a wearable power generator for sports monitoring applications
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A Wearable Power Generator for Sports Monitoring ApplicationsUrsula Leonard 08331502
Sports and Exercise Engineering, National University of Ireland, GalwaySupervisors: Dr. Maeve Duffy, Dr. Edward Jones
Figure 1 The table lists energy levels available form the body[2]. The optimised generator structure shown outputs max AC voltage. The green waveform (generator shaken) and the yellow waveform (running on a treadmill) are examples of generator output.
Figure 2 A schematic of the coversion circuit drawn in Psim is presented with a picture of the choosen circuit built on a small board. The graphs show predicted DC output and measured DC output from generator.
Figure 3 shows two graphs; possible load devices and the relationship between generator output and speed. The images are possible load devices.
References [1] T. Starner, “Human-Powered Wearable Computing”; [2] E. Romero, R. O. Warrington, and M. R. Neuman “Body Motion for Powering Biomedical Devices”.
IntroductionOver the past number of years, the
number of portable electronic devices we use in everyday life has
steadily increased. With the advantage of portability comes
one crucial limitation; they are all inherently dependant on batteries to meet their energy requirements. By prolonging the life of batteries or eliminating them completely,
we are confident the results would be life changing; for example,
detection of problems earlier with monitoring applications, less
interaction with your physician and a decrease in the number of operations performed yearly
replacing batteries.
Project Objectives• Design and test of a wearable generator to provide maximum output AC power in the space
available in a typical “smart” running shoe.
• Design, modelling and testing of an optimised AC/DC converter stage for connecting between the generator
output and a load device.• Investigate possible low power
consuming applications in the field of sports and exercise and incorporate
into system.• Comprehensive system testing for
different combinations of user activity levels and identification of limits in generator performance.
Materials
To achieve the movement of a magnetic field through a
conductor, the generator utilises copper coils and small neodymium magnets. Placed at the ankle, the generator takes advantage of the
repetitive pendulum motion of the feet during normal gait. By
allowing the magnet to slide freely up and down through the coil, a
voltage is induced. Using Psim simulation software, possible conversion circuits were
analysed and a doubler circuit was chosen as the converter stage. A network of schottky diodes and
capacitors implements this circuit outputting constant DC power.
Further workThe emphasis can now be on developing a load device and
possibly a storage unit. Further optimization of the generator
structure would be encouraged, to improve the
power output levels and perhaps make the structure even smaller. At present the
generator is placed at the ankle; incorporation into an
altered shoe and a better hardware system would help
during the texting phase.
ConclusionMaximum energy is available
for capture during fast walking and fast running. In the
transition from walking to running, there is a dip in available power. This is
because, while walking there is always at least one foot on the
ground, but while running both feet are off the ground
for a period of time. The reduced swinging causes a dip
in generator performance. Gender or weight has no effect on generator performance . All testing was completed indoor
on a treadmill.
Acknowledgments The author would like to thank Maeve Duffy, Edward Jones, Myles Meehan and Martin Burke for their continued help and guidance throughout the course of the project.
Method
In previous studies it has been calculated that up to 67W of
power are available from heel strike while walking[1]. By
electromagnetic induction, this wasted energy is captured and
used. Faraday’s law states that the induced voltage in any closed circuit is equal to the rate of change of magnetic flux. The
magnetic flux is directly proportional to the magnetic field,
so as the magnitude increases, the magnetic flux increases. The
magnitude of the voltage is proportional to the speed at which
the conductor cuts the flux and the number of turns in the
conductor.
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