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(11) | EP 0 555 248 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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ACTIVE VIBRATION CONTROL SYSTEM WITH MULTIPLE INPUTS SYSTEM ZUR AKTIVEN REGELUNG VON SCHWINGUNGEN MIT MEHREREN EINGÄNGEN SYSTEME ACTIF DE REGULATION DE VIBRATIONS AVEC ENTREES MULTIPLES |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
Field of Invention
[0001] The invention relates to a system for actively controlling vibration. In common with previous methods it uses multiple actuators and sensors, but the improved method drives the actuators using output wave generators each of which is responsive to at least two input signals. In particular, unlike previous methods, the invention can be applied to the control of vibration from multiple sources irrespective of the degree of correlation between the sources.
Background to the Invention
[0002] In the following the use of the word vibration shall include sound and other similar linear disturbances.
[0003] There have been many publications relating to the active control of vibration in solids and in fluids. They use one or more actuators to produce secondary vibration that tends to cancel an unwanted vibration in some region. Sensors in this region produce signals representative of the residual vibration. These signals (the residual signals) are used in a control system together with input signals to adjust the signals sent to the actuators.
[0004] Active control systems can be broadly categorised according to the type of input signals used. The first type uses input signals which are both time and amplitude related to the primary vibration or the combination of both primary and secondary vibration. The second type uses input signals which are time related to the primary vibration but contain no amplitude information.
[0005] This second type of system is usually used for controlling periodic or tonal vibrations and an example is described in UK patent 1,577,322 (Active Attenuation of Recurring Sounds, G.B.B Chaplin).
[0006] When there is more than one source of vibration it is sometimes possible to use one control system each source, provided that the sources are uncorrelated with each other.
[0007] Another method treats the vibration as if it were coming from a single source and to use a fast-adapting control system to compensate for the modulations caused by the interactions of the sources ( UK patent 2,132,053 (Warnaka & Zalas), UK patent 2,126,837 (Groves), UK patent 2,149,614 (Nelson & Elliot). This will only work if the sources are correlated over the timescale of the adaption process. It could not be used, for example, for controlling aircraft propeller noise when the synchrophaser is switched off, since modulations are then too rapid.
[0008] There are many applications where the vibration is produced by vibration sources which are at least partially correlated. One example of this is the generation of road noise inside a vehicle. There is some correlation between the vibration produced from each wheel as a result of road uneveness and in addition it is not always possible to position vibration sensors which are responsive to one wheel only.
[0009] Another example of this is when the vibration sources are tonal in nature. If the frequencies of the sources are very close together then the cross-correlation of the signals from the individual sources must be calculated over a long time before the correlation becomes negligible. There have been attempts to separate the signals in a reduced time by using phase information from the different sources (for example PCT/GB89/00913 (Eatwell & Ross) ), but this relies upon the frequencies remaining fixed and separate over the measurement time and makes the assumption that the sources are uncorrelated over some specific time period.
[0010] In many real applications not only do the frequencies change, but they can overlap. This is the case for example when two machines are connected by a clutch which can slip, when they are governed to run at the same nominal speed, or when they are linked with a control system such as a synchrophaser for aircraft propellers. In these cases it is often impossible to identify accurately which vibration is due to which source using the input signals only.
Summary of the Invention
[0011] According to the invention, an active vibration control system comprises:
at least two input sensors which generate first signals related to the phase and/or the amplitude of a primary vibration field or the sources which generate the primary vibration field,
a plurality of actuators driven by second signals which produce a secondary vibration field,
a plurality of monitoring sensors responsive to the combination of the said primary and secondary vibration fields and which produce third signals,
a controller including one output waveform generator for each second signal wherein each output waveform generator is responsive to the said first signals and generates one of the said second signals so that the combined effect of the second signals is that the vibration in a region, which is excited by the said primary and secondary vibration fields, tends to be reduced, wherein the controller adapts the output waveform generators so that the vibration in the region is maintained at a reduced level,
characterised in that said adaption of the output waveform generators takes account of the cross correlation matrix of the first signals and/or the cross correlation matrix between the first and third signals.[0012] Some input sensors may sense vibration in the field produced by vibration sources or may be associated with or linked to the source in such a way as to produce a signal indicative of the activity of the source which produces the vibration (e.g. rotation of a turbine).
