An Underactuated Gripper Based on Car Differentials for Self-Adaptive Grasping with Passive Disturbance Rejection
Published in In the proceedings of 2021 IEEE International Conference on Robotics and Automation (ICRA), 2021
Abstract:
Fig. 1. The introduced gripper consists of one base differential and two finger differentials to split the power from the motor to both fingers, and transfer the power to both proximal and distal phalanges, respectively. When one of the phalanges is in contact with the object, the differential mechanisms keep other joints moving thus achieving adaptability. These differentials combined with return springs also add a mechanical passive disturbance rejection to the gripper. For example, after the differential-based gripper grasps an object (a sphere in the figure) (a), unexpected external disturbance forces applied to the fingers can be rejected as fingers move coordinately keeping grasping posture (b). Once the disturbances are released (c), the fingers and grasped object are able to return to the original grasping position (d). Abstract-We introduce an underactuated differential-based robot gripper able to perform self-adaptive grasping with passive disturbance rejection. The gripper utilises three car differential systems to achieve self-adaptiveness with a single actuator: a base differential for distributing power from the motor to the fingers, and two independent finger differentials for controlling the proximal and distal joints. Linear and torsional springs are cleverly added to these differentials to allow the return of the fingers and the gripper-object system to equilibrium, thus enabling the gripper rejecting unexpected external forces applied to the fingers after securing a grasp. This novel design provides passive disturbance rejection without implementing complicated control systems and is the main contribution of this paper. Moreover, the differentials allow the gripper to perform not only self-adaptive power grasp but also precision grasp, provide it with a large force transmission efficiency, and facilitate the prediction of grasping position. We analyse the static model of the introduced differential system and evaluate the gripper design via four sets of experiments. Numerical and empirical results clearly demonstrate the viability of the proposed grasper.
Recommended citation:
Qiujie Lu, Jinhong Wang, Zhuang Zhang, Genliang Chen, Hao Wang, Nicolas Rojas, "An Underactuated Gripper Based on Car Differentials for Self-Adaptive Grasping with Passive Disturbance Rejection." In the proceedings of 2021 IEEE International Conference on Robotics and Automation (ICRA), 2021.