A method and apparatus for measuring the center of mass of a large non-cylindrical winged vehicle

Abstract

The application provides a large non-cylindrical winged carrier centroid measurement method and device, and the method comprises the following steps: supporting the front and rear ends of a product by using a front vehicle and a rear vehicle; the front vehicle and the rear vehicle are both provided with a weighing sensor; obtaining the centroid coordinates of the front / rear vehicle of the product; the centroid coordinates of the front / rear vehicle of the product are composed of the centroid coordinates of the front / rear vehicle in a horizontal state of the product and the centroid coordinates of the front / rear vehicle in an inclined state of the product; according to the static torque balance principle, the centroid coordinates of the product are composed of the centroid coordinates of the front vehicle of the product, the mass of the front vehicle of the product measured by the weighing sensor, the centroid coordinates of the rear vehicle of the product and the mass of the rear vehicle of the product measured by the weighing sensor. The application is proposed in view of the characteristics of the large non-cylindrical winged carrier, the long fuselage, the large wingspan and the far distance between the belly and the center line of the fuselage, and the rolling method cannot be used for the centroid measurement, and the safety degree and the measurement precision can be improved, and the measurement cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of center of mass measurement technology, and in particular relates to a method and equipment for measuring the center of mass of a large non-cylindrical winged vehicle. Background Technology

[0002] The technology related to large launch vehicles is currently a research hotspot in various countries. Mass and center of mass are important parameters of large launch vehicles. Accurately measuring the coordinates of mass and center of mass helps to improve the attitude control accuracy of the launch vehicle, thereby ensuring the launch vehicle enters orbit precisely; it also helps to optimize payload layout and reduce launch costs.

[0003] First, based on their principles, centroid measurement methods can be categorized into three main types: computer simulation methods, time-domain measurement methods, and frequency-domain measurement methods. Time-domain measurement methods are further divided into static and dynamic methods. Static methods include mechanical repositioning, multi-point weighing, and unbalanced torque methods, while dynamic methods include compound pendulum methods, rotational balancing methods, and moment of inertia methods. Frequency-domain measurement methods include the mass line method and modal analysis methods.

[0004] However, many existing methods for measuring the center of mass have the following drawbacks when measuring large-sized aircraft:

[0005] (1) Safety issues. Dynamic measurement methods are widely used in the inspection of small and medium-sized test pieces, such as the multi-line pendulum method, the unbalanced torque method, and the compound pendulum method. However, because large test pieces are usually large, some problems will be introduced during dynamic measurement. For example, the multi-line pendulum method requires the test piece to be suspended and twisted, and the strength of the suspension wire will affect the process.

[0006] (2) Low measurement accuracy. Dynamic methods such as the multi-line pendulum method and the compound pendulum method have low measurement accuracy when measuring large-sized test pieces, while the multi-point weighing method mainly uses mechanical positioning and requires the test piece to be measured in a specific attitude. Since large-sized aircraft have a large mass, it is difficult to guarantee the positioning accuracy in a specific attitude.

[0007] (3) Poor versatility of measuring equipment. Large-sized aircraft are usually assembled from different parts, and different models of aircraft have different shapes and sizes. However, most of the existing measuring equipment is model-specific, resulting in poor equipment versatility. At present, the measurement method with certain versatility adopts the fixed sensor scheme, which involves setting several weighing sensors at specific locations on the ground. Before testing, the positions of multiple sensors need to be leveled. Practice has shown that this method has low accuracy.

[0008] (4) It is difficult to measure large-volume irregularly shaped test objects. Because large non-cylindrical winged vehicles are tens of meters long and have a wingspan of more than ten meters, they are irregular bodies, so it is impossible to use traditional equipment and methods to measure the center of mass. Summary of the Invention

[0009] In view of this, the present invention aims to propose a method and device for measuring the center of mass of a large non-cylindrical winged vehicle based on fuselage lifting and tilting, so as to measure the center of mass of a large non-cylindrical winged vehicle with a long fuselage, large wingspan, and a large distance between the fuselage belly and the fuselage centerline.

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

[0011] A method for measuring the center of mass of a large non-cylindrical winged vehicle includes the following steps:

[0012] The front and rear carriages support the front and rear ends of the product respectively; both the front and rear carriages are equipped with weighing sensors.

[0013] Obtain the center of gravity coordinates of the front vehicle and the rear vehicle of the product; the center of gravity coordinates of the front vehicle are synthesized from the center of gravity coordinates of the front vehicle when the product is horizontal and the center of gravity coordinates of the front vehicle when the product is tilted; the center of gravity coordinates of the rear vehicle are synthesized from the center of gravity coordinates of the rear vehicle when the product is horizontal and the center of gravity coordinates of the rear vehicle when the product is tilted.

[0014] Based on the principle of static torque balance, the center of mass coordinates of the product are obtained by combining the center of mass coordinates of the product's front vehicle and the mass of the product's front vehicle measured by the weighing sensor, and the center of mass coordinates of the product's rear vehicle and the mass of the product's rear vehicle measured by the weighing sensor.

[0015] Furthermore, the method for synthesizing the centroid coordinates of the front / rear vehicle of the product includes:

[0016] In a horizontal state, the analytical expression of the first line of gravity of the front / rear vehicle of the product in the product coordinate system is calculated from the coordinates of the intersection point of the first line of gravity of the front / rear vehicle of the product and the XOY plane of the product coordinate system, and the direction vector of the first line of gravity of the product in the product coordinate system.

[0017] In the tilted state, the analytical expression of the second line of gravity of the front / rear vehicle of the product in the product coordinate system is calculated from the coordinates of the intersection point of the second line of gravity of the front / rear vehicle of the product and the XOY plane of the product coordinate system, and the direction vector of the second line of gravity of the product in the product coordinate system.

[0018] In the product coordinate system, calculate the estimated coordinates of the intersection point of the analytical expressions of the first and second lines of gravity acting on the front / rear vehicles to obtain the centroid coordinates of the front / rear vehicles.

