An analysis of quantization errors in digital control systems andits application to a hard disk drive

摘要

The analog-to-digital (A/D) converters and the digital-analog(D/A) converters are required for construction of a digital controlsystem, which convert analog signals to digital signals and digitalsignals to analog signals, respectively. However, it should be noticedthat all the converters actually have finite wordlength implementation.Considering these quantization errors, we must decide the number of bitsof the A/D converters and the D/A converters by trial and error. In thispaper, we derive a theorem which shows the relation between the systemparameters and the quantization errors caused by A/D and D/A convertersin a general digital control system with two degrees of freedom.Therefore, the trial-and-error process can be excluded completely whenthe number of bits of A/D converters and D/A converters are decided.Moreover, we apply the obtained theorem to a simulation of a hard diskdrive control system. The suitability of the obtained theorem forpractice use is verified by the simulation