Refueling-free calibration oil mass volume measuring system and refueling-free calibration method

Abstract

The invention discloses a refueling-free calibration oil mass and volume measuring system and a refueling-free calibration method. The system comprises a capacitance oil quantity sensor, a measuring cable, an adjustable capacitance device and a measuring computer which are connected in sequence, the capacitance value of the capacitance fuel quantity sensor linearly changes along with the oil immersion height, and the capacitance fuel quantity sensor is used for generating a capacitance signal comprising the corresponding capacitance value based on the fuel level in the fuel tank; the measuring computer is used for calculating the fuel volume of the fuel tank based on the capacitance signal; the adjustable capacitance device is used for compensating capacitance deviation caused by replacement of the capacitance oil quantity sensor, the measuring cable and / or the measuring computer, so that the capacitance value collected by the measuring computer is kept consistent with the capacitance value before replacement, and refueling-free calibration is achieved. According to the invention, the adjustable capacitor device is introduced to replace physical refueling, so that rapid, accurate and zero-consumption refueling-free calibration is achieved, and the maintenance efficiency and the part interchangeability are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of aircraft fuel measurement technology, and more specifically, relates to a fuel volume measurement system and a fuel calibration method that do not require refueling. Background Technology

[0002] The fuel volume measurement system is one of the key systems of an aircraft, used to monitor the fuel level in each fuel tank in real time and accurately. It is crucial for flight safety, mission planning, and fuel economy management. A typical fuel measurement system mainly includes components such as a capacitive fuel level sensor, measurement cables, and a measurement computer. Its basic principle is to use the linear change in capacitance of the capacitive sensor in the fuel and air medium to sense the fuel level, which is then converted into volume by the measurement computer.

[0003] However, existing technology has a significant drawback: due to unavoidable individual performance differences in the manufacturing of core components such as fuel level sensors, measuring cables, and measuring computers, their capacitance characteristics (such as sensor dry capacitance, cable parasitic capacitance, and measuring circuit reference capacitance) cannot be completely consistent. When any component in the system needs to be replaced due to failure or maintenance, this individual difference will cause a change in the static capacitance of the entire measuring circuit, resulting in a systematic deviation in the readings of the measuring computer. To ensure measurement accuracy, the current common practice is to perform a complete "fill-up-empty" calibration procedure (i.e., zeroing and full-up tests) on all fuel tanks of the entire machine after component replacement.

[0004] This traditional physical calibration method has many prominent problems:

[0005] First, it is inefficient and time-consuming. Especially for medium and large-sized aircraft, the refueling, stabilization, testing, and fuel dumping processes are extremely time-consuming, which seriously affects the aircraft's availability and uptime.

[0006] Secondly, it is not economically viable and results in significant resource waste. The operation requires a large amount of fuel and occupies numerous ground support equipment and professional personnel, leading to unnecessary operating costs.

[0007] Third, the operation is complex and its stability is questionable. The accuracy of refueling calibration is affected by various factors such as the standardization of refueling operations, ambient temperature, and fuel characteristics, resulting in poor long-term stability of interchangeability calibration, which may require repeated testing.

[0008] Therefore, there is an urgent need in this field for a method and system for measuring oil volume that can fundamentally avoid full-machine refueling calibration and enable rapid, accurate, and low-cost system recalibration after component replacement, in order to solve the long-standing industry pain points of low maintenance efficiency and high operating costs. Summary of the Invention

[0009] The purpose of this invention is to propose an oil volume measurement system and a calibration method that requires no refueling, thereby solving the technical problems of low efficiency, high cost, and complicated operation caused by the requirement to perform full-machine refueling calibration after replacing parts in existing oil volume measurement systems; achieving fast and accurate refueling-free calibration, significantly improving maintenance efficiency and component interchangeability.

[0010] To achieve the above objectives, in a first aspect, the present invention proposes a fuel volume measurement system that requires no refueling calibration, comprising:

[0011] The capacitive oil level sensor, measuring cable, adjustable capacitor device, and measuring computer are connected in sequence.

[0012] The capacitance value of the capacitive fuel level sensor changes linearly with the immersion depth, and is used to generate a capacitance signal including the corresponding capacitance value based on the fuel level in the fuel tank.

[0013] The measuring computer is used to calculate the fuel volume of the fuel tank based on the capacitance signal;

[0014] The adjustable capacitor device is used to compensate for the capacitance deviation caused by replacing the capacitance oil level sensor, measuring cable and / or measuring computer, so that the capacitance value collected by the measuring computer is consistent with that before replacement, realizing calibration without refueling.

[0015] Optionally, the adjustable capacitor device includes:

[0016] Multiple signal conditioning channels, each signal conditioning channel corresponding to a measurement branch, each measurement branch consisting of a capacitive fuel level sensor and a measurement cable;

[0017] Each of the signal conditioning channels includes:

[0018] Base value capacitor, multiple parallel compensation branches and multiple series compensation branches;

[0019] The first end of the base capacitor is connected to the input end of the signal conditioning channel, and the second end is connected to the output end of the signal conditioning channel.

