Aviation fuel oil measuring system based on DSP microprocessor

Abstract

The invention provides an aviation fuel oil measuring system based on a DSP microprocessor, and belongs to the technical field of airborne controllers, the aviation fuel oil measuring system comprises a consumption measuring part, an oil level measuring part and a measuring system processor, the consumption measuring part comprises a turbine consumption sensor and a temperature sensor, and is installed in an oil supply pipeline; the oil level measuring part comprises a variable-diameter capacitive sensor and a dielectric constant compensation sensor, the dielectric constant sensor is installed at the bottom of an oil tank, a turbine consumption sensor is connected with a processor through a consumption signal excitation and acquisition conditioning circuit, and a temperature sensor is connected with the processor through a temperature signal excitation and acquisition conditioning circuit and an AD conversion circuit. The variable-diameter capacitive sensor and the dielectric constant compensation sensor are connected with the processor through the capacitance signal excitation and acquisition conditioning circuit and the AD conversion circuit. According to the invention, the precision and reliability of fuel oil measurement are improved, and the real-time and accurate measurement of the fuel oil level and consumption is realized.

Description

A DSP microprocessor-based aviation fuel measurement system Technical Field

[0001] This application relates to the field of airborne controller technology, and in particular to an aviation fuel measurement system based on a DSP microprocessor. Background Technology

[0002] Information such as aviation fuel consumption rate and remaining fuel level are crucial parameters for airborne engine control systems. With the rapid development of modern sensor technology, the application of various sensors in industry is becoming increasingly widespread. How to select several sensors from a large pool to accurately measure the state of the energy source (fuel), and how to design circuits based on the working principles and interface characteristics of the selected sensors to achieve real-time, high-precision detection of aviation fuel status, have always been technical challenges that countries urgently need to overcome and improve. Summary of the Invention

[0003] In view of this, this application provides an aviation fuel measurement system based on a DSP microprocessor, which at least partially solves the problems of low real-time performance, unstable accuracy, and difficulty in handling multi-sensor signal acquisition in existing fuel measurement technologies. This application conditions the fuel tank level signal and fuel supply pipeline consumption signal from the sensors into electrical signals, and then converts them into digital signals through a processor, realizing the conversion from intangible physical parameters to specific digital parameters. This achieves high-precision real-time acquisition of aviation fuel level and consumption rate, ultimately meeting the aircraft's requirements for good power response and range under different operating conditions.

[0004] This application provides an aviation fuel measurement system based on a DSP microprocessor. The system includes a fuel consumption measurement section, a fuel level measurement section, and a measurement system processor. The fuel consumption measurement section includes a turbine fuel consumption sensor and a temperature sensor, which are installed in the fuel supply pipeline. The fuel level measurement section includes a variable diameter capacitive sensor and a dielectric constant compensation sensor. The dielectric constant sensor is installed at the bottom of the fuel tank. The turbine fuel consumption sensor is connected to the measurement system processor through a fuel consumption signal excitation and acquisition conditioning circuit. The temperature sensor is connected to the measurement system processor in sequence through a temperature signal excitation and acquisition conditioning circuit and an AD conversion circuit. The variable diameter capacitive sensor and the dielectric constant compensation sensor are both connected to the measurement system processor in sequence through a capacitive signal excitation and acquisition conditioning circuit and an AD conversion circuit, respectively.

[0005] According to a specific implementation of an embodiment of this application, the capacitor signal excitation and acquisition conditioning circuit uses a balanced proportional method to acquire capacitance. The capacitor signal excitation and acquisition conditioning circuit includes, in sequence, a first excitation generation circuit, an excitation conditioning circuit, a filter circuit, and a rectifier circuit.

[0006] According to a specific implementation of an embodiment of this application, the first excitation generation circuit sequentially includes a first DDS chip, a first zero-adjustment circuit, a first proportional amplifier circuit, and an output protection circuit; the excitation conditioning circuit includes a first analog switch, a second analog switch, and a first operational amplifier. The first terminal of the first analog switch receives a gain resistor selection signal, and the second terminal of the first analog switch is connected to multiple resistors in parallel; the first terminal of the second analog switch receives a sensor selection signal, and the second terminal of the second analog switch is connected to multiple resistors in parallel, with a follower connected to the rear end of each resistor; the output terminal of the first operational amplifier is connected to the third terminal of the second analog switch and the node of the sinusoidal excitation voltage output; the non-inverting input terminal of the first operational amplifier is grounded, and the inverting input terminal of the first operational amplifier is connected to the input sinusoidal signal and connected to the third terminal of the first analog switch; the first analog switch receives control from the gain resistor selection signal and selectively connects different resistors to the feedback loop of the first operational amplifier to achieve gain adjustment; the second analog switch receives control from the sensor selection signal and switches different sensor channels to achieve multi-channel excitation.

