Magnetic levitation flight wind tunnel speed measurement device and method based on optical sensor and scale

Abstract

The invention discloses a magnetic levitation flight wind tunnel speed measurement device and method based on an optical sensor and a scale. The speed measuring device comprises a scale which is arranged along the motion trail direction of the magnetic levitation flight wind tunnel motion platform. Hollows which are distributed at equal intervals are formed in the scale in the axial direction; the optical probe moves along with the moving platform; the hollowed-out parts and the non-hollowed-out parts between the adjacent hollowed-out parts can form switching between shielding and passing of light beams emitted by the optical probe so as to generate switching type signals; and the switch type signal is used for calculating the motion speed of the motion platform. According to the invention, strong electromagnetic environment anti-interference capability and full-stroke continuous high-precision speed measurement can be taken into consideration at the same time, the system structure is simple, the cost is controllable, and the system can adapt to wide-speed-range test working conditions.

Description

Technical Field

[0001] This invention belongs to the field of wind tunnel testing technology, and in particular relates to a magnetic levitation flight wind tunnel speed measurement device and method based on optical sensors and scales. Background Technology

[0002] The maglev flight wind tunnel is a novel aerodynamic testing device that integrates superconducting magnetic levitation drive technology with the principle of dynamic model aerodynamic testing. Unlike the traditional wind tunnel's "wind-driven, body-static" testing mode, the maglev flight wind tunnel adopts a "body-driven, wind-static" testing logic. It can directly drive the test model to move at high speed along the track, realistically replicating the aerodynamic environment of aircraft, high-speed rail vehicles, and other equipment during actual operation. It boasts advantages such as wide speed range coverage, wide Reynolds number adaptation, low background noise, and low airflow turbulence. This equipment can effectively support research on core fundamental scientific issues in aerospace and rail transportation fields, such as boundary layer transition, aerodynamic noise suppression, flow separation control, and high-speed motion stability, as well as equipment performance verification. It is a key core testing device in the independent development of advanced aircraft, ultra-high-speed trains, and other high-end equipment in my country.

[0003] In the aerodynamic testing of a maglev flight wind tunnel, the real-time velocity of the test model is a fundamental parameter for calculating its aerodynamic coefficients and analyzing its aerodynamic characteristics. The accuracy, stability, and real-time performance of the velocity measurement results directly determine the validity of the aerodynamic test data. However, due to the limitations of the working principle of the maglev flight wind tunnel, the model's motion area during the test is subject to a high-intensity, large-scale, and complex electromagnetic field generated by the superconducting maglev system. Conventional electromagnetic velocity sensors and electronic measuring equipment are highly susceptible to strong electromagnetic interference, resulting in signal distortion, data drift, or even complete failure, making it impossible to achieve stable and accurate velocity measurement.

[0004] To address the speed measurement requirements in the strong electromagnetic environment of maglev flight wind tunnels, the current mainstream solution involves distributing a large number of speed sensors along the entire track. Multiple sets of sensors collect trigger signals as the test model passes through different locations. Combining the sensor spacing and trigger time difference, the average speed of the test model is calculated using a distance-time relationship. However, this solution has the following technical problems in practical applications: First, the test track of a maglev flight wind tunnel is usually hundreds or even thousands of meters long. In order to achieve continuous speed measurement throughout the entire process, hundreds or even thousands of sensors and supporting signal acquisition channels need to be deployed. The equipment procurement, installation and maintenance costs are extremely high, which greatly increases the construction cost of the wind tunnel test system.

[0005] Secondly, a large number of distributed sensors require complex wiring systems, synchronous acquisition systems and signal processing systems. The overall structure of the speed measurement system is huge and complex. Failure of any sensor or acquisition channel will affect the integrity of the speed measurement results. The overall reliability of the system is low, and troubleshooting and maintenance are extremely difficult.

[0006] Third, this scheme can only obtain segmented average speed through discrete sensor points, and cannot realize real-time continuous speed measurement of the entire test model's journey. It is difficult to reproduce the speed change history of the model in the entire stages of acceleration, constant speed and deceleration, and cannot meet the parameter requirements of high-precision aerodynamic tests.

