Design and Modeling of a Robot for Rehabilitation of the Sit-to-Stand Movement and Walking

Disabilities of the lower extremities significantly affect a person’s ability to perform activities of daily living. Many people have been affected by this type of disability due to birth disease or injury from accidents, strokes or even old age. The technical aids used in this type of disability are very basic, and rehabilitation is mainly performed by therapists. Rehabilitation consists of repetitions of exercises with normal movements that must be performed for prolonged periods of time. On the other hand, therapists, having to support the weight of the patient, tend to get injured. This paper introduces the design and modeling a robotic device intended to assist the therapist in the rehabilitation of sit-to-stand (STS) and walking movements, focusing primarily on the technical aspects of the system. The robot is designed to safely support the user’s weight and guide the user with appropriate movements according to the usual biomechanics of STS. This paper presents the solution of the inverse kinematic modeling of both the position and velocity of the robot mechanism, as well as the dynamic analysis. A series of simulations is conducted to evaluate the performance of the proposed mechanical architecture during the STS task, providing quantitative information on the system dynamics and the interaction forces between the user and the robot. The mathematical model was employed in the design of a prototype intended for children aged 8–12 years, capable of supporting up to 50 kg and providing a vertical motion range of 20–90 cm. The main structural elements of the robot, its control architecture, and its operation during the execution of the STS task are described. Finally, the conclusions of this work are discussed, and future work derived from this research is outlined.