A simple measurement device and method for aircraft mass characteristics

Abstract

The present invention relates to the technical field of aircraft mass characteristic measurement, and discloses a simple aircraft mass characteristic measurement device and measurement method. The measurement device includes a horizontally arranged measurement platform, on which two support mechanisms are installed. The support mechanisms include a base and two hydraulic telescopic rods vertically fixed to the base. A horizontally arranged crossbeam is installed on the top of the two hydraulic telescopic rods. The outer wall of the crossbeam is provided with a plurality of sleeves. A universal joint is fixed to the bottom of the outer wall of the sleeve, and a suspension rope is provided on the universal joint. The present invention suspends the aircraft above the measurement platform, and uses the equilibrium equation of the moment taken at the suspension point to calculate the position of the center of mass relative to the suspension point, thereby determining the position of the center of mass of the aircraft; then, the moment of inertia of the aircraft is measured using the double cycloid method. The operation is simple, the method is reliable, and it can be widely used to measure the mass characteristics of aircraft.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft mass characteristic measurement, and in particular to a simple aircraft mass characteristic measurement device and a measurement method. Background Art

[0002] Aircraft mass characteristics refer to properties such as its mass, center of mass, and moment of inertia. In engineering applications, these characteristics are an important basis for aircraft design and a key control parameter. They can be accurately measured using specialized measuring equipment, but this equipment is generally expensive and requires specialized measurement tooling for different aircraft. This results in complex and costly measurement methods. Summary of the Invention

[0003] In response to the above problems, the present invention provides a simple device and method for measuring the mass characteristics of an aircraft. By suspending the aircraft above a measurement platform, the balance equation of the moment taken at the suspension point can be used to calculate the position of the center of mass relative to the suspension point, thereby determining the position of the center of mass of the aircraft; then, the moment of inertia of the aircraft is measured using the double cycloid method. The operation is simple, the method is reliable, and it can be widely used to measure the mass characteristics of aircraft.

[0004] To solve the above technical problems, the present invention provides a simple device for measuring aircraft mass characteristics, comprising a horizontally arranged measuring platform, characterized in that: two support mechanisms are mounted on the measuring platform, the support mechanisms comprising a base and two hydraulic telescopic rods vertically fixed to the base, a horizontally arranged crossbeam is mounted on the top of the two hydraulic telescopic rods, the outer wall of the crossbeam is provided with a plurality of sleeves, the bottom of the outer wall of the sleeve is fixed with a universal joint, and the universal joint is provided with a suspension rope;

[0005] The sleeve is provided with a threaded hole perpendicular to the sleeve axis, and a tightening bolt is provided in the threaded hole; a guide rail groove is opened on the measuring platform, and a plurality of threaded holes are provided at the bottom of the guide rail groove along the length direction of the guide rail groove, and the base of the support mechanism is installed in the guide rail groove by bolts;

[0006] The measuring device performs the following method steps:

[0007] S1. Select the hanging point A directly above the aircraft's central axis, select points B and D on the horizontal reference line on the side of the aircraft's fuselage, and measure the projection distance L between points B and D on the aircraft's central axis. BD ;

[0008] S2. Use the lifting rope to lift the aircraft at point A and measure the height h of points B and D relative to the measuring platform. B 、h D , calculate the tilt angle of the aircraft through the formula;

[0009] S3. Add a counterweight to point E on the aircraft to level it, and measure the projected distance L between point A and point E. AE , calculate the position of the center of mass O through the equilibrium equation;

[0010] S4. Establish a spatial rectangular coordinate system and measure the moment of inertia I of the aircraft around the z-axis using the double cycloid method. z ;

[0011] S5. Measure two types of vibration periods T x1 and T x2 , calculate the moment of inertia I around the x-axis x ;

[0012] S6. Measure the moment of inertia I of the aircraft around the y-axis by hanging it sideways y ;

[0013] In actual measurement, I is corrected according to the parallel axis theorem of moment of inertia z and I y , we get the moment of inertia I through the center of mass z″ and I y″ .

[0014] 2. The simplified measurement device for aircraft mass characteristics according to claim 1, wherein the suspension rope is a steel cable, and the load-bearing capacity of a single suspension rope is more than three times the weight of the aircraft.

