Clarkson Powered Knee Prosthesis
The focus of my master’s thesis at Clarkson University…
was on the potential to regenerate electrical energy with a powered transfemoral prosthesis during energetically net-dissipative activities, such as walking over a level surface, stair descent, or stand-to-sit transitions. The device was developed by my advisor, Prof. Kevin Fite, and can be seen in Figure 20.
Through modeling and simulation, I was able to determine the regimes where energetic recovery is theoretically possible, but needed to provide experimental validation. For this, I developed a variant of the MOSFET H-bridge that can switch between a powered mode, a coasting mode (i.e. the motor leads are effectively open), and a braking mode (i.e. the motor leads are shorted together). To this, I added a bank of ultracapacitors that would charge during phases where the back electromotive force (EMF) of the motor exceeded the voltage on the capacitors.
In the end, I was able to demonstrate that it is feasible to regenerate modest amounts of energy while concurrently controlling the damping at the knee joint, albeit with lower efficiency than the models would predict (Tucker and Fite, IEEE Adv. Intel. Mechatronics, 2010).
Figure 20 - The Clarkson Powered Knee Prosthesis, as worn by an able-bodied subject.