Adaptation performance improvements for active control of sound or vibration

• US 6,772,074 B2
• Filed: 02/27/2002
• Issued: 08/03/2004
• Est. Priority Date: 02/27/2001
• Status: Active Grant

• Current Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation)
• Original Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation)
• Inventors: MacMartin, Douglas G., Millott, Thomas A., Park, Christopher G.
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US10/083,949
• Publication Number:
  US 20020120415A1
• Time in Patent Office: 888 Days
• Field of Search: 702/56, 700/280, 244/1.N, 381/71.4, 381/71.11
• US Class Current: 702/56
• CPC Class Codes: F16F 15/00 Suppression of vibrations in systems damping of non-rotary systems using inertia effect F16F7/10; prevention or isolation of vibrations in machine tools B23Q11/0032; suppression of driveline vibrations in hybrid vehicle transmissions B60W30/20 ; vehicle seat suspension devices B60N2/50; methods or devices for protecting against, or damping of, acoustic waves, e.g. sound G10K11/16; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion vibration absorbing or balancing means for aircraft propellers B64C11/008, for rotorcraft rotors B64C27/001 ; testing static and dynamic balance of machines or structures G01M1/00
• CPC Class Codes: F16F 15/02 Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems F16F15/005 takes precedence ; layered products B32B; suppression of vibration in ships B63; relieving load on bearings, using magnetic means F16C39/06
• CPC Class Codes: G05B 13/0225 being a periodic perturbation
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/17833 by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
• CPC Class Codes: G10K 11/17853 of the filter
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17875 using an error signal without a reference signal, e.g. pure feedback

Abstract

A noise or vibration control system improves the quality of adaptation estimates by filtering the input signals to the adaptation, selectively implementing a “dead-zone” during which adaptation does not occur and by selectively adding a dither signal to the control commands. The dead-zone is based on the magnitude of the changes in the control commands, which are responding to the changes in the sensor signals. The dead-zone can be applied to all actuators simultaneously, or can be applied to the adaptation of each actuator channel independently. To maintain identifiability, a “dither signal” is added to the control commands to “ping” the system to increase the amount of information available to the adaptive algorithm. The dither signal is preferably implemented on only one actuator channel at a time. Also, the dither amplitude for each channel is preferably set to be proportional to the current control amplitude. The quality of the adaptation estimates is also improved by filtering the input signals to the adaptation circuit, y_k=Δz_k, and v_k=Δu_k. Among other things, the filter matches the filtering applied by the harmonic estimator.

Claims

1. A method for reducing sensed physical variables including the steps of:

a) generating a plurality of control commands as a function of the sensed physical variables based upon an estimate of a relationship between the sensed physical variables and the control commands;

b) updating the estimate of the relationship based upon a response by the sensed physical variables; and

c) varying a size of the update to the estimate in said step b) based upon a magnitude of change over time by at least one of the plurality of control commands, wherein the estimate of the change in response y=Δ

z due to a chance in control command v=Δ

u at a specific time t_k is denoted T_k,

where T_k is updated according to the equations

2. The method of claim 1 further including the step of selecting between updating or leaving unchanged the estimate of the relationship based upon a magnitude of change by the plurality of control commands.

3. The method of claim 1 further including the step of:

d) selecting between updating or leaving unchanged the estimate corresponding to a first control command of the plurality of control commands based upon the magnitude of the change in the first control command.

4. The method of claim 3 further including the steps of comparing the magnitude of the change to a threshold and varying the threshold based upon an estimate of a signal to noise ratio.

5. The method of claim 1 wherein:

a) each variable q_i at each time step is set equal to zero or to some nominal value depending on whether |v_i|>

δ

_i where |v_i| is a magnitude of change in the i^th control command and the variables δ

_i are the deadzone threshold for channel i.

6. The method of claim 1 wherein:

each variable q_i at each time step us set according to the equation q_i=max (q_o, q_v|v_i|^N) where q_o and q_v are parameters chosen for a particular application, |v_i| is a magnitude of change in the i^th control command and N is a positive integer.

