Multi-parameter quality characteristic measurement method

Abstract

This invention provides a multi-parameter mass characteristic measurement method. After mounting the product under test on a measurement platform, the method allows for the orderly measurement of the mass center of mass, moment of inertia, and centroid. During the measurement process, only the orientation of the product under test needs to be adjusted, effectively improving measurement efficiency. The measurement sequence of this invention is as follows: first, mass, Y-axis center of mass, and Z-axis center of mass are measured; then, the centroid is measured; followed by X-axis moment of inertia, X-axis center of mass, Y-axis moment of inertia, and Z-axis moment of inertia. When measuring the centroid, the method uses the determination of the centroid points of multiple cross-sections along the axial direction of the product under test to fit the centroidal axis of the product under test, resulting in high measurement accuracy.

Description

Technical Field

[0001] This invention relates to a method for measuring quality characteristic parameters, specifically a method for measuring multi-parameter quality characteristics, and belongs to the field of measurement equipment technology. Background Technology

[0002] Mass, center of mass, and moment of inertia are the most important components of mass characteristic parameters. In the aerospace field, mass is directly related to takeoff load, while the center of mass and moment of inertia are related to the ease of flight trajectory control and attitude adjustment. They are important parameters in the flight control of various weapons and equipment. Product mass characteristic parameters can be obtained through equipment measurement.

[0003] Currently, domestic methods for measuring the geometric centroid and moment of inertia mostly employ a split-system measurement approach. This involves measuring the geometric centroid on a geometric integrated measurement system, the center of gravity on a multi-point weighing platform, and the moment of inertia on a torsion pendulum platform. This method is cumbersome and inefficient due to the need for multiple equipment changes, and repeated clamping can easily lead to inconsistent reference standards and large measurement errors. Summary of the Invention

[0004] In view of this, the present invention provides a multi-parameter quality characteristic measurement method, which can sequentially measure multiple quality characteristic parameters with high measurement efficiency.

[0005] Multi-parameter quality characteristic measurement method: Define the axis of the product being measured as the X direction, the horizontal direction as the Z direction when the axis of the product being measured is vertical, and the direction perpendicular to the Z direction in the horizontal plane as the Y direction, and establish a right-hand rectangular coordinate system;

[0006] The product under test is mounted on the measuring platform. Initially, the axis of the product under test is along the vertical direction.

[0007] S1: Measurement of mass, Y-axis centroid, and Z-axis centroid:

[0008] The weighing unit lifts the measuring platform and uses the three-point weighing method to measure the mass, Y-axis centroid, and Z-axis centroid of the product being measured.

[0009] S2: Centroid measurement:

[0010] Multiple laser displacement sensors are arranged at intervals along the height direction of the product being measured, with the measuring end of the laser displacement sensor facing horizontally toward the product being measured. During centroid measurement, the product being measured rotates along its own axis. During the rotation, each laser displacement sensor synchronously collects the displacement signal at the corresponding cross section of the product being measured.

[0011] S3: X-axis rotational inertia measurement:

[0012] The weighing unit is lowered so that the measuring platform rests on the torsion mechanism. The torsion mechanism drives the measuring platform to reciprocate torsion, and the torsion period is measured by the photoelectric period measurement unit. After the measurement is completed, the measuring platform is braked. After the measuring platform is braked, the measuring platform lifting mechanism is activated to lift the measuring platform and move it away from the torsion mechanism.

[0013] S4: X-axis centroid measurement:

[0014] Adjust the posture of the product under test so that the Y direction of the product under test is vertical; lower the lifting mechanism of the measuring platform, use the weighing unit to lift the measuring platform, and use the three-point weighing method to measure the center of mass in the X direction.

[0015] S5: Measurement of rotational inertia in the Y direction:

[0016] The weighing unit is lowered so that the measuring platform rests on the torsion mechanism. The torsion mechanism drives the measuring platform to reciprocate torsion, and the torsion period is measured by the photoelectric period measurement unit. After the measurement is completed, the measuring platform is braked. After the measuring platform is braked, the measuring platform lifting mechanism is activated to lift the measuring platform and move it away from the torsion mechanism.

[0017] S6: Z-axis rotational inertia measurement:

[0018] The product under test is rotated 180° so that its Z-axis is vertical. Then, the lifting mechanism of the measuring platform is lowered so that the measuring platform rests on the torsion mechanism. The torsion mechanism drives the measuring platform to reciprocate torsion, and the torsion period is measured by the photoelectric period measurement unit. After the measurement is completed, the measuring platform is braked. After the measuring platform is braked, the lifting mechanism of the measuring platform is started to lift the measuring platform.