[0007] According to a specific implementation of an embodiment of this application, the rectifier circuit includes a second operational amplifier, a third operational amplifier, multiple resistors, and multiple diodes. The non-inverting input terminal of the second operational amplifier is grounded. One end of the inverting input terminal of the second operational amplifier receives a capacitor feedback voltage signal through a sixth resistor R6. The other end of the inverting input terminal of the second operational amplifier is connected to one end of a fifth resistor R5 and the anode of a first diode D1. The output terminal of the second operational amplifier is connected to the inverting input terminal of the third operational amplifier through a second diode D2 and a seventh resistor R7. The output terminal of the second operational amplifier is also connected to the cathode of the first diode D1. The other end of the fifth resistor R5 is connected between the second diode D2 and the seventh resistor R7. The inverting input terminal of the third operational amplifier is also connected to... The circuit consists of a fourth operational amplifier, multiple resistors, and multiple capacitors. The output of the third operational amplifier is connected to the other end of the eighth resistor R8 and rectified. The non-inverting input of the third operational amplifier is grounded. The other end of the fourth resistor R4 is connected to the input of the sixth resistor R6. The filter circuit includes a fourth operational amplifier, multiple resistors, and multiple capacitors. The non-inverting input of the fourth operational amplifier is connected to the second resistor R2 and the first resistor R1 in series. The second resistor R2 and the first resistor R1 are connected to the inverting input of the fourth operational amplifier through the first capacitor C1. The second resistor R2 and the non-inverting input of the fourth operational amplifier are grounded through the second capacitor C2. The output of the fourth operational amplifier is connected to the third resistor R3. The other end of the third resistor R3 is grounded through the third capacitor C3.

[0008] According to a specific implementation of an embodiment of this application, the consumption signal excitation and acquisition conditioning circuit includes a second excitation generation circuit, a carrier demodulation circuit, and a hysteresis comparison circuit. The second excitation generation circuit provides positive and negative phase excitation signals to the turbine consumption sensor. The carrier demodulation circuit converts the envelope signal fed back by the sensor into a carrier frequency AC signal. Then, the hysteresis comparison circuit converts the carrier frequency AC signal into a square wave signal of the same frequency and inputs it to the measurement system processor for acquisition.

[0009] According to a specific implementation of an embodiment of this application, the second excitation generation circuit includes a second DDS chip, a second zero-adjustment circuit, a second proportional amplifier circuit, and an inverting proportional amplifier circuit. The measurement system processor inputs an SPI digital signal to control the second DDS chip to output an AC excitation voltage with an amplitude of 0 to 1V. This signal is sent to the second zero-adjustment circuit, which outputs a sinusoidal excitation voltage of -0.5V to +0.5V. After being filtered by a first-order active bandpass filter circuit, the voltage is sent to the back-end amplifier circuit.

[0010] According to a specific implementation of an embodiment of this application, the second zeroing circuit includes a fifth operational amplifier, a fourth capacitor C4, and multiple resistors. The inverting input terminal of the fifth operational amplifier receives a reference voltage through a tenth resistor R10 and is connected to the output terminal through a ninth resistor R9. The non-inverting input terminal of the fifth operational amplifier receives the AC excitation voltage output by the second DDS chip through an eleventh resistor R11 and is grounded through a twelfth resistor R12. The output terminal of the fifth operational amplifier outputs a sinusoidal excitation voltage through a thirteenth resistor R13, and the output terminal of the thirteenth resistor R13 is also grounded through the fourth capacitor C4.

[0011] According to a specific implementation of an embodiment of this application, the second proportional amplifier circuit includes a sixth operational amplifier and a seventh operational amplifier. The inverting input terminal of the sixth operational amplifier receives a sinusoidal excitation voltage through a fifteenth resistor R15 and is connected to the output terminal through a fourteenth resistor R14. The non-inverting input terminal of the sixth operational amplifier is grounded through a sixteenth resistor R16. The output terminal of the sixth operational amplifier is also connected to the non-inverting input terminal of the seventh operational amplifier, and the inverting input terminal of the seventh operational amplifier is connected to the output terminal.

[0012] According to a specific implementation of an embodiment of this application, the carrier demodulation circuit includes a common-mode filter circuit, a subtraction circuit, and a first low-pass filter circuit connected in sequence. The common-mode filter circuit and the first low-pass filter circuit are used to eliminate common-mode voltage and glitches in the output AC signal.

[0013] According to a specific implementation of an embodiment of this application, the temperature signal excitation and acquisition conditioning circuit includes a reference voltage source, an interface protection circuit, a second low-pass filter circuit, and a differential proportional amplifier processing circuit connected in sequence. The interface protection circuit uses a TVS diode for lightning protection and electrostatic discharge protection.