7. The method of claim 1 wherein the estimate of the relationship is given by Δ

z=TΔ

u, where Δ

z is a change in the sensed physical variables and Δ

u is a change in the control commands.

8. A method for reducing sensed physical variables including the steps of:

a) generating a plurality of control commands as a function of the sensed physical variables based upon an estimate of a relationship between the sensed physical variables and the control commands;

b) updating the estimate of the relationship based upon a response by the sensed physical variables;

c) where the control commands are filtered to match a filter that has been applied to the sensed physical variables to improve the quality of the estimates prior to said step b); and

wherein a change in the sensed physical variables Δ

z is related to a change in the control commands Δ

u by Δ

z=T(Δ

u), the estimate of a sensed physical variable response T is based on Δ

u and Δ

z, said method further including the step of filtering Δ

u to match a known filter on Δ

z.

9. The method of claim 8 further including the step of low-pass filtering both Δ

u and Δ

z to reduce an impact of high-frequency noise on the estimate of T.

10. A system for controlling a plurality of sensed physical variable comprising:

a plurality of sensors for measuring the physical variables;

a control unit generating an estimate of a relationship between the sensed physical variables and a plurality of control commands, and generating the plurality of control commands over time based upon the sensed physical variables and based upon the relationship; and

a plurality of force generators activated based upon said plurality of command signals;

wherein the control unit sequentially adds a signal to each of the plurality of control commands, measures the response to the signal and updates the estimate of the relationship based upon the response, wherein the signal added by the control unit is a dither signal that initially decreases in order to avoid saturation for that control command.

11. The system of claim 10 wherein the signal added to each of the plurality of control commands by the control unit differs for each control command.

12. The system of claim 11 wherein the signal added to a given control command includes a triangular signal.

13. The system of claim 10 wherein the control unit holds constant the control command to which the signal is added and updates the control commands other than the one to which the signal is added according to the relationship.

14. The system of claim 13 wherein the control unit updates the relationship only for the control command to which the signal is added.

15. The system of claim 10 wherein the control unit determines a magnitude of the signal based upon a current magnitude of the control command to which the signal is added.

16. The system of claim 10 wherein the control unit varies a frequency of the signal to be added to each of the plurality of control commands and extracts the information corresponding to each said control command.

17. A system for controlling a plurality of sensed physical variable comprising:

a plurality of sensors for measuring the physical variables;

a control unit generating an estimate of a relationship between the sensed physical variables and a plurality of control commands, and generating the plurality of control commands over time based upon the sensed physical variables, and based upon the relationship; and

a plurality of force generators activated based upon said plurality of command signals;

wherein the control unit varies a size of the update to the estimate of the relationship based upon a magnitude of change over time by at least one of the plurality of control command and wherein the control unit selects between updating or leaving unchanged the estimate of the relationship based upon a magnitude of change by the plurality of control commands.

18. The system of claim 17 wherein the control unit compares the magnitude of the change to a threshold and varies the threshold based upon an estimate of a signal to noise ratio.

19. The system of claim 18 wherein

the estimate of the change in response y=Δ z due to a change in control command v=Δ

u at a specific time t_k is denoted T_k,

where T_k is updated according to the equations

20. The system of claim 19 wherein the control unit sets each variable q_i to zero or some nominal value at each time step depending on whether |v_i|>

δ

_i where |v_i| is a magnitude of change in the i^th control command and the variables δ

_i are a deadzone threshold for channel i.

21. A method for reducing sensed physical variables including the steps of:

a) generating a plurality of control commands as a function of the sensed physical variables based upon an estimate of a relationship between the sensed physical variables and the control commands;

b) updating the estimate of the relationship based upon a response by the sensed physical variables; and

c) varying a size of the update to the estimate in said step b) based upon a magnitude of change over time by at least one of the plurality of control commands, wherein the estimate of the relationship is given by Δ

z=TΔ

u, where Δ

z is a change in the sensed physical variables and Δ

u is a change in the control commands, and wherein the size of the update is varied in said step c) based upon a comparison of ||Δ

u|| to a threshold.

22. The method of claim 21 further including the step of selecting between updating or leaving unchanged the estimate of the relationship based upon the comparison of ||Δ

u|| to a threshold.