Exoskeleton for human energy augmentation the Shadow Suit concept: Lower extremity development of the Shadow-Suit

To facilitate kinematic changes in expendable exoskeletons, considerations must be placed on the links leading to the end joint(s), where rigid connections with human limbs could lead to uncomfortable experiences for a pilot operating the exoskeleton. To cater to changes in human size while maintaining initial kinematic computation, an additional exoskeleton named the Shadow-Suit is proposed as a control module to provide feedback to the exoskeleton (the outer shell). This Shadow-Suit is an anthropomorphic suit to be attached to the non-anthropomorphic exoskeleton (outer shell), where movements of this suit will be “shadowed” by the outer shell exoskeleton. This paper focuses on the development of the lower extremity of this Shadow-Suit concept. The kinematics of the lower extremity was computed using Denavit-Hartenberg modelling, where the end joint of the lower extremity is predicted during a normal walking stance of the pilot. Sensory feedback was processed by Omron CPM-2A PLC module, in which lag of the reaction of the pneumatic actuator on the outer shell exoskeleton was able to be minimized to the point of ≈1.2 seconds. Result suggest that this concept is able to reduce the excessive torque towards the pilot, while at the same time able to accommodate different pilot limb length without having to change the link length of the exoskeleton.