[0007] Chinese patent application CN202010882500.8 discloses a particle imaging velocimetry system used in a wind tunnel, comprising a wind tunnel body, a model support and moving device, a particle generator, a particle dispersion connector, a particle dispersion tube, an illumination device, and an image acquisition device. The model support and moving device is located outside the experimental section of the wind tunnel and is used to mount the model and move it within the experimental section. The particle generator is connected to the particle dispersion tube via the particle dispersion connector. Mounting holes are symmetrically arranged on the sidewall of the wind tunnel. The particle dispersion tube is positioned between two symmetrically arranged mounting holes. The particle dispersion tube has particle dispersion nozzles, and the tracer particle layer ejected from the nozzles coincides with the spanwise section of the model to be measured. The laser sheet light layer emitted by the illumination device coincides with the spanwise section of the model to be measured and the tracer particle layer. The image acquisition device is located outside the experimental section of the wind tunnel and is used to acquire images of the spanwise section of the model to be measured.

[0008] While the particle image velocimetry method used in the above-mentioned existing technologies can achieve high-precision velocity measurement, the equipment is expensive, the optical path system is complex to build, and the requirements for the cleanliness of the test environment, vibration control, and airflow stability are extremely high. Airflow disturbances and track micro-vibrations during the maglev flight wind tunnel test will seriously affect the measurement accuracy. Moreover, it can only achieve instantaneous velocity measurement at fixed points and cannot complete continuous velocity measurement throughout the entire journey, making it difficult to adapt to the actual test conditions of the maglev flight wind tunnel. Summary of the Invention

[0009] The purpose of this invention is to provide a magnetic levitation flight wind tunnel speed measurement device and method based on optical sensors and scales, which partially solves or alleviates the above-mentioned shortcomings in the prior art. Its system structure is simple, the cost is controllable, and it can be adapted to wide speed range test conditions.

[0010] To solve the aforementioned technical problems, the present invention specifically adopts the following technical solution: A first aspect of the present invention is to provide a magnetic levitation flight wind tunnel speed measuring device based on an optical sensor and a scale, comprising a scale arranged along the motion trajectory direction of the magnetic levitation flight wind tunnel motion platform; the scale is provided with equally spaced cutouts along the axial direction; It also includes an optical probe that moves with the motion platform; the hollowed-out portion and the non-hollowed-out portion between adjacent hollowed-out portions can switch between blocking and passing the light beam emitted by the optical probe to generate a switching signal. The switch-type signal is used to calculate the motion speed of the motion platform.

[0011] Furthermore, the ratio of the width of the non-hollowed-out portion to the width of the hollowed-out portion of the scale is the duty cycle, and the duty cycle ranges from 0.1 to 1.0.

[0012] Furthermore, the duty cycle is 0.5.

[0013] Furthermore, the optical probe is fixed to the motion platform using a mounting bracket; When the optical probe is a reflective type, the mounting bracket includes a base plate for fixed connection with the motion platform and an upright plate for mounting the optical probe; When the optical probe is a through-beam type, the mounting bracket includes a column for fixing to the motion platform, and a crossbeam perpendicular to the motion direction of the motion platform is provided on the column; the crossbeam is provided with a fixed seat and a movable seat, and the movable seat can move along the crossbeam to adjust the distance between it and the fixed seat; the transmitting end and receiving end of the through-beam probe are respectively provided on the fixed seat and the movable seat, and the scale is located between the fixed seat and the movable seat.

[0014] Furthermore, it also includes an optical fiber amplifier and an electromagnetic shielding box. The optical probe is connected to the optical fiber amplifier via an optical fiber. The optical fiber amplifier is encapsulated in the electromagnetic shielding box. The output end of the electromagnetic shielding box is connected to a signal acquisition device. The signal acquisition device is connected to a host computer for communication. The host computer is used to calculate the motion speed of the motion platform based on the switch signal.

[0015] Furthermore, the scale is made of a non-ferromagnetic material with a thickness of 1-5 mm.

[0016] Furthermore, the magnetic levitation flight wind tunnel speed measuring device also includes an adjustment mechanism for adjusting the width of the hollowed-out area.

