System and method for a surface strain gauge

• US 9,618,420 B2
• Filed: 04/12/2011
• Issued: 04/11/2017
• Est. Priority Date: 04/19/2010
• Status: Expired due to Fees

• Current Assignee: Single Wing Energy OY
• Original Assignee: Philip Wesby
• Inventors: Wesby, Philip, Turner, Christopher
• Primary Examiner(s): Barbee, Manuel L
• Application Number:
  US13/641,581
• Publication Number:
  US 20130035878A1
• Time in Patent Office: 2,191 Days
• CPC Class Codes: F03D 17/00 Monitoring or testing of wind motors, e.g. diagnostics testing during commissioning of wind motors F03D13/30
• CPC Class Codes: F03D 7/042 by means of an electrical or electronic controller
• CPC Class Codes: F05B 2270/331 Mechanical loads
• CPC Class Codes: F05B 2270/332 Maximum loads or fatigue criteria
• CPC Class Codes: F05B 2270/808 Strain gauges; Load cells
• CPC Class Codes: G01M 5/0016 of aircraft wings or blades
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0083 by measuring variation of impedance, e.g. resistance, capacitance, induction
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A system and method for a surface strain gauge is described which has direct application to wind turbine structures and wind turbine blades and wind turbine struts. The invention is equally applicable to other airfoil structures such as aircraft wings and aircraft fuselages. The strain gauge comprises an array of carbon fiber material integrated with one or more microcontroller modules wherein the entire array may be incorporated into the surface of the structure to be monitored during manufacture of the structure. The array comprises separate sheets of carbon fiber reinforced epoxy which are linked together and which each comprise a separately addressable element such as a microcontroller wherein the microcontrollers are connected to a power supply and to a central bus which itself links to a central system controller. Differential measurements of the resistance of separate carbon fiber reinforced epoxy sheets may be determined in real time as well as the resistance between two or more sheets. In this way real time dynamic load monitoring can be performed and compared with original values determined at time of manufacture to provide data on fatigue of the structure with time before damage and failure occurs.

Claims

1. A smart surface strain gauge comprising:

a material having electrical resistance-changing properties, changing reversibly with tension or compression,

wherein the material comprises an array of at least one sheet or fiber element connected to at least one other sheet or fiber element, each separate sheet or fiber element comprising one or more control points;

at least one microcontroller, the one or more control points integrated with the at least one microcontroller, the at least one microcontroller configured to measure any change in resistance at the one or more control points, the at least one microcontroller further configured to be separately addressable;

a power supply connected to the microcontroller; and

a central data communication link connected to the microcontroller,

the at least one separately addressable microcontroller configured to communicate with at least one system controller over the central data communication link,

the said system controller configured to process data received from each microcontroller and compute the strain on part or all of the total structure, or the rate of development of fatigue of part or all of said total structure.

2. A smart surface strain gauge according to claim 1 wherein the said sheet or fiber element is formed of carbon fiber reinforced epoxy or carbon fiber reinforced epoxy matrix composite.

3. A smart surface strain gauge according to claim 2 further comprising

a plurality of said separate carbon fiber reinforced epoxy sheets or fiber elements each comprising at least one measurement point, and the at least one microcontroller, wherein

each of said sheets and or fiber elements being associated with the at least one microcontroller configured to perform resistance measurements, wherein said at least one microcontroller further connected to said power supply and said communication link for sending and or receiving data from said system controller, and

said system controller being remote from the structure, and said communication link sending and receiving communications to said system controller from a wireless communications circuit.

4. A smart surface strain gauge according to claim 3 further comprising an arrangement of said carbon fiber reinforced epoxy sheets or fiber elements wherein a single sheet element further comprising:

two of the said microcontrollers each configured to be connected to a sheet element via one or more connections respectively wherein

each of said two microcontrollers being connected to at least one measurement point for performing resistance measurements, and

each of said two microcontrollers being connected to said communications link via at least one connection and

each of said two microcontrollers being connected to said power supply by at least one connection.

5. A smart surface strain gauge according to claim 2 further comprising

a plurality of said separate carbon fiber reinforced epoxy sheets or fiber elements each comprising at least one measurement point, and said at least one microcontroller, wherein

each of said sheets and or fiber elements being associated with the at least one microcontroller configured to perform resistance measurements, wherein said at least one microcontroller further connected to said power supply and said communication link for sending and receiving data from said system controller, and

said system controller being integrated with the said structure and being integrated with the said power supply and the said communications link.

6. A smart surface strain gauge according to claim 5 further comprising an arrangement of said carbon fiber reinforced epoxy sheets or fiber elements wherein a single sheet element further comprising:

two of the said microcontrollers each configured to be connected to a sheet element via one or more connections respectively wherein

each of said two microcontrollers being connected to at least one measurement point for performing resistance measurements, and

each of said two microcontrollers being connected to said communications link via at least one connection and

each of said two microcontrollers being connected to said power supply by at least one connection.

7. A smart surface strain gauge according to claim 2 further comprising an arrangement of said carbon fiber reinforced epoxy sheets or fiber elements, said arrangement being integrated into the blade of a wind turbine, and wherein

said blade sheets or blade fiber elements being organized into an arrangement of alternating arrays between the front and back outer surfaces of said blade,

wherein each arrangement being controlled by one or more of said separately addressable microcontrollers, and

the said at least one system controller processing the data received from said separately addressable microcontrollers.

