Research On Active Vibration Contral Of Rotor System Using Magnetorheological Fluid Damper

Rotating machines represent the largest and most important class of machinery including electrical motors, machine tools, compressors, turbo machinery and aircraft gas turbine engines. These systems are affected by exogenous or endogenous vibrations produced by unbalance, misalignment and cracks etc. Rotor vibration is very important for both analysis and safety of rotating machines. Reduction of rotor vibration is very important for safe and efficient functioning of these rotating machines. The common technique for vibration control is vibration damping. Magnetorheologiacal Fluid (MRF) damper, which provides adjustable damping over a wide range of frequencies without large power requirements. It has been successfully used in civil engineering applications. MRF draw attentions of specialists in rotor vibration and is one of the more promising new vibration damping devices. The aim of this work is the analysis and design of the intelligent control strategy and techniques for vibration reduction in a rotor system using shear mode MRF damper.The outline of this thesis is as follows:(1) Passive and active vibration control technologies for a rotor system have been introduced while active control strategies for rotor vibration were studied and applications of Magnetorlogical fluid damper in rotating machinery were presented. A shear mode magnetorheological fluid damper was analyzed and designed to control the vibration. A dynamic model of the MR damper-Rotor system was built and simulated with Matlab/Simulink to analyze its vibration characteristics and the vibration reduction effect.(2) Three active control strategies were proposed based on simulation and analysis:on-off and sectional control based on rotor speed phase, in which current was adjustable according to rotor speed detected; a close loop control strategy based on vibration amplitude while rotor speed and amplitude were monitored in real time, was presented in which current was adjustable according to vibration amplitude. Rotor vibration was well controlled under desired value. An optimization seeking control strategy using pattern search method was proposed and designed, in which an appropriate control current was determined to keep the rotor vibration under desired value.(3) A control system was designed and constructed on a one span rotor bench and a control platform for one span rotor was developed in Labview. Experiment validations on the effectiveness of the proposed control strategy were conducted. Experiment results showed that rotor vibration caused by unbalance can be well controlled whether in resonance region(80%) or in non-resonance region(30%). Current is adjustable according to related parameters (rotor speed or amplitude). Furthermore, an appropriate current is determined using optimization seeking strategy.(4) The control strategies proposed can be extended to a two-span rotor system. The control experiment system was constructed on a two span rotor bench. Based on control platform of one span rotor, a parallel and independent control platform for a two-span rotor system was developed to control each span non-interfering and respectively. Experiment results showed that rotor vibration caused by unbalance is well controlled in two-span rotor system(first critical speed region 37%, second critical speed region 42%) with appropriate current which obtained by optimal current approximate controller.(5) To reflect advantages of optimization seeking control strategy presented in this thesis and to validate the intelligent optimization control for complex rotor system with high nonlinearity and uncertainty, detailed experiments about the performance of optimization seeking control strategy were developed on two span rotor vibration control platform. The influence on accuracy,rapidity and stability of optimization seeking control for rotor vibration are analyzed through different control parameters(different desired values, different tolerances and different current search steps). The stability of optimization seeking control process is affected with different accuracy(different tolerances). The rapidity of optimization seeking control is better with longer current search step, but longer search step may affect the accuracy and stability of optimization seeking control. It is necessary to balance these three control performance requirements(accuracy, rapidity and stability) in actual rotor vibration. In the premise of vibration control stability, rapidity and accuracy of control are improved as far as possible.The strategies and control system presented in this work can be extended to multi span (more than three or four span) rotor system. It provides a powerful technical support for the extension and application in target and control for shafting vibration. It can also be applied in other vibration control techniques such as anti-swirl.