A scanning-based center of gravity measurement device and measurement method

Abstract

A scanning-based center of gravity measuring device and method, including a base, a longitudinal support mechanism capable of being adjusted in the vertical direction is arranged on the base, one end of a horizontal slide bar capable of being adjusted in the horizontal direction is connected to the top of the longitudinal support mechanism, the other end of the horizontal slide bar is connected to a vertically arranged standard ball bar through a hook, more than two spheres for collecting measurement data are integrally formed on the standard ball bar, and the lower end of the standard ball bar is connected to the workpiece to be measured through a universal connector. The present invention can be used for the center of gravity of objects of various shapes and sizes, including but not limited to drone models, dummy models, hulls, aircraft models, etc. For super-large products, a crane can be used to lift them, and then a long-distance scanner can be used to measure and obtain the center of gravity coordinates of the object to be measured. The present invention has good versatility, strong adaptability, simple and reliable operation, fast measurement speed, low cost, high measurement accuracy, and can meet the center of gravity measurement needs of products composed of complex mechanisms and complex materials.

Description

Technical Field

[0001] The present invention relates to a gravity center measuring device, and in particular to a gravity center measuring device and a measuring method based on scanning. Background Art

[0002] For many occasions such as aircraft, ships, and test dummies, it is necessary to obtain their center of gravity to detect whether the actual center of gravity position is consistent with the designed center of gravity position. If it does not meet the requirements, it is necessary to use counterweights and other means to adjust the center of gravity position to ensure that the deviation is within the allowable range. The traditional method of measuring the center of gravity requires customized special fixtures according to the object to be measured. One measurement process requires multiple sets of fixtures, and weighing or displacement sensors are also required. The measurement process is very cumbersome, with low accuracy and poor versatility. Patent [201910259540.4] introduces a center of gravity measurement device for measuring test dummies. The fixture structure is complex, requires multiple adjustments, and has no versatility. Patent [201822273860.9] introduces a center of gravity measurement device for a target drone, which requires multiple sets of fixtures and can only be used for measurements of a certain type of aircraft. The measurement accuracy is also not high. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a scanning-based center of gravity measurement device and measurement method with good versatility, fast measurement speed and high accuracy.

[0004] The technical solution adopted by the present invention is: a scanning-based center of gravity measuring device and measuring method, including a base, a longitudinal support mechanism that can be adjusted in the vertical direction is provided on the base, the top end of the longitudinal support mechanism is connected to one end of a horizontal sliding rod that can be adjusted in the horizontal direction, the other end of the horizontal sliding rod is connected to a vertically arranged standard ball rod through a hook, the standard ball rod is integrally formed with more than two spheres for collecting measurement data, and the lower end of the standard ball rod is connected to a workpiece to be measured through a universal connector.

[0005] The measuring method of the center of gravity measuring device based on scanning comprises the following steps:

[0006] 1) The screw at the lower end of the universal connector connected to the lower end of the standard ball rod vertically hung on the horizontal sliding rod through a hook is threadedly connected to the internal threaded hole formed on the surface of the workpiece to be measured with a marking point attached, and the workpiece to be measured is naturally suspended and stationary;

[0007] 2) Scanning the workpiece to be measured and the standard ball bar with a scanner to obtain point cloud data of the workpiece to be measured and the standard ball bar;

[0008] 3) Separate the universal connector from the workpiece to be measured, and connect a suction cup to the bottom of the universal connector, and use the suction cup to suck other positions of the workpiece to be measured, and wait for the workpiece to be measured to be still;

[0009] 4) Use a scanner to scan and obtain point cloud data of another position of the workpiece being measured and the standard ball bar;

[0010] 5) Repeat steps 3) to 4) until the set number of point cloud data is obtained;

[0011] 6) The two point cloud data are converted into coordinate systems according to the point cloud data of the workpiece shape or the marking points, so that the two point cloud data are unified into one coordinate system;

[0012] 7) Fit the two point cloud data of the standard club to form a ball, and obtain the coordinate position of the center of the ball, that is, obtain the coordinate values ​​of the center of the ball A1, A2, A3 and B1, B2, B3;

[0013] 8) Use the least square method to fit the fitting straight lines AL of the sphere centers A1, A2, and A3, and the fitting straight lines BL of the sphere centers B1, B2, and B3;

[0014] 9) Repeat steps 6) to 8) until all the fitting straight lines of the set secondary point cloud data are obtained; the coordinate value of the approximate intersection point O of all the fitting straight lines is calculated, and the coordinate value of the intersection point O is the center of gravity value of the workpiece being measured.

