A Study On Open Embedded Auto-balancing Control System For Rotating Machinery

On-line rotor auto-balancing has been a hot area of engineering research and development over the years, which has a great potential of innovation. This technology can not only eliminate the dynamic random imbalances and reduce real-time equipment vibrations during rotor's running period, but also can effectively extend the operation cycle of rotating machinery, decrease malfunction downtimes, save maintenance costs, which has a very high economic value. Moreover, its potential application area is extremely broad. According to the reports so far, the applications cover not only large mechanical equipment, like compressors, turbines and centrifuges, but also highly precision rotary mechanism such as the hard disk drive heads. In fact, any machinery needs to maintain the stable operation of rotating facility is the latent target, so the development and application prospects of rotor on-line auto-balancing technology are very bright.As a part of the National Natural Science Foundation Project:"the theory and method for complex mechanical systems modeling, simulation, operation optimization and self-recoverling control" (No.50635010), this research project first summarized several typical auto-balancing system, and then discussed several industrial field problems auto-balancing control system may encounter and their solutions under the guidance of self-recovering theory. The simulation studies of self-recovering control and signal processing algorithms for auto-balancing were done using a custom-built mathematical higee rotor model. Three different on-line auto-balancing control systems were built up respectively for three different kinds of balancers which are the continuous injection-discharge liquid balancer, the single injection liquid and the electromagnetic balancer. All the systems were physical tested through the experimental platform. An embedded usage customized auto-reasoning fault diagnosis system for rotating machinery got studied as a part of wellappointedness of the minimum auto-balancing control system. Finally, a prototype control system with independent intellectual property was completed, which may build the initial foundation for the localization and industrialization of this bright technology. The main taskes of this project contained:(1) Comparison and analysis of typical auto-balancing systemsThere are three kinds of auto-balancing system in the DSE Center of Beijing University of Chemical Technology, which are:the continuous injection-discharge liquid auto-balancing system, the single injection liquid auto-balancing system, and the electromagnetic auto-balancing system. They represent the main realization forms of auto-balancing theory. Based on the review and comparison, system structures were analyzed, the balancing principles were investigated, and some key issues on auto-balancing control system, which need to be solved in the industrial application field, were come into question.(2) Hardware realization of open embedded auto-balancing systemDust, vibration, pollution or narrow install space, are just some cases of the adverse conditions which may exist in the industrial field. Hence, PC/104 bus was chosen as the system hardware platform. After the system function division, hardware modules were designed "from the top to the bottom". According to the different types of balancers and sensors, corresponding expansion modular boards can be loaded to the minimum function system. In this way, the existing resources could be maximizing used.(3) Simulation and optimization of auto-balancing control algorithmsThe auto-balancing control process of an industrial rotor has its own particularity, manifested in:1) only a very small range of overshoot is allowed, otherwise it may cause malfunctions. In general, no overshoot is demanded; 2) the transition oscillation is a kind of interference to the balance ability of the balancer, hence it should be inhibited as much as possible; 3) With the change in production load or other external conditions, the vibration range of rotor system may be different, balance control system needes smooth transitions between multiple setpoints. On the other hand, the whole control process will be realized in an embedded system which has limited available hardware resources. So in this project, the Iterative Learning Control (ILC) algorithm was highly focused on. Vector Geometry was used to improve the basic algorithm of ILC. Then a mathematical model of higee rotor was achieved. Based on it, the standard PI increment control algorithm, the basic ILC algorithm and its modification algorithm with vector analysis got compared. With the conclusions of theory analysis and simulation studies, the algorithm structure of ILC suitable for auto-balancing control was eventually established, and the ranges of control parameters were given out.(4) Extraction and processing of unbalance signalUnbalance signal extrction is a big issue in balancing control system, which has a direct impact on the final control effects. In particular, to avoid the "wrong direction" phenomenon during the control process greatly dependents on the precision and accuracy of this extraction progress. Due to the limited hardware resources, time-varying parameters and other factors, adaptive filtering algorithm was used here, and the basic LMS algorithm has been modified. An international open-source database of vibration signal was used as the benchmark to test and compare the adaptive signal processing ability of the basic LMS algorithm, its modification algorithm and the Wiener filter. The results showed that the modified LMS algorithm based on vector analysis had a good balance in the computational complexity, the system resource consumption, the signal extraction precision and other indexes.(5) Construction of auto-reasoning mechanism for rotating machinery fault diagnosis systemThere are so many reasons leading to mechanical vibration that not any one can be inhibited by the auto-balancing system. As an extension module of this open embedded auto-balancing system, the design target of rotating machinery auto-reasoning fault diagnosis system is to distinguish the vibration reason in order to determine whether the auto-balancing system run or not. Moreover, it may provide a guidance of possible fault cause to on-site operators. The degree of auto-reasoning was substantial increased by rough set simplification, rule property restructured, and fuzzy information.(6) The prototype of open embedded auto-balancing control systemBase on the previous studies, the system structure was improved step by step, finally achieved its original prototype.