A dynamic calibration method for local datum of a ship

Abstract

The present invention relates to a method for dynamic calibration of a local datum of a ship, comprising the following steps: selecting measurement points in a local area of ​​the ship to determine the spatial coordinates of the measurement points; fitting a plane coordinate system and spatial coordinates of a target measurement area of ​​the ship to generate a longitudinal horizontal line, a ship centerline, and a transverse horizontal line; adopting a straightness error evaluation method based on a minimum area method of transformed coordinates to calculate a straightness error t of minimum condition evaluation; querying the maximum value of a hull centerline and a horizontal assembly deviation according to the construction length of the hull as a deviation calculation value; determining a marking deviation and calculating a total error; extending the local deviation of the point measurement to the overall deviation of the entire measurement area to perform an extension conversion of the length and angle; making a local datum installation plane and an equipment installation base for equipment to be calibrated; and fixing the equipment installation base.

Description

Technical Field

[0001] The invention relates to a method for dynamic calibration of a local benchmark of a ship. Background Art

[0002] Total stations and photoelectric theodolites are multifunctional measuring instruments that are widely used in the construction industry and integrate measurement and surveying (layout) functions. The coordinate surveying function refers to the function of quickly and accurately laying out a point on the ground based on the coordinates of a point. This function can improve the accuracy and speed of measurement and layout.

[0003] In ship measurement, the ship should first be moved to the dock to establish stable, rigid and static conditions, select an appropriate location to set up the total station and photoelectric theodolite, and then coordinate measurement to determine the level and orientation of the ship. The steps of coordinate measurement are mainly to set up the survey station, backsight orientation, input the coordinates of unknown ground surface points and the height of the reflective prism at the set-out point, and instrument measurement or calculation.

[0004] After the ship platform is completed and leaves the dock, for subsequent installation or maintenance projects with high construction precision requirements, such as radar and inertial navigation, the ship is often returned to the dock, and the hull is kept in a static and stable state through the dock piers. Optical calibration equipment such as total stations and theodolites are set up in the dock, and multiple calibration points are established on the hull. By aiming at the calibration points, the horizontal and azimuth reference lines of the ship are mapped. However, due to the basic principles of total stations and theodolites, they need to be set up and the levelness adjusted under static conditions through gyroscopes or levels. Therefore, this method cannot be used for calibration when the ship is floating. Since the project of docking and installing dock piers is large, costly, and long, this method cannot be used for urgent, local, cost-sensitive, and high-precision installation and construction projects.

[0005] In addition, local benchmark progress calibration can be carried out by transplanting existing reference points on the ship. The main thing is to transplant the existing reference benchmark to the target area. If there are obstacles during the transplantation process, the benchmark platform is first transferred to the transfer station by mid-way transfer. After the equipment is transferred, the coordinates of the transfer station are collected again to realize the coordinate system conversion and the generation of the new benchmark platform. However, due to the long distance between the reference point and the target installation position of the equipment, or multiple compartments, multiple coordinate system conversions are designed, resulting in multiple accumulations of transfer errors that cannot be eliminated. Summary of the invention

[0006] The present invention aims to provide a method for dynamic calibration of local datum of a ship, which is used to measure and calculate the centerline and horizontal datum of the ship when the ship is floating, and meets high-precision requirements, so as to facilitate the installation of the base and calibration of the equipment after the ship is undocking. The technical solution is as follows:

[0007] A method for dynamic calibration of a local reference of a ship comprises the following steps:

[0008] (11) Select measurement points in the local area of ​​the ship and determine the spatial coordinates p (x, y, z) of the measurement points; fit the plane coordinate system and spatial coordinates of the target measurement area of ​​the ship to generate the longitudinal horizontal line, the centerline of the ship, and the transverse horizontal line;

[0009] (12) Using the straightness error evaluation method based on the minimum area method of transformed coordinates, calculate the straightness error t of the minimum condition evaluation;

