Energy harvesting for wireless sensor operation and data transmission

• US 20040078662A1
• Filed: 03/05/2003
• Published: 04/22/2004
• Est. Priority Date: 03/07/2002
• Status: Active Grant

• Current Assignee: Hottinger Bruel & Kjaer Incorporated
• Original Assignee: MicroStrain, Inc. (Spectris PLC)
• Inventors: Arms, Steven W., Townsend, Christopher P., Hamel, Michael John, Churchill, David L.
• Granted Patent: US 7,081,693 B2
• Time in Patent Office: Days
• US Class Current: 714/22
• CPC Class Codes: B60C 23/0411 Piezoelectric generators
• CPC Class Codes: H02J 7/32 for charging batteries from a charging set comprising a non-electric prime mover rotating at constant speed
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: H02N 2/186 Vibration harvesters
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

A device for powering a load from an ambient source of energy is provided. The device includes an energy harvesting device for harvesting energy from the ambient source of energy wherein the rate energy is harvested from the ambient source of energy is below that required for directly powering the load. A storage device is connected to the energy harvesting device. The storage device receives electrical energy from the energy harvesting device and is for storing the electrical energy. A controller is connected to the storage device is for monitoring the amount of electrical energy stored in the storage device and for switchably connecting the storage device to the load when the stored energy exceeds a first threshold. The system can be used for

Claims

1. A device for powering a load from an ambient source of energy, comprising:

an energy harvesting device for harvesting energy from the ambient source of energy, herein the rate energy is harvested from the ambient source of energy is below that required for directly powering the load;

a storage device connected to said energy harvesting device, wherein said storage device receives electrical energy from said energy harvesting device and wherein said storage device is for storing said electrical energy; and

a controller connected to said storage device for monitoring the amount of electrical energy stored in said storage device and for switchably connecting said storage device to the load when said stored energy exceeds a first threshold.

2. A device as recited in claim 1, wherein said controller is powered by energy stored in said storage device.

3. A device as recited in claim 1, wherein said controller is further for switchably disconnecting said storage device from the load when said stored energy is below a second threshold.

4. A device as recited in claim 2, wherein said controller includes a monitoring device and a first switch.

5. A device as recited in claim 3, wherein said monitoring device includes a voltage sensitive switch or a voltage comparitor.

6. A device as recited in claim 5, wherein said monitoring device includes an integrated circuit having said nanoamp comparator and a reference voltage source.

7. A device as recited in claim 6, wherein said voltage comparitor monitors its input voltage relative to a reference voltage and wherein said first threshold is set by said reference voltage.

8. A device as recited in claim 6, wherein said monitoring device further includes an internal switch, wherein an output of said monitoring device causes said internal switch to close when storage device voltage reaches or exceeds said first threshold to connect said storage device to the load for using said stored energy.

9. A device as recited in claim 8, wherein an output of said monitoring device causes said internal switch to open when storage device voltage discharges to a second threshold to disconnect said storage device from the load.

10. A device as recited in claim 4, wherein said first switch is for holding the load in an off state while voltage to said monitoring device is below a level needed for properly operating said monitoring device.

11. A device as recited in claim 10, wherein said first switch has a gate connected to a terminal of said storage device.

12. A device as recited in claim 10, wherein said first switch has a first terminal connected to the load and a second terminal connected to ground.

13. A device as recited in claim 1, wherein said energy harvesting device comprises a piezoelectric transducer (PZT) for generating electrical energy from ambient mechanical energy.

14. A device as recited in claim 13, wherein said piezoelectric transducer is connected to said storage device through a rectifier.

15. A device as recited in claim 14, further comprising a circuit having an impedance approximately matching load impedance of the PZT to improve efficiency of energy collection.

16. A device as recited in claim 15, wherein said circuit comprises a small capacitor and a DC-DC converter to transfer charge from said small capacitor to said storage device.

17. A device as recited in claim 16, wherein said circuit further comprises a second switch connected to a terminal of said small capacitor, wherein said second switch enables said DC-DC converter when voltage across said small capacitor reaches a third threshold value.

18. A device as recited in claim 17, wherein said third threshold value is a multiple of a turn on voltage of said second switch.

19. A device as recited in claim 17, wherein said multiple is provided by a voltage divider.

20. A device as recited in claim 17, wherein said voltage divider has a total resistance exceeding 10 megohms.

21. A device as recited in claim 17, further comprising a timing capacitor for providing a RC time delay to keep said second switch on while said small capacitor discharges.

22. The sensing system as recited in claim 13, wherein said PZT is mounted on a tuned flexural element.

23. A device as recited in claim 22, wherein said tuned flexural element comprises a cantilever beam.

24. A device as recited in claim 23, wherein said cantilever beam is tapered.

25. A device as recited in claim 24, wherein magnitude of said taper is set to provide a constant strain along its length.

26. A device as recited in claim 22, wherein said tuned flexural element includes an adjustable mass.

27. A device as recited in claim 13, wherein said piezoelectric material is attached to a structural member subject to strain.

28. A device as recited in claim 13, wherein said a piezoelectric generating device comprises a piezoelectric fiber, a piezoelectric hard ceramic or a piezoelectric polymer.

29. A device as recited in claim 1, wherein said ambient source of energy comprises ambient mechanical energy or ambient magnetic field coupled energy.

30. A device as recited in claim 28, wherein said ambient magnetic coupled energy comprises a power transmission line.

31. A device as recited in claim 1, wherein said storage device comprises a battery or a capacitor.

32. The device as recited in claim 31, wherein said battery comprises a thin film battery.

33. A device as recited in claim 1, wherein said load comprises a sensor, a transmitter, a sensor transmitter network, or an actuator.

