A data acquisition method for continuous variable angle of attack pressure test in a transient high-speed wind tunnel

Abstract

The present invention discloses a data acquisition method for a continuous variable angle of attack pressure measurement test in a transient high-speed wind tunnel. The continuous variable angle of attack pressure measurement test data acquisition system comprises a programmable synchronous trigger, a VXI / PXI data acquisition system that supports external triggering and has a sampling rate of at least 200 Hz, one or more pressure measurement systems that support external triggering and have a sampling rate of at least 100 Hz, a VXI / PXI data acquisition system host computer, and a pressure measurement system host computer. A multi-channel synchronous hardware trigger device is used to achieve precise synchronous acquisition of multiple sets of various types of acquisition systems, effectively solving the problems of asynchronous startup of multiple acquisition systems and inaccurate sampling rate settings of the acquisition system software under the traditional network command mode.

Description

Technical Field

[0001] The invention belongs to the technical field of aerodynamic wind tunnel tests, and in particular relates to a data acquisition method for a transient high-speed wind tunnel continuous variable angle of attack pressure test. Background Art

[0002] Pressure testing is an important tool for measuring aircraft aerodynamic forces. It not only determines the pressure distribution and aerodynamic loads on the aircraft and its components, but also helps determine the location of minimum pressure points, shock waves, and flow separation. This provides a basis for structural strength calculations, aerodynamic analysis, and flow characteristics studies of the aircraft and its components. A common pressure test involves placing pressure taps on the surface of the test model, connecting them to a pressure measurement system via pressure piping. Pressure measurements are performed using a step-by-step process with paused acquisition. A single pressure test only captures pressure data at a few sparsely spaced angles of attack (usually 2° to 5°). A continuously variable angle of attack pressure test involves continuously and rapidly acquiring pressure data on the aircraft model's surface, along with the corresponding flow field and model attitude information, while the model moves at a constant speed within the desired angle of attack range. This allows for a near-continuous pressure-versus-angle curve within the desired range. Data acquisition in this test involves a VXI / PXI data acquisition system collecting wind tunnel flow field and model attitude information, and a single or multiple pressure measurement systems simultaneously acquiring model surface pressure data. Because the VXI / PXI data acquisition system and various types and sets of pressure measurement systems are independent of each other, achieving synchronous and co-frequency acquisition is difficult. Furthermore, due to the uncertainty of network signal transmission delays and the inaccuracy of software-set sampling frequencies, it is difficult to accurately synchronize the wind tunnel flow field and model attitude angle data collected by the VXI / PXI data acquisition system with the model surface pressure data collected by the pressure measurement system during continuously variable angle of attack pressure measurement tests. This random asynchrony introduces significant difficulties and errors in subsequent data processing and analysis, making it difficult to meet the requirements of continuously variable angle of attack pressure measurement. Summary of the Invention

[0003] The purpose of the present invention is to improve the existing technology and realize high-precision synchronous acquisition of multiple sets of acquisition systems of different types in wind tunnel tests.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for collecting data from a continuous variable angle of attack pressure test in a transient high-speed wind tunnel is disclosed. The continuous variable angle of attack pressure test data acquisition system comprises a programmable synchronous trigger, a VXI / PXI data acquisition system that supports external triggering and has a sampling rate of at least 200 Hz, one or more pressure measurement systems that support external triggering and have a sampling rate of at least 100 Hz, a VXI / PXI data acquisition system host computer, and a pressure measurement system host computer. The programmable synchronous trigger has the following functions:

[0006] Can receive program-controlled instructions to control the generation and stop of pulses in each trigger channel;

[0007] Each trigger channel can independently set different trigger square wave frequency, square wave shape and start delay time;

[0008] The clock accuracy of the synchronous trigger reaches 0.01ms.

[0009] The collection method specifically includes the following steps:

[0010] S1: Before the wind tunnel test, set the trigger square wave frequency, square wave shape, and delay time for each output channel of the synchronization trigger based on the desired sampling rate and the external triggering method of each acquisition system. The trigger square wave frequency must not exceed the maximum sampling rate of the connected acquisition system. Common acquisition frequencies for VXI / PXI data acquisition systems in wind tunnels range from 300Hz to 500Hz, while those for pressure measurement equipment range from 100Hz to 300Hz.

[0011] S2: Before the wind tunnel test, the software sets the acquisition parameters of the VXI / PXI data acquisition system as follows: external hardware triggering, collecting 1 to 21 frames each time and calculating the average value.

[0012] S3: Before the wind tunnel test, the software sets the acquisition parameters of each pressure measurement system as follows: external hardware triggering, collecting 1 to 5 frames each time triggering and calculating the average value.

[0013] S4: Before the wind tunnel is started, all acquisition systems are in the state of waiting for external trigger signals.