[0010] (13) According to the construction length of the hull, the maximum value of the hull centerline and horizontal assembly deviation is queried and used as the deviation calculation value;

[0011] (14) The maximum value of the queried hull centerline assembly deviation is defined as the in-dock assembly centerline entity deviation Δ zb ; Take 1 / 2 of the deck thickness in the hull measurement area as the sampling point deviation of the non-structural surface of the hull centerline Δ zf , the calculated cumulative deviation of the ship's centerline Δ z Δ is the entity deviation of the centerline of the assembly in the dock zb Deviation from sampling point on non-structured surface Δ zf The difference, Δ z =Δ zb -Δ zf ;

[0012] (15) The maximum value of the queried horizontal assembly deviation of the hull is defined as the horizontal entity deviation of the assembly in the dock; the sampling point deviation of the horizontal non-structural surface of the hull is taken as 0, and the cumulative deviation value of the horizontal hull Δ is calculated. s is the horizontal entity deviation of the assembly in the dock, that is, Δ s =Δ sb ;

[0013] (16) Determine the marking deviation u and calculate the total error Δ = t + Δ z +Δ s +u;

[0014] (17) Extend the local deviation of point measurement to the overall deviation of the entire measurement area, and perform extension conversion of length and angle;

[0015] (18) Make a local reference installation plane for installing the equipment to be calibrated: Use the already fitted spatial coordinate system to map it to the local reference installation plane, set several measurement points in the local installation reference plane, and calibrate it to determine the horizontality of the local reference installation plane, and polish it to meet the horizontal flatness; use a laser tracker to determine the center line of the local reference plane and mark the center line;

[0016] (19) Make the equipment installation base for the equipment to be calibrated;

[0017] (20) The equipment to be calibrated and the equipment mounting base are connected to the local reference mounting plane, the centerline mark of the local reference plane is aligned with the boss surface of the equipment mounting base, and the boss surface is corrected again using the laser tracker reflector. The equipment mounting base is adjusted so that the boss surface is aligned with the centerline of the local reference plane, and the equipment mounting base is fixed.

[0018] Furthermore, in step (1), measurement points are selected in a local area of ​​the ship, and the method for determining the spatial coordinates of the measurement points is as follows: based on the original center longitudinal girder structure and the strong transverse beam structure position of the hull, corresponding marks are made on the deck surface, a laser tracker device is set up at a position where all measurement points can be observed, a reflector is set at the measurement point, and the coordinate data of the measurement point is scanned and recorded using the laser tracker device; and the spatial coordinates p (x, y, z) of the measurement point are determined.

[0019] Furthermore, based on the principle of spatial polar coordinate measurement, a spatial coordinate system is constructed based on the horizontal rotation axis and vertical rotation axis of the laser tracking head and their intersection. The spatial coordinates p (x, y, z) of the measuring point are obtained by measuring the pitch angle (EL) and horizontal azimuth angle (AZ) parameters of the laser head deflection and the radial distance parameter r from the center of the laser head to the measuring point p.

[0020] The method of using a laser tracker to scan and record the coordinate data of the measuring point to obtain the spatial coordinate p (x, y, z) of the measuring point is as follows: based on the principle of spatial polar coordinate measurement, a spatial coordinate system is constructed based on the horizontal rotation axis and the vertical rotation axis of the laser tracking head and their intersection. The laser head emits and receives the laser returned by the reflector. The pitch angle (EL) and the horizontal azimuth angle (AZ) of the laser head deflection and the radius distance parameter r from the center of the laser head to the measured point p are measured to obtain the spatial coordinate p (x, y, z) of the measuring point.

