Design, control, and human subject evaluation of powered hip exoskeletons

Abstract

Powered lower-limb exoskeletons have potentials to revolutionize many fields such as industrial, military, and clinical industries. Most lower-limb exoskeletons are complex multi-joint devices that are often limited by their weight, convoluted controllers, and imperfect power transmissions. To make exoskeletons more robust, researchers are re-focusing on single-joint devices and studying the effects of human-machine interaction. While both the ankle joint and hip joint are main torque contributors during level walking, the hip joint is less efficient due to the lack of spring-like tendons. As a result, providing hip joint assistance may be more impactful than aiding other joints.

This thesis proposes a top-down approach towards wearable robotics by designing, building, and testing two versions of torque-controllable exoskeletons. The goal is to understand how to achieve the best performance through novel designs and controllers. Hip Exo v1.0 and Hip Exo v2.0 both utilize series elastic actuator design to achieve closed-loop torque control. Hip Exo v1.0 is validated through an assistance magnitude study and a proportional EMG profile pilot. Hip Exo v2.0 is developed to fix many of the design flaws from Hip Exo v1.0 through new mechanical and electrical designs. The improved Hip Exo v2.0 allows for the development and implementation of next-generation EMG pattern recognition controller. An EMG delay pilot, EMG pattern recognition pilot, and speed/ramp estimator pilot are performed with Hip Exo 2.0. All the human subject studies give valuable insights into understanding how human interacts with wearable robots. The findings of this thesis act as a comprehensive guide for design, control, and human subject validation of powered hip exoskeletons.