CN103727961A - Method for correcting dynamic error of electro-optic theodolite - Google Patents

Abstract

The invention discloses a method for correcting the dynamic error of an electro-optic theodolite, relating to the field of photoelectricity measurement and control and solving the problem in a dynamic measurement process of an existing electro-optic theodolite that the system has time delay error for an encoder sampling center and an infrared camera exposure center are out of sync. The method comprises steps of calibrating a detection rack; taking the average value of three obtained change face data as a truth value; delaying parameter design; setting external triggering synchronizing signal delayed TD of a camera, selecting the value of an encoder so as to align the exposure time center with a miss distance and a sampling time of the encoder; measuring the angle at dynamic state and accurately calculating and setting external triggering synchronizing delayed TD of the camera, then setting the servo control parameter and amplitude of oscillation of an infrared theodolite, and collecting the date of sinusoidal motion of the full field by the infrared theodolite; obtaining information about azimuth angle and angle of pitch; and respectively carrying out subtracting on the azimuth angle and the angle of pitch with the truth value obtained in step one, and taking the square root value so as to obtain the angle measurement accuracy to realize error correction.

Description

Dynamic Error Correction Method of Photoelectric Theodolite

technical field

The invention belongs to the field of photoelectric measurement and control, and in particular relates to a dynamic error correction method of a photoelectric theodolite, which can be used to improve the angle measurement accuracy of the photoelectric theodolite in the precision detection of the photoelectric theodolite. At the same time, in the field test experiment, it can be used to improve the target's outer ballistic trajectory coordinates.

Background technique

During the launch test of missiles and spacecraft, most of the data reflecting the test situation, such as the flight trajectory of the rocket and the orbit of the satellite, are obtained through measurement by radio and optical external measurement equipment. The measurement accuracy of these external measurement equipment marks the The measurement and control level of spacecraft tests such as missiles and satellites. Accuracy is the life and destination of external testing equipment. Since measurement data and accuracy analysis are closely related to the development, finalization and improvement of missiles, satellites and other spacecraft, all relevant domestic units attach great importance to the accuracy appraisal of external testing equipment. The photoelectric theodolite is the main equipment for photoelectric measurement in the shooting range. The photoelectric measurement equipment mainly completes the spatial positioning of the measured target through angle measurement and intersection processing, and further calculates the target's external ballistic parameter data. The size of the angle measurement error directly affects the positioning accuracy, so the research on the source, influence and detection method of the angle measurement error is one of the important research contents of the photoelectric theodolite.

The accuracy calibration of photoelectric theodolite is divided into two parts: static angle measurement accuracy and dynamic angle measurement accuracy. The dynamic measurement angle measurement accuracy is obtained on the basis of static angle measurement accuracy. In this paper, the reasons affecting the dynamic measurement error of the photoelectric theodolite are analyzed, and an error correction method based on time alignment is proposed. After dynamic angle measurement correction, the root mean square value of the angle measurement error of the azimuth angle and the elevation angle is improved from 27.89" and 17.67" respectively. To 10.07" and 8.56", this method effectively improves the dynamic measurement accuracy, and has reference value for other photoelectric measurement equipment.

Contents of the invention

The purpose of the present invention is to solve the system delay error caused by the asynchrony between the encoder sampling center and the infrared camera exposure center during the dynamic measurement process of the photoelectric theodolite, and proposes a method for setting the external trigger signal of the infrared camera by analyzing experimental parameters The method of delay time solves the problem of exposure synchronization.

The photoelectric theodolite dynamic error correction method of the present invention, this method comprises the following steps:

Step 1. Calibrate the detection frame; use a high-precision Leica theodolite to measure the angle values of the three collimators. The angle values of the collimators are to calibrate the positive and negative mirror data of the three collimators. The average value of the positive and negative mirror data is used as the true value;

Step 2. Delay parameter design; set the camera’s external trigger synchronization signal delay TD, select the encoder value, according to the formula: T/2+T _delay = 1.25ms×i, T is time, and the value of i is 0 ~7, realize the alignment of exposure time, off-target amount, and encoder sampling time;

Step 3. Calculation of dynamic angle measurement accuracy; delay TD according to the external trigger synchronization signal of the infrared camera set in step 2, then set the servo control parameters and swing amplitude of the infrared theodolite, and use the infrared theodolite to measure the data during the sinusoidal motion of the full field of view Collecting; Obtaining azimuth and elevation information;

Step 4. The azimuth angle and pitch angle information obtained in step 3 are respectively compared with the true value obtained in step 1, and the value of the square root is taken to obtain the angle measurement accuracy and realize the correction of the error.

