Shaft mounted energy harvesting for wireless sensor operation and data transmission

• US 20050017602A1
• Filed: 01/31/2004
• Published: 01/27/2005
• Est. Priority Date: 03/05/2003
• Status: Active Grant

• Current Assignee: Lord Corporation (Parker-Hannifin Corporation)
• Original Assignee: MicroStrain, Inc. (Spectris PLC)
• Inventors: Arms, Steven W., Townsend, Christopher P., Hamel, Michael J., Churchill, David L.
• Granted Patent: US 7,256,505 B2
• Time in Patent Office: Days
• US Class Current: 310/339
• CPC Class Codes: B60C 23/0411 Piezoelectric generators
• CPC Class Codes: B60C 23/0413 Wireless charging of active radio frequency circuits
• CPC Class Codes: B60C 23/0433 Radio signals
• CPC Class Codes: G01D 21/00 Measuring or testing not otherwise provided for
• CPC Class Codes: G01D 5/185 using piezoelectric sensors
• CPC Class Codes: G01L 3/108 involving resistance strain gauges
• CPC Class Codes: G01M 5/00 Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings G01M9/00 takes precedence
• 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: H02K 11/21 Devices for sensing speed or position, or actuated thereby specially adapted for machines having non-mechanical commutating devices H02K29/06, H02K29/14
• CPC Class Codes: H02K 11/24 Devices for sensing torque, or actuated thereby H02K11/27 takes precedence
• CPC Class Codes: H02K 11/25 Devices for sensing temperature, or actuated thereby
• CPC Class Codes: H02K 11/26 Devices for sensing voltage, or actuated thereby, e.g. overvoltage protection devices
• CPC Class Codes: H02K 7/1846 structurally associated with wheels or associated parts dynamos arranged in the wheel hub of cycles B62J6/12
• CPC Class Codes: H02N 11/002 Generators
• CPC Class Codes: H02N 2/186 Vibration harvesters

Abstract

A device for monitoring a rotating shaft is provided. The device measures strain in the shaft and provides angular velocity and torque in the shaft. The device includes a sensor, sensor conditioning circuitry, a microprocessor, and a transmitter, all located on a rotating shaft. The device obtains power by harvesting mechanical energy of the rotating shaft itself. Coils are provided rotating with the shaft and permanent magnets are mounted adjacent the rotating shaft so electrical energy is induced in the coils as they rotate through the magnetic field of the permanent magnets. A battery or capacitor is connected to the coils for storing energy. A microprocessor is connected to the sensors, the storage device, and the transmitter for managing power consumption and for monitoring the amount of electrical energy stored in the storage device and for switchably connecting the storage device to the transmitter when the stored energy exceeds a threshold.

Claims

1. A device, comprising:

a rotating shaft;

an energy harvesting circuit mounted on said rotating shaft, said energy harvesting circuit for harvesting mechanical energy from motion of said rotating shaft and converting said mechanical energy into electricity; and

a radio frequency communications device mounted on said rotating shaft and connected to receive electricity derived from said energy harvesting circuit.

2. A device as recited in claim 1, further comprising a magnetic field and an inductor, wherein said magnetic field is arranged adjacent said rotating shaft and said inductor is arranged on said rotating shaft, wherein said energy harvesting device harvests energy from a pulse of electricity induced in said inductor by rotation of said inductor through said magnetic field.

3. A device as recited in claim 2, further comprising a permanent magnet arranged adjacent said rotating shaft, wherein said magnetic field is provided by said permanent magnet.

4. A device as recited in claim 2, wherein said inductor comprises a coil or a Weigand device.

5. A device as recited in claim 4, further comprising a plurality of coils or Weigand devices mounted on said rotating shaft.

6. A device as recited in claim 1, wherein said rotating shaft comprises a measurable parameter, wherein a sensor is mounted on said rotating shaft for measuring said measurable parameter, further wherein said radio frequency communications device comprises a transmitter, said transmitter for transmitting said measurement or for transmitting data derived from said measurement.

7. A device as recited in claim 6, wherein said sensor comprises a temperature sensor, a strain gauge, a torque sensing device, a sensor, or an accelerometer.

