Mechatronics Design of a Gait-Assistance Exoskeleton for Therapy of Children with Duchenne Muscular Dystrophy

This paper presents a mechatronics design of a gait-assistance exoskeleton for therapy in children with Duchenne muscular dystrophy (DMD). This type of muscular dystrophy is a severe condition that causes muscle wasting, which results in a progressive loss of mobility. Clinical studies have shown the benefits of physical therapy in prolonging the mobility of patients with DMD. However, the therapy sessions are exhaustive activities executed by highly qualified rehabilitation personnel, which makes providing appropriate treatment for every patient difficult. This paper develops a mechatronics design of a gait-assistance exoskeleton to automate therapy sessions. The exoskeleton design uses adaptable mechanisms to adjust the device to the patient's needs and includes the design of a series-elastic actuator to reduce the effects of nonalignment of the rotation axis between the exoskeleton and the patient. A mathematical dynamic hybrid model of the exoskeleton and a child's body is developed using anthropometry of a population of six-year-old children. The hybrid model is used to design a nonlinear control strategy, which uses differential geometry to perform feedback linearization and to guarantee stable reference tracking. The proposed control law is numerically validated in a simulation to evaluate the control system's performance and robustness under parameter variation during therapy with trajectory-tracking routines.