Source: https://patents.google.com/patent/US20080047363
Timestamp: 2018-02-24 06:31:58
Document Index: 205967404

Matched Legal Cases: ['art.\n14', 'art.\n15', 'art.\n16', 'art.\n17', 'art.\n18', 'art.\n24', 'art.\n29', 'art.\n36']

US20080047363A1 - Shaft mounted energy harvesting for wireless sensor operation and data trasmission - Google Patents
US20080047363A1
US20080047363A1 US11891957 US89195707A US2008047363A1 US 20080047363 A1 US20080047363 A1 US 20080047363A1 US 11891957 US11891957 US 11891957 US 89195707 A US89195707 A US 89195707A US 2008047363 A1 US2008047363 A1 US 2008047363A1
US8011255B2 (en )
This patent application is a divisional of U.S. patent application Ser. No. 10/769,642, filed Jan. 31, 2004, and claims priority of that application. The Ser. No. 10/769,642 application is a continuation-in-part of Ser. No. 10/379,223, filed Mar. 5, 2003.
Ser. No. 10/379,224, docket number 115-004, filed Mar. 5, 2003 incorporated herein by reference; and
In addition, the present inventors recognized that if the available power in the piezoelectric element were to be efficiently converted from its low current and high impedance current source to a voltage source, the capacitor could be charged much faster than if the same capacitor were charged directly from the short circuit current of the piezoelectric element without this conversion. For example, if a voltage converter can present a 500 K load to the piezoelectric element, approximately matching its impedance, the element will deliver 17.5 volts at 35 uA or 610 microwatts. If this power was then converted down to 100 ohms source impedance, even at 80% efficiency, the charge current would be more than 2.2 mA. By comparison, the output at the same level of excitation of the piezoelectric element when loaded to 100 ohms without a converter, is 6 millivolts at 60 uA or 0.36 microwatts, about 1,700 times less power.
The present inventors found that they could epoxy torsional strain gauges 164 a, 164 b to shaft 117, as shown in FIG. 15, for measuring torsional strain in shaft 117. They could then convert this measured strain to torque of shaft 117 using the equation below, where T is the calculated torque, ε is the torsional strain as measured by torsional strain gauge 136 b, Do is the outer diameter of shaft 117, Di is the inner diameter of shaft 117, E is the modulus of elasticity of the material of which shaft 117 is fabricated, and ν is the Poisson Ratio Poisson ratio is material property having to do with width v. stretch of that material. Torque ⁢ ⁢ ( T ) = ɛ * π ⁢ ⁢ ( Do 4 - Di 4 ) ⁢ E 16 ⁢ D 0 ⁡ ( 1 + v ) ( 1 )
In another example, presently motor current is frequently monitored to determine an end point to processing with a machine, such as polishing machine, by detecting a change in current, when polishing removes one layer of material and starts polishing a different material with a different hardness. However, motor current may vary widely during such a polishing operation. Also motor current is only an indirect indicator of torque in the shaft driving the polishing tool. One embodiment allows a direct measurement of this torque, or another relevant mechanical property of the shaft, such as strain, and this data is transmitted from shaft 117 and received at base station 146 and provided as an analog output for use adjusting operation of motor 244 driving shaft 117. By directly measuring shaft mechanical properties and feeding back data to driving motor 244, greater accuracy in controlling torque in driving shaft 117 can be provided and such problems as overpolishing or metal fatigue in drive shaft 117 from over-driving can be prevented.
a. providing a shaft a sensor, a processor, an energy storage device, and a transmitter;
b. mounting said sensor directly on said shaft;
c. mounting said processor, said energy storage device, and said transmitter to rotate with said shaft;
d. rotating said shaft;
e. waking said processor for a period of time and drawing energy to said processor from said energy storage device to provide said processor in an active mode during said period of time;
f. sampling said sensor during said period of time;
g. returning the processor to sleep mode; and
h. transmitting data derived from said sensor.
2. A method as recited in claim 2, wherein said shaft is on a machine for delivering torque.
6. A method as recited in claim 1, wherein said sampling said sensor comprises a frequency less than about 1 Hz to a frequency of about 1 kHz.
7. A method as recited in claim 1, wherein said processor further comprises controlling power to said sensor and wherein said processor sends a signal to provide power to said sensor only during said time period.
8. A method as recited in claim 1, wherein said processor further comprises controlling power to said transmitter wherein said processor provides power to said transmitter only during said active mode time period.