[0014] Beneficial Effects: The aviation fuel measurement system based on a DSP microprocessor in this application, through analyzing the working principles and interface characteristics of turbine consumption sensors, fuel level sensors, and PT1000 temperature sensors, designs a high-precision aviation fuel condition measurement system. An external variable resistor is used to simulate a PT1000 thermistor, and real fuel level and consumption sensors are connected to the fuel measurement system to verify the system's acquisition accuracy. The fuel measurement system can adjust parameters such as excitation signal amplitude, full-scale output voltage, and output bias voltage by adjusting the external configuration according to different sensor characteristics, thus making it suitable for various sensor models and possessing strong applicability. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 is a schematic diagram of a capacitive fuel level sensor according to an embodiment of the present invention; Figure 2 is a fuel level sensor interface connection diagram according to an embodiment of the present invention; Figure 3 is a working principle diagram of a fuel consumption sensor according to an embodiment of the present invention; Figure 4 is a measurement principle diagram of a fuel consumption and temperature sensor according to an embodiment of the present invention; Figure 5 is a framework structure diagram of an aviation fuel measurement system based on a DSP microprocessor according to an embodiment of the present invention; Figure 6 is a block diagram of the proportional capacitance measurement principle according to an embodiment of the present invention; Figure 7 is a block diagram of the first excitation generation circuit according to an embodiment of the present invention; Figure 8 is a block diagram of the excitation conditioning circuit according to an embodiment of the present invention; Figure 9 is a schematic diagram of a diode precision rectifier circuit according to an embodiment of the present invention; Figure 10 is a schematic diagram of the present invention. Figure 11 is a block diagram of a filter circuit according to an embodiment of the present invention; Figure 12 is a block diagram of a second excitation generation circuit according to an embodiment of the present invention; Figure 13 is a block diagram of a second zeroing circuit according to an embodiment of the present invention; Figure 14 is a block diagram of a second proportional amplifier circuit according to an embodiment of the present invention; Figure 15 is a block diagram of a carrier demodulation circuit and hysteresis comparison circuit according to an embodiment of the present invention; Figure 16 is a block diagram of a temperature signal excitation and acquisition conditioning circuit according to an embodiment of the present invention; Figure 17 is a graph of PT1000 resistance measurement results according to an embodiment of the present invention; Figure 18 is a graph of oil level capacitance measurement results according to an embodiment of the present invention. Detailed Implementation

[0017] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0018] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0020] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0021] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0022] This application provides an aviation fuel measurement system based on a DSP microprocessor, aiming to address the problems of low real-time performance, unstable accuracy, and difficulty in handling multi-sensor signal acquisition in existing fuel measurement technologies. First, a suitable measurement sensor is selected. Then, corresponding acquisition and conditioning hardware circuits are designed based on their working principles and interface characteristics. Finally, the design is refined through practical testing with real sensors. The designed fuel measurement system not only meets existing acquisition accuracy requirements but also enables interfacing with multiple external sensors of the same type.

[0023] Capacitive fuel level sensors and turbine-type fuel consumption sensors were selected, as these two types of sensors are used to measure fuel level and consumption rate, respectively. By inputting a certain excitation signal to the sensor, the fuel tank level signal and the fuel supply pipeline consumption signal can be converted into corresponding electrical signals, which have the advantages of high sensitivity, good reliability, and excellent accuracy. Research on fuel level and consumption measurement technology plays an important role in analyzing the real-time changes in aviation fuel conditions.

[0024] In one embodiment, an aviation fuel measurement system based on a DSP microprocessor is provided. The system includes a fuel consumption measurement section, a fuel level measurement section, and a measurement system processor. The fuel consumption measurement section includes a turbine fuel consumption sensor and a temperature sensor, which are installed in the fuel supply pipeline. The fuel level measurement section includes a variable diameter capacitive sensor and a dielectric constant compensation sensor. The dielectric constant sensor is installed at the bottom of the fuel tank. The turbine fuel consumption sensor is connected to the measurement system processor through a fuel consumption signal excitation and acquisition conditioning circuit. The temperature sensor is connected to the measurement system processor in sequence through a temperature signal excitation and acquisition conditioning circuit and an AD conversion circuit. The variable diameter capacitive sensor and the dielectric constant compensation sensor are both connected to the measurement system processor in sequence through a capacitive signal excitation and acquisition conditioning circuit and an AD conversion circuit, respectively.

[0025] In practical implementation, the working principles and external interface load characteristics of capacitive fuel level sensors and turbine fuel consumption sensors are first analyzed. Secondly, external cables are shielded to prevent interference, and electrical signals are processed through conditioning circuits to ensure normal acquisition by the microcomputer or DSP. Then, the software uses the voltage acquired by the AD converter and, according to a specific formula or lookup table, calculates the capacitance of the external fuel level sensor, the carrier frequency of the fuel consumption sensor, and the resistance of the PTC thermistor. Finally, by combining the sensor signal conversion formulas, information such as fuel consumption rate, consumption volume, and fuel level can be obtained. Combining hardware design and software calibration methods, a high-precision aviation fuel measurement system is designed, and its functionality and performance are verified using actual sensors. The specific architecture of the system includes the following:

[0026] (1) Fuel level measurement The fuel measurement system uses a capacitive fuel level sensor and a turbine flow sensor in the detection equipment. The capacitive fuel level sensor is further divided into a variable diameter capacitive fuel level sensor and a dielectric constant sensor. The variable diameter capacitive fuel level sensor consists of two coaxial cylindrical tubes (inner tube and outer tube) forming the two plates of the "capacitor", as shown in Figure 1. The variable diameter inner tube can realize that the capacitance increment changes linearly with the fuel depth.

[0027] Dielectric constant sensors are typically installed at the bottom of the fuel tank. The capacitance of their internal compensation section remains constant regardless of fuel level, but changes in fuel density and temperature are independent of these factors. External environmental factors can cause variations in the dielectric constant, which in turn alter the internal compensation capacitance of the sensor. Collecting the compensation capacitance value from the dielectric constant sensor can compensate for and correct for measurement errors in fuel level capacitance caused by changes in temperature and density.