[0019] Furthermore, the analytical expression for the lines of action of gravity of the front / rear vehicles is calculated as follows:

[0020] The coordinates of the load-bearing point of the weighing sensor in the reference coordinate system are transformed to obtain the coordinates of the load-bearing point of the weighing sensor in the sensor coordinate system. The static moment equilibrium equation is established to obtain the projection point of the product's center of mass on the XOY plane of the sensor coordinate system, which is the intersection of the gravity lines of the front / rear vehicles of the product and the XOY plane of the sensor coordinate system.

[0021] Given that the line of action of gravity passes through the intersection point of the line of action of gravity of the front / rear vehicle of the product and the XOY plane of the sensor coordinate system, and given the direction vector of the line of action of gravity in the sensor coordinate system, use the coordinate transformation matrix to obtain the coordinates of the intersection point of the line of action of gravity of the front / rear vehicle of the product and the XOY plane of the sensor coordinate system in the product coordinate system, as well as the direction vector of the line of action of gravity in the product coordinate system.

[0022] The analytical expression for the gravity lines of the front / rear vehicles of the product is obtained from the coordinates of the intersection points of the gravity lines of the front / rear vehicles of the product coordinate system and the XOY plane of the sensor coordinate system, as well as the direction vector of the gravity lines of the product coordinate system.

[0023] Furthermore, the method for calculating the centroid coordinates of the front / rear vehicle of the product is as follows:

[0024] If the first line of action of gravity intersects with the second line of action of gravity, then the intersection point of the first line of action of gravity and the second line of action of gravity is the coordinate of the center of mass of the front / rear vehicle of the product.

[0025] If the first and second lines of gravity are skew lines, then the midpoint of the common perpendicular of the first and second lines of gravity in the product coordinate system is the coordinate of the centroid of the front / rear vehicle of the product.

[0026] If the first and second lines of action of gravity are skew lines, then the process for determining the coordinates of the center of mass of the front / rear vehicle of the product is as follows:

[0027] Let product coordinate system O P -X P Y P Z P The intersection point of the first line of action of gravity L1 and the common perpendicular is N1(x). N1 y N1 , z N1 The intersection of the second line of action of gravity and the common perpendicular is N2(x). N2 y N2 , z N2 Since the common perpendicular is perpendicular to the first line of gravity L1 and the second line of gravity L2 respectively, the coordinates of the two intersection points N1 and N2 satisfy the following equation:

[0028]

[0029] Where, m1， n 1， p1 represents the direction vector of the first line of action of gravity, L1; m 2， n 2， p2 represents the direction vector of the second line of action of gravity, L2, (x N1 y N1 , z N1 The coordinates are the intersection of the first line of action of gravity L1 and the common perpendicular, (x) N2 y N2 , z N2 The coordinates are the intersection of the first line of action of gravity L2 and the common perpendicular.

[0030] Since the two intersection points N1 and N2 are on the first line of action of gravity L1 and the second line of action of gravity L2 respectively, let

[0031]

[0032] in, The coordinates of the projection point of the first line of action of gravity on the product's center of mass in the product coordinate system. The coordinates of the projection point of the second line of gravity acting on the product's center of mass in the product coordinate system are represented by k1 and k2, which are the slopes of the two lines to be solved.

[0033] Solving the system of equations yields a linear equation in two variables k1 and k2. Solving the equation gives the values ​​of k1 and k2, from which the coordinates of the foot of the perpendicular N1(x) can be determined. N1 y N1 , z N1 N2(x) N2 y N2 , z N2 If the coordinates of the midpoints of line segments N1 and N2 are the coordinates of the centroid, then the product coordinate system O... P -X P Y P Z P The coordinates of the center of gravity of the vehicle before and after the product are:

[0034]

[0035] Among them, (xP cg yP cg zP cg (O is the product coordinate system) P -X P Y P Z P The coordinates of the center of mass of the product's front and rear carriages are determined. Further, based on the principle of static moment balance, the method for synthesizing the product's center of mass coordinates from the coordinates of the front carriage's center of mass and the product's mass measured by the weighing sensor, and the coordinates of the rear carriage's center of mass and the product's mass measured by the weighing sensor, is as follows:

[0036] The product's center of gravity is designated as CG. 前 The product quality measured by the preceding vehicle is M. 前 The rear center of gravity of the product is CG. 后 The product quality measured by the rear vehicle was M. 后 The centroid coordinates of the product are obtained by synthesizing the static moment balance principle:

[0037] Among them, M 前 It is the mass measured by the vehicle in front, M 后 This is the mass measured by the following vehicle; the coordinates of the center of mass of the preceding vehicle in the product coordinate system are: The coordinates of the center of mass of the rear vehicle in the product coordinate system are: The coordinates of the center of mass of the arrow (x) are obtained by solving the simultaneous equations. P y P , z P ).

[0038] Furthermore, the coordinate system transformation method is as follows:

[0039] The coordinate system of the laser tracker is defined as the reference coordinate system; the laser tracker is used to determine the relative position of the product under test with respect to the vehicles in front and behind.

[0040] A reference coordinate system is established by selecting three target seats on the outer perimeter of the front / rear vehicle base as reference points;

[0041] Using the reference coordinate system as an intermediate bridge, calculate the transformation matrix between the sensor coordinate system and the reference coordinate system of the front / rear vehicle, and the transformation matrix between the reference coordinate system and the product coordinate system of the front / rear vehicle, and then obtain the transformation matrix between the sensor coordinate system and the product coordinate system of the front / rear vehicle.

