Mutual active cancellation of fan noise and vibration

• US 20060103334A1
• Filed: 11/16/2004
• Published: 05/18/2006
• Est. Priority Date: 11/16/2004
• Status: Active Grant

• Current Assignee: Lenovo PC International Limited (Lenovo Group Ltd.)
• Original Assignee: International Business Machines Corporation
• Inventors: Abali, Bulent, Harper, Richard E., Guthridge, D. Scott, Manson, Peter A., Marr, Harry B. Jr.
• Granted Patent: US 7,282,873 B2
• Time in Patent Office: Days
• US Class Current: 318/67
• CPC Class Codes: F04D 25/166 using fans
• CPC Class Codes: F04D 29/665 by means of resonance chambers or interference

Abstract

A multi-fan apparatus and method incorporates mutual active cancellation of fan noise and/or vibrations. The multi-fan apparatus includes two or more fans circuits, each comprising a fan, a fan speed controller and a separate tachometer, and a fan phase controller. The phase controller is connected to at least one fan speed controller and to each tachometer. Each fan'"'"'s speed is independently and dynamically maintained at the same set speed by the fan speed controllers using an independent control loops. A noise and/or vibration cancellation phase difference between fans is determined in order to achieve destructive interference of pressure waves and, thus, noise and/or vibration reduction, in pre-determined region of a system incorporating the multi-fan apparatus. The phase controller establishes and maintains this cancellation phase difference between the fans based upon feedback from the tachometers.

Claims

1. A multi-fan apparatus comprising:

a first fan circuit comprising;

a first fan;

a first tachometer connected to said first fan; and

,

a first fan speed controller connected to said first fan;

a second fan circuit comprising;

a second fan;

a second tachometer connected to said second fan; and

,

a second fan speed controller connected to said second fan; and

,

a fan phase controller connected to said first fan speed controller and each of said tachometers, wherein said fan phase controller separates phases of rotation of said first fan and said second fan; and

,

wherein said first fan circuit and said second fan circuit operate independently.

2. The apparatus according to claim 1, further comprising a fan speed determiner connected each of said fan speed controllers for inputting a same set fan speed to each of said fan speed controllers.

3. The apparatus according to claim 1, wherein said tachometers are adapted to detect and signal fan phase of rotation information.

4. The apparatus according to claim 1, wherein said fan phase controller is adapted to separate phases of rotation of said first fan and said second fan to establish a cancellation phase of rotation difference for providing at least one of noise and vibration cancellation.

5. The apparatus according to claim 4, wherein said fan phase controller comprises a processing device, and

wherein said processing device is adapted to determine said fan speeds and to determine a current phase of rotation difference between said first fan and said second fan, based upon phase of rotation signals emanating from each of said tachometers;

wherein said processing device is further adapted to compare said cancellation phase difference with said current phase difference and to calculate a short term fan speed variation for at least one of said fans to separate said phases of rotation of said first fan and second fan to said cancellation phase difference; and

,

wherein said fan phase controller is further adapted to signal said short term fan speed variation to said first fan speed controller.

6. The apparatus according to claim 4, wherein said fan phase controller further comprises a memory device.

7. The apparatus according to claim 6, wherein said cancellation phase difference may be pre-determined for any given location, where at least one of noise and vibration cancellation is desired, within a system incorporating said apparatus;

and

wherein said pre-determined cancellation phase difference is stored in said memory device.

8. The apparatus according to claim 6, further comprising a cancellation phase difference determiner connected to at least one of sound and vibration sensors and to said fan phase controller;

and

wherein said cancellation phase difference determiner is adapted to dynamically determine said cancellation phase difference based upon measurements from said at least one sensor and to store said cancellation phase difference in said memory device.

9. The apparatus according to claim 4, wherein said cancellation phase difference is variable depending upon multiple factors, including but not limited to, the physical arrangement of said first fan and second fan within a system, the location of a region of said system where said cancellation is desired relative to the location of said fans, the speed of propagation of said pressure waves, the relative spacing between fan outlets in said system, and the number of fan blades on each fan.

10. A multi-fan apparatus comprising:

a first fan circuit comprising;

a first fan;

a first tachometer connected to said first fan; and

a first fan speed controller connected to said first fan;

a second fan circuit comprising;

a second fan;

a second tachometer connected to said second fan; and

a second fan speed controller connected to said second fan;

a fan speed determiner connected each of said fan speed controllers adapted to input a same set fan speed to each of said fan speed controllers; and

a fan phase controller connected to said first fan speed controller and each of said tachometers, wherein said fan phase controller is adapted to separate phases of rotation of said first fan and said second fan to establish a cancellation phase of rotation difference for providing at least one of noise and vibration cancellation;

wherein said first fan circuit and said second fan circuit operate independently.

11. The apparatus according to claim 10, wherein said tachometers are adapted to detect and signal fan speed and phase of rotation.

12. The apparatus according to claim 11, wherein said fan phase controller comprises a processing device, and

wherein said processing device is adapted to read said fan phase of rotation signals emanating from each of said tachometers and to determine fan speeds and a current phase of rotation difference between said first fan and said second fan;

wherein said processing device is further adapted to compare said cancellation phase difference with said current phase difference, and calculate a short term fan speed variation for at least one of said fans to separate said phases of rotation of said first fan and second fan to said cancellation phase difference; and

wherein said fan phase controller is further adapted to signal said short term fan speed variation to said first fan speed controller.