[0014] S5: When the wind tunnel is started, the host computer of the VXI / PXI data acquisition system receives the wind tunnel start signal and immediately sends a continuous acquisition start signal to the synchronization trigger; each trigger channel of the synchronization trigger generates a pulse according to the preset trigger square wave frequency, square wave shape, delay time and other parameters, triggering the VXI / PXI data acquisition system and pressure measurement system to start continuous acquisition according to the synchronization trigger square wave output time, the trigger square wave frequency of the connected channel and the sampling mode set by each acquisition system.

[0015] S6: During the continuous data collection process of the wind tunnel test, each data collection system adds a timestamp to each row of data collected. The timestamp format can be a relative time from the start or an absolute system time.

[0016] S7: During the wind tunnel test, when the VXI / PXI system host computer and the pressure measurement system host computer receive information from the network that the model's starting and ending attitude angles are stable, they mark the starting and ending attitude angles in the currently acquired data frame. The time it takes for the model's attitude angles to stabilize must be greater than 1.5 seconds.

[0017] S8: After the wind tunnel test is completed, the host computer of the VXI / PXI data acquisition system sends a stop continuous acquisition signal to the synchronous trigger. The synchronous trigger stops outputting trigger pulses, and each acquisition system stops continuous acquisition and saves the collected continuous data respectively.

[0018] S9: In the continuous variable angle of attack pressure measurement test, the test data collected when the flow field is stable and the angle of attack moves uniformly from the starting attitude angle to the ending attitude angle position is called valid test data. The data extending from 200 frames to 1000 frames from the model start / end attitude angle mark position is set as valid test data.

[0019] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0020] Using hardware synchronization triggering equipment to trigger multiple sets of various types of acquisition systems can effectively improve the synchronization of multiple sets of equipment acquisition, achieve accurate synchronization of data acquisition time, and accurately control the data sampling rate. This effectively solves the uncertainty of the acquisition start time of the traditional network command method and the inaccuracy of the software setting sampling rate.

[0021] The continuous test data collected by multiple acquisition systems at the start of the wind tunnel, precisely and synchronously, can obtain all information about the time-varying changes of all measured parameters throughout the entire test process, including fluctuation bandwidth, frequency, and their respective correlations, providing detailed data support for comprehensive analysis of the test data. The pressure data collected by the pressure measurement system and the start and end attitude position identifiers contained in the flow field and attitude angle data collected by the VXI / PXI acquisition system facilitate state identification and processing during the test.

[0022] The model's initial and final attitude angles are stable for 1.5 seconds and the extended effective test data segment of 200 to 1000 frames can ensure the subsequent extended data acquisition for accurate synchronization of pressure measurement data with flow field data and model angle of attack data. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0024] Figure 1This is a diagram showing the composition of the data acquisition system for the continuous variable angle of attack pressure test in a transient high-speed wind tunnel.

[0025] Figure 2 This is a flow chart of the data collection method for the continuous variable angle of attack pressure measurement test in a transient high-speed wind tunnel. DETAILED DESCRIPTION

[0026] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0027] Any feature disclosed in this specification (including any appended claims, abstract, and drawings), unless otherwise stated, may be replaced by other equivalent or similar features. In other words, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0028] like Figure 1 As shown in Figure 1, the data acquisition system for the transient high-speed wind tunnel continuous variable angle of attack pressure test in this embodiment consists of a synchronization trigger, a VXI-1413C data acquisition system, four Initium pressure measurement systems, a data acquisition system host computer, and a pressure measurement system host computer. The VXI-1413C data acquisition system supports external triggering and has a maximum cycle scan rate of 100kHz. The four Initium systems also support external triggering and have a maximum sampling rate of 1000Hz.

[0029] Connect the sync trigger:

[0030] The synchronous trigger has 8 trigger channels, each with a synchronization accuracy of 0.01ms and a pulse frequency of up to 5kHz.

[0031] Trigger channel 1 is connected to the VXI-1413C data acquisition system, and trigger channels 2-5 are connected to Initium pressure measurement systems 1-4 respectively, supporting a total of 2048 points of pressure acquisition.

[0032] Specific test steps are as follows Figure 2 As shown:

[0033] S1: Before the wind tunnel test, preset the trigger wave frequency and delay time of each output channel of the synchronous trigger according to the VXI-1413C data acquisition system, the Initium system external trigger mode and the test requirements:

[0034] Set the trigger output wave to a rectangular square wave with an amplitude of 5V and a square wave width of 0.5 times the period;

[0035] Trigger channel 1 is set to: trigger square wave frequency is 300Hz, falling edge trigger, delay time is 0;

[0036] The trigger wave frequency of trigger channels 2, 3, and 4 is set to 150Hz, rising edge trigger, and the delay time is 1.667ms.

[0037] S2: Before the wind tunnel test, the software sets the acquisition parameters of the VXI-1413C data acquisition system. The trigger mode is external falling edge trigger. Each trigger, 7 frames are acquired, averaged, and saved.

