Large Grasp Force Hand with High Compliance during High Speed Phase

Abstract

This paper presents a back-drivable two-fingered four-degree of freedom hand that can generate a large grasping force of 120 N and perform a high speed motion of larger than 750 °/s. All fingers are 98 mm in length and the weight of the hand is 1.2 kg. The hand can generate a large grasp force with a new force-magnification mechanism. The force-magnification mechanisms installed in our previous hands need a non-backdrivable element so that their high-speed drive mechanisms cannot be back-driven when the force-magnification mechanisms are activated, which results in low compliance. The new force-magnification mechanism in this paper uses a rack and pinion gear connection mechanism to establish the drive connection with the high-speed drive mechanism only when it is activated. Therefore, the high-speed drive mechanism can be back driven keeping high compliance. However, when the tooth crests of the rack hits that of the pinion gear, the connection mechanism is jammed. Therefore, a rack gear tilting mechanism is also proposed.