CONTROL AND PROTECTION OF LOUDSPEAKERS

• US 20150304772A1
• Filed: 09/24/2013
• Published: 10/22/2015
• Est. Priority Date: 09/24/2012
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Actiwave AB (Cirrus Logic Incorporated)
• Inventors: Risberg, Pr Gunnars, Lindahl, Erik, Toth, Landy, Arvidsson, Marcus, Karlsson, Daniel
• Granted Patent: US 9,900,690 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04R 3/002 Damping circuit arrangements for transducers, e.g. motional feedback circuits
• CPC Class Codes: H04R 3/007 Protection circuits for transducers

Abstract

A nonlinear control system and a loudspeaker protection system. In particular, a nonlinear control system including a controller, an audio system, and a model is disclosed. The controller is configured to accept one or more input signals, and one or more estimated states produced by the model to produce one or more control signals. The audio system includes one or more transducers configured to accept the control signals to produce a rendered audio stream therefrom. An active loudspeaker with an integrated amplifier is disclosed. A loudspeaker protection system and a quality control system are disclosed. More particularly, a system for clamping the input to a loudspeaker dependent upon a bank of representative models is disclosed.

Claims

1. A loudspeaker protection system for producing a rendered audio stream from one or more input signals comprising:

an estimator comprising one or more state estimating models, each state estimating model configured to accept one or more of the input signals, and to generate one or more estimated states therefrom; and

a loudspeaker protection block configured to accept one or more of the input signals and/or delayed versions thereof, and the estimated states and/or signals generated therefrom, and to produce an output signal from a combination thereof.

2. The loudspeaker protection system in accordance with claim 1, further comprising a selector coupled to the estimator and the loudspeaker protection block and configured to analyze one or more of the estimated states and/or state estimating models, and to generate an estimating signal therefrom,

wherein the loudspeaker protection block is further configured to use the estimating signal in producing the output signal.

3. The loudspeaker protection system in accordance with claim 2, wherein the selector is further configured to select a worst case estimated state from the estimated states,

wherein the estimating signal is dependent upon the worst case estimated state.

4. The loudspeaker protection system in accordance with claim 2, further comprising a feedback block coupled to an associated loudspeaker and the selector, and configured to provide one or more feedback signals from the loudspeaker to the selector,

wherein the selector is further configured to use one or more of the feedback signals in generating the estimating signal.

5. The loudspeaker protection system in accordance with claim 2, wherein one or more of the state estimating models is altered based upon the estimating signal.

6. The loudspeaker protection system in accordance with claim 1, further comprising:

a feedback block coupled to an associated loudspeaker and/or driver configured to provide one or more feedback signals or signals generated therefrom to the system;

a model bank including a group of models each with associated characteristics; and

a selector coupled to the feedback block, the model bank, and the estimator, and-configured to accept one or more of the feedback signals or signals generated therefrom, calculate one or more measured characteristics from the feedback signals, compare one or more model characteristics to the measured characteristics to select a best fit model from the model bank, and load, enable, and/or select an associated best fit model for operation within the estimator.

7. The loudspeaker protection system in accordance with claim 6, wherein the measured characteristic is related to loudspeaker impedance and the estimated state is related to loudspeaker excursion.

8. The loudspeaker protection system in accordance with claim 1, further comprising:

a feedback block coupled to an associated loudspeaker and/or driver and configured to provide one or more feedback signals or signals generated therefrom to the system;

a model bank comprising a group of feedback estimating models each associated with a corresponding state estimating model and configured to calculate a value from one or more of the input signals; and

a selector coupled to the feedback block, the model bank, and the estimator, and configured to compare one or more of the values with the feedback signals to select a best fit feedback estimating model from the model bank,

wherein the selector is further configured to load, enable, and/or select a corresponding best fit state estimating model for operation within the estimator.

