Design, Characterization, and Dynamic Simulation of the MAHI Open Exoskeleton Upper Limb Robot

Abstract

Stroke and spinal cord injury are becoming ever more prevalent in the United States. Recent research has shown that rehabilitation robots have the potential to positively impact the rehabilitation process by providing a platform for repetition-based movement therapy. To advance the field, future research directions for robotic rehabilitation are focused on advanced model-based control algorithms, and the combination of robotics with cutting-edge neuromodulation technologies. These approaches necessitate devices that not only feature kinematic and dynamic properties well-suited for model-based control, but also require devices that allow for easy placement of sensors and electrodes on the limb when inserted in the robot. With these design goals in mind, we present the MAHI Open Exoskeleton, a four-degree-of-freedom robot with an open mechanical structure and simplified dynamics, combined with open-source software, that together lay the groundwork for advanced model-based control. The dynamic properties of each joint were characterized and compared against other recently developed rehabilitation robots. Open-source software was developed for the robot, which provides users with both low-level and application-level interfaces to implement a variety of control strategies. Dynamic equations were developed and implemented into a real-time simulation with a visualization, including a seamless interface to the developed software library. Impedance control and model predictive control were implemented and compared to the simulation, proving the value of the new designs.