[0019] As a preferred embodiment of the present invention, a rotationally symmetric comparative measurement method is used for centroid measurement, based on which:

[0020] In S1, when measuring the centroid in the Y and Z directions:

[0021] After completing one measurement of the Y-axis and Z-axis centroids, the product under test is spun 180 degrees, and then the Y-axis and Z-axis centroids are measured a second time using the three-point weighing method through the weighing unit.

[0022] In S4, when determining the centroid in the X direction:

[0023] After completing one measurement, adjust the posture of the product under test so that the axis of the product under test is still in the horizontal direction, but the positions of the two ends of the axis are interchanged, so as to perform a second measurement of the center of mass in the X direction.

[0024] In a preferred embodiment of the present invention, the second measurement of the X-axis centroid is performed after the measurement of the Z-axis moment of inertia is completed.

[0025] As a preferred embodiment of the present invention, the centroids in the Y and Z directions of the product under test are measured using the centroid rotation method. Based on this:

[0026] In S1, when measuring the centroid in the Y and Z directions:

[0027] The product under test rotates 360° along its own axis. During the rotation, the centroid measurement data is automatically collected every time the set angle is rotated.

[0028] As a preferred embodiment of the present invention, when the centroid rotation method is used to measure the Y-axis centroid and Z-axis centroid of the product under test, the centroid is measured simultaneously during the Y-axis and Z-axis centroid measurements.

[0029] As a preferred embodiment of the present invention, when braking the measuring platform, friction braking is adopted, in which the measuring platform is stopped from swinging by applying braking friction force to the measuring platform.

[0030] In a preferred embodiment of the present invention, during the braking process, the applied braking friction force is continuously reduced, causing the measuring platform to stop swinging and return to its original position.

[0031] As a preferred embodiment of the present invention, when performing mass measurement, a correction for air buoyancy is made based on direct weighing. The correction method is as follows:

[0032] m=C f ·m0

[0033] C f =(1-ρ a / ρ m ) / (1-ρ a / ρ)

[0034] Where: m is the corrected mass of the tested product; C f ρ is the air buoyancy correction factor; m0 is the measured mass of the product, and ρ is the mass of the measured product. a ρ is the density of air. m ρ is the density of the standard weight; ρ is the density of the product being tested.

[0035] In a preferred embodiment of the present invention, the photoelectric period measurement unit includes a photoelectric sensor and a pendulum. When the measurement platform reciprocates, it drives the pendulum to swing back and forth within the detection area of ​​the photoelectric sensor. The photoelectric sensor receives a trigger signal, thereby measuring the period of the reciprocating motion through the photoelectric sensor.

[0036] Beneficial effects:

[0037] (1) After the product to be measured is installed on the measurement platform, the mass center, moment of inertia and centroid can be measured in an orderly manner according to the steps of the measurement method of the present invention. During the measurement process, only the posture of the product to be measured needs to be adjusted, which can effectively improve the measurement efficiency.

[0038] (2) When performing centroid measurement, the measurement method of the present invention uses the determination of the centroid points of multiple cross sections of the product under test along the axial direction to fit the centroid axis of the product under test, which results in high measurement accuracy. After the centroid axis is determined, the intersection of the centroid axis and the cross section where the axial centroid is located is the centroid.

[0039] (3) When performing centroid measurement, in order to further improve the measurement accuracy, rotational symmetry measurement is adopted, that is, the product being measured is rotated 180 degrees and then measured twice. The influence of tooling processing, tooling positioning, levelness and other factors can be eliminated by two measurements.

[0040] (4) When measuring the centroid in the Y and Z directions, the centroid rotation method can also be used to further improve the measurement accuracy.

[0041] (5) In the measurement method of the present invention, after the moment of inertia measurement is completed, the measuring platform is stopped from swinging by friction braking, which is simple and reliable; and the measuring platform can be stopped from swinging and returned to its original position by continuously reducing the braking friction. Attached Figure Description

[0042] Figure 1 This is a flowchart of the multi-parameter quality characteristic measurement method of the present invention;

[0043] Figure 2 A schematic diagram of the measuring device capable of implementing this measurement method;

[0044] Figure 3 This is a schematic diagram illustrating the principle of centroid measurement.

[0045] Figure 4 This is a flowchart illustrating the specific measurement steps.

[0046] Among them: 1-product under test, 2-main frame, 3-measuring platform lifting mechanism, 4-tooling inner frame, 5-torsion braking mechanism, 6-measuring platform, 7-torsion bar, 8-weighing unit, 9-air-float turntable, 10-torsion drive unit, 11-tooling outer frame, 12-rotary bearing, 13-pin, 14-rotation drive unit, 15-laser displacement sensor. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0048] Example 1:

[0049] This embodiment provides a multi-parameter mass characteristic measurement method, which can systematically measure all the measurement data required for calculating mass, triaxial center of mass, triaxial moment of inertia and centroid, with high measurement efficiency.

