Inductive charging for a self-balancing robot - Design and development of prototype

Abstract

In this master’s thesis project an inductive power transfer (IPT) system is designed and developed. This IPT system should in the future be implemented in Aros Electronics self-balancing robot Glenn. The system can transfer 153 W over a 3 cm air gap with an efficiency of 84.5 %. Furthermore, the IPT system is able to transfer 100 W with a misalignment between the power pads of 4 cm as well as an increased air gap to 4 cm. The IPT system has been designed by iterations between COMSOL simulations and circuit simulations in LT spice. The power supply in the IPT system produces a 83 kHz square-wave voltage. The system uses series-series capacitive compensation to achieve resonance on the transmitting and receiving circuits. With the series-series compensation the systems functions as a voltage source and the compensations is independent of load and the mutual inductance, making it a suitable choice for charging of batteries. The transmitting and receiving coils are made of litz wire to decrease skin effect and proximity effect. The coils are placed on ferrite plates to increase the magnetic field and mutual inductance between the coils, resulting in two power pads.