Millions of physical disabilities, who have lost a hand or both hands, are in need of prosthetic hands not only for decoration but also for the functions to help them with basic daily activities. Although EMG prosthetic hands are being extensively studied to satisfy this need, most of them are too expensive to be economically available, difficult to operate and maintain by a user him/herself, or over heavy for longtime wearing. The aim of this study is therefore to develop a simplified EMG prosthetic hand (sim-EMGPH) to solve these problems. The sim-EMGPH consists of five parts: a lightweight robotic hand with two motors to realize the most frequent hand activities, a highly stretchable cosmetic glove with little load on the motors, an EMG measurement system including sensors with high wearability made of soft conductive materials, a controller implemented by a 32-bit microprocessor which performs EMG signal processing, pattern recognition, and motor control, and a human-friendly tablet interface for the user to operate the sim-EMGPH by him/herself. We manufactured three sim-EMGPHs for three subjects: two with congenital upper limb deficiency and one with upper limb amputation. Free task experiments showed that the subjects could operate the sim-EMGPHs by themselves to perform basic activities of daily living. Limitations revealed and improvement plans are also discussed in this paper.

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Prosthetic hands are desired by those who have lost a hand or both hands not only for decoration but also for the functions to help them with their activities of daily living (ADL). Prosthetic robotic hands that are developed to fully realize the function of a human hand are usually too expensive to be economically available, difficult to operate and maintain, or over heavy for longtime wearing. The aim of this study is therefore to develop a simplified prosthetic hand (sim-PH), which is to be controlled by myoelectric signals from the user, to realize the most important grasp motions in ADL by trading off the cost and performance. This paper reports the structure design of a two-DoF sim-PH with two motors to drive the CM joint of the thumb and the interlocked MP joints of the other four fingers. In order to optimize the structure, the model of the sim-PH was proposed based on which 7 sim-PHs with different structural parameters were manufactured and tested in a pick-and-place experiment. Correspondence analysis of the experimental results clarified the relationship between the hand functions and the shapes of fingers.

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