[0017] Preferably, the adjustment mechanism includes: an adjustment scale overlapping the scale on the front or rear side, the adjustment scale being reciprocating along the axial extension direction of the scale, thereby changing the cutout covering area of ​​the two scales and thus adjusting the width of the cutout. For example, the scales are two identical scales overlapping each other, and the axial position of at least one of the two scales is adjustable (i.e., serves as the adjustment scale), thereby changing the cutout covering area of ​​the two scales and thus adjusting the width of the cutout.

[0018] Furthermore, the adjustment mechanism also includes a linear drive mechanism for driving the movement of the adjustment scale, through which the relative axial positions of the two scales can be adjusted, thereby changing the width of the cutout.

[0019] This invention also provides a wind tunnel speed measurement method for maglev flight based on an optical sensor and a scale, which utilizes the aforementioned maglev wind tunnel speed measurement device, including: The switching signal output by the optical probe is differentiated in time to obtain the time derivative of the switching signal; peak detection is performed on the time derivative of the switching signal to extract the time points corresponding to all peaks; The motion speed of the motion platform is calculated based on the width of the cutout on the scale and the time difference of the peak time point.

[0020] Furthermore, the switching signal is a voltage signal, calculated using the formula: The time derivative of the voltage signal output by the optical probe is calculated; where, Let V(t) be the first derivative of the voltage signal V(t) with respect to time t, where V(t) is the voltage signal, t is time, and diff is the difference operator. Using the formula: Peak detection is performed on the time derivative of the voltage signal; where, It is a one-dimensional time series array that stores the time coordinates corresponding to all detected signal peaks. findpeaks() is the peak detection algorithm. Using the formula: Calculate the velocity of the motion platform; where v(t) is the velocity at time t. The width of the cutout.

[0021] Beneficial effects: This invention adopts the principle of optical non-contact speed measurement. The generation of optical signals and the transmission of optical fibers are not affected by the strong magnetic field of the superconducting magnetic levitation system. With the full-enclosed electromagnetic shielding box of the optical fiber amplifier and the coaxial anti-interference cable transmission, full-link electromagnetic protection is achieved, which completely solves the problems of signal distortion, data drift and even complete failure of traditional electromagnetic sensors under strong magnetic fields.

[0022] This invention employs time derivative and peak detection solution logic, which can completely filter out invalid noise caused by signal DC drift, low-frequency electromagnetic interference, and ambient light disturbance, and retain only the effective transition characteristics of beam on / off. Compared with traditional square wave threshold edge detection, the anti-interference capability is improved by an order of magnitude, and it can still output accurate speed measurement results stably under harsh test conditions.

[0023] This invention eliminates the need for deploying sensors and cables along the entire length of a long track, significantly shortening the installation and commissioning cycle. Subsequent maintenance only requires checking the status of a single optical probe and scale, greatly simplifying troubleshooting and replacement. This completely solves the problems of difficult maintenance and numerous potential failure points associated with traditional solutions involving a large number of sensors. The core moving component is a single servo optical probe, eliminating the need for numerous distributed electronic devices and minimizing system failure points. Non-contact measurement eliminates mechanical wear, ensuring long-term stable operation and significantly reducing the risk of test failure due to speed measurement system malfunctions. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. The elements or parts in the drawings are not necessarily drawn to scale. Obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0025] Figure 1 This is a structural schematic diagram of one embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the scale structure in this invention.

[0027] Figure 3 This is a schematic diagram of the installation of a reflective optical probe.

[0028] Figure 4 This is a schematic diagram of the installation of a through-beam optical probe.

[0029] Figure 5 This is a schematic diagram of an adjustable cutout ruler.

[0030] Figure 6 This is a flowchart of Embodiment 3 of the present invention.

[0031] Figure 7 This is a schematic diagram of the voltage signal output by the optical probe.

[0032] Figure 8 This is a schematic diagram of the speed signal obtained from the calculation.