[0020] Each of the parallel compensation branches is connected in parallel with the base capacitor, and each of the parallel compensation branches is composed of a compensation capacitor and a first controlled switch connected in series.

[0021] One end of each of the series compensation branches is connected to the second end of the base capacitor, and the other end is connected to the output end of the signal conditioning channel. Each of the series compensation branches consists of a compensation capacitor and a second controlled switch connected in series.

[0022] The first and second controlled switches operate in response to external adjustment commands, selectively activating the parallel compensation branch and / or the series compensation branch to adjust the output capacitance value of the signal conditioning channel, thereby ensuring that the capacitance value acquired by the measuring computer remains consistent with that before replacement, achieving calibration without refueling.

[0023] Optionally, it also includes:

[0024] An onboard computer, which is communicatively connected to the measuring computer, is used to forward fuel quantity information and external adjustment commands;

[0025] A ground-based host computer, which is communicatively connected to the airborne computer, is used to receive and display the fuel quantity information and generate the external adjustment commands;

[0026] The adjustable capacitor device receives the external adjustment command either through the measuring computer or directly from the onboard computer.

[0027] Optionally, the capacitive sensor includes:

[0028] An internal capacitive sensor is installed inside the fuel tank;

[0029] An external capacitive sensor is located outside the fuel tank.

[0030] Optionally, the adjustable capacitor device controls the combined states of multiple first controlled switches and / or second controlled switches to enable the output capacitance value of the signal conditioning channel to be adjusted in a discrete manner within a preset capacitance value range.

[0031] Optionally, the preset capacitance value range is greater than the range of changes in the total system capacitance value caused by replacing any component or combination of the capacitance oil level sensor, the measuring cable, and the measuring computer.

[0032] Optionally, each of the fuel tanks may be provided with one or more of the measurement branches.

[0033] Secondly, the present invention proposes a refueling-free calibration method, applied to the refueling-free calibration oil volume measurement system described in any one of the first aspects, characterized in that the method comprises:

[0034] After the oil volume measurement system completes its initial calibration, the total reference capacitance value corresponding to the capacitive oil volume sensor acquired by the measurement computer is recorded.

[0035] After the system components are replaced, the current total capacitance value corresponding to the capacitive oil level sensor is obtained from the measurement computer.

[0036] The current total capacitance value is compared with the corresponding total reference capacitance value to generate a capacitance adjustment command to compensate for the deviation.

[0037] The capacitance adjustment command is sent to the adjustable capacitance device, which adjusts the current total capacitance value until the current total capacitance value collected by the measuring computer returns to the total reference capacitance value.

[0038] The beneficial effects of this invention are as follows: by introducing an adjustable capacitor device connected in series in the measurement circuit, after replacing the sensor, cable or computer, its output capacitance can be directly adjusted by software commands to compensate for the deviation of the total capacitance of the circuit caused by individual differences of components, so that the measured value can be automatically restored to the state before replacement. This completely eliminates the time-consuming, oil-consuming and expensive full machine refueling and calibration process, significantly improves maintenance efficiency, reduces operating costs, and ensures the long-term stable interchangeability and reliability of the measurement system.

[0039] The system of the present invention has other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0040] The above and other objects, features and advantages of the present invention will become more apparent from the accompanying drawings, in which like reference numerals generally denote like parts.

[0041] Figure 1 A schematic diagram of a fuel volume measurement system that requires no refueling calibration according to the present invention is shown.

[0042] Figure 2 A schematic diagram of an oil volume measurement system without refueling calibration according to Embodiment 1 of the present invention is shown.

[0043] Figure 3 A schematic diagram of the structure of each channel of the adjustable capacitor device according to Embodiment 2 of the present invention is shown.

[0044] Figure 4 A schematic diagram of the structure of each channel of the adjustable capacitor device according to Embodiment 3 of the present invention is shown. Detailed Implementation

[0045] The invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0046] like Figure 1 As shown, a fuel volume measurement system without refueling calibration according to the present invention includes:

[0047] The capacitive oil level sensor, measuring cable, adjustable capacitor device, and measuring computer are connected in sequence.

[0048] The capacitance value of the capacitive fuel level sensor changes linearly with the immersion depth, and is used to generate a capacitance signal including the corresponding capacitance value based on the fuel level in the fuel tank.

[0049] The measuring computer is used to calculate the fuel volume in the fuel tank based on capacitance signals;

[0050] The adjustable capacitor device is used to compensate for capacitance deviations caused by replacing the capacitor oil level sensor, measuring cable and / or measuring computer, so that the capacitance value collected by the measuring computer is consistent with that before replacement, achieving calibration without refueling.

