Yinlai Jiang

Development and evaluation of simplified EMG prosthetic hands

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.

A low-degree of freedom EMG prosthetic hand with nails and springs to improve grasp ability

There are millions of people who have lost a hand or both hands due to acquired amputation or congenital limb deficiencies. In order to improve their quality of life, electromyogram (EMG) prosthetic hands have been developed to compensate for some daily activities which a cosmetic glove cannot do. However, most EMG prosthetic hands pursue the ability of motions by multi-degree of freedom mechanisms that lead to the shortcomings, such as low intensity, high cost, overweight, and maintenance difficulties at the same time. The development of low-degree of freedom EMG prosthetic hand with high performance is therefore very practical and important. We have developed an EMG prosthetic hand with two motors to realize the rotary motions which account for 85% hand motions in daily life. In this study, we improve the mechanism of the hand with springs to connect the fingers to the palm and artificial nails equipped on top of the fingers. Experimental results show a significant improvement of grasp ability, especially for the tiny objects.

Tendon drive finger mechanisms for an EMG prosthetic hand with two motors

EMG prosthetic hands are being extensively studied to meet with the need of the millions of physical disabilities who have lost a hand or both hands. But for most of existing multi-degree of freedom EMG prosthetic hands, shortcomings such as low intensity, high price, et al., have blocked them from practical realization. Low-degree freedom EMG prosthetic hand with high performance is therefore desired to solve these problems. The aim of this study is to optimize the low-freedom degree EMG prosthetic hand based on utilization rate of human hands joints in daily life. We used two motors to realize the rotary motions of CM joints and three kinds of tendon drive mechanism of MP joints. The low-freedom degree EMG prosthetic hand can also complete powerful grasp, precise grasp and lateral grasp which account for 85% hand motions in daily life. Stress analysis is also performed to guarantee safety in daily use. Finally, a pick-and-place experiment was conducted to evaluate the designs.

Structure design for a Two-DoF myoelectric prosthetic hand to realize basic hand functions in ADLs

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.

Pinch-force-magnification mechanism of low degree of freedom EMG prosthetic hand for children.

EMG prosthetic hands are being extensively studied for the disabled who need them not only for cosmesis but also for the functions to help them with basic daily activities. However, most EMG prosthetic hands are developed for adults. Since the early use of prosthetic hands is important for the children to accept and adapt to them, we are developing low degrees of freedom (DoF) prosthetic hand that is suitable for children. Due to the limited size of a childs hand, the servo motor which drives the MP joint are small-sized and low-power. Hence, a pinch-force-magnification mechanism is required to improve the pinch force of the EMG prosthetic hand. In this paper we designed a wire-driven mechanism which can magnify pinch force by increasing the length of the MP joints moment arm. Pinch force measurement experiment validated that the pinch force of the prosthetic hand with the mechanism is more than twice of that of the hand with direct drive.

A highly usable and customizable sEMG sensor for prosthetic limb control using polypyrrole-coated nonwoven fabric sheet

A novel sEMG (surface electromyography) sensor using polypyrrole-coated nonwoven fabric sheet as electrodes (PPy-electrode) is proposed for the disabled to control prosthetic limbs in daily life. The PPy-electrodes are sewed on an elastic band to guarantee closely contact to the skin thus to enable stable sEMG measurement with high signal-to-noise ratio. Furthermore, the sensor is highly customizable to fit for the size and the shape of the stump so that the disabled can wear the sensor by themselves. The performance of the proposed sensor is investigated by comparing with Ag/AgCl electrodes with electrolytic gel in an experiment to measure the sEMG from the same muscle fibers. The high correlation coefficient (0.84) between the sEMG measured by the two types of sensors suggests the effectiveness of the proposed sensor. The experiment of sEMG patter recognition to control myoelectric prosthetic hands showed that the PPy-electrodes are as effective as Ag/AgCl electrodes to measure sEMG signals for practical myoelectric control.

