JP2012507660A - System and method for measuring holdings in filters - Google Patents

Abstract

Disclosed is a system and method for determining clogging of a filter having a first dielectric constant using materials having different dielectric constants. The filter is contained in a metal container that forms a microwave cavity, and microwave or RF energy is created in the cavity, and changes in the cavity microwave response are monitored. Changes in the cavity microwave response are associated with filter clogging. In a preferred embodiment, the microwave energy includes multiple cavity modes, thereby allowing determination of the spatial distribution of contaminant clogging. In one embodiment, the microwave cavity response includes a frequency shift of the resonant mode. Alternatively, the microwave cavity response includes a shift in the quality factor Q of the resonant mode. The microwave cavity response may include a shift in the amplitude or peak width of the microwave signal at resonance.

Description

(Cross-reference of related applications)
This application is a continuation-in-part of U.S. Provisional Patent Application No. 11 / 741,832 (filed April 30, 2007). This application is U.S. Provisional Patent Application No. 60 / 746,081 (May 2006). The disclosures of these applications are hereby incorporated by reference in their entirety.

  This application claims the benefit of US Provisional Patent Application No. 61 / 110,965 (filed Nov. 3, 2008), the disclosure of which is incorporated herein by reference in its entirety.

(Field of Invention)
The present invention relates to the determination of contaminant loading on a filter, and more particularly to the use of radio frequency to determine clogging.

  In many areas, there is a need for accurate detection of the amount of material captured by a filter. As an example, it is necessary to determine clogging such as air filters for HVAC systems, filter bag housings used in industrial applications, and filters used with liquids.

  As another example, it is necessary to determine filter clogging of soot on the particulate filter. The amount of clogging on the particulate filter must be recognized in order to determine the appropriate conditions for activation of regeneration as well as monitoring conditions to determine when full regeneration has been achieved. The level of clogging is important in this situation because regeneration of particulate filters often undergoes an uncontrolled incineration where soot is ignited by the presence of free oxygen and combustion waves are generated through the filter. Under certain circumstances, regeneration can produce very high temperatures, which can limit the fatigue life of the filter and ultimately cause large thermal stresses that can lead to its failure. Thus, the level of clogging is important for successful filter regeneration.

  A particular application for particulate filters is diesel particulate filters (DPF). Currently, filter pressure drop measurements are used to evaluate the amount of soot accumulated in the DPF. Also, in some cases, predictive models can be used to assess filter clogging. Pressure drop measurements alone only provide an indirect and inaccurate measurement of particulate filter soot accumulation and have several drawbacks. Exhaust gas composition, temperature, and flow rate all affect the filter pressure drop and must be considered to accurately correlate the pressure drop with filter clogging. Furthermore, the spatial distribution of accumulated ash and soot also affects the pressure drop measurement, which may change over time, especially as the filter becomes clogged with ash.

  After repeated regeneration, a substantial amount of ash may also accumulate in the particulate filter. The pressure drop measurement cannot distinguish between filter soot accumulation and ash accumulation, the latter introducing further errors in the assessment of soot clogging based on pressure drop. In addition, various types of filters exhibit non-linear pressure drop response and pressure drop history phenomena, depending on the filter clogging condition and history, which makes pressure-based filter clogging measurements more difficult.

  A pressure drop based assessment of soot accumulation in the DPF is also characterized by a generally slow response time and low sensitivity to slight changes in soot clogging. In addition, because these systems are unable to directly monitor the ash level in the filter, the filter needs to be inspected periodically, regardless of the actual ash level of the filter, regardless of the vehicle or Introduces machine downtime. In addition, pressure drop based measurements cannot be detected except for the worst filter failure, and in most cases cannot meet stringent on-board diagnostic requirements.

  In order to address some of the disadvantages associated with filter pressure drop measurements, various predictive models are commonly used with these measurements. There are a wide variety of models, many of which require several engine operating parameters, input from various engine and exhaust sensors, and time between regeneration events to predict the amount of soot accumulated in the DPF. Is used. In many cases, these models are uploaded to an engine control unit (ECU). These models are generally calibrated for specific engines and fuels and require recalibration for each specific application. Moreover, when used with a cleaner burning fuel (as compared to the fuel where the model was originally calibrated), the model tends to overestimate filter clogging and is unnecessary. This results in filter regeneration and fuel economy penalty. The combined use of predictive models and filter pressure drop measurements has little effect on overcoming the drawbacks listed above. These disadvantages lead to inefficient system operation, fuel economy penalty, increased filter heat circulation and fatigue, and reduced filter life.

  In addition, exhaust gas soot sensors have been proposed to directly measure the concentration of soot aerosol in the exhaust gas entering the particulate filter. Because these measurement systems may produce some level of passive regeneration, depending on the exhaust conditions, the amount of soot accumulated on the particulate filter is not necessarily equal to the amount of soot entering the filter. There is a drawback. Further, the exhaust gas soot sensor does not provide any information regarding ash accumulation or soot and ash distribution within the DPF. In addition, many of these sensors suffer from soot contamination, which consumes excessive amounts of energy and is prone to errors introduced by exhaust temperature, exhaust gas viscosity, and other factors.

  Radio frequency (RF) based particulate clogging monitoring systems have also been proposed. One such system monitors filter clogging and initiates filter regeneration based on the magnitude of a low frequency (RF) signal transmitted through the filter. This system has the advantage over utilizing the high frequencies required to create multiple cavity resonance modes by limiting its use to low frequencies below that required to establish resonance in the cavity Miss a lot of.

  It has also been proposed to use microwaves to detect soot content components in particulate traps. One such system detects soot content components in the particulate filter by monitoring changes in the filter resonant frequency. However, such a system cannot determine the spatial distribution of soot content components within the particulate filter.

  All known RF and microwave filter clogging monitoring systems have several drawbacks:

  (A) Prior art systems are unable to monitor the spatial distribution of material accumulated in the filter. The accumulation of ash in the filter displaces the soot and changes its distribution. Furthermore, non-uniform flow conditions can also result in non-uniform material accumulation.

  (B) All known filter clogging monitoring systems initiate filter regeneration based on some average filter clogging total. Locally high soot clogging cannot be detected by systems that are unable to measure the material distribution in the filter.

  (C) Previous microwave and RF-based filter clogging systems cannot simultaneously detect both soot and ash accumulation in the filter under all exhaust conditions.

  (D) These systems do not detect filter failures or malfunctions that are important to ensure that the filter operates as needed.

  (E) These systems do not detect malfunction or failure of individual components such as sensors, which may be required for correct operation of the filter.

  (F) Microwave and RF based measurement systems are affected by humidity and water vapor present in the exhaust gas and on the filters, which must be considered to reduce measurement errors.

  (G) Conventional filter clogging monitoring systems are designed to provide existing engine and exhaust to provide feedback control functions that are useful in modifying engine operation to optimize the performance of combined engines and aftertreatment systems. Communication with the sensor has not been achieved.