[0014] Some or all of the adaption updates may be scaled by the reciprocal of the largest eigenvalue of the cross correlation matrix of the first signals.
[0015] Alternatively some or all of the adaption updates may use a modified form of the inverse of the cross correlation matrix of the first signals.
[0016] Some or all of the adaption updates may use a matrix derived from the eigenvectors and/or the eigenvalues of the cross correlation matrix of the first signals.
[0017] Some or all of the adaption updates may use a matrix which is selected to minimise the one-step-ahead residual vibration in the region.
[0018] Changes in the first signals may be cross correlated to form a cross correlation matrix of the changes in the first signals, and some or all of the adaption updates may use a matrix which is selected at least partly with reference to the said cross correlation matrix of the changes in the first signals.
[0019] Changes in the third signals occuring during an initial measuring or calibrating step when no secondary field is being generated may be cross correlated to form a cross correlation matrix of the changes in the third signals, or the cross correlation matrix of changes in the third signals may be calculated from estimates of what the third signals would be without the secondary field, and some or all of the adaption updates may use a matrix which is selected at least partly with reference to the said cross correlation matrix of the changes in the third signals.
[0020] The first signals and the noise (as hereinafter defined in equation 5) may be cross correlated to form a cross correlation matrix between the first signals and the noise, and some or all of the adaption updates may use a matrix which is selected at least partly with reference to the said cross correlation matrix between the first signals and the noise.
[0021] Where the first signals contain components attributable to the secondary vibration the latter is preferably subtracted from the outputs of the input sensors so that the first signals available for use by the controller do not contain any substantive components attributable to the secondary vibration.
[0022] The cross correlation matrix of the first signals may be stored as required in the controller.
[0023] The cross correlation matrix between the first and third signals may be stored in the controller.
[0024] The cross correlation matrix of the first signals (or the first and third signals) may be formed at least in part during an initial measuring or calibrating step or may be formed during the vibration reduction mode of operation of the controller or partly during an initial step and partly during a vibration reduction mode of operation of the controller.
[0025] Where the primary vibration field is produced by two or more sources each of which has a repetitive or periodic or quasi-periodic characteristic or any combination thereof and each input sensor is linked to a separate source and produces a first signal indicative of the repetitive or periodic or quasiperiodic activity of that source, the waveform generator may include a sampled-data system for each first signal, each of which systems is supplied with a control signal derived from one of the said first signals.
[0026] Where there are two or more sources and therefore two or more sampled-data systems and each sampled-data system has to be synchronized, the synchronization may be achieved using some or all of the control signals derived from the said first signals.
[0027] Where there are two or more sources and therefore two or more sampled-data systems each sampled-data system may comprise a sampled-data filter (eg a digital filter) the input of which is supplied with one of the first signals, and the sampled-data filters may be synchronized from a single synchronizing signal.
[0028] In the present invention each output wave generator may be a device which produces a signal waveform which is responsive to two or more input signals. Each of these input signals could be
(i) a signal which is time related to one of the vibration sources or to the unwanted (primary) field such as in UK patent 1,577,322 (from a tachometer for example), or
(ii) a signal which is time and amplitude related to the primary vibration.
(iii) a signal representative of the time or phase difference between the primary vibration or one of the vibration sources and some reference signal. This phase difference could, for example, be in the form of an angle difference for rotating machines or a timing difference.
[0029] The output wave generator can be a sampled-data device and can operate
(i) as a fixed (uniform) time-base filter.
(ii) on the time-base of a reference signal, which could be one of the input signals, so that a specified number of output points are generated in each vibration cycle. This can be thought of as a synchronous sampled-data filter.
