Eigenvalue equalization applied to the active minimization of energy density in a mock helicopter cabin
04 May 2007-Journal of the Acoustical Society of America (Acoustical Society of America)-Vol. 121, Iss: 5, pp 3179-3179
TL;DR: In this article, the authors developed a method that equalizes the eigenvalues of the system over the operating frequency range, leading to more uniform performance for active noise control in a helicopter cabin.
Abstract: A number of applications in active noise control require the ability to control and track multiple frequencies. If a standard filtered‐x algorithm is used, the system must be designed to be stable for the slowest converging frequency anticipated, thereby leading to reduced overall performance of the system. Previous work has focused on overcoming this through development of a method that equalizes the eigenvalues of the system over the operating frequency range, leading to more uniform performance. The current work has built on the previous work to extend the method for implementation in systems that control the acoustic energy density. Minimizing energy density has been shown to have favorable performance characteristics when used for controlling enclosed acoustic fields. Thus, combining the approach of equalizing the system eigenvalues with energy density control leads to a system that incorporates the advantages of both methods. The control approach is demonstrated through implementation in a mock helicopter cabin, to demonstrate the favorable convergence characteristics, along with the global control of the field.
Citations
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01 Sep 2011
TL;DR: In this paper, an alternative method is presented that avoids the disadvantages of these methods, namely the additional complex hardware, and the need to obtain detailed information of the uncertainties, and it is shown that the technique leads to improved performance in terms of robustness and the amount of reduction of the error signals.
Abstract: Model errors in adaptive controllers for reduction of broadband noise and vibrations may lead to unstable systems or increased error signals. Previous work has shown that the addition of a low-authority controller that increases damping in the system may lead to improved performance of an adaptive, high-authority controller. Other researchers have suggested to use frequency dependent regularization based on measured uncertainties. In this paper an alternative method is presented that avoids the disadvantages of these methods namely the additional complex hardware, and the need to obtain detailed information of the uncertainties. An analysis is made of an active noise control system in which a difference exists between the secondary path and the model as used in the controller. The real parts of the eigenvalues that determine the stability of the system are expressed in terms of the amount of uncertainty and the singular values of the secondary path. Based on these expressions, modifications of the feedforward control scheme are suggested that aim to improved performance without requiring detailed uncertainty measurements. For an active noise control system in a room it is shown that the technique leads to improved performance in terms of robustness and the amount of reduction of the error signals.
8 citations
TL;DR: Modifications of the feedforward control scheme are suggested that aim to improve performance without requiring detailed uncertainty measurements, and the need to obtain detailed information of the uncertainties is avoided.
Abstract: Model errors in adaptive controllers for reduction of broadband noise and vibrations may lead to unstable systems or increased error signals. Previous research on active structures with small damping has shown that the addition of a low-authority controller which increases damping in the system may lead to improved performance of an adaptive, high-authority controller. Other researchers have suggested to use frequency dependent regularization based on measured uncertainties. In this paper an alternative method is presented that avoids the disadvantages of these methods namely the additional complex hardware, and the need to obtain detailed information of the uncertainties. An analysis is made of an adaptive feedforward controller in which a difference exists between the secondary path and the model as used in the controller. The real parts of the eigenvalues that determine the stability of the system are expressed in terms of the amount of uncertainty and the singular values of the secondary path. Modifications of the feedforward control scheme are suggested that aim to improve performance without requiring detailed uncertainty measurements.
5 citations