MPJ Hand: A self-adaptive underactuated hand with flexible fingers of multiple passive joints

Abstract

This paper developed a self-adaptive robotic hand with novel flexible fingers of multiple passive joints, called MPJ hand, whose main mechanism is based on the linkage-style parallel and self-adaptive finger in SARAH Hand, can perform parallel pinching grasp and self-adaptive encompassing grasping modes with relatively even force distribution. A MPJ hand is developed with three MPJ fingers and 45 degrees of freedom (DOFs). Each MPJ finger has three phalanxes, mainly consists of an actuator, and accelerative gear system, springs, four-link mechanicals and unidirectional phalanx unit. This kind of phalanx can deform in one direction under the action of force and in the opposite direction it is rigid and cannot have any deformation due to the limiter. The grasping process of the MPJ finger was discussed, kinematic analysis was performed by Denavit-Hartenberg (D-H) method and mathematic model was established for force analysis. Kinematics and mathematic model show the distribution of contact forces and compare the MPJ finger with the traditional rigid fingers. Simulation and experimental results show the even grasping force distributions and the versatility of the MPJ hand. The MPJ hand has a wide range of applications.