[0033] Summary of attached labeling and identification: 1-Scale, 2-Mounting bracket, 3-Optical probe, 4-Electromagnetic shielding box, 5-Signal acquisition device, 6-Host computer, 11-Hollow hole, 12-Non-Hollow hole part, 21-Base plate, 22-Upright plate, 23-Column, 24-Crossbeam, 25-Fixed seat, 26-Movable seat, 101-Fixed reference scale, 102-Axially adjustable scale, 100-Test model, 200-Motion platform, 300-Railway. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] In this document, suffixes such as "module," "part," or "unit" used to denote elements are used only for the purpose of illustrative purposes and have no specific meaning in themselves. Therefore, "module," "part," or "unit" may be used interchangeably.

[0036] In this document, the terms "upper," "lower," "inner," "outer," "front," "rear," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In this document, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] In this document, "and / or" includes any and all combinations of one or more of the listed related items.

[0039] In this article, "multiple" means two or more, that is, it includes two, three, four, five, etc.

[0040] Example 1: like Figure 1, Figure 2 As shown, this embodiment provides a magnetic levitation flight wind tunnel speed measuring device based on an optical sensor and a scale, including a scale 1, which is set along the motion trajectory direction of the magnetic levitation flight wind tunnel motion platform 200; the scale 1 is provided with equally spaced hollows 11 along the axial direction; It also includes an optical probe 3 that moves with the motion platform 200; the cutout 11 and the non-cutout portion 12 between adjacent cutouts 11 can switch between blocking and passing the light beam emitted by the optical probe 3 to generate a switch signal. The switch signal is used to calculate the motion speed of the motion platform 200.

[0041] This invention utilizes a minimalist architecture consisting of a scale 1 with equidistant cutouts 11 fixed to the wind tunnel track 300 and an optical probe 3 that moves synchronously with the test model 100. It generates periodic switching electrical signals by switching the light beam on and off as it passes through the cutouts 11 and non-cutout areas of the scale 1. The fixed interval of the mechanically machined scale 1 is used as the absolute distance reference, and the real-time speed of the motion platform 200 is calculated by combining the time characteristics of the signal.

[0042] Specifically, in this embodiment, the scale 1 is fixedly installed along the motion trajectory direction of the maglev flight wind tunnel motion platform 200, i.e., the axial direction of the test track 300, and remains stationary throughout the entire process. The installation position matches the motion path of the optical probe 3, ensuring that the detection beam of the probe can stably illuminate the working surface of the scale 1 throughout the entire motion, without deviation or obstruction.

[0043] The scale 1 features evenly spaced perforated structures 11 along the axial direction of the platform's movement. Between adjacent perforated structures 11 are non-perforated sections 12 of equal width. These perforated and non-perforated sections 11 alternate along the movement direction, forming a periodic light-transmitting and light-blocking structure. The purpose is to convert the continuous linear displacement of the moving platform 200 into periodic on / off signals that are recognizable by the optical probe 3 and correspond one-to-one with the displacement, while simultaneously providing a fixed physical distance reference for velocity calculation.

[0044] The width ratio of the non-cutout portion 12 to the cutout portion 11 of scale 1 is defined as the duty cycle, with a value range of 0.1 to 1.0, preferably 0.5 in this embodiment. It can be adjusted according to the test speed range. A large duty cycle can be selected for low-speed test conditions to improve signal stability; a small duty cycle can be selected for high-speed test conditions to avoid signal aliasing at high speeds and ensure time resolution.

[0045] The thickness of scale 1 is usually 1~5mm, preferably 3mm, to balance workability and structural rigidity of the long track 300 installation; the height of scale 1 is designed to be adapted to the installation height of optical probe 3 to ensure effective coverage of the beam throughout the entire path.

[0046] In this embodiment, scale 1 is preferably made of non-ferromagnetic materials such as 304 / 316 stainless steel, high-strength aluminum alloy, carbon fiber composite material, etc., to completely avoid interference with the superconducting magnetic field of the maglev flight wind tunnel, while ensuring the straightness, structural rigidity and environmental stability of long-distance installation, and adapting to the working conditions such as airflow disturbance and temperature change in wind tunnel tests.

[0047] like Figure 5 As shown, in this embodiment, the scale 1 consists of two overlapping scales. The axial position of at least one of the two scales 1 is adjustable (i.e., it serves as an adjustment mechanism), which changes the area covered by the cutouts 11 of the two scales 1, thereby adjusting the width of the cutouts 11.

