Mutual active cancellation of fan noise and vibration
View Patent ↗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.
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 to 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 cancellation 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 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 cancellation 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 a sound sensor and a vibration sensor 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 of said sound sensor and said vibration 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 cancellation 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 a sound sensor and a 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.