[0015] The scanning-based center of gravity measuring device and method of the present invention can achieve a measurement accuracy of within 0.2 mm or even higher, has good versatility, fast measurement speed, and saves a lot of costs. The present invention can be used for the center of gravity of objects of various shapes and sizes, including but not limited to drone models, dummy models, hulls, aircraft models, etc. For super-large products, a crane can be used to lift them, and then a long-distance scanner can be used to measure the center of gravity coordinates of the object to be measured. The present invention has the characteristics of strong adaptability, simple and reliable operation, low cost, and high precision, and can meet the center of gravity measurement needs of products composed of complex mechanisms and complex materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of a scanning-based center of gravity measurement device of the present invention;

[0017] Figure 2 yes Figure 1 A magnified schematic diagram of the local structure in FIG.

[0018] Figure 3 It is a schematic diagram of another connection method between the present invention and the workpiece to be measured;

[0019] Figure 4 It is a schematic diagram of the measurement method of the present invention.

[0020] In the figure

[0021] 1: Vibration isolation pad 2: Base

[0022] 3: Vertical support 4: Lower locking screw

[0023] 5: Vertical slide bar 6: Upper locking screw

[0024] 7: Slide bar 7.1: Groove

[0025] 8: Hook 9: Standard club

[0026] 9.1: Sphere 9.2: Rod

[0027] 10: Universal connector 11: Scanner

[0028] 12: Workpiece being measured 13: Marking point

[0029] 14: Suction cup DETAILED DESCRIPTION

[0030] A scanning-based center of gravity measurement device and method of the present invention are described in detail below in conjunction with the embodiments and drawings.

[0031] like Figure 1 As shown, a scanning-based center of gravity measuring device of the present invention includes a base 2, on which a longitudinal support mechanism capable of being adjusted in the vertical direction is provided, the top end of the longitudinal support mechanism is connected to one end of a horizontal sliding rod 7 capable of being adjusted in the horizontal direction, the other end of the horizontal sliding rod 7 is connected to a vertically arranged standard ball rod 9 through a hook 8, the standard ball rod 9 is integrally formed with more than two spheres 9.1 for collecting measurement data, and the lower end of the standard ball rod 9 is connected to a workpiece 12 to be measured through a universal connector 10.

[0032] like Figure 2 As shown, the standard club 9 includes a rod body 9.2, and two or more spheres 9.1 are formed integrally on the rod body 9.2 at equal intervals, and the vertical center axis of each sphere 9.1 is in a straight line with the center axis of the rod body 9.2. The cross-sliding rod 7 is formed with a groove 7.1 at one end connected to the hook 8, and the hook portion of the hook 8 is embedded in the groove 7.1, so that the hook 8 can be stably hung in the groove of the cross-sliding rod 7.

[0033] like Figure 1 , Figure 2 As shown, the upper end of the standard ball rod 9 is formed with an internal thread hole, and the end of the vertical part of the hook 8 is formed with an external thread, and the standard ball rod 9 is threadedly connected to the hook 8; the lower end of the standard ball rod 9 is formed with an internal thread hole, and the lower end of the standard ball rod 9 is connected to the screw rod at the upper end of the universal connector 10 through the internal thread hole. The screw rod formed at the lower end of the universal connector 10 is threadedly connected to the internal thread hole formed on the workpiece 12 to be measured.

[0034] like Figure 3 As shown, the lower end of the universal connector 10 can also be connected to the workpiece 12 through a suction cup 14, and an internal threaded hole is formed on the upper end of the suction cup 14. The screw formed at the lower end of the universal connector 10 is threadedly connected to the internal threaded hole on the suction cup 14.

[0035] like Figure 1 As shown, the bottom end is fixedly connected to the longitudinal support 3 on the base 2 and the longitudinal slide bar 5 connected to the upper end of the longitudinal support 3, the longitudinal support 3 has an adjustment groove formed along the axial direction, the lower part of the longitudinal slide bar 5 can be inserted into the adjustment groove movably up and down, and is positioned by the lower locking screw 4 set on the side of the upper port of the longitudinal support 3, and the upper end of the longitudinal slide bar 5 has a through hole formed in the radial direction, the transverse slide bar 7 can be inserted into the through hole movably, and is positioned by the upper locking screw 6 set on the side of the upper end of the longitudinal slide bar 5. A vibration isolation pad 1 is fixedly set at the bottom of the base 2.

