Time average feedforward control techniques for time varying systems
Adaptive FeedforWard algorithms have been successfully applied in the active control of sound and vibrations~ Current approaches, such as the Filtered-X Least Mean Square algorithm, are limited in adaptability and applicability by the computationally intensive system identification process. The Time Average approach is a technique that promises to be a major advance in the active control of sound and vibration. This approach is based on statistical estimates of the error signals, and does not require having previous knowledge of the system. A new minimization algorithm has been developed, which enhances the performance of the Time Average controllers. A new technique to estimate the cost function is also presented. This technique is called the Real Time Cost Function Evaluation method. Based upon these new controller design concepts, single channel and multi-channel controllers were developed and experimentally tested. The experiments included control of a harmonically excited, simply supported beam, and the control of inlet tonal noise radiated from a JT1SD-l turbofan engine.