[0051] Specifically, the system constructs a digital, calibrable fuel quantity measurement loop based on the principle of capacitive sensing. Its core lies in the capacitive fuel quantity sensor, which acts as the sensing unit. The capacitance value of this sensor is linearly related to the fuel level (immersion height), thus converting the non-electrical quantity of fuel volume into a linear capacitance change signal. This signal is transmitted through a measurement cable, which itself introduces a fixed parasitic capacitance. The signal then enters the key module of this invention—the adjustable capacitance device. This device is connected in series with the subsequent measurement computer, forming a complete signal chain. The measurement computer is responsible for acquiring the total capacitance signal of the loop and calculating the corresponding fuel volume based on the known linear relationship.

[0052] The system's innovation and core functionality lie in its "fuel-free calibration." When any component in the system (fuel level sensor, measuring cable, or measuring computer) is replaced due to malfunction or maintenance, the individual performance differences of the new component cause a shift in the reference capacitance of the entire measuring circuit. Traditional methods require recalibration through actual refueling. In this system, however, the adjustable capacitor acts as a software-adjustable "capacitance compensator." Upon detecting a deviation in the capacitance value read by the measuring computer due to component replacement, the system sends an adjustment command to the adjustable capacitor to precisely change its output capacitance value, thus actively offsetting the capacitance deviation caused by the component replacement. After this adjustment, the total capacitance value collected by the measuring computer remains consistent with the reference state before replacement. This means the output of the entire measuring system can be recalibrated without performing any actual refueling or evacuation. This process fundamentally transforms calibration from a cumbersome and expensive physical operation into a fast and precise software adjustment, achieving a qualitative improvement in maintenance efficiency.

[0053] In one example, the adjustable capacitor device includes:

[0054] Multiple signal conditioning channels, each signal conditioning channel corresponds to a measurement branch, and each measurement branch consists of a capacitive fuel level sensor and a measurement cable;

[0055] Each signal conditioning channel includes:

[0056] Base value capacitor, multiple parallel compensation branches and multiple series compensation branches;

[0057] The first end of the base capacitor is connected to the input terminal of the signal conditioning channel, and the second end is connected to the output terminal of the signal conditioning channel.

[0058] Each parallel compensation branch is connected in parallel with the base capacitor, and each parallel compensation branch is composed of a compensation capacitor and a first controlled switch connected in series.

[0059] One end of each series compensation branch is connected to the second end of the base capacitor, and the other end is connected to the output of the signal conditioning channel. Each series compensation branch consists of a compensation capacitor and a second controlled switch connected in series.

[0060] The first and second controlled switches operate in response to external adjustment commands, selectively connecting the parallel compensation branch and / or the series compensation branch to adjust the output capacitance value of the signal conditioning channel, thereby ensuring that the capacitance value acquired by the measuring computer remains consistent with that before replacement, achieving calibration without refueling.

[0061] Specifically, this adjustable capacitor device, as the core hardware module for achieving the refueling-free calibration function, adopts a modular, digitally programmable precision capacitor adjustment architecture. The device integrates multiple independent signal conditioning channels, each corresponding to a physical measurement branch consisting of a single capacitive fuel level sensor and its dedicated measurement cable, thus supporting parallel and independent calibration of multi-tank, multi-sensor systems.

[0062] At the core of each signal conditioning channel is a base capacitor serving as a capacitance reference, with its two ends defining the channel's input (connecting to the sensor cable) and output (connecting to the measurement computer), respectively. Around this base capacitor, two sets of networked conditioning branches, each consisting of controlled switches and compensation capacitors, are configured within the channel: The first is multiple parallel compensation branches, each connecting a compensation capacitor to the base capacitor via a first controlled switch. When the switch is closed, the compensation capacitor is connected in parallel with the base capacitor, directly increasing the channel's total output capacitance. The second is multiple series compensation branches, each connecting a compensation capacitor between the base capacitor's output and the channel's output via a second controlled switch. When the switch is closed, the compensation capacitor is effectively connected in series with the base capacitor, thus reducing the channel's total output capacitance.

[0063] The entire adjustment process is digitally controlled by external commands. When the system detects that a channel's measurement value deviates from the reference due to component replacement, it generates a specific adjustment command and sends it to the device. After parsing the command, the controller inside the device drives the corresponding first and / or second controlled switches to perform precise action combinations—that is, selectively closing or opening specific parallel and series branches. Through this digital programming of the switch array, the composite output capacitance of the channel can be adjusted discretely and stepwise, ultimately restoring the total capacitance signal flowing to the subsequent measurement computer to the calibration value before component replacement. This allows for software-based recalibration of the electrical characteristics of the entire measurement circuit without any fuel intervention.

[0064] In one example, it also includes:

[0065] The onboard computer is connected in communication with the measurement computer and is used to forward fuel quantity information and external adjustment commands;

[0066] The ground-based host computer communicates with the onboard computer to receive and display fuel quantity information and generate external adjustment commands.

[0067] The adjustable capacitor device receives external adjustment commands either from a measuring computer or directly from an onboard computer.

