Aviation fuel oil measuring system and method based on square wave excitation

Abstract

The invention relates to the technical field of aviation fuel measurement, and discloses an aviation fuel measurement system and method based on square wave excitation, the system comprises a fuel sensor, a processor unit and a proportional amplification unit, the proportional amplification unit comprises a feedback capacitor, a grounding resistor and an operational amplifier, and the system also comprises a third A / D conversion unit and a second A / D conversion unit. The real-time value of the fuel sensor is calculated by reading the acquisition results of the second A / D conversion unit and the third A / D conversion unit by utilizing a square wave excitation signal sent by the processor unit according to the acquisition results of the second A / D conversion unit and the third A / D conversion unit, so that the high-precision measurement of the fuel quantity is realized; the measuring system is simple in structure, simple and convenient in operation process, low in cost and high in reliability.

Description

Technical Field

[0001] The invention relates to the technical field of aviation fuel measurement, and discloses an aviation fuel measurement system and method based on square wave excitation. Background Art

[0002] Accurate collection of aviation fuel can reduce the amount of spare fuel when the aircraft takes off, provide a more accurate reference for aircraft tactical formulation, and is of great significance to various aircraft models in the aviation field. Domestic and foreign aircraft fuel level measurement technologies mainly include float type, capacitance type, ultrasonic level type, optical fiber level type and magnetostrictive type. At present, the capacitive level sensor still occupies a dominant position. The commonly used measurement method is the AC proportional method, that is, the measured capacitance is measured by the proportional relationship between the excitation voltage, feedback voltage, the measured capacitance and the reference capacitance. The traditional AC proportional method requires the setting of a special high-precision excitation source. Both the excitation voltage and the feedback voltage need to be converted into an average value through a high-precision rectifier circuit to replace the real-time value. The establishment process is slow, the real-time performance is poor, the hardware cost is high, and the control is complex. Therefore, it is of great significance to study the new aviation fuel collection system engineering with high real-time, low cost and simple control. Summary of the invention

[0003] The purpose of the present invention is to provide an aviation fuel measurement system and method based on square wave excitation, which realizes high-precision measurement of fuel quantity, and the measurement system has a simple structure, a simple calculation process, low cost and high reliability.

[0004] In order to achieve the above technical effects, the technical solution adopted by the present invention is:

[0005] An aviation fuel measurement system based on square wave excitation, comprising:

[0006] A fuel sensor including a capacitive sensing unit;

[0007] A processor unit, for generating a square wave excitation signal and transmitting the square wave excitation signal to an input end of the fuel sensor;

[0008] A proportional amplification unit, the proportional amplification unit comprising a feedback capacitor, a grounding resistor and an operational amplifier, the output end of the operational amplifier is connected to the negative input end of the operational amplifier through the feedback capacitor, the negative input end of the operational amplifier is connected to the fuel sensor, and the positive input end of the operational amplifier is grounded through the grounding resistor;

[0009] A third A / D conversion unit, used for collecting the output voltage of the proportional amplification unit and transmitting it to the processor unit;

[0010] The second A / D conversion unit is used to collect the output voltage of the square wave excitation signal and transmit it to the processing unit.

[0011] Furthermore, a power amplification unit is provided between the processor unit and the fuel sensor.

[0012] Furthermore, it also includes a temperature measuring unit, which is used to measure the temperature of the feedback capacitor and transmit the collected temperature signal to the processor unit.

[0013] Furthermore, it also includes a current indicating unit for measuring the output current of the square wave excitation signal, and the current indicating unit is communicatively connected to the processor unit through the first A / D conversion unit; the processor unit is also used to disconnect the square wave excitation signal when the output current of the square wave excitation signal reaches a preset threshold.

[0014] In order to achieve the above technical effects, the present invention also provides an aviation fuel measurement method based on square wave excitation. The method is based on the aviation fuel measurement system and includes:

[0015] After the aviation fuel measurement system is powered on, when the processor unit does not send a square wave excitation signal, a zero level calibration is performed in advance to read the first voltage value of the second A / D conversion unit and the second voltage value of the third A / D conversion unit;

[0016] The processor unit sends a square wave excitation signal, and reads the excitation voltage value of the second A / D conversion unit and the feedback voltage value of the third A / D conversion unit;

[0017] The real-time value of the fuel sensor is calculated according to the first voltage value, the second voltage value, the excitation voltage value and the feedback voltage value.

