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Research on Technology of High-Precision Dynamic Balancing Measurement and Automatic Balancing for Rotors

Author: TaoLiMin
Tutor: WenXiSen
School: National University of Defense Science and Technology
Course: Mechanical Engineering
Keywords: Rotating machine Rotor Dynamic balancing Narrowband tracking filter Automatic balancing Balancing head Automatic balancing strategy Influence coefficient method
Type: PhD thesis
Year: 2006
Downloads: 1211
Quote: 18
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Rotating machine is an important part in mechanical system, which has a great significance in defensive and civil domain. Imbalance is a common problem for rotors, and also the principal reason of faults in rotor systems. The research of dynamic balancing technology has important scientific and engineering significance. With the rapid evolvement of electronics, computer, and measurement, dynamic balancing technology has been developed greatly in recent years, which helps to build up a trend of high-speed, high-efficiency, and high-reliability for rotor systems. At present, related researches are centering on dynamic balancing measurement, non-symmetrical/non-planar modal rotor balancing, balancing without trial weights, automatic balancing, and so on. Aimed to increase balancing precision and efficiency for rotors, this dissertation analyzes dynamic response of imbalance at first, discusses the related key technologies further in dynamic balancing measurement and automatic balancing such as narrowband tracking filtering, automatic balancing strategy, and so on. The main contents are as follows:1. In order to interpret the relationship between vibration response and variables of imbalance together with parameters of system in typical rotor under constant acceleration, such as planar rotor, rigid rotor, and flexible rotor, the main influencing rules of system parameters on the transient imbalance response are studied deeply by theoretic analysis and numerical simulation on foundation of the existing research results summarized and concluded. The analysis results indicate that the vibration fractional factor with rotating frequency has a close relationship with both rotating speed of rotor and damping of bearing under constant acceleration. When rotating acceleration is small and damping is large, the transient response is not sensitive to the variation of rotating speed; otherwise the imbalance response with constant acceleration and the response in stable state will build up obvious differences near critical rotating speed.2. In order to adapt to the requirements of high-precision dynamic balancing measurement with rotating speed variation and to isolate the vibration fractional factor with rotating frequency from imbalance response precisely and quickly, two new types of analog tracking filtering technologies are deeply studied: (1) the tracking filtering method using switched-capacitor is deduced from the equivalent principle between switch & capacitor and resistance, and a new narrow-brand tracking filter using switched-capacitor is designed accordingly; (2) the correlative tracking filtering method is deduced from the correlation principle, and an analog narrow-brand tracking filter using Multiplying Digital-to-Analog Converter (MDAC) is designed accordingly.3. In order to realize fast and precise control of balancing head, two special types of automatic balancing strategies with the corresponding algorithms are brought forward for balancing head in polar coordinates: (1) an alternate-coordinate optimization method with multiple circulations is built up to improve alternate-coordinate optimization method for single plane in existence, and widens its application to automatic balancing for double planes which proves to be able to gain global optimal solution;(2) a fast automatic balancing strategy and its recursive algorithm are presented based on the influence coefficient method, which restrains the influences on balancing precision from vibration noises, measurement errors, and control errors rapidly and effectively.4. In order to gain the distributing condition of imbalance on rotor quickly and precisely, the signal processing technologies such as programmed amplifying, programmed integrating, equal -angle sampling with outer triggering, and precise imbalance solving are studied deeply, and a portable high-precision dynamic balancing measurement system is developed. To avoid multiple on/off process when balancing off-line and to compensate the random imbalance in running timely, two new types of balancing head structures are advanced, of which the balancing head based on the principle of permanent-magnetic-induction stepping motor has a compact structure and a high precision and the balancing head driven by permanent-magnetic stepping motor is easier to realize; and an automatic balancing system based on infrared control signal transmission is designed and developed accordingly.5. The performances of the developed dynamic balancing measurement system are tested, and then the system is applied to dynamic balancing of low-speed fan rotor, high-speed gyro rotor, and magnetic-suspended rotor respectively. The balancing effects are satisfactory, which indicate that the system has high measurement precision when applied to both dynamic balancer with hard/soft bearing and field dynamic balancing. The automatic balancing strategy based on alternate-coordinate optimization method and the rapid automatic balancing strategy based on the influence coefficient method are applied to the automatic balancing experiment of rotor with single plane, which reveals that alternate-coordinate optimization method is easy to use and safe to operate, and that the rapid automatic balancing strategy based on the influence coefficient method has high balancing precision and balancing efficiency.In sum, this dissertation analyzes the characteristics of imbalance response in typical rotors deeply at first, and brings forward two types of analog narrow-band tracking filtering methods and two special types of automatic balancing control strategies with the corresponding algorithms, then develops a portable high-precision dynamic balancing measurement system, and then presents two new types of balancing head structures, and develops an automatic balancing system based on infrared control signal transmission afterwards, and gives out further imagination for future research in the end.

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