(iii) on multiple time-bases, each time-base corresponding to a reference signal which could be one of the input signals. This would be thought of as multiple synchronous sampled-data filters whose output is combined to produce the waveform generator output.
[0031] The invention also lies in the method by which the output wave generators are adjusted or adapted in response to the input (first) signals and the signals from the residual sensors (third signals), so that their combined effect is to tend to cancel the unwanted vibration.
[0032] In one particular embodiment of the invention in which the output wave generators are filters, the unwanted vibration is generated by two vibration sources and the two input signals are derived directly from the sources, one from each. The inputs to the controller at time t are u1(t) and u2(t) and the impulse responses of the corresponding filters for the n-th actuator are X1(n,t) and X2(n,t) . The combined output (second) signal from the output waveform generator to the n-th actuator is
where * denotes convolution. In matrix notation we can write
etc., so that
[0033] The third signal at the m-th sensor when no control is applied is
where the first two terms on the right hand side are the contributions from the two vibration sources and n is the noise not associated with the vibration sources.
[0035] The residual signal at the M microphones is
where A(t) is the matrix of responses describing the way in which impulses from a controller output (second signals) affect the (third) signals from the residual sensors.
[0036] In the case where y1 and y2 can be identified separately the first filter output X1 can be used to cancel y1 since it is assumed to be well correlated with u1, and the second used for y2. The signal processing approach used in Eatwell and Ross sought to separate the components in the residual signals. This cannot be done accurately unless the signals are sufficiently noise-free or the constituent components remain constant for a long time. However, the current invention recognises that when separation is difficult, as in the case of synchrophased propellers, it is also unnecessary since the aim of an active control system is only to reduce the unwanted vibration.
[0037] The primary vibration can be thought of as a sum of independent (uncorrelated) components. These correspond to the contributions from the individual sources only when the input signals themselves are uncorrelated. The method is best explained in terms of these components.
[0038] A measure of the degree of correlation is given by the off- diagonal elements of the cross-correlation matrix of the first signals which is defined by
[0039] The angle brackets denote expectations which can be approximated by short term time averages. This definition is for two input (first) signals but the extension of this definition to more than two first signals is obvious. This can be transformed to the frequency domain, in which case it could be called the cross spectrum matrix, however, the use of the term cross correlation matrix should be taken to include the frequency domain equivalents. In the particular case when the input signals do not contain any amplitude information they can be normalised so that the diagonal elements of the matrix are unity, giving the complex matrix
where B(f) is the Fourier transform of <u1(t)u2(t+T)>, f is the frequency and the superposed * denotes complex conjugation.
[0040] In the frequency domain, when u1 and u2 are suitably normalised,
where t is the time between the start of a cycle of one vibration source and the start of a cycle of the other source. When the sampling is synchronised to one source
where f0 is the fundamental frequency, n is the harmonic number and Θ = 2πf0t is phase angle between the sources.
[0042] R is the modulus of B(f). The eigenvectors are
and
where argB is the argument of B and exp(.) is the exponential function.
[0043] A common way of measuring the performance of a control system is to calculate the mean square error at the residual sensors. This is denoted by
[0044] This is most useful when Y and X are only changing very slowly. We look at this case first in order to illustrate the importance of the cross-correlation matrix.
[0046] When the two vibration sources are well correlated R is close to unity and the first eigenvalue is much larger than the second. Hence, if Yv1 and Yv2 are of similar size we see that the first term on the right hand side gives a much larger contribution to the error E than does the second. This indicates that it may not be important to obtain a good estimate of this second component.
[0050] The calculation assumes that both A and u are known. In practice they cannot be known exactly. The effect of these inaccuracies are largest when the matrix C is poorly conditioned, that is when d2 is small. The error is then increased by a factor which scales on the noise level and on d2/h2, where h2 is the estimate of d2 used in the calculation of C-1. In addition the solution for X, even if it is accurate in the mean, is highly sensitive to the measurement noise.