[0028] The fuel level sensor interface is shown in Figure 2. The fuel measurement system applies a certain AC excitation signal to the capacitive sensor and the dielectric constant sensor, while simultaneously acquiring the feedback capacitance signal (AC) of the measurement section and the capacitance signal (AC) of the compensation section. The measurement system then uses a rectifier and filter circuit to convert the output AC excitation signal and the two AC feedback signals into DC voltage signals, which are then sent to the AD converter. The software, combined with standard capacitance values, calculates the compensation section capacitance value C0 and the measurement section capacitance value C using a specific formula.

[0029] (2) Fuel consumption measurement Fuel consumption measurement mainly includes two aspects: measurement of fuel consumption volume and measurement of fuel consumption mass. The fuel consumption sensor is a turbine-type fuel consumption sensor, and the temperature sensor is a PT1000 thermistor. These two sensors are installed together in the fuel supply pipeline. The working principle of the fuel consumption sensor is shown in Figure 3.

[0030] When the fuel pump draws fuel from the tank and delivers it into the fuel supply line, it causes a turbine inside the sensor to rotate. The turbine's rotation is then converted into an envelope signal by an internal signal conversion device (an inductance converter circuit). The carrier frequency of the envelope signal is linearly related to the volumetric rate of the flowing fuel (L / h). By acquiring the carrier frequency and summing the number of pulses, the fuel consumption rate (L / h) and the consumption volume (L) can be calculated.

[0031] Fuel density changes with temperature. Therefore, to accurately measure the density of a specific grade of fuel, a function of density ρ versus temperature T can be established. Based on the calculated temperature T, mathematical calculations can be performed to obtain the actual fuel density value. Combined with the volume of fuel consumed, the mass of fuel consumed can then be calculated.

[0032] The turbocharger fuel consumption sensor interface is shown in Figure 4. The fuel consumption sensor receives positive and negative excitation signals (same frequency, common mode, and peak value, but opposite phase) output from the fuel system excitation circuit. When fuel flows through the turbocharger fuel consumption sensor in the pipeline, a corresponding electrical signal is generated. The measurement system then collects and shapes the electrical signal output by the fuel consumption sensor, and finally generates a pulse square wave signal for acquisition by the ECAP port of the single-chip microcomputer.

[0033] The temperature sensor receives the voltage reference generated by the reference source circuit in the system. Then, the signal output by the sensor is converted into the voltage difference signal across the thermistor R1 by the system's internal conditioning circuit. This signal is then input to the AD conversion circuit and finally generates a serial digital signal for acquisition by the SPI port of the single-chip microcomputer.

[0034] (3) Overall Framework of Fuel Measurement System The overall framework of the fuel measurement system is shown in Figure 5. The designed fuel measurement system first uses the internal excitation circuit to send corresponding DC or AC excitation signals to the external sensor. After receiving the sensor signal, the system's internal signal processing hardware circuit conditions the feedback signals of oil temperature, oil level, and fuel consumption, and then sends them to the system processor for acquisition.

[0035] The CPU processing circuit uses a DSP as the main control chip to acquire TTL level square wave signals and digital signals after A / D conversion. The DSP analyzes the acquired data, demodulating carrier frequency, oil temperature, and oil level signals to achieve real-time monitoring of fuel consumption and fuel quantity in the fuel system.

[0036] The following embodiments provide a detailed description of each excitation and acquisition conditioning circuit.

[0037] In one embodiment, the capacitor signal excitation and acquisition conditioning circuit uses a balanced proportional method for capacitor acquisition. The capacitor signal excitation and acquisition conditioning circuit includes, in sequence, a first excitation generation circuit, an excitation conditioning circuit, a filter circuit, and a rectifier circuit.

[0038] The most direct purpose of the fuel level signal acquisition module is to measure the capacitance values ​​of the measuring and compensation sections within the capacitive fuel level sensor and dielectric constant sensor. The capacitance values ​​of both the measuring and compensation sections are measured within the range of 20pF to 450pF.

[0039] The capacitance is acquired using a balanced proportional method. Figure 6 shows the block diagram of the balanced proportional method for measuring capacitance. The capacitance signal acquisition circuit mainly includes an excitation circuit, a proportional amplifier circuit, and a filter and rectifier circuit. The capacitance value of the capacitor under test can be calculated using the proportional method by using the capacitance value of the standard capacitor and the two calculated DC voltage values. The basic formula for the proportional method of capacitance acquisition is as follows: Ub / Ua=Cb / Ca (1) where Ca is the standard capacitance value, Cb is the capacitance value to be measured, Ua is the excitation voltage acquisition value, and Ub is the sensor feedback voltage acquisition value.