[0038] S3: Before the wind tunnel test, the software sets the acquisition parameters for the Initium pressure measurement system. The trigger mode is external rising edge trigger, and each trigger collects and saves one frame of data.

[0039] S4: Before starting the wind tunnel, confirm that all acquisition systems are in the state of waiting for external triggering.

[0040] S5: When the wind tunnel is started, when the host computer of the VXI-1413C data acquisition system receives the "CGO" signal of wind tunnel start, it immediately programs the synchronous trigger to synchronously output the trigger signal of each channel, and each acquisition system connected to it continuously collects test data according to the set acquisition frequency and acquisition method.

[0041] S6: During the continuous data collection process of the wind tunnel test, each data collection system adds a timestamp to each row of data collected. The timestamp format is the relative time of the start of the start.

[0042] S7: During the wind tunnel test, the model moves at a constant speed of 0.5° / s to 1° / s between the starting and ending attitude angles required for the test. Once the starting and ending attitude angles are in place, they remain stable for 2 seconds. When the VXI-1413C data acquisition system and pressure measurement system host computers receive the "ACQ" message indicating that the model's starting and ending attitude angles are stable, they mark the currently collected data row. In the data column labeled STP_ID, the starting attitude angle stability segment is marked as "1," the ending attitude angle stability segment is marked as "2," and the remaining segments are marked as "0."

[0043] S8: When the test ends, when the VXI-1413C data acquisition system host computer receives the "END" signal, the synchronous trigger stops outputting trigger pulses, each system stops continuous acquisition, and the collected continuous data are saved separately.

[0044] S9: After the test is completed, the data of the start and end attitude angle mark positions extending 500 frames are set as valid test data.

[0045] The present invention is not limited to the aforementioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A method for collecting data from a continuous variable angle of attack pressure test in a transient high-speed wind tunnel, characterized by: It includes a pressure test data acquisition system, which is composed of a synchronization trigger, a data acquisition system, four pressure test systems, a data acquisition system host computer, and a pressure test system host computer; The trigger channel 1 of the synchronous trigger is connected to the data acquisition system, and the trigger channels 2-5 are connected to the pressure measurement systems 1-4 respectively; The pressure test data acquisition method comprises the following steps: S1: Before the wind tunnel test, set the trigger square wave frequency, square wave shape and delay time parameters of each trigger channel of the synchronization trigger. The trigger square wave frequency should not be higher than the maximum sampling rate of the connected data acquisition system and each pressure measurement system. S2: Before the wind tunnel test, set the acquisition parameters of the data acquisition system: use external hardware triggering, and collect 1 to 21 frames for each trigger and calculate the average value; S3: Before the wind tunnel test, set the acquisition parameters of each pressure measurement system: use external hardware triggering, and collect 1 to 5 frames for each trigger and calculate the average value; S4: Before the wind tunnel is started, the data acquisition system and each pressure measurement system are in a state of waiting for external triggering; S5: When the wind tunnel is started, the data acquisition system host computer receives the wind tunnel start signal and immediately sends a continuous acquisition start signal to the synchronization trigger. Each trigger channel of the synchronization trigger generates a pulse according to the preset trigger square wave frequency, square wave shape and delay time parameters. The data acquisition system and pressure measurement system start continuous acquisition according to the synchronization trigger square wave output time, the trigger square wave frequency of the connected channel, and the sampling mode set by the data acquisition system and each pressure measurement system. S6: During the continuous data collection process of the wind tunnel test, the data acquisition system host computer and the pressure measurement system host computer add a timestamp to each row of data collected. The timestamp format is relative time from the start of the test or absolute system time, with time accuracy to milliseconds. S7: During the wind tunnel test, when the host computer of the data acquisition system and the host computer of the pressure measurement system receive information from the network that the starting attitude angle and the ending attitude angle of the tested model are in place and stable, the starting attitude angle or the ending attitude angle is marked in the currently collected data frame; S8: After the wind tunnel test is completed, the data acquisition system host computer sends a stop continuous acquisition signal to the synchronization trigger. The synchronization trigger stops outputting pulses, and the data acquisition system and each pressure measurement system stop continuous acquisition and save the collected continuous data respectively. S9: Obtain valid test data from the collected data. The valid test data is data in which the flow field is stable and the angle of attack moves uniformly from the starting attitude angle position to the ending attitude angle position and extends from 200 frames to 1000 frames.

2. The data acquisition method for continuous variable angle of attack pressure test in a transient high-speed wind tunnel according to claim 1 is characterized in that In S1, the acquisition frequency of the data acquisition system in the wind tunnel is 300Hz~500Hz, and the acquisition frequency of the pressure measurement system is 100Hz~300Hz.

3. The data acquisition method for continuous variable angle of attack pressure test in a transient high-speed wind tunnel according to claim 1 is characterized in that In S7, the time for the attitude angle of the model under test to be stable must be greater than 1.5 seconds.

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