[0048] To facilitate adjustment of the width of the cutout 11, this embodiment uses two isoparametric scales 1 stacked one on top of the other along the beam propagation direction. The relative displacement of at least one scale 1 along the axial direction of the track 300 (i.e., the direction of movement of the motion platform 200) changes the overlapping light-transmitting area of ​​the cutout 11, achieving continuous stepless adjustment of the effective cutout width. This adapts to the full-condition speed measurement requirements of maglev wind tunnels, from low speed to ultra-high speed, without replacing the scales 1 or altering the core architecture of the speed measurement system. Of course, other adjustment methods can also be used to adjust the width of the cutout.

[0049] In this embodiment, the axis of scale 1 refers to the direction of motion of the maglev flight wind tunnel motion platform 200, that is, the entire extension direction of the test track 300, and also the length direction of scale 1.

[0050] The so-called overlapping arrangement refers to the arrangement of two scales 1 stacked one after the other along the beam propagation direction of the optical probe 3. The working surfaces of the two scales 1 are parallel to each other and parallel to the axis, and are on the beam path of the optical probe 3 throughout the entire process. The beam must pass through the cutouts 11 of the two scales 1 one after the other to complete the switching of the on and off states.

[0051] The overlap width of the cutout 11 areas of the two scales 1 along the axial direction is the effective cutout 11 width, which is the direct determining factor of the speed measurement algorithm and also the adjustment object of this scheme.

[0052] Assuming that the two rulers 1 are completely identical, initially, the cutouts 11 of the two rulers 1 are completely aligned along the axis, and the non-cutouts 11 are completely aligned with each other. At this time, the overlapping light-transmitting area of ​​the cutouts 11 of the two rulers 1 is the largest, and the effective cutout width 11 is equal to the designed width of the cutout 11 of a single ruler 1, which is the maximum value of the adjustment range.

[0053] When one of the scales 1 undergoes a relative displacement ΔX along the axial direction, the hollowed-out areas 11 of the two scales 1 are axially misaligned. The non-hollowed-out part 12 of one scale 1 will block part of the hollowed-out area 11 of the other scale 1. The overlapping light-transmitting area of ​​the hollowed-out area 11 decreases synchronously, and the effective width of the hollowed-out area 11 narrows linearly with the increase of the displacement.

[0054] For example, the width of the cutout 11 of a single ruler 1 is 5mm, and the width of the non-cutout 11 is 5mm. When the adjustable ruler 1 moves 2mm along the axis, the effective cutout 11 width = 5mm - 2mm = 3mm; when it moves 4mm, the effective cutout 11 width narrows to 1mm, realizing continuous stepless adjustment of the effective cutout 11 width.

[0055] In this embodiment, the two scales 1 include a fixed reference scale 101 and an axially adjustable scale 102. The fixed reference scale 101 is rigidly fixed to a dedicated mounting base on the maglev wind tunnel track 300 throughout its entire length, remaining stationary and serving as the distance and position reference for the entire scale 1 system. The axially adjustable scale 102 is stacked parallel to the fixed reference scale 101 and installed on an axial adjustment mechanism, such as a linear drive mechanism. It retains only a single degree of freedom of movement along the axial direction, without any deflection in the up, down, left, or right directions, ensuring that the parallelism and gap with the fixed scale 1 remain consistent throughout the adjustment process.

[0056] In this embodiment, the optical probe 3 is a switch-type signal generation unit that converts the physical changes of light transmission and shading of the scale 1 into an electrical signal that can be collected and calculated.

[0057] The optical probe 3 is rigidly fixed to the motion platform 200 of the maglev flight wind tunnel or mounted on the test model 100 on the platform via a special mounting bracket 2. It can move synchronously and linearly along the track 300 with the motion platform 200 without relative displacement. The beam emission end of the probe is always aligned with the working surface of the scale 1, ensuring that the beam and the hollow 11 / non-hollowed-out part 12 of the scale 1 work effectively throughout the motion.