[0050] like Figure 1 As shown, the axis of the product being measured is defined as the X-direction. When the axis of the product being measured is vertical, the horizontal direction is defined as the Z-direction. The direction perpendicular to the Z-direction in the horizontal plane is defined as the Y-direction. A rectangular coordinate system is established based on the right-hand rectangular coordinate system.

[0051] The product under test is mounted on the measuring platform using a measuring fixture. Initially, the product's axis is vertical. The measuring fixture can change the product's orientation; three weighing units with lifting functions are located below the measuring platform.

[0052] S1: Measurement of mass, Y-axis centroid, and Z-axis centroid:

[0053] The weighing unit lifts the measuring platform and uses the three-point weighing method to measure the mass, the Y-axis centroid, and the Z-axis centroid.

[0054] S2: Centroid measurement:

[0055] Multiple laser displacement sensors are arranged at intervals along the height direction of the product being tested, with the measuring ends of the laser displacement sensors facing horizontally toward the product being tested. During centroid measurement, the product being tested rotates along its own axis. During the rotation, each laser displacement sensor synchronously collects the displacement signal at the corresponding cross-section of the product being tested, thereby obtaining the geometric centroid of each cross-section. The centroid axis of the product being tested is obtained by least-squares fitting of all geometric centroids.

[0056] S3: X-axis rotational inertia measurement:

[0057] Lower the weighing unit so that the measuring platform rests on the torsion mechanism. The torsion mechanism drives the measuring platform to reciprocate torsion, and the torsion period is measured by the photoelectric period measurement unit. After the measurement is completed, brake the measuring platform. After the measuring platform is braked, start the measuring platform lifting mechanism to lift the measuring platform and make the measuring platform leave the torsion mechanism.

[0058] S4: X-axis centroid measurement:

[0059] Adjust the posture of the product under test so that the Y direction of the product is vertical; lower the lifting mechanism of the measuring platform, use the weighing unit to lift the measuring platform, and use the three-point weighing method to measure the center of mass in the X direction.

[0060] S5: Measurement of rotational inertia in the Y direction:

[0061] Lower the weighing unit so that the measuring platform rests on the torsion mechanism. The torsion mechanism drives the measuring platform to reciprocate torsion, and the torsion period is measured by the photoelectric period measurement unit. After the measurement is completed, brake the measuring platform. After the measuring platform is braked, start the measuring platform lifting mechanism to lift the measuring platform and move it away from the torsion mechanism.

[0062] S6: Z-axis rotational inertia measurement:

[0063] The product under test is rotated 180° so that its Z-axis is vertical. Then, the lifting mechanism of the measuring platform is lowered so that the measuring platform rests on the torsion mechanism. The torsion mechanism drives the measuring platform to reciprocate torsion, and the torsion period is measured by the photoelectric period measurement unit. After the measurement is completed, the measuring platform is braked. After the measuring platform is braked, the lifting mechanism of the measuring platform is started to lift the measuring platform.

[0064] Example 2:

[0065] This embodiment provides a quality characteristic measuring device capable of implementing the above-described measurement method, such as... Figure 2 As shown, the mass characteristic measuring device includes: a measuring platform assembly, a mass center of mass measuring unit, a moment of inertia measuring unit, a centroid measuring unit, and measuring fixtures.

[0066] The measuring platform assembly includes: main frame 2, measuring platform 6, measuring platform lifting mechanism 3, and measuring and control unit;

[0067] The mass and center of mass measurement unit measures mass and center of mass based on the three-point weighing principle. Based on this, the mass and center of mass measurement unit includes three weighing units 8, and each weighing unit 8 includes a weighing sensor and a weighing sensor lifting mechanism.

[0068] The centroid measurement unit includes: an automatic rotational motion structure and a laser displacement measurement unit;

[0069] The moment of inertia measurement unit includes: an air-floating turntable 9, a torsion pendulum drive unit 10, a torsion bar 7, a photoelectric period measurement unit, and a torsion pendulum braking mechanism;

[0070] The measuring fixture is used to mount the product under test 1 and can change the posture of the product under test 1 when performing center of mass measurement and moment of inertia measurement.

[0071] For the measuring device, the vertical direction is defined as the X direction, the horizontal direction as the Z direction, and the direction perpendicular to the Z direction in the horizontal plane as the Y direction. A rectangular coordinate system is established based on the right-hand rectangular coordinate system. That is, when the product being measured 1 is placed vertically (i.e., the axis is along the vertical direction), its Z and Y directions are consistent with the Z and Y directions in the coordinate system of the measuring device.

[0072] The measuring fixture includes an outer frame 11 and an inner frame 4. The inner frame 4 is connected to the outer frame 11 via a pin 13 arranged along the Z direction. The inner frame 4 can rotate relative to the outer frame 11 about the axial direction of the pin 13.