[0021] Furthermore, the method of step (2) is:

[0022] Suppose there are n measuring points p i (x i ,y i , z i ), i = l, 2, ..., n, the ideal straight line for evaluating the straightness error according to the minimum condition is l, a, b and translation c are selected, l is rotated around the x-axis by an angle a to become a straight line l1 parallel to the plane zox, and around the y-axis by an angle b to become a straight line l2 parallel to the yoz axis, l2 is then subjected to coordinate translation c, where the translations along the x, y, and z axes are Δ x , Δ y, 0, after shifting, it is a straight line lˊ, then lˊ is made to coincide with the z-axis, where a is the angle between the straight line l and the plane xoz, b is the angle between the straight line l1 and the z-axis, (-Δ x , -Δ y , 0) is the coordinate of the intersection of the straight line l2 and the xoy plane;

[0023] The coordinates of each measuring point and the ideal straight line l are transformed together. After the transformation, l is transformed into a straight line lˊ parallel to the z-axis. i (x i ,y i , z i ), i = 1, 2, ..., n, the coordinate transformation is p i ˊ(x i ˊ,y i ˊ, z i ˊ)(i=1,2,……,n), let the distance from each measuring point to the ideal straight line be d i ,

[0024]

[0025] d max is d i The maximum value, d max is a function of (a, b, c), find the function d max Minimum value, denoted as min d max , then mind max Twice the straightness error is the minimum condition evaluation:

[0026] t=2×min d max (a,b,c).

[0027] Furthermore, the calculation method of the deviation angle θ of the angle extension in step (9) is as follows: assuming that the overall length of the ship is L, the longitudinal deviation value a1 of the local length L1 area of ​​the ship is obtained by point measurement, and then the deviation angle θ of the L1 area is calculated. a , and then calculate the theoretical deviation angle of the entire measurement area

[0028] Furthermore, step (9) manufactures the equipment installation base of the equipment to be calibrated according to the following characteristics: first, the center line of the equipment installation base is marked, and the parallelism between the equipment to be calibrated and the center line is not less than 0.2 mm; second, the installation surface is polished, and the flatness is within 1 mm. 2 The range does not exceed 0.3mm; third, two bosses are set on one side of the equipment installation base, and the flatness of the surface is within 1m 2 The range does not exceed 0.1mm, and the parallelism between the outer surface of the boss and the center line of the base is not less than 0.2mm; fourth, a fine-tuned waist-shaped hole is set for adjustment.

[0029] The essential features of the present invention are: utilizing the characteristic that the ship hull will refer to the relevant construction standards when it is built, reverse fitting the spatial coordinate system of the local area of ​​the ship, and measuring the relative coordinates of the relevant points through the laser tracker to obtain the centerline deviation and horizontality deviation of the local area of ​​the ship under dynamic conditions; establishing a systematic error analysis method, analyzing the measurement error of the laser measuring instrument, the construction process error and the construction random error item by item, and using the minimum error calculation method and the maximum error standard selection principle for cumulative calculation, to obtain the best and most reliable measurement results. Compared with the existing technology, the advantages of the present invention are:

[0030] 1. The reverse test method is applicable to most surface ship platforms. It does not require technical parameters and construction drawings during forward design. It is widely applicable to platforms that meet national military standards or related standards.

[0031] 2. The calibration method using relative coordinate system does not rely on static calibration conditions, which can greatly reduce the time and economic costs brought by ship docking and static calibration.

[0032] 3. The use of high-precision measurement methods and perfect measurement methods and error analysis methods can achieve a high level of accuracy under floating platform conditions, which can meet the high-precision calibration requirements of ship equipment such as radar and inertial navigation.

[0033] 4. By taking advantage of the dynamic measurement of the laser tracker, after the establishment of the local reference coordinate system of the ship, the equipment calibration can be repeated many times without moving the points, and it will not affect tasks such as ship navigation. It has obvious advantages in complex and long-term construction projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Selection of measurement points in the floating platform coordinate system;

[0035] Figure 2 The spatial coordinate system of the measured point;

[0036] Figure 3 Coordinate transformation diagram;

[0037] Figure 4 Deviations in assembly of sections and blocks of surface ships;

[0038] Figure 5 Measurement area distance conversion;

[0039] Figure 6 Length angle conversion;

[0040] Figure 7 Boss outline drawing. DETAILED DESCRIPTION

[0041] The present invention is described below in conjunction with the accompanying drawings and embodiments.