[0051] This can be demonstrated by looking at the effect of errors in the eigenvalues of C. If h1 and h2 are the estimates of the eigenvalues we can write the estimate of C-1 as (I+c)C-1 where
and I is the identity.
[0053] The resulting mean square error, when A is known exactly and can be inverted, can be shown to be increased by an absolute amount
[0054] The error relative to the primary vibration is therefore increased by an amount depending on c and on the coherence between u and y. One factor affecting this coherence is the signal to noise ratio, s=<y*y>/<n*n>.
[0056] where g(d2) is a function which tends to increase d2 when it is small and leave it unchanged if it is large enough. The scaling of this function can be determined by the signal to noise ratio, s, or by any other measure of the noise or the coherence. One such measure which can be measured 'on-line' is
[0057] In most applications the primary vibration field is changing, this means that an adaptive control scheme must be used.
[0058] The adaptive scheme takes the form
where µ is a convergence parameter and R and Q are matrices to be chosen, and <ejuj*> is the cross correlation matrix of the first and third signals. The expectation denotes a combination of measurements such as an average or exponentially weighted average and includes the case where a single measurement is used. Typical expressions for R when there is a single vibration source are
where Iδ is the identity metrice and is a small positive number included to improve the conditioning of the matrix inversion. These expressions can be used for the multiple source case described here.
[0060] Another aspect of this invention is the choice of the functions f and g and the convergence parameter µ.
[0061] We shall do this by examining the performance of the algorithm. This can be done by looking at the change in the residual signal after one iteration of the update scheme. The error after the j-th iteration is
where
and
[0062] The term <ujuj*>Q can be written as
<(yj+1-yj) (yj+1-yj)*> is the cross correlation matrix of the changes in the third signals which would occur if the secondary field were not produced.
<(uj+1-uj)(uj+1-uj)*> is the cross correlation matrix of the changes in the first signals. <njuj*> is the cross correlation between the noise and the first signals. Equation (29) shows that there are four contributions to the new residual vector. The first term represents the change in the primary noise field, this can only be reduced by increasing the update rate. The second represents the error that would occur in a noise-free situation where the vibration sources were not changing. This term can be reduced by choosing µ to be unity, choosing R such that AR is close to the identity matrix, and by choosing Q to be close to C-1. The terms involving nj is additional noise introduced by the adaption algorithm. This term can be reduced by making µ, R or Q small (which is in conflict with reducing the second term) or by combining more measurements (which is in conflict with reducing the first term). The last term is proportional to the change in the input vector u this can be reduced by increasing the update rate. It is also proportional to Xj+1 which is affected by choice of µ and Q. In particular, when the function g is large, Xj+1 as given in equation 31 contains a large noise term.
[0063] The functions f and g may be chosen so as to minimise the one step ahead residual and so they depend upon the noise levels and the rate of change of the input vector u. The choice of µ may then be made with reference to f and g. We shall now give some examples.
[0064] One choice for Q uses f(d1) = g(d1,d2) = 1, which gives Q = I, the identity. Upon substituting equation 30 into equation 29 it is clear that for convergence of the algorithm
where norm(.) denotes the matrix norm. Hence the update scales on the largest eigenvalue of the cross-correlation matrix C.
[0065] Another choice is f(d1) = 1/d1 and g(d1,d2) is some function which tends to a fixed value when d2 is very small and tends to 1/d2 when d2 is sufficiently large. For example g(d1,d2) = 1/sqrt(d1d2) which ensures that the amplification of the noise is not too large. Q is then close to the inverse of the cross-correlation matrix C. For this case the algorithm converges provided
[0066] The foregoing analysis shows that the choice of functions f(.) and g(.) which will minimize the one-step ahead residual noise will depend upon the dynamics of the vibration sources and upon the noise levels. Hence the choice of the functions f(.) and g(.) may be made, for a particular application, with reference to the dynamics of the vibration sources and/or the noise levels in such a way as to reduce the expected value of the one-step ahead residual noise. One way this choice may be made is calculate or estimate the terms of equation 29 and select the functions which minimize the left hand side.