8. A device as recited in claim 7, wherein said strain gauge comprises resistance devices sensitive to strain.

9. A device as recited in claim 8, wherein said resistance devices are arranged in a chevron pattern.

10. A device as recited in claim 7, wherein said strain gauge is configured for measuring torque, bending, tension, or compression of said shaft.

11. A device as recited in claim 1, wherein a rechargeable source of power is mounted on said rotating shaft configured for receiving and storing charge from said energy harvesting circuit.

12. A device as recited in claim 11, wherein said rechargeable source of power comprises a battery or a capacitor.

13. A device as recited in claim 1, wherein a receiver is mounted on said rotating shaft.

14. A device as recited in claim 13, wherein said receiver comprises a transceiver.

15. A device as recited in claim 1, wherein a processor is mounted on said rotating shaft for receiving data from said sensor or data derived from said sensor.

16. A device as recited in claim 15, wherein an A/D converter is mounted on said rotating shaft for converting sensor data to digital data.

17. A device as recited in claim 16, wherein a memory device is mounted on said rotating shaft for storing said digital sensor data.

18. A device as recited in claim 17, wherein said memory is integral with or connected to said processor.

19. A device as recited in claim 17, wherein said memory contains a unique address to identify data transmitted from said memory.

20. A device as recited in claim 15, wherein said processor contains a program to process said data before transmitting.

21. A device as recited in claim 15, wherein said processor controls operation of said transmitter.

22. A device as recited in claim 15, wherein said processor is configured to calculate torque of said shaft and to calculate angular velocity or RPM of said shaft.

23. A device as recited in claim 22, wherein said processor is configured to calculate power transmitted by said shaft calculating the product of torque and RPM.

24. A device as recited in claim 22, wherein said device further comprises a data base of said torque measurements for comparing to a present measurement for detecting a change in torque.

25. A device as recited in claim 15, wherein said processor is configured to determine a change in a parameter related to said shaft, support for said shaft, a device powering said shaft, or a device powered by said shaft based on said sensor measurement.

26. A device as recited in claim 15, wherein said processor is configured to determine a change in a parameter related to said shaft, support for said shaft, a device powering said shaft, or a device powered by said shaft based on a change in torque or power of said shaft.

27. A device as recited in claim 15, wherein said device further comprises a feedback mechanism to adjust operation of said shaft based on said measurement.

28. A device as recited in claim 1, wherein said shaft is part of a machine for delivering torque.

29. A device as recited in claim 28, wherein said machine is one of a motor, a vehicle, a pump, a valve, a compressor, a polishing machine, a grinder, a lathe, or a milling machine.

30. A method of monitoring a rotating part, comprising the steps of:

a) mounting a sensor, a processor, an energy storage device, and a transmitter on a rotatable part;

b) rotating said rotatable part to provide a rotating 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, wherein said processor returns to sleep mode after said period of time;

d) sampling said sensor during said period of time; and

e) transmitting data derived from said sensor.

31. A method as recited in claim 30, wherein said rotating part comprises a shaft.

32. A method as recited in claim 31, wherein said shaft is on a machine for delivering torque.

33. A method as recited in claim 32, wherein said machine is one of a motor, a vehicle, a pump, a valve, a compressor, a polishing machine, a grinder, a lathe, or a milling machine.

34. A method as recited in claim 30, wherein said sensor comprises a temperature sensor, a strain gauge, a torque sensing device, or an accelerometer to measure rate of rotation.

35. A method as recited in claim 30, wherein said waking said processor step (c) comprises waking said processor at a frequency in the range from less than about 1 Hz to about 1 kHz.

36. A method as recited in claim 30, wherein said sampling said sensor step (d) comprises a frequency in the range from less than about 1 Hz to about 1 kHz.

37. A method as recited in claim 30, wherein said waking said processor step (c) further comprises the step of controlling power to said sensor and wherein said processor sends a signal to provide power to said sensor only during said time period.

38. A method as recited in claim 30, wherein said waking said processor step (c) further comprises the step of controlling power to said transmitter wherein said processor provides power to said transmitter only during said active mode time period.

39. A method as recited in claim 30, wherein said mounting step (a) further comprises the step of mounting sensor signal conditioning on said rotating shaft wherein said waking said processor step (c) further comprises the step of controlling power to said sensor signal conditioning wherein said processor sends a signal to provide power to said sensor signal conditioning only during said time period.