[0042] The sensor coordinate system is established as follows: weighing sensors are installed at the four corners of both the front and rear vehicles; the geometric center of the bearing points of the four weighing sensors is taken as the origin O. S X S The axis starts from the origin O S Z points to the midpoint of the line connecting the bearing points of two adjacent load cells. S The axis is perpendicular to the plane containing the load cells of the four load cells and points upwards. S Determined by the right-hand rule, i.e., X S The axis passes through the right palm, with the thumb pointing to Z. S The axis, then the four fingers refer to Y. S axis;

[0043] The method for establishing the product coordinate system is as follows: origin O p Located at the theoretical apex of the nose cone; X p Axis: Located within the plane of symmetry of the launch vehicle, passing through the origin O.p The normal to the vertical reference plane, pointing towards the rear of the aircraft, is positive; Y p Axis: Located within the spacecraft's plane of symmetry, perpendicular to X. p The axis, pointing towards the back of the fuselage, is positive; Z p Axis: Determined by the right-hand rule, i.e., X p The axis passes through the right palm, with the thumb pointing to Y. p The axis, then the four fingers refer to Z. p The tail end face of the carrier is defined as the vertical reference plane.

[0044] A large non-cylindrical winged vehicle center of mass measurement device includes a front vehicle for supporting the front end of the product and a rear vehicle for supporting the rear end of the product. Both the front and rear vehicles include a measuring vehicle and a support fixture mounted on the measuring vehicle. Each measuring vehicle is equipped with a weighing sensor, and the support fixture is mounted on the weighing sensor.

[0045] There are four load cells, which are set at the four corners of the measuring vehicle. The front and rear vehicles are both set on the guide rails and can move closer or further apart along the guide rails. The top of the support fixture is U-shaped to facilitate the positioning of the workpiece being measured. The four corners of the measuring vehicle are also equipped with anti-deviation lifting devices for adjusting the height of the support fixture.

[0046] The measuring equipment also includes an anti-overturning support and protection platform, which is enclosed in the shape of a fence around the measuring vehicle. Four jacks are installed on its four columns. When the product is installed, the jacks are placed on the bottom of the support fixture. When the product is measured, the top surface of the jacks is lowered and separated from the support fixture.

[0047] An electronic device includes a processor and a memory communicatively connected to the processor and used to store executable instructions of the processor, the processor being used to execute the above-described method for measuring the center of mass of a large non-cylindrical winged vehicle.

[0048] A server includes at least one processor and a memory communicatively connected to the processor, the memory storing instructions executable by the at least one processor, the instructions being executed by the processor to cause the at least one processor to perform the above-described method for measuring the center of mass of a large non-cylindrical winged vehicle.

[0049] A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the aforementioned method for measuring the center of mass of a large non-cylindrical winged vehicle.

[0050] Compared with existing technologies, the method and equipment for measuring the center of mass of a large non-cylindrical winged vehicle described in this invention have the following advantages:

[0051] The present invention provides a method and apparatus for measuring the center of mass of a large non-cylindrical winged vehicle. This method addresses the characteristics of large non-cylindrical winged vehicles, such as long fuselages, large wingspans, and a large distance between the fuselage belly and the fuselage centerline, making it impossible to measure the center of mass using a roll-based method. This method is based on fuselage lifting and tilting for center of mass measurement, and solves the following problems:

[0052] (1) Improve safety. Centroid detection is a multi-point weighing method in static detection. In actual operation, measures such as jacks are used to prevent risks.

[0053] (2) Improve measurement accuracy. Dynamic detection methods have low accuracy. Using multi-point weighing helps the sensor obtain accurate values. The data is then processed by the centroid detection algorithm to obtain more accurate three-dimensional coordinates of the centroid.

[0054] (3) Reduced detection costs and provided important parameter support for subsequent attitude control and payload configuration of the launch vehicle. Attached Figure Description

[0055] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0056] Figure 1 This invention illustrates a schematic diagram of the physical model of the flexible mass center measurement system for the mass center measurement method of a large non-cylindrical winged vehicle according to an embodiment of the present invention.

[0057] Figure 2 The actual installation of the equipment sensors for the centroid measurement method of a large non-cylindrical winged vehicle according to an embodiment of the present invention is shown.

[0058] Figure 3 This invention illustrates a schematic diagram of the entire aircraft coordinate system for the method of measuring the center of mass of a large non-cylindrical winged vehicle according to an embodiment of the invention.

[0059] Figure 4 This diagram illustrates the quadrant definition of the storage tank region from back to front in the method for measuring the center of mass of a large non-cylindrical winged vehicle according to an embodiment of the present invention.

[0060] Figure 5 This invention illustrates the principle of the coordinate transformation algorithm for the centroid measurement method of a large non-cylindrical winged vehicle according to an embodiment of the invention.

[0061] Figure 6 This invention presents a schematic diagram of the overall structure of the large non-cylindrical winged vehicle center of mass measurement device according to an embodiment of the invention.

[0062] Figure 7This invention illustrates the internal structure of the front / rear vehicle of the large non-cylindrical winged vehicle center of mass measurement device according to an embodiment of the invention.

[0063] Figure 8 This diagram illustrates the product level measurement status of the centroid measuring device for a large non-cylindrical winged vehicle according to an embodiment of the present invention.

[0064] Figure 9 This diagram illustrates the product tilt measurement state of the centroid measuring device for a large non-cylindrical winged vehicle according to an embodiment of the present invention.

[0065] Figure 10 This invention illustrates a schematic diagram of the front-end anti-tipping support protection platform structure of the large non-cylindrical winged vehicle center of mass measurement equipment according to an embodiment of the present invention;

[0066] Figure 11 This invention illustrates a schematic diagram of the rear anti-tipping support protection platform structure of the large non-cylindrical winged vehicle center of mass measurement equipment according to an embodiment of the present invention.

[0067] Figure 12 This diagram illustrates the structural schematic of the preparation stage of the centroid measurement device for a large non-cylindrical winged vehicle according to an embodiment of the present invention.

[0068] Figure 13 This diagram illustrates the structural schematic of the product level measurement stage of the centroid measurement device for a large non-cylindrical winged vehicle according to an embodiment of the present invention.