[0040] Further, referring to Figures 7 and 8, the first excitation generation circuit sequentially includes a first DDS chip, a first zero-adjustment circuit, a first proportional amplifier circuit, and an output protection circuit; the excitation conditioning circuit includes a first analog switch, a second analog switch, and a first operational amplifier. The first terminal of the first analog switch receives a gain resistor selection signal, and the second terminal of the first analog switch is connected to multiple resistors in parallel; the first terminal of the second analog switch receives a sensor selection signal, and the second terminal of the second analog switch is connected to multiple resistors in parallel, with a follower connected to the rear end of each resistor; the output terminal of the first operational amplifier is connected to the third terminal of the second analog switch and the node of the sinusoidal excitation voltage output; the non-inverting input terminal of the first operational amplifier is grounded, and the inverting input terminal of the first operational amplifier is connected to the input sinusoidal signal and connected to the third terminal of the first analog switch; the first analog switch receives control from the gain resistor selection signal and selectively connects different resistors to the feedback loop of the first operational amplifier to achieve gain adjustment; the second analog switch receives control from the sensor selection signal and switches different sensor channels to achieve multi-channel excitation.

[0041] In practice, the excitation sinusoidal signal is generated by the first DDS chip, using the domestically produced JDDS9851 direct digital frequency synthesizer chip. The amplitude of the original excitation sinusoidal wave is 0V to 1V, which is converted into a sinusoidal signal of -1V to 0V by an inverting proportional operational amplifier circuit. Then, it is converted into a common-mode sinusoidal excitation signal of 0V and amplitude of -1V to 1V by the first zero-adjustment circuit and the first proportional amplifier circuit.

[0042] By switching the corresponding feedback gain resistor using a first analog switch, graded excitation outputs are achieved for different ranges of the capacitance value to be measured. A second analog switch transmits the same excitation signal to multiple external level sensors, preventing coupling and interference caused by sending the same excitation signal to different sensors.

[0043] The principle block diagram of the excitation conditioning circuit is shown in Figure 8. The capacitor under test can be divided into three measurement ranges: G1: 20pF~100pF; G2: 100pF~200pF; G3: 200pF~450pF. If the standard capacitor Ca is selected as 100pF, then the conversion factor K between the capacitor under test Cb and the standard capacitor Ca is: (2) According to formula (1), Ub = KUa. Since the maximum analog input of the AD conversion circuit is 10V, in order to ensure that the excitation voltage acquisition value Ua and the feedback voltage acquisition value Ub do not exceed 10V, and Ub should be as large as possible to ensure the AD acquisition accuracy of Ub, the peak values ​​of the excitation voltage Ua under different ranges are as follows: (3) In the above formula, the three-level control signals G1 to G3 are used to switch the corresponding gain resistors into the excitation amplifier circuit and generate the excitation voltage Ua under the three levels, so that the peak value of Ub under different levels can be obtained: (4) When the capacitance value of the capacitor under test is at its maximum within different measurement ranges, Ub is uniformly set to 9V to leave a margin by reasonably selecting the gain resistor. In the logic, the range is usually adjusted to G3 first to ensure that no capacitance value of the capacitor under test within the total measurement range will cause the feedback voltage acquisition value Ub to exceed the limit. The basis for range switching depends on whether the value of Ub exceeds the theoretical range in the current range. If the value of Ub is lower than the lower limit in the current range, the range is downgraded; if the value of Ub exceeds the upper limit, the range is upgraded. The working principle of setting more ranges is the same as above.

[0044] Further, referring to Figure 9, the rectifier circuit includes a second operational amplifier, a third operational amplifier, multiple resistors, and multiple diodes. The non-inverting input of the second operational amplifier is grounded. One end of the inverting input of the second operational amplifier receives the capacitor feedback voltage signal through the sixth resistor R6. The other end of the inverting input of the second operational amplifier is connected to one end of the fifth resistor R5 and the anode of the first diode D1. The output of the second operational amplifier is connected to the inverting input of the third operational amplifier through the second diode D2 and the seventh resistor R7. The output of the second operational amplifier is also connected to the cathode of the first diode D1. The other end of the fifth resistor R5 is connected between the second diode D2 and the seventh resistor R7. The inverting input of the third operational amplifier is also connected to one end of the eighth resistor R8 and one end of the fourth resistor R4. The output of the third operational amplifier is connected to the other end of the eighth resistor R8 and rectified for output. The non-inverting input of the third operational amplifier is grounded. The other end of the fourth resistor R4 is connected to the input of the sixth resistor R6.

[0045] Referring to Figure 10, the filter circuit includes a fourth operational amplifier, multiple resistors, and multiple capacitors. The non-inverting input of the fourth operational amplifier is connected to a second resistor R2 and a first resistor R1 connected in series. The second resistor R2 and the first resistor R1 are connected to the inverting input of the fourth operational amplifier through a first capacitor C1. The second resistor R2 and the non-inverting input of the fourth operational amplifier are grounded through a second capacitor C2. The output of the fourth operational amplifier is connected to a third resistor R3. The other end of the third resistor R3 is grounded through a third capacitor C3.

[0046] In practical implementation, the capacitor acquisition circuit primarily aims to ensure the accuracy of Ub / Ua, rather than pursuing the accuracy of acquiring a single voltage of Ub or Ua. Furthermore, the fuel measurement system has certain requirements for the real-time performance of fuel level measurement; therefore, a diode precision rectifier circuit is selected. The principle of the diode precision rectifier circuit is shown in Figure 9.