[0067] The invention may be applied to control the propeller noise in an aircraft with two propellers. This example is now described with reference to the accompanying drawing, in which Figure 1 shows one type of output wavefrom generator. Each output waveform generator (for simplicity only one is shown) receives a tachometer pulse train, 1, from one of the propellers and generates the anti-sound (second) signal, 2, for each loudspeaker in synchronization with it (again only one loudspeaker is shown for reasons of simplicity). The phase and amplitude of the loudspeaker signals are governed by output weighting coefficients, 3, which are adjusted by the adaptive algorithm.
[0068] The values of aj and bj, are the cosine and sine output weighting coefficients of the anti-sound signal for propeller 1, for each loudspeaker (at each harmonic j), and the values of a'j and b'j, are the coefficients for propeller 2. These output weighting coefficients are adjusted by the adaptive algorithm once per adaptive update. Regularly the phase signal, 4 , or a timing signal from which the phase is derived, is re-measured and used to combine the values of aj, a'j, bj, and b'j according to the equation:
(the subscript j has been dropped for clarity)
where:
- c
- is the combined coefficient for the cosine generator,
- d
- is the combined coefficient for the sine generator,
- Cp
- is the cosine of the phase angle (of propeller 2 relative to propeller 1), and
- Sp
- is the sine of the phase angle.
[0069] Each time a pulse is received from the tachometer pulse train the output to each loudspeaker is calculated according to the equation:
where WCj(i) is a stored cosine wave of harmonic number j, and WSj(i) is a stored sine wave of harmonic number j. This represents the sum of the cosine and sine generator outputs weighted by the coefficients cj and dj and summed for each harmonic j. In figure 1, two harmonics are being controlled.
[0070] The adaption in the controller may be done with reference to the third signals from microphones in the cabin. These could be used to adjust the output weighting coefficients a and b (or a' and b'), which are subsequently used by the output waveform generators to create the anti-sound signals.
1. An active vibration control system comprising:
at least two input sensors which generate first signals related to the phase and/or the amplitude of a primary vibration field or the sources which generate the primary vibration field,
a plurality of actuators driven by second signals which produce a secondary vibration field,
a plurality of monitoring sensors responsive to the combination of the said primary and secondary vibration fields and which produce third signals,
a controller including one output waveform generator for each second signal wherein each output waveform generator is responsive to the said first signals and generates one of the said second signals so that the combined effect of the second signals is that the vibration in a region, which is excited by the said primary and secondary vibration fields, tends to be reduced, wherein the controller adapts the output waveform generators so that the vibration in the region is maintained at a reduced level,
characterised in that said adaption of the output waveform generators takes account of the cross correlation matrix of the first signals and/or the cross correlation matrix between the first and third signals.2. A system as claimed in claim 1, wherein the adaption of the output waveform generators
by means of a matrix uses information from the first and third signals.
3. A system as claimed in claim 1 or claim 2, wherein the adaption of the output waveform
generators is scaled by the reciprocal of the largest eigenvalue of the cross correlation
matrix of the first signals.
4. A system as claimed in any of claims 1 to 3, wherein the adaption of the output waveform
generators uses a modified form of the inverse of the cross correlation matrix of
the first signals.
5. A system as claimed in any of claims 1 to 4, wherein the adaption of the output waveform
generators uses a matrix derived from the eigenvectors and/or the eigenvalues of the
cross correlation matrix of the first signals.
6. A system as claimed in any of claims 1 to 5, wherein one of the matrices used in the
adaption of the-output waveform generators is chosen to minimise the one-step-ahead
residual vibration in the region.