  Therefore, it would be beneficial if there was a filter clogging measurement system that addresses the above problems. Such a system would be advantageous in that lower emission limits may be achieved while minimizing the amount of maintenance and unnecessary regeneration cycles. In addition, the use of multiple resonance modes will allow for a more detailed assessment of clogs specific to the device.

  In addition to particulate filters, the filter clogging measurement system can be applied to a wide range of filters, including fiber filters, various porous media used for filtration, and the like. In one embodiment, in an air filter used in an HVAC system, determining the filter clogging condition is important in determining when to clean or replace the filter. Similarly, bag filters are often cleaned by backflow, and it is important here to determine when to clean the filter based on the condition of filter clogging.

  Disclosed is a system and method for determining clogging of a filter having a first dielectric constant using materials having different dielectric constants. The filter is contained in a metal container that forms a microwave cavity, and microwave or RF energy is created in the cavity, and changes in the cavity microwave response are monitored. Changes in the cavity microwave response are associated with filter clogging. In a preferred embodiment, the microwave energy includes multiple cavity modes, thereby allowing determination of the spatial distribution of contaminant clogging.

  In one embodiment, the microwave cavity response includes a frequency shift of the resonant mode. Alternatively, the microwave cavity response includes a shift in the quality factor Q of the resonant mode. The microwave cavity response may include a shift in the amplitude or peak width of the microwave signal at resonance.

  At least one antenna may be used to transmit / receive microwave energy. In one embodiment, only one antenna is used in reflective mode to transmit / receive microwave energy. Two antennas may be used in transmission mode, with one antenna transmitting and the other receiving. Instead of an antenna, at least one waveguide may be used to transmit / receive microwave energy. In one embodiment, one waveguide is used in reflection mode to transmit / receive microwave energy. Alternatively, two waveguides may be used in the transmission mode, with one waveguide transmitting and the other waveguide receiving.

  In another embodiment, the filter is a diesel exhaust particulate trap for removing particulate matter from diesel engine exhaust. The particulate material may be a soot. Note that the filter can be any filter and the particulate matter can be any contaminant collected on the filter.

  In yet another embodiment, the metal container includes a cylindrical portion between two transition cones, one of which is connected to the exhaust pipe. The microwave energy may be in any range of frequencies, but may be in the S band. Suitable materials include in particular cordierite and silicon carbide. Both low and high order cavity modes may be used to monitor filter clogging. In this embodiment, the frequency of operation may be selected so that the mode operates at cut-off in a narrow area of the filter inlet and outlet.

  If two antennas or waveguides are used, they may be placed on opposite sides of the filter or on the same side of the filter. In one embodiment, the antenna and waveguide may be placed downstream of the filter to prevent contamination.

  Microwave energy may be provided by a modified microwave chip, which may be monitored by a diode with or without amplification. Cavity monitoring may use lock-in detection and / or homodyne detection, or heterodyne detection.

FIG. 1 is a perspective view of a basic diesel particulate filter according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of another embodiment of the present invention. FIG. 3 is a diagram of a microwave filter measurement system, according to one embodiment. FIG. 4 is a diagram of a microwave filter measurement system according to another embodiment. FIG. 5 is a graph of S21 (transmission) determined experimentally as a function of frequency. FIG. 6 is a graph of the S11 (reflection) response experimentally determined as a function of frequency. FIG. 7 is a graph showing an enlarged view of the transmission mode of FIG. FIG. 8 is a graph showing sensor output as a function of filter clogging. FIG. 9 is a diagram showing how different resonance modes result in high electric field strengths in different regions within the filter. FIG. 10 is a graph showing responses of a plurality of filter resonance modes to a non-uniform wrinkle distribution. FIG. 11 is a graph showing sensor output for wrinkle distribution of different filters as a function of filter clogging. FIG. 12 is a graph showing the response of the microwave signal to ash accumulation in the filter. FIG. 13 is a graph showing the response of a microwave signal to a filter failure.

  The present invention is based on the recognition that microwaves can be used to determine the status of trap or filter clogging. The clogging may be soot, particulates, ash, or any solid / liquid. In addition to determining the total amount of clogging, the microwave system described herein is useful in determining the distribution of clogging across the filter. The microwave detection used in the present invention can be inexpensive because inexpensive oscillators and detectors within the frequency range of interest are commercially available.

  In the case of diesel particulate filters, the particulates are made from soot and other organic compounds (solid and / or liquid) and ash. For the purposes of this disclosure, composites of carbon and organic compounds are referred to as cocoons for simplicity. One skilled in the art recognizes that soot and organic compounds are removed through regeneration, but ash clogging remains.

  In addition, although this disclosure refers to a diesel particulate filter, it should be noted that the filter can be any type of filter. Further, the material clogging of the filter need not be soot or ash, but can be any material with different dielectric properties than the medium it replaces.

In one embodiment, the diesel particulate filter unit is made from cordierite having a dielectric constant slightly higher than 4 at frequencies near the S band. This material has a small temperature dependence. The presence of soot (in some cases, up to 10 g / liter is possible for the trap, and the trap size is about 2 liters for a 5.66 inch trap) changes the microwave characteristics of the microwave cavity. For this reason, the maximum clogging of the trap can be up to 20 g with a volume of about 20 cm ³ . This amount of wrinkles corresponds to a substantial change in substantial volume and trap dielectric characteristics. Note that the dielectric constant of 煤 is approximately 2.

  Silicon carbide is also suitable for the production of diesel particulate filters. The microwave properties of silicon carbide also favor the use of microwaves for clogging detection. Those skilled in the art will know that the microwave clogging detection techniques disclosed herein determine clogging of fiber filters (organic and inorganic fibers) such as those used in, for example, bag housings, and non-uniform dielectrics. It will be appreciated that in other applications where a substantial mass / volume of material with a rate can be collected.

  In addition, although the term “microwave” is used throughout this disclosure, the methods and apparatus disclosed herein may be equally applicable to energy in other frequency bands. For example, RF band energy may also be used to test for clogging.

  Ash components that are not removed through regeneration can be monitored to see if substantial amounts of ash accumulate on the trap over time.

  Low and high order cavity modes can be used to monitor trap clogging and the spatial distribution of collected material. Different cavity modes have different electric field patterns with peaks and nulls that vary throughout the volume. For a given cavity mode, only the presence of soot in the region with the high electric field affects the microwave in the cavity. By selecting different modes within the cavity, it is possible to sample different regions and thus obtain information about the wrinkle distribution.

  The presence of soot affects the cavity response in several ways. The resonant frequency shifts to a lower frequency with soot accumulation. In addition, the cavity quality Q is affected by the presence of absorption soot. Furthermore, the amplitude of the signal at resonance decreases with the accumulation of soot. All three of these parameters can be used to determine the wrinkle level. Several modes can be used to monitor clogging in various areas of the diesel particulate filter.

