Ship rolling data error compensation method

Abstract

The present invention relates to the field of optical measurement technology, and in particular to a method for compensating for ship-sway data errors. The method interpolates and fits ship-sway information at different times and the corresponding times to obtain an interpolation polynomial. By directly photographing stars, a suitable extrapolation time step parameter is selected in combination with the interpolation polynomial as a compensation parameter for the detector to offset the ship-sway. The present invention selects a suitable extrapolation time step parameter for the interpolated and extrapolated ship-sway data by photographing stars to ensure the rationality of the parameter selection, thereby improving the measurement accuracy of the equipment and effectively isolating the equipment from the ship's swing.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical measurement, and in particular relates to a method for compensating ship rolling data errors. Background Art

[0002] Equipment that uses inertial devices to measure and obtain ship motion parameters for navigation is called a marine inertial navigation system. Photoelectric theodolites can measure and observe the angles of targets within their field of view in polar coordinates through optical imaging, while radars can measure the position of targets by transmitting and receiving electromagnetic waves. When placed on a ship, a photoelectric theodolite or radar can obtain the measured angle or position of the target below the deck. At this point, the ship's attitude and position information generated by the inertial navigation equipment (including the ship's heading, roll, pitch, and the longitude, latitude, and elevation of the equipment's location) is used to convert the below-deck measurement data to obtain the target's measured angle or position in the geodetic coordinate system.

[0003] In actual use, the ship's attitude may change. In this case, theodolites and radar equipment cannot perform the same guidance and tracking as on land. They must calculate the target's position relative to the ship based on the target's real-time position and the ship's real-time position, and then convert it into the target's position in the deck coordinate system. The target is then digitally guided into the theodolite or radar's range. The theodolite or radar can then digitally guide or automatically track the target based on its own equipment to obtain the target's measured angle and position in the deck coordinate system.

[0004] Typically, the target's position measured by the theodolite or radar in the deck coordinate system needs to be converted to its position in the geodetic coordinate system. In addition to the measurement errors of the theodolite or radar itself, inaccuracies in the ship's attitude and position data can introduce new errors during the conversion process. Therefore, the ship's attitude and position data must be corrected and compensated to reduce the errors introduced during the conversion process.

[0005] Existing methods typically compensate for ship rolling data based on theoretical calculations of delay information. However, this method has the disadvantage that after theodolite or radar equipment measures the target and obtains the measured angle and position data of the target under the deck system, when converting it to the geodetic coordinate system, the real-time measurement accuracy error increases due to the following reasons:

[0006] (1) The sampling frequency or measurement data transmission frequency of the ship rolling measurement equipment such as the strapdown inertial navigation and platform inertial navigation is insufficient, resulting in the inability of radar, theodolite and other equipment to obtain the ship rolling measurement data at the working time (for example, the theodolite operates at 1000 Hz, the inertial navigation equipment operates at 100 Hz, and the ship rolling data is sent to the theodolite at 20 Hz. Then the theodolite cannot obtain the continuously changing 1000 Hz ship rolling data and can only use the received 20 Hz low-frequency data);

[0007] (2) The transmission delay when the ship rolling measurement equipment such as strapdown inertial navigation and platform inertial navigation sends the ship rolling measurement data to the radar, theodolite and other equipment through network communication or serial port communication, resulting in the ship rolling data being no longer the latest ship rolling data when the radar, theodolite and other equipment use it (for example, the data collected by the inertial navigation at time T0 is sent to the theodolite at time T1, and the theodolite equipment that needs to use the ship rolling data at time T1 can only use the latest ship rolling data received at time T0);

[0008] (3) Due to internal reasons such as the time-consuming calculation of ship rolling data and the lag in controlling the servo motor, the instantaneous measurement data of radar, theodolite and other equipment cannot be aligned with the instantaneous ship rolling data used, resulting in measurement errors when the radar, theodolite and other equipment are working. Summary of the Invention

[0009] In view of this, the present invention aims to provide a method for compensating ship-shaking data errors. By photographing stars, a suitable extrapolation time step parameter is selected for the ship-shaking data after interpolation and extrapolation to ensure the rationality of the parameter selection, thereby completing the compensation of the detector.