[0073] like Figure 3 As shown, the main frame 2 is the mounting base for the entire device, the measuring platform 6 is located on the main frame 2, and the measuring fixture for clamping the product 1 to be measured is placed on the measuring platform 6. Specifically, the outer frame 11 of the fixture is fixedly installed on the measuring platform 6, and the product 1 to be measured is supported on the inner frame 4 of the fixture.

[0074] A measuring platform lifting mechanism 3 is provided between the main frame 2 and the measuring platform 6. In this example, the measuring platform 6 is a disc-shaped structure. Three measuring platform lifting mechanisms 3 are evenly distributed around the measuring platform 6 on the circumference below the measuring platform 6 for raising and lowering the measuring platform 6. In this example, the measuring platform lifting mechanism 3 is a cylinder. The fixed end of the cylinder is fixed to the surface of the main frame 2, and the telescopic end is vertically upward (not connected to the measuring platform 6). It is used to lift the measuring platform 6 after contacting it.

[0075] The mass and centroid measurement unit is used to measure the mass and centroid of the product 1 being measured. In this example, a three-point weighing method is used for mass and centroid measurement. Based on this, three weighing units 8 are evenly distributed circumferentially between the main frame 2 and the measuring platform 6. In the weighing unit 8, the weighing sensors are mounted on the main frame 2 via a weighing sensor lifting mechanism (each weighing sensor corresponds to one weighing sensor lifting mechanism). In this example, the weighing sensor lifting mechanism uses a cylinder, with the fixed end of the cylinder fixed to the surface of the main frame 2, and the weighing sensors mounted on the telescopic end of the cylinder. During mass measurement, the measuring platform lifting mechanism 3 descends to a position where it is not in contact with the measuring platform 6; the weighing sensors are lifted by the weighing sensor lifting mechanism to contact the measuring platform 6. At this time, the measuring platform 6 is supported only on the three weighing sensors, thus the product 1 being measured, clamped on the measuring fixture, is weighed using the three-point weighing method through the three weighing sensors. During mass measurement, the measuring platform 6 is supported by three load cells. The load cells and the measuring platform 6 have a relatively fixed and accurate geometric positional relationship. The mass of the measuring fixture and the product under test 1 is entirely supported by the three load cells. The measuring fixture and the product under test 1 also have a definite positional relationship with the measuring platform 6. The mass of the product under test 1 is calculated based on the readings of the three load cells before and after loading the product under test 1.

[0076] When the density of the product being measured (1) differs significantly from the agreed density (i.e., the density of the standard weights used to calibrate the weighing sensor), a correction for air buoyancy is required based on the direct weighing to improve measurement accuracy. The correction method is as follows:

[0077] m=Cf ·(m2- m1)

[0078] C f =(1-ρ a / ρ m ) / (1-ρ a / ρ)

[0079] Where: m is the corrected mass of the tested product 1, in kg; C f ρ is the air buoyancy correction factor; m1 is the mass of the measuring fixture obtained by direct weighing using the three-point weighing method; m2 is the mass of the product 1 to be measured after clamping it onto the measuring fixture and obtaining it by direct weighing using the three-point weighing method; ρ a For air density, take 1.2 kg / m³. 3 ;ρ m The density of the standard weight is 8000 kg / m³ in this example. 3 ρ is the density of the tested product 1, in kg / m³. 3 .

[0080] The measurement of the center of mass of the tested product 1 includes the measurement of its Y-axis center of mass, Z-axis center of mass, and X-axis center of mass (i.e., axial center of mass) in the coordinate system of the tested product. The center of mass measurement also adopts the three-point weighing method. In order to improve the measurement accuracy, a rotational symmetry comparison measurement is used when measuring the center of mass in each direction. That is, after completing the first measurement of the Y-axis and Z-axis center of mass, the tested product is rotated 180 degrees, and then the Y-axis and Z-axis center of mass are measured a second time using the three-point weighing method through the weighing unit. The average value of the measurement data on both sides is used to calculate the Y-axis and Z-axis center of mass.

[0081] The measurement of the axial center of mass (i.e., the X-axis center of mass) is based on the principle of the three-point weighing method. When the product 1 to be measured is rotated to an axially horizontal position through the inner frame 4 of the tooling, the axial center of mass is directly measured twice, in the forward direction and in the reverse direction, and the direct measurement of the axial center of mass is converted into the relative offset of the two axial centers of mass, so as to calculate the distance of the axial center of mass from the rotation axis.

[0082] The centroid data of the tested product relative to the axis of rotation is obtained by calculating the data from two measurements, which can eliminate the influence of factors such as tooling processing, tooling positioning, and levelness.

