Total impedance and complex dielectric property ice detection system

• US 7,439,877 B1
• Filed: 05/18/2007
• Issued: 10/21/2008
• Est. Priority Date: 05/18/2007
• Status: Expired due to Fees

• Current Assignee: Philip Onni Jarvinen
• Original Assignee: Philip Onni Jarvinen
• Inventors: Jarvinen, Philip Onni
• Primary Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US11/804,701
• Time in Patent Office: 522 Days
• Field of Search: 340/962, 340/580, 340/581, 244/134.R
• US Class Current: 340/962
• CPC Class Codes: B64D 15/20 Means for detecting icing or initiating de-icing

Abstract

An ice detection system that detects the onset of ice accreation on an aircraft'"'"'s external surfaces, continuously measures its thickness and growth time history and provides the type of ice, glaze or rime, is disclosed along with an independent way to confirm that the contaminant is known to be ice and only ice. Total impedance data, thermal conductivity value and complex dielectric properties are used to discriminate between ice, water, deicing fluid and snow with measurements made by low cost, low power consumption, low profile, miniature electronic chips, components and devices collocated together on the external surface in a thin pliant patch that does not effect the airflow about the aircraft. The ice detection system provides ice accreation data and warning signals to displays and aural signaling devices in the cockpit for the pilot and to the control console of a ground controller flying the aircraft if it is unmanned.

Claims

1. An aircraft ice detection system employing an external, surface mounted ice sensor unit with at least two ice sensor embodiments to measure the temperature, thermal conductivity and total impedance properties of a contaminant layer overlying the ice sensor, with a thermal conductivity measured with a self-heated device and a total impedance properties measured by a collocated, miniature electronic chip that electrically excites the ice sensor over a range of test frequencies;

an Analog Devices AD5933 chip used in the embodiment, and with a collocated computer having a data storage unit and a processor;

said data storage unit containing laboratory measured ice data, contaminant properties and ice sensor measured data, said processor containing dedicated software and algorithms for processing ice sensor data to derive complex dielectric properties and a locus of a contaminant in complex dielectric space, for discriminating between ice, rain water, deicer fluid and snow and subsequently between glaze ice or rime ice overlying said ice sensor and for choosing an initial value for ice thickness, said software and algorithms also checking the icing data for signs of cracks, flaws and voids or higher electrical conductivity in said ice based on the size and the shape of said complex dielectric locus and correcting said initial ice thickness value for these effects if found, with said software and algorithms calculating the ice distribution and associated ice weight over said aircraft with said icing data along with aural warning signals transmitted to a pilot of said aircraft and to dedicated displays and to a ground controller and to dedicated displays if said aircraft is unmanned, with said ice detection system using a method to carry out ice detection and discrimination comprising;

means for exciting said ice layer on said surface of said aircraft using said external surface mounted ice sensor which underlies and is immersed in said contaminant layer by driving said ice sensor thru said frequency scan at a given input voltage,

means for using said ice sensor in at least two different embodiments;

one embodiment employing two separated parallel plates, facing each other and extending out essentially perpendicular to the aircraft'"'"'s surface and the other embodiment employing a thin, flat ice sensor of bullseye form mounted directly on the aircraft'"'"'s external surface,

means for measuring, storing and processing said total impedance data of said ice layer over said frequency scan from near zero frequency to high frequency using said miniature impedance measuring electronic chip collocated with said ice sensor,

means for measuring said thermal conductivity of said contaminant layer overlying said ice sensor using said self-heated device collocated with said ice sensor,

means for converting said total impedance measurements to said complex dielectric properties of said overlying layer by said method which relates said ice sensor physical and electrical characteristics and said impedance values to said complex dielectric characteristics,

means for using said total impedance, said complex dielectric properties and said measured thermal conductivity values to discriminate between said ice, rain water, deicing fluid or snow overlying said ice sensor,

means for determining whether said ice is glaze or rime based on said measured value of said thermal conductivity,

means for determining said thickness of said ice from said total impedance value by using said impedance value to locate appropriate laboratory measured ice properties stored in the data storage unit of said computer which is located in collocation with said ice sensor,