  The present invention will now be described with reference to the drawings. Referring to FIG. 1, the diesel particulate filter unit 10 includes a cylindrical portion 12 made of metal and transition cones 14 and 16. The cone 14 is connected to the exhaust pipe 18. In this embodiment, the pair of rod antennas 20 and 22 are disposed on the opposite side of the filter 24.

  Because of the conical transition sections 14 and 16, the frequency of operation can be selected so that the mode operates with a cut-off in a narrow region of the trap inlet and outlet, the mode being less than the cut-off in the main exhaust 18 It is the frequency which operates with. It is not necessary to provide a screen to limit microwave radiation.

  In the embodiment of FIG. 1, one of the conventional rod antennas 20 and 22 functions as a transmitter and the other functions as a receiver. It should be understood that both rod antennas 20 and 22 may be located on the same side rather than sandwiching the filter 24. In this case, the preferred location of the rods 20 and 22 would be downstream of the filter element 24 to minimize wrinkles on the surface of the transmitter, receiver or related component.

  Referring now to FIG. 2, it is possible to implement a transmitter through the use of a loop antenna 26 or through the use of a waveguide 28. The waveguide 28 may be filled with a highly inductive material. It is also contemplated to use loop antenna 26 and / or waveguide 28 to monitor radiation by functioning as a receiving antenna.

  It is possible to use a single antenna (rod or loop) and a single waveguide, or two antennas or waveguides. In the case of a single antenna / waveguide, the information is in the reflected signal. In the case of a separate antenna / waveguide for the transmitter / receiver, it is possible to choose between reflection or transmission modes. For two antennas / waveguides, the coupling matrix that can be used to determine clogging is transmission from one antenna / waveguide to the other, and vice versa, and for each antenna / waveguide There are four elements of reflection inside.

  As shown in FIG. 2, one suitable location for the transmitter and / or receiver is in the central region of the filter 24. This location represents a distinct advantage of the microwave system disclosed herein, as the wave penetrates the outer surface of the filter 24, and thus the outer wall of the filter 24 can protect the sensor from sputum deposition. . This arrangement can be performed for either single or two waveguides, loop antennas, or rod antennas.

  One embodiment of a system for transmitting and receiving microwave energy through a filter 24 and processing the received signal is shown in FIG. The filter 24 is contained inside a filter housing 32 that forms a microwave resonant cavity, and forms the particulate filter unit 10. The housing 32 may be designed in such a manner as to optimize its resonance characteristics. The housing 32 can be connected to the conduit 30 to direct flow through the filter 24. One or more probes 20 and 22 may be installed in the housing 32 to transmit and receive microwave energy.

  A mesh or screen (not shown) may or may not be attached to the conduit 30 or housing 32 to limit microwave energy. In some applications, the use of high frequencies may be desired, limiting the microwave energy and creating a resonant cavity in these conditions to limit mesh, screen, or some other form of conduit 30 Requires the use of.

  In one embodiment, the microwave filter detection system shown in FIG. 3 may include a controller 34. The control device 34 may be integrated into an existing conduit unit, such as an engine control unit (ECU), or a single control unit, and may communicate with other control systems. It does not have to be. There may be one or more controllers 34. The controller may control a signal generator 36 that is configured to generate a microwave signal within a given frequency range. In one embodiment, the signal generator 36 may be a voltage controlled oscillator and the controller 34 may be configured to control the signal generator 36 with a variable voltage.

  The controller 34 may be a processing unit such as a microprocessor or a custom semiconductor device and is configured to execute a series of instructions. These instructions may be permanently programmed into the device or may be stored in a readable storage element such as a memory device. The memory may be read-only such as ROM, or may be read / write such as RAM, DRAM, FRAM, or a combination of the two. In addition to the memory, the controller 34 may have input and output ports so that it can communicate with various sensors, detectors, and other devices described herein.

  The microwave signal generated by the signal generator 36 may be fed into the splitter 38 and to the circulation device 40. The circulation device may be connected to a probe 22 that may be configured to transmit and receive microwave signals within the cavity 32. The circulation device may further be connected to the detection device 42, and the detection device 42 may be connected to the control device 34. In one embodiment, the detection device 42 may be a diode detection device such as, for example, a Schottky barrier diode configured to detect a microwave signal received by the probe 22.

  The controller 34 may be connected to a detector 44 that is configured to detect the microwave signal from the probe 20. In one embodiment, the detection device 44 may be a diode detection device such as a Schottky barrier diode. Other detection devices are possible. The detection device 44 may be further connected to a probe 52 installed in the cavity 46. Another probe 54 may also be installed in the cavity 46 and connected to the splitter 38 by a switch 48. Switches 48 and 50 may also be connected to the controller 34. The controller 34 closes the switch 50 to allow the signal to pass from the splitter 38 to the circulator 40 to introduce microwave energy into the cavity 32 to monitor the filter 24 for clogging, The switch 48 may be configured to open. In another mode of operation, controller 34 may close switch 48 and open switch 50 to transmit a signal from splitter 38 to probe 54. Transmitting signals from probe 54 to probe 52 through cavity 46 is useful for implementing a self-diagnostic function to determine whether the microwave filter sensing system shown in FIG. 3 is functioning properly. possible. In this embodiment, the cavity 46 functions as a reference cavity and may or may not contain any opening.

  In the system shown in FIG. 3, a cavity 46, probes 52 and 54, or switches 50 and 48 that provide additional self-diagnostic functions may be unnecessary if this function is not required in a given application. Please note that it is good.

  The microwave filter detection system may also include a temperature sensor 56 and a humidity sensor 58. Sensors 56 and 58 may be attached anywhere along the conduit 30 on the housing 32 or in the filter 24. Microwave measurements can be affected by temperature or humidity variations within the resonant cavity 32. Sensors 56 and 58 may allow controller 34 to change the microwave signal by performing temperature or humidity corrections.

  In operation, microwave energy is established in the cavity 32 of the device 10. There are a number of modes that can be used to determine trap clogging. In one embodiment, the signal generator 36 may be configured to generate a radio frequency signal and sweep a frequency range sufficient to generate two or more cavity resonance modes within the housing 32. In another embodiment, the signal generator 36 may only be configured to sweep the frequency range necessary to generate the desired resonant mode. The required frequency range is a function of the size of the cavity 32. In one embodiment, the cavity 32 has a diameter of 5.66 inches and a length of 6 inches, and the frequency range of operation may be 1 GHz to 2 GHz. However, any cavity 32 size and frequency range may be used. The frequency may or may not be in the microwave range depending on the size and shape of the cavity 32.