[0010] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0011] A method for compensating ship rolling data errors, comprising:

[0012] S1: Use the inertial navigation system to obtain ship rolling information and ship position information, select the target star from the stars photographed by the detector, and calculate the position of the target star in the detector based on the ship rolling information;

[0013] S2: Perform interpolation fitting on the ship rolling information at different moments and the corresponding moments to obtain an interpolation polynomial between the ship rolling information and the corresponding moments; obtain the predicted ship rolling information at multiple different moments with a fixed extrapolation time step;

[0014] S3: Calculate the average ship rolling situation based on the multiple predicted ship rolling information obtained in step S2, and calculate the ship rolling elimination degree based on the position of the target star calculated in step S2;

[0015] S4: changing the extrapolation time step, and re-obtaining the predicted ship rolling information at multiple different moments according to the interpolation polynomial in step S3; repeating step S3 with the current predicted ship rolling information to obtain the ship rolling elimination degree;

[0016] S5: Compare the ship roll elimination degrees obtained in steps S3 and S4. If the ship roll elimination degree becomes smaller, repeat steps S1 to S4 until the ship roll elimination degree does not decrease with the change of the extrapolation time step. Obtain the extrapolation time step with the minimum ship roll elimination degree, and substitute this extrapolation time step into the interpolation polynomial to predict the ship roll.

[0017] Furthermore, the detector is a photoelectric theodolite or a calibration television on a radar, the inertial navigation system is installed directly below the photoelectric theodolite or the radar, and the target star is displayed on the photoelectric theodolite or the calibration television.

[0018] Furthermore, step S1 includes:

[0019] Based on the ship's position, time, and star catalog, the stars within the detector's visible range are listed, and the target stars are selected based on the detector's detection capability and magnitude.

[0020] The detector is used to take n frames of target star images of the target star, and the miss distance of the target star relative to the detector is calculated in each frame of the target star image to obtain the average miss distance of the target star in the n frames of the target star image.

[0021] Furthermore, in the process of calculating the miss distance of the target star relative to the detector in each frame of the target star image:

[0022] According to the ship's rolling information, the first coordinate position of the target star in the earth coordinate system is converted into the second coordinate position in the deck coordinate system;

[0023] The second coordinate position is converted into the third position coordinate of the target star in the target surface polar coordinate system of the detector. The distance between the third position coordinate and the center position of the target surface polar coordinate system is the miss distance.

[0024] Furthermore, the first coordinate position is converted to the second coordinate position by the following formula:

[0025] ;

[0026] Among them, (X1, Y1, Z1) represents the first coordinate position, (X2, Y2, Z2) represents the second coordinate position, H represents the heading in the ship roll information, P represents the pitch in the ship roll information, and R represents the roll in the ship roll information.

[0027] Furthermore, the second coordinate position is converted to the third coordinate position by the following formula:

[0028] ;

[0029] Wherein, (A, E) represents the third position coordinate.

[0030] Furthermore, in step S2, the extrapolated time step is the difference between the time substituted into the interpolation polynomial and the current time, and the time substituted into the interpolation polynomial is greater than the current time.

[0031] Furthermore, in step S2: the ship rolling information corresponding to n frames of target star images and the time corresponding to n frames of target star images are fitted using the least squares method or Lagrange interpolation method to obtain an interpolation polynomial; and the predicted ship rolling information at n different time moments is obtained using a fixed extrapolation time step.

[0032] Furthermore, in step S3:

[0033] The average ship rolling condition is calculated by the following formula:

[0034] ;

[0035] in, Indicates the average ship rolling situation, R i represents the roll in the predicted ship roll information at the i-th moment, P i represents the pitching in the predicted ship rolling information at the i-th moment, H i represents the heading in the predicted ship rolling information at the i-th moment, represents the average heading at n moments;

[0036] The average off-target amount was calculated by the following formula:

[0037] ;

[0038] in, represents the average off-target amount, d i represents the miss distance corresponding to the target star image in the i-th frame;

[0039] The ship rolling elimination degree is obtained by the following formula:

[0040] ;

[0041] Among them, ISO represents the ship roll elimination degree.

[0042] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0043] The present invention creates the ship-sway data error compensation method, which simulates the actual measurement situation of the measuring equipment by photographing stars. The extrapolated time step parameters obtained have a certain degree of credibility, so as to ensure the rationality of the parameter selection, reduce the measurement errors of measuring equipment such as theodolites and radars when they are on board a ship due to the low ship-sway data acquisition frequency, ship-sway data transmission delay and the servo lag of the measuring equipment itself, and improve the measurement accuracy of the equipment and the ship-sway isolation of the equipment when the ship-sway amplitude is large. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0045] Figure 1 A flow chart of a method for compensating for ship rolling data errors according to an embodiment of the present invention;

[0046] Figure 2 A schematic diagram of the ship rocking information according to an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of imaging of a star in a detector according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0049] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0050] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first", "second" and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0051] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0052] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0053] like Figure 1 As shown, the ship rolling data error compensation method described in the embodiment of the present invention includes:

[0054] S1: Use the inertial navigation system to obtain ship roll information and ship position information, select the target star from the stars photographed by the detector, and calculate the position of the target star in the detector based on the ship roll information.