[0042] The ship local reference dynamic calibration method of the present invention is specifically as follows:

[0043] (1) Based on the centerline and horizontal assembly deviation of the segment or block used as reference during ship construction, a high-precision laser measuring instrument with floating measurement function is used to select points in the target measurement area of ​​the ship, set up a laser tracker, and establish a coordinate system at the measurement point using a reflection ball to fit the plane coordinate system or space coordinates of the target measurement area of ​​the ship.

[0044] Through error analysis of segmented assembly error, inherent error analysis of laser measurement, and construction error, the maximum error of the entire measurement method is calculated.

[0045] Make a reference platform and equipment installation base, and perform total weight installation calibration through horizontal adjustment and azimuth installation surface.

[0046] (2) Based on the basic method of floating platform measurement in step (1), select the ship reference source. Use the stern hull structure to determine the centerline and horizontal reference. Use the laser tracker to scan the stern deck structure of the ship to determine the ship's shape, form the internal coordinate system reference of the acquisition equipment, and project it to the target area.

[0047] like Figure 1 As shown in the figure, in the local area of ​​the ship, taking the deck as an example, by finding the original longitudinal girder structure and strong transverse beam structure, several marked points are made on the deck surface, and the laser tracker equipment is set up at a position where all points can be observed, and the coordinate data is scanned and recorded. The longitudinal horizontal line (also the centerline of the ship) and the transverse horizontal line are generated by fitting. When collecting data, attention should be paid to the influence of different deck plate thickness on the data.

[0048] (3) The laser tracker uses the principle of spatial polar coordinate measurement to determine the spherical coordinates of the center point of the reflector by measuring the pitch angle (EL), the horizontal azimuth angle (AZ) and a radius distance. The coordinate system consists of the horizontal rotation axis and the vertical rotation axis of the laser tracking head and their intersection. The laser head emits and receives the laser returned by the reflector. By measuring the two angle parameters of the laser head deflection and a distance parameter r from the center of the laser head to the measured point p, the spatial coordinates p (x, y, z) of the measured point are obtained by the formula, as follows: Figure 2 shown.

[0049] px=r sin(b)cos(a)

[0050] py=r sin(b)sin(a)

[0051] pz=r cos(b)

[0052] (4) Based on step (3) (2), the principle of laser tracker and the method of measuring and placing selected points are adopted, and the straightness error evaluation method based on the minimum area method of transformed coordinates is adopted to obtain the minimum error that meets the conditions.

[0053] Suppose there are n measuring points pi (xi, yi, zi) (i = l, 2, ..., n), the ideal straight line for evaluating the error under the minimum condition is l, and a, b and translation c are appropriately selected so that l is rotated around the axis by an angle a to become a straight line l1 parallel to the plane zox, and rotated around the axis by an angle b to become a straight line l2 parallel to the yoz axis. l2 is then subjected to coordinate translation c, where the translations along the x, y, and z axes are Δ x , Δ y , 0, after shifting, it is a straight line lˊ, then lˊ can be made to coincide with the z-axis. Figure 3 (a), (b), and (c), where a is the angle between the straight line l and the plane xoz, b is the angle between the straight line l1 and the z-axis, (-Δ x , -Δ y , 0) are the coordinates of the intersection of straight line l2 and xoy plane.

[0054] Since the coordinate transformation of each measuring point and the ideal straight line will not affect the relationship between the points, the coordinate transformation of each measuring point and the ideal straight line l is carried out together. After the transformation, l is transformed into a straight line lˊ parallel to the z-axis, and the coordinate transformation of each measuring point pi(xi, yi, zi) (i = 1, 2, ..., n) is p i ˊ(x i ˊ,y i ˊ, z i ˊ)(i=1,2,……,n), the distance from each point to the ideal straight line is d i ,but

[0055]

[0056] d max is d i The maximum value, d max is a function about (a, b, c), find the minimum value of the function, denoted as mind max , then mind max The straightness error is twice the value of the minimum condition evaluation straightness error:

[0057] t=2×min d max (a,b,c).