[0083] Furthermore, the Y-axis and Z-axis centroids of the tested product 1 can also be measured using the centroid rotation method. Based on this, a rotary bearing 12 is installed on the inner frame 4 of the fixture. The tested product 1 is connected to the rotary bearing 12 via a transition fixture, and is thus supported on the inner frame 4 of the fixture. The tested product 1 and the rotary bearing 12 are coaxial. The rotation drive unit 14 drives the transition fixture, causing the tested product 1 to rotate around its own axis. The rotary bearing 12, the transition fixture, and the rotation drive unit 14 together constitute an automatic rotational motion structure, which is shared with the centroid measurement unit.

[0084] When measuring the Y-axis and Z-axis centroids of the tested product 1 using the centroid rotation method, the rotating bearing 12 drives the tested product 1 to rotate. During the rotation, the Y-axis and Z-axis centroid measurement data are dynamically collected, that is, measurement data is collected once for each set rotation angle. In this example, measurement data is collected once for each 1° rotation. After the tested product 1 rotates one full circle (i.e., 360°), the measurement results at multiple angles can theoretically obtain a series of centroid coordinate values ​​around the rotation axis (i.e., the central axis of the rotating bearing 12). The curve formed by this series of centroid coordinate values ​​is theoretically a circle with radius r centered at the rotation axis (let's call it point c), where r is the distance from the centroid to the rotation axis.

[0085] The centroid measurement unit is used to measure the centroid of the product being measured (1). By measuring the centroid and combining the results with the centroid measurement, the lateral deviation of the centroid of the product being measured (i.e., the deviation of the centroid from the centroidal axis) can be obtained. Figure 3 As shown, the centroid measurement unit includes an automatic rotational motion structure (i.e., the aforementioned rotary bearing 12, adapter fixture, and rotational drive unit 14) and a laser displacement measurement unit. The automatic rotational motion structure drives the product under test 1 to rotate around its axis. The laser displacement measurement unit consists of multiple laser displacement sensors 15 spaced apart along the height direction on the inner frame 4 of the fixture, which perform cross-sectional measurements. In this example, three laser displacement sensors 15 are spaced apart along the height direction on the inner frame 4 of the fixture. Each laser displacement sensor 15 is horizontally positioned with its measuring end horizontally facing the product under test 1. When the length of the product under test 1 is large, a displacement sensor bracket can be connected to the inner frame 4 of the fixture to ensure that the multiple laser displacement sensors 15 are spaced apart along the height direction of the product under test 1. The height position of each laser displacement sensor 15 on the inner frame 4 of the fixture is adjustable, and each laser displacement sensor 15 is horizontally extendable, thus allowing for free adjustment according to the shape of the product under test 1.

[0086] The automatic rotating motion structure drives the tested product 1 to rotate one revolution. The time for one revolution is pre-calibrated. The rotation angle of the tested product 1 can be calculated from the rotation time. Combined with the displacement signals at each cross section of the tested product 1 synchronously collected by the laser displacement measurement unit, the data required for centroidal axis fitting can be obtained. Then, the centroidal axis is obtained by fitting using the least squares method. The centroidal coordinates of the cross section where the centroidal axis and the X-axis centroid are located can be obtained through the intersection of the centroidal axis and the cross section where the X-axis centroid is located. Furthermore, the deviation of the X-axis centroid from the centroidal axis, i.e., the lateral deviation of the centroid, can also be obtained.

[0087] The moment of inertia measurement unit is used to measure the moment of inertia of the tested product 1 in three directions (XYZ directions). A torsion bar 7 is installed inside the main frame 2, coaxially positioned below the measurement platform 6. An air-bearing turntable 9 is coaxially positioned between the measurement platform 6 and the torsion bar 7. The air-bearing turntable 9 uses a pneumatic bearing; only an air film exists between the stator and rotor of the pneumatic bearing, thus enabling frictionless rotation of the rotor relative to the stator. The stator of the pneumatic bearing is fixed to the main frame 2, the rotor is coaxially fixed to the top of the torsion bar 7, and the bottom of the torsion bar 7 is fixed to the main frame 2. The measurement platform 6 is placed on the rotor of the pneumatic bearing (there is no connection between the two; it is only placed on the rotor). The torsion bar 7 is a flexible rod, allowing the rotor of the pneumatic bearing to only twist. The torsion drive unit 10 is used to push the measuring platform 6 to rotate at an initial angle, so that the torsion bar 7 is in a torsional state. The torsion bar 7 then drives the air-bearing turntable 9 and the measuring platform 6 to reciprocate. The torsion period of the measuring platform 6 is measured by the photoelectric period measurement unit, thereby obtaining the moment of inertia in the rotational direction. The photoelectric period measurement unit includes a photoelectric sensor and a pendulum needle. The pendulum needle is mounted on the lower surface of the measuring platform 6, and the photoelectric sensor is fixed to the main frame 2. When the measuring platform 6 reciprocates, it drives the pendulum needle to swing back and forth within the detection area of ​​the photoelectric sensor. The photoelectric sensor receives a trigger signal, and thus the oscillation period is measured.