[0068] Specifically, the system constructs a complete hierarchical, remotely controllable calibration and monitoring network. The airborne computer, serving as the core of local data aggregation and command relay on the aircraft, establishes a two-way communication link with the measurement computer, receiving real-time fuel volume data from various measurement branches, and simultaneously undertaking command distribution tasks. The ground-based host computer is deployed at the ground support end, maintaining a stable connection with the airborne computer via a wireless data link, forming an integrated air-ground information system. The ground-based host computer not only receives and intuitively displays real-time fuel information from the airborne end, providing operators with global status awareness, but more importantly, it serves as the calibration command generation and decision-making terminal, allowing operators to directly generate and issue external adjustment commands for specific sensor channels after identifying data anomalies. These adjustment commands are transmitted uplink to the airborne computer via a wireless network. Subsequently, the airborne computer delivers the command to its target via two selectable reliable paths: one is forwarding through the measurement computer, and the other is sending it directly to the adjustable capacitor device. This flexible and redundant command path design ensures that calibration control commands can reliably trigger the adjustable capacitor device to perform precise capacitance compensation operations, thereby enabling online, non-contact software calibration of the onboard fuel measurement system from a remote ground station.

[0069] In one example, the capacitive sensor includes:

[0070] Built-in capacitive sensor, located inside the fuel tank;

[0071] An external capacitive sensor is located outside the fuel tank.

[0072] Specifically, this system is designed with broad adaptability and compatibility, supporting two mainstream capacitive fuel level sensor installation methods. The built-in capacitive sensor is directly installed within the fuel tank's internal structure, its sensing element immersed in the fuel medium, directly sensing changes in liquid level. This method typically offers high measurement directness and accuracy. The external capacitive sensor, on the other hand, is installed outside the fuel tank, usually sensing the internal liquid level indirectly through a structure connected to the tank wall. Its advantage lies in easier installation, maintenance, and replacement, eliminating the need to enter the tank or handle fuel. Regardless of whether the sensor is built-in or external, its core working principle relies on the linear relationship between capacitance value and immersion depth (or equivalent liquid level). This invention's refueling-free calibration system, through its adjustable capacitor device, effectively compensates for capacitance parameter variations caused by individual differences or replacements in both types of sensors. This ensures stable and reliable software calibration under different physical installation schemes, significantly broadening its application range and engineering practicality.

[0073] In one example, the adjustable capacitor device controls the combined states of multiple first controlled switches and / or second controlled switches to enable the output capacitance value of the signal conditioning channel to be adjusted in a discrete manner within a preset capacitance value range.

[0074] Specifically, the core mechanism of this adjustable capacitor device for achieving precise capacitance adjustment lies in its digital control logic. The internal processor, based on received external adjustment commands, interprets them as a precise control sequence of a series of first controlled switches (parallel branch switches) and second controlled switches (series branch switches) in a specific signal conditioning channel. By programming the "closed" and "open" states of these switches, various specific switch combinations are formed. Each switch combination corresponds to a defined circuit topology, allowing compensation capacitors of different numbers and values ​​to be connected to the base capacitor in parallel or series, thereby producing a discrete, specific composite output capacitance value. This adjustment is not continuous and stepless, but rather incrementally increased or decreased in discrete steps, using a preset minimum capacitance change (i.e., step size). The entire adjustment process is confined to a pre-designed capacitance value range. The lower limit of this range is determined by the minimum equivalent capacitance when all series branches are connected, while the upper limit is determined by the maximum equivalent capacitance when all parallel branches are connected. This discrete adjustment method based on switch combinations essentially transforms the analog adjustment of the capacitance value into digital control, and has the advantages of high reliability, high repeatability, strong anti-interference ability, and easy integration with computer systems to achieve fully automatic calibration.

[0075] In one example, the preset capacitance value range is greater than the range of changes in the total system capacitance value caused by replacing any component or combination of the capacitance oil level sensor, the measuring cable, and the measuring computer.

[0076] Specifically, the adjustable capacitance range of this adjustable capacitance device, after rigorous system design and tolerance analysis, is set to be greater than the maximum expected change in the total capacitance of the entire measurement circuit that might occur under real-world maintenance scenarios due to the replacement of any one or more of the three core components—the capacitive fuel level sensor, the measuring cable, and the measuring computer—either individually or in combination. This design principle is the fundamental guarantee for ensuring the reliability and effectiveness of the refueling-free calibration function. Specifically, engineers need to statistically analyze or measure to determine the performance dispersion of each component in batch production, quantifying the maximum positive and negative deviations that their capacitance parameters (such as the dry capacitance of the sensor, the parasitic capacitance of the cable, and the input capacitance of the computer) might deviate from the standard value. By superimposing these worst-case deviation values, the maximum total capacitance change range that the system needs to handle can be obtained. Subsequently, the capacity configuration of the parallel and series compensation networks for each channel in the adjustable capacitance device must ensure that the synthesized preset capacitance adjustment range completely covers and is slightly greater than the aforementioned maximum change range, thus reserving sufficient compensation margin for any possible component replacement combinations. This key design ensures that regardless of changes in component combinations during maintenance, the system has sufficient electrical regulation to correct the total capacitance of the measurement loop back to the reference value, eliminating the risk of calibration failure at the hardware level.