One-Handed Wearable sEMG Sensor for Myoelectric Control of Prosthetic Hands

A novel sEMG (surface electromyography) sensor using polypyrrole-coated nonwoven fabric sheet as electrodes (PPy-electrode) is proposed for the disabled to control prosthetic limbs in daily life. The PPy-electrodes are sewed on an elastic band to guarantee closely contact to the skin thus to enable stable sEMG measurement with high signal-to-noise ratio. Furthermore, the sensor is highly customizable to fit for the size and the shape of the stump so that the disabled can wear the sensor by themselves. The performance of the proposed sensor is investigated by comparing with Ag/AgCl electrodes with electrolytic gel in an experiment to measure the sEMG from the same muscle fibers. The high correlation coefficient (0.87) between the sEMG measured by the two types of sensors suggests the effectiveness of the proposed sensor. The experiment to control myoelectric prosthetic hands showed that the disabled can use it with one hand to obtain sEMG signals for myoelectric control.

Development of New Cosmetic Gloves for Myoelectric Prosthetic Hand by Using Thermoplastic Styrene Elastomer

This paper reports on design and development of new cosmetic gloves for Myoelectric Prosthetic Hand which provides a realistic appearance and flexible motion of robot hands. The main design issues are divided into five as followings; appearance, gripping performance, durability, texture, flexibility. The appearance includes the shape, wrinkles, finger mark, nail, and color of the hand; the aim is to make these properties of the prosthetic hand as similar to those of the human hand as possible. The durability is evaluated by adaptabilities for daily living, and flexible materials without prevention from finger motion. Furthermore, the gripping performance is improved by the thickness map of palm which is well fit to the gripping object. The experiment shows the results of the performance test applied to the pick-and-place task by using powered prosthetic hand in order to evaluate total properties of the developed cosmetic gloves.

Approximate model for interactive-tendon driven mechanism of a multiple-DoFs myoelectric prosthetic hand

For practical use, a myoelectric prosthetic hand needs to (1) have a human-like structure, (2) be lightweight, (3) have multiple degrees of freedom (DoFs), and (4) have a high grip force. We have developed a myoelectric prosthetic hand with an interactive-tendon driven mechanism. This paper describes the control method by which the interactive-tendon driven mechanism produces fine and precise actions, as well as an approximate model for the control method. The approximate model was developed based on a geometry model and an equilibrium model for the joint torque. Experimental results show that the joint motions of the actual robotic hand are controlled with errors of between 9 and 15% using the approximate model.

Development of new cosmetic gloves for myoelectric prosthetic hand using superelastic rubber

Abstract This paper reports on the design and development of new cosmetic gloves made of two different superelastic rubbers – thermoplastic styrene elastomer (TSE) and silicone rubber (TSG silicone) – and compares them with gloves made of polyvinyl chloride (PVC) for myoelectric prosthetic hands to realize a realistic appearance and flexible motion. The materials are compared in terms of their appearance, material, mechanical, and sensing properties. Appearance properties include the shape, wrinkles, fingerprints, texture, nail, and color of the hand; these properties are designed so as to produce a prosthetic hand that looks similar to a human hand. The material properties are evaluated in terms of adaptability for daily living without preventing finger motions of the powered hand by performing a tear strength test. Mechanical properties are improved by designing the thickness of the palm to grip an object. The sensing properties are essential for acquiring information about the object and the environment. The overall performance is evaluated through a material engineering test and a pick-and-place test with a powered prosthetic hand. Tear strength comparisons showed that TSE and TSG silicone could respectively withstand 5–7 and 3 times the strain that PVC could withstand before breakage. The TSE glove shows the highest stretching length before breaking and shows high flexibility even after breaking. The electric currents during EMG prosthetic hand motion showed that TSE and TSG silicone gloves successfully reduced energy consumption by around one-third for many hand movements. Flexibility test results for the maximum opening posture showed that the PVC glove greatly restricted the hand opening width. However, the differences between the cases without and with TSE gloves were very small; therefore, both cases show the same range of motion. The flexible TSE facilitated easy fitting and therefore had the lowest fitting time; in fact, it can be worn in one-third the time required for wearing PVC or TSG silicone gloves. In pick-and-place experiments, TSG silicone and TSE gloves both showed similar results for successfully grasping objects. The TSE glove is hard to break and has high elasticity; therefore, nails can be added to it. Furthermore, TSG resin is thermosetting and can be processed at room temperature, making it easy to impart conductivity. Therefore, the TSG silicone material is more suitable for implementing a sensor.