Active neck orthosis for musculoskeletal cervical disorders rehabilitation using a parallel mini-robotic device

This work presents the design, construction, simulation, instrumentation, and implementation of a closed chain robotic active neck orthosis with four degrees of freedom satisfying a similar configuration to a four-legged Stewart platform. The dynamics of the device is regulated by a robust control strategy with state restrictions based on a first sliding mode controller with state dependent gains that operates as a divergent function as the states approach the state restrictions. The formal justification about the application of the controller on the proposed orthosis, the finite-time convergence to a sliding surface and the effect of the constraints is proven. The orthosis is also controlled with a traditional state feedback strategy to evaluate the tracking error concerning an external disturbance and compare its performances against the proposed control strategy. A graphical interface based on computer vision is developed to select the type of therapy and assess the patient's range of motion while wearing the orthosis. The system is tested in some selected volunteers subjects, managing to limit the range of motion within a pre-established area based on the range of motion reported by patients with cervicalgia and whiplash syndrome found in the literature. The developed system offers a novel method to deal with the treatment of neck illnesses based on a novel mechatronic device.