Underactuated Anthropomorphic Finger Mechanism for Grasping and Pinching with Optimized Parameter

Abstract

Problem statement: Underactuated finger mechanism is beneficial in the anthropomorphic applications in which it reduces the finger size, weight and power consumption due to the less number of actuators compared to its number of Degree Of Freedom (DOF). However, the currently existing underactuated finger is limited to grasping operations only and unable to pinch with the finger tip. Moreover, the behavior of such finger in achieving the desired configuration depends greatly on its geometric parameters. Therefore, this study presented a new bar linkage type underactuated finger mechanism with an optimized parameter set that resembled the human finger in performing both pinching and grasping operation. Approach: The existing seven bar linkage underactuated finger mechanism was modified by adding a guiding slot in the upper middle phalange link so that its length can be adjusted to achieve human finger’s configuration during pinching and grasping. A multiobjective optimization problem subjected to parameter constraints was then formulated using the evaluation criteria for human finger kinematics during pinching and grasping. Results: The numerical result obtained gave an improved set of geometrical parameter to achieve these configurations as it provided less error than the initial guess. Conclusion: A new underactuated finger mechanism that resembled the human finger to perform both pinching and grasping operation was presented in this study. The hardware fabrication will be carried out in the future using the optimized lengths obtained.