  In one embodiment, the controller 34 may control the signal generator 36 to generate a microwave signal sufficient to generate more than one resonance mode within the cavity 32. The splitter 38 may direct the microwave signal to the circulation device 40. The switch 50 may or may not be used. When operating in the transmission mode, the circulation device 40 may direct the microwave signal to the probe 22. Probe 22 may transmit a microwave signal from probe 22 through filter 24 to be received by probe 20. The detection device 44 may detect the signal received by the probe 20 and relay the signal to the control device 34. In this manner, the resonance curve of the cavity 32 may be sampled using transmission.

  When operating in the reflective mode, the circulator 40 may allow the probe 22 to transmit and receive microwave signals. Thus, signals transmitted and received by the probe 22 may be directed to the detection device 42. The detector 42 may relay the detected signal to the controller 34, thus allowing the resonance curve of the cavity 32 to be sampled using reflection.

  The signal received by the detector 42 or 44 may or may not be filtered or amplified before being transmitted to the controller 34.

  The controller 34 obtains signals from the detectors 44 and 42 and uses analog means, or is contained within the controller 34 or on a computer readable storage medium accessible by the controller 34. The signal may be processed using a computer program that follows the set of instructions. Signal processing includes filtering, smoothing, applying, and calculating various signal parameters and statistical data such as temperature, humidity, or components of accumulated material, or correction factors or compensation. The controller may perform temperature or humidity compensation by monitoring the temperature sensor 56 or the humidity sensor 58 and applying a reference value such as from a lookup table, or a correction function such as a formula or series of formulas. In applications where humidity or temperature compensation is not required, the probe 56 or 58 may not be used.

  The signal parameter of interest may be the resonance mode amplitude, frequency, peak width, or quality factor of one or more cavities 32. The controller 34 may sample the entire resonance curve or only the frequency range required for the resonance mode of interest to determine the above signal parameters. In one embodiment, the above signal parameters are resonant using a computer program according to a series of instructions that are contained within the controller 34 or contained on a computer readable storage medium accessible by the controller 34. It may be determined from a curve. Statistical data for parameters such as the mean, median, mode and standard deviation of two or more measurements may also be calculated in a similar manner. The above parameters may relate to the amount, type, and distribution of material accumulated in the filter 24.

  Controller 34 may compare the received signal parameter to a reference. This criterion may be a series of stored values based on the shape of the cavity used. In another embodiment, the reference is a previously received signal. In this method, the control device may monitor parameter changes over time.

  One means of determining the signal quality factor may utilize the controller 34 to change the operation of the signal generator 36. When the signal generator 36 is a voltage controlled oscillator (VCO), the drive voltage of the VCO has an AC signal superimposed on the DC signal. The DC signal is varied by the controller 34 until the signal response from the detector 44 or 42 shows a maximum. The AC signal amplitude is then varied by the controller 34 until the amplitude of the response measured by the detector 44 or 42 indicates the required peak-to-value ratio, which can be adjusted depending on the measurement conditions. If a one-half factor is selected as the ratio, the output drops by 3 db from peak to valley.

  The amplitude of the AC signal determines the value of Q. The relationship is almost inversely proportional. For this reason, the amplitude of the AC signal is substantially proportional to the width of the resonance curve. The measured values showed that the soot accumulation in several resonance modes is linearly proportional to the peak width, and thus the amplitude of the AC signal is approximately proportional to the soot level.

  A number of methods can be used to measure peak pair values, including lock-in techniques (phase sensitive detection). Also, the frequency of the AC signal can be variable or constant. A frequency from 0.1 Hz to 100 Hz can be used.

  A circuit that locks at the resonant frequency, such as a circuit with feedback, can be used. Analog circuitry can be used to determine the resonant frequency by providing the correct amplification (and phase) of the signal and feeding it to the VCO.

In addition to changing the frequency of the source, an alternative method of determining Q relies on changing the resonant frequency of the cavity 32 with a constant frequency source. The change in the resonant frequency of the cavity 32 may be due to a change in size or shape, a change in dielectric constant, or a combination of the two. The resonant mode is swept across a narrow, fixed frequency oscillator and the response is measured. It will be possible to calibrate the influencing factors (size, shape, or dielectric constant) to the resulting change in frequency and thus to the Q of the device. The influencing factors that change the characteristics of the cavity 32 are the actual change in shape as is possible with sliding shorts in the walls of the cavity 32, or the movement from a low electric field to a high electric field (displacement, rotation, or other means). It may be a substitution of a dielectric or conductive substance. The amount of change required is related to the Q of the signal and the stability of the signal generator. For this reason, if the signal _{generator has} a frequency stability of the quantity Δf _generator , the influencing factor needs to change the resonance frequency of the cavity 32 by the coefficient of Δf _generator . Similarly, if the amount of clogging to be measured results in a change in the resonant frequency of Δf _loading , the change in the resonant frequency of the cavity 32 needs to be greater than Δf _loading . The change in resonant frequency due to influencing factors must be greater than Δf _generator , Δf _loading , and the change in Q due to clogging, f * ΔQ.

  Alternatively, a wideband signal could be used to drive the cavity 32 with response measurements over a wide frequency range sufficient to determine Q.

  In yet another embodiment, Q can be evaluated using a hardware filter. In the case of the clean filter 24 without wrinkles, Q is high and the width of the resonance mode is very narrow. A suitable filter design can be used to filter the signal (peak at resonance). As clogging of filter 24 increases, Q decreases, peak width increases, and most signals pass through the filter, increasing the sensor output voltage. The filter can be designed to accommodate Q where the increase in voltage output exceeds some threshold.

  The quality factor may also be determined by measuring the attenuation of the signal in the microwave cavity 32 after the signal generator 36 is suddenly stopped.

  The controller 34 may also be configured to initiate operation based on the amount, type, or distribution of material accumulated in the filter 24. In one embodiment, the controller 34 may initiate regeneration of the filter 24 or activate an alarm when the clogging of the filter 24 exceeds a certain threshold. The regeneration of the filter 24 may be triggered based on the total amount of soot accumulation in the filter 24 or local clogging that exceeds a certain threshold. In another example, the controller 34 may trigger an alarm when the filter 24 ash clogging exceeds a certain threshold to alert the operator to clean or replace the filter 24. In another embodiment, the controller 34 may trigger an alarm in response to detection of a fault or misoperation of the filter 24 or detection of misoperation at the individual sensors and components depicted in FIG. .

  The controller 34 may also execute a series of instructions contained on a computer readable storage medium, such as, for example, a computer program or algorithm. The computer program may be used to evaluate the components of the substance accumulated in the filter 24 based on exhaust or engine operating conditions and the history of the filter 24. The estimation of material components, in one embodiment, includes soluble organic materials, carbon, and sulfates, and soot components such as ash. In another embodiment, the computer program evaluates the amount of material accumulated in the filter 24, uses the calculated clogging value of the filter 24, pressure measurements, or other microwave sensing or some other means. And may be used to compare the measured clogging value of the filter 24.