[0058] The probe emits a stable detection beam. When the beam illuminates the hollow area 11 of the scale 1, it passes smoothly, and the probe outputs a corresponding level signal. When the beam illuminates the non-hollowed-out portion 12 between adjacent hollow areas 11, it is blocked, and the probe outputs the opposite level signal. As the platform continues to move, the alternating hollow areas 11 and non-hollowed-out portions 12 on the scale 1 continuously sweep across the detection beam, causing the beam to periodically pass through and be blocked. The optical probe 3 synchronously outputs a periodic switching square wave electrical signal that corresponds one-to-one with the movement displacement. The faster the platform moves, the higher the frequency of the square wave signal, achieving precise conversion from displacement to electrical signal.

[0059] More specifically, such as Figure 3As shown, when the optical probe 3 is a reflective type, the mounting bracket 2 includes a base plate 21 for fixed connection with the motion platform 200 and a vertical plate 22 for mounting the optical probe 3. The mounting bracket 2 is an integrated L-shaped structure, composed of the base plate 21 and the vertical plate 22, which are arranged perpendicularly at 90°. It can be formed by integrated milling, precision welding and other processes, with no unnecessary moving parts, extremely simple structure and extremely high reliability.

[0060] like Figure 4 As shown, when the optical probe 3 is a through-beam type, the mounting bracket 2 includes a column 23 for fixing to the motion platform 200. A crossbeam 24 perpendicular to the motion direction of the motion platform 200 is provided on the column 23. The crossbeam 24 is provided with a fixed seat 25 and a movable seat 26. The movable seat 26 can move along the crossbeam 24 to adjust the distance between it and the fixed seat 25. The transmitting end and receiving end of the through-beam probe are respectively provided on the fixed seat 25 and the movable seat 26. The scale 1 is located between the fixed seat 25 and the movable seat 26.

[0061] The crossbeam 24 is vertically fixed to the column 23 and serves as the main support for the fixed seat 25 and the movable seat 26. It also provides precise linear motion guidance for the movable seat 26, ensuring that the movable seat 26 can only move along an axis perpendicular to the direction of movement. This ensures that the probes on the fixed seat 25 and the movable seat 26 remain coaxial during the adjustment of the spacing.

[0062] The fixed base 25 is rigidly locked at the far end of the crossbeam 24 away from the column 23. It has no displacement adjustment capability and serves as the fixed reference for the entire optical path system. Its function is to support the transmitting or receiving end of the through-beam probe and provide a fixed coaxial reference point for the entire optical path.

[0063] The movable base 26 is installed on the guide structure of the crossbeam 24 and can move freely in a straight line along the axis of the crossbeam 24. It is a functional component for adjusting the probe spacing. Its function is to support the other end of the through-beam probe. By moving along the crossbeam 24, the distance between the probe and the fixed base 25 is adjusted to accommodate scales 1 of different thicknesses and probes of different specifications. At the same time, it always maintains strict coaxiality with the fixed base 25 during the movement to ensure the stability of the optical path.

[0064] In addition, this embodiment also includes an optical fiber amplifier and an electromagnetic shielding box 4. The optical probe 3 is connected to the optical fiber amplifier via an optical fiber. The optical fiber amplifier is encapsulated in the electromagnetic shielding box 4. The output end of the electromagnetic shielding box 4 is connected to a signal acquisition device 5. The signal acquisition device 5 is communicatively connected to a host computer 6. The host computer 6 is used to calculate the motion speed of the motion platform 200 based on the switch signal.

[0065] Fiber optic cables provide a channel for optical signal transmission, and fiber optic amplifiers process the optical signals, setting important parameters such as response time and light intensity.

[0066] The electromagnetic shielding box 4 is made of electromagnetic shielding material, preferably iron-based metal. The electromagnetic shielding box 4 has a power input interface and a signal output interface, providing electromagnetic shielding, power supply, and signal output functions for the fiber optic amplifier.

[0067] The signal acquisition device 5 is an analog signal acquisition device, comprising a signal acquisition card and a data acquisition chassis. The signal acquisition card is installed inside the data acquisition chassis. Preferably, the signal acquisition card is a voltage acquisition card with 24-bit analog-to-digital conversion, a range of ±10V, and a sampling rate of 102.4kHz. The signal acquisition card is connected to the electromagnetic shielding box 4 via a coaxial BNC cable, and the data acquisition chassis communicates with the host computer 6 via protocols such as USB and LAN.