[0018] Furthermore, the fuel sensor C x Real-time value through formula The analysis shows that V A / D2 is the excitation voltage value, V A / D20 is the first voltage value, V A / D3 is the feedback voltage value, V A / D20 is the second voltage value, C f is the capacitance value of the feedback capacitor.

[0019] Further, the method of sending a square wave excitation signal from the processor unit and reading the excitation voltage value of the second A / D conversion unit and the feedback voltage value of the third A / D conversion unit includes:

[0020] The processor unit generates a square wave excitation signal and simultaneously generates a frequency-multiplied signal A having a frequency twice that of the square wave excitation signal, wherein the falling edge of the frequency-multiplied signal A is aligned with the rising edge of the square wave excitation signal;

[0021] When the square wave excitation signal is at a high level and the double frequency signal A is at a rising edge, the second A / D conversion unit is triggered to sample, and the recorded results are data A1, data A2, ..., data A n , A n represents the square wave excitation signal output voltage value obtained by the second A / D conversion unit at the nth sampling;

[0022] When the processor unit detects that the square wave feedback signal is at a rising edge, it simultaneously generates a frequency-multiplied signal B having a frequency twice that of the square wave excitation signal, and the falling edge of the frequency-multiplied signal B is aligned with the rising edge of the square wave signal;

[0023] When the square wave feedback signal is at a high level and the frequency-multiplied signal B is at a rising edge, the third A / D conversion unit is triggered to sample, and the recorded results are data B1, data B2, ..., data B n , B n It represents the output voltage value of the proportional amplification unit obtained by the nth sampling of the third A / D conversion unit.

[0024] Further, a temperature measurement unit is provided near the feedback capacitor to measure the temperature of the feedback capacitor, and the collected temperature signal is transmitted to the processor unit;

[0025] The processor unit obtains the real-time temperature value of the temperature measurement unit according to C' f =C f0 ·[1+α(T t -T0)] to compensate the feedback capacitance value, where C′ f The feedback capacitor at temperature T t The capacitance under, C f0 is the capacitance of the feedback capacitor at the reference temperature T0, α is the temperature coefficient of the feedback capacitor;

[0026] Fuel sensor C x Real-time value through formula The analysis shows that V A / D2 is the excitation voltage value, V A / D20 is the first voltage value, V A / D3 is the feedback voltage value, V A / D20 is the second voltage value.

[0027] Furthermore, the square wave excitation signal has symmetrical amplitudes about the time axis, and a high level duty cycle of the square wave excitation signal is not less than 50%.

[0028] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts a square wave excitation signal emitted by a processor unit, reads the acquisition results of the second A / D conversion unit and the third A / D conversion unit, and calculates the real-time value of the fuel sensor according to the acquisition results of the second A / D conversion unit and the third A / D conversion unit, thereby realizing high-precision measurement of the fuel quantity, and the measurement system has a simple structure, a simple calculation process, low cost and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural block diagram of the aviation fuel measurement system based on square wave excitation in embodiment 1 or 2;

[0030] Figure 2 This is a sampling timing diagram of the square wave excitation signal and the square wave feedback signal in Example 2. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the embodiments and drawings. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0032] Example 1

[0033] See also Figure 1 , an aviation fuel measurement system based on square wave excitation, characterized in that it includes:

[0034] A fuel sensor including a capacitive sensing unit;

[0035] A processor unit, for generating a square wave excitation signal and transmitting the square wave excitation signal to an input end of the fuel sensor;

[0036] A proportional amplification unit, the proportional amplification unit comprising a feedback capacitor, a grounding resistor and an operational amplifier, the output end of the operational amplifier is connected to the negative input end of the operational amplifier through the feedback capacitor, the negative input end of the operational amplifier is connected to the fuel sensor, and the positive input end of the operational amplifier is grounded through the grounding resistor;

[0037] A third A / D conversion unit, used for collecting the output voltage of the proportional amplification unit and transmitting it to the processor unit;

[0038] The second A / D conversion unit is used to collect the output voltage of the square wave excitation signal and transmit it to the processing unit.

