# US 5,553,153 A · Method and system for on-line system identification > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,553,153 A - Document ID: US5553153A - Status: Granted - Kind: A - Application number: 08/015,195 - Filed: 1993-02-10 - Granted: 1996-09-03 - Earliest claimed: 1993-02-10 - Assignees: Noise Cancellation Technologies, Inc. - Inventors: Graham P. Eatwell - Web page: https://patentgrep.com/patent/US5553153A ## CPC - G05B 17/02: electric - G10K 11/17813: {characterised by the analysis of the acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms} - G10K 11/17854: {the filter being an adaptive filter} - G10K 11/17855: {for improving speed or power requirements} - G10K 11/17879: {using both a reference signal and an error signal} - H03H 21/0012: {Digital adaptive filters} - G10K 2210/3018: Correlators, e.g. convolvers or coherence calculators - G10K 2210/30232: Transfer functions, e.g. impulse response - G10K 2210/3025: Determination of spectrum characteristics, e.g. FFT - G10K 2210/3033: Information contained in memory, e.g. stored signals or transfer functions - G10K 2210/30351: Identification of the environment for applying appropriate model characteristics - G10K 2210/3045: Multiple acoustic inputs, single acoustic output - G10K 2210/3057: Variation of parameters to test for optimisation - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) - G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract This invention relates to an improved method of on-line system identification for use with active control systems which requires less computation and reduces the problem of coefficient jitter in the filters of the active control system by using a fixed test signal which is designed to have a particular power spectrum. ## Claims ### Claim 1 An active noise or vibration control system with on-line system identification for identifying the response of a physical system, said control system comprising control means producing control signals, said control means including control adaption means responsive to residual signals, test signal generating means for generating test signals, wherein the test signal generating means includes means for delaying or inverting a fixed test signal of length determined by the response time of the physical system, including actuator means and sensing means, said actuation means responsive to a combination of the control signals and the test signals and producing a canceling noise or vibration, one component of which counters or partially counters an unwanted first noise or vibration, said sensing means responsive to the combination of said canceling noise or vibration and said first noise or vibration and producing input signals, compensation filter means responsive to said test signals and producing compensation signals, said compensation filter means including a filter adaption means responsive to said test signals and said residual signals and configured to minimize the correlation between the residual signals and the test signals, signal subtraction means for subtracting said compensation signals from said input signals to produce said residual signals, characterized in that the compensation signals substantially cancel the components of the input signal due to the test signals. ### Claim 2 (depends on 1) An active noise or vibration control system as in claim 1 and including means for delaying the residual signals by the same amount as the test signals and inverting the residual signals whenever the test signals the inverted so as to produce delayed or inverted residual signals. ### Claim 3 (depends on 2) An active noise or vibration control system as in claim 2, said control system including accumulation means for accumulating said delayed or inverted residual signals so as to produce accumulated residual signals. ### Claim 4 (depends on 3) An active noise or vibration control system as in claim 3 wherein the compensation filter means is adapted in response to said accumulated residual signals and said fixed test signal. ### Claim 5 (depends on 4) An active noise or vibration control system as in claim 4 wherein the compensation filter means is adapted in response to the product of said accumulated residual signals and said fixed test signal. ### Claim 6 (depends on 1) An active noise or vibration control system as in claim 1 and including means for delaying the input signals by the same amount as the test signals and inverting the input signals whenever the test signals are inverted so as to produce delayed or inverted input signals. ### Claim 7 (depends on 6) An active noise or vibration control system as in claim 6, said control system including accumulation means for accumulating said delayed or inverted input signal so as to produce accumulated input signal. ### Claim 8 (depends on 7) An active noise or vibration control system as in claim 7 wherein predicted responses to said fixed test signal are produced by passing said test signals through said compensation filter means and wherein the compensation filter means is adapted in response to said accumulated input signals and the predicted responses. ### Claim 9 (depends on 8) An active noise or vibration control system as in claim 8 wherein the compensation filter means is adapted in response to a Fourier Transform of said accumulated input signals and a Fourier transform of said test signals. ### Claim 10 (depends on 8) An active noise or vibration control system as in claim 8 wherein the compensation filter means is adapted in response to said accumulated input signals, said fixed test signal and said predicted responses. ### Claim 11 (depends on 1) An active noise or vibration control system as in claim 1 wherein said fixed test signal, y(n) at time sample n, satisfies ##EQU16## wherein M is the length of said fixed test signal and L is a constant. ### Claim 12 (depends on 1) An active noise or vibration control system as in claim 1 wherein said fixed test signal, y(n) satisfies y(0)=L y(n)=0, n=1,2,3, . . . , M-1 where M is the length of said fixed test signal and L is a constant. ### Claim 13 (depends on 1) An active noise or vibration control system as in claim 1 wherein one compensation filter means is used to couple each actuator output with each sensor input. ### Claim 14 (depends on 1) An active noise or vibration control system as in claim 1 wherein said compensation filter means is a Finite Impulse Response filter. ### Claim 15 (depends on 1) An active noise or vibration control system as in claim 1 wherein said compensation filter means is an Infinite Impulse Response or recursive filter. ### Claim 16 (depends on 1) An active noise or Vibration control system as in claim 1 wherein said compensation filter means is a Lattice filter. ### Claim 17 (depends on 1) An active noise or vibration control system as in claim 1 wherein said compensation filter means is adapted less frequently than said control means. ### Claim 18 (depends on 1) An active noise or vibration control system as in claim 1 wherein the control adaption means and the compensation filter adaption means operate at a different rate to the control means and the adaption rate of said compensation filter means is determined by the processing power of said active noise control system.