[0088] When the moment of inertia needs to be measured, the measuring platform 6 is lowered onto the air-floating turntable 9. At this time, the measuring platform 6 is not in contact with the measuring platform lifting mechanism 3 and the weighing unit 8. The torsion drive unit 10 includes a push cylinder and a push rod or push block set on the lower surface of the measuring platform 6. By pushing the push cylinder to push the push rod or push block, the measuring platform 6 is twisted at an initial angle of about 2°, thereby putting the torsion bar 7 in a torsion state. After the push cylinder is de-aired, its push rod quickly returns to its original position, and the measuring platform 6 then swings back and forth at a slower speed due to the load of the moment of inertia, thus completing one drive action.

[0089] The inner frame 4 of the tooling drives the tested product 1 to rotate, thereby changing the posture of the tested product 1 and measuring the rotational inertia in different directions. For example, when the axis of the tested product 1 is vertically upward (i.e., the X-axis of the tested product 1 is coaxial with the rotary bearing 12), the rotational inertia in the X direction is measured; when the Y-axis of the tested product 1 is vertically upward, the rotational inertia in the Y direction is measured; and when the Z-axis of the tested product 1 is vertically upward, the rotational inertia in the Z direction is measured.

[0090] When measuring the center of mass, the measuring platform 6 is lifted by the measuring platform lifting mechanism 3 so that it does not come into contact with the rotor of the air-float turntable 9.

[0091] The torsional braking mechanism is used to brake the measuring platform 6 after the rotational inertia measurement is completed, so that the measuring platform 6 stops twisting. In this example, the torsional braking mechanism includes a brake cylinder and a friction plate disposed at the end of the extension and retraction end of the brake cylinder; the cylinder body end of the brake cylinder is fixed on the main frame 2, the extension and retraction end is vertically upward, and the end of the extension and retraction end is provided with a friction plate; when braking is required after the measurement is completed, the extension and retraction end of the brake cylinder is controlled to extend so that the friction plate at its end contacts the bottom surface of the measuring platform 6, thereby achieving braking by friction.

[0092] When the measuring platform stops swinging, due to the presence of friction, the measuring platform 6 has not yet returned to its original position. At this time, the friction is gradually reduced to allow it to continue to slide and the amplitude of friction to continue to decay. The way to reduce the friction is to continuously reduce the cylinder thrust. The reduction of cylinder thrust is accomplished by the slow release of pressurized gas inside the cylinder.

[0093] The measurement and control unit located inside the main frame 2 is used to receive monitoring data from each sensor (including the weighing sensor and each laser displacement sensor) in the measuring device, and to control the measuring platform lifting mechanism 3, the weighing sensor lifting mechanism, the automatic rotation motion structure, the torsion drive unit 10 and the torsion braking mechanism.

[0094] In summary, in this example, measurement platform 6 has the following states during the measurement process:

[0095] (1) The state of the installation of measuring fixture and the product under test 1: the lifting mechanism of the three weighing sensors falls down, the lifting mechanism of the three measuring platforms 3 rises up to lift the measuring platform 6, and the measuring platform 6 is separated from the air-float turntable 9;

[0096] (2) Mass center of mass measurement status: The lifting mechanism 3 of the three measuring platforms is lowered, and the lifting mechanism of the three weighing sensors is raised to support the measuring platform 6. The measuring platform 6 is separated from the air-float turntable 9 and is only supported by three weighing points. When measuring the center of mass in the Y and Z directions, the product 1 being measured is installed vertically. When measuring the center of mass in the X direction, the inner frame 4 of the tooling is rotated 90 degrees before measurement. At this time, the axis of the product 1 being measured is along the horizontal direction.

[0097] (3) Rotational inertia measurement state: The lifting mechanisms 3 of the three measuring platforms and the lifting mechanisms of the three weighing sensors are all lowered, and the measuring platform 6 is placed on the air-floating turntable 9. It can rotate with the air-floating turntable 9 and the rotational inertia is measured by the torsion bar method.

[0098] (4) Placement state: When no measurement is required, i.e. when the power and air supply to the device are cut off, the lifting mechanisms 3 of the three measuring platforms and the lifting mechanisms of the three weighing sensors all fall down, and the measuring platform 6 is supported on the air-float turntable 9.

[0099] This measuring device can achieve the full measurement of mass, triaxial center of mass, triaxial moment of inertia and centroid in a single clamping operation; without considering the product hoisting time, the entire measurement process takes about 30 minutes.