[0068] The host computer 6 is an industrial control computer, pre-installed with operating systems such as Windows, and can be expanded to install industrial data acquisition software.

[0069] Example 2: This embodiment also provides a wind tunnel speed measurement method for maglev flight based on optical sensors and scales, applying the aforementioned maglev wind tunnel speed measurement device, see [link to documentation]. Figure 6 The specific steps include: Step 1: Complete the assembly of the speed measuring device based on the optical probe and scale, power on the system, and set the fiber optic amplifier parameters and data acquisition parameters under the condition that the test model is stationary. Step 2: Start the magnetic levitation drive system and send the test model launch command as a trigger signal to the data acquisition system to trigger signal acquisition; Step 3: After the test model has braked, the collected signals are processed by the following algorithm to obtain the speed-time history.

[0070] S1 performs time derivative calculation on the switching signal output by the optical probe to obtain the time derivative of the switching signal.

[0071] like Figure 7 As shown, the purpose of this step is to amplify the transition edge characteristics of the switching signal, filter out invalid information and background interference in the steady segment, highlight the instantaneous moment when the scale cutout / non-cutout edge sweeps across the beam, and provide a highly recognizable feature signal for subsequent time point locking.

[0072] Ideally, the switching signal output by the optical probe is a standard square wave. When the beam passes through the hollow area, it outputs a high level, and when it is blocked by the non-hollowed-out part, it outputs a low level. The voltage remains almost unchanged during the stable high and low level ranges, and only a voltage jump occurs at the moment of switching between hollow and non-hollow areas. In actual maglev wind tunnel operation, the original signal is superimposed with noise and clutter caused by electromagnetic interference, voltage drift, and airflow turbulence. Traditional threshold detection is prone to edge misjudgment. However, the derivative operation can make the output value containing DC drift and low-frequency noise in the steady segment approach 0, and only generate a sharp peak at the moment of voltage jump, thus separating the effective feature from the invalid interference at the source.

[0073] In this embodiment, the switching signal is a voltage signal. Before performing time derivative on the voltage signal, signal preprocessing such as amplification and singularity removal should be performed.

[0074] Specifically, using the formula: ; The time derivative of the voltage signal output by the optical probe is calculated; where, Let V(t) be the first derivative of the voltage signal V(t) with respect to time t, where V(t) is the voltage signal, t is time, and diff is the difference operator.

[0075] S2 performs peak detection on the time derivative of the switching signal and extracts the time points corresponding to all peaks.

[0076] From the differentiated signal, it is necessary to identify all effective peak values ​​of the beam sweeping across the corresponding open / non-open edges of the scale, and lock the absolute time coordinates corresponding to each edge to provide a time reference anchor point for the final velocity calculation. The time points corresponding to these peak values ​​correspond one-to-one with the physical positions on the scale. The difference between two adjacent time points is the time taken for the motion platform to travel a fixed distance on the scale, which is the time reference for the entire velocity measurement algorithm.

[0077] This step utilizes the following formula: ; Peak detection is performed on the time derivative of the voltage signal; where, It is a one-dimensional time series array that stores the time coordinates corresponding to all detected signal peaks. findpeaks() is the peak detection algorithm.

[0078] S3 calculates the motion speed of the motion platform based on the width of the cutout on the scale and the time difference of the peak time point.

[0079] This step uses the fixed physical dimensions of the scale as the absolute distance benchmark. Combined with the time difference between adjacent peak values, the real-time velocity of the motion platform is calculated using the physical formula: velocity = distance / time. Finally, the entire velocity-time history of the platform from launch, acceleration, constant speed, deceleration to braking is obtained, providing velocity benchmark data for aerodynamic testing. Figure 8 As shown.

[0080] The core of this step is to calculate the speed of motion by using the ratio of a fixed distance to the corresponding time. The formula is: ; Where v(t) is the velocity at time t, The width of the cutout.