7. A system as claimed in any of claims 1 to 6, wherein one of the matrices used in the
adaption of the output waveform generators is chosen at least partly with reference
to the estimate of the cross correlation matrix of the changes in the first signals.
8. A system as claimed in any of claims 1 to 7, wherein one of the matrices used in the
adaption of the output waveform generators is chosen at least partly with reference
to the estimate of the cross correlation matrix of the changes in the third signals
which would occur without the secondary vibration.
9. A system as claimed in any of claims 1 to 8, wherein the cross correlation matrix
of the first signals is stored in the controller.
10. A system as claimed in any of claims 1 to 9, wherein the cross correlation matrix
between the first and third signals is stored in the controller.
11. A system as claimed in any of claims 1 to 10, wherein the cross correlation matrix
of the first signals is estimated during operation of the controller.
12. A system as claimed in any of claims 1 to 11, wherein the cross correlation matrix
between the first and third signals is estimated during operation of the controller.
13. A system as claimed in any of the preceding claims wherein the response of the input
sensors to the secondary vibration is subtracted from their output so that the first
signals are substantially insensitive to the secondary vibration.
14. A system as claimed in any of the preceding claims wherein part of at least one of
the output waveform generators is a filter which has a time-base synchronised to the
rotation rate or timing of one of the vibration sources.
15. A system as claimed in claim 14, wherein part of at least one of the output waveform
generators receives an additional signal related to the relative phase or timing of
another vibration source.
16. A system as claimed in any of the preceding claims wherein part of at least one of
the output waveform generators is a filter which operates on a uniform time-base and
which receives a signal related to the phase or timing of one vibration source.
1. Aktives Vibrationssteuersystem mit
mindestens zwei Eingangssensoren, die erste Signale erzeugen, welche auf die Phasenlage und/oder die Amplitude eines primären Vibrationsfeldes oder die Quellen, die das primäre Vibrationsfeld erzeugen, bezogen ist,
eine Mehrzahl von Betätigern, die durch zweite Signale angetrieben werden, welche ein sekundäres Vibrationsfeld erzeugen,
eine Mehrzahl von Überwachungssensoren, die auf die Kombination der primären und sekundären Vibrationsfelder ansprechen und die dritte Signale erzeugen,
eine Steuervorrichtung mit einem Ausgangskurvenformgenerator für jedes zweite Signal, wobei jeder Ausgangskurvenformgenerator auf die ersten Signale anspricht und eines der zweiten Signale erzeugt, so daß der kombinierte Effekt der zweiten Signale darin besteht, daß die Vibration in einem Bereich, der durch die primären und sekundären Vibrationsfelder erregt wird, zur Reduzierung tendiert, und wobei die Steuervorrichtung die Ausgangskurvenformgeneratoren so adaptiert, daß die Vibrationen in dem Bereich auf einem reduzierten Pegel gehalten werden,
dadurch gekennzeichnet, daß die Adaption der Ausgangskurvenformgeneratoren die Querbeziehungsmatrix der ersten Signale und/oder die Kreuzkorrelationsmatrix zwischen den ersten und dritten Signalen berücksichtigt.2. System nach Anspruch 1, bei dem die Adaption der Ausgangskurvenformgeneratoren mit
Hilfe einer Matrix Informationen aus den ersten und dritten Signalen benutzt.
3. System nach Anspruch 1 oder 2, bei dem die Adaption der Ausgangskurvenformgeneratoren
durch den reziproken Wert des größten Eigenwertes der Querkorrelationsmatrix der ersten
Signale maßstäblich verändert wird.
4. System nach einem der Ansprüche 1 - 3, bei dem die Anpassung der Ausgangskurvenformgeneratoren
eine modifizierte Form des inversen Wertes der Querkorrelationsmatrix der ersten Signale
verwendet.
5. System nach einem der Ansprüche 1 - 4, bei dem die Anpassung der Ausgangskurvenformgeneratoren
eine Matrix verwendet, die von den Eigenvektoren und/oder den Eigenwerten der Querkorrelationsmatrix
der ersten Signale abgeleitet wird.
