Green Energy Harvesting in Prosthetics

Energy Harvesting

The green energy harvesting here will
emphasis use of piezoelectric devices in
Prosthetic legs. Geometric parameters,
beam, mass and resistive electric loads
significantly influence the output power [4].
The piezoelectric CMOS harvesting could
bypass the input voltage and recover some
energy to increase the energy during
negative piezoelectric voltage.

The devices that have been used are
piezoelectric, electromagnetic, electrostatic,
pyroelectric, photovoltaic and
thermoelectric. The conversion of
harvesting energy is very good in
scalability, capability, high energy density
and compatible with standard electronic
technology. In addition, the piezoelectric
could be coupled to a mechanism to
perform opening of the contacts in the
switching devices [1-3].

Reference:  Piezoelectrics in Prosthetics: Energy Harvesting Paperback – 25 Apr 2016 by Dr Kesorn Pechrach Weaver PhD (Author)

Piezoelectric Test in Prosthetics: Energy harvesting

CHAPTER 1

ENERGY HARVESTING

This works present the design of an energy
harvesting system using smart materials
for self power generation of upper and
lower prosthetic legs. The smart materials
like Piezo Composites, Piezo Flexible Film,
Macro Fibre Composites, and PZT have
been employed and modified to be
appropriately embedded in the
prosthesis.

The movements of the prosthesis would
extract and transfer energy directly from
the piezoelectric via a converter to a power
management system. Afterward, the power
management system manages and
accumulates the generated electrical energy
to be sufficient for later powering electronic
components of the prosthesis.
The experimental results of energy
harvesting and efficiency in peak
piezoelectric voltages during step up and
continuous walking for a period of time.
One of the most interesting sources for
energy harvesting is environmental
vibrations.

The devices that have been used are
piezoelectric, electromagnetic, electrostatic,

Reference: Piezoelectrics in Prosthetics: Energy Harvesting Paperback – 25 Apr 2016 by Dr Kesorn Pechrach Weaver PhD (Author)

Prosthetic Foot & harvesting equipments

3.4 Prosthetic Foot & harvesting equipments

Propulsion is generated from the reaction between the foot and the ground in the standing phase. To improve the propulsion function of the foot prosthesis and stump system, it must shorten the first period of the standing phase when the ankle power is negative and more quickly release energy in the second period. Decreasing the elastic modulus of the material of the energy storing element could greatly increase the energy stored and energy released. The elastic modulus of the material has only a small effect on the propulsion index, but the stored and released energy changes significantly with it. [17]

Considering the motion and power variation in the ankle joint in the standing phase, during the muscles contract and the direction of reaction force exerted by the ground coincides with the direction of the relative motion. The muscular power during that period is defined to be negative. During the standing phase, the muscles extend, the reaction force is in the opposite direction to the relative motion, and the power is defined as positive. [49-51]

The test stand can adjust the angle of the prosthetic foot position. To test the suitable positions to harvest energy from foot while walking, standing and swing position. 

The film piezoelectric were placed  in the sole position, in the bottom of the foot. Sole is the first position to touch the ground when walking forward.

Ronsek Innovation 

Pechrach Publishing 

https://www.amazon.com/Piezoelectrics-Prosthetics-Kesorn-Pechrach-Weaver/dp/0993117821 

Upper Prosthetic Leg with harvesting equipments

Upper Prosthetic Leg with harvesting equipments

There is a plan to embed some piezoelectrics inside the socket area including the hitting harvesting kit. The complete set would be moulded as part of the material for the upper prosthetic leg.

The harvesting circuit for using with the hitting mechanism consists of hitting hands, cores and low energy consumption motor. This test kit can have a variation speed to find the maximum delay time to create the maximum vibration in the PZT blade.

Four sets of PZT piezoelectric connects as series to produce more power from harvesting energy. Four capacitor banks are used as storage energy tanks for power which produce from PZT piezoelectric.  

Reference:

 Piezoelectrics in Prosthetics

Ronsek and Pechrach Publishing