[0077] In one example, each fuel tank corresponds to one or more measurement branches.

[0078] Specifically, in the configuration of the fuel volume measurement system that requires no refueling calibration, the correspondence between the fuel tank and the measurement branch presents a flexible and scalable topology. Specifically, each independent fuel tank can be configured to connect to one or more measurement branches in the system. Each such measurement branch is a complete sensing and signal transmission unit, consisting of a capacitive fuel level sensor and its dedicated measurement cable.

[0079] When a single fuel tank is equipped with a measurement branch, the system adopts a single-point measurement mode. The capacitance signal provided by this branch represents the fuel level information of the entire fuel tank. This configuration is suitable for fuel tanks with regular shapes or relatively relaxed requirements for measurement accuracy.

[0080] When multiple measurement branches are set up for a single fuel tank, the system upgrades to a multi-point distributed measurement mode. In this case, multiple sensors are typically strategically placed at different locations within the fuel tank (e.g., front and rear ends or left and right sides) to overcome liquid level tilt caused by changes in aircraft attitude (such as climb, dive, and turn), or to measure large fuel tanks with irregular shapes. Each branch independently measures the liquid level at its mounting point, and the measurement computer synthesizes the signals from all branches using specific algorithms (such as averaging, weighted synthesis, or 3D modeling integration) to calculate a more accurate and reliable total fuel volume.

[0081] This design significantly improves the system's adaptability, measurement accuracy, and redundancy reliability. Regardless of the complexity of the tank geometry, accurate measurements can be achieved by increasing the number of branches; furthermore, even if one branch fails, the remaining branches can still provide backup measurement data, greatly enhancing the system's robustness. In the aforementioned adjustable capacitance device, each such measurement branch is independently connected to a dedicated signal conditioning channel, ensuring independent and accurate capacitance deviation compensation and calibration for each sensing node.

[0082] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0083] Example 1

[0084] This embodiment provides a fuel volume measurement system that requires no refueling calibration, including:

[0085] The system includes a fuel tank, a fuel level sensor, a measuring cable, an adjustable capacitor, a measuring computer, an onboard computer, and a ground-based host computer. The fuel level sensor, measuring cable, adjustable capacitor, measuring computer, and onboard computer are electrically connected in sequence, and the onboard computer and ground-based host computer are connected wirelessly.

[0086] For multi-fuel tank aircraft, there can be a first fuel tank, a second fuel tank, and a third fuel tank; each fuel tank can have one or more fuel level sensors, which can be built-in capacitive sensors or external capacitive sensors, and their capacitance values ​​change linearly with the immersion depth.

[0087] The first fuel tank is equipped with a first fuel level sensor, which is an external capacitive sensor; the second and third fuel tanks are each equipped with three fuel level sensors, namely the second, third, fourth, fifth, sixth and seventh fuel level sensors, all of which are internal capacitive sensors.

[0088] Each fuel level sensor is connected to an adjustable capacitor device channel via an independent measuring cable; the first to the seventh fuel level sensors are each connected to the first to the seventh channel of the adjustable capacitor device via the first to the seventh measuring cables, respectively.

[0089] The adjustable capacitor device, the measuring computer, and the airborne computer are electrically connected in sequence; the adjustable capacitor device and the measuring computer can communicate bidirectionally, sending and receiving information to each other; the measuring computer and the airborne computer can communicate bidirectionally, sending and receiving information to each other.

[0090] The adjustable capacitor bank can send the capacitance values ​​of each channel to a measurement computer, which in turn can send these values ​​to an onboard computer. The onboard computer and the ground computer are connected via radio, enabling bidirectional communication and the exchange of information. The onboard computer can also send the capacitance values ​​of each channel of the adjustable capacitor bank to a ground-based host computer. The onboard computer can send commands to the adjustable capacitor bank via the measurement computer or directly to the adjustable capacitor bank.

[0091] The adjustable capacitor device has multiple independent channels, each consisting of a base capacitor, a parallel capacitor bank, a series capacitor bank, and a circuit switch group. The base capacitor has a capacitance value of C. j The parallel capacitor bank consists of m capacitors connected in parallel with the base capacitor, each with a capacitance value of C. b1 C b2 …C bm The circuit switch on the path is controlled by the internal processor of the adjustable capacitor device, and the circuit switch is normally open. When the circuit switch is closed, the capacitor of that path will be connected in parallel with the base capacitor, and the output capacitance value of the channel will increase after parallel connection. Multiple capacitors can be connected in parallel with the base capacitor simultaneously; for example, when the capacitance value is C... b1 When connected in parallel with the base capacitor, the output capacitance of this channel is (C j +C b1 When the capacitance value is C b1 C b2 When connected in parallel with the base capacitor, the output capacitance of this channel is (C j +C b1 +C b2 ).

