Wearability improvement of untethered pneumatic ankle foot orthosis

Pneumatic active ankle foot orthosis (AFO) for drop foot correction has the advantages of inherent compliance and remote force control. However, pneumatic AFOs that use heavy stationary air compressors as the energy source have limitations for outdoor use. Although a portable air-compressor-powered pneumatic AFO has been developed recently, it is difficult to operate in practical applications owing to the bulky design of the AFO and excessive power sources with overheating issues. In this study, the AFO system was optimized to improve wearability. The weight of the AFO was decreased from 720 to 600 g. A Bluetooth module was installed instead of a 1.2-m cable between the master and slave boards. The efficiency of the portable pneumatic actuator increased 12.4%, whereas its volume decreased 11%. The internal temperature was reduced from 100°C to 40°C using two cooling fans. Throughout the optimization process, the wearability of the AFO system was improved for real-life use.