[0015] 3. The simplified measurement device for aircraft mass characteristics according to claim 1, wherein the universal joint is fixed to the lower hanging point of the aircraft, and the length of the hanging rope meets the requirements for moment of inertia measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the structure of the simple measurement device for aircraft mass characteristics in Examples 1 and 2;

[0017] Figure 2 This is a schematic diagram of measuring the center of mass of the aircraft when the aircraft is tilted and hung at point A in Example 1;

[0018] Figure 3 It is an enlarged schematic diagram of the local F in Example 1;

[0019] Figure 4 This is a schematic diagram of the aircraft in Example 1, where the aircraft is suspended at point A and a counterweight is added to measure the center of mass of the aircraft;

[0020] Figure 5 Schematic diagram of the principle of measuring the moment of inertia of the aircraft around the z-axis in Example 1 or 2;

[0021] Figure 6This is a schematic diagram of the first type of vibration principle for measuring the moment of inertia of the aircraft around the x-axis in Example 1;

[0022] Figure 7 This is a schematic diagram of the second type of vibration principle for measuring the moment of inertia of the aircraft around the x-axis in Example 1;

[0023] Figure 8 Schematic diagram of the principle of measuring the moment of inertia of the aircraft around the y-axis in Example 1 or 2;

[0024] Figure 9 This is a flow chart for adjusting the aircraft mass parameters in Example 1 or 2;

[0025] Among them, 1. Measuring platform; 2. Hydraulic telescopic rod; 3. Beam; 4. Sleeve; 5. Universal joint; 6. Guide rail groove. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0027] Example 1:

[0028] See also Figure 1 A simple device for measuring the mass characteristics of an aircraft includes a horizontally arranged measuring platform 1, on which two supporting mechanisms are installed. The supporting mechanisms include a base and two hydraulic telescopic rods 2 vertically fixed to the base. A horizontally arranged crossbeam 3 is installed on the top of the two hydraulic telescopic rods 2. The outer wall of the crossbeam 3 is sleeved with multiple sleeves 4. A universal joint 5 is fixed to the bottom of the outer wall of the sleeve 4, and a lifting rope is provided on the universal joint 5.

[0029] In this embodiment, the crossbeam 3 and the hydraulic telescopic rods 2 of the two supporting mechanisms form a gate-shaped structure. A lifting rope is installed at the bottom of the sleeve 4 on the outer wall of the crossbeam 3 through a universal joint 5 to suspend the aircraft, and the aircraft is lifted by extending the hydraulic telescopic rods 2, which is simple to operate and low in cost.

[0030] A threaded hole perpendicular to the axis of the sleeve 4 is provided on the sleeve 4, and a tightening bolt is provided in the threaded hole. The sleeve 4 is sleeved on the beam 3, and the position of the sleeve 4 on the beam 3 can be adjusted to facilitate keeping the lifting rope under the hanging point in a vertical direction; the sleeve 4 with a determined position is tightened and fixed on the beam 3 by tightening the bolt. When it needs to be adjusted again, the position of the sleeve 4 can be adjusted by unscrewing the tightening bolt.

[0031] A guide rail groove 6 is provided on the measuring platform 1, and a plurality of threaded holes are provided at the bottom of the guide rail groove 6 along the length direction of the guide rail groove 6. The base of the support mechanism is installed in the guide rail groove 6 by bolts; the base is installed on the measuring platform 1 through the guide rail groove 6, and the base can slide in the guide rail groove 6 to adjust the distance between the two support mechanisms, and then the base is fixed with bolts. It can adapt to the simple measurement of the mass characteristics of aircraft of different sizes. Before measurement, it is sufficient to select the beam 3 that matches the distance between the support mechanisms.

[0032] The simplified measurement method for aircraft mass characteristics in this embodiment is as follows:

[0033] S1. Select the hanging point A directly above the aircraft's centerline. Select points B and D on the horizontal reference line on the side of the aircraft's fuselage. Points B and D should be located in front of and behind point A, respectively. Measure the projected distance L between points B and D on the aircraft's centerline. BD ;

[0034] S2. Use the lifting rope to lift the aircraft at point A, so that the aircraft is tilted and suspended above the measuring platform 1. Figure 2 and Figure 3 , measure the height h of points B and D relative to the measuring platform 1 B 、h D , and use the following formula to obtain the tilt angle α of the aircraft:

[0035]

[0036] S3. Keep the hanging position unchanged and add counterweight at point E on the aircraft to make the aircraft level. Figure 4 , that is, h B =h D , measure the projected distance between point A and point E on the aircraft's central axis, and use the equilibrium equation of the moment taken at the hanging point A to obtain the distance Δx between the center of mass O and point A along the aircraft's central axis:

[0037]

[0038] where x E 、x A are the coordinate positions of point E and point A on the x-axis, m is the mass of the aircraft, m p is the mass of the counterweight;

[0039] From this, we can get the vertical distance Δz of the center of mass O below the hanging point A:

[0040]