[0039] In this embodiment, a square wave excitation source is used to replace the traditional sinusoidal wave excitation source, thereby avoiding the high hardware cost and complex control defects of the traditional dedicated high-precision sinusoidal wave excitation source, eliminating the high-precision rectifier circuit in the traditional AC proportional amplification method and the measurement error caused thereby, and having a faster dynamic response speed and a wider adaptability range. Combined with algorithms such as system error correction and temperature compensation correction, the system acquisition accuracy is higher, thereby obtaining a low-cost, high real-time, high-reliability, and high-precision new aviation fuel quantity collection system, which is of great significance for improving the aircraft fuel measurement accuracy, reducing the aircraft fuel dead oil reserve, reducing the aircraft weight, and improving the aircraft maneuverability.

[0040] In this embodiment, the specific process of the aviation fuel measurement method based on square wave excitation includes:

[0041] After the aviation fuel measurement system is powered on, when the processor unit does not send a square wave excitation signal, a zero level calibration is performed in advance to read the first voltage value of the second A / D conversion unit and the second voltage value of the third A / D conversion unit;

[0042] The processor unit sends a square wave excitation signal, and reads the excitation voltage value of the second A / D conversion unit and the feedback voltage value of the third A / D conversion unit;

[0043] The real-time value of the fuel sensor is calculated according to the first voltage value, the second voltage value, the excitation voltage value and the feedback voltage value. x By formula Where V A / d2 is the excitation voltage value, V A / d20 is the first voltage value, V A / D3 is the feedback voltage value, V A / D20 is the second voltage value, C f is the capacitance value of the feedback capacitor.

[0044] The aviation fuel measurement system in this embodiment also includes a current indicating unit for measuring the output current of the square wave excitation signal. The current indicating unit is communicatively connected to the processor unit via the first A / D conversion unit. The processor unit is also used to disconnect the square wave excitation signal when the output current of the square wave excitation signal reaches a preset threshold value, and can perform output disconnection locking, and at the same time set a circuit overcurrent trip signal to play a role in intelligent protection.

[0045] In this embodiment, the first A / D conversion unit, the second A / D conversion unit, and the third A / D conversion unit can be independent A / D conversion units, or different channels of the same A / D conversion unit with multiple channels. When the same A / D conversion unit with multiple channels is used, the first A / D conversion unit, the second A / D conversion unit, and the third A / D conversion unit reuse the data bus and the control bus.

[0046] Example 2

[0047] An aviation fuel measurement method based on square wave excitation, comprising:

[0048] Step 1: After the aviation fuel measurement system is powered on, when the processor unit does not send a square wave excitation signal, a zero level calibration is performed in advance to read the first voltage value V of the second A / D conversion unit. A / D20 , and the second voltage value V of the third A / D conversion unit A / D30 ;

[0049] See also Figure 1 In this embodiment, the aviation fuel measurement system includes: a processor unit, a power amplifier unit, a current indication unit, a fuel sensor C x , a proportional amplification unit, a temperature measurement unit, a first A / D conversion unit, a second A / D conversion unit, a third A / D conversion unit and a fourth A / D conversion unit; the proportional amplification unit includes a feedback capacitor C f , a grounding resistor R0 and an operational amplifier, the output of the operational amplifier is connected to the feedback capacitor C f The negative input terminal of the operational amplifier is connected to the negative input terminal of the fuel sensor C x The positive input terminal of the operational amplifier is connected to ground through a grounding resistor R0, where:

[0050] The processor unit is connected to the power amplifier unit, the first A / D conversion unit, the second A / D conversion unit, the third A / D conversion unit and the fourth A / D conversion unit at the same time; the output of the proportional amplifier unit is connected to the fuel sensor C through the current indication unit x The input of the first A / D conversion unit is connected to the overcurrent output of the current indicating unit; the input of the second A / D conversion unit is connected to the output of the current indicating unit; the input of the third A / D conversion unit is connected to the output of the proportional amplification unit; the input of the fourth A / D conversion unit is connected to the output of the temperature measurement unit for converting the temperature signal into a corresponding processing signal; the temperature measurement unit is installed close to the feedback capacitor C f ; The feedback capacitor C f Select high-precision and low-temperature drift coefficient capacitors.

