Optimal Control to Facilitate the Development Process of Exoskeletons

Developing an exoskeleton for the lower back is challenging because the ideal support is not known and may vary across the users. As a result, a series of prototypes and extensive testing is needed to determine a suitable design of such a device. We aim to facilitate the development process of a spinal exoskeleton by optimizing the characteristics of its passive elements, taking into account human-robot interaction. Biomechanical models were created and adapted to the anthropometric and muscular properties of five recorded subjects performing unassisted lifting motions. A dynamic model of the exoskeleton was developed with torque generation consistent with the prototype. Possible configurations of the passive elements are specified by a set of parameters which were determined during optimization by minimizing the simulated human actuation required to perform the recorded motions while wearing the exoskeleton. Comparing optimized and initial setup, a significant improvement in exoskeletal support was achieved for all subjects, while contact forces remained within specified limits to ensure a comfortable usage of the device.