MULTIPLE INTERACTING DVE ALGORITHM

Abstract: A digital virtual earth (DVE) cancellation system which receives a phenomena input signal via multiple sensors (1, 2, 3) representing residual phenomena to be canceled, and has adaptive filters (12, 24, 25) for each of the multiple sensor/actuator pairs, (1, 4, 2, 5, 3, 6) which generate the appropriate cancellation signal (19, 20, 21) for the associated actuator (4, 5, 6). The multiple interacting DVE (MIDVE) algorithm estimates the noise at each sensor (1, 2, 3) by subtracting out the combined effects of each actuator signal (19, 20, 21) from the residual signal (16, 17, 18) at that sensor (1, 2, 3). This estimated noise signal is used to control the adaptive filters (12, 24, 25) associated with the subject actuator (4, 5, 6). These filters (12, 24, 25) receive the estimated noise as input. They then produce the cancellation signals by filtering the estimated noise with the filter weights. These weights are adapted using the residual signal (16, 17, 18) and the estimated noise convolved with the system impulse responses.

Description: MULTIPLE INTERACTING DVE ALGORITHM FIELD OF THE INVENTION The present invention relates to active cancellation systems for repetitive or non- repetitive phenomena, and, more specifically, to the extension of the digital virtual earth technology to applications involving multiple interacting sensors and actuators. BACKGROUND OF THE INVENTION In U.S. Patent Number 5,105,377 by the same inventor, hereby incorporated by reference herein, there is described an active cancellation system for repetitive or non- repetitive phenomena which estimates the noise signal by subtracting the predicted effects of the cancellation signal from the residual sensor signal. In this single input, single output system, an LMS filtered-x algorithm is employed to adapt the cancellation filter coefficients. The adaptive filter produces the cancellation signal by filtering the estimated noise with filter weights that are adapted using the residual signal and the estimated noise convolved with the system impulse response. The single channel version of the DVE algorithm is described by the equations: x k = e k " ∑ Q - yk - 1 y = ∑ A m,k , χ k - m m A m^ + ι = A m , k - α -e k - ∑ Cι.x k _ ! where: y k is the cancellation signal value at sample k, e k is the error signal value at sample k, C is the vector of coefficients of the impulse response from the controller output to the error sensor input, A is the vector of coefficients of the cancellation filter, x k is the value of the estimated noise signal at sample k and α is the LMS convergence rate coefficient This form of the algorithm is only applicable to systems consisting of one channel, i.e. a single sensor and a single actuator. In many situations, a multiple channel version of the algorithm is necessary to provide complete cancellation. Therefore, there exists a need for a digital virtual earth active cancellation system which is applicable to multiple input-output channels. SUMMARY OF THE INVENTION The multiple interacting DVE (MIDVE) algorithm computes an estimate of the noise at each sensor by subtracting out the combined effects of each actuator signal according to the following equations: x s,k = e s,k " ∑ ∑ C a,s,l • y a ,k - 1 a 1 where the subscripts a and s indicate the actuator and sensor. The remaining variables are as described above but extended to different sensors and actuators, (and pairs of sensors and actuators as with the impulse responses and cancellation coefficients). The cancellation signal for each actuator is computed by summing the partial cancellation signals based on the estimated noise signal at each sensor as follows: v a,k - _ ι Z., A s,a,m,k • x s,k • m The cancellation filter coefficients are updated using a multidimensional fϊltered-x algorithm as follows: A s,a,m,k + 1 = As,a,m,k " α • e s,k * _£_, ~-&, ~ ,\ ' x s,k - 1 This extension of the single input, single output DVE algorithm to nultichannel applications follows, in only the most general terms, the methodology described in an article entitled An Adaptive Algorithm for Active Cancellation of a Wideband Random Field by S.N. Arzamasov and A.A. Mal'tov. This paper was submitted April 11, 1984 tcr Gor'ku University, and published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 28, No. 8, pp. 1008-1016, in August 1985 (and translated to English by Plenum Publishing Corporation). However, the Arzamasov/Mal'tov approach requires 2 levels of input sensors (an "upstream" sensor and a "downstream" sensor) for each cancellation output transducer. The present invention eliminates the need for such a requirement. In a MIDVE system, only 1 sensor is needed for each output channel. This reduces not only cost over the prior art, but also reduces the computational burden on the system processor. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram showing the basic MIDVE system. Figure 2 is a block diagram detailing the impulse responses between the multiple interacting inputs and outputs. Figure 3A is a more detailed block diagram of an embodiment of one channel of the input section of the MIDVE system of Figure 1 constructed in accordance with the present invention used in the system of Figure 1. Figure 3B is an alternate embodiment of the input channel detailed in Figure 3A. Figure 4A is a more detailed block diagram of an embodiment of one channel of the output section of the MIDVE system of Figure 1 constructed in accordance with the present invention used in the system of Figure 1. Figure 4B is an alternate embodiment of the output channel detailed in Figure 4A. Figure 5 is a block diagram showing the partial operation of an embodiment of the processor constructed in accordance with the present invention used in the system of Figure 1. DETAILED DESCRIPTION Figure 