Methods, apparatus and systems for real time identification and control modes of oscillation

DETAILED DESCRIPTION The present invention provides a novel approach for active control of detrimental instabilities in practical combustors or the excitation of beneficial acoustic oscillations in combustion and energy intensive processes, for example.
The present invention overcomes the above-described and other problems in prior active control systems.
The invented system comprises a sensor, a processing unit including an observer and a controller, and an actuator.
The observer analyzes the signal supplied by the sensor and determines, virtually in real time, the modal functions (and hence the amplitudes and phases) and frequencies of the excited combustor modes.
Based on the modal functions and frequencies, the controller adaptively determines a gain and phase shift for each mode or uses a predetermined gain and phase shift, and combines the modes to generate a time-varying control signal that is fed to the actuator.
Based on the control signal, the actuator produces a secondary system of oscillations within the combustor that tends to damp the instability.
Alternatively, the controller can assign a phase and a gain to the actuator signal in a manner that excites oscillations in the process for applications where such oscillations produce beneficial effects.
The observer of this invention uses a frequency domain analysis that avoids the time consuming process of frequency scanning commonly used in fast Fourier transform (FFT) and Wavelets transformers.
Instead, the unknown frequencies and amplitudes of the modes of oscillation are determined by the processor using a pair of integrals that are modified versions of Wavelet Transforms, whose integration limits are changed continuously.
The frequency of the largest amplitude, dominant mode is determined first in a rapidly converging solution approach.
Once the dominant mode has been determined, it is effectively subtracted from the sensor signal as are the other modes as presently known by the observer, and the mode characterization procedure is repeated to determine the characteristics of the mode with the next largest amplitude