[0092] The circuit switch on the series capacitor bank path is controlled by the internal processor of the adjustable capacitor device, and the circuit switch is normally open. The series capacitor bank consists of n capacitors connected in series with the base capacitor, and their capacitance values ​​are C. c1 C c2 …C cn After the circuit switch is closed, the capacitor in this circuit will be connected in series with the base capacitor. After being connected in series, the output capacitance value of the channel will decrease. Multiple capacitors can be connected in series with the base capacitor simultaneously. For example, when the capacitance value is C... c1 When connected in series with the base capacitor, the output capacitance of this channel is When the capacitance value is C c1 C c2 Simultaneously, when connected in series with the base capacitor, the output capacitance of this channel is

[0093] The capacitance value of each channel of the adjustable capacitor device fluctuates within a certain range around the base capacitance value. The minimum output capacitance value can be expressed as (C j -ΔClo The maximum value can be expressed as (C). j +ΔC h ).

[0094] The adjustable capacitor device can automatically control the capacitor switching of parallel and series capacitor banks according to the capacitance adjustment commands from the measuring computer or onboard computer, so that the capacitance value of the channel output meets the requirements of the capacitance adjustment command; the range of parasitic capacitance change caused by changing the measuring computer is (-ΔC). mc ,ΔC mc The range of parasitic capacitance change caused by replacing the measuring cable is (-ΔC). ml ,ΔC ml The change in dry capacitance value caused by replacing the fuel level sensor is (-ΔC). mg ,ΔC mg The capacitance value fluctuation range of each channel output by the adjustable capacitor device is greater than the capacitance value change range caused by replacing the measuring computer, measuring cable, and oil level sensor, i.e., ΔC. lo >(ΔC mc +ΔC ml +ΔC mg ), ΔC h >(ΔC mc +ΔC ml +ΔC mg ).

[0095] The "first fuel level sensor capacitance value" measured by the measuring computer is the sum of the first fuel level sensor capacitance value, the first measuring cable, the parasitic capacitance of the first channel of the adjustable capacitor device, and the parasitic capacitance inside the measuring computer. The measuring computer converts the measured "first fuel level sensor capacitance value" into the fuel volume of the first fuel tank.

[0096] If the first fuel level sensor, the first measuring cable, or the measuring computer is replaced, the ground-based host computer can detect the change in the "capacitance value of the first fuel level sensor" measured by the measuring computer and send a capacitance adjustment command to the airborne computer. The adjustable capacitor device automatically changes the capacitance value of its first channel, so that the "capacitance value of the first fuel level sensor" measured by the measuring computer is restored to the capacitance value before replacement, thus achieving calibration without refueling.

[0097] The measuring computer uses a similar method to measure the capacitance values ​​of the "second fuel level sensor," "third fuel level sensor," and "fourth fuel level sensor," and converts these values ​​into the fuel volume of the second fuel tank. Similarly, the measuring computer uses the same method to measure the fuel volume of the third fuel tank.

[0098] If the second to seventh fuel level sensors or the second to seventh measuring cables are replaced, a capacitance adjustment command can be sent via the ground-based host computer. The adjustable capacitor device will automatically change the capacitance values ​​of its second to seventh channels, so that the "capacitance values ​​of the second to seventh fuel level sensors" measured by the measuring computer are restored to the capacitance values ​​before replacement, thus achieving calibration without refueling.

[0099] Compared with existing technologies, it has the following beneficial effects:

[0100] (1) It enables oil-free calibration after replacing multiple components such as oil level sensor, measurement cable and measurement computer in the measurement system, which greatly improves the interchangeability of components.

[0101] (2) It can be used in aircraft with multiple fuel tanks and multiple fuel quantity sensors, and has a wide range of applications.

[0102] (3) Calibration commands can be sent from the ground host computer, which is quick, convenient, time-saving and low labor cost.

[0103] Example 2

[0104] like Figure 2 As shown, this embodiment provides a fuel volume measurement system that requires no refueling calibration, including:

[0105] The fuel volume measurement system contains three fuel tanks: the first fuel tank 11, the second fuel tank 12, and the third fuel tank 13.

[0106] The first fuel tank 11 is equipped with a first fuel quantity sensor 21, which is an external fuel quantity sensor;

[0107] The second fuel tank 12 is equipped with a second fuel quantity sensor 22, a third fuel quantity sensor 23 and a fourth fuel quantity sensor 24;

[0108] The third fuel tank 13 is equipped with a fifth fuel level sensor 25, a sixth fuel level sensor 26 and a seventh fuel level sensor 27.

[0109] The first fuel level sensor 21, the second fuel level sensor 22, the third fuel level sensor 23, the fourth fuel level sensor 24, the fifth fuel level sensor 25, the sixth fuel level sensor 26, and the seventh fuel level sensor 27 are respectively connected to the first measuring cable 31, the second measuring cable 32, the third measuring cable 33, the fourth measuring cable 34, the fifth measuring cable 35, the sixth measuring cable 36, and the seventh measuring cable 37;

[0110] The adjustable capacitor device 40 has a total of 8 channels. The first measuring cable 31, the second measuring cable 32, the third measuring cable 33, the fourth measuring cable 34, the fifth measuring cable 35, the sixth measuring cable 36 and the seventh measuring cable 37 are respectively connected to channels 1 to 7 of the adjustable capacitor device 40, and channel 8 is reserved.

