Adaptation performance improvements for active control of sound or vibration

• US 20020120415A1
• Filed: 02/27/2002
• Published: 08/29/2002
• 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.
• Granted Patent: US 6,772,074 B2
• Time in Patent Office: Days
• US Class Current: 702/69
• 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;

b) generating an estimate of a relationship between the sensed physical variables and the control commands, wherein the estimate is used in said step a) in generating the plurality of control commands;

c) sequentially adding a dither signal to each of the plurality of control commands;

d) measuring a response to said step c);

e) updating the estimate of the relationship based upon said step d).

2. The method of claim 1 wherein the dither signal added to each of the plurality of control commands in said step c) differs for each control command.

3. The method of claim 2 wherein the dither signal added to a given control command includes a triangular signal.

4. The method of claim 3 further including the step of choosing a direction for the triangular signal in order to avoid saturation for that control command

5. The method of claim 1 further including the steps of:

f) holding constant the control command to which the dither is added,

g) updating control commands other than the one to which the dither is added according to the function.

6. The method of claim 5 wherein said step e) is performed only for the control command to which the dither is added.

7. The method of claim 1 further including the step of determining a magnitude of the dither signal based upon a current magnitude of the control command to which the dither signal is added.

8. The method of claim 1 further including the steps of:

Varying a frequency of the dither signal to be added to each of the plurality of control commands; and

Extracting the information corresponding to each said control command.

9. 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.

10. The method of claim 9 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.

11. The method of claim 9 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.

12. The method of claim 11 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.

13. The method of claim 9 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

T_k+1=T_k+EK^T E=y−

T_kv K=Qv/(1+v^TQv),

the matrix Q is a diagonal matrix with elements q_i, and the variables q_i determine the adaptation gain corresponding to the i^th control command.

14. The method of claim 13 wherein:

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

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.

15. The method of claim 13 wherein:

each variable q_i at each time step is set according to the equation q_i=max(q₀, q_v|v_i|^N) where q₀ and q_v are parameters chosen for a particular application, |v_l| is a magnitude of change in the i^th control command and N is a positive integer.

17. The method of claim 16 wherein the control commands are filtered to match a filter that has been applied to the sensed physical variables.

18. The method of claim 17 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

19. The method of claim 18 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.

16. 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) where the control commands and sensed physical variables are filtered to improve the quality of the estimates prior to said step b).