ERC Researchers Demonstrate Energy Savings for Ankle-Foot Orthosis by Recovering Exhaust Gas

Achievement date: 

Researchers at the Center for Compact and Efficient Fluid Power (CCEFP), an NSF-funded Engineering Research Center (ERC) headquartered at the University of Minnesota,  demonstrated a strain-energy accumulator on an Ankle-Foot Orthosis (AFO) as a way to recover exhaust gas in its pneumatic system (see figure).


In these preliminary trials, use of the pneumatic strain-energy accumulator resulted in an energy savings of over 25% relative to operating the pneumatic actuation of the AFO in the conventional manner. This is an important energy-saving achievement because the AFO is representative of a typical pneumatic actuator task and industrial pneumatics are used widely in the United States.


The typical method of pneumatic actuation is only 23% to 30% efficient since a large amount of the energy is exhausted when the actuator changes direction. The pneumatic strain-energy accumulator is able to store a portion of this exhaust gas and then reuse it to assist the powered return motion of the actuator. Given that about 0.5% of the energy consumed in the United States is for industrial pneumatics, an application of this technology for pneumatic devices on assembly lines could save $1.4B to $2.5B per year.