ankle. In addition, the strap was changed to a BOA Fit System-based
brace to make it easier to wear. The total weight of the AFO was 600 g,
which was 120 g lighter than that of the prototype AFO.
Electronics refinement: For the electronics of the AFO system,
the size and weight of the master board were reduced to 1/4 and 1/3,
respectively (Table 1). In addition, a Bluetooth module was loaded for
communicating instead of a 1.2-m cable in the previous system (Fig. 2).
Compressor refinement: Based on a previous study [14], the
customized dual-piston crank compressor was improved by reducing the
gear ratio and increasing the nominal torque of the DC motor to reduce
the noise level. The rotational motion generated by an electric motor
combined with a gearbox was transformed into a reciprocating linear
motion with a piston crankshaft mechanism. The reciprocating linear
motion of the piston is shown in Equation (1)