A system and method for determining time delay of a hypersonic vehicle imaging payload

Abstract

The application discloses a kind of high supersonic aircraft imaging load time delay determination systems, including imaging load;LED light source, as the imaging target of imaging load;Pulse width modulator, the duty cycle of control pulse signal is passed through, regulate and control LED light source brightness periodic change;Signal acquisition system, signal acquisition system is used to collect pulse signal of pulse width modulator output;And a determination method.The application adopts the mode of pulse width modulation, utilizes pulse width modulator by controlling the duty cycle of pulse signal, regulates and controls the LED light source brightness periodic change of imaging load target area, to contain time information in the image information obtained by imaging load, so as to calculate and determine the relationship between the average value of gray scale of image information light source area and the duty cycle of pulse signal by multiple experiments, further set the duty cycle periodic change of pulse signal, the trigger delay time of imaging load is obtained by determining the duty cycle corresponding to trigger time and imaging time.

Description

Technical Field

[0001] This invention relates to the field of hypersonic experimental technology, specifically to a system and method for measuring the time delay of imaging payloads of hypersonic vehicles. Background Technology

[0002] Optical imaging payloads are critical systems for the normal operation of weapon platforms such as hypersonic kinetic energy interception, star navigation, and reconnaissance. During the design process, wind tunnel tests are required to evaluate the impact of aero-optical effects on the imaging payload.

[0003] Achieving hypersonic flight conditions in a wind tunnel places extremely high demands on the wind tunnel's driving energy. All wind tunnels are pulse-type wind tunnels with short effective experimental time. The effective time of hypersonic wind tunnels at Mach 9 and above, both domestically and internationally, does not exceed forty milliseconds. However, the imaging payload of hypersonic weapons is designed for real flight environments, operates in continuous mode, and has a low imaging frequency. Only one frame of image can be acquired within the effective experimental time of the wind tunnel.

[0004] The design conditions for the imaging payload differ significantly from those for wind tunnel testing. Timing coordination is crucial to synchronize the wind tunnel flow field and the imaging payload's exposure time, necessitating the determination of the time delay characteristics between receiving the trigger signal and the actual exposure. However, since the imaging payload output only provides light intensity information about the imaging target and contains no time information, the time delay of the imaging payload cannot be determined. Summary of the Invention

[0005] The purpose of this invention is to provide a system and method for measuring the imaging payload delay of hypersonic vehicles, so as to solve the technical problem in the prior art that the imaging payload output results only contain the light intensity information of the imaging target and do not contain any time information, thus making it impossible to determine the imaging payload delay.

[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0007] A hypersonic vehicle imaging payload time delay measurement system includes:

[0008] An imaging payload, used to acquire image information of a target region;

[0009] An LED light source is disposed in the target area as the imaging target of the imaging payload, so as to form a light source area in the image information acquired by the imaging payload;

[0010] A pulse width modulator is electrically connected to the LED light source, and the pulse width modulator controls the periodic change of the brightness of the LED light source by controlling the duty cycle of the pulse signal.

[0011] A signal acquisition system, which is electrically connected to the pulse width modulator to acquire the pulse signal of the pulse width modulator;

[0012] The process involves recording the pulse signal of the pulse width modulator and the image information acquired by the imaging payload. After conducting multiple experiments with varying duty cycles, the correspondence between the average grayscale value of the light source region in the image information and the duty cycle of the pulse signal is determined.

[0013] The duty cycle of the pulse width modulator is further set to change periodically, synchronously triggering the signal acquisition system and the imaging payload, recording pulse signals and image information. By comparing the duty cycle of the pulse signal at the trigger time with the duty cycle corresponding to the average gray value of the light source area in the image information, the interval between the pulse signal of the pulse width modulator and the image capture time of the imaging payload is determined, that is, the trigger delay time of the imaging payload.

[0014] As a preferred embodiment of the present invention, the pulse width modulator controls the periodic change of the brightness of the LED light source so as to include time information in the brightness change. The image information acquired by the imaging payload includes the average gray value of the light source area, and is converted into time information through the relationship between the average gray value of the light source area and the duty cycle.

[0015] Among them, the relationship between the average grayscale value and duty cycle of the light source area in the image information was pre-calibrated and determined after multiple experiments.

