Target position resolving method and device based on distributed single-phase limited laser detector

Abstract

The invention provides a target position resolving method and device based on a distributed single-phase limited laser detector. According to the method, the structural form of a traditional four-quadrant laser detector is changed, four quadrants are separated and placed in four directions respectively, and the method has the advantages of being easy to install, capable of being transplanted and low in cost. On the basis of not changing the appearance and the structure of the original system, the complexity of a software processing algorithm is increased, so that a target position resolving unit is conveniently added; through verification of a prototype, a set of complete solution is provided. The technology has wide application prospects and huge market requirements.

Description

Technical Field

[0001] The present invention belongs to the field of laser guidance, and specifically relates to a method and device for resolving the target position based on a distributed single-quadrant laser detector. Background Art

[0002] Currently, the commonly used laser semi-active guidance technology at home and abroad almost all adopts the structure of a traditional four-quadrant detector. The target surface of this detector is divided into four regions, representing the four directions of xy respectively. When the laser spot irradiates the target surface, different charges are generated according to the different illumination amounts in the four regions. These charges are amplified and converted into voltage signals, and then read and processed to obtain the target position. The problems existing in this method include:

[0003] 1. The four-quadrant laser detector and its optical system must be placed at the very front end of the guidance system, otherwise they will be blocked by other components on the system and unable to receive laser signals.

[0004] 2. The four regions on the detector target surface are close to each other, and signal crosstalk and coupling effects are extremely likely to occur, that is, even if there is no laser irradiation in a certain region, charge accumulation and amplification will occur, and the generated voltage will be collected, so it will inevitably cause a large error in the calculation of position accuracy.

[0005] 3. In order to minimize the interference between the signals of the four-quadrant detector, it is necessary to reduce the sensitivity and responsiveness of the target surface to light; however, this will also affect the detection distance index of the detector; therefore, the detection distance of the four-quadrant detector is generally not too far, and even if the index meets the requirements, the price is relatively expensive. Summary of the Invention

[0006] Aiming at the deficiencies of the above method, the purpose of the present invention is to provide a method and device for resolving the target position based on a distributed single-quadrant laser detector, which changes the target position calculation method of the traditional four-quadrant laser detection system, and relies on single-quadrant detectors distributed in four different directions to simultaneously collect target surface signals for fusion fitting to achieve target position resolution, and obtain a guidance detection signal representing the target position.

[0007] The technical solution adopted by the present invention to solve its technical problems is:

[0008] A method for resolving the target position based on a distributed single-quadrant laser detector, which changes the target position calculation method of the traditional four-quadrant laser detection system, and relies on single-quadrant detectors distributed in four different directions to simultaneously collect target surface signals for fusion fitting to achieve target position resolution, and obtain a guidance detection signal representing the target position. The method includes the following steps:

[0009] S1) Target position acquisition and calculation: Control the distributed detector to collect the voltage values of the four-way spot areas respectively, set the fitting range, adjust the step size, and perform iterative fitting calculations repeatedly to obtain the fitting coordinates (x′, y′) values of the target position after four-way fusion that meet the error threshold requirements, and output them as the target position detection signal for the target surface positioning of the distributed laser detector;

[0010] S2) Anti-high repetition frequency interference processing: For the target surface positioning detection signal, set the time gate width, extract the time-domain aliased signal within the time gate, and extract the time-domain interference signal outside the time gate; Filter the interference signal in the aliased signal and retain the target position guidance signal.

[0011] The steps of setting the fitting range, adjusting the step size, performing iterative fitting calculations repeatedly, and obtaining the fitting coordinates (x′, y′) values of the target position after four-way fusion that meet the error threshold requirements include:

[0012] 1a) Collect the voltage values S1, S2, S3, S4 of the four-way detectors respectively, and use formula 5 to calculate the fusion calculation value (S x , S y ) of the detection position;

[0013] 1b) Substitute it into the two-dimensional fitting function Q to obtain the fitting coordinates (x′, y′) values of the target position after fusion;

[0014] 1c) Within the range of plus or minus 3% of (x′, y′), take the fitting coordinates (x′, y′) values after fusion as (x, y) and substitute them into the spot shadow area calculation formula with a step size of 1‰ to obtain the spot shadow areas S 1’ , S 2’ , S 3’ , S 4’ of the four-way fitting, that is, the voltage values obtained by fitting calculation;

[0015] 1d) Compare S 1’ , S 2’ , S 3’ , S 4’ with the collected voltage values S1, S2, S3, S4. If the error does not exceed 5‰, it is considered the best fitting value, and the (x′, y′) value at this time is the final fitting coordinates of the target position.

