeze displacements and friction coefficients, we then study the influence of physical characteristics of object on grasp stability during perturbation. Finally, the most stable grasp is identified using our contact area-based metric, π.