means for comparing a shape of said locus determined from said calculated complex dielectric properties in said complex dielectric space with a characteristic semicircular shape exhibited by said ice as the independent check that said ice is present,

means for determining whether said flaws, cracks or voids or enhanced electrical conductivity are present in said ice by examining said measured complex dielectric values in comparison with those for pure ice,

means for correcting said ice thickness choice based on said initial total impedance measurements if said flaws, cracks or voids or higher electrical conductivity are found to exist,

means for using said icing data from multiple ice sensor locations to construct the map of icing conditions occurring on said aircraft and to estimate a current weight penalty due to said icing,

whereby the onset of icing on said aircraft along with said thickness of said ice buildup with time on said aircraft is detected by said externally mounted ice sensor, employing said method which discriminates between said ice, rain water, deicer fluid and snow overlying the ice sensor as well as discriminating between said glaze ice and rime ice based on following a series of procedures that make use of measurements of the properties of said contaminant layer overlying said ice sensor in comparison with said physical properties and said complex dielectric properties known for said ice and for said possible contaminants.

2. The aircraft ice detection system method recited in claim 1 further comprising:

sending said icing data and said aural warning signals to said aircraft'"'"'s pilot and to the pilot'"'"'s display or to said unmanned aircraft'"'"'s ground controller and to said ground controller'"'"'s display to continuously alert them as to the aircraft'"'"'s icing status and to also alert them if said ice thickness exceeds a pre-specified amount causing a dangerous condition to exist as well as sending said icing data to said aircraft'"'"'s deicing system, if desired.

3. Apparatus for continuously measuring the onset, thickness, and buildup of ice thickness with time of ice on an external surface of an aircraft with the following collocated components;

an external surface mounted ice sensor, a temperature measuring device, a thermal conductivity measuring device, and a total impedance measuring device in the form of a miniature electronic device comprising an Analog Devices AD5933 type chip, the aircraft'"'"'s electrical power supply, electrical, control and data wire runs, a power converter, a computer with a data storage unit and a processor;

said data storage unit containing laboratory measured and pre-stored ice data and equivalent data for possible contaminants, said processor containing program software and data reduction algorithms, with transceiver units used for system control signal and data transmission if a wireless communication approach is chosen, with all the elements of said ice detection apparatus selected from a class of miniature or micro-miniature, low power consumption, low profile electronic components and collocated together in a thin, pliable patch of minor vertical height, with visual and aural warning signals communicated to alert the pilot of the said aircraft, said apparatus comprising;

said surface mounted ice sensor attached externally to said aircraft,

means for electrically exciting said ice sensor and an overlying contaminant layer with a frequency scan from near zero frequency to high frequency at a selected voltage,

means for measuring said total impedance of an overlying layer during said near zero frequency to high frequency sweep,

means for measuring a thermal conductivity of said overlying layer,

means for storing and processing measured impedance data and thermal conductivity values,

means for storing said laboratory measured ice data including total impedance versus said excitation frequency at multiple temperatures and also storing ice dielectric relaxation times,

means for converting said impedance scan measurements into complex dielectric properties of said overlying layer,

means for discriminating between said overlying layers of said ice, rain water, deicing fluid, or snow,

means for comparing said impedance data and said thermal conductivity values with those characteristic of said laboratory ice data to determine an initial choice for said thickness of said ice,

means for comparing complex dielectric properties with those characteristic of said ice, wherein said ice is known to exhibit a semicircular shaped locus in complex dielectric space as a function of said excitation frequency,

means for determining whether flaws, cracks or voids or higher electrical conductivity are present in said ice layer,

means to modify initially chosen ice thickness value for the presence of said flaws, cracks, or voids or higher electrical conductivity, if present,

means to transmit said icing status data and said warning signals to said pilot or to a ground controller or said icing data to the deicing system, if desired,

whereby said apparatus for detecting the onset of said icing on said aircraft and for continuously measuring said ice thickness, and said buildup of ice thickness with time is mounted in a thin, pliable patch to ease installation by allowing the option of gluing said patch directly to said aircraft'"'"'s surface and with minor vertical height such that the presence of said patch does not interfere with said airflow around said aircraft or the airflow over said ice sensor, and the required measurements for the properties of said overlying layer, including said temperature, said thermal conductivity, said total impedance and said complex dielectric properties made with said ice sensor system whose components are all collocated together and constructed with miniature size, low profile shaped and economical chips, devices and components.