9. The loudspeaker protection system in accordance with claim 8, wherein the feedback signals are related to loudspeaker current and/or voltage, and the estimated state is related to loudspeaker excursion.

10. The loudspeaker protection system in accordance with claim 1, wherein one or more of the state estimating models are a feed forward transfer function.

11. The loudspeaker protection system in accordance with claim 1, wherein the protection block comprises a compressor, limiter, and/or clipper configured to accept the input signals, and

wherein the compressor, limiter, and/or clipper includes one or more properties configured by the estimated states and/or estimating signal.

12. The loudspeaker protection system in accordance with claim 8, wherein the protection block, the model bank, and/or the selector are configured to accept a power constraint from an external power manager.

13. The loudspeaker protection system in accordance with claim 8, wherein the estimator, the model bank, and/or the selector are configured to generate a power prediction.

14. The loudspeaker protection system in accordance with claim 13, wherein the power prediction is used in generation of the output signal.

15. The loudspeaker protection system in accordance with claim 13, wherein the protection block is configured to compare the power prediction with the power constraint in generation of the output signal.

16. The loudspeaker protection system in accordance with claim 1, wherein the protection block, compressor, limiter, and/or clipper are configured to accept a kinetic feedback signal representative of a movement of the loudspeaker within an environment, and to generate the output signal based upon the kinetic feedback signal.

17. The loudspeaker protection system in accordance with claim 16, wherein a kinetic feedback signal is selected from the group consisting of a linear acceleration, a rotational motion, a pressure change, a free-fall condition, an impact, and combinations thereof.

18. The loudspeaker protection system in accordance with claim 1, wherein the loudspeaker protection system is configured to upload one or more of the estimated states, state estimating models, and/or estimating signals to a data center.

19. The loudspeaker protection system in accordance with claim 1, wherein one or more of the models is of a type selected from a minimum phase model, a linear phase model, and a set of one or more biquad filters.

20. The loudspeaker protection system in accordance with claim 1, wherein the loudspeaker protection block is configured to superimpose a test signal onto the output signal.

21. The loudspeaker protection system in accordance with claim 6, wherein the selector is further configured to extract a test feedback signal related to the test signal from the feedback signal.

22. The loudspeaker protection system in accordance with claim 21, wherein the selector is further configured to generate a model based upon the test signal and the test feedback signal.

23. The loudspeaker protection system in accordance with claim 1, wherein the loudspeaker protection system is configured to periodically update one or more of the state estimating models.

24. The loudspeaker protection system in accordance with claim 23, wherein the loudspeaker protection system is further configured to download an updated model from a data center.

25. The loudspeaker protection system in accordance with claim 8, wherein one or more of the selector, the model bank, and the estimator are implemented in an operating system compatible background service.

26-27. -27. (canceled)

28. A method for protecting a loudspeaker, the method comprising:

receiving an input signal including an audio stream;

estimating one or more loudspeaker states from the audio stream;

determining which estimated loudspeaker states best represent an actual loudspeaker state; and

modifying the audio stream based upon the determined best estimated loudspeaker state.

29. The method for protecting a loudspeaker in accordance with claim 28, wherein the modifying step includes limiting the audio stream based upon a value of the best estimated loudspeaker state.

30. The method for protecting a loudspeaker in accordance with claim 28, further comprising:

measuring a feedback signal from the loudspeaker; and

basing the determination at least in part upon the feedback signal.

31. The method for protecting a loudspeaker in accordance with claim 28, wherein the estimating step includes calculating one or more of the state estimates with a feed forward model.

32. The method for protecting a loudspeaker in accordance with claim 28, further comprising:

calculating state estimates and output estimates from corresponding model pairs;

comparing the output estimates from each model pair with a feedback signal from the loudspeaker to select the best model pair; and

selecting the best estimated loudspeaker state from the best model pair.

33. The method for protecting a loudspeaker in accordance with claim 28, further comprising:

calculating a power estimate from the input signal and/or a feedback signal; and

using the power estimate in the modifying step.

