HyPro: A Multi-DoF Hybrid-Powered Transradial Robotic Prosthesis

This paper proposes a multi-DoF hybrid-powered transradial robotic prosthesis, named HyPro. The HyPro consists of two prosthetic units: hand and wrist that can achieve five grasping patterns such as power grasp, tip grasp, lateral grasp, hook grasp, and index point. It is an underactuated device with 15 degrees of freedom. A hybrid powering concept is proposed and implemented on hand unit of HyPro where the key focus is on restoration of grasp functions of biological hand. A novel underactuated mechanism is introduced to achieve the required hand preshaping for a given grasping pattern using electric power in the pregrasp stage and body power is used in grasp stage to execute the final grasping action with the selected fingers. Unlike existing hybrid prostheses where each of the joints is separately controlled by either electric or body power, the proposed prosthesis is capable of delivering grasping power in combination. The wrist unit of HyPro is designed and developed to achieve flexion-extension and supination-pronation using electric power. Experiments were carried out to evaluate the functionality and performance of the proposed hybrid-powered robotic prosthesis. The results verified the potential of HyPro to perform intended grasping patterns effectively and efficiently.

Grasping with the eyes

When observing someone else acting on an object, people implement goal-specific eye movement programs that are driven by their own motor representation of the observed action. Usually, however, we observe people acting in contexts where more objects, different in shape and size, are present. Is our brain able to select the intended target even when there are different objects in the visual scene? And if this is the case, what kind of information does our motor system capitalize on? We recorded eye movements while participants observed an actor reaching for and grasping one of two objects requiring two different kinds of grip to be picked up. In a control condition, the actor merely reached for and touched one of the two objects without preshaping her hand according to the target features. Results showed higher accuracy and earlier saccadic movements when participants observed an actually grasping hand than when they observed a mere reaching hand devoid of any kind of target-related preshaping. This clearly suggests that the hand preshaping provided the observer with enough motor cues to proactively and reliably saccade toward the object to be grasped, thus identifying it even when the action target was not previously known. Our findings strongly corroborate the direct matching hypothesis suggesting that in processing others' actions, we take advantage of the same motor knowledge that enables us to efficiently perform those actions.