Evaluación de funcionalidad de un exoesqueleto de mano en usuarios sanos

Abstract

Stroke is one of the major causes of disability in the world. Those who suffer from this condition acquire a disability that includes hemiparesis, loss of muscle movement and loss of sensation. For the treatment of these limitations, especially in the hand area, robotic equipment such as assistive exoskeletons have been implemented for the progressive recovery of motor function. Numerous studies describe the development of hand exoskeletons designed in Soft-Robotics for rehabilitation therapies of post-CVA patients and assistance in activities of daily living. Their design in soft materials features high compatibility with the human body, allowing the actuation system to be comfortable and with a low risk of painful strains and shearing. The PrExHand project (Affordable and Modular Prosthetics and Exoskeletons for Hand Rehabilitation and Assistance, IAPP18-19/264), developed by the Biomechatronics Research Center (CB) of the Escuela Colombiana de Ingeniería Julio Garavito in collaboration with University College London and financied by the Royal Academy of Engineering (RAE), seeks the creation of a low-cost, modular hand exoskeleton for hand rehabilitation and assistance in post-CVA individuals. The present project focused on the evaluation of the pneumatic action exoskeleton, manufactured with textile structures for hand rehabilitation. This project aims to evaluate the PrExHand exoskeleton in non-pathological users to determine its functionality and usability, and thus, to establish the improvement requirements to be implemented in a next version of the device. To meet this objective, the exoskeleton's actuation time and the maximum flexion angle reached by the exoskeleton were initially evaluated in order to analyze the user interference in the device's actuation. Subsequently, an evaluation protocol of functionality in interaction with healthy users was designed and executed, consisting of three functionality tests and an interaction questionnaire divided into two general questions, where the capacity of the device to perform the tasks assigned in each test and the users' satisfaction with it were analyzed. Additionally, the presence and repetition of compensatory movements generated by the user during the use of the exoskeleton was evaluated. Next, an evaluation protocol of the exoskeleton in interaction with post-CVA patients was designed for its future implementation, once the improvements established for the device within the present project had been made. These improvements were determined from the analysis of the device's functionality and usability. The results obtained indicated a time of 11 seconds of action to reach the maximum flexion of the device in interaction with a user. This was a considerably high value compared to the theoretical design requirements, due to the actuation speed of the air pump, which capacity is not sufficient to perform finger flexion in a time of 2 seconds. In addition, the exoskeleton decreased by 51.5 % the finger flexion capacity in interaction with users by allowing only 30.9° of inclination. Despite this, the functional analysis corroborated the device's ability to perform various tasks requiring strong and precise grips, lifting both large objects weighing 450 g and small objects such as paper clips and coins. The usability evaluation determined that users were satisfied with the size, weight and ease of placement of the exoskeleton, however, the decreased level of satisfaction with the functionality and ease of use of the exoskeleton established a point of improvement for both criteria. Additionally, the presence of compensatory movements during the execution of 88.8 % of the tasks and the evidence of mild injuries in the localized wrist area indicated another need for improvement in the design of the device in the adjustment of this area. Finally, with the design of the functionality evaluation protocol with post-CVA patients, the need for the design of a preliminary patient selection protocol was exposed to ensure that the target population can perform the assigned tasks and the risk of adverse events is decreased. From the development of this thesis it was concluded that the current version of the exoskeleton, although it has functionality in aspects such as the ability to grasp objects of different sizes and sufficient strength to lift daily life objects, it is necessary to implement design improvements such as reducing the actuation time, the use of sensors for the analysis of the range of motion achieved by the actuators and the implementation of a control system to increase the efficiency of the device.