[0069] Figure 14 This diagram illustrates the structural schematic of the product tilt measurement stage of the centroid measurement device for a large non-cylindrical winged vehicle according to an embodiment of the present invention. Detailed Implementation

[0070] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0071] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0072] I. Measurement Principle

[0073] The physical model of the centroid flexible measurement system is as follows Figure 1As shown, the so-called flexible measurement method refers to a measurement system consisting of two relatively independent measurement subsystems: a front carriage and a rear carriage. The measurement carriage is mounted on a linear guide rail on site. Each subsystem uses four high-precision load cells to support the upper measurement platform, i.e., the support fixture. The fixture, shape, and relative distance between the two subsystems can be changed according to different measured parts sizes. The measurement system has strong compatibility and ensures a safe and stable measurement process. The positional relationship between the two subsystems and between the subsystem and the measured part is measured using a laser tracker. Combined with the load cell measurements, the mass and three-dimensional centroid of the measured part can be obtained. The actual installation of the load cells in this system is shown below. Figure 2 .

[0074] The measurement process is explained using the previous vehicle as an example.

[0075] In the first measurement state, the product being measured is placed horizontally. Measurements are taken of the product to obtain the coordinates of the intersection point of the first line of gravity acting from the vehicle in front and the XOY plane of the sensor coordinate system, as well as the direction vector of the first line of gravity acting.

[0076] By utilizing the transformation relationships between the sensor coordinate system and the reference coordinate system, and between the reference coordinate system and the product coordinate system, the coordinates of the intersection point of the first line of gravity action of the vehicle in front and the XOY plane of the sensor coordinate system, as well as the direction vector of the first line of gravity action, are obtained in the product coordinate system. Then, the analytical expression of the first line of gravity action in the product coordinate system is obtained.

[0077] The product is tilted at 12° to place it in the second measurement state. The product is then measured to obtain the coordinates of the intersection point of the second line of gravity of the front vehicle and the XOY plane of the sensor coordinate system, as well as the direction vector of the second line of gravity.

[0078] By utilizing the transformation relationships between the sensor coordinate system and the reference coordinate system, and between the reference coordinate system and the product coordinate system, the coordinates of the intersection point of the second gravity line of the front vehicle and the XOY plane of the sensor coordinate system in the product coordinate system, as well as the direction vector of the second gravity line, are obtained. Then, the analytical expression of the second gravity line in the product coordinate system is obtained.

[0079] Finally, the estimated coordinates of the intersection of the two gravity lines of the front vehicle in the product coordinate system are obtained, which are the coordinates of the center of mass of the front vehicle.

[0080] During the measurement of the center of gravity coordinates of the preceding vehicle, the following vehicle simultaneously completes all the steps of the preceding vehicle's measurement, thus obtaining the center of gravity coordinates of the following vehicle.

[0081] The centroid coordinates measured by the front and rear vehicles are combined to obtain the final centroid coordinates of the product.

[0082] The centroid calculation process involves multiple coordinate systems, which are defined as follows:

[0083] O S -X S Y S Z S The sensor coordinate system is defined by the load-bearing points S of the four weighing sensors on the vehicle's base. i (i = 1, 2, 3, 4) are determined, and the geometric center of the bearing point of the four weighing sensors is taken as the origin O. S X S The axis starts from the origin O S Z points to the midpoint of the line connecting the load-bearing points S3 and S4 of the third and fourth load cells. S The axis is perpendicular to the plane containing the four points and points upwards, Y S Determined by the right-hand rule, i.e., X S The axis passes through the right palm, with the thumb pointing to Z. S The axis, then the four fingers refer to Y. S The measurement system consists of two subsystems, one on the front vehicle and one on the rear vehicle. The coordinate system determined by the coordinates of the load-bearing points of the four weighing sensors on the front vehicle is called the front vehicle sensor coordinate system O. S1 -X S1 Y S1 Z S1 The coordinate system determined by the coordinates of the bearing points of the four weighing sensors on the rear vehicle is called the rear vehicle sensor coordinate system O. S2 -X S2 Y S2 Z S2 .

[0084] O P -X P Y P Z P The product coordinate system, which is the overall coordinate system of the large non-cylindrical winged vehicle in this embodiment, is specified by the product designer, and the final measurement results of the three-dimensional centroid are all represented in the product coordinate system.

[0085] The overall coordinate system defined in this embodiment is as follows:

[0086] Origin O: Located at the theoretical vertex of the nose. The actual vertex of the nose is the point farthest from the vertical reference plane by the line of intersection between the plane of symmetry of the launch vehicle and the outer surface of the fuselage. The actual vertex of the nose is consistent with the theoretical vertex, and its coordinates in the whole aircraft coordinate system are (0, 0, 0).

[0087] X-axis: Located within the symmetry plane of the launch vehicle, it is the normal to the vertical reference plane passing through the origin O of the coordinate system, pointing towards the rear of the aircraft as positive;

[0088] Y-axis: Located within the plane of symmetry of the launch vehicle, perpendicular to the X-axis, with the direction pointing towards the back of the aircraft as positive;

[0089] Z-axis: Determined according to the right-hand rule, that is, if the X-axis passes through the right palm and the thumb points to the Y-axis, then the four fingers point to the Z-axis;

[0090] The tail end face of the launch vehicle is defined as the vertical reference plane, and the overall coordinate system OXYZ is as follows: Figure 3 As shown.

[0091] The quadrant definition for the tank area of ​​a large non-cylindrical winged vehicle is as follows: Figure 4 (Looking from back to front)

[0092] To determine the relative position of the product under test and the measuring equipment, a laser tracker is introduced for measuring the coordinates of key points. For ease of description, the coordinate system of the laser tracker is defined as the reference coordinate system O. L -X L Y L Z L .