[0016] As a preferred embodiment of the present invention, it further includes:

[0017] A delayed pulse generator, electrically connected to the pulse width modulator, the imaging payload, and the signal acquisition system, is used to output three trigger signals to trigger the imaging payload, the pulse width modulator, and the signal acquisition system respectively.

[0018] The pulse width modulator, the signal acquisition system, and the imaging payload start working after receiving the trigger signal, and the signal acquisition system and the imaging payload receive the trigger signal later than the pulse width modulator.

[0019] As a preferred embodiment of the present invention, it further includes:

[0020] A computer that is electrically connected to and controls the signal acquisition system and the imaging payload.

[0021] To address the aforementioned technical problems, the present invention further provides the following technical solution:

[0022] A measurement method using the above-mentioned imaging load time delay measurement system includes the following steps:

[0023] Step 100: After setting the output pulse frequency of the pulse width modulator, fix the exposure time of the imaging load, set the duty cycle of the pulse width modulator to 0, and delay the triggering of the pulse width modulator by the imaging load to image the LED light source of the imaging target, and process to obtain the average gray value of the light source area of ​​the image information.

[0024] Step 200: Change the duty cycle and repeat step 100 until the duty cycle is 1. Use the least squares method to fit the duty cycle and average gray value of the pulse signal to obtain the correspondence between the average gray value of the light source area and the duty cycle in the image information of the imaging payload.

[0025] Step 300: Set the duty cycle to change linearly from 1 to 0 at a fixed frequency so that the light source brightness changes linearly at the same frequency. After the pulse width modulator starts working, it triggers the start of the imaging payload and signal acquisition system to acquire the image information of the imaging payload and the pulse signal of the pulse width modulator.

[0026] Step 400: Check the duty cycle of the pulse signal of the pulse width modulator at the trigger time, and use digital image processing methods to obtain the average gray value of the light source area in the image information. Combine the correspondence between the average gray value of the imaging payload and the duty cycle obtained in step 200 to determine the duty cycle corresponding to the imaging time, and determine the time interval between the two corresponding duty cycles based on a fixed frequency, which is the trigger delay time of the imaging payload.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention employs pulse width modulation, utilizing a pulse width modulator to control the duty cycle of the pulse signal, thereby periodically varying the brightness of the LED light source in the target area of ​​the imaging payload. This allows time information to be included in the image information acquired by the imaging payload. Through multiple experiments, the relationship between the average grayscale value of the light source area in the image information and the duty cycle of the pulse signal is calculated and determined. Furthermore, the duty cycles corresponding to the triggering time and the imaging time are determined to obtain the trigger delay time of the imaging payload. Attached Figure Description

[0029] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structural composition of the hypersonic vehicle imaging payload time delay measurement system provided in an embodiment of the present invention;

[0031] Figure 2A schematic diagram of the pulse width modulator output signal and imaging payload acquisition results under different duty cycle settings of the hypersonic vehicle imaging payload time delay measurement system provided in an embodiment of the present invention;

[0032] Figure 3 A schematic diagram showing the relationship between the average grayscale value of the imaging payload and the duty cycle of the hypersonic vehicle imaging payload time delay measurement system provided in an embodiment of the present invention.

[0033] Figure 4 A schematic diagram illustrating the change of duty cycle over time in the hypersonic vehicle imaging payload time delay measurement system provided in an embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram of the trigger signal timing relationship of the hypersonic vehicle imaging payload time delay measurement system provided in an embodiment of the present invention;

[0035] Figure 6 A schematic diagram of the trigger signal and pulse width modulation pulse signal recorded by the information acquisition system of the hypersonic vehicle imaging payload time delay measurement system provided in an embodiment of the present invention;

[0036] Figure 7 This is a schematic diagram of the imaging load imaging results of the hypersonic vehicle imaging load time delay measurement system provided in an embodiment of the present invention. Detailed Implementation

[0037] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] like Figure 1 As shown, the present invention provides a hypersonic vehicle imaging payload time delay measurement system, comprising:

[0039] Imaging payload: The imaging payload is used to acquire image information of the target area.

[0040] LED light source, the LED light source is set in the target area as the imaging target of the imaging payload, so as to form the light source area in the image information acquired by the imaging payload;

[0041] A pulse width modulator is electrically connected to an LED light source, and the pulse width modulator controls the periodic change of the brightness of the LED light source by controlling the duty cycle of the pulse signal.