6. System nach einem der Ansprüche 1 - 5, bei dem eine der Matrizen, die bei der Anpassung
der Ausgangskurvenformgeneratoren verwendet wird, so gewählt ist, daß die um eine
Stufe vorausgehende Restvibration im Bereich ein Minimum wird.
7. System nach einem der Ansprüche 1 - 6, bei dem eine der Matrizen, die bei der Anpassung
der Ausgangskurvenformgeneratoren verwendet wird, mindestens teilweise in bezug auf
den Schätzwert der Querkorrelationsmatrix der Änderungen in den ersten Signalen gewählt
wird.
8. System nach einem der Ansprüche 1 - 7, bei dem eine der Matrizen, die bei der Anpassung
der Ausgangskurvenformgeneratoren verwendet wird, mindestens teilweise in bezug auf
den Schätzwert der Querkorrelationsmatrix der Änderungen in den dritten Signalen gewählt
wird, die ohne die sekundären Vibrationen auftreten würden.
9. System nach einem der Ansprüche 1 - 8, bei dem die Querkorrelationsmatrix der ersten
Signale in der Steuervorrichtung gespeichert wird.
10. System nach einem der Ansprüche 1 - 9, bei dem die Querkorrelationsmatrix zwischen
den ersten und dritten Signalen in der Steuervorrichtung gespeichert wird.
11. System nach einem der Ansprüche 1 - 10, bei dem die Querkorrelationsmatrix der ersten
Signale während des Betriebes der Steuervorrichtung geschätzt wird.
12. System nach einem der Ansprüche 1 - 11, bei dem die Querkorrelationsmatrix zwischen
den ersten und dritten Signalen während des Betriebes des Steuergerätes geschätzt
wird.
13. System nach einem der vorausgehenden Ansprüche, bei dem das Ansprechen der Eingangssensoren
auf die sekundären Vibrationen von ihrem Ausgang subtrahiert wird, so daß die ersten
Signale im wesentlichen unempfindlich gegenüber den sekundären Vibrationen sind.
14. System nach einem der vorausgehenden Ansprüche, bei dem ein Teil mindestens eines
der Ausgangskurvenformgeneratoren ein Filter ist, der eine mit der Drehgeschwindigkeit
oder der Zeitsteuerung einer der Vibrationsquellen synchronisierte Zeitbasis hat.
15. System nach Anspruch 14, bei dem ein Teil mindestens eines der Ausgangskurvenformgeneratoren
ein zusätzliches Signal aufnimmt, das auf die relative Phasenlage oder die Zeitsteuerung
einer anderen Vibrationsquelle bezogen ist.
16. System nach einem der vorausgehenden Ansprüche, bei dem ein Teil mindestens eines
der Ausgangskurvenformgeneratoren ein Filter ist, das auf einer gleichförmigen Zeitbasis
arbeitet und das ein Signal aufnimmt, das auf die Phasenlage oder die Zeitsteuerung
einer Vibrationsquelle bezogen ist.
1. Système de commande active de vibrations comportant :
au moins deux capteurs d'entrée qui produisent des premiers signaux liés à la phase et/ou l'amplitude d'un champ primaire de vibrations ou aux sources qui produisent le champ primaire de vibrations,
une pluralité d'actionneurs entraînés par des deuxièmes signaux qui produisent un champ secondaire de vibrations,
une pluralité de capteurs de contrôle sensibles à la combinaison constituée desdits champs primaire et secondaire de vibrations et qui produisent des troisièmes signaux,
une commande comportant un générateur de forme d'onde de sortie pour chaque deuxième signal, chaque générateur de forme d'onde de sortie étant sensible auxdits premiers signaux et produisant l'un desdits deuxièmes signaux de sorte que le résultat combiné des deuxièmes signaux en est que les vibrations situées dans une zone, qui est excitée par lesdits champs primaire et secondaire de vibrations, tendent à être réduites, la commande adaptant les générateurs de forme d'onde de sortie de sorte que les vibrations dans la zone soient maintenues à un niveau réduit,
caractérisé en ce que ladite adaptation des générateurs de forme d'onde de sortie prend en compte la matrice d'intercorrélation des premiers signaux et/ou la matrice d'intercorrélation entre les premiers et les troisièmes signaux.2. Système selon la revendication 1, dans lequel l'adaptation des générateurs de forme
d'onde de sortie par l'intermédiaire d'une matrice utilise des informations provenant
des premiers et des troisièmes signaux.