[0100] like Figure 4 As shown, the entire measurement process is divided into two stages: skin measurement (i.e., without the product under test 1 installed) and "skin + product" measurement (i.e. with the product under test 1 installed). The measurement process is the same in both stages. The measurement process after installing the product under test 1 will be described in detail below.

[0101] When installing the product under test 1, first start the measuring platform lifting mechanism 3, and use the measuring platform lifting mechanism 3 to lift the measuring platform 6; the product under test 1 and the tooling inner frame 4 are both in a vertical self-rotation state of 0°.

[0102] After the product under test 1 is installed, the weighing unit 8 is first lifted to the position where it contacts the measuring platform 6, and then the measuring platform lifting mechanism 3 is lowered. At this time, the weighing unit 8 can be used for weighing. The rotating drive unit 14 drives the rotating bearing 12 to rotate, causing the product under test 1 to rotate around its axis for one revolution, so as to measure the center of mass in the Y and Z directions.

[0103] During the Y-axis and Z-axis centroid measurement process, that is, during the rotation of the product under test 1 around its axis, the measurement is performed by the laser displacement measurement unit. Thus, the centroid measurement can be performed simultaneously with the Y-axis and Z-axis centroid measurements, that is, the centroid measurement and the Y-axis and Z-axis centroid measurements are performed synchronously, resulting in high measurement efficiency.

[0104] After the Y-axis and Z-axis center of mass measurements are completed, the X-axis moment of inertia is measured: at this time, the weighing unit 8 is lowered so that the measuring platform 6 rests on the rotor of the air-float turntable 9; the torsion pendulum drive unit 10 is activated to make the measuring platform 6 reciprocate torsion pendulum to measure the X-axis moment of inertia; after the X-axis moment of inertia measurement is completed, the measuring platform 6 is braked by the torsion pendulum braking mechanism. After the measuring platform 6 is braked, the measuring platform lifting mechanism 3 is activated to lift the measuring platform 6.

[0105] Then, the first measurement of the X-axis center of mass (i.e., the forward measurement) is performed: the inner frame 4 of the tooling is adjusted to a horizontal state, that is, the axis of the product being measured 1 is horizontal (and the Y-axis of the product being measured 1 is vertical); the weighing unit 8 is lifted to a position in contact with the measuring platform 6, and then the measuring platform lifting mechanism 3 is lowered; at this time, the weighing unit 8 can be used to weigh, thereby performing the forward measurement of the X-axis center of mass.

[0106] After the first X-axis center of mass measurement, the Y-axis moment of inertia is measured: the weighing unit 8 is lowered so that the measuring platform 6 rests on the rotor of the air-bearing turntable 9, and the torsion drive unit 10 is activated to make the measuring platform 6 reciprocate torsion to measure the Y-axis moment of inertia; after the Y-axis moment of inertia measurement is completed, the measuring platform 6 is braked by the torsion braking mechanism. After the measuring platform 6 is braked, the measuring platform lifting mechanism 3 is activated to lift the measuring platform 6.

[0107] Then, the Z-axis rotational inertia is measured: the test product 1 is controlled to rotate 180° by an automatic rotational motion structure, so that the Z-axis of the test product 1 coincides with the axial direction of the rotary bearing 12; then, the measuring platform lifting mechanism 3 is lowered, so that the measuring platform 6 rests on the rotor of the air-bearing turntable 9; the torsion pendulum drive unit 10 is activated, so that the measuring platform 6 reciprocates torsion pendulum to measure the Z-axis rotational inertia; after the Z-axis rotational inertia measurement is completed, the measuring platform 6 is braked by the torsion pendulum braking mechanism. After the measuring platform 6 is braked, the measuring platform lifting mechanism 3 is activated to lift the measuring platform 6.

[0108] Then, perform the second measurement of the X-axis center of mass (i.e., reverse measurement): rotate the inner frame 4 of the fixture 180° around the pin 13 at the connection point with the outer frame 11 of the fixture. At this time, the axis of the product 1 being measured is still in the horizontal direction, but the positions of the two ends of the axis are interchanged; lower the lifting mechanism 3 of the measuring platform so that the measuring platform 6 falls on the air-float turntable 9; then use the weighing unit 8 to lift the measuring platform 6 so that it does not contact the air-float turntable 9; at this time, the weighing unit 8 can be used to weigh (perform the second measurement of the X-axis center of mass). After the measurement is completed, lower the weighing unit 8 so that the measuring platform 6 falls on the air-float turntable 9 and is repositioned. Then, start the lifting mechanism 3 of the measuring platform to lift the measuring platform 6.

[0109] Finally, the state is reset.