[0051] Step 2: The processor unit sends a square wave excitation signal, and reads the excitation voltage value of the second A / D conversion unit and the feedback voltage value of the third A / D conversion unit;

[0052] like Figure 2 As shown, in this embodiment, the steps of the method for collecting the excitation voltage and the feedback voltage are as follows:

[0053] 2.1 The processor unit generates a square wave excitation signal and simultaneously generates a frequency-multiplied signal A having a frequency twice that of the square wave excitation signal, wherein the falling edge of the frequency-multiplied signal A is aligned with the rising edge of the square wave excitation signal;

[0054] 2.2 When the square wave excitation signal is at a high level and the double frequency signal A is at a rising edge, the second A / D conversion unit is triggered to sample, and the recorded results are data A1, data A2, ..., data A n , A n represents the square wave excitation signal output voltage value obtained by the second A / D conversion unit at the nth sampling;

[0055] 2.3 When the processor unit detects that the square wave feedback signal is at a rising edge, it simultaneously generates a frequency-doubled signal B having a frequency twice that of the square wave excitation signal, and the falling edge of the frequency-doubled signal B is aligned with the rising edge of the square wave signal;

[0056] 2.4 When the square wave feedback signal is at a high level and the frequency-multiplied signal B is at a rising edge, the third A / D conversion unit is triggered to sample, and the recorded results are data B1, data B2, ..., data B n , B n represents the output voltage value of the proportional amplification unit obtained by the nth sampling of the third A / D conversion unit;

[0057] 2.5 Calculate the square wave excitation voltage V A / D2,n =A n -V A / D20 , the feedback voltage V A / D3,n =B n -V A / D20 ;

[0058] 2.6 Fuel sensor C x Real-time value

[0059] In this embodiment, 2.2 and 2.4 adopt double frequency of the excitation signal and the feedback signal, and the sampling time selects the rising edge of the valid signal and the doubled frequency signal. At this time, the voltage signal amplitude change rate is the lowest and the signal stability is the highest, which helps to improve the system's anti-interference ability, improve the system acquisition accuracy, and simplify the software and hardware design.

[0060] The frequency and amplitude of the square wave excitation signal emitted by the processor unit can be continuously adjusted. The square wave excitation signal is symmetrical about the time axis, and the high level duty cycle of the square wave excitation signal is not less than 50%. x Capacitance acquisition needs to be dynamically configured. For example, in this embodiment, the amplitude of the square wave excitation signal can be based on the capacitance sensor C x The acquisition result is adjusted, and the adjustment method is: to ensure that the square wave feedback signal acquisition result is within the range of 1 / 3 to 2 / 3 of the acquisition range of the third A / D conversion unit to improve the acquisition accuracy of the third A / D conversion unit.

[0061] It should be noted that, in this embodiment, except for the fuel sensor C x In addition, in this embodiment, a temperature measurement unit (i.e., a temperature sensor) may be provided near the feedback capacitor to measure the temperature of the feedback capacitor and transmit the collected temperature signal to the processor unit to control the feedback capacitor C. f Temperature compensation calculation. The processor unit can calculate the compensated feedback capacitance value C' based on the real-time temperature value obtained by the temperature measurement unit. f =C f0 ·[1+α(T t -T0)], where C′ f The feedback capacitor at temperature T t The capacitance under, C f0 is the capacitance of the feedback capacitor at the reference temperature T0, and α is the temperature coefficient of the feedback capacitor.

[0062] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An aviation fuel measurement system based on square wave excitation, characterized in that: include: A fuel sensor including a capacitive sensing unit; A processor unit, for generating a square wave excitation signal and transmitting the square wave excitation signal to an input end of the fuel sensor; A proportional amplification unit, the proportional amplification unit comprising a feedback capacitor, a grounding resistor and an operational amplifier, the output end of the operational amplifier is connected to the negative input end of the operational amplifier through the feedback capacitor, the negative input end of the operational amplifier is connected to the fuel sensor, and the positive input end of the operational amplifier is grounded through the grounding resistor; A third A / D conversion unit, used for collecting the output voltage of the proportional amplification unit and transmitting it to the processor unit; The second A / D conversion unit is used to collect the output voltage of the square wave excitation signal and transmit it to the processing unit.

