Other team members: Abdullah Al Mohaimen, MD. Sadman Amir.
Supervisor: Dr. Muhammad Abdullah Arafat.
Wireless power transfer has been the preferred choice for supplying power to biomedical implant devices. To achieve maximum power transfer efficiency, we need to ensure the critical coupling condition between the transmitter and receiver circuit. The distance between the transmitter and receiver coil may change in a dynamic environment. Similarly, the coils' orientation and the medium's property in between the coils may also change. If any of these changes, the critical coupling is lost, rapidly decreasing the power transfer efficiency.
Our research objective is to develop a complete system that automatically re-calibrates itself to critical coupling by observing the changes in the dynamic environment.
While doing experiments involving tranmitter and receiver coils, it is difficult to place the coils in a fixed upright orientation. Besides, precisely controlling the distance between them is also hard. To solve these problems, I designed this setup in Autodesk Fusion 360 following the directions of my Professor. Coils of any size can be fixed to the holders and the distance between them can be easily controlled and can be precisely measured. After I completed this setup, doing experiments in the lab became easier and experimental data were more accurate.
To achieve Magnetic Resonance Coupling in a dynamic condition, we needed a variable inductor. I designed and implemented this stepper-motor-controlled variable inductor. The overlap between the half-circular ferrite core and the coil wrapped around the bobbin is controlled by the stepper motor to achieve variable inductance.
At one stage of our research, we tried to place variable capacitors in both transmitter and receiver circuit. We had two OPA564 opamps. We implemented two compact circuit boards. Each had a variable capcitor whose capacitance can be controlled by a variable resistor. I designed the PCB on Altium. Unfortunately, this approach was not a success since the OPA564 opamps were eating too much power which was decreasing the overall efficiency.
We have been using Vector Network Analyzers, RF Signal Generators, Multi-Channel Oscilloscopes, and DC signal generators for different experimental setups. One of the perks of being involved in this research is I got to know the ins and outs of operating these super-useful machines. Since these are very expensive devices, I always handle them with great care.