Mechanical System

The post-op shoe is connected to the footplate by a pair of screws drilled into the non-slip sole. Connecting the footplate to the rail is a 2-DOF gimbal assembly: 397-Inner_Outer-4.pdf, which provides the range of motion for proper movement of the foot.

Springs connect crank and action arms, allowing rotation in the sagittal plane without breaking the four-bar mechanism that actuates the AFO in the coronal plane. The springs are also providing greater range of motion overall and add compliance between the motor and the interface with the subject.

The motor and electronics are attached to a slider along the rail with set screws for variable spring tensioning and levels of compliance. The potentiometer was connected concentrically with the motor crank shaft, butting up against the shaft and secured to the crank arm with a set screw. These components are electrically isolated with the use of machined pieces of Delrin instead of aluminum.

At the top of the rail the device is attached to the subject with the use of some padding and a strap. The leg wrap seen in Figures 2 and 3 improves the connection of the EMG electrodes to the skin.

The majority of the final mechanism was machined out of aluminum, but Delrin was used where electrical isolation necessary (e.g., to mount the electronics to the rear brace and the mount the potentiometer). Steel was also used in the shaft collars and spring which were purchased instead of machined.