[0047] After rectification, the output signal should be the positive half-axis full-wave signal of the input AC signal. The second-order Butterworth active filter circuit, combined with the first-order active filter circuit, converts the AC signal into a DC signal and filters out the DC voltage ripple as much as possible. The rectified filter circuit is shown in Figure 10.

[0048] Given R1=R2=22kΩ and C1=C2=3.3nF, the cutoff frequency of the second-order low-pass filter is: (5) Taking R3=22kΩ and C3=33nF, the cutoff frequency of the last-order low-pass filter is: (6) The signal after rectification and filtering has been converted into a DC voltage value. The excitation feedback voltage and capacitor feedback voltage can be acquired simultaneously through two AD acquisition channels, and the acquired digital values ​​are sent to a single-chip microcomputer for calculation.

[0049] In one embodiment, referring to FIG11, the consumption signal excitation and acquisition conditioning circuit includes a second excitation generation circuit, a carrier demodulation circuit, and a hysteresis comparison circuit. The second excitation generation circuit provides positive and negative phase excitation signals to the turbine consumption sensor. The carrier demodulation circuit converts the envelope signal fed back by the sensor into a carrier frequency AC signal. The hysteresis comparison circuit then converts the carrier frequency AC signal into a square wave signal of the same frequency, which is input to the measurement system processor for acquisition.

[0050] Furthermore, referring to Figure 12, the second excitation generation circuit includes a second DDS chip, a second zero-adjustment circuit, a second proportional amplifier circuit, and an inverting proportional amplifier circuit. The measurement system processor inputs an SPI digital signal to control the second DDS chip to output an AC excitation voltage with an amplitude of 0 to 1V. This signal is sent to the second zero-adjustment circuit, which outputs a sinusoidal excitation voltage of -0.5V to +0.5V. After being filtered by a first-order active bandpass filter circuit, the voltage is sent to the back-end amplifier circuit.

[0051] Furthermore, referring to Figure 13, the second zeroing circuit includes a fifth operational amplifier, a fourth capacitor C4, and multiple resistors. The inverting input of the fifth operational amplifier receives a reference voltage through the tenth resistor R10 and is connected to the output through the ninth resistor R9. The non-inverting input of the fifth operational amplifier receives the AC excitation voltage output by the second DDS chip through the eleventh resistor R11 and is grounded through the twelfth resistor R12. The output of the fifth operational amplifier outputs a sinusoidal excitation voltage through the thirteenth resistor R13, and the output of the thirteenth resistor R13 is also grounded through the fourth capacitor C4.

[0052] In practical implementation, R13 is set to 10kΩ, C4 to 2.2nF, and the approximate cutoff frequency of the low-pass filter is: (7) The sinusoidal AC signal input from the front end of the proportional amplifier circuit, ranging from -0.5V to +0.5V, needs to be amplified by an operational amplifier circuit to increase the amplitude to 10.5V (7.42Vrms). The gain resistors are selected as 1kΩ and 21kΩ, and the gain factor is 20.5. The principle of the amplifier circuit is shown in Figure 14.

[0053] Furthermore, as shown in Figure 14, the second proportional amplifier circuit includes a sixth operational amplifier and a seventh operational amplifier. The inverting input terminal of the sixth operational amplifier receives a sinusoidal excitation voltage through the fifteenth resistor R15 and is connected to the output terminal through the fourteenth resistor R14. The non-inverting input terminal of the sixth operational amplifier is grounded through the sixteenth resistor R16. The output terminal of the sixth operational amplifier is also connected to the non-inverting input terminal of the seventh operational amplifier, and the inverting input terminal of the seventh operational amplifier is connected to the output terminal.

[0054] Furthermore, referring to Figure 15, the carrier demodulation circuit includes a common-mode filter circuit, a subtraction circuit, and a first low-pass filter circuit connected in sequence. The common-mode filter circuit and the first low-pass filter circuit are used to eliminate common-mode voltage and glitches in the output AC signal.

[0055] After the carrier demodulation circuit converts the envelope signal into a carrier frequency AC signal, it sends the signal to the hysteresis comparator circuit, which outputs a square wave signal of the same frequency for acquisition.

[0056] The carrier demodulation circuit demodulates and converts the envelope signal fed back from the fuel consumption sensor. This process involves low-pass filtering, common-mode filtering, differential operations, and hysteresis comparison. Common-mode filtering and low-pass filtering are used to eliminate common-mode voltage and output AC signal glitches, preventing external interference from affecting the acquisition accuracy. The cutoff frequency of the first-order low-pass filter in the subsequent stage is: (8) The carrier frequency AC signal will be input into the subsequent hysteresis comparator for waveform conversion. The resistor configuration of the positive feedback hysteresis comparator can be calculated to reduce the influence of external interference on the electrical pulse square wave signal within a certain range. At this time, an electrical pulse square wave signal with the same frequency as the carrier AC signal can be output.

[0057] In one embodiment, the temperature signal excitation and acquisition conditioning circuit includes a reference voltage source, an interface protection circuit, a second low-pass filter circuit, and a differential proportional amplifier processing circuit connected in sequence. The interface protection circuit uses a TVS diode for lightning protection and electrostatic discharge protection.