[0058] The specific implementation plan is as follows:

[0059] Suppose the rotation matrix of the rotation angle of ? along the x-axis is [a], the rotation matrix of the rotation angle of ? along the y-axis is [b], and the translation matrix of the translation of c is [c]. According to the mathematical method, we have:

[0060]

[0061] Then the measuring point p i ˊ and p i The coordinate transformation relationship between them is:

[0062]

[0063] From this we can calculate:

[0064]

[0065]

[0066] but:

[0067]

[0068]

[0069] Straightness error:

[0070]

[0071] (5) Based on the selection and calculation of the mark positions in steps (2) and (3), the system error generated by the calibration method is calculated according to the shipbuilding implementation of the national military standard "GJB3182-98 Surface Ship Hull Construction Accuracy Requirements". In the process of shipbuilding, there are specific data requirements for segmented production and assembly positioning in the dock. Figure 4 .

[0072] 1) The calculation process of the centerline deviation is as follows: the standard deviation in the dock is looked up and the maximum value is taken, which is defined as the entity deviation. During the construction of the hull, the centerline is limited by the process implementation, and the deck thickness will affect the precision inverse estimation. It is necessary to consider the non-structural surface sampling point deviation, that is, the value deviation caused by the deck thickness at the measurement point. Taking the deck thickness of 10mm as an example, 1 / 2 of the deck thickness can be taken as the maximum deviation of 5mm. Therefore, the cumulative deviation value of the centerline Δ z is the deviation in the dock Δ zb Deviation from sampling point on non-structured surface Δ zf difference.

[0073] Δ z =Δ zb -Δ zf ;

[0074] 2) The calculation process of ship horizontal deviation is: take the maximum value of the entity deviation in the horizontal table, which is defined as the entity deviation; because the horizontal measurement point does not involve the conformity of the sampling point and the structure, it is considered that the average thickness of the ship deck is basically uniform, and the thickness deviation is not greater than 1mm. Therefore, the sampling point deviation value is defined as 0mm. Ship horizontal cumulative deviation value Δ s is the entity deviation Δ zb .

[0075] Δ s =Δ sb ;

[0076] 3) If the datum can be generated without station transfer, the measurement solution calculation does not require secondary conversion of the coordinate system. L The distance accuracy is: 15um+6um / m; the distance accuracy is: 0.5um / m. It can be ignored.

[0077] If station transfer is required, the scanning deviation will be 0.5mm. If additional station transfer is required, the accuracy of station transfer is related to the measuring distance, angle and size of station transfer platform. If the station transfer platform is within the ship width, the deviation angle can be ignored.

[0078] 4) The construction workers’ marking accuracy standard is 1mm, which can generally reach 0.25-0.5mm, and the deviation is calculated as 0.5mm for a 0.5m marking.

[0079] The total error is:

[0080] Δ=Δ z +Δ s +0.5;

[0081] like Figure 5 As shown in the figure, the local deviation of point measurement needs to be extended to the overall deviation of the entire measurement area, and the extension conversion of length and angle is required. The deviation angle θ can be obtained by collecting and calculating the longitudinal deviation value of the L1 area of ​​the overall length of the ship to obtain the a1 value; the deviation angle θa of the L1 area is calculated through the trigonometric function relationship.

[0082] Calculate the theoretical deviation angle of the entire measurement area:

[0083]

[0084] The length and angle are calculated as follows: within a one-meter radius, 1′≈0.29 mm. Figure 6 As shown:

[0085] When the angle is very small, the relationship between the angle and the deviation value can be directly calculated using the circumference.