[0093] To determine the position of the weighing sensor during product measurement, three target seats on the periphery of the measuring vehicle base were selected as reference points C. i (i = 1, 2, 3), used to establish the reference coordinate system O C -X C Y C Z C The origin O is taken as the geometric center of the three reference points. C X C The axis starts from the origin O C Pointing to the first reference point C1, Z C The axis is perpendicular to the plane containing the three points and points upwards. C Determined by the right-hand rule, i.e., X C The axis passes through the right palm, with the thumb pointing to Z. C The axis, then the four fingers refer to Y. C axis.

[0094] Coordinate system transformations are typically achieved through rotation and translation, and the transformation algorithms usually rely on matrix operations. Suppose that the coordinates of point A in space in coordinate system N are (x... N ,y N ,z N ), in the M coordinate system, the coordinates are (x M ,y M ,z M The transformation matrix between the N coordinate system and the M coordinate system is T. NM Then the following relationship exists between the two coordinate systems:

[0095]

[0096] Transformation matrix T NMIt can be represented as:

[0097]

[0098] In the formula R NM —The rotation matrix from the N coordinate system to the M coordinate system;

[0099] C NM —The translation vector from the N coordinate system to the M coordinate system.

[0100] The key to coordinate transformation algorithms lies in calculating the rotation matrix and translation vector between the two coordinate systems. For example... Figure 5 As shown, since the positioning points used to establish the coordinate system are initially described in the reference coordinate system, the coordinate system O of the front vehicle sensor can be calculated using the reference coordinate system as an intermediate bridge. S1 -X S1 Y S1 Z S1 Reference coordinate system O of the preceding vehicle R1 -X R1 Y R1 Z R1 Forward vehicle reference coordinate system O R1 -X R1 Y R1 Z R1 With product coordinate system O P -X P Y P Z P The transformation matrix between them is used to obtain the coordinate system O of the front vehicle sensor. S1 -X S1 Y S1 Z S1 With product coordinate system O P -X P Y P Z P The transformation matrix.

[0101] Similarly, the coordinate system O of the rear vehicle sensor can be calculated using the reference coordinate system as an intermediate bridge. S2 -X S2 Y S2 Z S2 With reference coordinate system O of the rear vehicle R2 -X R2 Y R2 Z R2 Rear vehicle reference coordinate system O R2 -X R2 Y R2 Z R2 With product coordinate system O P -X P Y P Z PThe transformation matrix between them is used to obtain the rear vehicle sensor coordinate system O. S2 -X S2 Y S2 Z S2 With product coordinate system O P -X P Y P Z P The transformation matrix.

[0102] II. Calculation process:

[0103] First, an unloaded measurement is performed, at which point the mass of the supporting fixture is measured:

[0104]

[0105] In the formula, M0 represents the mass of the supporting tooling.

[0106] m 0i (i=1,2,...,8)——Measurement values ​​of 8 weighing sensors during no-load measurement.

[0107] Load the workpiece under test, record the current measurement values ​​of the 8 weighing sensors and the measurement posture of the workpiece, and obtain the total mass of the support fixture and the workpiece under test as follows:

[0108]

[0109] In the formula, M1 represents the total mass of the supporting fixture and the workpiece being measured.

[0110] m 1i (i = 1, 2, ..., 8) — Measurement values ​​of 8 weighing sensors after loading the test piece.

[0111] The mass of the measured part can be obtained by subtracting the two equations:

[0112]

[0113] In the formula, M represents the mass of the measured part.

[0114] Δm i —Measurement values ​​of 8 weighing sensors before and after loading the test piece.

[0115] The calculation of the center of mass will still be explained using the front vehicle as an example. The calculated centers of mass of the front and rear vehicles will then be combined. The parameters required to establish the 3D center of mass calculation model of the front vehicle are as follows:

[0116] Table 1. Relevant parameters for establishing the three-dimensional centroid calculation model.

[0117]

[0118] Describe the first line of gravity action L1 of the product in the product coordinate system, and determine the center of mass of the product in the X and Z directions when the product is placed horizontally.

[0119] The coordinates of the load-bearing point of the weighing sensor in the instrument coordinate system (i = 1, 2, 3, 4) After coordinate transformation, the coordinates of the load-bearing point of the weighing sensor in the sensor coordinate system are obtained. (i = 1, 2, 3, 4), by establishing the static moment equilibrium equation, we can obtain the first line of action of gravity L1 in the measurement coordinate system and the line of action of gravity in the sensor coordinate system X. S O S Y S The intersection of the surfaces, that is, the product's center of mass at X. S O S Y S The projection point of the plane is denoted as CG1:

[0120] Projection point CG1 at X S Y S The coordinates along the axis are as follows.

[0121]

[0122] Since the first line of gravity, L1, passes through point CG1, and the direction vector of L1 in the sensor coordinate system is (0,0,1), the coordinates of the projection point CG1 in the product coordinate system can be obtained using the coordinate transformation matrix.

[0123] The direction vector of L1 in the product coordinate system is (m1, n1, p1).

[0124]

[0125] Therefore, the analytical expression for product L1 in the product coordinate system is:

[0126]

[0127] Describe the second line of gravity action L2 of the product in the product coordinate system, and determine the center of mass of the product in the Y direction in the front of the product when it is placed at an angle.

[0128] The coordinates of the load-bearing point of the weighing sensor in the sensor coordinate system are known. (i = 1, 2, 3, 4), by establishing the static moment equilibrium equation, the center of mass of the product at X can be obtained. S O S Y S The coordinates of the projection point of the surface in the measurement coordinate system are denoted as CG2:

[0129] Projection point at XS Y S The coordinates along the axis are as follows.

[0130]

[0131] Since the second line of action of gravity L2 passes through point CG2, and the direction vector of L2 in the sensor coordinate system is (0,0,1), the coordinates of the projection point CG2 in the product coordinate system can be obtained using the coordinate transformation matrix.

[0132] The direction vector of L2 in the product coordinate system is (m2, n2, p2).