[0058] In practical implementation, the PT1000 is a thermistor, requiring a resistance range of 800–1400Ω, corresponding to a detection temperature range of -50℃ to 100℃. The circuit consists of an interface protection circuit, a second low-pass filter circuit, and a differential proportional amplifier processing circuit. The thermistor sensor receives a 10V reference source from the receiving system, which is then divided by a 1K resistor within the functional module. The voltage difference signal passes through the interface protection circuit, the RC low-pass filter circuit, and the differential proportional amplifier processing circuit before being sent to the A / D conversion circuit. The interface protection circuit uses a TVS diode for lightning and electrostatic discharge protection.

[0059] The reference voltage source is powered independently, with an output voltage ripple within ±10mV. To ensure the acquisition accuracy of the thermistor acquisition circuit, the reference voltage source is divided and then sent to the AD converter for acquisition, achieving an acquisition accuracy within 0.3%. Simultaneously, software correction for measurement errors is used in the processor. The hardware circuit employs an RC low-pass filter with a cutoff frequency of approximately 7Hz, effectively filtering out high-frequency interference from the thermistor sensor signal.

[0060] The test results of the aviation fuel measurement system based on the DSP microprocessor of this application are shown in Table 1, Figure 17, and Figure 18. Table 1 shows that the system acquired envelope signals from five different carrier frequencies output by the fuel consumption sensor, and compared the obtained carrier frequency values ​​with those measured by a dedicated instrument. The largest frequency acquisition offset was -0.034 Hz, while the largest average error was only 0.0056 Hz. The acquisition frequency accuracy meets the error requirement range of ±0.5%, or ±0.05 Hz.

[0061] Table 1 Consumption Signal Measurement Record Table

[0062] As shown in Figure 17, the PT1000 resistance measurement data indicates that the system measures external variable resistors with resistance values ​​ranging from 0.8kΩ to 1.6kΩ, increasing in 0.1kΩ steps. The maximum resistance measurement error is -4.5Ω, and the measurement accuracy meets the requirement of ±0.5%, or ±8Ω.

[0063] As shown in Figure 18, the oil level capacitance measurement data indicates that the system collects 38 sets of AC oil level signals ranging from 10.28pF to 436.19pF from the oil level sensor, calculates and records capacitance values ​​ranging from 10.55pF to 435.08pF. The maximum capacitance acquisition error is -1.6pF, and the acquisition accuracy meets the error range requirement of ±5pF.

[0064] The embodiments provided by this invention are applicable to the field of airborne controllers, enabling real-time monitoring of aviation fuel consumption rate and remaining fuel level during aircraft flight. This provides crucial information regarding power reserves and range for manned or unmanned aircraft flight strategies. This application designs a high-precision aviation fuel status measurement system by analyzing the working principles and interface characteristics of turbine consumption sensors, fuel level sensors, and PT1000 temperature sensors. An external variable resistor is used to simulate a PT1000 thermistor, and real fuel level and consumption sensors are connected to the fuel measurement system, ensuring the system's acquisition accuracy. The fuel measurement system can adjust parameters such as excitation signal amplitude, full-scale output voltage, and output bias voltage by adjusting the external configuration according to different sensor characteristics, making it suitable for various sensor models and highly applicable.

[0065] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An aviation fuel measurement system based on a DSP microprocessor, characterized in that, The system includes a consumption measurement section, an oil level measurement section, and a measurement system processor. The consumption measurement section includes a turbine consumption sensor and a temperature sensor, which are installed in the oil supply pipeline. The oil level measurement section includes a variable diameter capacitive sensor and a dielectric constant compensation sensor. The dielectric constant sensor is installed at the bottom of the oil tank. The turbine consumption sensor is connected to the measurement system processor through a consumption signal excitation and acquisition conditioning circuit. The temperature sensor is connected to the measurement system processor in sequence through a temperature signal excitation and acquisition conditioning circuit and an AD conversion circuit. The variable diameter capacitive sensor and the dielectric constant compensation sensor are both connected to the measurement system processor in sequence through a capacitive signal excitation and acquisition conditioning circuit and an AD conversion circuit, respectively.

2. The aviation fuel measurement system based on a DSP microprocessor according to claim 1, characterized in that, The capacitor signal excitation and acquisition conditioning circuit uses a balanced proportional method for capacitor acquisition. The capacitor signal excitation and acquisition conditioning circuit includes, in sequence, a first excitation generation circuit, an excitation conditioning circuit, a filter circuit, and a rectifier circuit.

3. The aviation fuel measurement system based on a DSP microprocessor according to claim 2, characterized in that, The first excitation generation circuit sequentially includes a first DDS chip, a first zero-adjustment circuit, a first proportional amplifier circuit, and an output protection circuit. The excitation conditioning circuit includes a first analog switch, a second analog switch, and a first operational amplifier. The first terminal of the first analog switch receives a gain resistor selection signal, and the second terminal of the first analog switch is connected to multiple resistors in parallel. The first terminal of the second analog switch receives a sensor selection signal, and the second terminal of the second analog switch is connected to multiple resistors in parallel, with a follower connected to the rear end of each resistor. The output terminal of the first operational amplifier is connected to the third terminal of the second analog switch and the node of the sinusoidal excitation voltage output. The non-inverting input terminal of the first operational amplifier is grounded, and the inverting input terminal of the first operational amplifier is connected to the input sinusoidal signal and connected to the third terminal of the first analog switch. The first analog switch receives control from the gain resistor selection signal and selectively connects different resistors to the feedback loop of the first operational amplifier to achieve gain adjustment. The second analog switch receives control from the sensor selection signal and switches different sensor channels to achieve multi-channel excitation.

