Abstract
The world is ageing and this poses a challenge to produce cost-effective solutions that can keep elderly people independent and active by assisting them in daily living activities. In this regard, this paper presents a new control method to provide physical assistance for any of the user joints (e.g., hip, knee, elbow, etc.) as needed by the wearer, by means of an assistive non-medical single joint exoskeleton with a “harmonized controller” capable of providing assistance in a natural way, and varying the assistance as needed by the user performing some activity. The control method is aimed at exoskeletons to provide assistance to users facing difficulty in any activity such as walking, sit-to-stand, etc., and, other than providing assistance as needed, it can also reduce the muscular effort for a completely healthy user. Harmonized control uses exoskeleton-integrated force sensors and motion sensors to identify the user's intentions and the assistance level required, generating appropriate control signals for the actuators by implementing a simple PID controller. To verify the proposed harmonized-control technique, simulations using MATLAB/SIMULINK were performed for a single joint system. An experimental test rig for a single joint was also developed using MATLAB Xpc Target for real-time control. User tests were also carried out for the knee joint and the results obtained from simulations, experimentation and user tests are reported and discussed here. The results achieved to date and reported here show harmonized control to be a promising user-centric solution for the development of single joint assistive exoskeletons for support as needed by the user in daily living activities.
Highlights
Research and development in exoskeletons has picked up pace in recent years, and some of the exoskeleton products are already in the market or close to launch, such as the military application exoskeleton HULC from Lockheed Martin to allow soldiers to carry heavy weights on the battlefield [1], the HAL exoskeleton from Cyberdyne for rehabilitation and non-medical uses [2], ReWalk and Ekso for people with spinal cord injuries to allow them to walk on their own using crutches for control and stability from ReWalk [3] and Ekso Bionics [4], respectively
Most of the current research in exoskeleton control meth‐ ods either make use of electromyography (EMG) sensor signals to identify the intention of the person to move and provide physical assistance based on that data, or else imports conventional robotic methods to control the exoskeletons
The harmonized control method is for use in assistive exoskeletons that are worn by a user who is elderly, or a healthy adult who has full or weakened functionality, in order to perform daily living activities such as walking, sitto-stand, etc. or similar upper-body activities
Summary
Research and development in exoskeletons has picked up pace in recent years, and some of the exoskeleton products are already in the market or close to launch, such as the military application exoskeleton HULC from Lockheed Martin to allow soldiers to carry heavy weights on the battlefield [1], the HAL exoskeleton from Cyberdyne for rehabilitation and non-medical uses [2], ReWalk and Ekso for people with spinal cord injuries to allow them to walk on their own using crutches for control and stability from ReWalk [3] and Ekso Bionics [4], respectively. Non-medical assistive exoskeletons can be a cost-effective solution for the support of elderly persons who face difficulty in performing daily living activities such as walking, sit-to-stand, etc., and need care staff’s help. Most of the current research in exoskeleton control meth‐ ods either make use of electromyography (EMG) sensor signals to identify the intention of the person to move and provide physical assistance based on that data, or else imports conventional robotic methods to control the exoskeletons. EMGbased controllers for exoskeletons claim to provide good assistance, they are not practical for everyday use Another commonly used control method is model-based control, a few examples of which can be found in [10,11,12,13,14], and a good example of which is the BLEEX exoskeleton [10]. The technique and methodol‐ ogy will be discussed in detail, with simulation and experimental set-ups to test and verify the technique, as well as the results of the verification
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