On Adaptive Grasp with Underactuated Anthropomorphic Hands

To automatically adapt to the shape of different objects with enough grasping force is a challenge in the design of underactuated anthropomorphic hands, because the grasped object is easily ejected from the hands during underactuated grasping process. The goal of this paper is to develop a design method of underactuated anthropomorphic hands to guarantee reliable adaption to different grasped objects. An analysis method is developed to investigate the evolution of motion and force in the whole underactuated grasping process. Based on the evolution of motion and force, the underactuated grasping process is decomposed into four aspects including initial contact state, grasp terminal state, grasp trajectory and rate of progress. Moreover, the influence factors of such four aspects are found as the form of the combinations of underactuated mechanism parameters. According to the four aspects of the underactuated grasping process, this paper presents a stepwise parameter design method through optimization of parameter combinations step-by-step. The reliable adaptive grasp for a wide scale of grasped object size is achieved. Experimental setups are constructed to corroborate the results from the theory analysis and design.