Novel initial position detection technique for three-phase brushless DC motor without position and current sensors

This work presents a novel detection technique of initial position for three-phase brushless DC motor (BLDCM), which doesn't require any current and voltage sensors, and thereby significantly reducing the cost. The fundamental principle of the technique is to determine the initial position of permanent magnet by the difference of falling times of unexcited stator windings. As compared to previous research result Y.S. Lai et al., (2003), the error caused by the nonsaturation effect of excited windings can be avoided. Therefore the accuracy can be significantly improved. Experimental results derived from an FPGA-based control system will be presented to demonstrate the feasibility of the presented technique.