[0041] Obtain the position of the center of mass O based on the distance between the center of mass O and the lifting point A in the vertical direction and the center axis direction;

[0042] S4. Establish a spatial rectangular coordinate system oxyz, with the center of mass O of the aircraft as the coordinate origin, the straight line passing through the center of mass O and parallel to the central axis as the x-axis, and the straight line passing through the center of mass O and perpendicular to the plane containing the horizontal reference line of the aircraft's side as the z-axis. Use two ropes to hang the aircraft horizontally, with the bottom of the aircraft facing up and upside down. Make sure the two ropes are parallel to the z-axis and located in the xoz plane, and the distances between the two ropes and the z-axis are equal. Measure the period T of the aircraft's oscillation around the z-axis in the horizontal plane. z , the deflection angle is about 5°, such as Figure 5 As shown, calculate the moment of inertia I of the aircraft around the z axis z :

[0043]

[0044] where R x1 is the distance from the rope to the z-axis, H z It is the vertical distance from the center of mass O of the aircraft to the line connecting the upper hanging point;

[0045] S5. Keep measuring I z The hanging attitude is used to measure the period of two types of vibration of the aircraft:

[0046] The first type of vibration is when the aircraft swings from side to side in a plane perpendicular to its y-axis, similar to a swing. Figure 6 As shown in the figure, during the swing process, the center of mass O of the aircraft and the lower hanging point of the aircraft rope pass through the vertical equilibrium position at the same time, and swing in the other direction at the same time. The measured vibration period is T x1 ;

[0047] The second type of vibration is the vibration of the aircraft from one wing up and down to the other wing up and down. While the aircraft vibrates in the plane perpendicular to its y-axis, the aircraft's suspension rope also oscillates relative to the upper suspension point of the suspension rope, which is equivalent to the two wings yawing up and down with the x-axis as the axis, such as Figure 7 As shown; the characteristic is that during the vibration process, the center of mass of the aircraft and the lower hanging point of the rope pass through the vertical equilibrium position at the same time, but the movement directions of the center of mass and the lower hanging point are opposite. The period T of this type of vibration is measured x2 (swing, yaw angle is about 5°), the moment of inertia I of the aircraft around the x-axis can be calculated x :

[0048]

[0049] where h x H is the vertical distance from the center of mass O to the lower hanging point, x It is the vertical distance from the center of mass O of the aircraft to the line connecting the upper hanging point;

[0050] S6. Hang the aircraft sideways on two ropes. The two ropes are parallel to the aircraft's y-axis and are equidistant from the y-axis. Therefore, the upper and lower four connection points of the ropes are all located in the aircraft's xoy plane, as shown in the figure. Figure 8 As shown; the period T of the aircraft's self-oscillation around the y-axis in the horizontal plane is measured y (yaw angle is about 5°), calculate the moment of inertia I of the aircraft around the y-axis y :

[0051]

[0052] where R x2 is the distance from the rope to the y-axis, H y It is the vertical distance from the center of mass O of the aircraft to the line connecting the upper hanging point.

[0053] The sling rope in this embodiment is a steel cable. Its upper end is secured to the beam frame via a universal joint 5, and its lower end is secured to the aircraft's lower suspension point via a universal joint 5. The sling rope should also be sufficiently strong, with a single rope carrying capacity of at least three times the aircraft's weight. The sling rope should be of sufficient length, particularly several times the aircraft's length when measuring moment of inertia, to ensure accurate measurement results.

[0054] The measurement and adjustment of the aircraft's mass center position and moment of inertia is to firmly install the test equipment and the required counterweights on the aircraft in accordance with the requirements, and then adjust them so that the aircraft's mass parameters meet the requirements. Figure 9 shown.

[0055] In order to better complete the mass adjustment task of the aircraft, the installation positions of various devices and counterweights should be preliminarily determined based on the mass parameters of the aircraft and the internal space, and a mass adjustment plan should be formulated. Then, according to the assembly adjustment plan, the final assembly and adjustment are divided into two steps:

[0056] The first step is to install and fix the test equipment with installation orientation requirements, and measure the actual installation orientation of these equipment;

[0057] The second step is to preliminarily install other equipment and counterweights according to the assembly plan and measure the mass parameters of the aircraft. After adjustment to meet the requirements, these equipment and counterweights are fixed.