40. A method as recited in claim 39, wherein said mounting step (a) further comprises the step of 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 waking said processor step (c) further comprises the step of controlling operation of said sensor signal conditioning power supply by sending a signal to said enable pin.

41. A method as recited in claim 40, wherein said mounting step (a) further comprises the step of 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 waking said processor step (c) further comprises the step of enabling said signal conditioning power supply independently of enabling said transmitter power supply.

42. A method as recited in claim 41, wherein said mounting step (a) further comprises the step of 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 waking said processor step (c) further comprises the step of independently enabling said sensor power supply.

43. A method as recited in claim 30, wherein said waking said processor step (c) further comprises the step of computing strain of said rotating part.

44. A method as recited in claim 30, wherein said waking said processor step (c) further comprises the step of computing torque of said rotating part.

45. A method as recited in claim 30, wherein said waking said processor step (c) further comprises the step of computing angular velocity or RPM of said rotating part.

46. A method as recited in claim 30, wherein said waking said processor step (c) further comprises the step of computing instantaneous mechanical power of said rotating part.

47. A method as recited in claim 30, wherein said mounting step (a) further comprises the step of mounting a receiver or transceiver on said rotatable part.

48. A method as recited in claim 47, wherein said step (c) further comprises the step of receiving a command through said receiver or transceiver to wake up said processor.

49. A method as recited in claim 48, wherein said step (c) further comprises the step of receiving a command to log data, transmit data, or return to sleep mode.

50. A method as recited in claim 30, wherein said step (c) further comprises the step of providing power to said processor and to said transmitter to transmit data at preset time intervals.

51. A method as recited in claim 30, wherein said energy storage device comprises a battery.

52. A method as recited in claim 30, wherein said mounting step (a) further comprises the step of mounting an energy harvesting circuit on said rotatable part.

53. A method as recited in claim 52, wherein said energy harvesting circuit is connected to provide power to recharge said energy storage device.

54. A method as recited in claim 52, further comprising the step of 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.

55. A method as recited in claim 30, wherein said mounting step (a) further comprises the step of providing a circuit for measuring state of charge of said energy storage device on said rotatable part, said method further comprising the step of providing a first measurement of said state of charge of said energy storage device.

56. A method as recited in claim 55, further comprising the step of providing a second measurement of said state of charge of said energy storage device and comparing said second measurement to said first measurement to determine if charge stored in said energy storage device is depleting or charging.

57. A method as recited in claim 55, further comprising the step of 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.

58. A method as recited in claim 30, wherein said mounting step (a) further comprises the step of mounting a memory on said rotatable part.

59. A method as recited in claim 58, wherein said memory includes a unique address to identify data transmitted from said rotating shaft.

60. A method as recited in claim 58, further comprising the step of storing data derived from said sensor in said memory for transmitting by said sensor at a later time.

61. A method as recited in claim 30, further comprising the step of adjusting operation of said shaft based on said data.

62. A method as recited in claim 30, further comprising the step of providing a base station for receiving data transmitted by said transmitter and providing an output from said base station to control a machine driving said rotating shaft.

63. A method of collecting and wirelessly transmitting data, comprising the steps of:

a) providing a circuit including a sensor, a processor, an energy storage device, and a transmitter,

b) repeating the following steps in sequence to acquire a plurality of samples of data;

(1) waking said processor and drawing energy to said processor from said energy storage device to provide said processor in an active mode;

(2) taking a sample of data from said sensor while said processor is in said active mode and receiving said data in said processor; and

(3) returning said processor to sleep mode;

c) transmitting a signal derived from a plurality of said samples of data.

64. A method as recited in claim 63, wherein said sensor comprises a temperature sensor, a strain gauge, a torque sensing device, an accelerometer a pressure sensor, or a vibration sensor.

65. A method as recited in claim 63, wherein said waking said processor step (b)(1) comprises waking said processor at a frequency of about 1 Hz or about 10 Hz.

66. A method as recited in claim 63, wherein said waking said processor step (b)(1) comprises waking said processor at a frequency in the range from less than about 1 Hz to about 1 kHz.

67. A method as recited in claim 63, wherein said sampling said sensor step (b)(2) comprises a frequency in the range from less than about 1 Hz to about 1 kHz.

