Performance improvement of the linear BLDC generator in a deep space explorer

This paper presents methods to improve performance of the power supply system in a NASA deep space explorer. In the stirling engine driven reciprocating brushless DC (BLDC) generator, the accurate position information of the prime mover is important to diagnose the performance of the engine and prevent the distortion of the output power. Because sensors to detect the position are fragile and unreliable, and conventional sensorless technique has a drawback in the low speed region, a novel sensorless position detection technique for the prime mover has been proposed and verified. Another major issue of the generator for the spacecraft is power density maximization. The mass of the power system is important to the mass of the satellite. Therefore, the components of the spacecraft should be lightweight. Conventional rectification methods cannot achieve the maximum power possible because of non-optimal current waveforms. The optimal current waveform for maximizing power density and minimizing machine size and weight in a nonsinusoidal power supply system has been derived, incorporated in a control system, and verified by simulation work.