Patent Application
20170138781
The field of the disclosure relates generally to parameter measurement systems and, more particularly, to a method and system for improving parameter measurement by leveraging and combining sensor outputs having desired characteristics for measuring a parameter.
At least some sensors are designed to have at least one particular output characteristic, for example, high accuracy or high bandwidth (i.e., high speed or fast response). For example, in at least some aircraft systems, a fuel metering valve (FMV) is used in an engine controller. The FMV includes a fuel actuator sensor with a sensor output having a high bandwidth or fast response characteristic. However, the sensor output from the FMV also includes a low accuracy characteristic, with error of ±5%. Additionally, a fuel flow meter (FFM) includes a sensor configured to provide a signal to the aircraft related to fuel consumption at various stages of flight. The FFM sensor output includes a high accuracy characteristic, with error of ±1% during cruise stages, but also includes a slow response characteristic.
It may be expensive or difficult to design sensors with sensor outputs that combine two desired characteristics and/or to implement more complex hardware designs to reduce effects of low-accuracy sensors. At least some known systems attempt to use closed-loop feedback controls to manipulate sensor output signals from two disparate sensors having different desired output characteristics. However, such systems may be vulnerable to error or compromise when the two signals disagree, as there is no independent parameter to discern which signal to preference.
In one aspect, a measurement system is provided, including a first sensor, a second sensor, and a processor. The first sensor includes a first output signal including a plurality of output characteristics, at least one output characteristic of the plurality of output characteristics being deficient for measuring a desired parameter and at least one output characteristic being suitable for measuring the desired parameter. The second sensor includes a second output signal including at least some of the plurality of output characteristics of the first output signal, the at least one deficient characteristic of the first output signal being suitable in the second output signal for measuring the desired parameter. The processor is communicatively coupled to a memory device, and is programmed to calibrate the first output signal of the first sensor using the second output signal of the second sensor to generate a third output signal comprising the at least one suitable characteristic of the first output signal and the at least one suitable characteristic of the second output signal.
In another aspect, a method for improving sensor accuracy is provided. The method includes receiving a first output signal from a first sensor configured to measure a first parameter, the first output signal characterized as having a relatively high accuracy and a relatively low bandwidth, and receiving a second output signal from a second sensor configured to measure the first parameter, the second output signal characterized as having a relatively high bandwidth and a relatively low accuracy. The method also includes calibrating the second output signal from the second sensor using the first output signal from the first sensor, and generating a third output signal using the calibrated second output signal, the third output signal characterized as having a relatively high accuracy and a relatively high bandwidth for the first parameter.
In yet another aspect, a turbofan engine is provided, the turbofan engine including a core engine including a multistage compressor, a fan powered by a power turbine driven by gas generated in the core engine, a fan bypass duct at least partially surrounding the core engine and the fan, and a flow measurement and control (FMC) system. The FMC system includes a first sensor including a first output signal comprising a plurality of output characteristics, at least one output characteristic of the plurality of output characteristics being deficient for measuring a desired parameter and at least one output characteristic being suitable for measuring the desired parameter. The FMC system also includes a second sensor including a second output signal including at least some of the plurality of output characteristics of the first output signal, the at least one deficient characteristic of the first sensor being suitable in the second sensor for measuring the desired parameter. The FMC system further includes a controller configured to control actuation of a fuel meter valve (FMV) to control flow of fuel to the core engine. The controller includes a processor communicatively coupled to a memory device, the processor programmed to calibrate the first output signal of the first sensor using the second output signal of the second sensor to generate a third output signal including the at least one suitable characteristic of the first output signal and the at least one suitable characteristic of the second output signal.
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of this disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of this disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein.
In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings.
The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.
