Single-bit digital signal processing for current control of brushless DC motor

The application of single-bit digital signal processing to mechanical control systems has already been proposed by the authors. A single-bit digital signal is obtained with a delta sigma modulation. This bit stream signal has smaller quantized error at lower frequency and higher limitation of frequency response. This technology is widely applied in an analogue to digital conversion system in audio and telecommunication systems. We applied this high performance single-bit signal for the current control system of a brushless DC motor which requires high speed processing and high resolution in the system. The signal processing algorithm which was proposed by the authors was applied to the servo controller. The control processing system was installed in FPGA. This is the first trial to apply for P compensation, PI compensation and phase lag compensation in an actual servo system. In all compensation systems, the torque ripple at rated torque was 2%. We successfully demonstrated the single-bit digital servo system.