[0133]

[0134] Therefore, the analytical expression for L2 in the product coordinate system is:

[0135]

[0136] Calculating the center of mass CG of the front of the product: When L1 and L2 intersect, the intersection point between L1 and L2 is the center of mass, which is relatively simple to solve; when L1 and L2 are skew lines, it is necessary to calculate the midpoint of the common perpendicular of L1 and L2 in the product coordinate system to obtain the best estimate of the center of mass. The solution process is as follows:

[0137] Let N1(x) be the intersection point of L1 and the common perpendicular in the product coordinate system. N1 y N1 , z N1 The intersection of L2 and the common perpendicular is N2(x). N2 y N2 , z N2 Since the common perpendicular is perpendicular to L1 and L2 respectively, the coordinates of the two intersection points satisfy the following equation:

[0138]

[0139] Since the two intersection points are on L1 and L2 respectively, let

[0140]

[0141] Solving the system of equations yields a linear equation in two variables k1 and k2. Solving the equation gives the values ​​of k1 and k2, from which the coordinates of the foot of the perpendicular N1(x) can be determined. N1 y N1 , z N1 N2(x) N2 y N2 , z N2 The coordinates of the midpoint of line segment N1N2 are the estimated coordinates of the centroid. P -X P Y P ZP The CG coordinates of the center of gravity of the vehicle before the product are:

[0142]

[0143] The product's center of gravity is designated as CG. 前 The product quality measured by the preceding vehicle is M. 前 The rear center of gravity of the product is CG. 后 The product quality measured by the rear vehicle was M. 后 The centroid coordinates of the product are obtained by synthesizing the static moment balance principle:

[0144] Among them, M 前 It is the mass measured by the vehicle in front, M 后 This is the mass measured by the following vehicle; the coordinates of the center of mass of the preceding vehicle in the product coordinate system are: The coordinates of the center of mass of the rear vehicle in the product coordinate system are: The coordinates of the center of mass of the arrow (x) are obtained by solving the simultaneous equations. P y P , z P ).

[0145] III. Measuring Equipment

[0146] Mass centroid measurement equipment, see Figure 6 It includes a front vehicle and a rear vehicle, used for mass and lateral and longitudinal center of gravity measurement of large non-cylindrical winged vehicles, including two flexible and independent high-precision combined measurement vehicles (internal structure see...). Figure 7 The system includes a front support fixture, a rear support fixture, an inclined measuring fixture, and an anti-tipping support protection platform. The support fixture is mounted on the measuring vehicle and supported by a load cell inside the vehicle. The top of the support fixture is U-shaped to facilitate the positioning of the workpiece. Anti-deviation lifting devices are also provided at the four corners of the measuring vehicle to adjust the height of the support fixture. Sensor position measurement points are set on the outer wall of the measuring vehicle, opposite to the load cell, for measuring the position of the load cell.

[0147] This measuring equipment can be used with high-precision spatial coordinate measuring instruments (such as laser trackers) to accurately obtain the positional relationship between two measuring carriages and between the measuring carriage and the product, and to accurately measure the mass and transverse and longitudinal centroids of the product being measured. This system is also an integrated assembly and measurement platform; when not measuring mass and centroids, it can be used to support the product and perform assembly work.

[0148] Measurement requirements:

[0149] The system is required to measure both the retracted and extended landing gear states, with a mass measurement accuracy of 5 kg (product weight approximately 30 t); and a center of mass measurement accuracy of 5 mm in the X, Y, and Z directions.

[0150] Measurement plan:

[0151] This section describes the measurement scheme for large non-cylindrical winged vehicles, using the landing gear lowered and the hatch open as an example.

[0152] (1) When the product is placed horizontally, the mass and centroid of the carrier in the X and Z directions are measured by the front / rear vehicles. The actual carrier placement is as follows. Figure 8 As shown.

[0153] (2) Place the product at a certain angle and measure the centroid in the Y direction.

[0154] To achieve the measurement status after the carrier tilts at a certain angle, the rear vehicle replaced its tilt measurement rear support fixture with a special one, while the front vehicle added a support fixture several meters high to its original horizontal measurement support fixture. Simultaneously, both the front and rear vehicles were designed with anti-tipping support protection platforms to prevent hazards caused by fixture tilting during product installation and measurement. The product status at this stage is as follows: Figure 9 As shown.

[0155] (3) Product and tooling support interface

[0156] Since the product needs to be tilted at a certain angle when measuring the Y-axis centroid, it is necessary to use a lifting shaft at the front end of the product and two support points at the front and rear ends of the product and support fixtures for positioning and connection.

[0157] (4) Anti-overturning support and protection platform

[0158] The anti-tipping support and protection platform is enclosed in a fence-like manner around the measuring vehicle, with four hydraulic jacks mounted on its four columns. During product installation, the jacks press against the bottom circular holes of the support fixture to protect it and prevent tilting. During product measurement, the support fixture and the product contact the load cell via steel balls. To prevent accidental tilting of the support fixture, the top surfaces of the four hydraulic jacks lower to approximately 2mm below the support fixture, protecting the product without affecting the measurement process. Limiting devices ensure product safety during measurement. Simultaneously, the measuring vehicle can move on the track using wheels, ensuring no damage to the equipment when changing measurement locations within the factory. See the front and rear anti-tipping support and protection platforms for details. Figure 10 and Figure 11 .

[0159] Equipment Installation Tutorial

[0160] (1) Preparation stage

[0161] Prepare a high-precision combined measurement vehicle, front support fixture, rear support fixture, tilt measurement fixture, anti-tipping support and protection platform, etc. Place the two measurement vehicles in suitable positions on the guide rails. Figure 12 Connect the control cabinet for initial debugging.