[0081] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0082] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A wind tunnel speed measurement device for magnetic levitation flight based on an optical sensor and a scale, characterized in that: Includes a scale, which is set along the motion trajectory of the maglev flight wind tunnel motion platform; the scale has equally spaced cutouts along the axial direction; It also includes an optical probe that moves with the motion platform; the hollowed-out portion and the non-hollowed-out portion between adjacent hollowed-out portions can switch between blocking and passing the light beam emitted by the optical probe to generate a switching signal. The switch signal is used to calculate the motion speed of the motion platform; The optical probe is fixed to the motion platform using a mounting bracket; When the optical probe is a reflective type, the mounting bracket includes a base plate for fixed connection with the motion platform and an upright plate for mounting the optical probe; When the optical probe is a through-beam type, the mounting bracket includes a column for fixing to the motion platform, and a crossbeam perpendicular to the motion direction of the motion platform is provided on the column; the crossbeam is provided with a fixed seat and a movable seat, and the movable seat can move along the crossbeam to adjust the distance between it and the fixed seat; The transmitting and receiving ends of the through-beam probe are respectively located on a fixed base and a movable base, and the scale is located between the fixed base and the movable base.

2. The magnetic levitation flight wind tunnel speed measurement device based on an optical sensor and a scale according to claim 1, characterized in that: The ratio of the width of the non-cutout portion to the width of the cutout portion of the scale is the duty cycle, and the duty cycle ranges from 0.1 to 1.

0.

3. The magnetic levitation flight wind tunnel speed measurement device based on an optical sensor and a scale according to claim 1, characterized in that: The duty cycle is 0.

5.

4. The magnetic levitation flight wind tunnel speed measurement device based on an optical sensor and a scale according to claim 1, characterized in that: It also includes an adjustment mechanism for adjusting the width of the cutout.

5. The magnetic levitation flight wind tunnel speed measuring device based on an optical sensor and a scale according to claim 1, characterized in that: It also includes an optical fiber amplifier and an electromagnetic shielding box. The optical probe is connected to the optical fiber amplifier via an optical fiber. The optical fiber amplifier is encapsulated in the electromagnetic shielding box. The output end of the electromagnetic shielding box is connected to a signal acquisition device. The signal acquisition device is connected to a host computer for communication. The host computer is used to calculate the motion speed of the motion platform based on the switch signal.

6. The magnetic levitation flight wind tunnel speed measurement device based on an optical sensor and a scale according to claim 1, characterized in that: The scale is made of a non-ferromagnetic material with a thickness of 1-5 mm.

7. A magnetic levitation flight wind tunnel speed measurement device based on an optical sensor and a scale according to claim 4, characterized in that: The adjustment mechanism includes: an adjustment scale that is stacked on the front or rear side of the scale, the adjustment scale being able to reciprocate along the axial extension direction of the scale, thereby changing the cutout coverage area of ​​the two scales and thus adjusting the width of the cutout.

8. A magnetic levitation flight wind tunnel speed measuring device based on an optical sensor and a scale according to claim 7, characterized in that: It also includes a linear drive mechanism for driving the movement of the adjustment scale, through which the relative axial position of the two scales can be adjusted, thereby changing the width of the cutout.

9. A method for wind tunnel speed measurement of maglev flight based on optical sensors and scales, applied to the wind tunnel speed measurement device of maglev flight as described in any one of claims 1 to 8, characterized in that, include: The time derivative of the switching signal output by the optical probe is obtained by taking the time derivative. Peak detection is performed on the time derivative of the switching signal, and the time points corresponding to all peaks are extracted. The motion speed of the motion platform is calculated based on the width of the cutout on the scale and the time difference of the peak time point.

10. A wind tunnel speed measurement method for magnetic levitation flight based on an optical sensor and a scale, as described in claim 9, is characterized in that... The switching signal is a voltage signal, calculated using the formula: The time derivative of the voltage signal output by the optical probe is calculated; where, Let V(t) be the first derivative of the voltage signal V(t) with respect to time t, where V(t) is the voltage signal, t is time, and diff is the difference operator. Using the formula: Peak detection is performed on the time derivative of the voltage signal; where, It is a one-dimensional time series array that stores the time coordinates corresponding to all detected signal peaks. findpeaks() is the peak detection algorithm. Using the formula: Calculate the velocity of the motion platform; where v(t) is the velocity at time t. The width of the cutout.

Images