Design and fabrication of an Intuitive Leg Assist Device to address lower extremity weakness

The Intuitive Leg Assist Device (I-LAD) is designed to address a demographic of people with lower extremity weakness. It optimizes cost, weight, and functionality, and provides the power and support needed to perform natural ambulation. The design mimics the human gait cycle by coupling the actuation of the knee and hip via a dual four-bar linkage system modified from a crank rocker system, with a 12.8% and 14.1% error in the hip and knee movement, respectively. The patient supports the device using an over the shoulder harness and modified work belt, both connected to an acrylic plate. The plate serves as the mounting for the motor, planetary gear system, and electrical components that drive the linkage system. The linkage system is connected to a knee brace and ankle foot orthosis that minimizes the effect of foot drop. The design implements feedback and safety by incorporating four sensor inputs-two force sensors beneath the feet and two goniometers on the hips-and a microprocessor, which controls motor actuation. The program logic ensures that the device shuts down upon unintended user movement, minimizing safety hazards.