4. The apparatus recited in claim 3 wherein one embodiment for said ice sensor is a configuration employing two planar electrode plates spaced apart, facing each other and extending outward in a nearly vertical direction from the external surface.

5. The apparatus recited in claim 3 wherein the embodiment for said miniature impedance measuring electronic chip, that excites said contaminant layer overlying said ice sensor, is said Analog Devices electronic chip, AD5933, a 1 MSPS, 12-Bit Impedance Converter Network Analyzer of miniature size collocated physically with and electrically connected to said ice sensor.

6. The apparatus recited in claim 3 wherein the embodiments for said thermal conductivity and said temperature measuring devices are thermistors that employ glass encapsulated thermistors and which are collocated with said ice sensor and said impedance chip.

7. The apparatus recited in claim 6 wherein said processor is collocated with said ice sensor, said impedance chip, and said thermistor pair and used to store said impedance and said thermistor data, process same, and chose an initial value for said ice thickness.

8. The apparatus recited in claim 3 wherein the method described in “

Ice Physics”

, Reference 7, by P. V. Hobbs, Clarendon Press, Oxford, 1974, and in particular the equations on pages 82 thru 85 of that reference, equations numbered (2.2) thru (2.12), is used or a similar development is used to convert said impedance data to said complex dielectric values over said frequency scan.

9. The apparatus recited in claim 3 wherein said ice is confirmed if said complex dielectric property locus in said complex dielectric space with varying frequency is of said semicircular shape;

the characteristic shape of said ice.

10. The apparatus recited in claim 3 wherein said ice is also confirmed when a vector from approximately a quarter diameter point on a horizontal axis at a high frequency end of said semicircular locus, to a point on the opposite side of the locus corresponding to a pre-selected lower excitation frequency, is found to have approximately the same vector magnitude and inclination angle as a similar vector calculated from said stored laboratory measured ice data while keeping the product of said excitation frequency and the dielectric relation time constant the same for both points on the low frequency side of said locus.

11. The apparatus recited in claim 3 wherein the presence of said flaws, cracks or voids or higher electrical conductivity is determined from the magnitude of a diameter of said complex dielectric semicircular locus in said complex dielectric space in comparison to said diameter for pure ice.

12. The apparatus recited in claim 3 wherein said initial value chosen for said ice thickness based on said measured total impedance value is corrected for the effects of said flaws, cracks or voids or higher electrical conductivity if said effects are found.

13. The apparatus recited in claim 3 wherein a second embodiment for said ice sensor is a surface mounted, flush bullseye geometry sensor with a central circular area electrode surrounded by a second ring electrode of radial width.

14. The apparatus recited in claim 3 wherein a similar development, following the method in “

Ice Physics”

, by P. V. Hobbs, Clarendon Press, Oxford, 1974, pages 82 thru 85, equations (2.2) thru (2.12), for said ice sensor employing parallel electrode plates, is used or a similar development used to relate physical and electrical characteristics of said bullseye type ice sensor to its said complex dielectric values;

in order to identify the presence of said ice.

15. The apparatus recited in claim 3 wherein all elements of said ice detection system are collocated together in a thin pliable patch of diminished area that is mounted anywhere on said aircraft and does not effect the drag of said aircraft or a flowfield about said aircraft.

