Three-dimensional measuring device for centroid position of object

Abstract

The invention discloses an object mass center position three-dimensional measuring device and method, and relates to the technical field of high-precision mass metering, the object mass center position three-dimensional measuring device comprises a triangular weighing bridge mechanism, a cushion block, two scales and two weighing sensors, the triangular weighing bridge mechanism is positioned and matched with a trapezoidal platform by a rectangular pyramid bottom T-shaped support through a pin shaft, and the triangular weighing bridge mechanism is positioned and matched with the trapezoidal platform through a pin shaft; the rectangular pyramid bottom right opening support column and the rectangular pyramid bottom left opening support column are respectively positioned and matched with the isosceles V-shaped groove trapezoidal platform through two pin shafts; a to-be-measured object is placed on the upper surface of the trapezoidal platform and close to the center of the rectangular pyramid bottom T-shaped supporting column, the rectangular pyramid bottom T-shaped supporting column of the triangular weighing bridge mechanism is placed on the cushion block, and the difference value of the weighing sensors when the triangular weighing bridge mechanism measures the cushion block to be horizontal and the numerical value of the weighing sensors when the triangular weighing bridge mechanism inclines are measured. And calculating to obtain the three-dimensional centroid position coordinates of the object to be measured. The problems that a traditional multi-point weighing centroid measurement method is low in measurement precision and has measurement position errors are solved.

Description

Technical Field

[0001] The present invention can be applied in the field of high-precision mass measurement technology, and specifically is a three-dimensional measurement device for the centroid position of an object. Background Art

[0002] In the field of mass metrology, the mass characteristic parameters of an object, including mass, center of mass, moment of inertia, etc., are all physical parameters that describe its dynamic performance. Among them, center of mass measurement is a method to calculate the center position of the mass distribution of an object or system. It is widely used in aerospace, military industry, transportation, precision instruments and other fields. However, it is difficult to quickly and accurately measure the center of mass position of an object, so it is necessary to establish a standard center of mass measurement device and method for value traceability.

[0003] At present, the center of mass measurement mainly adopts the multi-point support weighing method. Among them, the bilateral center of mass measurement method based on the weighing bridge only needs one sensor, but there is a gap between the measured object and the weighing bridge and the center of mass height can only be obtained in one direction. Although the three-point support center of mass measurement method can obtain the three-dimensional center of mass position of the object, it requires at least three weighing sensors.

[0004] The multi-point support weighing method is mainly based on establishing a static moment balance equation to calculate the center of mass position of the object, and its measurement accuracy is mainly determined by the coordinate position accuracy and the weighing sensor accuracy. For large-mass heterogeneous objects, a large-range weighing sensor will be selected to meet the measurement requirements, but the accuracy of the large-range weighing sensor is generally not high and there are also measurement errors in the positions of the object and each support point. Therefore, the overall center of mass measurement accuracy of the object is low and cannot meet the measurement accuracy requirements in the field of high-precision mass measurement technology. In order to solve the above-mentioned problems of measurement accuracy and measurement position error, the present invention provides a three-dimensional measurement device and method for the center of mass position of an object based on the multi-point support weighing method. Summary of the invention

[0005] In order to solve the above-mentioned problems of measurement accuracy and measurement position error, the present invention provides a three-dimensional measurement device and method for the center of mass position of an object based on a multi-point support weighing method.

