Design of a Force-Isotropic Underactuated Hand

Underactuation in robotic hands is currently attractive for researchers. It reduces finger weight, size and power consumption and simplifies its control and maintenance due to using less number of actuators than number of Degrees Of Freedom (DOF). Instead of complex run-time algorithms, such hands use design-time analysis to improve their performances. In this paper a novel underactuated finger and a hand are proposed. The underacuation mechanism design is based on cam, tendon, ratchetgear and differential mechanism. Each finger has two DOF and hand has five fingers and one actuator. The main characteristic of this hand is to be force-isotropic. This means that the intensity of the forces exerted at the center of each phalanx, on the grasped object, are identical. So we have a uniform pressure on the grasped object to reduce the risk of failure. It is nearly absolute that, this characteristic has only been observed on some underactuated fingers, whereas, in this paper, the proposed hand has capability to apply a uniform pressure on the grasped objects. This hand is able to obtain a human-like grasping operation and it can be used either as a humanoid robot end effectors or prosthetic hand.