  In one embodiment, the controller 34 may implement a self-diagnostic function to ascertain whether the various components and subsystems are functioning properly. In one embodiment, the controller 34 may control the signal generator 36 to generate a reference signal. Splitter 38 may direct the microwave signal to switch 48. The controller 34 may operate a switch 48 that allows a reference signal to pass from the splitter 38 through the reference cavity 46 to the detector 44. The control device 34 may compare the reference signal from the detection device 44 with a known reference value. If the detected signal and criteria deviate further than an acceptable amount, the controller 34 may trigger an alarm or log a failure to indicate an error or malfunction. In a similar manner, a reference cavity and switch may also be utilized between splitter 38 and detector 42 as part of the diagnostic system.

  In another embodiment, the controller 34 may instruct the signal generator 36 to generate a reference signal that is transmitted by the probe 22 through the filter 24. The reference signal may be received by probe 20 and detector 44 (transmission) or probe 22 and detector 42 (reflection) and returned to controller 34. The reference signal may or may not be in the microwave range and may or may not result in the generation of one or more resonance modes within the housing 32. The controller 34 may compare the reference signal from the detection device 44 or 42 to a known reference value and may perform a self-diagnostic function in this manner.

  The resonance curve sampled from the cavity 32 may be used to monitor the amount, type, and distribution of material collected in the filter 24. In one embodiment, the material collected by the filter 24 may be soot or ash. The characteristics of the resonance curve may also be used to determine the condition or health of the filter 24, such as detecting cracks or areas where the filter 24 has melted.

  The cavity 32 may be optimized to enhance measurement sensitivity, extend the measurement range, or change the resonant characteristics of the cavity 32 when a given mass of the filter 24 is clogged.

  In one embodiment, external elements, such as screens or meshes, are installed upstream or downstream of the filter 24 or connected to the housing 32 or the exhaust pipe 30 to provide higher frequencies above the cutoff of the inlet and outlet compartments. It may be possible to use it. As an alternative to the mesh, providing an improvement to the exhaust pipe 30 allows the output of the pipe 30 to be at a local constriction of the exhaust pipe 30, a mesh or screen, or other exhaust element location such as a muffler or engine. It would be possible to prevent transmission of degradation. The use of higher frequencies with shorter wavelengths can increase the number of resonant modes of the cavity 32 and improve the spatial resolution of the sensor for measuring local material accumulation or distribution.

  The mesh is conductive and can be connected to or disconnected from the sidewalls of cavity 32 or other conductive elements. The screen is a deformation of the mesh where conductors without conductive elements in the other direction are arranged in a given pattern. Thus, the electric field can affect modes with polarization that is parallel to the conductor, but not other modes. The screens do not necessarily have to be parallel to each other, but they must have anisotropy so that some modes are preferentially affected and others are not. The screen can have parallel conductive elements, radial conductive elements, polar elements, or other patterns. The preferred arrangement of screens and mesh is in a planar form, but does not mean to exclude other arrangements.

  In addition, the filter 24 itself may be installed in a larger housing or a smaller housing in the assembly. This “double wall” housing structure increases the size of the microwave cavity 32 while concentrating the wrinkles only in the center of the cavity 32 containing the filter 24. Further, the size of the resonant cavity 32 may be increased relative to the filter 24 such that the filter 24 occupies only a small portion of the cavity 32, thereby extending the operating range of the system.

  FIG. 4 further illustrates a system that uses homodyne detection that may be used to improve the signal-to-noise ratio of the measurement. The controller 34 controls a signal generator 36 that feeds the RF signal to the splitter 38. The splitter 38 may feed the signal to the circulation device 40 or the phase shift device 60. The phase shift device 60 is connected to the mixer 62.

  Circulator 40 may be connected to probe 22 to allow RF signals to be transmitted and received by probe 22 through cavity 32. Alternatively, the probe 22 may transmit an RF signal to the probe 20 through the filter 24. The cavity 32 may house the filter 24 and be connected to the conduit 30 to form a particular filter unit 10. The cavity 32 may also contain the probe 20 connected to the mixer 62. The mixer 62 may be connected to a detection device 44 that is also connected to the control device 34. Temperature sensor 56 and humidity sensor 58 may also be connected to conduit 30 either upstream or downstream of filter 24.

  The signals received by the detectors 42 and 44 may or may not be filtered or amplified before being transmitted to the controller 34.

  System operation utilizes the phase shifter 60 with the mixer 62. The phase shifter 60 changes the phase of the signal generated by the signal generator 36 and received from the splitter 38. The signal (V 1) from the splitter 38 and the signal (V 2) transmitted through the filter 24 contained in the cavity 32 toward the phase shift device 60 are combined in the mixer 62.

The signal from the mixer 62 has a component that fluctuates as a DC bias and V1 ^* V2 ^* sin (Φ) + DC bias, and Φ is obtained by adding a phase component in a stable state to the phase from the phase shift device 60. Is. The DC bias does not depend on Φ. By changing the phase, Φ varies and the component V1 ^* V2 can be extracted from the signal. By using a larger V1, it is possible to detect a small signal V2 from the cavity. The component V1 ^* V2 ^* sin (Φ) can be determined via electrical filtering of the output of the mixer 62 or signal processing by the controller 34.

  FIG. 5 shows the transmission element S21 as a function of frequency, and FIG. 6 shows the reflection from a single launcher / receiver system. In FIG. 5, the rod antenna was installed on the opposite side of the trap as shown in FIG. The graph of FIG. 6 was created using a single antenna and the information is in the reflected signal. 5 and 6 both detect a transmitted signal in a 5.66 inch diameter cavity containing a voltage controlled oscillator and a cordierite particulate filter to sweep the frequency range from 1 GHz to 2 GHz. Shows a plurality of resonance modes generated using a Schottky barrier diode. For clean filter 24, soot accumulation causes a decrease in resonance peak amplitude, a shift in frequency of the resonance peak, an increase in peak width, and a decrease in quality factor Q. All of these parameters may be used to monitor the clogging of the filter 24 and the change in signal characteristics is shown graphically in FIG.

  Specifically, FIG. 5 shows that the presence of soot reduces the resonant frequency in each mode and also reduces the quality factor Q. In addition, the amplitude of each peak is also attenuated compared to the waveform produced when no wrinkles are present. Similarly, FIG. 6 shows a dramatic decrease in amplitude at each resonant frequency, as well as a frequency shift and a Q decrease.

  FIG. 7 is an enlarged view of the transmission mode of FIG. 5 and shows details of the vicinity of the mode near 1.7 GHz. As noted above, the presence of wrinkles changes the characteristics of the received waveform. In this figure, the amplitude decreases when wrinkles are present. Similarly, the peak width increases and decreases its quality factor Q. Finally, the frequency of resonance is shifted due to the presence of soot. It is these differences that allow the trap clogging decision to be made.

