An Interface between an Exoskeletal Elbow Motion Assistance Robot and the Human Upper Arm

Abstract

We have been developing exoskeletal motion assistance robots for human motion support to help physically weak persons. Since elbow motion is one of the simplest and most important motion in daily activities, we have developed a exoskeletal robot for human elbow motion assistance. In this system, the angular position and impedance of the exoskeletal robot are controlled by multiple fuzzy-neuro controllers. Skin surface electromyography (EMG) signals and wrist force by the human subject during elbow joint motion have been used as input information for the controller. Since the activation of working muscles tends to vary with the human subject's upper arm posture, we propose an interface that cancels out the effect of posture changes of the human subject's upper arm. Experimental results show the effectiveness of the proposed interface.

Development of a wearable exoskeleton for daily forearm motion assist

“…Some parts of the architecture (i.e. the architecture for the elbow flexion-extension motion assist) are the same as those in our previous study [1,2]. The exoskeleton consists of two links, two DC motors, a ballscrew drive shaft, a ballscrew support frame, a driving wire, a wrist frame, an inner and an outer wrist holder, a wrist cover, potentiometers and a wrist force sensor.…”

“…In order to generate the elbow flexion (or extension) motion, link-2 is flexed (or extended) by contracting (or expanding) the prismatic joint along the ballscrew drive shaft in the ballscrew support frame, which is attached to link-1, using the DC motor on the top of the ballscrew support frame [1,2]. The forearm pronation-supination motion (the rotational motion of the wrist cover with respect to the wrist frame) is generated by a wire that is driven by the other DC motor as shown in Fig.…”

“…We have been developing robotic exoskeletons [1 -4] to assist the motion of physically weak persons (patients) for the purpose of rehabilitation and daily use. So far, exoskeletons for elbow motion [1,2], shoulder motion [3], upper-limb motion (shoulder and elbow motion) [4,5] and lower-limb * To whom correspondence should be addressed. E-mail: kiguchi@ieee.org 752 K. Kiguchi et al motion [6,7] assist have been proposed for daily use and rehabilitation for the patients.…”

“…Moreover, physiological conditions, such as fatigue, affect the activity level of EMG signals [14]. EMG signals are also affected by arm posture, since the role of each muscle is changed according to the arm posture [2]. Therefore, it is not easy to apply EMG signals of muscles of the forearm and upper arm as input signals to the controller of the exoskeleton.…”

“…Thus, the proposed control method enables cooperative elbow and forearm motion of the patient by learning the muscle activation patterns of each patient, although some muscles are used for both elbow motion and forearm motion. In order to eliminate the problems caused by changing the arm posture, multiple neuro-fuzzy controllers [2], which are switched in accordance with the elbow angle, are prepared in this study.…”