[0086] (6) Based on the results of establishing the local platform coordinate system of the ship in steps (2), (3), (4), and (5), a local reference plane is made for installing the equipment to be calibrated. The already fitted spatial coordinate system is used to map to the local reference installation plane. Several measurement points are set in the local reference plane and calibrated to determine the horizontality of the local reference plane. The plane is then polished to meet the horizontal flatness requirements. The calibration method is the same as step (2). The centerline of the local reference plane is determined using a laser tracker. The calibration method is the same as step (2) and the centerline is marked.

[0087] (7) Based on the preparation of the local reference installation plane in step (6), calibrate the centerline and horizontal reference of the equipment installation base. The equipment installation base should meet the following characteristics: First, the centerline of the equipment installation base should be marked, and the parallelism of each installation equipment with the centerline should not be less than 0.2mm; second, the installation plane should be polished, and the flatness should not exceed 0.3mm (1m 2 Maximum processing accuracy); Third, there are two bosses on one side of the mounting base, and the flatness of the surface meets 0.1mm (1m 2 Maximum machining accuracy), the parallelism between the outer surface of the boss and the center line of the base is not less than 0.2mm; fourth, it has a waist-shaped hole that can be used for installation fine-tuning, see Figure 7 .

[0088] (8) Based on steps (7) and (6), the local reference installation plane and the equipment installation base are prepared, and the pre-installed equipment is aligned horizontally and azimuthally with the equipment installation base, and a rigid fixed connection is performed. The equipment and the installation base are docked with the local reference installation plane, and the centerline mark in step (6) is aligned with the boss surface of the equipment installation base in step (7), and the boss surface is corrected twice using the reflector of the laser tracker. The fine-tunable waist hole of the equipment installation base in step (7) is used for fine-tuning, so that the boss surface is completely aligned with the centerline of the local reference plane, and the equipment is fixed.

Claims

1. A method for dynamic calibration of a local reference of a ship, comprising the following steps: (1) Select measurement points in the local area of ​​the ship and determine the spatial coordinates of the measurement points; fit the plane coordinate system and spatial coordinates of the target measurement area of ​​the ship to generate the longitudinal horizontal line, the centerline of the ship, and the transverse horizontal line; (2) Using the straightness error evaluation method based on the minimum area method of transformed coordinates, calculate the straightness error t of the minimum condition evaluation; (3) According to the construction length of the hull, the maximum value of the hull centerline and horizontal assembly deviation is queried and used as the deviation calculation value; (4) The maximum value of the queried hull centerline assembly deviation is defined as the in-dock assembly centerline entity deviation Δ zb ; Take 1 / 2 of the deck thickness in the hull measurement area as the sampling point deviation of the non-structural surface of the hull centerline Δ zf , the calculated cumulative deviation of the ship's centerline Δ z Δ is the entity deviation of the centerline of the assembly in the dock zb Deviation from sampling point on non-structured surface Δ zf The difference, Δ z =Δ zb -Δ zf ; (5) The maximum value of the queried horizontal assembly deviation of the hull is defined as the horizontal entity deviation of the assembly in the dock; the sampling point deviation of the horizontal non-structural surface of the hull is taken as 0, and the cumulative deviation value of the horizontal hull Δ is calculated. s is the horizontal entity deviation of the assembly in the dock, that is, Δ s =Δ sb ; (6) Determine the marking deviation u and calculate the total error Δ = t + Δ z +Δ s +u; (7) Extend the local deviation of point measurement to the overall deviation of the entire measurement area, and perform extension conversion of length and angle; (8) Make a local reference installation plane for installing the equipment to be calibrated: Use the already fitted spatial coordinate system to map it to the local reference installation plane, set several measurement points in the local reference installation plane, and calibrate it to determine the horizontality of the local reference installation plane. Polish it to meet the horizontal flatness requirement; use a laser tracker to determine the center line of the local reference plane and mark the center line; (9) Make the equipment installation base for the equipment to be calibrated; (10) The equipment to be calibrated and the equipment mounting base are connected to the local reference mounting plane, the centerline mark of the local reference plane is aligned with the boss surface of the equipment mounting base, and the boss surface is corrected again using the laser tracker reflector. The equipment mounting base is adjusted so that the boss surface is aligned with the centerline of the local reference plane, and the equipment mounting base is fixed.

