Proposal of Novel Model for a 2 DOF Exoskeleton for Lower-Limb Rehabilitation

Abstract

Nowadays, engineering is working side by side with medical sciences to design and create devices which could help to improve medical processes. Physiotherapy is one of the areas of medicine in which engineering is working. There, several devices aimed to enhance and assist therapies are being studied and developed. Mechanics and electronics engineering together with physiotherapy are developing exoskeletons, which are electromechanical devices attached to limbs which could help the user to move or correct the movement of the given limbs, providing automatic therapies with flexible and configurable programs to improve the autonomy and fit the needs of each patient. Exoskeletons can enhance the effectiveness of physiotherapy and reduce patient rehabilitation time. As a contribution, this paper proposes a dynamic model for two degrees of freedom (2 DOF) leg exoskeleton acting over the knee and ankle to treat people with partial disability in lower limbs. This model has the advantage that it can be adapted for any person using the variables of mass and height, converting it into a flexible alternative for calculating the exoskeleton dynamics very quickly and adapting them easily for a child's or young adult's body. In addition, this paper includes the linearization of the model and an analysis of its respective observability and controllability, as preliminary study for control strategies applications.

Exoesqueleto para rehabilitación de miembro inferior con dos grados de libertad orientado a pacientes con accidentes cerebrovasculares

“…Otro de los modelos representativos de exoesqueletos se diseñó bajo quince figuras geométricas simples [19], [28], [29], las cuales conformaban el cuerpo humano usando el modelo de Hanavan. Hacen uso del programa Screws para representar el entorno físico del robot y de los posibles movimientos, considerándose hasta siete grados de libertad.…”

“…A partir de este trabajo y otros posteriores, se llegó a una implementación a escala de un exoesqueleto que permitió validar la cinemática y la dinámica de este sistema pero que no incluía el desarrollo a escala real ni el diseño ajustable a diversos pacientes. Posterior a estos desarrollos, se trabajó en la generalización del modelo biomecánico y en el análisis paramétrico del sistema para determinar la influencia de los parámetros en la cinemática y la dinámica del exoesqueleto para dos grados de libertad [28], [30], [35]. Otros trabajos de los autores, incluyen simulaciones de la cinemática de exoesqueletos para brazo humano considerando robots de tipo serial y paralelo [32], [33], [34].…”

“…Los parámetros del modelo son elementos variables y dependen del usuario, de tal manera que variaciones por ejemplo en las masas, distancias en cada eslabón e inercias pueden generar diferentes relaciones de torque para cada articulación como se muestra en [28].…”

Investigation of a Passive Ankle Joint Exoskeleton Designed for Movements with Dorsal and Plantar Flexion

“…Effective rehabilitation is a long-term process that also requires a trained physical therapist to help restore joint mobility. Therefore, robotics has been involved in rehabilitation therapy for constant patient observation and assisted motion [4].…”

Dynamic Analysis of Lower Limb Exoskeleton Motion and Control Using Differential Transform Method

“…Although progress has been made in such localized modeling using different analytical models, but challenges of modeling the entire human body has not received an adequate attention, no doubt because of the human body complex structure. In the current study, the Euler-Lagrange mechanics is applied to develop a model for a two degrees of freedom for lower limb exoskeleton in which the structure of the exoskeleton and the lower limb are considered as a unit, and modeled as a two-link pendulum using the kinematics and dynamics approach of the biomechanics of the lower limb as described in [26]. The resulting model is a set of coupled simultaneous nonlinear differential equations where each equation describes the dynamic behavior of each link of the proposed system.…”