[0042] The signal acquisition system is electrically connected to the pulse width modulator to acquire the pulse signal from the pulse width modulator.

[0043] The experiment involved recording the pulse signal of the pulse width modulator and the image information acquired by the imaging payload. After conducting multiple experiments with varying duty cycles, the correspondence between the average gray value of the light source region in the image information and the duty cycle of the pulse signal was determined.

[0044] The duty cycle of the pulse width modulator is further set to change periodically, and the signal acquisition system and imaging payload are triggered synchronously. The pulse signal and image information are recorded. By comparing the duty cycle of the pulse signal at the trigger time with the duty cycle corresponding to the average gray value of the light source area in the image information, the interval between the pulse signal of the pulse width modulator and the image capture time of the imaging payload is determined, that is, the trigger delay time of the imaging payload.

[0045] The imaging payload delay measurement system of this invention mainly utilizes a pulse width modulator to control the duty cycle of the pulse signal, thereby regulating the periodic change in the brightness of the LED light source. This allows the brightness change of the LED light source to include time information, enabling the acquisition of image information after the imaging payload is delayed by the pulse width modulator triggering. After multiple experiments with different duty cycles, the correspondence between the average grayscale value of the image information and the duty cycle of the pulse signal is determined. Furthermore, the periodic change of the pulse width modulator duty cycle is set to synchronously trigger the signal acquisition system and the imaging payload, recording the pulse signal and the image of the imaging target. By comparing the duty cycle of the pulse width modulator pulse signal at the trigger moment with the duty cycle corresponding to the average grayscale value of the image, the time interval, i.e., the trigger delay time of the imaging payload, is determined based on the two duty cycles.

[0046] Compared to conventional imaging payloads that lack time information, making it difficult to calibrate the time delay characteristics of imaging payloads, this invention employs pulse width modulation (PWM). A PWM modulator controls the duty cycle of the pulse signal to periodically change the brightness of the LED light source in the target area of ​​the imaging payload, thus incorporating time information into the image information acquired by the imaging payload. After multiple experiments with varying the duty cycle, the correspondence between the average grayscale value of the light source area in the image information and the duty cycle of the pulse signal is determined. Furthermore, the periodic change of the PWM duty cycle is set to synchronously trigger the signal acquisition system and the imaging payload, recording the pulse signal and the target image. By comparing the duty cycle of the PWM pulse signal at the trigger moment with the duty cycle corresponding to the average grayscale value of the light source area in the image, the trigger delay time of the imaging payload is obtained.

[0047] Among them, the pulse width modulator controls the periodic change of the brightness of the LED light source so as to include time information in the brightness change. The image information acquired by the imaging payload includes the average gray value of the light source area, and is converted into time information through the relationship between the average gray value of the light source area and the duty cycle.

[0048] The relationship between the average grayscale value of the light source area and the duty cycle in the image information was pre-calibrated and determined after multiple experiments.

[0049] In other words, after acquiring the image of the LED light source, the imaging payload determines the time information by combining the correspondence between the average gray value of the light source area in the image information and the duty cycle of the pulse signal.

[0050] The delayed pulse generator is electrically connected to the pulse width modulator, imaging payload, and signal acquisition system. It is used to output three trigger signals to trigger the pulse width modulator, imaging payload, and signal acquisition system respectively.

[0051] The pulse width modulator, signal acquisition system, and imaging payload start working after receiving the trigger signal, and the signal acquisition system and imaging payload receive the trigger signal later than the pulse width modulator.

[0052] That is, of the three trigger signals output by the delayed pulse generator, one is used to trigger the pulse width modulator to work, while the other two are delayed compared to the first trigger signal acquisition system and imaging payload. The signal acquisition system works after receiving the trigger signal to acquire the pulse signal of the pulse width modulator.

[0053] The computer is electrically connected to and controls the signal acquisition system and the imaging payload. The computer can process the pulse signal acquired by the signal acquisition system and the image information acquired by the imaging payload to determine the correspondence between the average gray value of the light source area in the image information and the duty cycle of the pulse signal. By comparing the duty cycle of the pulse signal at the trigger time with the duty cycle corresponding to the average gray value of the light source area in the image information, the interval between the pulse signal of the pulse width modulator and the image capture time of the imaging payload is determined, that is, the trigger delay time of the imaging payload.