Embodiments of the parameter measurement systems described herein provide a cost-effective method for leveraging sensor output from existing sensor in any control system to produce a combined sensor output having desired output characteristics from disparate sensors. More specifically, the parameter measurement systems include a first sensor including a first output signal having a plurality of output characteristics, wherein at least one of the output characteristics is deficient for measuring a desired parameter, such as flow, temperature, pressure, etc., and one of the output characteristics is suitable for measuring the desired parameter. The parameter measurement systems further include a second sensor including a second output signal that may have some of the same output characteristics, but includes output characteristics, which were deficient in the output signal from the first sensor, that are suitable for measuring the desired parameter. The system further include a processor configured to calibrate the first signal using the second signal to generate a third (calibrated) signal having the suitable characteristics from both the first and second output signals of the first and second sensors. As used herein, “suitable” refers generally to a beneficial or desired characteristic for measuring the desired parameter, and “deficient” refers generally to an undesirable or negative characteristic for measuring the desired parameter. Accordingly, certain characteristics may be suitable for measuring one parameter but deficient for measuring a different parameter. The parameter measurement systems facilitate development of a calibration model that is implemented and refined to optimize the combined sensor output according to the application thereof and to facilitate operability of the system in the event of a loss of one of the sensor output signals, thereby facilitating robustness of the system.
In at least some known aircraft systems, under normal operation, the fuel control system accuracy is in the range of about 4-6% error, for example, due to unit to unit variations in fuel metering valves, fuel temperature, and specific gravity effects. This impacts an engine operability margin for compressor stall or combustor lean blowout conditions.
FMV 210 includes at least one FMV sensor 212 (e.g., a linear variable differential transformer (LVDT)), configured to sense a fluid pressure of fuel through FMV 210, which produces an FMV sensor output signal 214 having output characteristics. Specifically, FMV sensor output signal 214 includes low accuracy and high bandwidth (i.e., fast response) output characteristics.
FFM 220 includes an FFM sensor 222, configured to sense a mass flow of fuel to estimate fuel consumption by core engine 112 (shown in
In addition, FMC system 150 includes and/or is in communication with a full authority digital engine control (FADEC) 250 computer system. FADEC 250 includes a non-volatile memory 252.
In the example embodiment, FMV sensor output signal 214 is calibrated during aircraft cruise using FFM sensor output signal 224, thereby producing a calibrated FMV output signal 240. In the example embodiment, controller 230 substantially continuously calibrates FMV sensor output signal 214 during cruise operation of FMC system 150 using calibration model 234. Accordingly, calibration model 234 may be refined continuously or at regular intervals, such that calibration model 234 is up to date. Data associated with calibration model 234 (“calibration data” 238) and/or instructions for implementing calibration model 234 may be stored in memory 252. In the event of FFM 220 and/or FFM sensor 222 failure or other loss of FFM sensor output signal 224 as input to the controller 230, which may otherwise lead to loss of engine performance or operability margin, calibration data 238 is retrieved from memory 252 to facilitate continued implementation of calibration model 234. Accordingly, continued input of calibrated FMV output signal 240 to actuation selector 236 may be facilitated, for example, until FFM sensor 222 is replaced. Calibrated FMV output signal 240 includes a high-accuracy response characteristic, with an accuracy of about 1% error, based on the calibration using FFM sensor output signal 224, as well a fast response characteristic from (original, uncalibrated) FMV sensor output signal 214, with a bandwidth of 10+Hz. Accordingly, in some embodiments, calibrated FMV output signal 240 may provide a back-up control signal to the aircraft in the event of FFM 220 failure.
In alternative embodiments, controller 230 receives inputs from additional components (not shown), such as a fuel nozzle manifold pressure sensor and/or temperature sensor. These inputs may function as supplementary calibration signals for FMV sensor output signal 214 and/or back-up signals for calibrated FMV output signal 240, for example, during non-steady state stage of flight (e.g., takeoff), when the slow response characteristic of FFM sensor output signal 224 may render FFM sensor output signal 224 less useful as a calibration signal. Calibrated FMV output signal 240 may therefore have an accuracy of about 2-3% error, for example, during non-steady state conditions (e.g., due to fuel nozzle variation & pressure signal tolerance).