  The above signal parameters, i.e., amplitude, frequency, peak width, quality factor, etc., can be calculated from the resonant curve sampled using controller 34, including satellite signals from the degenerate mode. In some cases, these signal parameters may be determined by analog means, and in other cases, more advanced signal processing, such as by digital means, and application of various algorithms may be employed. . The algorithm may be stored in the controller 34 or on an accessible computer readable storage medium. The resonance curve may be sampled more than once and the signal parameters are calculated after averaging the resonance curve or multiple cycles where one cycle is the entire frequency range generated by the signal generator 36. Also good. In another example, signal parameters for the resonance curve may be calculated for each cycle. Additional signal statistics such as mean, median, mode, and standard deviation of various parameters may also be calculated and utilized to determine clogging of the filter 24.

  FIG. 8 shows the sensor output of the microwave detection system as a function of filter 24 clogging relative to the resonant mode of one cavity 32. In this embodiment, the sensor output is the reciprocal of the signal quality factor. Any of the above parameters such as amplitude, frequency, peak width, quality factor, etc. may be used to determine the clogging of the filter 24, some parameters being more advantageous than others in certain applications. There is. For example, in some cases, the signal amplitude attenuates non-linearly with increasing clogging of the filter 24, while the reciprocal of the signal quality factor may behave linearly as shown in FIG. .

  FIG. 8 also represents a calibration curve that may be uploaded on a computer readable storage medium accessible by the controller 34. The calibration may be, for example, a look-up table, a mathematical formula, or other suitable form. The comparison of the measured resonance curve and the calculated parameters may be compared to a calibration value to determine filter 24 clogging. In some cases, only one calibration value or threshold may be required, as it may be important to only determine whether the clogging of the filter 24 has exceeded some important value. In other applications, a more detailed calibration function as shown in FIG. 8 may be required.

  The various resonant modes shown in FIGS. 5 and 6 are due to variations in electric field strength in different regions of the cavity 32. High field strength regions are more strongly affected by the presence of material accumulation in those regions. This effect may be used to monitor the distribution of substances accumulated in the filter 24.

  FIG. 9 is a diagram showing how different resonance modes occur in different regions of the filter 24 with high electric field strength. In FIG. 9, only the filter 24 is shown and the resonant cavity 32 is not shown. The figure shows that mode X occurs in the region of high electric field in the center of filter 24 and mode Y occurs in the region of high electric field in the inlet and outlet sections of filter 24. By sampling modes X and Y, the distribution of material clogging of the filter 24 can be determined. Increasing the number of modes generated in the filter 24, such as by expanding the frequency range of operation, etc., by sampling more regions of the filter 24, as shown by mode Z in FIG. The spatial resolution of measurements can be increased. An example of a mode axial analysis result is shown in FIG. 9, but there may also be differences in mode structure and electric field strength in the radial direction to determine the radial distribution of the material accumulated in the filter 24. Can be used.

  If the material accumulation in filter 24 is uniform, all resonant modes can be equally affected. Some modes may be more affected than others when there is a non-uniformity of material distribution. FIG. 10 shows data showing the three resonance modes, clearly shown as A, B, and C. Data corresponding to the case without defects is a clean filter 24. The data corresponding to the case with wrinkles shows the effect of non-uniform wrinkle distribution on the resonant mode features. In this case, the soot was deposited only near the outer periphery of the front surface of the filter 24. Clearly, modes A and C are affected by the presence of wrinkles in this region of filter 24, while mode B is not affected.

In one embodiment, multiple resonance modes can be generated and sampled in the filter 24. Several signal parameters may be measured or calculated from the resonance curve. For each measured signal parameter P _{i, m} (subscript “i” corresponds to the mode number), the deviation Dev _i of the measured signal parameter from the reference signal parameter P _{i, r} is as follows: It is.

Dev _i = (P _{i, m} −P _{i, r} ) / P _{i, r}
If the deviation Dev _i of the same signal parameter for each mode i is similar, clogging of the filter 24 is uniform. However, if the same signal parameter deviation for each mode is significantly different from the deviation of one or more modes, the clogging of the wrinkles may be non-uniform.

When this example is applied to the peak amplitude in FIG. 10, Dev _A is -0.24, Dev _B is -0.06, and Dev _C is -0.26. The results show that the soot accumulation on the front surface of the filter 24 mainly affects modes A and C, while mode B is relatively unaffected. On the other hand, a large change in mode B signal deviation relative to modes A and C will indicate that there is little material accumulation in front of the filter 24. However, it should be noted that the resonant mode structure is a function of the design and shape of the cavity 32. The selection of the system operating frequency to generate the appropriate resonant mode depends on both the shape of the cavity 32 as well as the area of the filter 24 being sampled. The above method can be used to develop the correlation required for specific resonant modes associated with material accumulation in different regions of the filter 24.

  FIG. 11 further illustrates the effect of the spatial distribution of material accumulated in the filter 24 on the microwave response to one filter 24 resonance mode. The graph of FIG. 11 shows the inverse change in signal quality factor as a function of filter 24 clogging when filter 24 is clogged at a relatively low level. The data corresponding to line 64 is due to the uniform soot accumulation of filter 24. At line 66, the center of filter 24 is initially disturbed for the first 0.5 g / L of filter 24 clogging, thereby preventing soot from depositing in this area of filter 24.

  When no soot was deposited in the center of the filter 24, the resonant mode signal characteristics did not change. Specifically, the data shown in FIG. 11, line 66 indicates that there is no change in the reciprocal of the signal quality factor for a filter 24 of soot level from 0 g / L to 0.5 g / L. When obstructions are removed and soot is deposited in the center of filter 24, the reciprocal of the signal quality factor increases with clogging, which is also due to line 66 when the soot level exceeds 0.5 g / L. Indicated. Note that the signal parameter need not be a quality factor as shown in FIG. 11, but can be any suitable parameter such as, for example, the amplitude, peak width, or frequency of one or more resonant modes. I want. Similarly, signal statistics such as the mean, median, mode, or standard deviation of one of the above signal parameters may also be used.

  In one embodiment, by monitoring changes in one particular mode, such as mode 5, the amount of material accumulated in the center of the filter 24 relative to other resonant modes may be determined. All similar changes in the resonant mode indicate uniform material accumulation in the filter 24 or at least for the region sampled by the mode used. An increase in the reciprocal of the mode 5 signal quality factor relative to the other modes indicates an increase in material accumulated in the center of the filter 24. A decrease in the reciprocal of the mode 5 signal quality factor relative to the other modes indicates that less material has accumulated in the center of the filter 24.

  However, it should be noted that any signal parameter or statistic may be used and that the resonant mode structure is a function of the design and shape of the cavity 32. The selection of the system operating frequency to generate the appropriate resonant mode depends on both the shape of the cavity 32 as well as the area of the filter 24 being sampled. The spatial resolution of the measurement may be improved by including additional modes, both low and high order. Similar correlations to changes in other resonance mode characteristics may be developed for material clogging of various regions of the filter 24.

