Electrical audio signal processing systems and devices – Acoustical noise or sound cancellation – Counterwave generation control path
Reexamination Certificate
1998-05-20
2001-03-27
Isen, Forester W. (Department: 2644)
Electrical audio signal processing systems and devices
Acoustical noise or sound cancellation
Counterwave generation control path
C381S071110, C381S071500
Reexamination Certificate
active
06208739
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the invention relates to the problem of rejecting exogenous disturbances acting on dynamical systems (or “plants”). In particular, the invention pertains to a method and system for noise and vibration suppression that does not require measurement of the actual disturbance.
Heretofore, several methods required a priori knowledge of the spectral characteristics of the disturbance in addition to models of all four paths in the plant including actuators and sensors shown in
FIG. 1
, that is, G
zw
(the “primary path”), G
zu
(the “secondary path”), G
yw
(the “reference path”) and G
yu
(the “feedback path”). These methods are described in reference
5
of the appended listing of references. Other methods used for active noise control described in references
1
,
2
,
6
through
12
, do not require knowledge about the disturbance but often require a direct measurement of it, and require an FIR (finite impulse response) or IIR (infinite impulse response) model of G
zu
. These methods use instantaneous measurements for adaptation and do not accurately characterize the effect of the control over a window of time.
Despite the need for a method and system that can adapt based on retrospective information obtained from sensors to account for the effect of the system and method over a window of time, none was known. Thus, there was the need for a method and system using a retrospective performance evaluation in a special heretofore unknown form. A need also existed to determine an explicit step size or well-defined distance based upon the retrospective performance evaluation.
The disclosed method and system of this invention is applicable to a wide class of disturbance rejection problems, including but not limited to active noise and vibration control. Other applications include command-tracking in which the command is viewed as a disturbance signal whose effect is rejected in the output error signal.
The present method does not require knowledge of the disturbance spectrum nor a measurement of it, and only requires the numerator of the ARMARKOV model G
zu
denoted by the Toeplitz matrix B
zu
.
The present method uses ARMARKOV models to describe the plant including sensors and actuators as well as the disturbance rejection controller. These models are described below.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method and system that evaluates performance based upon past data and determines an explicit step size or distance for adaptation, for differentiation from existing methods.
In contrast to the prior art, the method and system for achieving such rejection comprises of a set of sensors which measure the outputs of the plant for which the effect of the disturbance is to be minimized, an optional additional set of sensors which measure other outputs of the plant, converters that digitize analog signals from the sensors, a microprocessor capable of storing data from the converters and performing the calculations described in the method herein, converters that create command signals from the results of the calculations of the microprocessor, and actuators that act on the plant based on these command signals. A graphical representation of the system according to the invention is given in FIG.
1
.
The plant with sensors and actuators comprise the four block unit in
FIG. 1
, while the microprocessor implementing the method described herein, or “controller”, is the lower block marked G
c
. The exogenous disturbance is denoted by w(k), the outputs of the system for which the effects of this disturbance are to be minimized or “performance measurements” by z(k), the additional measured outputs of the system or “feedback measurements” by y(k) and the signals generated by the controller or “control signals” by u(k). The paths from the two sets of inputs to the plant, namely, w(k) and u(k), to the two sets of outputs of the plant, namely, z(k) and y(k) are denoted by G
zw
, G
zu
, G
yw
and G
yu
.
For a more complete understanding of the present invention, reference is made to the following detailed description when read in conjunction with the accompanying drawings wherein like reference characters refer to like elements throughout the several views, in which:
REFERENCES:
patent: 5796920 (1998-08-01), Hyland
patent: 6005952 (1999-12-01), Klippel
Sievers and von Flotow, Comparison and Extensions of Control Methods for Narrow-Band Disturbance Rejection, IEEE Transactions on Signal Processing vol. 40, p. 2377-2399.
Messner and Bodson, Design of Adaptive Feedforward Algorithms Using Internal Model Equivalence, Int. Journal of Adaptive Control and Signal Processing, vol. 9, p. 199-212.
Elliott, et al., A Multiple Error LMS and Its Application to the Active Control of Sound and Vibration, IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. ASSP-35, No. 10, p. 1423-1434.
Jiang, et al., Adaptation for Active Noise Control, IEEE Control Systems, Dec. 1997, p. 36-47.
Akers, et al., Time-Domain Identification Using ARMARKOV / Toeplitz Models, Proc. Amer. Contr. Conf., Jun. 1997, p. 191-195.
Akers, et al., ARMARKOV Least-Squares Identification, Amer. Contr. Conf., Jun. 1997, p. 186-190.
Venugopal, et al., Adaptive Disturbance Rejection Using ARMARKOV Systems Representations, Proc. of the 36 th IEEE CDC, Dec. 1997, p. 1884-1889.
Bernstein Dennis S.
Venugopal Ravinder
Burns Barbara M.
Isen Forester W.
Pendleton Brian Tyrone
The Regents of the University of Michigan
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