A brain controlled exoskeleton for the upper extremities: A user centered design to improve the quality of life of MND patients

Abstract

After a visit at a revalidation center in The Hague a design goal was established: Providing motor neuron disease (MND) patients with upper arm functionality to improve their quality of life. MND patients gradually lose function of their muscles, even their respiratory muscles. It has a severe impact on their own life, but also the lives of friends and family. The project involved the company Adjuvo Motion, a company that focuses on robotic rehabilitation of the upper extremities of post-stroke patients. A 4C analysis was done, which covered both the company’s internal strengths and weaknesses, as well as the external world in which the product would be placed. This analysis was concluded by a SWOT analysis, which helped to generate a direction for future product development. This direction was modularity. A patient that is not able to move his hand does not require a full exoskeleton, only one for the affected area. An MND patient and a physiotherapist were interviewed, which lead to the insight that the support of activities of daily living (ADL) is the most relevant design focus to regain some quality of life. Additionally, being able to partake in social interactions was also shown to be relevant. A design vision was devised, which served as the foundation for the ideation phase: “I want patients to be able to regain independence by allowing them to perform activities of daily living. But I don’t want to stop there. I want people to be able to retain the social values that are accompanied by arm movements. I want to accomplish this in a user friendly way.” After a brainstorm session with a group of six master students, it was concluded that an exoskeleton has the most potential to accomplish the design vision, as it allows the most versatile functionality that can closely mimic the human arm itself. The architecture of the exoskeleton has been covered in depth, revealing many potential technologies that can be used, including the electroencephalography (EEG). This is the measuring of electrical brain activity. The MND patient’s brain remains unaffected, allowing the EEG technology to circumvent the affected areas to generate the desired movement. The Emotiv EPOC was identified as the most valid candidate to do the EEG measurement with. Multiple concepts were created, which were evaluated using the weighted objectives method. With this method, the concepts are evaluated by looking at wishes for the concepts. Via an online questionnaire, ALS patients provided their input on what wishes are more important to them than others. The chosen concept provides elbow and hand functionality by using electric motors that pull cables, which are connected to the arms and fingers. A prototype was created, which supported elbow flexion and extension and it was controllable with the Emotiv EPOC. To validate the concept, three user tests were conducted, including one with an MND patient. The MND patient was able to control the prototype just by the thoughts of moving his arm. A successful result, although the research also showed a few points to improve for the final concept. The final concept is the Exoten, named so because it is more like an external tendon, than like an external skeleton. The Exoten consists of two arm modules, a waist band and an EEG baseball cap. The waist band contains the rechargeable battery, the electric motors that reel in the cables and the micro-controller. The Exoten currently supports the elbow movement and a gripping motion, but it also allows for future expansion of functionality. In its current state, patients would be able to perform some of the ADL, but also gain a new way to show affection to their loved ones. The arm modules can be worn beneath clothing, which is beneficial to its comfort and its accuracy. The proof of concept is there, but it requires several future steps to become a reliable product that the target group can use: - More user tests to verify and improve the concept further. - Work together with Emotiv to create a reliable and integrated EEG device. - Include more stakeholders such as health care professionals to validate the product proposition