1 is a block diagram which depicts the basic composition of a MIDVE system. For the remainder of the context of this discussion, only 3 channels of the MIDVE system will be diagrammed. The last, channel "n", should be understood to represent the n tn channel of an n-channel system. So, the system is made up of residual sensors 1, 2, and 3, actuators 4, 5, and 6, and a processor 7. The system functions as follows. Phenomena (e.g. noise and/or vibration) are received by the multiple residual sensors 1, 2 and 3. In response, these sensors emit their respective sensor signals. These sensor signals are affected by various system factors which have impulse responses E _ , E2, , and E n . The resulting residual signals r^, X2, and r n (16, 17, and 18) are received by the processor 7 which it uses to generate the cancellation signals y j , y2 . —- . and y n (19, 20, and 21). These cancellation signals are affected by various factors which have impulse responses S j , S2, , and S n . The resulting cancellation output phenomena from the actuators 4, 5, and 6 combines with the original phenomena, and the residual is detected by the residual sensors 1, 2, and 3. The signal values are determined by v a.k = 2__ -1 ~ . a, m, k " x s, k - m s m where y a k is the cancellation signal from actuator a at time k x s k - m -- tne va l ue of the estimated noise signal at sensor s at time k - m and A s a m k is the m* coefficient at time k of the cancellation filter associated with sensor s and actuator a. Figure 2 is a block diagram showing all of the paths of the impulse responses between the multiple inputs and outputs of the system. At each sensor, the output of each actuator has been affected by the impulse response between that sensor and the respective actuator. Figures 3A and 3B are more detailed block diagrams of the input section of the MIDVE system. The residual sensors 1, 2, and 3 detect the noise and/or vibration phenomena and in response emit sensor signals 8, 9, and 10. Each of these signals pass through an amplifier/gain stage 11, and are then conditioned by anti-aliasing circuitry 12. These conditioned signals are then sampled and converted to digital signals through the combination of the sample-and-hold circuitry 13 and the analog-to-digital converter (A/D), 14. Note that, although described pictorially as a separate entity, the sample-and -hold circuitry could be part of 14. In addition, note that the multiple input signals could be multiplexed through one set of input conditioning circuitry (Figure 3 A) or each could have its own set of dedicated input circuitry (Figure 3B). In Figure 3B, the additional circuitry required would consist of additional amplifier/gain control stages 22 and 23, additional anti-aliasing filters 24 and 25, additional sample-and-hold circuitry 26 and 27, and additional A/D's 28 and 29. The resulting digital input values, the residual signals τ_, T2, and r n (16, 17, and 18), are then available for tfse by the processor 7. The processor consumes the input data values and from them produces the appropriate cancellation output signal. Other embodiments of the input electronic circuitry could be used in place of that described above and shown in Figure 3 in order to provide the input data. Figures 4A and 4B are more detailed diagrams of the output section of the MIDVE system. The residual signals τ \ - 12- and r n (16, 17, and 18) from the input section are used by the processor, along with the system impulse response, to produce the appropriate cancellation signals y \ , y2, and y n (19, 20, and 21). The cancellation signals are converted to analog form by the digital-to-analog converter 31. These analog signals then pass through a reconstruction filter 32, are amplified by a gain stage 33, and are then converted to physical phenomena by actuator 34. The resulting cancellation phenomena mixes with the original noise/vibration phenomena and the residual is detected by residual sensors 1, 2, and 3 in the input section of the system. Note that the multiple output signals could be multiplexed through one set of output circuitry (Figure 4A) or each could have its own set of dedicated input circuitry (Figure 4B). In Figure 4B, the additional circuitry required would consist of additional D/A's 34 and 35, additional reconstruction filters 36 and 37, additional amplifier/gain stages 38 and 39, and additional actuators 40 and 41. In the MEDVE system, the system impulse response for any given output section includes the impulse response S of the respective output circuitry 31, 32, 33, 34, and 30 (if so configured), and the impulse responses E^ E 2 , and E n of the input circuitry 11,12, 13, 14, and 15 (if so configured) of each of the multiple input sections. Thus, each input channel of the system has an effect on the output of each channel. Figure 5 is a block diagram showing the partial operation of an embodiment of the processor 7 constructed in accordance with the present invention used in the system of Figure 1. The processor 7 receives the residual signals rj, r 2 , and r n (16, 17, and 18) from d e multiple sensors. The MIDVE algorithm estimates the noise at each sensor by subtracting out the combined effects of each actuator signal from the residual signal as follows: x s = e s,k " ∑ ∑ a,s,l • ya,k - 1 a I where the subscripts a and s denote the actuator and sensor, and the subscript k denotes the value at sample time k. The 1 subscript represents the estimated amount of time delay (the delay line) from the output to the input sensor. The estimates xi , x 2 , and x n (52, 53, and 54) of the noise at each sensor proceed from their respective summation points, through delay lines 55, 56, and 57, and each are input to adaptive filters 64, 65, and 66. The output of the adaptive filters, each having filter weights A m n , are summed, then