[0054] Based on the aforementioned imaging payload time delay measurement system, a measurement method is provided, comprising the following steps:

[0055] Step 100: After setting the output pulse frequency of the pulse width modulator, fix the exposure time of the imaging load, set the duty cycle of the pulse width modulator to 0, and delay the triggering of the pulse width modulator by the imaging load to obtain the average gray value of the light source area of ​​the image information.

[0056] Step 200: Change the duty cycle and repeat step 100 until the duty cycle is 1. Use the least squares method to fit the average gray value of the light source region of the image and the pulse duty cycle to obtain the correspondence between the average gray value of the light source region and the duty cycle in the image information of the imaging payload.

[0057] Step 300: Set the duty cycle to change linearly from 1 to 0 at a fixed frequency so that the light source brightness changes linearly at the same frequency. Start the pulse width modulator, imaging payload and signal acquisition system, and record the image information acquired by the imaging payload and the pulse signal of the pulse width modulator respectively.

[0058] Step 400: Check the duty cycle of the pulse signal of the pulse width modulator at the trigger time, and use digital image processing methods to obtain the average gray value of the light source area in the image information. Combine the correspondence between the average gray value of the imaging payload and the duty cycle obtained in step 200 to determine the duty cycle corresponding to the imaging time, and determine the time interval between the two corresponding duty cycles based on a fixed frequency, which is the trigger delay time of the imaging payload.

[0059] Specifically, the calibration process is illustrated using an imaging payload with a frame rate of 20Hz and an exposure time of 5ms as an example.

[0060] The pulse width modulator output pulse frequency is set to 10kHz, and the computer is connected to the signal acquisition system and imaging payload.

[0061] The correspondence between the average grayscale value of the light source region and the duty cycle of the pulse width modulator in the image information acquired by the calibrated imaging payload:

[0062] With a fixed exposure time for the imaging payload, the duty cycle of the microcontroller program is set to 0. The delayed pulse generator first triggers the pulse width modulator, initiating its operation, and then triggers the imaging payload 1 ms later. The imaging payload captures an image of the LED light source, and image processing methods are used to obtain the average grayscale value of the light source area. The above process is repeated by changing the duty cycle until it reaches 1. To ensure calibration accuracy, at least 20 sets of data should be provided. Figure 2 The figures show the output pulse signal of the pulse width modulator and the imaging payload image when the duty cycle is set to 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, respectively.

[0063] Then, the least squares method is used to fit the data to obtain the correspondence between the average gray level of the imaging payload and the duty cycle. For example... Figure 3 As shown, the fitted relationship is: average gray value = 1577.7 × duty cycle + 0.79.

[0064] By changing the duty cycle settings in the microcontroller program to control the duty cycle linearly from 1 to 0 at a frequency of 20Hz, the brightness of the light source will also change linearly at a frequency of 20Hz. Figure 4 As shown, the brightness of the light source changes linearly at a frequency of 20Hz.

[0065] Prepare a signal acquisition system. One channel of the signal acquisition system records the changes in the trigger signal of the delayed pulse generator, and another channel records the pulse signal of the pulse width modulator that controls the brightness of the light source.

[0066] Calibration begins with the computer setting the signal acquisition system and imaging payload to trigger mode. Using a DG535 pulse generator as the trigger signal source, the pulse width modulator is first triggered via channel A of the delayed pulse generator. One ms later, channel B triggers the signal acquisition system, and channel C triggers the imaging payload, initiating its operation. The acquisition system records the pulse width modulator pulse signal, and the imaging payload captures the image of the light source. The timing relationship of the trigger signals is as follows: Figure 5 As shown.

[0067] By using a computer to view the recorded results of the signal acquisition system, the duty cycle of the pulse width modulator pulse signal at the trigger moment is determined. Digital image processing methods are then used to obtain the average grayscale value of the light source area in the image captured by the imaging payload. The duty cycle corresponding to the imaging moment is determined by combining the obtained average grayscale value with the duty cycle.

