Electronic Control of Combination Knee/Ankle Prosthetic

Period of Performance: 05/01/2008 - 01/30/2011


Phase 1 SBIR

Recipient Firm

Seattle Prosthetic Design, LLC
Edmonds, WA 98020
Principal Investigator


DESCRIPTION (provided by applicant): While the addition of microprocessors has enhanced the control of modern limb systems, they still do not match the comfort and functionality of the thirty year old HydraCadence. This above the knee (AK) limb system provides functionality such as: active dorsiflexion, rapid planterflexion, adjustable heel height and swing rate control. The HydraCadence's active dorsiflexion ankle was the first and only AK limb system that allowed the amputee to swing the prosthesis in the sagittal plane without dragging the toe of the foot, thus producing a more natural gait and requiring less energy for movement. Since the introduction of electronic control in the field of prosthetic knees, feedback has been limited to knee angle and load. Phase I of this project will consist of upgrading the current mechanical system of the HydraCadence to include hip and knee angle measurements with electronic actuator control of the knee damper valve. Hip angle measurements in conjunction with lead-compensation will be used to control gate rate on a real time per cycle basis. The additional information from the hip angle will allow the control scheme to accurately determine what phase of gait the amputee is progressing through and will let the system adjust for anomalies such as ascending or descending steps, traversing steep slopes or abnormal behavior such as stumbling and falling. Phase II of this study will build upon the information gained in Phase I and will address the issues of incorporating the added benefits of knee stance phase control. Over the years, the HydraCadence limb has built a devoted customer base that expounds the virtues of functionality and comfort provide by this limb system. There have also been several studies recently that have shown the benefits in comfort and safety of the addition of electronic control to prosthetic knees [3]. The goal of this project is to provide one system that offers the functionality and comfort of both the HydraCadence and the modern microprocessor knees.