34. The method for protecting a loudspeaker in accordance with claim 28, further comprising:

receiving a power constraint; and

limiting an output signal based upon the power constraint.

35. The method for protecting a loudspeaker in accordance with claim 28, further comprising;

sending data corresponding to one or more state estimates to a data center; and

receiving one or more power constraints from the data center.

36. The method for protecting a loudspeaker in accordance with claim 28, further comprising reverting to a safe operating mode if a best estimated loudspeaker state cannot be determined.

37. The method for protecting a loudspeaker in accordance with claim 36, wherein the safe operating mode comprises:

summing each of the estimates to form a worst case estimate; and

modifying the audio stream based upon the worst case estimate.

38. An active loudspeaker comprising:

a movable membrane configured for production of an audible sound wave;

an enclosure with one or more walls coupled to the movable membrane so as to form a cavity within the enclosure;

one or more sensors coupled to the movable membrane configured to measure one or more states associated with a movement of the membrane to produce a sensory feedback signal; and

a microcircuit electrically coupled to the sensor and the movable membrane, coupled to and/or embedded within one of the walls of the enclosure, and configured to receive the sensory feedback signal and to drive the movement of the membrane.

39. The active loudspeaker in accordance with claim 38, wherein one or more of the sensors is selected from the group consisting of a capacitive sensor, an optical sensor, a thermopile, a pressure sensor, an infrared sensor, and an inductive sensor.

40. The active loudspeaker in accordance with claim 38, wherein one or more sensors is an optical sensor comprising an emitter and a detector, and

wherein the emitter and detector are optically coupled to the membrane.

41. The active loudspeaker in accordance with claim 40, further comprising a plurality of optical sensors, each optical sensor optically coupled with the membrane and configured to produce an optical feedback signal,

wherein the microcircuit is further configured to compare a plurality of the optical feedback signals to determine presence of a rocking vibration mode of the membrane.

42. The active loudspeaker in accordance with claim 41, wherein the microcircuit is further configured to reduce a movement of the membrane upon detection of a presence of a rocking mode.

43. The active loudspeaker in accordance with claim 38, wherein one or more sensors and the microcircuit are packaged into a single system on a chip.

44. The active loudspeaker in accordance with claim 38, further comprising a connector coupled to the microcircuit and configured to convey signals between the microcircuit and an external system,

wherein the microcircuit is further configured to communicate power, an audio stream, and/or configuration data via the connector with the external system.

45. The active loudspeaker in accordance with claim 44, wherein the connector comprises two terminals, through which the power, audio stream, and configuration data are communicated.

46. The active loudspeaker in accordance with claim 38, comprising a speaker protection system including:

an estimator comprising one or more state estimating models, each state estimating model configured to accept one or more of the input signals, and to generate one or more estimated states therefrom; and

a loudspeaker protection block configured to accept one or more of the input signals and/or delayed versions thereof, and the estimated states and/or signals generated therefrom, and to produce an output signal from a combination thereof.

47. A nonlinear control system for producing a rendered audio stream from one or more input signals, the nonlinear control system comprising:

a controller configured to accept one or more of the input signals and one or more estimated states, and to generate one or more control signals therefrom;

a model configured to accept one or more of the control signals and generate one or more estimated states therefrom; and

an audio system comprising at least one transducer and configured to accept one more of the control signals,

wherein the audio system is configured to drive the transducer with the control signals or a signal generated therefrom, and to produce the rendered audio stream.

48. The nonlinear control system in accordance with claim 47, wherein the model comprises a feed forward nonlinear state estimator configured to generate the estimated states.

49. The nonlinear control system in accordance with claim 47, wherein the model comprises an observer and the audio system comprises a means for producing one or more feedback signals, and

wherein the observer is configured to accept one or more of the feedback signals or signals generated therefrom and to generate one or more of the estimated states from one or more of the feedback signals and one or more of the control signals.

