There are currently many challenges in creating portable human-assistive robotics and exoskeletons, although the need for robotic human assist continues to grow. These challenges span disciplines such as control, design, fuel and efficiency, user-interfaces, neuroscience, and kinesiology. Our lab has developed a pneumatically powered ankle-foot orthosis (PPAFO) to address some of these issues.

In this dissertation, we address the issue of availability of portable pneumatic power sources, and we evaluate the short-term kinematic and metabolic impact of a bilateral, bidirectional portable powered ankle-foot orthosis (PPAFO) in an able-bodied population during over-ground walking, and we evaluate the kinematic and metabolic impact of a unilateral, bidirectional portable powered ankle-foot orthosis (PPAFO) in persons with gait impairment due to Multiple Sclerosis.

First, in Chapter 2, we address the state of portable powered pneumatic power sources. Specifically, we evaluated the use of compressed gas tanks with carbon dioxide or nitrogen as fuel. A test bench model of the PPAFO and walking trials (treadmill and over-ground) were used to evaluate each tank and gas, investigating normalized run time, minimum tank temperature, and rate of cooling. We concluded that compressed gas tanks can be used to successfully power portable pneumatic robotic platforms, especially when a recycling circuit can be implemented to increase the longevity of the fuel source, but considerations need to be taken into account in order to determine the proper fuel, based on size, weight, cost, and availability.

In Chapter 3, we evaluated a bidirectional, bilateral powered ankle-foot orthosis or exoskeleton system during over-ground walking in able-bodied individuals. With the powered PPAFOs, participants were able to reduce the metabolic power needed for walking compared to the unpowered PPAFO condition, and they were able to match the minimum metabolic power needed in shoes walking. Some kinematic changes were seen while using the PPAFOs, specifically an unexpected reduction in plantarflexion during toe-off.

In Chapters 4 and 5, we evaluated the use of a bidirectional powered ankle-foot orthosis to assist persons with gait impairment due to multiple sclerosis.

Use of the current embodiment of the portable powered AFO did not improve gait performance as measured by spatiotemporal parameters of gait. Significant differences in kinematic parameters at the ankle were observed such that the PPAFO was able to provide better assistance for foot drop during swing than the AFO or a shoes condition. Changes in kinematics at the knee were found such that the changes are likely due to compensatory reactions to the changes at the ankle induced by the footwear.

Throughout this work, we have been motivated to further research the mechanical design of the device so that users can better match their natural gait pattern in regards to spatiotemporal and kinematic parameters. Improving device design and functionality will help to determine if powered orthoses can be effective at assisting and improving gait function in persons with gait impairment.