Active Vibration Control Of Distributed Structures Suffering From Complex Excitations

The active vibration control of structures suffering from complex excitations is aninterdisciplinary subject involving the scientific research fields of structural dynamics, control theory,signal processing, computer application, etc. The kinetic study of distributed structures suffering fromcomplex excitations has long attracted the attention of scholars. However, complex excitationsprovide this type of structure with nonlinear dynamical behaviors such as bifurcation, chaos, etc.These complicated phenomena are induced by the infinite dimensional characteristic of continuousstructures, and it is easy to induce observation and control spillover when discrete time controlalgorithms are applied. This problem will influence the system’s instability. Therefore, the system’srobustness and anti-jamming performance should be further considered. In general, studying problemsinvolving distributed structures suffering from complex excitations is a great challenge, with a strongengineering background and scientific significance.Based on the vibration control of a wind tunnel model suffering from a transonic wind load, thisstudy examines the dynamical phenomena and control methods for a distributed structure sufferingfrom complex excitations. The main research contents and contributions are as follows:1. A control algorithm based on the input estimation method is studied, using a system withdeterminate model parameters. An unknown disturbance is introduced into the controllerdesign to improve control effect. Systems can be converted to a new state equation withoutan explicit disturbance in combination with a random walk model. Thus, it is easy to acquirethe estimated value of the new state equation by using a Kalman filter, which contains theestimated value of the unknown disturbance. Therefore, the estimated value can be used inthe linear quadratic gauss method to express the math of a controller with a disturbance.2. An anti-aliasing filter and high-order low-pass digital filter are introduced to avoid theinfluence of noise induced by the high-order mode of the distributed structures. The linearrelationship is regarded approximately as the phase-to-frequency characteristic in thepass-band of the filters. Considering the invariant time delay induced by the filters, thestability of the controlled system is studied, and the stability regions of the system areconfirmed by the stability switch theory.3. Delay usage and elimination methods are studied to design controllers adapted to the case ofsystems with output time delays. From the aspect of delay usage, an appropriate time delaycan be determined according to the decay rate of the impulse response. The controlled effect can be greatly improved through a time delay reset. From the aspect of delay elimination, adiscrete state equation is constructed without an explicit time delay, and is combined with alinear quadratic control method to obtain a controller with a time delay.4. Considering the nonlinear phase-to-frequency characteristic in the transition bandwidth offilters, the problem induced by a system’s variable time delay is studied. To deal with thisnew problem, the variable time delay system is converted to a fixed one using a phasecompensation method. A credible output time series is established for further study on theelimination of overall delay.5. A time series forecasting method is studied, and an ARMA model is established based on thesystem output. To obtain a serial output without a time delay, the model is transferred to theAR form, and is solved using a stochastic approximation method. This process essentiallyeliminates the influence of time delay and provides an effective controller input for thecontrol algorithm independent of the model parameters.6. Based on an actual engineering application and experimental research, an engineeringcontrol system and ground test system are established. Application software is developed forthe control system based on the Borland C++software development platform. In addition,the connections between a computer and a constant current source, power amplifier, andother peripheral equipment are established by using a data acquisition card (DAQ2206). Toprovide protection for real-time applications, multithreading technology is adopted to ensurecomputer and data transfer synchronization.7. The proposed control methods are validated on the ground test system, and some of them areapplied in the engineering control system.