[0111] The adjustable capacitor device 40 is electrically connected to the measuring computer 50, enabling bidirectional communication and the sending and receiving of information. The measuring computer 50 is also electrically connected to the airborne computer 60, enabling bidirectional communication and the sending and receiving of information. Simultaneously, the airborne computer 60 can directly send communication information to the adjustable capacitor device 40. The airborne computer 60 is also electrically connected to the ground-based host computer 70, enabling bidirectional communication and the sending and receiving of information.

[0112] Adjustable capacitor bank 40, capacitor bank for each channel, such as Figure 3 As shown, the base capacitor 401 has a capacitance of 100pF, the parallel capacitor bank consists of four parallel capacitors 402, each with a capacitance of 1pF; the series capacitor bank consists of four series capacitors 403, each with a capacitance of 2000pF; each parallel and series capacitor is equipped with a circuit switch 404, and their switching states are controlled by the internal processor of the adjustable capacitor device 40. With this configuration, the adjustable capacitor device 40 can output a capacitance range of 85pF to 104pF.

[0113] Before replacing any parts, the circuit switch 404 is in the off state. The measuring computer 50 measures the capacitance values ​​of the "first fuel level sensor", "second fuel level sensor", "third fuel level sensor", "fourth fuel level sensor", "fifth fuel level sensor", "sixth fuel level sensor", and "seventh fuel level sensor" as 180pF, 170pF, 160pF, 150pF, 170pF, 160pF, and 150pF, respectively, and transmits this information to the ground host computer 70 for display via the onboard computer 60.

[0114] If the second fuel level sensor 22 fails, it should be replaced. After replacement, the ground control computer 70 will display a "second fuel level sensor capacitance value" of 175pF. At this time, the ground control computer 70 will send a second fuel level sensor capacitance adjustment command. Upon receiving the command, the adjustable capacitor device 40 will control a series capacitor switch 404 with a capacitance value of 2000pF in its second channel to switch from open to closed. After adjustment, the ground control computer 70 will display a "second fuel level sensor capacitance value" of 170pF, indicating successful calibration.

[0115] Example 3

[0116] The oil volume measurement system in Example 3 has the same composition as that in Example 2, except that the capacitor bank of each channel of the adjustable capacitor device 40 is as follows: Figure 4 As shown, the base capacitor 405 has a capacitance of 100pF. The parallel capacitor bank consists of 15 parallel capacitors 406, each with a capacitance of 1pF. The series capacitor bank consists of 15 series capacitors 407, of which 5 have a capacitance of 900pF, 5 have a capacitance of 1000pF, and 5 have a capacitance of 2000pF. Each parallel and series capacitor is equipped with a circuit switch 404, and their switching states are controlled by the internal processor of the adjustable capacitor device 40. With this configuration, the adjustable capacitor device 40 can output a capacitance range from 50pF to 120pF.

[0117] When the measuring computer 50 fails, it is replaced. After replacement, the ground-based host computer 70 displays the following values ​​for the "first fuel level sensor capacitance": 190pF, 155pF, 148pF, 153pF, 170pF, 160pF, and 150pF, respectively. Therefore, the capacitance values ​​for the "first fuel level sensor capacitance", "second fuel level sensor capacitance", "third fuel level sensor capacitance", "fourth fuel level sensor capacitance", "fifth fuel level sensor capacitance", "sixth fuel level sensor capacitance", and "seventh fuel level sensor capacitance". Therefore, the capacitance values ​​for the "first fuel level sensor capacitance", "second fuel level sensor capacitance", "third fuel level sensor capacitance", and "fourth fuel level sensor capacitance" need to be calibrated. At this time, the ground-based host computer 70 sends a first fuel level sensor capacitance adjustment command. Upon receiving the command, the adjustable capacitor device 40 controls the ten parallel capacitor switches 404 in its first channel to change from open to closed. The ground-based host computer 70 then sends a second fuel level sensor capacitance adjustment command, and the adjustable capacitor device 40 receives the command. Then, the circuit switch 404 controlling the ten parallel capacitor switches 404 and the three series capacitors with a capacitance of 900pF in the second channel changes from open to closed; the ground host computer 70 sends a third fuel level sensor capacitance adjustment command. After receiving the command, the adjustable capacitor device 40 controls the circuit switch 404 controlling one parallel capacitor switch 404 and the three series capacitors with a capacitance of 1000pF in the third channel to change from open to closed; the ground host computer 70 sends a fourth fuel level sensor capacitance adjustment command. After receiving the command, the adjustable capacitor device 40 controls the circuit switch 404 controlling eight parallel capacitor switches 404 and one series capacitor with a capacitance of 2000pF in the fourth channel to change from open to closed; after adjustment, the ground host computer 70 displays the "first fuel level sensor capacitance value", "second fuel level sensor capacitance value", "third fuel level sensor capacitance value" and "fourth fuel level sensor capacitance value" as 180pF, 170pF, 160pF ​​and 150pF respectively, and the calibration is successfully achieved.