[0162] (2) Install level measuring fixture

[0163] Product level measurement fixtures, such as Figure 13 As shown, when measuring the product horizontally, the front support fixture, anti-tipping protection platform, hydraulic jack, etc. on the front vehicle can be installed together on the measuring vehicle. If the bottom area of ​​the support fixture on the rear vehicle is small, the two side crossbeams can be installed separately to support the jack and the rear support fixture. The anti-tipping protection platform on the rear vehicle can be installed after adjusting the distance between the two measuring vehicles before measuring the product tilt.

[0164] (3) Install tilt measuring fixture

[0165] After adjusting the distance between the front and rear vehicles, first install the rear vehicle's anti-tipping support protection platform and hydraulic jacks, then install the rear support fixture. When installing the front support fixture, first remove the upper part that contacts the lifting shaft, install it on top of the newly added front support fixture in the middle, and then connect the two support fixture sections to the bottom. The installed fixture should look like this. Figure 14 As shown.

[0166] This invention provides a method and equipment for measuring the center of mass of a large non-cylindrical winged vehicle. Because the center of mass of a non-cylindrical winged vehicle cannot be detected by traditional rotation methods, the existing mechanical structure, algorithm, and supporting software are optimized. Specifically, a supporting fixture is added to the existing tooling, and the optimized algorithm is used to detect the center of mass of the vehicle in a fixed state. This invention meets the needs for detecting the center of mass of irregularly shaped, large-volume vehicles, improves the accuracy of center of mass detection, provides a solution for the testing of large instruments, and is currently at the forefront of technological advancements. Furthermore, by upgrading the existing tooling, the cost of center of mass measurement is reduced.

[0167] Those skilled in the art will recognize that the units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0168] In the several embodiments provided in this application, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the division of units described above is merely a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. The aforementioned units may or may not be physically separated. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of the present invention according to actual needs.

[0169] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

[0170] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring the center of mass of a large non-cylindrical winged vehicle, characterized in that, Includes the following steps: The front and rear carriages support the front and rear ends of the product respectively; both the front and rear carriages are equipped with weighing sensors. Obtain the center of gravity coordinates of the front vehicle and the rear vehicle of the product; the center of gravity coordinates of the front vehicle are synthesized from the center of gravity coordinates of the front vehicle when the product is horizontal and the center of gravity coordinates of the front vehicle when the product is tilted; the center of gravity coordinates of the rear vehicle are synthesized from the center of gravity coordinates of the rear vehicle when the product is horizontal and the center of gravity coordinates of the rear vehicle when the product is tilted. Based on the principle of static torque balance, the center of mass coordinates of the product are obtained by combining the center of mass coordinates of the product's front vehicle and the mass of the product's front vehicle measured by the weighing sensor, the center of mass coordinates of the product's rear vehicle and the mass of the product's rear vehicle measured by the weighing sensor. The methods for synthesizing the centroid coordinates of the front and rear vehicles of the product include: In a horizontal state, the analytical expression of the first line of gravity of the front / rear vehicle of the product in the product coordinate system is calculated from the coordinates of the intersection point of the first line of gravity of the front / rear vehicle of the product and the XOY plane of the product coordinate system, and the direction vector of the first line of gravity of the product in the product coordinate system. In the tilted state, the analytical expression of the second line of gravity of the front / rear vehicle of the product in the product coordinate system is calculated from the coordinates of the intersection point of the second line of gravity of the front / rear vehicle of the product and the XOY plane of the product coordinate system, and the direction vector of the second line of gravity of the product in the product coordinate system. In the product coordinate system, calculate the estimated coordinates of the intersection point of the analytical expressions of the first and second lines of gravity of the front / rear vehicles to obtain the centroid coordinates of the front / rear vehicles. The analytical expression for the lines of action of gravity of the front / rear vehicles of the product is calculated as follows: The coordinates of the load-bearing point of the weighing sensor in the reference coordinate system are transformed to obtain the coordinates of the load-bearing point of the weighing sensor in the sensor coordinate system. The static moment equilibrium equation is established to obtain the projection point of the product's center of mass on the XOY plane of the sensor coordinate system, which is the intersection of the gravity lines of the front / rear vehicles of the product and the XOY plane of the sensor coordinate system. Given that the line of action of gravity passes through the intersection point of the line of action of gravity of the front / rear vehicle of the product and the XOY plane of the sensor coordinate system, and given the direction vector of the line of action of gravity in the sensor coordinate system, use the coordinate transformation matrix to obtain the coordinates of the intersection point of the line of action of gravity of the front / rear vehicle of the product and the XOY plane of the sensor coordinate system in the product coordinate system, as well as the direction vector of the line of action of gravity in the product coordinate system. The analytical expression of the gravity lines of the front / rear vehicles of the product is obtained from the coordinates of the intersection points of the gravity lines of the front / rear vehicles of the product coordinate system and the XOY plane of the sensor coordinate system, as well as the direction vector of the gravity lines of the product coordinate system. The method for synthesizing the center-of-mass coordinates of the product based on the principle of static moment balance, using the center-of-mass coordinates of the product's front vehicle and the product's mass measured by the weighing sensor, and the center-of-mass coordinates of the product's rear vehicle and the product's mass measured by the weighing sensor, is as follows: The product's center of gravity is designated as CG. 前 The product quality measured by the preceding vehicle is M. 前 The rear center of gravity of the product is CG. 后 The product quality measured by the rear vehicle was M. 后 The centroid coordinates of the product are synthesized based on the principle of static moment balance. The method for transforming the coordinate system is as follows: The coordinate system of the laser tracker is defined as the reference coordinate system; the laser tracker is used to determine the relative position of the product under test with respect to the vehicles in front and behind. A reference coordinate system is established by selecting three target seats on the outer perimeter of the front / rear vehicle base as reference points; Using the reference coordinate system as an intermediate bridge, calculate the transformation matrix between the sensor coordinate system and the reference coordinate system of the front / rear vehicle, and the transformation matrix between the reference coordinate system and the product coordinate system of the front / rear vehicle, and then obtain the transformation matrix between the sensor coordinate system and the product coordinate system of the front / rear vehicle. The sensor coordinate system is established as follows: weighing sensors are installed at the four corners of both the front and rear vehicles; the geometric center of the bearing points of the four weighing sensors is taken as the origin O. S X S The axis starts from the origin O S Z points to the midpoint of the line connecting the bearing points of two adjacent load cells. S The axis is perpendicular to the plane containing the load cells of the four load cells and points upwards. S Determined by the right-hand rule, i.e., X S The axis passes through the right palm, with the thumb pointing to Z. S The axis, then the four fingers refer to Y. S axis; The method for establishing the product coordinate system is as follows: origin O p Located at the theoretical apex of the nose cone; X p Axis: Located within the plane of symmetry of the launch vehicle, passing through the origin O. p The normal to the vertical reference plane, pointing towards the rear of the aircraft, is positive; Y p Axis: Located within the spacecraft's plane of symmetry, perpendicular to X. p The axis, pointing towards the back of the fuselage, is positive; Z p Axis: Determined by the right-hand rule, i.e., X p The axis passes through the right palm, with the thumb pointing to Y. p The axis, then the four fingers refer to Z. p The tail end face of the carrier is defined as the vertical reference plane. The method is used to measure the center of mass of large non-cylindrical winged vehicles with long fuselages, large wingspans, and a large distance between the fuselage belly and the fuselage centerline.

