The present paper describes a power-assist robot arm that uses pneumatic artificial rubber muscles (PARMs) covered withexoskeleton suits to mimic the motion of biarticular muscles. One robot arm uses a single PARM, which assists the wrist and elbow joint of the user. This robot arm is linked to a waist belt through a suspender-like structure of three PARMs. PI control (Proportional Integral control), which is based on the pressure value from a balloon sensor, is used to achieve accurate power-assist motion, and the present study focuses on the motions associated with lifting an object. In order to evaluate the validity of the proposed power-assist robot arm, skin surface electromyography (EMG) signals of forearm muscles are measured during a lifting task and a follow-up questionnaire survey is conducted.

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We are attempting to develop therapeutic technology that individuals with substantial arm weakness and minimal hand function after stroke can use to improve their movement ability without the continuous presence of a rehabilitation therapist. We have developed a device called Therapy WREX (T-WREX) that is comprised of four main features: 1) a passive, gravity-balancing arm support (based on WREX ¿Wilmington Robotic Exoskeleton) that allows a wide range of arm motion 2) a grip sensor that detects even trace amounts of grasp 3) virtual reality exercises that simulate activities of daily living, and 4) software that provides feedback about task performance. Initial clinical testing indicates that chronic stroke patients can significantly improve their movement ability with T-WREX. We have also found that patients strongly prefer using T-WREX for therapy compared to conventional, self-directed, tabletop exercises. This paper reports the results of a follow-up survey conducted with 11 subjects to gain further understanding about the basis for this preference. The results suggest that subjects prefer T-WREX because it is more interesting, and because it allows them to be more successful with their movement attempts. Further, each of the four features of TWREX had significant value to the subjects, suggesting that their combination is synergistic.

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The aim of this paper is to arbitrarily modify the load force of any selected muscle by using an exoskeleton, thus enabling «pinpointed» motion support, rehabilitation, and training. An advanced dynamic model, called a musculoskeletal-exoskeletal integrated human model, is developed. The driving-forces of the pneumatic actuators are designated by a muscle force control algorithm using the integrated model. A prototype power-assisting system is developed using pneumatic rubber actuators. The feasibility of the muscle force control is analyzed from a view point of nonlinear programming. The validity of the method is confirmed by measuring surface electromyographic signals of related muscles.

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In the design of exoskeletons for gait rehabilitation, the choice of degrees of freedom (DoFs) is one of the main issues. The goal of this research is to evaluate the effect of availability of additional DoFs related to balance-keeping on the normality of walking. These additional DoFs are the horizontal translations of the pelvis and the frontal rotation of the hip. Measurements on the gait of ten healthy subjects showed that kinematics and EMG differ only slightly when these DoFs are blocked (and only the sagittal joint rotations are available), in the impedance-controlled LOPES exoskeleton. This shows that omitting the additional DoFs allows walking with close-to-normal motor control, and also that effects of waking in this robot per se overshadow the additional effects of the mentioned DoFs. All subjects however reported a more difficult and uncomfortable walking when the horizontal pelvis motions were blocked. An additional motivation for keeping the DoFs despite these results is that they allow implementation of balance training.

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The feasibility of using exoskeletons in the performance of a simple task is discussed. The exoskeleton device has a total weight of 33 lb when unsupported, and it has seven joints. A Fitts’ law paradigm was used to characterize the tradeoff between speed and accuracy for the task. The results of tests with five subjects are given

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