[0016] It is necessary to establish the spot shadow area calculation formula in advance, and the steps are as follows:

[0017] Divide the four quadrants according to the structure of the distributed detector and the relationship between the laser spot positions. Let the center coordinates of each spot be (x, y), and the radii of the detector and the spot be R. Then the calculation formulas for the spot shadow areas S1, S2, S3, S4 detected by each path are:

[0018] 2 - 14y2

[0019] (Formula 2)

[0020] (Formula 3)

[0021] (Formula 4)

[0022] The formula 5 is the division of the sum and difference to obtain the fusion calculation value (S x , S y ) at the detection position:

[0023] S x = (S1 - S3) / (S1 + S3)

[0024] S y = (S2 - S4) / (S2 + S4)

[0025] The two-dimensional fitting function Q is obtained by performing two-dimensional function fitting on the fusion calculation value (S x , S y ) at the detection position and the true coordinates (x, y) of the target position.

[0026] In the aliased signal, the interference signal is filtered out and the target guidance signal is retained as follows: The aliased signal and the interference signal are respectively subjected to Fourier transform to obtain the spectral characteristics of the aliased signal and the interference signal. The interference spectrum is screened out, and then the inverse Fourier transform is performed back to the time domain to obtain the interference-free target guidance signal.

[0027] A target position calculation device based on a distributed single-phase limit laser detector includes a distributed detection unit, a processing unit, and a memory; the distributed detection unit is used to synchronously collect distributed target surface images and send them to the processing unit, and the processing unit calls the program in the memory, executes the method steps as described above, calculates the target position on the distributed target image, and then performs anti-high repetition frequency interference processing to finally obtain the guidance signal representing the target position.

[0028] The distributed detection unit is four-way detectors evenly arranged at equal distances outward from the target center in the vertical plane according to the four-quadrant principle. The detector lenses are directed towards the target and are used to respectively collect laser voltage signals.

[0029] The target position calculation device based on the distributed single-phase limit laser detector further includes a main frame for distributing and installing the four-way detectors, the processing unit, and the memory.

[0030] The present invention changes the traditional target position calculation method of the four-quadrant laser detection system and realizes target position calculation by relying on single-phase limit detectors distributed in four different directions. This method has the following advantages:

[0031] 1. The single-quadrant detector has a simple structure, making it easy to design, produce, and test. It has low costs and obvious price advantages. Its detection response rate and signal-to-noise ratio are significantly improved compared to the four-quadrant detector.

[0032] 2. The distributed structure is easy to install and debug, and can optimize the guidance process without significantly changing the original system structure; while the traditional four-quadrant detector method requires significant modification of the existing system structure, so its application scenarios are limited.

[0033] 3. When using the four-quadrant detector, the coupling and crosstalk effects between each signal path need to be considered and cannot be eliminated, only minimized; while the distributed structure completely eliminates these effects, so its detection distance and position calculation accuracy are much better than the four-quadrant structure.

[0034] 4. The software processing process of the distributed structure is simpler and more efficient than that of the four-quadrant structure; the design difficulty of the optical system is also greatly reduced. Therefore, this method of target calculation will surely be widely applied in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the flowchart of the method of the present invention;

[0036] Figure 2 is the schematic diagram of the basic structure of the distributed detector;

[0037] Figure 3 is the schematic diagram of the circuit structure;

[0038] Figure 4 is the schematic diagram of the overall chip and the peripheral circuit;

[0039] Figure 5 is the diagram of the structure of the distributed detector and the relationship between the laser spot position;

[0040] Figure 6 is the detailed diagram of the position relationship of each path of the detector;

[0041] Figure 7 is the error diagram of the target position and the true value obtained by directly using the function fitting function;

[0042] Figure 8 is the error diagram of the target position and the true value after further traversal processing based on the fitted target position;

[0043] Figure 9 is the flowchart of high-repetition-rate interference signal filtering based on high-speed data acquisition technology;

[0044] Figure 10 is the diagram of the position relationship of the distributed single-quadrant laser detector. DETAILED IMPLEMENTATION MANNER

[0045] To make the above objects, features and advantages of the present invention more obvious and understandable, the following further details the specific implementation methods of the present invention in conjunction with the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the invention. Therefore, the present invention is not limited by the specific implementations disclosed below.