[0036] The measuring method of the center of gravity measuring device based on scanning of the present invention comprises the following steps:

[0037] 1) The screw at the lower end of the universal connector 10 connected to the lower end of the standard ball rod 9 vertically hung on the horizontal sliding rod 7 through the hook 8 is threadedly connected to the internal threaded hole formed on the workpiece 12 to be measured with the marking point 13 on the surface, and the workpiece 12 to be measured is naturally suspended and stationary;

[0038] 2) Scanning the workpiece 12 and the standard ball bar 9 using a scanner 11 to obtain point cloud data of the workpiece 12 and the standard ball bar 9;

[0039] 3) Adoption Figure 3 As shown, the universal connector 10 is separated from the workpiece 12 to be measured, and a suction cup 14 is connected to the bottom end of the universal connector 10, and the suction cup 14 is used to suck the other positions of the workpiece 12 to be measured, and wait for the workpiece 12 to be measured to be stationary;

[0040] 4) Scanning with the scanner 11 to obtain point cloud data of another position of the workpiece 12 and the standard ball bar 9;

[0041] 5) Repeat steps 3) to 4) until the set number of point cloud data is obtained;

[0042] 6) The two point cloud data are converted into coordinate systems according to the point cloud data of the workpiece shape or the marking point 13, so that the two point cloud data are unified into one coordinate system;

[0043] 7) Fitting the two point cloud data of the standard club 9 to form individual balls respectively, and obtaining the coordinate position of the ball center, that is, obtaining the coordinate values ​​of the ball center A1, A2, A3 and B1, B2, B3;

[0044] 8) Using the least square method, the fitting straight lines AL of the sphere centers A1, A2, and A3, and the fitting straight lines BL of the sphere centers B1, B2, and B3 are respectively fitted; including:

[0045] (1) Set n sphere centers at position A, and set the coordinates of the i-th sphere center to be: A i (x i ,y i ,z i );

[0046] (2) Give the standard equation of a straight line in space:

[0047]

[0048] Where x0, y0, z0 are points on the straight line to be found, L, M, N are the coefficients of the fitted straight line to be found;

[0049] (3) The simplified standard equation of a straight line in space is:

[0050]

[0051] Where:

[0052] (4) Substitute the coordinates of the n sphere centers at position A into the simplified standard equation of a straight line in space and calculate the sum of squares between the approximate value and the actual value:

[0053]

[0054] (5) According to the principle of least squares, the extreme value of ΔxΔy has a partial derivative of zero. Calculate the partial derivatives of a, b, c, and d and set them to zero:

[0055]

[0056] Find the values ​​of a, b, c, d:

[0057]

[0058] Get the values ​​of x0, y0, z0 and L, M, N, and thus get the equation of the line;

[0059] (6) Assume that the approximate intersection point of lines A and B is J A-B (x A-B ,y A-B ,z A-B ),

[0060] When there are only two straight lines, the approximate intersection point J A-B (x A-B ,y A-B ,zA-B ) is the measured coordinate of the center of gravity (X z , Y z , Z z );

[0061] 9) Repeat steps 6) to 8) until all the fitting lines of the set secondary point cloud data are obtained; the coordinate value of the approximate intersection point O of all the fitting lines is calculated, and the coordinate value of the intersection point O is the center of gravity value of the workpiece being measured. Including:

[0062] When there are three straight lines, find two more approximate intersection points J A-C (x A-C ,y A-C ,z A-C ),J B-C (x B-C ,y B-C ,z B-C ), the center of gravity coordinates of the workpiece being measured (X z , Y z , Z z ) is calculated as:

[0063]

[0064] When there are more than three straight lines, find the approximate intersection points of each pair of straight lines, and then find the average value of the X, Y, and Z coordinates corresponding to all the approximate intersection points. The average value is the centroid coordinate.

[0065] About approximate intersection point: The intersection point of multiple straight lines obtained by fitting at different positions is theoretically the center of gravity. However, due to measurement errors, the straight lines are not in the same plane. Therefore, when finding the intersection point of two straight lines, the point with the shortest distance between the two straight lines is taken as the intersection point. The point with the shortest distance is called the approximate intersection point.

