Yoshiko Yabuki

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.

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.

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.

Engineering Approach for Functional Recovery Based on Body Image Adjustment by Using Biofeedback of Electrical Stimulation

This chapter reports on a biomedical robotic collaborative approach for neuroprosthesis based on body image adjustment. The body image and homunculus show a stable relationship between the brain and a sensor and the motor allocation of the human body. The body schema conceptually explains the relationship between the brain and the body movement. In recent times, a novel concept of functional recovery of motion based on biofeedback to connect the intentions of motion and the sensory input has attracted considerable attention. This chapter describes adaptable EMG prosthetic hand experiments that show that the sensory motor cortex indicates the human intentions of motion through synchronized proprioceptive sensor inputs. This illusion induces strange activities in the sensory motor area according to the synchronous biofeedback. Biofeedback using an interference-driven electrical stimulation (ES) device is proposed, and the experimental results show that the somatic reflex stimulation realizes muscular control and neural rehabilitation in patients with sensor–motor coordination disruption. Furthermore, the proposed device can be applied for the rehabilitation of paralysis due to stroke; it has functions for changing the stimulation parameters and controlling many channels in order to adapt to various types of paralysis and to support complex movements such as grasping, standing, and walking. For neuroprosthesis applications, the desired relationship between the stimulation and intention of motion is synchronous and can be controlled by using an electrical switch to control the ES.

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.

Development of a Parent Wireless Assistive Interface for Myoelectric Prosthetic Hands for Children

In this study, a one-degree-of-freedom myoelectric prosthesis system was proposed using a Parent Wireless Assistive Interface (PWAI) that allowed an external assistant (e. g., the parent of the user) to immediately adjust the parameters of the prosthetic hand controller. In the PWAI, the myoelectric potential of use of the upper limb was plotted on an external terminal in real time. Simultaneously, the assistant adjusted the parameters of the prosthetic hand control device and manually manipulated the prosthetic hand. With these functions, children that have difficulty verbally communicating could obtain properly adjusted prosthetic hands. In addition, non-experts could easily adjust and manually manipulate the prosthesis; therefore, training for the prosthetic hands could be performed at home. Two types of hand motion discrimination methods were constructed in this study of the myoelectric control system: (1) a threshold control based on the myoelectric potential amplitude information and (2) a pattern recognition of the frequency domain features. In an evaluation test of the prosthesis threshold control system, child subjects achieved discrimination rates as high as 89%, compared with 96% achieved by adult subjects. Furthermore, the high discrimination rate was maintained by sequentially updating the threshold value. In addition, a discrimination rate of 82% on average was obtained by recognizing three motions using the pattern recognition method.

Force-magnification mechanism with artificial tendon sheath for myoelectric prosthetic hand for children

Myoelectric prosthetic hands (MPH) for children are being studied to meet with the need of children with upper limb deficiency. The MPH for children developed in a previous study was lack of stability and mechanical adaptability, and could not be controlled to meet with variable scenes in real life. We therefore developed a steady mechanism to ensure its mechanical stability, and conducted a pick-and-place experiment to verify its practical performance. Furthermore, we designed a bionic mechanism to enhance its mechanical adaptability. The mechanism mimicking human ligaments of tendon sheath makes it possible that the MPHs finger can bend fast with small torque while approaching to the object, and slowly increase grasp torque after touching the object. To enable the mechanism to exert proper range of torque, the dynamics of the mechanism was analyzed. We also conducted a mechanics experiment to verify its mechanical adaptability.

Development of a Myoelectric Hand Incorporating a Residual Thumb for Transmetacarpal Amputees

Restoring the hand functionality of partial amputees requires a myoelectric prosthetic hand, which is a robotic hand controlled by myoelectric signals from the skin surface and has the potential to restore human hand functionality. Most myoelectric hands have been developed for forearm amputees, while those for partial-hand amputees are few in number despite the higher numbers of the latter. Partial-hand amputees have limited hand functionality and cannot grasp and manipulate various objects in a manner comparable to individuals with a healthy hand; thus, they require a myoelectric hand. In this study, design issues were identified, and three-dimensional computer-aided design was used to propose an integrated skeleton and housing with a supporting socket. A passive thumb mechanism with motion in the remaining part of the hand was developed where the motion control system is based on the amputee’s muscles. An amputation system is proposed comprising mixed metacarpal and center-part cuts. A prototype was constructed, and its gripping functionality was evaluated. The results demonstrated an enhanced gripping performance compared to the non-use of prosthetics, which attests to the viability and effectiveness of the system.

Live demonstration: Prosthetic hands controlled with a highly usable sEMG sensor

Two kinds of prosthetic hands, one is a multi degree-of-freedom (DoF) robotic hand (Fig. 1) using tendon-driven mechanism and the other is a two DoF robotic hand using direct drive mechanism (Fig.2), will be demonstrated. They are both developed to compensate the lost upper limb function.