Study On Frequency Characteristic And Compensation Of Dynamic Unbalance Measurement System

Balancing rotating speed is not only related to the quality and geometric dimensioning of the rotor,it also needs to adapt to the working speed of the rotor in the dynamic balancing correction.The balancing rotating speed of the general hard-bearing dynamic balancing machine is 120~60000rps.The unbalancing vibration signal is related to the balancing rotating speed and the low-frequency vibrationg signal is so small that coverd by the high-frequency noise,so the frequency characteristic of the measurement system should be considered.The frequency characteristic of unbalancing measurement system depends on frequency characteristic of rotor-cradle vibration system,vibration pick-up and measurement circuit.This paper analyzes the frequency characteristic of these three modules and researches in-situ frequency compensation method of the measurement circuit.For the rotation frequency range and vibration response of general hard-bearing dynamic balancing machine and the rotating mechanism of CT,this paper combining the frequency characteristic of vibration pick-up,selects vibration pick-up,and compares and analyzes the output signal of sensor.As frequency response of low-pass filter circuit can't compensate completely for the response characteristic of the vibration system of balancing machine,which then causes measurement error,this paper studies two methods to reduce the frequency error: rotation frequency segmentation filtering and frequency compensation.Rotation frequency segmentation filtering changes the filter's parameters to make all the rotation frequency to be in the filter's stopband,which offsets the rotation frequency factor directly.Frequency compensation based on the on-board resources of the unbalance measurement system itself,identificates the transfer function of low-pass filter by in-situ method and compensates the frequncey characteristic of low-pass filter by the inverse function of the actual transfer function.At last,digital simulation and field experiment are conducted to verify the effectiveness of in-situ frequency compensation method.The software of the measurement system is designed based on the demand analysis.The microprocessor realizes reak time data acquisition and communication.The master computer realizes friendly graphic user interface by the multi-thread architecture.