[0046] In response to the requirements of low-cost guidance transformation of non-guided systems and the development of new guidance systems, the present invention conducts research on distributed laser semi-active guidance technology systems, breaks through technologies such as weak optoelectronic signal processing, anti-deception, high-repetition-frequency interference, and target angle deviation acquisition under the condition of wing deployment error, develops a principle prototype of a distributed laser semi-active guidance component, and completes laboratory simulation tests, providing important technical support for future in-depth research on this method.

[0047] This method mainly includes four aspects:

[0048] I. Weak high-frequency narrow pulse signal processing technology

[0049] For high-frequency narrow pulse signals, the traditional processing method is to use peak holding. Its advantages are low cost and simple structure, and it only requires a suitable amplifier and resistor-capacitor components to work; however, its disadvantages are also obvious. It can only hold signals above a certain amplitude and pulse width, and the effect depends severely on whether the resistor-capacitor values are appropriate. Even for components with the same nominal value, the errors inherent in them can cause changes in the output results.

[0050] To overcome the above disadvantages, this project plans to use a high-speed analog-to-digital acquisition circuit instead of a peak holding circuit. As long as the bandwidth of the acquisition circuit is high enough, it can fully reflect information such as the amplitude and phase of the input signal; thus, it has the advantages of high integration and easy debugging. Without increasing the circuit cost and design complexity, the highest sampling rate can reach 1 Ghz / s.

[0051] II. Target position acquisition and calculation technology

[0052] Considering the structural characteristics of distributed guidance, it is quite different from the familiar four-quadrant detector form. When the latter outputs position coordinates, X and Y are independent of each other, so there is no need to consider the coupling problem between X and Y when solving the position coordinates. However, for distributed guidance, X and Y are coupled at all times, and the previous algorithms are not applicable. Through strict mathematical derivation, we established an expression for the voltage relationship between the target position and the four detectors, and carried out engineering transformation, achieving the purpose of neither affecting the accuracy nor being easy to implement on an embedded hardware platform.

[0053] III. Anti-high-repetition-frequency interference technology

[0054] Anti-high-repetition-rate interference is a problem that all laser guidance systems have to face. Traditional peak-holding means do not have any ability to resist high-repetition-rate interference; this method relies on weak high-frequency narrow pulse signal processing technology to collect interference signals and normal signals separately in the time domain, and then converts them to the frequency domain through FFT; according to their spectral differences in the frequency domain, a suitable filter is designed to filter out the interference signals, and then the remaining normal signals are transformed back to the time domain through IFFT, achieving the purpose of filtering.

[0055] The working principle of the laser detector is: the stronger the laser energy per unit area on the target surface irradiated by the laser, the larger the area of the target surface irradiated, and the higher the voltage value output by the detector.

[0056] As Figure 1 shown, a method for resolving the target position of a distributed single-phase limit laser detector changes the traditional target position calculation method of a four-quadrant laser detection system, and relies on single-phase limit detectors distributed in four different directions to simultaneously collect target surface signals for fusion fitting to achieve target position resolution, obtaining a guidance detection signal representing the target position. The method includes the following steps:

[0057] S1) Target position acquisition and resolution: Control the distributed detectors to separately collect the voltage values of the four-way spot areas, set the fitting range, adjust the step size, and repeatedly iterate for fitting and resolution to obtain the target position fitting coordinates (x′, y′) value after four-way fusion that meets the error threshold requirements, and output it as the target surface positioning detection signal of the distributed laser detector;

[0058] S2) Anti-high-repetition-rate interference processing: For the target surface positioning detection signal, set the time gate width, extract the time-domain aliased signal within the time gate, and extract the time-domain interference signal outside the time gate; filter out the interference signal in the aliased signal and retain the target position guidance signal. 1. Weak high-frequency narrow pulse signal processing technology For weak high-frequency narrow pulse signals, if we want to obtain their amplitude and phase information in real time and without distortion, the requirements for the processing circuit are high bandwidth and high sampling rate, so as to ensure that the obtained signal is real and effective. To achieve this purpose and not significantly increase the implementation difficulty and cost of the circuit, we choose the common and well-supplied high-speed analog-to-digital acquisition chip ADC08D502 on the market, whose highest sampling rate is 500MHZ, that is, the sampling interval is 2ns. To further increase the sampling rate and considering the limitation of the board space at the same time, we divide each clock signal into two, and one of them is inversely connected to another high-speed acquisition chip; in this way, it is equivalent to having data acquisition points at both the rising edge and the falling edge of the clock, thus achieving the purpose of a 1GHZ sampling rate.