Beneficial effects of the present invention: the present invention proposes a method of using dynamic delay setting correction to align the three elements of the exposure time, the amount of miss, and the encoder to the same time. The calculation formula of delay correction time under different system parameters is given. Use this formula to calculate appropriate camera delay settings for different integration times, and encoder data selection methods. In the field of infrared photoelectric measurement and control of a large field of view, the method of the invention is beneficial to improving the dynamic angle measurement accuracy of a large field of view infrared photoelectric theodolite. Using the system internal delay correction method, the dynamic measurement accuracy of the photoelectric theodolite is corrected. After the dynamic angle measurement correction, the root mean square value of the angle measurement error of the azimuth angle and the elevation angle is increased from 27.89" and 17.67" to 10.07" and 8.56 respectively. ", this method effectively improves the dynamic measurement accuracy, and has reference value for other photoelectric measurement equipment.

Description of drawings

Fig. 1 is the detection environment composition schematic diagram of photoelectric theodolite dynamic error correction method of the present invention;

Fig. 2 is the schematic diagram of the photoelectric theodolite timing relationship after delay correction in the photoelectric theodolite dynamic error correction method of the present invention;

Fig. 3 is the schematic diagram of the timing relationship of the photoelectric theodolite without time-delay correction;

Fig. 4 is the field comparison experiment processing result of photoelectric theodolite dynamic error correction method of the present invention;

Detailed ways

1. Calibrate the detection frame; if the calibration of the detection frame is completed in the indoor calibration and calibration workshop, the theodolite needs to be placed on the detection platform to work. The calibration system includes a stable platform, infrared photoelectric theodolite, large-diameter collimator, detection frame, 0.5 "Leica theodolite and other systems. After adjusting and stabilizing the detection platform, use a 0.5" Leica theodolite to check the 1# light pipe with an azimuth angle of 0° and the elevation angle of 0°, the 5# light pipe with an azimuth angle of 90° and an elevation angle of 0°, and The 6# light pipe with an azimuth angle of 90° and an elevation angle of 65° is used for calibration; the calibration data includes three times of forward and reverse mirror data, and then the average value of the three times of data is taken as the true value. At the same time, the positive and negative mirror data of the three light pipes calibrated by the 0.5" Leica theodolite are used to calculate the system error, that is, the zero position difference, the collimation difference, and the horizontal axis difference. The system error is used for true value correction.

2. Calculation of delay correction parameters; the timing principle of the photoelectric theodolite is to align the three elements of the exposure time, the amount of miss, and the encoder to the same time. To analyze the cause of the problem, when the theodolite moves at a certain speed and acceleration, when the exposure time of the infrared camera is 1ms, we need to align the exposure center of the infrared camera with the center of one of the 8 sets of encoders, so theoretically we need Delay the encoder's external trigger synchronization backward by 500μs, but due to the limitations of data transmission, sampling time, and servo control during the system design process, the encoder's external trigger synchronization signal cannot be modified, and the camera's external trigger can be modified signal, so it is necessary to delay the camera's external trigger synchronization signal by 750μs, and select the first group of encoder values. After the delay is set, the working sequence relationship is shown in Figure 4. The formula for timing alignment is as follows. When the integration time of the infrared camera is T (T is generally whole milliseconds), the encoder to be selected is the i[0:7] group, and the delay time is set to Tdelay, then the three need to satisfy the formula (1).

T/2+T _delay = 1.25ms×i (1)

3. Collect measurement data; after setting the time delay, the theodolite performs a sinusoidal movement with the working parameters of the speed 20°/s and the swing amplitude of 5° centering on the beacon light, and then calculates the measurement of the theodolite when it moves upward and downward. Obtained azimuth and elevation angle information. The measurement results are shown in Table 1 and Table 2. Table 1 shows the encoder and off-target information of each frame image when the theodolite moves upward after delay correction, and the encoder and off-target information of each frame image when the theodolite moves downward after delay correction. quantity information;

Table 1

Table 2

4. The accuracy calculation results after correction; when measuring the dynamic accuracy, the servo control parameters of the theodolite are set to 20°/s for speed and 5° for swing. When the infrared camera works with an integration time of 1ms, the time division system takes the second synchronization signal as a reference, and generates a 100Hz synchronous external trigger signal for the infrared camera as a time reference by frequency division. At the same time, an 800Hz synchronous trigger signal is generated to the encoder as the working time reference of the encoder system. When the theodolite shoots the beacon light in a sinusoidal motion, it will image the beacon light when it moves downward and upward. When the above times are not adjusted, the time contained in the image generated when moving upward and downward , encoder, off-target amount, and synthetic angle information. The root-mean-square and average values of the measured azimuth and elevation static measurement errors are as follows:

δ _ΔA = 10.07″ $\stackrel{\‾}{\mathrm{\ΔA}}={41967.82}^{\′\′}$

δ _ΔE = 8.56″ $\stackrel{\‾}{\mathrm{\ΔE}}={-260.21}^{\′\′}$

Through the measurement data, we can see that the system error can be eliminated after the central moment of the time-delay corrected data exposure synchronization is aligned with the encoder angle, thereby improving the dynamic measurement accuracy of the photoelectric theodolite.

