High Precision And Low Speed Dynamic Balancing Measurement System Design

In order to improve missile warheads' flight control precision,it's necessary to test them at the speed of 60 to 120 rpm(revolutions per minute),with a high-precision testing method of measuring dynamic unbalance on vertical dynamic balancing machine.The testing speed of the general dynamic unbalance measurement systems is between 300 and 3000 rpm,and its accuracy at a low speed cannot meet the practical needs of missile warheads.In order to satisfy the production demand of missile warheads testing,the thesis focuses on the dynamic unbalance measurement system working at the speed of 60 to 120 rpm.Based on the basic theory of vertical dynamic balancing machine,the key techniques of the measurement system were discussed when it's utilized at a low speed,namely the means of detecting the low-frequency vibration signal accurately,and the methods for solving the amount of unbalance.The technique of filter based on hardware and the methods of signal processing by software were deeply studied to get the low-frequency vibration signal's amplitude and phase from strong noise.Combined with some experiments,the way to apply the two key techniques has been mastered.After detailed analysis and comparison of several ways to apply the two key techniques, a new design of dynamic unbalance measurement system has been proposed.The system uses MCU as its control cell,and realizes the execution of circuit with the techniques of DDS (Direct Digital Synthesis),programmed gain control,tracking-filter,phase sensitivity demodulation,synchronous whole-periodic sampling and so on.The system uses the optimized ICM(influence coefficients balancing method) to solve the amount of rotor's dynamic unbalance.According to the system design,the printed circuit has been produced,the program for driving the hardware composed,the software for processing digital signal and the programmed algorithm for calculating dynamic unbalance completed.The function and performance of the measurement system has also been proved by experiments.In the design of circuit,new achievements in communication and power systems such as DDS, correlation-filter and synchronous whole-periodic sampling have been successfully combined with dynamic unbalance measuring,which contributes to the collection of several channels signals in-phase.At the same time,the method of using the PWM module in the sampling units(pulse width modulation,provided by uPSD3234A) to replace PLL(Phase-Locked Loop) has been proposed.It simplifies the printed circuit,and enhances the accuracy of signal sampling,which makes it of initiative and practical value.In the design of the software for upper computer,using the combination method of frequency spectrum analysis and whole-periodic sampling based on software to analyze the digital signal collected has been proposed,which solves the problem of near-frequency noise interference at a low speed,and improves the accuracy of detection for vibration signal.The design also improves ICM in the aspects of static-couple separation and compensation by software,and makes the ratio of plane-separation smaller.The e_mar(up to the smallest of the remaining unbalance)of the measurement system is less than 2g·mm/kg at the speed of 60 to 120 rpm;the URR(unbalance reduction rate) is more than 95%;the error of centroid's setover is less than 0.038mm;the relative error of couple unbalance is less than 0.95%;and the ratio of plane-separation is less than 1/44.The experiment results show that the measurement system satisfies the requirements for testing missle warheads.