3. Système selon la revendication 1 ou 2, dans lequel l'adaptation des générateurs de
forme d'onde de sortie est proportionnée par la réciproque de la plus grande valeur
propre de la matrice d'intercorrélation des premiers signaux.
4. Système selon l'une quelconque des revendications 1 à 3, dans lequel l'adaptation
des générateurs de forme d'onde de sortie utilise une forme modifiée de l'inverse
de la matrice d'intercorrélation des premiers signaux.
5. Système selon l'une quelconque des revendications 1 à 4, dans lequel l'adaptation
des générateurs de forme d'onde de sortie utilise une matrice dérivée des vecteurs
propres et/ou des valeurs propres de la matrice d'intercorrélation des premiers signaux.
6. Système selon l'une quelconque des revendications 1 à 5, dans lequel l'une des matrices
utilisées lors de l'adaptation des générateurs de forme d'onde de sortie est choisie
pour minimiser les vibrations résiduelles anticipées d'un pas situées dans la zone.
7. Système selon l'une quelconque des revendications 1 à 6, dans lequel l'une des matrices
utilisées lors de l'adaptation des générateurs de forme d'onde de sortie est choisie
au moins partiellement en référence à l'estimation de la matrice d'intercorrélation
des changements des premiers signaux.
8. Système selon l'une quelconque des revendications 1 à 7, dans lequel l'une des matrices
utilisées lors de l'adaptation des générateurs de forme d'onde de sortie est choisie
au moins partiellement en référence à l'estimation de la matrice d'intercorrélation
des changements des troisièmes signaux qui peuvent survenir sans les vibrations secondaires.
9. Système selon l'une quelconque des revendications 1 à 8, dans lequel la matrice d'intercorrélation
des premiers signaux est mémorisée dans la commande.
10. Système selon l'une quelconque des revendications 1 à 9, dans lequel la matrice d'intercorrélation
entre les premiers et troisièmes signaux est mémorisée dans la commande.
11. Système selon l'une quelconque des revendications 1 à 10, dans lequel la matrice d'intercorrélation
des premiers signaux est estimée pendant le fonctionnement de la commande.
12. Système selon l'une quelconque des revendications 1 à 11, dans lequel la matrice d'intercorrélation
entre les premiers et troisièmes signaux est estimée pendant le fonctionnement de
la commande.
13. Système selon l'une quelconque des revendications précédentes, dans lequel la réponse
des capteurs d'entrée aux vibrations secondaires est soustraite de leur sortie de
sorte que les premiers signaux sont pratiquement insensibles aux vibrations secondaires.
14. Système selon l'une quelconque des revendications précédentes, dans lequel une partie
d'au moins un des générateurs de forme d'onde de sortie est un filtre qui a une base
de temps synchronisée à la vitesse de rotation ou au minutage de l'une des sources
de vibrations.
15. Système selon la revendication 14, dans lequel une partie d'au moins un des générateurs
de forme d'onde de sortie reçoit un signal supplémentaire lié à la phase, ou au minutage,
d'une autre source de vibrations.
16. Système selon l'une quelconque des revendications précédentes, dans lequel une partie
d'au moins un des générateurs de forme d'onde de sortie est un filtre qui agit sur
une base de temps uniforme et qui reçoit un signal lié à la phase ou au minutage d'une
source de vibrations.