13. The apparatus according to claim 10, wherein said fan phase controller further comprises:

a memory device.

14. The apparatus according to claim 13, wherein said cancellation phase difference may be pre-determined for any given location, where at least one of noise and vibration cancellation is desired, within a system incorporating said apparatus;

and

wherein said pre-determined cancellation phase difference is stored in said memory device.

15. The apparatus according to claim 13, further comprising a cancellation phase difference determiner connected to at least one of sound and vibration sensors and to said fan phase controller;

and

wherein said cancellation phase difference determiner is adapted to dynamically determine said cancellation phase difference based upon measurements from said at least one sensor and to store said cancellation phase difference in said memory device.

16. The apparatus according to claim 10, wherein said cancellation phase difference is variable depending upon multiple factors, including but not limited to, the physical arrangement of said first fan and second fan within a system, the location of a region of said system where said cancellation is desired relative to the location of said fans, the speed of propagation of said pressure waves, the relative spacing between fan outlets in said system, and the number of fan blades on each fan.

17. A fan noise and vibration cancellation method, said method comprising:

determining a cancellation phase difference between at least two fans to provide at least one of noise and vibration cancellation;

independently maintaining said at least two fans at the same set speed; and

adjusting the phase of rotation of at least one of said fans relative to the phase of rotation of another of said fans to establish and maintain said cancellation phase difference.

18. The method according to claim 17, said cancellation phase difference causes destructive interference to at least one of sound and vibration pressure waves in a pre-determined localized region, where said cancellation is desired, within a system incorporating said fans.

19. The method according to claim 17, wherein adjusting the phase of rotation of at least one of said fans relative to the phase of rotation of another of said fans to establish and maintain said cancellation phase difference further comprises:

reading phase of rotation signals emanating from tachometers connected to each of said fans, and

determining a current phase of rotation difference between said fans.

20. The method according to claim 19, wherein adjusting the phase of rotation further comprises:

comparing said cancellation phase difference with said current phase difference, and

calculating a short term fan speed variation for at least one of said fans which would separate the phases of rotation between said fans to establish said cancellation phase difference.

21. The method according to claim 20, wherein adjusting the phase of rotation further comprises:

signaling said short term fan speed variation to said fan speed controller.

22. The method according to claim 17, wherein determining a cancellation phase difference further comprises:

pre-determining said cancellation phase difference to provide at least one of noise and vibration cancellation in a pre-determined region of a system incorporating said fans.

23. The method according to claim 17, wherein determining a cancellation phase difference further comprises:

dynamically determining said cancellation phase difference.

24. The method according to claim 23, wherein dynamically determining said cancellation phase difference comprises:

measuring at least one of sound and vibration in a pre-determined region, where at least one of noise and vibration cancellation is desired, of a system incorporating said fans; and

determining and adjusting said cancellation phase difference based upon said measurement.

25. The method according to claim 22, wherein said cancellation phase difference remains static.

26. A fan noise and vibration cancellation method, said method comprising:

determining a cancellation phase difference between at least two fans to provide at least one of noise and vibration cancellation;

independently maintaining said at least two fans at the same set speed using independent control loops; and

adjusting the phase of rotation of at least one of said fans relative to the phase of rotation of another of said fans to establish and maintain said cancellation phase difference, using a fan phase controller.

27. The method according to claim 26, wherein each of said independent control loops comprise:

a fan,

a tachometer connected to said fan, and

a fan speed controller connected to said fan;

wherein a same set speed is input into each of said fan speed controllers by a fan speed determiner; and

wherein, within each control loop, each fan speed controller is adapted to maintain said fan at said set speed based upon readings from said tachometer.

28. The method according to claim 26, said cancellation phase difference causes destructive interference to at least one of sound and vibration pressure waves in a pre-determined region, where said at least one of noise and vibration cancellation is desired, within a system incorporating said fans.

29. The method according to claim 26, wherein said fan phase controller is adapted to read phase of rotation signals emanating from said tachometers and to determine a current phase of rotation difference between said fans.

30. The method according to claim 29, wherein said fan phase controller is further adapted to compare said cancellation phase difference with said current phase difference, and to calculate a short term fan speed variation for at least one of said fans which would separate the phases of rotation between said fans to establish said cancellation phase difference.

31. The method according to claim 30, wherein said fan phase controller is further adapted to signal said short term fan speed variation to said fan speed controller.

32. The method according to claim 26, wherein determining a cancellation phase difference further comprises:

dynamically determining said cancellation phase difference.

33. The method according to claim 31, wherein dynamically determining said cancellation phase difference comprises:

using sensors to continuously measure at least one of sound and vibration in a pre-determined region, where said cancellation is desired, of a system incorporating said fans; and

dynamically changing said cancellation phase difference based upon readings from said sensors.

34. The method according to claim 26, wherein determining a cancellation phase difference further comprises:

pre-determining said cancellation phase difference to provide at least one of noise and vibration cancellation in a pre-determined region of a system incorporating said fans.

35. The method according to claim 34, wherein said pre-determined cancellation phase difference is static.