[0068] Since the duty cycle is set to change linearly at 20Hz, the corresponding time interval can be determined after determining the values ​​of the two duty cycles. This time interval is the trigger delay time of the imaging payload. Figure 6 The signal acquisition system's acquisition results are shown below. The red dashed line represents the acquired trigger signal, and the blue solid line represents the acquired pulse width modulation (PWM) signal. The trigger signal occurs at 1.0 ms. By checking the duration of the high and low levels of the PWM signal at that time, the duty cycle is determined to be 0.98. The imaging payload's imaging results are as follows: Figure 7 As shown, the average grayscale value of the light source area in the image is 1152.5 using digital image processing methods. Based on the correspondence between the average grayscale value of the imaging payload and the duty cycle obtained from the calibration, the duty cycle at the imaging time can be determined to be 0.73. Since the duty cycle change frequency is 20Hz, the imaging delay time of the imaging payload can be determined to be (0.98-0.73) / 20=12.5ms.

[0069] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A system for measuring the time delay of imaging payloads of hypersonic vehicles, characterized in that, include: An imaging payload, used to acquire image information of a target region; An LED light source is disposed in the target area as the imaging target of the imaging payload, so as to form a light source area in the image information acquired by the imaging payload; A pulse width modulator is electrically connected to the LED light source, and the pulse width modulator controls the periodic change of the brightness of the LED light source by controlling the duty cycle of the pulse signal. A signal acquisition system, which is electrically connected to the pulse width modulator to acquire the pulse signal of the pulse width modulator; The process involves recording the pulse signal of the pulse width modulator and the image information acquired by the imaging payload. After conducting multiple experiments with varying duty cycles, the correspondence between the average grayscale value of the light source region in the image information and the duty cycle of the pulse signal is determined. The duty cycle of the pulse width modulator is further set to change periodically, synchronously triggering the signal acquisition system and the imaging payload, recording pulse signals and image information. By comparing the duty cycle of the pulse signal at the trigger time with the duty cycle corresponding to the average gray value of the light source area in the image information, the interval between the pulse signal of the pulse width modulator and the image capture time of the imaging payload is determined, that is, the trigger delay time of the imaging payload.

2. The hypersonic vehicle imaging payload time delay measurement system according to claim 1, characterized in that, The pulse width modulator controls the periodic change of the brightness of the LED light source to include time information in the brightness change. The image information acquired by the imaging payload includes the average gray value of the light source area and is converted into time information through the relationship between the average gray value of the light source area and the duty cycle. The relationship between the average grayscale value of the light source area and the duty cycle in the image information was pre-calibrated and determined after multiple experiments.

3. The hypersonic vehicle imaging payload time delay measurement system according to claim 2, characterized in that, Also includes: A delayed pulse generator, electrically connected to the pulse width modulator, the imaging payload, and the signal acquisition system, is used to output three trigger signals to trigger the imaging payload, the pulse width modulator, and the signal acquisition system respectively. The pulse width modulator, the signal acquisition system, and the imaging payload start working after receiving the trigger signal, and the signal acquisition system and the imaging payload receive the trigger signal later than the pulse width modulator.

4. The hypersonic vehicle imaging payload time delay measurement system according to claim 3, characterized in that, Also includes: A computer that is electrically connected to and controls the signal acquisition system and the imaging payload.

5. A method for measuring the imaging payload time delay using the imaging payload time delay measurement system according to any one of claims 1-4, characterized in that, Includes the following steps: Step 100: After setting the output pulse frequency of the pulse width modulator, fix the exposure time of the imaging load, set the duty cycle of the pulse width modulator to 0, and delay the triggering of the pulse width modulator by the imaging load to image the LED light source of the imaging target, and process to obtain the average gray value of the light source area of ​​the image information. Step 200: Change the duty cycle and repeat step 100 until the duty cycle is 1. Use the least squares method to fit the duty cycle and the average gray value of the pulse signal to obtain the correspondence between the average gray value of the light source area and the duty cycle in the image information of the imaging payload. Step 300: Set the duty cycle to change linearly from 1 to 0 at a fixed frequency so that the light source brightness changes linearly at the same frequency. After the pulse width modulator starts working, it triggers the start of the imaging payload and signal acquisition system to acquire the image information of the imaging payload and the pulse signal of the pulse width modulator. Step 400: Check the duty cycle of the pulse signal of the pulse width modulator at the trigger time, and use digital image processing methods to obtain the average gray value of the light source area in the image information. Combine the correspondence between the average gray value of the imaging payload and the duty cycle obtained in step 200 to determine the duty cycle corresponding to the imaging time, and determine the time interval between the two corresponding duty cycles based on a fixed frequency, which is the trigger delay time of the imaging payload.

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