[0118] Example 4

[0119] This embodiment provides a refueling-free calibration method, applied to the refueling-free calibration oil volume measurement system described in Embodiment 1. The method includes:

[0120] After the oil volume measurement system completes its initial calibration, the total reference capacitance value corresponding to the capacitive oil volume sensor acquired by the measurement computer is recorded.

[0121] After the system components are replaced, the current total capacitance value corresponding to the capacitive oil level sensor is obtained from the measurement computer.

[0122] The current total capacitance value is compared with the corresponding total reference capacitance value to generate a capacitance adjustment command to compensate for the deviation.

[0123] The capacitance adjustment command is sent to the adjustable capacitance device, which adjusts the current total capacitance value until the current total capacitance value collected by the measuring computer is restored to the total reference capacitance value.

[0124] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A fuel volume measurement system that requires no refueling calibration, characterized in that, include: The capacitive oil level sensor, measuring cable, adjustable capacitor device, and measuring computer are connected in sequence. The capacitance value of the capacitive fuel level sensor changes linearly with the immersion depth, and is used to generate a capacitance signal including the corresponding capacitance value based on the fuel level in the fuel tank. The measuring computer is used to calculate the fuel volume of the fuel tank based on the capacitance signal; The adjustable capacitor device is used to compensate for the capacitance deviation caused by replacing the capacitance oil level sensor, measuring cable and / or measuring computer, so that the capacitance value collected by the measuring computer is consistent with that before replacement, realizing calibration without refueling.

2. The fuel volume measurement system without refueling calibration according to claim 1, characterized in that, The adjustable capacitor device includes: Multiple signal conditioning channels, each signal conditioning channel corresponding to a measurement branch, each measurement branch consisting of a capacitive fuel level sensor and a measurement cable; Each of the signal conditioning channels includes: Base value capacitor, multiple parallel compensation branches and multiple series compensation branches; The first end of the base capacitor is connected to the input end of the signal conditioning channel, and the second end is connected to the output end of the signal conditioning channel. Each of the parallel compensation branches is connected in parallel with the base capacitor, and each of the parallel compensation branches is composed of a compensation capacitor and a first controlled switch connected in series. One end of each of the series compensation branches is connected to the second end of the base capacitor, and the other end is connected to the output end of the signal conditioning channel. Each of the series compensation branches consists of a compensation capacitor and a second controlled switch connected in series. The first and second controlled switches operate in response to external adjustment commands, selectively activating the parallel compensation branch and / or the series compensation branch to adjust the output capacitance value of the signal conditioning channel, thereby ensuring that the capacitance value acquired by the measuring computer remains consistent with that before replacement, achieving calibration without refueling.

3. The fuel volume measurement system without refueling calibration according to claim 1, characterized in that, Also includes: An onboard computer, which is communicatively connected to the measuring computer, is used to forward fuel quantity information and external adjustment commands; A ground-based host computer, which is communicatively connected to the airborne computer, is used to receive and display the fuel quantity information and generate the external adjustment commands; The adjustable capacitor device receives the external adjustment command either through the measuring computer or directly from the onboard computer.

4. The fuel volume measurement system without refueling calibration according to claim 1, characterized in that, The capacitance sensor includes: An internal capacitive sensor is installed inside the fuel tank; An external capacitive sensor is located outside the fuel tank.

5. The oil volume measurement system without refueling calibration according to claim 3, characterized in that, The adjustable capacitor device controls the combined states of multiple first controlled switches and / or second controlled switches, enabling the output capacitance value of the signal conditioning channel to be adjusted in a discrete manner within a preset capacitance value range.

6. The oil volume measurement system without refueling calibration according to claim 5, characterized in that, The preset capacitance value range is greater than the range of changes in the total system capacitance value caused by replacing any component or combination of the capacitance oil level sensor, the measuring cable, and the measuring computer.

7. The fuel volume measurement system without refueling calibration according to claim 2, characterized in that, Each of the fuel tanks is provided with one or more of the measurement branches.

8. A refueling-free calibration method, applied to the refueling-free fuel volume measurement system according to any one of claims 1-7, characterized in that, The method includes: After the oil volume measurement system completes its initial calibration, the total reference capacitance value corresponding to the capacitive oil volume sensor acquired by the measurement computer is recorded. After the system components are replaced, the current total capacitance value corresponding to the capacitive oil level sensor is obtained from the measurement computer. The current total capacitance value is compared with the corresponding total reference capacitance value to generate a capacitance adjustment command to compensate for the deviation. The capacitance adjustment command is sent to the adjustable capacitance device, which adjusts the current total capacitance value until the current total capacitance value collected by the measuring computer returns to the total reference capacitance value.

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