Rapidly converging multichannel controllers for broadband noise and vibrations

Applications are given of a preconditioned adaptive algorithm for broadband multichannel active noise control. Based on state-space descriptions of the relevant transfer functions, the algorithm uses the inverse of the minimum-phase part of the secondary path in order to improve the speed of convergence. A further improvement of the convergence rate is obtained by using double control filters for elimination of adaptation loop delay. Regularization was found to be essential for robust operation. The particular regularization technique preserves the structure to eliminate the adaptation loop delay. Depending on the application at hand, a number of extensions are used for this algorithm, such as for applications with rapidly changing disturbance spectra, applications with large parametric uncertainty, applications with control of time-varying acoustic energy density

Adaptive multichannel control of time-varying broadband noise and vibrations

This paper presents results obtained from a number of applications in which a recent adaptive algorithm for broadband multichannel active noise control is used. The core of the algorithm uses the inverse of the minimum-phase part of the secondary path for improvement of the speed of convergence. A further improvement of the speed of convergence is obtained by using double control filters for elimination of adaptation loop delay. Regularization was found to be necessary for robust operation. The regularization technique which is used preserves the structure to eliminate the adaptation loop delay. Depending on the application at hand, a number of extensions are used for this algorithm. For an application with rapidly changing disturbance spectra, the core algorithm was extended with an iterative affine projection scheme, leading to improved convergence rates as compared to the standard nomalized lms update rules. In another application, in which the influence of the parametric uncertainties was critical, the core algorithm was extended with low authority control loops operating at high sample rates. In addition, results of other applications are given, such as control of acoustic energy density and control of time-varying periodic and non-periodic vibrations

Studi Komparatif Sistem Kendali Bising Aktif Umpan Maju Menggunakan Filter Adaptif Berbasis LMS

In this paper, we discuss simulation and experimental study of the application of Least Mean Square (LMS) based adaptive filter algorithm in active noise control. A number of adaptive filter algorithm based on LMS are investigated, namely Preconditioned Least Mean Square (PLMS), Filtered-reference LMS (FxLMS) and two variants of Filtered-error LMS (FeLMS) algorithms. Active noise control simulation for attenuating recorded blower noise is performed. In case of active noise control experiment, a disturbance is generated by adding three sinus waves with different amplitudes and phases using digital signal processor TMS320C6701, and passing them through primary path. Comparison of the four algorithms is carried out by measuring the performance (in terms of resulting attenuation level) and speed of convergence. Simulation and experiment results demonstrate that PLMS provides the best performance and speed of convergence

Optimal controllers and adaptive controllers for multichannel feedforward control of stochastic disturbances

A time domain formulation for the multichannel feedforward control problem is used to derive an optimally condition for the least squares controller. It is also used to motivate an instantaneous steepest descent algorithm for the adaptation of the controller, which is known as the filtered error LMS algorithm. The convergence rate of this algorithm is limited by the correlation properties of each reference signal, their cross-correlation properties and the dynamics and coupling within the plant response. An expression is then derived for the transfer function of the optimum least squares controller. This suggests a new architecture for the adaptive controller whose convergence rate is not limited by the factors mentioned above. A set of white and uncorrelated reference signals are generated to drive a modified matrix of control filters, whose outputs are multiplied by the inverse of the minimum phase part of the plant response matrix before being fed to the physical plant. The error signals from the plant are then used to update this controller after being fed through the time-reverse transpose of the all-pass part of the plant matrix. The relationship is also discussed between this architecture and that using a singular value decomposition of the plant response, which is used to control tonal disturbances

Active vibration control systems in the frequency and sub-band domain.

Active noise and vibration control has been the subject of intense study in the last two decades due to the increased speed in digital signal processors and the technological development and manufacture of smart materials. This dissertation analyzes an active control system using adaptive digital signal processing techniques and applies it to the vibration reduction of hard disk drives (HDD). Specifically, this work focuses on the implementation of the adaptive algorithm in the frequency and sub-band domains for performance improvement.In this dissertation, selective adaptation in the frequency domain is proposed to alleviate the constructive interference associated with a feedback active control system. A new sub-band adaptive filter architecture without a signal path delay is proposed, and the associated adaptive algorithm is derived. This delayless sub-band algorithm can be applied to the active control systems to improve the convergence rate and trade-off the performance from the various sub-bands. The resulting side effect of the error path delay of the analysis filter bank is analyzed, and two compensation methods are proposed to increase the performance. The frequency domain method and the sub-band decomposition technique are then combined to improve the overall performance. The single-channel active control system is extended to the multiple-channel active control system to reduce the vibration of complex mechanical structure. The optimal performances of three variants of the feedback control system have been derived in terms of the correlation coefficients of the primary disturbances and the impulse responses of the secondary paths. Real time and simulation results are performed to verify the efficiency of the proposed algorithms and techniques