  As shown in FIGS. 10 and 11, sampling the resonance curve and comparing changes in the signal response of multiple resonance modes thus provides information about the spatial distribution of the material accumulated in the filter 24. I will provide a.

  In some cases, the location of the material of the filter 24 may not be important, and it may be important only to determine whether there is significant non-uniformity of the filter 24 clogging. In these applications, the controller 34 may be configured to start operation when the value of at least one signal parameter corresponding to one resonance mode is outside of an acceptable range. For example, regeneration of the filter 24 may be initiated when the clogging of the local filter 24 exceeds some threshold, and it is not important that there is a higher clogging in the filter 24 and clogging It may only be important to be sufficiently non-uniform, such as outside the acceptable range.

  The microwave detection system may also be utilized to determine the type of material that is stored in the filter 24. FIG. 12 shows the difference in signal characteristics for the resonant mode of one filter 24 when the filter 24 contains and does not contain ash. In this example, the presence of ash strongly affects the degenerate mode, or the small side mode, or the peak near the main resonant mode. As the ash level of the filter 24 increases, the amplitude, peak width, quality factor, and frequency of these submodes are affected. Monitoring the microwave signal to detect changes in these side modes or peak features provides one means for simultaneously detecting both ash and soot clogging.

  As conductive particulates are deposited in the cavities 32, the dielectric properties of the cavities 32 may change due to the presence of a partial conductive layer. When this occurs, not only will the absorption increase, but the mode characteristics will also vary. This is due to mode operation in the presence of a conductive medium on the surface of the filter 24. In general, the modes have different orientations relative to the surface. Since the antenna can generate multiple modes using the same electric field structure rather than different polar orientations, there are multiple modes at least at the same frequency (degenerate mode). A mode that uses a parallel electric field for one of the surfaces is mainly orthogonal to one of the surfaces (and thus the filter usually uses a square channel) It will have a different behavior than it is at 45 degrees to the surface. Thus, it may be possible to distinguish between the two modes by a frequency shift using a partially conductive electrical path. To optimally use this property, it would be useful to have an antenna that can generate multiple modes (any large antenna) or have multiple antennas. These antennas can be electric dipoles (rods) or magnetic dipoles (current loops).

  Another type of mode degeneration is due to modes that are not symmetric with respect to the central plane of the device (a plane perpendicular to the midpoint axis from the end). One mode has a high electric field on the partition of the device (which may be one end of the device) and a low electric field on the other. Due to symmetry, such a mode has a corresponding mode with the opposite behavior, with a high electric field on the opposite side. Because of symmetry, both modes will have the same frequency and the same Q for a uniformly clogged filter 24. For example, if pollutants such as ash accumulate in a non-uniform manner, one of the modes will be affected differently and thus one of the different modes. There is a frequency shift and a Q change. For this reason, mode degeneracy is destroyed and a plurality of peaks are observed in the measurement.

  Two or more antennas or waveguides may be used to transmit signals through the DPF. In the case of a DPF with non-uniformity, such as non-uniform material clogging, using different polarizations (with respect to DPF) will distinguish degenerate modes.

  The appearance and disappearance (integration) of peaks can be used to measure the amount and type of clogging, clogging non-uniformity, and other characteristics of the cavity 32. It may also be possible to measure temperature, to characterize regeneration and during normal operation of the catalytic DPF (accumulation / oxidation depends on trap temperature / oxygen / clogging characteristics). Useful for determining accumulation.

  In addition, ash, sulfate, and phosphate, mainly composed of various metal oxides, may also exhibit different dielectric properties than the filter 24 and soot collected on the filter 24. The dielectric properties of ash and soot can also vary as a function of temperature and as a function of the frequency used to create the various resonant modes. In one embodiment, the dielectric properties of ash can cause increased RF signal absorption at elevated temperatures, and can result in a decrease in amplitude and quality factor (increased peak width) of one or more resonant modes. In this manner, ash is easily detected by comparing the resonant mode characteristics of filter 24 clogged with ash at an elevated temperature with the reference signal of filter 24 at the same temperature without any ash. Can result in replaying. Furthermore, the distribution of ash in the filter 24 may be determined by generating and sampling a plurality of resonance modes.

  In general, the amount and distribution of two or more materials in the filter 24 may be determined using the method described above if each material has different dielectric properties. In addition, the dielectric constants of different materials can also have different temperature and frequency dependencies. All of these differences will affect the resonant mode structure and can be utilized to determine both the amount and type of material in the filter 24. These principles can be applied to a myriad of materials and are not limited to straw or ash.

  Additional parameters for determining the constituents of the accumulating material can be provided by operating the RF filter clogging measurement system in reflection (S11, S22) and transmission (S12, S21) modes, whereby the coupling matrix Contains additional elements inside.

For any given mode m, the signal amplitude ratio (A _m ), resonant frequency (f _m ), and quality factor (Q _m ) are functions for different clogging in the filter 24. Therefore,
A _m = f _m (α ₁ , α ₂ ,..., Α _n )
f _m = G _m (α ₁ , α ₂ ,..., α _n )
Q _m = H _m (α ₁ , α ₂ ,..., Α _n )
Where (α ₁ , α ₂ ,..., Α _n ) are species 1, 2,. . . , N is clogged. Different species generally have different values for the real and imaginary parts of the dielectric constant (the frequency shift is largely dependent on the real part of the dielectric constant, and the amplitude ratio and quality factor depend on the imaginary part) Since the part and imaginary part also vary with frequency, different amounts of dependence on A _m , f _m and Q _m have different functional dependences on different species. It is possible to provide an approximation of dissimilar content through standard means such as using an expert system. External calibration may require an inverse algorithm. The larger the number of signals, the smaller the number of species and the better the evaluation. Other on-board diagnostics can be used with this method to improve component assessment.

  The inverse algorithm is of the form:

α ₁ = X (A ₁ , A ₂ ..., A _p , f ₁ , f ₂ ,..., f _p , Q ₁ , Q ₂ ,..., Q _p )
α ₂ = Ψ (A ₁ , A ₂ ..., A _p , f ₁ , f ₂ ,..., f _p , Q ₁ , Q ₂ ,..., Q _p )
...
α _n = Z (A ₁ , A ₂ ..., A _p , f ₁ , f ₂ ,..., f _p , Q ₁ , Q ₂ ,..., Q _p )
The algorithm can also provide an estimate of deviation from expected and actual clogging. In one embodiment, clogging is inversely proportional to Q, although other parameters such as amplitude, frequency, or width of one or more resonant modes may be used, as shown in FIGS. To do. Thus, the form of the formula can alternatively be:

α ₁ = X (A ₁ , A ₂ ..., A _p , f ₁ , f ₂ ,..., f _p , 1 / Q ₁ , 1 / Q ₂ , ..., 1 / Q _P )
α ₂ = Ψ (A ₁ , A ₂ ..., A _p , f ₁ , f ₂ ,..., f _P , 1 / Q ₁ , 1 / Q ₂ ,..., 1 / Q _P )
...
α _n = Z (A ₁ , A ₂ ..., _Ap , f ₁ , f ₂ ,..., f _P , 1 / Q ₁ , 1 / Q ₂ ,..., 1 / Q _P )
Furthermore, it is advantageous to determine the dependence of the cavity factor of each mode by an equation of the form

A _m = F _m (α ₁ , α ₂ ,..., Α _n )
f _m = G _m (α ₁ , α ₂ ,..., α _n )
1 / Q _m = H ′ _m (α ₁ , α ₂ ,..., Α _n )
The inverse of this matrix of the algorithm is more robust than reversing a set of equations that use H _m .

