Abstract: An adaptive control system implements a back-projection technique to limit adaptation of adaptive parameters in the system so that system actuators are not driven beyond desired physical limitations. When the optimal controller solution lies outside of a desired region in the parameter space, chosen in accordance with the physical limitations of the system, adaptation is back-projected onto or near a smooth convex surface defining the edge of the desired region. Adaptation is preferably normalized to improve adaptation convergence. Back-projection is preferably compensated in accordance with adaptation normalization to facilitate convergence. To lessen computational burdens, adaptation and/or back-projection is accomplished in accordance with a time-sharing technique in which orthogonal components are separately processed. The technique can be implemented in tonal control systems, and in systems capable of controlling non-periodic disturbances.

Abstract: An active acoustic attenuation system in which the region of desired acoustic control is remote from an error sensor. The invention uses an adjusted error signal from the remote error sensor to update an adaptive control filter. The adaptive control filter drives an output transducer which outputs a secondary input that destructively interferes with and cancels an acoustic disturbance. Adaptation of the adaptive control filter compensates for the error sensor being remote from the region of desired control by adjusting the error signal in accordance with an H filter representing a relationship between a disturbance signal measured by the error sensor and a disturbance signal as would be measured in the region of desired control. The invention includes feedforward and regenerative feedback embodiments, as well as SISO and MIMO embodiments.

Abstract: An adaptive control system and method for actively canceling tones in an active acoustic attenuation system has an adaptive parameter bank. Adaptation of the adaptive parameter bank can be constrained with respect to the null space of a C model of an auxiliary path (e.g. speaker-error). Alternatively, output from the adaptive parameter bank can be constrained with respect to the effective null space of the C model. The preferred system uses singular value decomposition, normalization, and demodulation to implement the methods of constraining output and adaptation. The invention can eliminate stability and tracking problems associated with over-parameterization.

Abstract: A system that facilitates the development and operation of active sound or vibration control systems, especially for those not skilled in computer programming. The system facilitates the development of developing active sound or vibration control systems implementing an adaptive control model. In particular, the system has a software collection containing control system software that implements an adaptive control model which can be programmed on an electronic controller to actively control sound or vibration. The system also has a user interface that prompts the user to enter information pertaining to the control system being developed so that the electronic controller can implement an adaptive control model in accordance with the information entered by the user.

Abstract: An active control system having an adaptive filter model in which the effect of transfer functions after the adaptive filter model output are eliminated from the adaption process. The adaptive control scheme inputs a reference signal to a copy of the adaptive filter model, and the copy of the adaptive filter model outputs a correction signal that drives an output transducer. The copy of the adaptive filter model does not receive an error input signal. Adaption occurs in the adaptive filter model. The model input to the adaptive filter model is a C-filtered reference signal. There are no transfer functions between the output of the adaptive filter model and the error input to the adaptive filter model. The error input to the adaptive filter model is a combination of an error signal from an error sensor, a C-filtered correction signal, and a model output signal from the adaptive filter model.

Abstract: An adaptive control system that can be used for active acoustic attenuation implements an LMS or an RLMS update using an error signal that is filtered through a delayed Hermitian transpose of a C model of an auxiliary path following an adaptive control filter. Adaptive on-line C modeling can be used effectively. The invention is useful in SISO and MIMO applications, and can reduce the number of filtering operations in systems using several reference signals. The invention does not require inverse C modeling.

Abstract: An act control system introduces a control signal put transducer (14) to combine with the system input signal (6) and yield a system output signal (8). An adaptive filter model (40) has an output (46) supplying a correction signal to the output transducer to introduce the control signal. The model has a first error input (44, 232, 248) driven by an error signal from an error transducer (16) to drive the correction signal toward a value matching the system input signal to modify and/or cancel same. The model has a second error input (202, 224, 240, 268, 280) selectively driven by a spectral leak signal (212) to drive the correction signal away from such matching value by driving the correction signal towards zero, to selectively constrain performance of the model in response to a given condition of a given parameter.

Abstract: An active acoustic system provides attenuation and spectral shaping of an acoustic wave. A phase lock loop (304) phase locks to the input acoustic wave (6) and generates (306) a desired signal or tone (308) in given phase relation therewith. An error signal (44) from an error transducer or microphone (16) is summed (302) with the desired signal (308) and the resultant sum is supplied to the error input (202) of an adaptive filter model (40) which outputs a correction signal (46) to an output transducer or speaker (14) to introduce the canceling and shaping acoustic wave. In other embodiments, various combinations sum the desired signal (308) with the error signal (44), the model output correction signal (46), and the model input signal (42). Speaker and error path compensation (146, 318, 320) and feedback compensation (340) is provided.

Abstract: An active acoustic attenuation system attenuates a correlated input acoustic wave and eliminates the need for an input transducer sensing such wave and also eliminates the need to sum a filtered modification of the model output correction signal with the error signal as an input to the model. The error signal is instead summed with the model input signal provided through a model copy, and the output resultant sum is supplied as the input to the model. A summer sums the error signal from the error transducer and the output of a copy of the adaptive filter model and supplies the resultant sum to the model input. Another copy of a model modeling the output transducer and the error path between the output transducer and the error transducer is connected in series between the model input and the input of the first noted model copy.

Abstract: An acoustic system (20) includes a model reference (22) having a selectably programmable response, and an active model (24) including in combination an acoustic path (26) and an adaptive filter (28) such that the combination of the acoustic path (26) and the adaptive filter (28) adaptively models the model reference (22) such that the combined response of the acoustic path (26) and the adaptive filter (28) provides an active model response matching the response of the model reference (22).

Abstract: A multi-channel active acoustic attenuation system for attenuating a correlated input acoustic wave has one or more output transducers introducing one or more respective canceling acoustic waves to attenuate the input acoustic wave and yield an attenuated output acoustic wave, one or more error transducers sensing the output acoustic wave and providing one or more error signals, and a plurality of adaptive filter channel models. Each channel model has a model input from a respective error transducer. One or more of the channel models also has a model input from at least one of the remaining channel models. Each channel model has an error input from one or more of the error transducers. Each channel model has a model output outputting a correction signal to a respective output transducer to introduce the respective canceling acoustic wave. The correction signal from one or more of the model outputs is also input to the model input of one or more of the remaining channel models.