This proposal is for the development and evaluation of an active ankle foot orthosis (AAFO). This device will fill the gap in the existing research aimed at helping individuals with conditions causing foot drop as well as in other related rehabilitation activities. Individuals with foot drop are unable to dorsiflex their foot because of impaired muscle activity around the ankle. The major causes of foot drop are trauma to the involved nerves, stroke, cerebral palsy and multiple sclerosis. There are two common complications from foot drop. First, there is no control of the foot after heel strike, so that it slaps the ground on every step. The second complication is the inability to clear the toe during swing. This causes the person to drag their toe on the ground throughout the swing or compensate through alterations in the normal biomechanics of ambulation. An AAFO is a wearable device that is intended to help normalize the gait of a person with foot drop. The device provides a controlled force to compensate for muscle deficiencies that cause the condition. The current AAFO?s use bulky actuators such as DC motors and pneumatic actuators, which do not allow for practical and comfortable walking. In this research shape memory alloys (SMAs) will be used to provide the actuation force of the AAFO. To this end, analytical and experimental studies will be performed to develop a device that is lightweight and comfortable for walking. The main benefit of the SMAs for this application is biocompatibility and their very high force to mass ratio: an SMA wire can lift close to 80,000 times of its own weight. Furthermore, SMA actuators do not need moving parts, which greatly reduce the complexity of the design.