Claims

1. A method for measuring a center of gravity measuring device based on scanning, the center of gravity measuring device based on scanning comprising a base (2), the base (2) being provided with a longitudinal support mechanism capable of being adjusted in the vertical direction, the top end of the longitudinal support mechanism being connected to one end of a horizontal slide bar (7) capable of being adjusted in the horizontal direction, the other end of the horizontal slide bar (7) being connected to a vertically arranged standard ball bar (9) via a hook (8), the standard ball bar (9) being integrally formed with more than two spheres (9.1) for collecting measurement data, the lower end of the standard ball bar (9) being connected to a workpiece (12) to be measured via a universal connector (10), characterized in that: The method comprises the following steps: 1) A screw rod at the lower end of a universal connector (10) connected to the lower end of a standard ball rod (9) vertically hung on a horizontal slide rod (7) through a hook (8) is threadedly connected to an internal threaded hole formed on a workpiece (12) to be measured with a marking point (13) attached to the surface, and the workpiece (12) to be measured is naturally suspended and stationary; 2) using a scanner (11) to scan the workpiece (12) and the standard ball bar (9) to obtain point cloud data of the workpiece (12) and the standard ball bar (9); 3) separating the universal connector (10) from the workpiece (12) to be measured, and connecting a suction cup (14) to the bottom end of the universal connector (10), and using the suction cup (14) to suck other positions of the workpiece (12) to be measured, and waiting for the workpiece (12) to be measured to be stationary; 4) using a scanner (11) to scan and obtain point cloud data of another position of the workpiece (12) to be measured and the standard ball bar (9); 5) Repeat steps 3) to 4) until the set number of point cloud data is obtained; 6) performing coordinate system conversion on the two point cloud data according to the point cloud data of the workpiece shape or the marking points (13), so that the two point cloud data are unified into one coordinate system; 7) fitting the two point cloud data of the standard club (9) into spheres respectively to obtain the coordinate position of the sphere center, that is, obtaining the coordinate values ​​of the sphere center A1, A2, A3 and B1, B2, B3; 8) Use the least square method to fit the fitting straight lines AL of the sphere centers A1, A2, and A3, and the fitting straight lines BL of the sphere centers B1, B2, and B3; 9) Repeat steps 6) to 8) until all the fitting straight lines of the set secondary point cloud data are obtained; the coordinate value of the approximate intersection point O of all the fitting straight lines is calculated, and the coordinate value of the intersection point O is the center of gravity value of the workpiece being measured.

2. The measuring method of the scanning-based center of gravity measuring device according to claim 1, characterized in that: Step 8) includes: (1) Set n sphere centers at position A, and let the coordinates of the i-th sphere center be: A i (x i ,y i ,z i ); (2) Give the standard equation of a straight line in space: Where x0, y0, z0 are points on the straight line to be found, L, M, N are the coefficients of the fitted straight line to be found; (3) The simplified standard equation of a straight line in space is: Where: (4) Substitute the coordinates of the n sphere centers at position A into the simplified standard equation of a straight line in space and calculate the sum of squares between the approximate value and the actual value: (5) According to the principle of least squares, the extreme value of ΔxΔy has a partial derivative of zero. Calculate the partial derivatives of a, b, c, and d and set them to zero: Find the values ​​of a, b, c, d: Get the values ​​of x0, y0, z0 and L, M, N, and thus get the equation of the line; (6) Assume that the approximate intersection point of lines A and B is J A-B (x A-B ,y A-B ,z A-B ), When there are only two straight lines, the approximate intersection point J A-B (x A-B ,y A-B ,z A-B ) is the measured coordinate of the center of gravity (X z , Y z , Z z )。 3. The measuring method of the scanning-based center of gravity measuring device according to claim 2, characterized in that: When there are three straight lines, find two more approximate intersection points J A-C (x A-C ,y A-C ,z A-C ),J B-C (x B-C ,y B-C ,z B-C ), the center of gravity coordinates of the workpiece being measured (X z , Y z , Z z ) is calculated as: When there are more than three straight lines, find the approximate intersection points of each pair of straight lines, and then find the average value of the X, Y, and Z coordinates corresponding to all the approximate intersection points. The average value is the centroid coordinate.

Images