[0058] Example 2

[0059] like Figure 5 and Figure 6 , based on Example 1, the moment of inertia I of the aircraft measured when the two suspension ropes are parallel to the z-axis or the y-axis and are equidistant from the z-axis or the y-axis z or I yHowever, this is often not possible in actual measurements. Sometimes it is difficult to find a position where the frame can be installed to clamp the front and rear fuselages at an equal distance in front and behind the center of mass of the aircraft. Therefore, the positions of the front and rear frames have to be asymmetrical with respect to the center of mass, so that the z-axis or y-axis represented by the center line of the two suspension ropes differs by L from the z′ axis or y′ axis passing through the actual center of mass of the aircraft. z or L y Or, because there is a difference between the actual center of mass of the aircraft and the theoretical center of mass during the deployment process, the z' axis or y' axis represented by the center line of the two suspension ropes and the z axis or y axis passing through the actual center of mass of the aircraft differ by L z or L y ,. What is measured at this time is the moment of inertia I of the aircraft about the z-axis or y-axis represented by the center line passing through the two ropes z or I y , rather than the moment of inertia I about the z′ or y′ axis passing through the center of mass of the vehicle z ' or I y '. According to theoretical mechanics, the moment of inertia of any rigid body about the axis passing through the center of mass has a minimum value. The above method actually overestimates the moment of inertia of the aircraft, so it needs to be corrected. According to the parallel axis theorem of moment of inertia, z or I y The calculation formula is modified as follows to obtain the moment of inertia I about the z′ axis or y′ axis passing through the actual center of mass of the aircraft z ' or I y 'as follows:

[0060]

[0061] The other parts of this embodiment are the same as those of embodiment 1 and will not be described in detail here.

[0062] The above are embodiments of the present invention. The above embodiments and the specific parameters therein are only for the purpose of clearly describing the invention verification process and are not intended to limit the scope of patent protection of the present invention. The scope of patent protection of the present invention shall still be subject to the claims. Any equivalent structural changes made by using the contents of the description and drawings of the present invention shall also be included in the scope of protection of the present invention.

Claims

1. A simple device for measuring the mass characteristics of an aircraft, comprising a horizontally arranged measuring platform (1), characterized in that: Two supporting mechanisms are installed on the measuring platform (1), and the supporting mechanisms include a base and two hydraulic telescopic rods (2) vertically fixed to the base, a horizontally arranged crossbeam (3) is installed on the top of the two hydraulic telescopic rods (2), a plurality of sleeves (4) are sleeved on the outer wall of the crossbeam (3), a universal joint (5) is fixed on the bottom of the outer wall of the sleeve (4), and a lifting rope is provided on the universal joint (5); The sleeve (4) is provided with a threaded hole perpendicular to the axial direction of the sleeve (4), and a tightening bolt is provided in the threaded hole; A guide rail groove (6) is provided on the measuring platform (1), a plurality of threaded holes are provided at the bottom of the guide rail groove (6) along the length direction of the guide rail groove (6), and the base of the support mechanism is installed in the guide rail groove (6) by means of bolts; The measuring device performs the following method steps: S1. Select the hanging point A directly above the aircraft's central axis, select points B and D on the horizontal reference line on the side of the aircraft's fuselage, and measure the projection distance L between points B and D on the aircraft's central axis. BD ; S2. Use the lifting rope to lift the aircraft at point A and measure the height h of points B and D relative to the measuring platform. B 、h D , calculate the tilt angle of the aircraft through the formula; S3. Add a counterweight to point E on the aircraft to level it, and measure the projected distance L between point A and point E. AE , calculate the position of the center of mass O through the equilibrium equation; S4. Establish a spatial rectangular coordinate system and measure the moment of inertia I of the aircraft around the z-axis using the double cycloid method. z ; where R x1 is the distance from the rope to the z-axis, H z It is the vertical distance from the center of mass O of the aircraft to the line connecting the upper hanging point; S5. Measure two types of vibration periods T x1 and T x2 , calculate the moment of inertia I around the x-axis x ; where h x H is the vertical distance from the center of mass O to the lower hanging point, x It is the vertical distance from the center of mass O of the aircraft to the line connecting the upper hanging point; S6. Measure the moment of inertia I of the aircraft around the y-axis by hanging it sideways y ; where R x2 is the distance from the rope to the y-axis, H y It is the vertical distance from the center of mass O of the aircraft to the line connecting the upper hanging point. In actual measurement, I is corrected according to the parallel axis theorem of moment of inertia. z and I y , we get the moment of inertia I through the center of mass z′ and I y′ .

2. The simplified measurement device for aircraft mass characteristics according to claim 1, characterized in that: The lifting rope is a steel cable, and the carrying capacity of a single lifting rope is more than three times the weight of the aircraft.

3. The simplified measurement device for aircraft mass characteristics according to claim 1, characterized in that: The universal joint (5) is fixed to the lower hanging point of the aircraft, and the length of the hanging rope meets the requirements for moment of inertia measurement.

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