A novel underactuated robotic finger for withstanding impacts of non-cooperative object capture

An underactuated robotic finger is proposed and studied for capturing non-cooperative objects, featuring an underactuated rigid-mechanism that can brake residual motion of non-cooperative targets. The finger consists of three joints driven by two actuators, and a set of one-input-two-output planetary gears is introduced to realize force transmission by using the ring gear and the planetary carrier to drive the two joints. The rotation of the ring gear and the planetary carrier are governed jointly by the inputs and the external force. In the process of capturing a moving target, the proposed robotic finger can effectively limit the impact force peak due to collision with the target. Moreover, the recovery time of the joint can be adjusted by changing the input torque of the motor, which can be set to achieve optimal recovery process for different tasks. A prototype has been built to study the proposed design of the robotic finger, and experimental results have confirmed its desirable characteristics.