The above process can be generalized to include determining the component distribution. (Α ₁ , α ₂ ,..., Α _n ) is the concentration most affected by mode α, and (β ₁ , β ₂ ,..., Β _n ) is most affected by mode β. The above method can be generalized to include different species distributions, assuming that the concentra- tion is subject to. “Most affected” refers to those regions in the filter 24 where the electric field of the associated mode is high. In this case, the inverse algorithm is
A _m = F ^* _m (α ₁ , α ₂ ,..., Α _n , β ₁ , β ₂ ,..., Β _n ,.
f _m = G ^* _m (α ₁ , α ₂ ,..., α _n , β ₁ , β ₂ ,..., β _n ,.
1 / Q _m = H ^* _m (α ₁ , α ₂ ,..., Α _n , β ₁ , β ₂ ,..., Β _n ,.
It becomes.

  There can be more variables than equations, so it may be necessary to make assumptions about places where different composites are likely to provide the reverse. The best way is to build a large matrix of data using different clogs of different composites at different locations and then use an expert system to derive the inverse algorithm (s) That would be true.

  Faults in the filter 24 such as cracking and melting affect the dielectric properties of the ceramic substrate. Loss of a portion of the substrate due to cracking, breakage, or dissolution creates an invalid space in a predetermined area of the filter 24. The experimental data shows the change in microwave signal response for filters with various defects, as represented in FIG. Changes in the signal response include, among other things, frequency shifts, amplitude changes, and filter 24 quality factor changes.

  In addition, faults in the filter 24 may be detected by monitoring the accumulation or lack of specific substances in specific areas of the filter 24. Cracked, broken or melted filter 24 allows soot to leak out of filter 24, with little soot or ash accumulation seen in the area near the fault. In addition, the failure mode of the filter 24 can also affect the flow of exhaust gas through the filter 24. Changes in the exhaust flow distribution will also affect the deposition characteristics of the material collected in the DPF, which uses multiple resonant modes to monitor the accumulated material distribution. Can be detected.

  The microwave detection system disclosed herein can use inexpensive components, the microwave source is an enhanced microwave chip as used in mobile phones, and the receiver is an amplifier Can be a simple diode with or without. The microwave chip may contain a detection device 44 or 42, a signal generation device 36, and a control device 34. As the detection system, advanced detection systems such as lock-in detection, heterodyne detection, and homodyne detection can be used.

  The clogging was assumed to be soot or ash clogging (from an engine, etc.), but as long as it has a different dielectric constant from the background filter material (for air / engine exhaust), the surface of the filter Any material that accumulates in a significant amount above can be measured.

  Those skilled in the art will recognize that modifications and variations of the present invention will occur and such modifications and variations are intended to be included within the scope of the appended claims.

  Accordingly, the various embodiments of radio frequency filter clogging measurement systems and methods of system control described herein monitor the amount, type, and distribution of substances accumulated in a filter, as well as the filter or system. Can be used to detect any failure. The system may further trigger an action based on the monitored clogging condition or status of the filter.

  Although the above description contains considerable specificity, this should not be construed as limiting the scope of any embodiment, but as an illustration of these presently preferred embodiments. is there. Numerous other effects and variations are possible within the teachings of various embodiments. For example, radio frequency clogging sensors can be applied to any type of filter for any application where knowledge of the amount, type, and distribution of material clogging in the filter is important.

  Examples of additional applications of the filter clogging measurement system described herein include air filters for use in HVAC systems and filter bag housings used in industrial applications. The filter need not be connected to the engine, but may be used for several purposes. Furthermore, the filter detection system is not limited to filtration of particulates from gas, but is equally applicable to liquids.

  Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.

Claims (15)

A method for determining contaminant clogging of a filter contained within a metallic container forming a resonant cavity, wherein the filter has a first dielectric constant, the contaminant being the first dielectric. Having a second dielectric constant different from the rate, the method comprising:
Establishing microwave energy in the cavity to include a plurality of cavity resonance modes;
Monitoring a change in cavity microwave response in the plurality of cavity resonance modes;
Determining a material clogging in each of the plurality of cavity resonance modes based on the change in the cavity microwave response.   The method of claim 1, wherein the material clogging comprises a spatial distribution of the material within the filter.   The method of claim 1, wherein the change in the cavity microwave response comprises a change in Q of one of the plurality of cavity resonance modes.   The method of claim 1, wherein the change in the cavity microwave response comprises a change in amplitude of one of the plurality of cavity resonance modes.   The method of claim 1, wherein the change in the cavity microwave response comprises a change in frequency of one of the plurality of cavity resonance modes. Determining the region of the filter associated with each resonant mode;
Comparing the changes in the plurality of resonance modes with each other;
The method of claim 1, further comprising: determining a region of substance accumulation based on the comparison of the changes.   The method of claim 1, further comprising initiating filter regeneration based on the material clogging.   The method of claim 1, further comprising determining an amount of ash in the filter.   The method of claim 1, wherein an antenna is used in a reflective mode to transmit microwave energy to and receive microwave energy from the cavity.   The method of claim 1, wherein two antennas are used in a transmission mode, one antenna transmits microwave energy to the cavity, and the other antenna receives microwave energy from the cavity.   11. The method of claim 10, wherein each of the two antennas is also used in a reflective mode to create a coupling matrix based on the transmit antenna, the receiving antenna, and the used mode. A system for determining contaminant clogging of a filter, the contaminant having a dielectric constant different from the first dielectric constant of the filter;
The filter adapted to remove contaminants from the flow;
A metal container forming a resonant cavity, the metal container containing the filter;
A signal generator for outputting a signal having a frequency range to include a plurality of resonance modes of the cavity;
At least one antenna for transmitting the signal from the signal generator into the cavity;
At least one antenna for receiving the transmitted signal from the cavity;
A controller configured to compare a parameter of the received signal with a reference and to determine clogging of the material based on the comparison.   The system of claim 12, wherein the criteria includes a previously received signal.   The system of claim 12, wherein the criteria includes a stored value.   The system of claim 12, wherein the parameter is selected from the group consisting of amplitude, frequency, and quality factor.

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