Design and Prototype of a Gravity-Balanced Leg Orthosis

Design and Prototype of a Gravity-Balanced Leg Orthosis

  Gravity balancing is often used in industrial machines to decrease the required actuator efforts during motion. In the literature, a number of methods have been proposed for gravity balancing that include counterweights, springs, and auxiliary parallelograms to determine the center of mass. However, these concepts have not yet been significantly applied to rehabilitation equipment. This paper presents the underlying design of an orthosis for the human leg that is capable of fully or partially balancing the leg over the range of its motion. This design combines the use of auxiliary parallelograms to determine the center of mass along with springs to achieve a fully or partially gravity balanced orthosis. A first prototype has been constructed to demonstrate the effectiveness of the idea. Future prototypes will have parameters that can be tuned to the geometry and inertia of a specific human subject.