8 E. Bonisoli et al. Fig. 1.9 3D printed prototypes 0 2 4 6 8 101214161820 0 0.2 0.4 0.6 0.8 1 1.2 Time [s] Average Harvested Power [mW] Running sim no friction Walking sim no friction Running exp Walking exp 0 0.05 0.1 0.15 0.2 0.25 0.3 –5 0 5 Time [s] Voltage [V] 10th step 0 0.05 0.1 0.15 0.2 0.25 0.3 0 500 1000 Time [s] Harvested Energy [μJ] Fig. 1.10 3D printed prototypes performance input, while, when running, a broad increase in the energy harvested is shown, both in simulation and in real test, about 40 %. The experimental recovered energy during a running step is about five times the required for the activity detection and data sending. Storing the energy surplus compensates the difference with respect to the requirements under very low intensity input allowing detecting every step during activity. 1.4 Conclusions With the aim of feeding a bluetooth step-counter placed in the sole of a shoe for walking and running activity monitoring, a semi-industrialized set of EH prototypes with a dedicated electronic interface has been designed, produced and tested in order to demonstrate the feasibility of the project and validate the simulation model. Energy harvesting is performed with a magneto-inductive transducer designed to maximize the recovery in response to the vibrating input due to the impact between the shoe and the ground during walking or running. The electronics interface consists of a step-up and buck converter, and, by means of a full wave active boost converter with a transducer current control, provides an optimum adaptive load emulation independently from the signal provided by the transducer and from the voltage stored on the output capacitor. The device has been designed in according to the manufacturing requirements for a medium-large scale production and taking into account the severe environment in term of external load where it will be placed. Numerical and experimental results show the effectiveness of the developed EH step-counter device demonstrating that the energy recovered during the impact is
RkJQdWJsaXNoZXIy MTMzNzEzMQ==