[0055] Among them, the ship shaking information is as follows Figure 2 As shown, Figure 2 (a) shows the heading in the ship's rolling information. Figure 2 (b) in the figure shows the pitching in the ship rolling information. Figure 2 (c) in the figure shows the roll information within the ship's roll. The detector is a photoelectric theodolite or a calibration television on a radar. The inertial navigation system is installed directly below the photoelectric theodolite or radar, and the target star is displayed on the photoelectric theodolite or calibration television. The inertial navigation system's insufficient measurement frequency makes it difficult to ensure that the ship's roll measurement value is consistent with the current time.

[0056] In some embodiments, step S1 includes:

[0057] S11: Based on the ship's position information, time, and star catalog, stars within the detector's visible range are listed, and target stars are selected based on the detector's detection capability and magnitude. In this embodiment of the present invention, the ship's position information includes the ship's longitude, latitude, and altitude; the star catalog includes star parameters such as star sign, magnitude, mean right ascension, mean declination, proper motion, and parallax. The process of selecting target stars based on the detector's detection capability and magnitude includes selecting stars with the highest brightness possible within the detector's detection capability, based on the detector's design specifications (usually measured in magnitude).

[0058] S12: Using the detector to capture n frames of target star images, the target star's miss distance relative to the detector is calculated in each frame of the target star image, and an average miss distance of the target star in the n frames of the target star image is obtained. In this embodiment of the present invention, a servo motor is used to guide the visual axis of the photoelectric theodolite or radar calibration television toward the target star, so that the target star is imaged on the detector target surface.

[0059] In step S12, the process of calculating the miss distance of the target star relative to the detector in each frame of the target star image includes:

[0060] According to the ship's rolling information, the first coordinate position of the target star in the earth coordinate system is converted to the second coordinate position in the deck coordinate system by the following formula:

[0061] ;

[0062] Where (X1, Y1, Z1) represents the first coordinate position, (X2, Y2, Z2) represents the second coordinate position, H represents heading, P represents pitch, and R represents roll. Due to communication delays, the ship's roll data received by the theodolite or radar at the current moment is not the current measured ship's roll, but rather the ship's roll data from a previous moment, resulting in an error during this conversion step.

[0063] The second coordinate position is converted into the third position coordinate of the target star in the detector's target surface polar coordinate system by the following formula:

[0064] ;

[0065] Wherein, (A, E) represents the third position coordinate;

[0066] The distance between the third position coordinate and the center position of the target surface polar coordinate system is the miss distance.

[0067] Due to the measurement frequency, communication delay, and servo motor lag of the inertial navigation system, the target star in the field of view of the theodolite or radar calibration TV shakes periodically as the ship rolls, that is, the miss distance changes periodically as the ship rolls.

[0068] S2: Interpolate and fit the ship's rolling information at different times and their corresponding times to obtain an interpolation polynomial between the ship's rolling information and the corresponding time. The predicted ship's rolling information at multiple different times is obtained using a fixed extrapolation time step. The extrapolation time step is the difference between the time substituted into the interpolation polynomial and the current time. The time substituted into the interpolation polynomial is usually greater than the current time to compensate for data transmission delays and servo response delays.

[0069] In some embodiments, step S2 includes fitting the ship roll information corresponding to n frames of target star images and the time corresponding to the n frames of target star images using a least squares method or a Lagrange interpolation method to obtain an interpolation polynomial. The predicted ship roll information at n different time instants is obtained using a fixed extrapolation time step.

[0070] S3: Calculate the average ship roll situation based on the multiple predicted ship roll information obtained in step S2, and calculate the ship roll elimination degree in combination with the position of the target star calculated in step S2.

[0071] In some embodiments, in step S3:

[0072] The average ship rolling condition is calculated by the following formula:

[0073] ;

[0074] in, Indicates the average ship rolling situation, R i represents the roll in the predicted ship roll information at the i-th moment, P i represents the pitching in the predicted ship rolling information at the i-th moment, H i represents the heading in the predicted ship rolling information at the i-th moment, represents the average heading at n moments;

[0075] The average off-target amount was calculated by the following formula:

[0076] ;

[0077] in, represents the average off-target amount, d i represents the miss distance corresponding to the target star image in the i-th frame;

[0078] The ship rolling elimination degree is obtained by the following formula:

[0079] ;

[0080] Among them, ISO represents the ship roll elimination degree.

[0081] S4: Change the extrapolation time step, and re-obtain the predicted ship roll information at multiple different moments according to the interpolation polynomial of step S3; repeat step S3 with the current predicted ship roll information to obtain the ship roll elimination degree.