[0110] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for measuring multi-parameter quality characteristics, characterized in that: Define the axis of the product being measured as the X-direction. When the axis of the product being measured is vertical, the horizontal direction is the Z-direction. The direction perpendicular to the Z-direction in the horizontal plane is the Y-direction. Establish a right-handed rectangular coordinate system. The product under test is mounted on the measuring platform. Initially, the axis of the product under test is along the vertical direction. S1: Measurement of mass, Y-axis centroid, and Z-axis centroid: The weighing unit lifts the measuring platform and uses the three-point weighing method to measure the mass, Y-axis centroid, and Z-axis centroid of the product being measured. S2: Centroid measurement: Multiple laser displacement sensors with their measuring ends horizontally facing the product are arranged at intervals along the height direction of the product being tested. The product being tested rotates along its own axis, and each laser displacement sensor synchronously collects the displacement signal at the corresponding cross section of the product being tested. The geometric centroid of each cross section is obtained from this. All geometric centroids are fitted with least squares to obtain the centroidal axis of the product being tested. After the centroidal axis is determined, the intersection of the centroidal axis and the cross section where the axial centroid is located is the centroid. S3: X-axis rotational inertia measurement: The weighing unit is lowered so that the measuring platform rests on the torsion mechanism. The torsion mechanism drives the measuring platform to reciprocate torsion, and the photoelectric period measurement unit measures the torsion period. S4: X-axis centroid measurement: Adjust the posture of the product under test so that the Y direction of the product under test is vertical; lower the lifting mechanism of the measuring platform, use the weighing unit to lift the measuring platform, and use the three-point weighing method to measure the center of mass in the X direction. S5: Measurement of rotational inertia in the Y direction: The weighing unit is lowered so that the measuring platform rests on the torsion mechanism. The torsion mechanism drives the measuring platform to reciprocate torsion, and the photoelectric period measurement unit measures the torsion period. S6: Z-axis rotational inertia measurement: The product under test is rotated 180° so that the Z-axis of the product under test is vertical; then the lifting mechanism of the measuring platform is lowered so that the measuring platform is placed on the torsion mechanism. The torsion mechanism drives the measuring platform to reciprocate torsion, and the photoelectric period measurement unit measures the torsion period. During the above measurement process, the measuring platform is braked after each measurement of the moment of inertia is completed; after the measuring platform is braked, the measuring platform lifting mechanism is activated to lift the measuring platform and move it away from the torsion mechanism. When measuring the centroid, a rotationally symmetric comparative measurement method is used, based on the following: In S1, when measuring the centroid in the Y and Z directions: After completing one measurement of the Y-axis and Z-axis centroids, the product under test is spun 180 degrees, and then the Y-axis and Z-axis centroids are measured a second time using the three-point weighing method through the weighing unit. In S4, when performing X-axis centroid measurement: After completing one measurement, adjust the posture of the product under test so that the axis of the product under test is still in the horizontal direction, but the positions of the two ends of the axis are interchanged, so as to perform a second measurement of the center of mass in the X direction. The second measurement of the center of mass in the X direction is performed after the measurement of the moment of inertia in the Z direction is completed; When braking the measuring platform, friction braking is used. The measuring platform is stopped from swinging by applying braking friction force. During braking, the applied braking friction force is continuously reduced to stop the measuring platform from swinging and return it to its original position. The torsional braking mechanism includes a brake cylinder and a friction plate disposed at the extension end of the brake cylinder. The friction force is reduced by continuously reducing the thrust of the brake cylinder. The reduction of the thrust of the brake cylinder is accomplished by the slow release of pressurized gas inside the cylinder.

2. The multi-parameter quality characteristic measurement method of claim 1, wherein: The centroids in the Y and Z directions of the tested product are measured using the centroid rotation method. Based on this: In S1, when measuring the centroid in the Y and Z directions: The product under test rotates 360° along its own axis. During the rotation, the centroid measurement data is automatically collected every time the set angle is rotated.

3. The multi-parameter quality characteristic measurement method of claim 2, wherein: When using the centroid rotation method to measure the Y-axis centroid and Z-axis centroid of the product being measured, the centroid is measured simultaneously during the Y-axis and Z-axis centroid measurements.

4. The multi-parameter quality characteristic measurement method according to any one of claims 1 to 3, characterized in that: When performing mass measurement, a correction for air buoyancy is applied based on direct weighing. The correction method is as follows: m = C f • m0 C f =(1-ρ a / r m ) / ( 1-p a / p) wherein: m is the corrected mass of the product under test; is the air buoyancy correction factor; m0 is the measured mass of the product under test, p a is the air density; p m is the density of the standard weight; p is the density of the product under test.

5. The multi-parameter quality characteristic measurement method according to any one of claims 1-3, characterized in that: The photoelectric period measurement unit includes a photoelectric sensor and a pendulum. When the measurement platform reciprocates, it drives the pendulum to swing back and forth within the detection area of ​​the photoelectric sensor. The photoelectric sensor receives a trigger signal, thereby measuring the period of the reciprocating motion.

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