68. A method as recited in claim 63, wherein said waking said processor step (b)(1) further comprises the step of controlling power to said sensor and wherein said processor sends a signal to provide power to said sensor only while said processor is in said active mode.

69. A method as recited in claim 63, wherein said waking said processor step (b)(1) further comprises the step of controlling power to said transmitter wherein said processor provides power to said transmitter only while said processor is in said active mode said active mode time period.

70. A method as recited in claim 63, wherein said providing step (a) further comprises the step of providing sensor signal conditioning, wherein said waking said processor step (b)(1) further comprises the step of controlling power to said sensor signal conditioning wherein said processor sends a signal to provide power to said sensor signal conditioning only while said processor is in said active mode.

71. A method as recited in claim 70, wherein said circuit further comprises a sensor signal conditioning power supply for powering said sensor signal conditioning, wherein said sensor signal conditioning power supply comprises an enable pin, wherein said waking said processor step (b)(1) further comprises the step of controlling operation of said sensor signal conditioning power supply by sending a signal to said enable pin.

72. A method as recited in claim 71, wherein said circuit further comprises a transmitter power supply, wherein said processor has separate controls to enable said sensor signal conditioning power supply and to enable said transmitter power supply wherein said waking said processor step (b)(1) further comprises the step of enabling said signal conditioning power supply independently of enabling said transmitter power supply.

73. A method as recited in claim 72, wherein said circuit further comprises a sensor power supply, wherein said processor has an additional separate control to enable said sensor power supply wherein said waking said processor step (b)(1) further comprises the step of independently enabling said sensor power supply.

74. A method as recited in claim 63, wherein said waking said processor step (b)(1) further comprises the step of computing strain.

75. A method as recited in claim 63, wherein said circuit further comprises a receiver or transceiver.

76. A method as recited in claim 75, wherein said step (b)(1) further comprises the step of receiving a command through said receiver or transceiver to wake up said processor.

77. A method as recited in claim 76, wherein said step (b)(1) further comprises the step of receiving a command to log data, transmit data, or return to sleep mode.

78. A method as recited in claim 63, wherein said step (b)(1) further comprises the step of providing power to said processor and to said transmitter to transmit data at preset time intervals.

79. A method as recited in claim 63, wherein said energy storage device comprises a battery.

80. A method as recited in claim 63, wherein said circuit further comprises an energy harvesting circuit connected to provide power to recharge said energy storage device.

81. A method as recited in claim 63, wherein said circuit further comprises a component for measuring state of charge of said energy storage device, said method further comprising the step of providing a first measurement of said state of charge of said energy storage device.

82. A method as recited in claim 81, further comprising the step of providing a second measurement of said state of charge of said energy storage device and comparing said second measurement to said first measurement to determine if charge stored in said energy storage device is depleting or charging.

83. A method as recited in claim 81, further comprising the step of 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.

84. A method as recited in claim 63, wherein said circuit further comprises a memory connected to said processor.

85. A method as recited in claim 84, wherein said memory includes a unique address to identify data transmitted by said transmitter.

86. A method as recited in claim 84, further comprising the step of storing data derived from said sensor in said memory for transmitting by said transmitter at a later time.

87. A method as recited in claim 63, wherein said circuit is mounted on a machine, further comprising the step of adjusting operation of said machine based on said data.

88. A method as recited in claim 87, wherein said circuit further includes a receiver, said method further comprising the steps of providing a base station for receiving data transmitted by said transmitter and providing an output from said base station to said transceiver to control a machine based on said data.

89. A method as recited in claim 63, wherein said providing step (a) includes the step of providing said circuit on a moving part.

90. A method as recited in claim 89, wherein said providing step (a) includes the step of providing said circuit on a rotating part.

91. A method as recited in claim 63, wherein said circuit further comprises an energy harvesting device connected to provide charge to said energy storage device.

92. A method as recited in claim 91, further comprising the step of harvesting energy with said energy harvesting device from a motion of said device.

93. A method as recited in claim 63, wherein said circuit further includes a receiver, said method further comprising the steps of providing a base station for receiving data transmitted by said transmitter and for providing an signal from said base station to said transceiver.

