A speed collection system based on the phase-locked loop（PLL） six frequency multiplication for brushless DC motor（BLDCM） control system is designed.High performance processor STM32 is used as core control component

PLL frequency multiplication technique is adopted to obtain precise control of motor speed.This system includes processor

drive circuit

inverter circuit

frequency multiplier circuit and motor.Frequency multiplier circuit realizes six frequency multiplication for the three-path Hall sensor signals.Its output are taken as speed feedback of system.According to simulation and measurement

the designed PLL six frequency multiplier circuit can carry on speed sampling and processing accurately and effectively

and the precision of speed sampling is improved.The experimental result shows that the system is practical and valuable in engineering.