Control Strategy for a Developed Robotic Spine Exoskeleton

Adolescent Idiopathic Scoliosis, called AIS, estimated to affect up to 4% of adolescents, is the biggest problem among the orthopedic profession. It is an abnormal side-to-side curvature of the spine which occurs between the age of 10 and skeletal maturity without any known reason. Bracing as a common treatment of AIS does not adopt to skeletal changes during the treatment because of its sensor-less design and the lack of control on corrections provided by the brace. Its static design may also affect the patient's safety and convenience. Robotic spine exoskeleton can reduce the problem by restoring the balance of forces along the spine using the measurements received from sensors installed on the robot. In this paper, an in-house developed robotic exoskeleton with one Stewart-Gough Platform (SGP) is designed, and an impedance control strategy is proposed to implement the interaction between the robot and the patient in order to make the exoskeleton more safe and convenient for the patient to use. Besides, an Adaptive Inverse Dynamic Controller (AIDC) is proposed to improve the trajectory tracking of the exoskeleton in the presence of large modeling errors due to uncertain dynamics. Numerical simulations and the validating experimental results are conducted to demonstrate the performance of impedance control in terms of interaction control. In addition, the proper trajectory tracking is verified through the numerical simulations of the proposed AIDC controller.