inverted, and the resulting signal is output to the output circuitry. Thus, the processor computes the cancellation signal for each actuator as follows: y a ,k = Σ Δ-J A s, a, m, k * x s, k • m The output delay lines 55, 56, and 57 are also provided to a second set of filters 43, 44, and 45 that are a model of the impulse response between the respective sensor and actuator. The output from these filters proceed through another set of delay lines 58, 59, and 60, and are then used by adapters 61, 62, and 63. These adapters use the filtered outputs, along with the original residual signals r j , r2, and r n , to provide adaptation signals to the adaptive filters 64, 65, and 66. These adaptation signals are used to adjust d e adaptive filter weights A m n . The cancellation filter coefficients are updated using a multidimensional filtered-x algorithm as follows: As, a, m, k + 1 = A s, a, m, k " α , e s, k* __ C a> s, 1 • x s, k - 1 The diagram of Figure 5 only shows the operations that the processor performs in calculating the output for channel 1 of the MIDVE system, but would be similarly extended for all other output channels. The processor 7 depicted in Figure 5 could be implemented in any of Several forms including fixed program hardware, custom VLSI, or in one or more stored program microprocessors. Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only. In no way should it be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the following claims.

Claims: CLAIMS 1. A multiple input, multiple output active cancellation system which has only one input transducer for each cancellation output transducer comprising: means for detecting repetitive and/or non-repetitive noise and/or vibration phenomena and including multiple sensors producing appropriate residual signals, input circuitry means coupled to the multiple sensors and adapted to convert the residual signals into a digital form that is used by a processor of d e system, output circuitry means adapted to convert multiple digital output signals from the processor into analog form usable by the output means, an output means for producing d e output noise and/or vibration from the multiple analog output signals, said means consisting of multiple output actuators, processor means coupled to said input and said output circuitry means that receives the multiple residual input signals and produces the multiple output signals. 2. A system as in claim 1 wherein said input circuitry means includes sample-and- hold circuit means and an analog to digitafconverter. 3. A system as in claim 1 wherein input circuitry means comprises a multiplicity of dedicated input circuitry, one for each input signal. 4. A system as in claim 3 wherein each dedicated input circuitry includes amplifier/gain control stages, anti-aliasing filters, sample-and-hold circuitry and analog to digital converters. 5. A system as in claim 1 wherein said processor means included means to employ a multi-dimensional filtered-x algoridim to update d e cancellation filter coefficients to subtract out the combined effects of each of die actuator signals from the residual signals to provide an estimated input signal at each sensor. 6. A system as in claim 5 wherein said processor means further includes means to convolve said estimated input signals with cancellation filter coefficients to produce output signals. 7. A system as in claim 6 wherein said processor means further includes means to continually update the cancellation filter coefficients. 8. A multiple input, multiple output digital virtual earth active cancellation system comprising: means for detecting repetitive and/or non-repetitive noise and/or vibration phenomena and producing appropriate residual signals using multiple sensors, input circuitry means coupled to d e multiple sensors which convert the residual signals into a digital form that is used by a processor of the system, output circuitry means adapted to convert multiple digital output signals from a processor into analog form usable by the output means, an output means for producing the output noise and/or vibration from the multiple analog output signals, said means consisting of multiple actuators, processor means coupled to said input and said output circuitry that receives the multiple residual input signals and produces the multiple ouφut signals. 9. A system as in claim 8 wherein said input circuitry means includes amplifier/gain control stages, anti-aliasing filters, sample-and-hold circuitry and analog to digital converters. 10. A system as in claim 8 wherein said processor means includes means to update cancellation filter coefficients to provide estimated input signals at each sensor and to convolve said signals witii said coefficients to produce output signals. 11. A method for extending die single input, single ouφut DVE algorithm to systems with multiple sensors and actuators by employing a multi-dimensional filtered-x algoritiim to update die cancellation filter coefficients; said method consisting of: subtracting out the combined effects of each of said actuator signals from each of said residual signals to produce an estimated input signal at each sensor, convolving said estimated input signals with the appropriate cancellation filter coefficients to produce the ouφut signals for each of said multiple actuators, and continually updating said cancellation filter coefficients. 12. A method as in claim 11 wherein the step of convolving said estimated input signals involves passing said signals dirough filters that are a model of the impulse response between the respective sensor and actuator.

Inventors: ZIEGLER ELDON JR, ZIEGLER, ELDON, JR.
Applicants: NOISE CANCELLATION TECH, ZIEGLER ELDON JR, NOISE CANCELLATION TECHNOLOGIES, INC.
Application year: 1992
Main classification: G06F15
IPC codes: G06F17, G10K11, H03H21