9. A method as recited in claim 1, wherein said mounting further comprises mounting sensor signal conditioning to rotate with said rotating shaft, wherein said processor further comprises controlling power to said sensor signal conditioning, wherein said processor provides power to said sensor signal conditioning only during said time period.
10. A method as recited in claim 9, wherein said mounting further comprises mounting a sensor signal conditioning power supply on said rotatable part for powering said sensor signal conditioning, wherein said sensor signal conditioning power supply comprises an enable pin, wherein said processor further comprises controlling operation of said sensor signal conditioning power supply by sending a signal to said enable pin.
11. A method as recited in claim 10, wherein said mounting further comprises mounting a transmitter power supply on said rotatable part, wherein said processor has separate controls to enable said sensor signal conditioning power supply and to enable said transmitter power supply wherein said processor further comprises enabling said signal conditioning power supply independently of enabling said transmitter power supply.
12. A method as recited in claim 11, wherein said mounting further comprises mounting a sensor power supply on said rotatable part, wherein said processor has an additional separate control to enable said sensor power supply wherein said processor further comprises independently enabling said sensor power supply.
13. A method as recited in claim 1, wherein said processor further comprises computing strain of said rotating part.
14. A method as recited in claim 1, wherein said processor further comprises computing torque of said rotating part.
15. A method as recited in claim 1, wherein said processor further comprises computing angular velocity or RPM of said rotating part.
16. A method as recited in claim 1, wherein said processor further comprises computing instantaneous mechanical power of said rotating part.
17. A method as recited in claim 1, wherein said mounting further comprises mounting a receiver or transceiver on said rotatable part.
18. A method as recited in claim 17, further comprising receiving a command through said receiver or transceiver to wake up said processor.
22. A method as recited in claim 1, wherein said mounting further comprises mounting an energy harvesting circuit on said rotatable part.
24. A method as recited in claim 22, further comprising providing a magnetic field adjacent said rotatable part, wherein said energy harvesting circuit comprises an inductor for harvesting energy from rotation of said rotating part in said magnetic field.
25. A method as recited in claim 1, wherein said mounting further comprises providing a circuit for measuring state of charge of said energy storage device on said rotatable part, said method further comprising providing a first measurement of said state of charge of said energy storage device.
27. A method as recited in claim 25, further comprising using said first measurement of state of charge in said processor to determine one of: rate of sampling data from said sensor, how long to sample data from said sensor, time between samplings of data from said sensor, how long to keep said processor in sleep mode, when to awaken said processor, how long to keep said processor awake, time for providing power to said sensor, and time for providing power to said transmitter.
28. A method as recited in claim 1, wherein said mounting further comprises mounting a non-volatile memory on said rotatable part.
29. A method as recited in claim 29, wherein said non-volatile memory includes a unique address to identify data transmitted from said rotating shaft.
30. A method as recited in claim 29, further comprising storing data derived from said sensor in said non-volatile memory for transmitting by said transmitter at a later time.
33. A method of monitoring a rotating part, comprising:
a. mounting a sensor, a processor, an energy storage device, a non-volatile memory, and a transmitter on a rotatable part;
c. waking said processor for a period of time and drawing energy to said processor from said energy storage device to provide said processor in an active mode during said period of time;
d. sampling said sensor and storing data derived from said sensor in said non-volatile memory during said period of time;
e. returning said processor to sleep mode; and
f. transmitting data derived from said sensor and stored in said non-volatile memory.
34. A method of monitoring a rotating part, comprising:
a. mounting a sensor, a processor, and an energy supplying device, on a rotatable part;
c. waking said processor for a period of time and drawing energy to said processor from said energy supplying device to provide said processor in an active mode during said period of time;
d. sampling said sensor during said period of time;
e. automatically adjusting operation of said rotatable part based on said data; and
f. returning said processor to sleep mode.
35. A method as recited in claim 34, further comprising providing a device driving said rotatable part, wherein said adjusting operation of said rotatable part based on said data includes adjusting operation of said device driving said rotatable part.
36. A method as recited in claim 35, wherein said device driving said rotatable part is a motor.
US20080047363A1 true true US20080047363A1 (en) 2008-02-28
US8011255B2 US8011255B2 (en) 2011-09-06
US12947502 Granted US20110060535A1 (en) 2002-03-07 2010-11-16 Method of Operating a Rotatable Part
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