16. An aircraft ice detection system located on an external surface of an aircraft for measuring an onset of icing on said aircraft which continuously measures an ice thickness, an ice thickness buildup with time and an type of ice, glaze or rime, and which also provides several independent ways to confirm the presence of said ice, said system utilizing a combination of means to accomplish these results, a combination of selected parameters and measurements including temperature, thermal conductivity and said total impedance of a contaminant layer overlying said external ice sensor, the use of said measurements along with derived complex dielectric properties of said containment layer to discriminate between ice, rain water, deicer fluid and snow and then between glaze ice and rime ice lying over said ice sensor, software and algorithms providing methods to operate on said measurements, compare said measured results with laboratory measured ice data stored in a computer, a data storage unit and a processor combination collocated with said computer and said ice sensor and to select said ice, if present, from among possible contaminants, and by comparing a complex dielectric locus with that for said ice to provide an independent confirmation of said ice presence, also employing the size of a locus diameter in comparison to that of pure ice to discriminate between cracks, flaws and voids or higher electrical conductivity and the use of this result to correct an initially chosen ice thickness value for these effects, said ice detection system also using a unique combination of low power consumption, miniature size components with characteristic small footprints and reduced heights allowing all parts of said aircraft ice detection system to be collocated together, said system comprising:

means for detecting said onset of icing on said aircraft'"'"'s external surfaces using an overlying layer'"'"'s temperature, said thermal conductivity measurements, and said total impedance measurement values and the said derived complex dielectric properties,

means for discriminating between said ice, rain water, deicing fluid or snow overlying said external surface mounted ice sensor,

means for determining whether said ice is said glaze or rime,

means for continuously determining said ice thickness and an ice thickness growth time history from said total impedance measurements of said overlying ice layer,

means for independently confirming that said contaminant layer is said ice based on said complex dielectric properties determined from converting frequency scanned total impedance data,

means which allow said collocation of said ice sensor, an impedance measuring electronic chip, a self-heated thermistor, a local temperature measuring thermistor, said computer, said data storage unit, said processor, said ice status and said data transfer and communication units and all other supporting equipment in a thin, pliant patch attached to said aircraft'"'"'s external surface,

means for communicating said ice status data and said warning signals to a pilot or to a ground controller of an unmanned aircraft.

17. The system recited in claim 16 wherein said embodiments for said ice sensor include a parallel plate or nearly parallel plate configurations which project out from the aircraft surface and a surface mounted, flush bullseye type configurations.

18. The system recited in claim 16 wherein said variable frequency, miniature electronic chip collocated with said ice sensor is used to measure said overlying layer total impedance data, store said data and process same;

said embodiment of said impedance measuring chip being an Analog Devices electronic chip AD 5933.

19. The system recited in claim 16 wherein said method described in “

Ice Physics”

, by P. V. Hobbs, Clarendon Press, Oxford, 1974, pages 82 thru 85, said equations (2.2) thru (2.12), is used or a similar development is used to calculate said complex dielectric properties of said overlying layer for a parallel plate type ice sensor and a modified version for a bullseye type ice sensor.

20. The system recited in claim 16 wherein said laboratory data measured by R. P. Auty, for said complex dielectric properties of said glaze ice and for said glaze ice dielectric relaxation times, and other similar data, are stored in said processor and used as a basis for comparison to newly measured data, in particular the stored data includes the data summarized in the Table II, page 33, temperature t=−

10.6 C, the Table III, page 35, t=−

0.1 C thru −

65.8 C, and in the Appendix V, pages 47 thru 51, at temperatures of −

1.5 C, −

16.3 C, −

27.5 C, −

37.6 C, −

50.6 C and −

65.6 C respectively and the use of the procedure and the technique of J. W. Valvano, for the determination of said thermal conductivity of said overlying contaminant layer, in particular the following equation;

$K_{\mathrm{eff}}=\frac{1}{\frac{3<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>T}{\mathrm{\Gamma <br><br>}<br><br><br><br>a^2}-\frac{1}{5<br><br><br><br>K_b}},$

where K_eff is the thermal conductivity, Δ

T is the volume averaged temperature increase in degrees Celsius, Γ

is the steady-state volume power in watts/milliliter, a is the radius of the thermistor bead, and K_b is the thermal conductivity of a self-heated thermistor bead.