5. The measurement results without delay correction; at the same time, the calculation results of the measurement data without delay correction are given, so that the delay correction effect can be reflected. Without delay correction, the servo control parameters of the theodolite are set to 20°/s for speed and 5° for swing. When the infrared camera works with an integration time of 1ms, the time division system takes the second synchronization signal as a reference, and generates a 100Hz synchronous external trigger signal for the infrared camera as a time reference by frequency division. At the same time, an 800Hz synchronous trigger signal is generated to the encoder as the working time reference of the encoder system. When the theodolite shoots the beacon light in a sinusoidal motion, it will image the beacon light when it moves downward and upward. When the above times are not adjusted, the time contained in the image generated when moving upward and downward , encoder, miss amount, and composite angle information are shown in Table 3 and Table 4. Table 3 is the encoder and miss amount information corresponding to each frame image when the theodolite moves upward, and Table 4 is the code corresponding to each frame image when the theodolite moves downward. Device and off-target information.

table 3

Table 4

When the theodolite is moving forward, the encoder value adopts the 0th encoder as shown in Figure 1. The root-mean-square and average values of the measured azimuth and elevation static measurement errors are as follows:

δ _ΔA = 15.63″ $\stackrel{\‾}{\mathrm{\ΔE}}={-41995.73}^{\′\′}$

δ _ΔE = 15.45″ $\stackrel{\‾}{\mathrm{\ΔE}}={-253.61}^{\′\′}$

When the theodolite is moving forward, the encoder value also adopts the 0th encoder in the accompanying drawing 3. The root-mean-square and average values of the measured azimuth and elevation static measurement errors are as follows:

δ _ΔA = 9.99″ $\stackrel{\‾}{\mathrm{\ΔA}}={41943.73}^{\′\′}$

δ _ΔE = 11.94″ $\stackrel{\‾}{\mathrm{\ΔE}}={-271.88}^{\′\′}$

If the above data are integrated into a set of data calculation, the root mean square value and average value of the static measurement error of the measured azimuth angle and elevation angle are as follows:

δ _ΔA = 27.89″ $\stackrel{\‾}{\mathrm{\ΔA}}={41971.09}^{\′\′}$

δ _ΔE = 17.67″ $\stackrel{\‾}{\mathrm{\ΔE}}={-264.63}^{\′\′}$

From the root mean square value of the static measurement error of the overall azimuth angle and pitch angle and the root mean square value of the forward motion and reverse motion, it can be seen that the equipment has a large systematic error, while the random error of the equipment is very small. According to With the knowledge of error theory, we can analyze, test and eliminate the systematic error of the equipment.

Through the measurement data, we can see that the system error can be eliminated after the central moment of the time-delay corrected data exposure synchronization is aligned with the encoder angle, thereby improving the dynamic measurement accuracy of the photoelectric theodolite.

In this embodiment, data comparison experiments with high-precision calibrated equipment are used in the field. During the experiment, the photoelectric theodolite infrared ballistic camera measurement system and high-precision equipment simultaneously measure the target ballistic trajectory, and the measurement sub-station uses the corrected dynamic measurement Method, the integration time of the infrared camera is 1ms, the delay of the infrared camera is 750μs, and the first set of encoder values is selected. The target azimuth angle and target pitch angle obtained by the measurement substation are corrected by the dynamic error, and then intersected, and the intersection calculation result is compared with the high-precision calibrated equipment. Calculate the angle measurement errors of the two sets of measuring equipment in the geodetic coordinate system in X direction, Y direction and Z direction respectively. The results of the field comparison are shown in Figure 4. It can be seen from Figure 4 that the average angle measurement errors in the X direction, Y direction, and Z direction in the geodetic coordinate system are 11.32", 10.05", and 2.71", respectively.

Claims (2)

1. The photoelectric theodolite dynamic error correction method is characterized in that the method may further comprise the steps: Step 1. Calibrate the detection frame; use a high-precision Leica theodolite to measure the angle values of the three collimators. The angle values of the collimators are to calibrate the positive and negative mirror data of the three collimators. The average value of the positive and negative mirror data is used as the true value; Step 2. Delay parameter design; set the camera’s external trigger synchronization signal delay TD, select the encoder value, according to the formula: T/2+T _delay = 1.25ms×i, T is time, and the value of i is 0 ~7, realize the alignment of exposure time, off-target amount, and encoder sampling time; Step 3. Calculation of dynamic angle measurement accuracy; delay TD according to the external trigger synchronization signal of the infrared camera set in step 2, then set the servo control parameters and swing amplitude of the infrared theodolite, and use the infrared theodolite to measure the data during the sinusoidal motion of the full field of view Collecting; Obtaining azimuth and elevation information; Step 4. The azimuth angle and pitch angle information obtained in step 3 are respectively compared with the true value obtained in step 1, and the value of the square root is taken to obtain the angle measurement accuracy and realize the correction of the error. 2. photoelectric theodolite dynamic error correction method according to claim 1, is characterized in that, adopting Lycra theodolite described in step one is the collimator of 0 ° and pitch angle 0 ° to azimuth angle, azimuth angle is 90 ° and A collimator with an elevation angle of 0° and a collimator with an azimuth angle of 90° and an elevation angle of 65° are used for calibration.

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