50. The nonlinear control system in accordance with claim 49, wherein the observer comprises an unscented Kalman filter or an augmented unscented Kalman filter to generate one or more of the estimated states.

51. The nonlinear control system in accordance with claim 47, wherein the controller comprises a protection block configured to analyze one or more of the input signals, the estimated states, and/or the control signals, and

wherein the protection block is further configured to modify the control signals based upon the analysis.

52. The nonlinear control system in accordance with claim 47, wherein:

the controller comprises a feed forward control system operably coupled to a feedback control system;

the model is configured to generate one or more reference signals from one or more of the estimated states;

the feed forward control system is configured to perform a nonlinear transformation on the input signals to produce an intermediate control signal; and

the feedback controller is configured to compare two or more of the intermediate control signal, the reference signals, and feedback signals to generate the control signals.

53. The nonlinear control system in accordance with claim 52, wherein the feedback controller comprises a PID control block.

54. The nonlinear control system in accordance with claim 52, wherein the feed forward controller comprises an exact input-output linearization controller.

55. The nonlinear control system in accordance with claim 47, wherein the audio system comprises a driver configured to interconnect the control signal with the transducer, to monitor one or more of a current signal, a voltage signal, a power signal, and/or a transducer impedance signal, and to provide the signal as feedback to one or more component of the nonlinear control system.

56. The nonlinear control system in accordance with claim 47, wherein the audio system comprises a feedback coordination block configured to accept one or more sensory signals generated by one or more sensors or transducers in the system, and to generate one or more feedback signals therefrom.

57. The nonlinear control system in accordance with claim 47, wherein the controller further includes a target dynamics block and an inverse dynamics block, and

wherein the target dynamics block is configured to modify one or more of the input signals, or a signal generated therefrom, and to generate a targeted spectral response therefrom, and

wherein the inverse dynamics block is configured to compensate for one or more nonlinear property of the audio system on the input signals or a signal generated therefrom.

58. The nonlinear control system in accordance with claim 57, wherein the target dynamics block and the inverse dynamics block are serially coupled.

59. The nonlinear control system in accordance with claim 47, further comprising an adaptive algorithm configured to monitor a distortion aspect of one or more signals within the nonlinear control system and to modify one or more aspects of the controller to reduce said distortion aspect.

60. The nonlinear control system in accordance with claim 59, wherein the controller further comprises one or more parametrically defined parameters,

wherein a function of the controller is dependent on the parameters, and

wherein the adaptive algorithm is configured to adjust one or more of the parameters to reduce the distortion aspect.

61. The nonlinear control system in accordance with claim 47, wherein the audio system comprises a means for estimating a characteristic temperature of the transducer and delivering the estimate to one or more of the controller and/or the model, and

wherein the controller and/or the model are configured to compensate for changes in the estimated characteristic temperature.

62. The nonlinear control system in accordance with claim 47, wherein the nonlinear control system is integrated into a consumer electronics device.

63. The nonlinear control system in accordance with claim 62, wherein the consumer electronics device is a smartphone, a tablet computer, or a soundbar.

64. The nonlinear control system in accordance with claim 47, wherein the transducer is selected from the group consisting of an electromagnetic loudspeaker, a piezoelectric actuator, an electroactive polymer-based loudspeaker, and an electrostatic loudspeaker.

67. A method for matching performance of a production speaker to a target speaker model comprising:

configuring the production speaker with a nonlinear control system in accordance with claim 47;

analyzing performance of the production speaker;

comparing the performance of the production speaker to that of the target speaker model; and

adjusting the nonlinear control system to modify the performance of the production speaker to correspond to the target speaker model.

68. The method in accordance with claim 67, further comprising iteratively performing the analyzing, comparing, and adjusting steps.

69. The method in accordance with claim 67, wherein the adjusting step is at least partially performed with an unscented Kalman filter.

65-66. -66. (canceled)