The loss of an upper limb dramatically affects a person's daily activities. Recent developments in bionics and prostheses make it possible to compensate this loss of functionality with a bionic robotic hand. These bionic hands are commercially available and can enable a person to perform multiple types of hand movements. Controlling a bionic hand is in most cases based on the interpretation of two surface electromyography (EMG) signals. To control the multiple degrees of freedom (DOF) of a robotic hand with only two EMG signals, a sequential control strategy is used. This sequential control strategy requires a lot of training from the user. Currently different strategies are being developed to enable a user friendly and more efficient type of control.
Most developments in the field of upper extremity prostheses are aimed at adults with a single arm reduction. Children with a double arm reduction are often unable to use the available prostheses and those that are available don't provide a solution for their specific needs. This project aims to integrate the most recent developments in prosthesis control and bionic robotics and make them available for children with a double arm reduction. The research is unique and novel because it aspires to develop and verify the use of non-invasive control strategies that enable children with a double or single arm reduction to control prostheses (with multiple DOF) outside of lab conditions.
This project is primarily focused on one user. Larrissa (anonymous name) is an 8-year-old Belgium girl that misses both hands and feet. At the age of 1,5 she lost both hands and feet due to illness. Because her current prosthesis (and all other prosthesis) isn't suited for a bilateral amputee and offers little functionality she remains highly dependent on the help of others.
The development was initiated in 2015 by Jos d'Haens (BAP physiotherapy, MOVANT) and was complemented with the master thesis of Erik Haring. This collaborative project between the department of Product Development and Rehabilitation sciences and physiotherapy at the Faculty of Medicine and Health Sciences resulted in a first prototype of a prosthetic socket, designed for Larissa. Jos d'Haens developed a miniaturised robotic hand that can perform three primary grip types. The compact dimensions make this bionic hand especially suitable for children. The prototype of the prosthetic socket (physical connection with the wearer) was the tangible output of the master thesis of Erik Haring. This project aims to provide the missing link, a user-friendly and intuitive control system that translates human input into desired movements of the robotic hand.
We defined two clusters of research questions within the project
1. Human input: Which signals can be captured within the stump of the child? Are these signals suitable to serve as input for an intuitive control strategy for the prosthesis?
2. Control strategy: How can we transform these signals into a user-friendly control strategy?
2.1 Focus on movements: Developing a prosthesis control strategy that enables the child to perform at least the three primary grip patterns: power grip, precision grip and lateral grip. With these three grips users can perform 80% of the most common daily activities.
2.2 Focus on intuitive use and user-friendliness: With the actual feedback of the child we aim for a control system that can activate at least three grip patterns in a user-friendly and intuitive way. Apart from a functional fit, we will gather user feedback on the social acceptance of the movements and look of the prosthesis.
We hope to apply and expand the knowledge and insights obtained from this study to other projects for young amputees. The methodology could serve as a basis for the development and design of similar intuitive and child friendly control strategies for prosthesis and assistive devices.