94. A method as recited in claim 93, further comprising the step of providing a signal to wirelessly program an offset.

95. A method as recited in claim 93, further comprising the step of providing a signal to wirelessly program a gain.

96. A method as recited in claim 95, wherein said program includes a command to perform a shunt calibration step.

97. A method as recited in claim 95, wherein said circuit further comprises a microprocessor controlled switch and a known resistance, wherein said shunt calibration step includes throwing said microprocessor controlled switch to temporarily apply said known resistance in said circuit to simulate a known sensor signal.

98. A method as recited in claim 97, wherein said shunt calibration step further includes providing a microprocessor controlled digital trimpot to provide a desired full scale output when said known resistance is applied.

99. A method as recited in claim 93, further comprising the step of providing a signal to wirelessly program sensor offset, wherein said program includes a command to remove said offset.

100. A method as recited in claim 99, wherein said circuit further comprises an instrumentation amplifier and a second microprocessor controlled switch, said instrumentation amplifier having two sensor inputs, wherein said step of removing said offset includes the step of using said microprocessor to control said second microprocessor controlled switch to temporarily short said two sensor inputs together so as to provide equal input signals to both of said inputs to determine said offset.

101. A method as recited in claim 100, wherein said circuit further comprises a programable digital potentiometer, wherein said step of removing said offset includes the step of using said programable digital potentiometer to re-zero offset voltage of said instrumentation amplifier so that output of said instrumentation amplifier is zero while said sensor inputs are shorted.

102. A method as recited in claim 97, further comprising the step of providing RF chokes at both inputs to said instrumentation amplifier to reduce high frequency noise.

103. A method of collecting and wirelessly transmitting data, comprising the steps of:

a) providing a circuit including a sensor, a signal conditioning circuit, a processor, an energy providing device, a transmitter, and a receiver, said sensor and said signal conditioning circuit capable of being programmed to calibrate offset or to calibrate gain;

b) providing a base station for wirelessly transmitting programming commands to said receiver and for wirelessly receiving data derived from said sensor;

c) wirelessly transmitting a signal from said base station to program said offset or said gain.

104. A method as recited in claim 103, wherein said program includes a command to perform a shunt calibration step and a command to remove said sensor offset.

105. A method as recited in claim 104, wherein said circuit further comprises a first microprocessor controlled switch and a known resistance, wherein said shunt calibration step includes throwing said first microprocessor controlled switch to temporarily apply said known resistance in said circuit to simulate a known sensor signal.

106. A method as recited in claim 105, wherein said shunt calibration step further includes providing a microprocessor controlled digital trimpot to provide a desired full scale output when said known resistance is applied.

107. A method as recited in claim 104, wherein said circuit further comprises an instrumentation amplifier and a second microprocessor controlled switch, said instrumentation amplifier having two sensor inputs, wherein said step of removing said offset includes the step of using said microprocessor to control said second microprocessor controlled switch to temporarily short said two sensor inputs together so as to provide equal input signals to both of said inputs to determine said offset.

108. A method as recited in claim 107, wherein said circuit further comprises a programable digital potentiometer, wherein said step of removing said offset includes the step of using said programable digital potentiometer to re-zero offset voltage of said instrumentation amplifier so that output of said instrumentation amplifier is zero while said sensor inputs are shorted.

109. A method as recited in claim 107, further comprising the step of providing RF chokes at both inputs to said instrumentation amplifier to reduce high frequency noise.

110. A method of collecting, processing, and wirelessly transmitting data, comprising the steps of:

a) providing a circuit including a sensor, a signal conditioning circuit, a processor, an energy providing device, a transmitter, and a receiver;

b) providing a base station for wirelessly transmitting programing commands to said receiver and for wirelessly receiving data derived from said sensor; and

c) wirelessly transmitting a program from said base station to said receiver to wirelessly program operation of said microprocessor, said sensor, or said signal conditioning circuit.

111. A method as recited in claim 110, wherein said program provides instructions to acquire and log sensed data.

112. A method as recited in claim 110, wherein said program provides instructions to compare sensed data to programmable threshold levels.

113. A method as recited in claim 110, wherein said program provides instructions for reducing the amount of data transmitted.

114. A method as recited in claim 110, wherein said program provides instructions for analyzing data.