2. The aviation fuel measurement system according to claim 1, characterized in that: A power amplification unit is also arranged between the processor unit and the fuel sensor.

3. The aviation fuel measurement system according to claim 1, characterized in that: It also includes a temperature measuring unit, which is used to measure the temperature of the feedback capacitor and transmit the collected temperature signal to the processor unit.

4. The aviation fuel measurement system according to claim 1, characterized in that: It also includes a current indicating unit for measuring the output current of the square wave excitation signal, and the current indicating unit is communicatively connected to the processor unit through the first A / D conversion unit; the processor unit is also used to disconnect the square wave excitation signal when the output current of the square wave excitation signal reaches a preset threshold.

5. An aviation fuel measurement method based on square wave excitation, the method is based on the aviation fuel measurement system according to claim 1, characterized in that: include: After the aviation fuel measurement system is powered on, when the processor unit does not send a square wave excitation signal, a zero level calibration is performed in advance to read the first voltage value of the second A / D conversion unit and the second voltage value of the third A / D conversion unit; The processor unit sends a square wave excitation signal, and reads the excitation voltage value of the second A / D conversion unit and the feedback voltage value of the third A / D conversion unit; The real-time value of the fuel sensor is calculated according to the first voltage value, the second voltage value, the excitation voltage value and the feedback voltage value.

6. The aviation fuel measurement method according to claim 5, characterized in that: Fuel sensor C x Real-time value through formula The analysis shows that V A / D2 is the excitation voltage value, V A / D20 is the first voltage value, V A / D3 is the feedback voltage value, V A / D20 is the second voltage value, C f is the capacitance value of the feedback capacitor.

7. The aviation fuel measurement method according to claim 5, characterized in that: The method for receiving a square wave excitation signal from a processor unit and reading an excitation voltage value of a second A / D conversion unit and a feedback voltage value of a third A / D conversion unit comprises: The processor unit generates a square wave excitation signal and simultaneously generates a frequency-multiplied signal A having a frequency twice that of the square wave excitation signal, wherein the falling edge of the frequency-multiplied signal A is aligned with the rising edge of the square wave excitation signal; When the square wave excitation signal is at a high level and the double frequency signal A is at a rising edge, the second A / D conversion unit is triggered to sample, and the recorded results are data A1, data A2, ..., data A n , A n represents the square wave excitation signal output voltage value obtained by the second A / D conversion unit at the nth sampling; When the processor unit detects that the square wave feedback signal is at a rising edge, it simultaneously generates a frequency-multiplied signal B having a frequency twice that of the square wave excitation signal, and the falling edge of the frequency-multiplied signal B is aligned with the rising edge of the square wave signal; When the square wave feedback signal is at a high level and the frequency-multiplied signal B is at a rising edge, the third A / D conversion unit is triggered to sample, and the recorded results are data B1, data B2, ..., data B n , B n It represents the output voltage value of the proportional amplification unit obtained by the nth sampling of the third A / D conversion unit.

8. The aviation fuel measurement method according to claim 5, characterized in that: A temperature measuring unit is arranged near the feedback capacitor to measure the temperature of the feedback capacitor, and the collected temperature signal is transmitted to the processor unit; The processor unit obtains the real-time temperature value from the temperature measurement unit according to C f ′ =C f0 ·[1+α(T t -T0)] to compensate the feedback capacitance value, where C f ′ The feedback capacitor at temperature T t The capacitance under, C f0 is the capacitance of the feedback capacitor at the reference temperature T0, α is the temperature coefficient of the feedback capacitor; Fuel sensor C x Real-time value through formula The analysis shows that V A / D2 is the excitation voltage value, V A / D20 is the first voltage value, V A / D3 is the feedback voltage value, V A / d20 is the second voltage value.

9. The aviation fuel measurement method according to any one of claims 5 to 8, characterized in that: The square wave excitation signal has symmetrical amplitudes about the time axis, and a high level duty cycle of the square wave excitation signal is not less than 50%.

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