8. A smart surface strain gauge according to claim 7 further comprising an arrangement of said carbon fiber reinforced epoxy sheets and or fiber elements wherein

said microcontrollers are linked by a communication link and power supply, and wherein said communication link and power supply are configured to send data comprising communication of power and data signals, and wherein

said microcontrollers being linked to a radio communications circuit for communicating with the said at least one system controller via a radio link or via a fixed line link wherein,

said system controller configured to process the received surface strain gauge data and send control signals to change the power generated by the wind turbine as a function of the measured readings, or send control signals to activate a brake to slow or stop the rotation of the wind turbine as a function of the measured readings.

9. A smart surface strain gauge according to claim 7 wherein a dynamic load on part or all of the structure causes a change in resistance of at least one of said arrangement of sheets or fiber elements and said microcontrollers measuring dynamic load data, wherein

the two alternating sheet arrays and or fiber element arrays configured to provide data of the loading on said blade at points where the strain changing from compression to tension, wherein

the changes in resistance determined by one array will be opposite in sense to that determined by the other, and wherein

said resistance of each of said sheet arrays and or fiber element arrays being determined by the microcontroller configured to compute the resistance across different measurement points in said sheet or fiber element or across a plurality of said sheets or fiber elements in order to detect absolute resistance increases indicating fiber breakage and cumulative damage by at least one selected from the group consisting of:

differential resistance measurement, absolute resistance measurement, and comparison resistance measurement.

10. A smart surface strain gauge according to claim 9 wherein each of said microcontrollers being configured to compare said resistance of each separate array of sheets and/or fiber elements by subtraction or ratio in a bridge circuit so that the strain-induced resistance change can be separated from temperature or other causes of resistance change.

11. A smart surface strain gauge according to claim 7 wherein

said system controller further comprising a control algorithm using a fuzzy logic self-learning strategy as a function of at least one of the measured parameters selected from the group consisting of:

wind speed, turbine rotational speed, tip speed ratio, temperature, variations in wind power, and wind direction.

12. A smart surface strain gauge according to claim 11 wherein said measured parameters are determined by sensors on the turbine and based, at least in part, on other operational characteristics of said turbine, wherein

said self-learning algorithm is configured to direct its load-monitoring strategy to investigate parts of the structure most under load with higher frequency, wherein reference resistance values of said sheet arrays and or fiber element arrays determined when manufactured or at a time prior to use provide a baseline to determine the rate of development of fatigue of said structure with time, the smart surface strain gauge further comprising:

said system controller configured to (1) determine the prevailing environmental conditions and (2) implement the optimum load-monitoring strategy in order to monitor the structure effectively.

13. A smart surface strain gauge according to claim 1 wherein said communication link and power supply is integrated with the surface of the structure.

14. A smart surface strain gauge according to claim 1 wherein fatigue of part or all of said total structure is determined by monitoring permanent changes of resistance.

15. A smart surface strain gauge according to claim 1 wherein each separately addressable microcontroller is configured to (1) monitor the stress and strain on a structure under dynamic load, (2) measure the change in resistance of each of said sheet or fiber elements in real time, and (3) compare said measurement data with stored data values.

16. A smart surface strain gauge according to claim 15 wherein said stored data values is at least one selected from the group consisting of reference data measured at time of manufacture of the structure, and reference data measured at a time before the structure is under dynamic load.

17. A smart surface strain gauge according to claim 1, wherein said system controller is further configured to monitor at least one selected from the group consisting of:

the integrity of the structure, dynamic loading of the structure, surface deformation of the structure, onset of fatigue of the structure, and a change in the surface of a pressurized structure,

and wherein said structure being at least one selected from the group consisting of;

a building, a bridge, an aircraft wing, an aircraft fuselage, an aircraft propeller, a helicopter rotor, a wind turbine structure, a wind turbine blade, a wind turbine strut, a motor vehicle body, a fuel tanker vehicle, a boat hull, a marine vessel, a ship hull, an oil tanker, a musical instrument, a support and control structure, a tool, a prosthetic joint, a prosthetic limb, a prosthetic hand, and a synthetic heart valve.

18. A smart surface strain gauge as disclosed according to claim 17 wherein the structure comprises a high surface density of resistance measurement points thereby providing a capability to capture and transmit sounds wherein the dynamically changing resistance measurements are transmitted by a communications link to an amplifier and loudspeaker where the sounds can be generated.

19. A smart surface strain gauge according to claim 17 wherein the structure is a musical instrument and the resistance measurements are linked to data related to the deformation of the instrument wherein the vibration of the said instrument can be tuned correctly, the vibration of the instrument structure, caused when a string is vibrated or when a woodwind instrument is blown, causes a deformation of the instrument body and a corresponding change in resistance in the surface strain gauge which is measured and processed by the system controller.

20. A smart surface strain gauge according to claim 19, which is further configured to be linked to:

a visible means being an arrangement of one or more selected from the group consisting of same color LEDs, changing color LEDs, and varying intensity LEDs, the said LED arrangement indicating when the resistance measurements get close to or match the signature resistance corresponding to one or more musical note frequencies for that instrument thereby providing a means to tune the said musical instrument.

21. A smart surface strain gauge according to claim 19, which is further configured to be linked to:

an audible means of varying pitch wherein, the said audible means indicating when the resistance measurements get close to or match the signature resistance corresponding to one or more musical note frequencies for that instrument thereby providing a means to tune the said musical instrument.

22. A smart surface strain gauge according to claim 1, wherein said communication link and power supply are integrated into a communication and power bus, wherein power is transmitted to the microcontrollers over the same link which carries the data.