HydroBone and Variable Stiffness Exoskeleton with Knee Actuation

• Main Author: Sridar, Saivimal
• Other Authors: Marko B. Popovic, Advisor
• Format: Others
• Published: Digital WPI 2016
• Subjects: HydroBone; Jamming of granular media; HydroMuscle; Variable stiffness; Exoskeleton
• Online Access: https://digitalcommons.wpi.edu/etd-theses/391; https://digitalcommons.wpi.edu/cgi/viewcontent.cgi?article=1390&context=etd-theses

The HydroBone is a variable stiffness load-bearing element, which utilizes jamming of granular media to achieve stiffness modulation, controlled by the application of positive pressure. Several compressive tests were conducted on the HydroBone in order to quantify the load-bearing capability of the system. It was determined that the stiffness of the HydroBone was a function of the internal pressure of the system. A controller was modeled based on this function to achieve automatic stiffness modulation of the HydroBone. An exoskeleton was designed based on the HydroBone and various actuators for the exoskeleton were considered. The HydroMuscle, a soft linear actuator was selected to provide knee actuation for the exoskeleton, based on several efficiency and force output test conducted. A knee brace was designed, capable of producing 15Nm of torque on the knee, actuated using Bowden cables coupled to the HydroMuscles.