34. The sensing system as recited in claim 33, wherein power is intermittently provided to said sensor to reduce power consumption.

35. The sensing system as recited in claim 33, wherein said sensor is a passive sensor.

36. The sensing system as recited in claim 35, wherein said passive sensor can be reset remotely.

37. The sensing system as recited in claim 35, wherein said passive sensor comprises a shape memory alloy.

38. The sensing system as recited in claim 35, wherein said sensor comprises a passive strain accumulation sensor.

39. The sensing system as recited in claim 33, wherein said sensor is embedded in another material.

40. A device as recited in claim 33, wherein said transmitter is for wirelessly transmitting a signal for triggering an action.

41. A device as recited in claim 1, further comprising a tire, wherein said device is for mounting on said tire for sensing and transmitting tire temperature or tire pressure information.

70. A system as recited in claim 35, wherein said high capacity storage device is for powering a data storage device or an actuator.

71. A system as recited in claim 35, wherein said high capacity storage device is for powering or reading a sensor.

72. The system as recited in claim 35, further comprising a processor wherein said sensor is programmable by said processor.

73. The system as recited in claim 35, wherein said piezoelectric transducer is excited by wind, water, wave, tide, strain, or vibrational energy.

74. The system as recited in claim 35, wherein the system is resistant to degradation from moisture, salt, or vibration.

75. A device as recited in claim 35, further comprising a tire, wherein said device is for mounting on said tire for sensing and transmitting tire temperature or tire pressure information.

42. An energy harvesting system comprising:

a piezoelectric transducer;

a rectifier;

a reactive device having a high impedance approximately matching impedance of said piezoelectric transducer at its operating frequency for efficiently transferring energy from said piezoelectric transducer to said reactive device;

a low impedance high capacity storage device;

a circuit for monitoring voltage across said reactive device, and for transferring said charge from said reactive device to said low impedance high capacity storage device when said voltage across said reactive device reaches a specified voltage value.

43. A system as recited in claim 42, wherein said circuit provides impedance transformation.

44. A system as recited in claim 43, wherein said circuit includes a DC-DC converter and a device for switching on said DC-DC converter at said specified voltage value.

45. A system as recited in claim 43, wherein said circuit further includes a device for switching off said DC-DC converter when said reactive device discharges to a specified discharged voltage value.

46. A system as recited in claim 43, wherein said device for switching off said DC-DC converter when said reactive device discharges to a specified discharged voltage value comprises a timing circuit.

47. A system as recited in claim 43, wherein said high capacity storage device comprises a first capacitor or a battery.

48. A system as recited in claim 43, wherein said reactive device comprises a second capacitor.

49. A system as recited in claim 43, wherein said high capacity storage device is for powering a wireless transmitter or first transceiver for wireless communication of information.

50. A system as recited in claim 49, further comprising a sensor, wherein said wireless transmitter or first transceiver is for wireless communication of sensor information.

51. The system as recited in claim 49, further comprising a base station for receiving said wirelessly transmitted information.

52. The system as recited in claim 51, wherein said base station comprises a receiver or a second transceiver.

53. The system as recited in claim 51, further comprising a plurality of said systems, each said system capable of wirelessly transmitting information to said base station.

54. The system as recited in claim 53, wherein each of said systems further comprises an address.

55. The system as recited in claim 54, wherein each of said systems is capable of transmitting or recognizing said address.

56. The system as recited in claim 51, wherein said base station comprises an Ethernet enabled receiver.

57. The system as recited in claim 56, wherein said Ethernet enabled receiver uses extensible markup language (XML) data output format to enable multiple users on a local area network to view said information using a standard internet browser.

58. The system as recited in claim 56, wherein time division multiple access (TDMA) is used to control communications, wherein said systems are in sleep mode except when awakened to transmit bursts of data.

59. The system as recited in claim 56, further comprising a temperature sensor, a strain gauge, a pressure sensor, a magnetic field sensor, an accelerometer, a or DVRT.

60. The system as recited in claim 56, wherein said sensor comprises a device to monitor machine health through sensor values.

61. The system as recited in claim 50, further comprising a processor and a data logger for recording sensor data.

62. The system as recited in claim 61, wherein said data logger comprises non-volatile memory.

63. The system as recited in claim 51, further comprising a bi-directional RF transceiver, wherein said base station orchestrates sample triggering and high speed logging of said sensor data.

64. The system as recited in claim 51, wherein data is processed locally then uploaded when polled by said base station.

65. The system as recited in claim 53, wherein each of said systems comprises a unique identification code.

66. The system as recited in claim 42, wherein said wireless transmitter can transmit frequency shift keyed digital sensor data with checksum bytes.

67. The system as recited in claim 57, wherein said wireless transmitter comprises differential or pseudo-differential channels.

68. The system as recited in claim 57, wherein said wireless transmitter further comprises a data logger including on-board non-volatile memory, user programmable digital filter, gain, and sample rates, and built-in error checking of pulse code modulated (PCM) data.

69. The system as recited in claim 59, wherein said data logger is for storing said information for later transmission by said transmitter.

76. A device for sensing temperature or pressure in a tire comprising:

a tire;

a PZT mounted on said tire;

a circuit for harvesting energy from said PZT, wherein said circuit comprises an element having an impedance approximately matching impedance of said PZT; and

a sensing module connected to said circuit, said sensing module including a sensor and a circuit for wirelessly transmitting sensor information.