2. The method for measuring the center of mass of a large non-cylindrical winged vehicle according to claim 1, characterized in that, The method for calculating the centroid coordinates of the front / rear vehicle of the product is as follows: If the first line of action of gravity intersects with the second line of action of gravity, then the intersection point of the first line of action of gravity and the second line of action of gravity is the coordinate of the center of mass of the front / rear vehicle of the product. If the first and second lines of gravity are skew lines, then the midpoint of the common perpendicular of the first and second lines of gravity in the product coordinate system is the coordinate of the centroid of the front / rear vehicle of the product. If the first and second lines of action of gravity are skew lines, then the process for determining the coordinates of the center of mass of the front / rear vehicle of the product is as follows: Let product coordinate system O P -X P Y P Z P The intersection point of the first line of action of gravity L1 and the common perpendicular is N1. The intersection of the second line of action of gravity and the common perpendicular is N2. Since the common perpendicular is perpendicular to the first line of gravity L1 and the second line of gravity L2 respectively, the coordinates of the two intersection points N1 and N2 satisfy the following equation: ； Where, m 1， n 1， p1 represents the direction vector of the first line of action of gravity, L1; m 2， n 2， p2 represents the direction vector of the second line of action of gravity, L2. The coordinates are the intersection of the first line of action of gravity L1 and the common perpendicular. The coordinates are the intersection of the first line of action of gravity L2 and the common perpendicular. Since the two intersection points N1 and N2 are on the first line of action of gravity L1 and the second line of action of gravity L2 respectively, let ； in, The coordinates of the projection point of the first line of action of gravity on the product's center of mass in the product coordinate system. The coordinates of the projection point of the second line of action of gravity representing the product's center of mass in the product coordinate system. Let S be the slopes of the two lines to be solved; Combining these equations, we obtain a linear equation in two variables k1 and k2. Solving the equation, we can obtain... , The value can be used to determine the coordinates of the foot of the perpendicular, N1. N2 Then the coordinates of the midpoints of line segments N1 and N2 are the coordinates of the centroid; product coordinate system O P -X P Y P Z P The coordinates of the center of gravity of the vehicle before and after the product are: ； in, Product coordinate system O P -X P Y P Z P The coordinates of the center of gravity of the vehicle before and after the product is installed.

3. The method for measuring the center of mass of a large non-cylindrical winged vehicle according to claim 1, characterized in that: The centroid coordinates of the product are: ; Among them, M 前 It is the mass measured by the vehicle in front, M 后 This is the mass measured by the following vehicle; the coordinates of the center of mass of the preceding vehicle in the product coordinate system are: The coordinates of the centroid of the rear vehicle in the product coordinate system are: The coordinates of the center of mass of the arrow body are obtained by solving the simultaneous equations. .

4. A centroid measurement device for a large non-cylindrical winged vehicle, used to implement the centroid measurement method for a large non-cylindrical winged vehicle as described in any one of claims 1-3, characterized in that: It includes a front vehicle for supporting the front end of the product and a rear vehicle for supporting the rear end of the product. Both the front and rear vehicles include a measuring vehicle and a supporting fixture mounted on the measuring vehicle. The measuring vehicle is equipped with a weighing sensor, and the supporting fixture is mounted on the weighing sensor. There are four load cells, which are set at the four corners of the measuring vehicle. The front and rear vehicles are both set on the guide rails and can move closer or further apart along the guide rails. The top of the support fixture is U-shaped to facilitate the positioning of the workpiece being measured. The four corners of the measuring vehicle are also equipped with anti-deviation lifting devices for adjusting the height of the support fixture. The measuring equipment also includes an anti-overturning support and protection platform, which is enclosed in the shape of a fence around the measuring vehicle. Four jacks are installed on its four columns. When the product is installed, the jacks are placed on the bottom of the support fixture. When the product is measured, the top surface of the jacks is lowered and separated from the support fixture.

5. An electronic device, comprising a processor and a memory communicatively connected to the processor and used for storing processor-executable instructions, characterized in that: The processor is used to execute the method for measuring the center of mass of a large non-cylindrical winged vehicle as described in any one of claims 1-3.

6. A server, characterized in that: It includes at least one processor and a memory communicatively connected to the processor, the memory storing instructions executable by the at least one processor, the instructions being executed by the processor to cause the at least one processor to perform the method for measuring the center of mass of a large non-cylindrical winged vehicle as described in any one of claims 1-3.

7. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by the processor, it implements the method for measuring the center of mass of a large non-cylindrical winged vehicle as described in any one of claims 1-3.

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