2. The ship local reference dynamic calibration method according to claim 1, characterized in that: In step (1), the method for selecting measurement points in the local area of ​​the ship and determining the spatial coordinates of the measurement points is as follows: based on the original longitudinal girder structure and the strong transverse beam structure position of the hull, corresponding marks are made on the deck surface, the laser tracker device is set up at a position where all the measurement points can be observed, a reflector is set at the measurement point, and the coordinate data of the measurement point is scanned and recorded by the laser tracker device to determine the spatial coordinates p (x, y, z) of the measurement point.

3. The ship local reference dynamic calibration method according to claim 2, characterized in that: The method for determining the spatial coordinates of the measuring point is: based on the principle of spatial polar coordinate measurement, a spatial coordinate system is constructed based on the horizontal rotation axis and the vertical rotation axis of the laser tracking head and their intersection points, and the spatial coordinates p (x, y, z) of the measuring point are obtained through the measured pitch angle (EL) and horizontal azimuth angle (AZ) parameters of the laser head deflection and the radius distance parameter r from the center of the laser head to the measuring point p.

4. The method for dynamic calibration of a local reference of a ship according to claim 1, characterized in that: The method of step (2) is: Suppose there are n measuring points p i (x i ,y i , z i ), i = l, 2, ..., n, the ideal straight line for evaluating the straightness error according to the minimum condition is l, select a, b and translation c, so that l is rotated around the x-axis by an angle a to become a straight line l1 parallel to the plane zox, and rotated around the y-axis by an angle b to become a straight line l2 parallel to the yoz axis, l2 is then subjected to coordinate translation c, where the translations along the x, y, and z axes are Δ x , Δ y , 0, after shifting, it is a straight line lˊ, then lˊ is made to coincide with the z-axis, where a is the angle between the straight line l and the plane xoz, b is the angle between the straight line l1 and the z-axis, (-Δ x , -Δ y , 0) is the coordinate of the intersection of the straight line l2 and the xoy plane; The coordinates of each measuring point and the ideal straight line l are transformed together. After the transformation, l is transformed into a straight line lˊ parallel to the z-axis. i (x i ,y i , z i ), i = 1, 2, ..., n, the coordinate transformation is p i ˊ(x i ˊ,y i ˊ, z i ˊ)(i=1,2,……,n), let the distance from each measuring point to the ideal straight line be d i , d max is d i The maximum value, d max is a function of (a, b, c), find the function d max Minimum value, denoted as min d max , then mind max Twice the straightness error is the minimum condition evaluation: t=2×mind max (a,b,c)。 5. The method for dynamic calibration of a local reference of a ship according to claim 1, characterized in that: The calculation method of the deviation angle θ of the angle extension in step (9) is as follows: assuming that the overall length of the ship is L, the longitudinal deviation value a1 of the local length L1 area of ​​the ship is obtained by point measurement, and then the deviation angle θ of the L1 area is calculated. a , and then calculate the theoretical deviation angle of the entire measurement area 6. The method for dynamic calibration of a local reference of a ship according to claim 1, characterized in that: Step (9) The equipment installation base of the equipment to be calibrated is manufactured according to the following characteristics: first, the center line of the equipment installation base is marked, and the parallelism between the equipment to be calibrated and the center line is not less than 0.2 mm; second, the installation surface is polished, and the flatness is within 1 mm. 2 The range does not exceed 0.3mm; third, two bosses are set on one side of the equipment installation base, and the flatness of the surface is within 1m 2 The range does not exceed 0.1mm, and the parallelism between the outer surface of the boss and the center line of the base is not less than 0.2mm; fourth, a fine-tuned waist-shaped hole is set for adjustment.

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