Evaluation of Grasp Stiffness in Underactuated Compliant Hands Exploiting Environment Constraints

Exploiting underactuation and compliance in design and control of robotic hands represents a lively research topic. Reducing the actuators and increasing uncontrolled degrees of freedom, however may affect dexterity and control capabilities. Observing how humans use their hands in everyday grasping and manipulation tasks, it is evident that our “planner” is not always very precise, and we tend to use the environment to guide our finger trajectories to accomplish with the task. An interesting research challenge consists in providing also to robotics hands the ability of efficiently exploit environmental constraints. As a first step, it is necessary to extend to an augmented grasp system, including the hand, the object and the environment interaction, the main theoretical results and evaluation measures available for robotic grasping. In this paper we summarize an extended robotic grasp model including the interaction with the environment, and we apply to this system the evaluation of grasp stiffness. Some grasp evaluations for a simplified planar gripper are presented.