[0059] The processing of the clock source is also crucial. If the four clock sources are not synchronized, it will lead to inconsistent signal acquisition times in the four quadrants, affecting the position calculation accuracy. Therefore, we use four synchronizable clocks as the excitation source for the high-speed acquisition chip, ensuring the consistency of the four-channel signals at the acquisition time point and not introducing additional errors.

[0060] For the selection of the main control chip, we choose the spartan-7 series FPGA of XILINX as the main control chip. Its LVDS input rate can reach up to 680MHZ / S at most, meeting our requirements. This FPGA is also a commonly used product on the market.

[0061] Figure 2 It is a schematic diagram of the basic structure of the distributed detector. In the figure, there are a total of four detection units. Each detection unit includes an optical lens, a single-phase detector, and a processing circuit. The output signals of the four detection units are connected to the processing unit at the back end. Figure 3 It is a schematic diagram of the circuit structure, specifically indicating the positional relationship of each part. The overall chip and peripheral circuit design is as Figure 4 shown in the figure. In the figure, HIGH PASS FILTER is to perform high-pass filtering on the original signal output by the detector (chip ADA4896); AGC is to adjust the gain of the signal (chip AD8367); HIGH speed acquisition is high-speed data acquisition (model ADC08D502); XILINX in the middle is the signal processing module (model XC7S50); Clock around is the synchronous clock.

[0062] 2. Target position acquisition technology

[0063] Different from the traditional four-quadrant detector structure, the structure of the distributed detector and the relationship between the laser spot position are as Figure 5 shown. The detailed positional relationship for each path is as Figure 6 shown. Let the center coordinates of the light spot be (x, y), and the radii of both the detector and the light spot be R. After strict mathematical derivation, the expressions for the areas of the four shaded regions are as follows: 2 - 14y2

[0064] Formula 6

[0065] Formula 7

[0066] Formula 8

[0067] We still use the traditional sum-difference division method, Formula 5, that is:

[0068] S x =(S1 - S3) / (S1 + S3)

[0069] S y =(S2 - S4) / (S2 + S4)

[0070] Then we used the two - dimensional function fitting function in the Matlab data processing toolbox to obtain the functional relationship between (S x , S y ) and the true (x, y) coordinates. In theory, at this step, we can already calculate the target position information based on the four - channel voltage values collected. However, the problem is that the function fitting function of the data processing toolbox cannot perfectly obtain a function expression with zero error. After analysis, the maximum error value at this time is about 3%, as shown in Figure 7 .

[0071] To improve the accuracy, we traverse in the neighborhood of each output value, and the maximum error can reach no more than 5‰. The specific implementation process is as follows:

[0072] According to the four - channel voltage values S1, S2, S3, S4 collected by the circuit, calculate S x and S y , substitute them into the above - mentioned two - dimensional function obtained by fitting, and obtain the calculated (x′, y′) values. However, there is a certain error between this value and the true (x, y). We substitute the (x′, y′) values into formulas 1, 2, 3, 4 within the range of plus or minus 3% of the calculated (x′, y′) values with a step size of 1‰ to obtain the calculated values S1, S2, S3, S4, that is, the calculated voltage values. Compare them with the collected voltage values. Those with an error not exceeding 5‰ are considered the best - fitting values, and the (x, y) values at this time are the final target positions. As shown in Figure 8 .

[0073] 3. Anti - high - repetition - rate interference technology

[0074] All laser - guidance systems with practical application functions must have the function of anti - high - repetition - rate interference. Currently, the common high - repetition - rate interference frequency is generally 400KHZ, and the pulse width is 1us, while the frequency of the laser signal is 20HZ. Our purpose is to separate the laser signal from the interference.

[0075] Based on the high - speed data acquisition technology, taking 20HZ as the time node, set a time window with a width of 5us. Outside the time window, all are definitely interference signals. Therefore, perform FFT transformation on the collected time - domain signal to obtain the frequency - domain characteristics of the interference signal. Then perform FFT transformation on the aliased signal within the 5us time window. Remove the frequency - domain characteristics of the interference signal in the frequency domain of the aliased signal, and what is obtained is the frequency - domain characteristics of the laser signal. Finally, perform IFFT transformation to obtain the laser signal in the time domain, and the anti - interference process ends. The specific process is as shown in Figure 9 .

[0076] The prototype structure designed in the present invention is as Figure 10 shown.

[0077] Finally, it should be noted that the above is the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should be regarded as the protection scope of the present invention.