In some embodiments, calibration model 234 may implement performance of a quasi-state state compensation using the FFM sensor output signal 224 to refine the accuracy of pressure estimations, such as pressure change or delta-p estimations, or temperature estimations, such as turbine inlet temperature, from (original, uncalibrated) FMV sensor output signal 214. Refinement of calibration model 234 (e.g., by substantially continuous operation during steady states) not only facilitates improved estimation of the actual fuel flow into core engine 112 using calibrated FMV output signal 240 but also facilitates providing an improved transient fuel flow signal to other control or monitoring systems (e.g., to a cockpit for display to a pilot of an aircraft). Therefore, improved actuation of FMV 210 by controller 230 is facilitated, reducing margins and increasing fuel efficiency and performance of core engine 112. Additionally, operability margins (e.g., reducing stall, blowout, thrust transient times, start times) of core engine 112 may be improved. Reducing thrust transient times (during which fuel flow may be rapidly reduced) and improving delta-p estimations may further facilitate preventing low-pressure turbine 128 shaft speed droop. As calibration model 234 is refined, controller 230 (e.g., using processor 232) may detect rapid or unexpected changes in FMV sensor output signal 214, which may signal mechanical failures, and controller 230 may facilitate limiting potential for engine overspeed (and potential aircraft thrust control malfunction events), for example, by facilitating actions such as closure of compressor 121 stator vanes. In addition, calibration model 234 facilitates tracking or monitoring (e.g., using processor 232) of nozzle 125 health over time, which may provide earlier indication of nozzle 125 clogging or other degradation.
Notably, FMC system 150 described herein functions using existing sensors 212, 222 in engine assembly 100, i.e., without the need (nor, therefore, the expense) for any additional sensors. Moreover, as FMC system 150 functions with existing sensors 212, 222, FMC system 150 may be implemented on many types of aircraft engines and/or other engine systems (not shown). It should be understood that the present disclosure is not limited to the embodiments specifically described herein, but that the teachings herein may be applicable to additional sensor systems, including pressure sensor systems, temperature sensor system, and any other sensor systems having more than one sensor with output signals having different desired characteristics.
For example, in an alternative embodiment, a pressure control system implemented in an aircraft system includes two pressure sensors, a high-range pressure sensor and a low-range pressure sensor. The low-range pressure sensor produces a low-range output signal having over-pressure protection and a high-accuracy output signal characteristic (about 0.5% error) at low pressure. The high-range pressure sensor produces a high range output signal having high accuracy in high pressure conditions but low accuracy output characteristics in low pressure conditions. Similar to the calibration of FMV sensor output signal 214 described above, the low-range output signal is used to calibrate the high-range output signal during operation of the pressure control system using a calibration model. The calibration model is stored in a memory for later retrieval, for example, upon loss of the low-range output signal.
Second sensor output signal 324 includes a plurality of output characteristics, one or more of which are deficient for measuring a desired parameter, and one or more of which are suitable for measuring the desired parameter. For example, second sensor output signal 324 may have low bandwidth (i.e., slow response) and high accuracy (e.g., about 1% error) characteristics. In one embodiment, second sensor output signal 324 includes FFM sensor output signal 224 (shown in
Second sensor output signal 424 includes a plurality of output characteristics, one or more of which are deficient for measuring a desired parameter, and one or more of which are suitable for measuring the desired parameter. For example, second sensor output signal 424 may have low bandwidth (i.e., slow response) and high accuracy (e.g., about 1% error) characteristics. In one embodiment, second sensor output signal 424 includes FFM sensor output signal 224 (shown in
The above-described systems provide an efficient method for leveraging suitable characteristics of different sensors to produce a single, calibrated output with each of those suitable characteristics, for example, for measuring a particular parameter. Specifically, the above-described systems includes at least two sensors, each having at least one suitable signal output characteristic, and at least a first sensor of the two sensors having a deficient or ill-suited characteristic for the desired purpose (e.g., measurement of a parameter for use in a control system). A second sensor of the two sensors includes a suitable characteristic that can be used to overcome the deficient characteristic of the first sensor. Therefore, an output signal from the second sensor is used to calibrate the output from the first sensor. A third, calibrated signal is produced, having suitable characteristics from both output signals. This calibrated signal not only is better suited for the desired purpose but the calibration thereof may facilitate using the calibrated signal even in the event of a loss of the sensor output from the second sensor, which improves system robustness. By performing the calibration using a processor-implemented model, the above-described systems may be implemented on new or existing systems, reducing the need for more expensive sensors or hardware work-arounds.
Exemplary embodiments of parameter measurement systems and sensor calibration models are described above in detail. The measurement and calibration systems, and methods of operating such systems and component devices are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. Embodiments of the parameter measurement systems and sensor calibration models may be used for a variety of applications, including any system that includes two or more disparate sensors with output signals having different characteristics.
Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