4. The aviation fuel measurement system based on a DSP microprocessor according to claim 2, characterized in that, The rectifier circuit includes a second operational amplifier, a third operational amplifier, multiple resistors, and multiple diodes. The non-inverting input of the second operational amplifier is grounded. One end of the inverting input of the second operational amplifier receives the capacitor feedback voltage signal through the sixth resistor R6. The other end of the inverting input of the second operational amplifier is connected to one end of the fifth resistor R5 and the anode of the first diode D1. The output of the second operational amplifier is connected to the inverting input of the third operational amplifier through the second diode D2 and the seventh resistor R7. The output of the second operational amplifier is also connected to the cathode of the first diode D1. The other end of the fifth resistor R5 is connected between the second diode D2 and the seventh resistor R7. The inverting input of the third operational amplifier is also connected to one end of the eighth resistor R8. The output of the third operational amplifier is connected to one end of the fourth resistor R4 and the other end of the eighth resistor R8 for rectification. The non-inverting input of the third operational amplifier is grounded. The other end of the fourth resistor R4 is connected to the input of the sixth resistor R6. The filter circuit includes a fourth operational amplifier, multiple resistors, and multiple capacitors. The non-inverting input of the fourth operational amplifier is connected to the second resistor R2 and the first resistor R1 in series. The second resistor R2 and the first resistor R1 are connected to the inverting input of the fourth operational amplifier through the first capacitor C1. The second resistor R2 and the non-inverting input of the fourth operational amplifier are grounded through the second capacitor C2. The output of the fourth operational amplifier is connected to the third resistor R3. The other end of the third resistor R3 is grounded through the third capacitor C3.

5. The aviation fuel measurement system based on a DSP microprocessor according to claim 1, characterized in that, The consumption signal excitation and acquisition conditioning circuit includes a second excitation generation circuit, a carrier demodulation circuit, and a hysteresis comparison circuit. The second excitation generation circuit provides positive and negative phase excitation signals to the turbine consumption sensor. The carrier demodulation circuit converts the envelope signal fed back by the sensor into a carrier frequency AC signal. Then, the hysteresis comparison circuit converts the carrier frequency AC signal into a square wave signal of the same frequency, which is then input to the measurement system processor for acquisition.

6. The aviation fuel measurement system based on a DSP microprocessor according to claim 5, characterized in that, The second excitation generation circuit includes a second DDS chip, a second zero-adjustment circuit, a second proportional amplifier circuit, and an inverting proportional amplifier circuit. The measurement system processor inputs an SPI digital signal to control the second DDS chip to output an AC excitation voltage with an amplitude of 0 to 1V. This signal is sent to the second zero-adjustment circuit, which outputs a sinusoidal excitation voltage of -0.5V to +0.5V. After being filtered by a first-order active bandpass filter circuit, the voltage is sent to the back-end amplifier circuit.

7. The aviation fuel measurement system based on a DSP microprocessor according to claim 6, characterized in that, The second zeroing circuit includes a fifth operational amplifier, a fourth capacitor C4, and multiple resistors. The inverting input of the fifth operational amplifier receives the reference voltage through the tenth resistor R10 and is connected to the output through the ninth resistor R9. The non-inverting input of the fifth operational amplifier receives the AC excitation voltage output by the second DDS chip through the eleventh resistor R11 and is grounded through the twelfth resistor R12. The output of the fifth operational amplifier outputs a sinusoidal excitation voltage through the thirteenth resistor R13, and the output of the thirteenth resistor R13 is also grounded through the fourth capacitor C4.

8. The aviation fuel measurement system based on a DSP microprocessor according to claim 7, characterized in that, The second proportional amplifier circuit includes a sixth operational amplifier and a seventh operational amplifier. The inverting input of the sixth operational amplifier receives a sinusoidal excitation voltage through the fifteenth resistor R15 and is connected to the output through the fourteenth resistor R14. The non-inverting input of the sixth operational amplifier is grounded through the sixteenth resistor R16. The output of the sixth operational amplifier is also connected to the non-inverting input of the seventh operational amplifier, and the inverting input of the seventh operational amplifier is connected to the output.

9. The aviation fuel measurement system based on a DSP microprocessor according to claim 5, characterized in that, The carrier demodulation circuit includes a common-mode filter circuit, a subtraction circuit, and a first low-pass filter circuit connected in sequence. The common-mode filter circuit and the first low-pass filter circuit are used to eliminate common-mode voltage and glitches in the output AC signal.

10. The aviation fuel measurement system based on a DSP microprocessor according to claim 1, characterized in that, The temperature signal excitation and acquisition conditioning circuit includes a reference voltage source, an interface protection circuit, a second low-pass filter circuit, and a differential proportional amplifier processing circuit connected in sequence. The interface protection circuit uses a TVS diode for lightning protection and electrostatic discharge protection.

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