Claims

1. A method for solving the target position of a distributed single-phase limit laser detector, characterized in that Change the target position calculation method of the traditional four - quadrant laser detection system. Rely on single - quadrant detectors distributed in four different directions to simultaneously collect target surface signals for fusion fitting to achieve target position calculation, and obtain a guidance detection signal representing the target position. The method includes the following steps: S1) Target position acquisition and calculation: Control the distributed detectors to separately collect the voltage values of the four - way spot areas, set the fitting range, adjust the step size, and perform iterative fitting calculation repeatedly to obtain the fitting coordinates (x′, y′) values of the target position after four - way fusion that meet the error threshold requirements, and output them as the target surface positioning detection signals of the distributed laser detectors; S2) Anti - high - repetition - frequency interference processing: For the target surface positioning detection signal, set the time - wave - gate width, extract the time - domain aliased signal within the time - wave - gate, and extract the time - domain interference signal outside the time - wave - gate; Filter out the interference signal in the aliased signal and retain the target position guidance signal.

2. The target position calculation method of a distributed single-phase limit laser detector according to claim 1, characterized in that, The setting of the fitting range, adjustment of the step size, and repeated iterative fitting calculation to obtain the fitting coordinates (x′, y′) values of the target position after four - way fusion that meet the error threshold requirements include: 1a) Collect the voltage values S1, S2, S3, and S4 of the four detectors respectively, and calculate the fusion calculation value (S x , S y ) of the detection position using Formula 5; 1b) Substitute into the two - dimensional fitting function Q to obtain the fitting coordinates (x′, y′) values of the target position after fusion; 1c) Within the range of plus or minus 3% of (x′, y′), take the fused fitting coordinates (x′, y′) values as (x, y) and substitute them into the spot shadow area calculation formula with a step size of 1‰ to obtain the spot shadow areas S1′, S2′, S3′, S4′ of the four - way fitting, that is, the voltage values obtained by fitting calculation; 1d) Compare S1′, S2′, S3′, S4′ with the collected voltage values S1, S2, S3, S4. If the error does not exceed 5‰, it is considered the best fitting value, and the (x′, y′) value at this time is the final fitting coordinates of the target position.

3. The target position resolution method of a distributed single-phase limit laser detector according to claim 2, characterized in that It is necessary to pre - establish the spot shadow area calculation formula, and the steps are as follows: Divide the four - quadrant according to the structure of the distributed detector and the position relationship of the laser spot. Let the center coordinates of each spot be (x, y), and the radii of the detector and the spot be R. Then the calculation formulas for the spot shadow areas S1, S2, S3, S4 detected by each path are: (Formula 1) (Formula 2) (Formula 3) (Formula 4) 4. A method for solving the target position of a distributed single-phase limit laser detector according to claim 1, characterized in that The formula 5 is to divide the sum and difference to obtain the fusion calculation value (S x , S y ) S x = (S1 - S3) / (S1 + S3) S y = (S2 - S4) / (S2 + S4) 5. A method for solving the target position of a distributed single-phase limited laser detector according to claim 1, characterized in that, The two-dimensional fitting function Q is obtained by performing two-dimensional function fitting on the fusion calculation values (S x , S y ) at the detection positions and the true coordinates (x, y) of the target positions.

6. A method for resolving the target position of a distributed single-phase limit laser detector according to claim 1, characterized in that, Filtering out the interference signal in the aliased signal and retaining the target guidance signal is: Perform Fourier transforms on the aliased signal and the interference signal respectively to obtain the spectral characteristics of the aliased signal and the interference signal, screen out the interference spectrum, and then perform inverse Fourier transform back to the time domain to obtain the interference - free target guidance signal.

7. A target position calculation device based on a distributed single-phase limit laser detector, characterized in that It includes a distributed detection unit, a processing unit, and a memory; the distributed detection unit is used to synchronously collect distributed target surface images for the processing unit. The processing unit calls the program in the memory, executes the method steps as claimed in claims 1 - 6, calculates the target position on the distributed target image, and then performs anti - high - repetition - frequency interference processing to finally obtain a guidance signal representing the target position.

8. The target position calculation device of a distributed single-phase limit laser detector according to claim 1, characterized in that The distributed detection unit is a four - way detector evenly arranged at equal distances outward from the target center in the vertical plane according to the four - quadrant principle. The detector lenses face the target and are used to separately collect laser voltage signals.

9. The target position calculation device of a distributed single-phase limit laser detector according to claim 1, characterized in that, The target position calculation device of the distributed single-phase limit laser detector further includes a main frame for distributively installing four detectors, a processing unit, and a memory.

Images