[0082] S5: Compare the ship roll elimination degrees obtained in steps S3 and S4. If the ship roll elimination degree becomes smaller, repeat steps S1 to S4 until the ship roll elimination degree does not decrease with the change of the extrapolation time step. Obtain the extrapolation time step with the minimum ship roll elimination degree, and substitute this extrapolation time step into the interpolation polynomial to predict the ship roll.

[0083] Affected by the servo control system, the response time of each device is different. Usually, the extrapolation time step parameters of different devices are also different, and need to be calibrated according to the method provided by the present invention.

[0084] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0085] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for compensating ship rolling data errors, characterized in that: include: S1: using the inertial navigation system to obtain ship rolling information and ship position information, screening target stars from the stars photographed by the detector, and calculating the position of the target star in the detector based on the ship rolling information; S2: Perform interpolation fitting on the ship rolling information at different moments and the corresponding moments to obtain an interpolation polynomial between the ship rolling information and the corresponding moments; obtain the predicted ship rolling information at multiple different moments with a fixed extrapolation time step; S3: calculating an average ship rolling condition based on the multiple predicted ship rolling information obtained in step S2, and calculating a ship rolling elimination degree based on the position of the target star calculated in step S2; S4: changing the extrapolation time step, and re-obtaining the predicted ship rolling information at multiple different moments according to the interpolation polynomial in step S3; repeating step S3 with the current predicted ship rolling information to obtain the ship rolling elimination degree; S5: Compare the ship roll elimination degrees obtained in steps S3 and S4. If the ship roll elimination degree becomes smaller, repeat steps S1 to S4 until the ship roll elimination degree does not decrease with the change of the extrapolation time step, and obtain the extrapolation time step with the minimum ship roll elimination degree. Substitute this extrapolation time step into the interpolation polynomial to predict the ship roll.

2. The ship motion data error compensation method according to claim 1, characterized in that: The detector is a photoelectric theodolite or a calibration television on a radar, the inertial navigation system is installed directly below the photoelectric theodolite or the radar, and the target star is displayed on the photoelectric theodolite or the calibration television.

3. The ship rolling data error compensation method according to claim 1, characterized in that: Step S1 includes: According to the ship position information, time and star catalog, the stars within the visible range of the detector are listed, and the target stars are selected based on the detection capability of the detector and the magnitude; The detector is used to shoot n frames of target star images of the target star, and the miss distance of the target star relative to the detector is calculated in each frame of the target star image to obtain an average miss distance of the target star in the n frames of the target star image.

4. The ship rolling data error compensation method according to claim 3, characterized in that: In the process of calculating the miss distance of the target star relative to the detector in each frame of the target star image: converting a first coordinate position of the target star in the earth coordinate system into a second coordinate position in the deck coordinate system according to the ship rolling information; The second coordinate position is converted into a third position coordinate of the target star in the target surface polar coordinate system of the detector, and the distance between the third position coordinate and the center position of the target surface polar coordinate system is the miss distance.

5. The ship motion data error compensation method according to claim 4, characterized in that: The first coordinate position is converted to the second coordinate position by the following formula: ； Among them, (X1, Y1, Z1) represents the first coordinate position, (X2, Y2, Z2) represents the second coordinate position, H represents the heading in the ship roll information, P represents the pitch in the ship roll information, and R represents the roll in the ship roll information.

6. The ship motion data error compensation method according to claim 5, characterized in that: The second coordinate position is converted to the third position coordinate by the following formula: ； Wherein, (A, E) represents the third position coordinate.

7. The ship motion data error compensation method according to claim 5, characterized in that: The extrapolated time step in step S2 is the difference between the time substituted into the interpolation polynomial and the current time, and the time substituted into the interpolation polynomial is greater than the current time.

8. The ship motion data error compensation method according to claim 5, characterized in that: In step S2: the ship rolling information corresponding to n frames of target star images and the moments corresponding to n frames of target star images are fitted using the least squares method or the Lagrange interpolation method to obtain the interpolation polynomial; and the predicted ship rolling information at n different moments is obtained using a fixed extrapolation time step.

9. The ship motion data error compensation method according to claim 8, characterized in that: In step S3: The average ship rolling condition is calculated by the following formula: ； in, Indicates the average ship rolling condition, R i represents the roll in the predicted ship roll information at the i-th moment, P i represents the pitching in the predicted ship rolling information at the i-th moment, H i represents the heading in the predicted ship rolling information at the i-th moment, represents the average heading at n moments; The average off-target amount was calculated by the following formula: ； in, represents the average off-target amount, d i represents the miss distance corresponding to the target star image in the i-th frame; The ship rolling elimination degree is obtained by the following formula: ； Here, ISO represents the ship rolling elimination degree.

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