[0006] The invention comprises a triangular weighing bridge mechanism, a cushion block and two weighing sensors, wherein the cushion block and the two weighing sensors are located in the same horizontal plane, the triangular weighing bridge mechanism comprises a tetrahedral pyramid T-shaped support, a tetrahedral pyramid right open support, a tetrahedral pyramid left open support and a trapezoidal platform, the tetrahedral pyramid T-shaped support of the triangular weighing bridge mechanism is arranged on the cushion block, the tetrahedral pyramid right open support and the tetrahedral pyramid left open support are respectively placed on the two weighing sensors, the trapezoidal platform and the pointed cone of the tetrahedral pyramid T-shaped support are positioned on the same vertical line, the bottom side of the trapezoidal platform is parallel to the connecting line of the pointed cones of the tetrahedral pyramid right open support and the tetrahedral pyramid left open support and are in the same plane, the object to be measured is placed on the upper surface of the isosceles V-groove trapezoidal platform close to the center position of the tetrahedral pyramid T-shaped support and close to the main support, so as to measure the weighing difference of the cushion block by the triangular weighing bridge mechanism and the value of the weighing sensor when the triangular weighing bridge mechanism is tilted, and the three-dimensional centroid position coordinates of the object to be measured are calculated.

[0007] Furthermore, the weighing sensor mechanism includes a weighing sensor and an embedded weighing pan.

[0008] Furthermore, the trapezoidal platform is an isosceles V-groove trapezoidal platform, which is matched with the T-shaped pillar at the bottom of a four-sided pyramid through a pin, and the right open pillar at the bottom of the four-sided pyramid and the left open pillar at the bottom of the four-sided pyramid are positioned and matched with the long bottom side of the isosceles V-groove trapezoidal platform through the pin respectively.

[0009] A method for three-dimensional measurement of the centroid of an object comprises the following steps:

[0010] Step 1: Obtain the air buoyancy density ρ of the experimental environment a , the mass of the object being measured is m c and volume V;

[0011] Step 2: calibrate the triangular weighing bridge mechanism, take the bottom vertebra of the four-sided pyramid T-shaped support as the origin, take the vertical direction from the origin to the line connecting the right open support and the bottom sharp cone of the left open support of the four-sided pyramid as the X-axis, and take the line segment direction of the line connecting the right open support and the bottom sharp cone of the left open support of the four-sided pyramid as the Y-axis to establish a three-coordinate measurement system;

[0012] Step 3: Place the triangular weighing bridge mechanism at the center of the pad and the two weighing sensor mechanism scales, and adjust the position of the weighing sensor mechanism to be at the same height as the pad;

[0013] Step 4: Place the object on the triangular weighing bridge mechanism and close to the center of the T-shaped support at the bottom of the quadrangular pyramid, and read the readings of the two weighing sensor mechanisms m. 2 、m 3 According to the principle of static moment balance combined with the measured data, the coordinates of the center of mass (xc ,y c ) can be obtained by the following formula:

[0014]

[0015] In the formula, m c is the mass of the object being measured, V is the volume of the object being measured, m 2 、m 3 are the readings of the two weighing sensor mechanisms, l is the vertical distance from the coordinate origin to the weighing sensor mechanism in the X direction, l 2 is the vertical distance from the origin of the coordinate system to one of the weighing sensor mechanisms in the Y direction, ρ a is the buoyancy density of air;

[0016] Step 5: When calculating the center of mass of the object in the Z direction, take out the pad to tilt the triangular weighing bridge mechanism by an angle of θ. According to the static moment equilibrium equation, the center of mass coordinates z of the object in the Z direction relative to the origin are c It can be obtained by the following formula:

[0017]

[0018] In the formula, m' 2 、m' 3 They are the readings of the two load cell mechanisms when the weighing bridge is tilted;

[0019] Step 6: Based on the measurement data and coordinate conversion, the three-dimensional coordinates of the center of mass of the object being measured relative to itself can be calculated by the following formula:

[0020]

[0021] In the formula, (x c ,y c , z c ) is the three-dimensional centroid position of the object relative to the coordinate origin, a is the distance from the contact surface of the tetrahedral T-shaped support (4) and the object to the origin in the X direction, r is the vertical distance from the origin to the bottom of the object in the Y direction, and c is the distance from the origin to the upper surface of the isosceles V-groove trapezoidal platform (7) in the Z direction.

[0022] Furthermore, a three-dimensional coordinate measuring machine is used to obtain the distance a from the contact surface of the T-shaped support at the bottom of the quadrangular pyramid and the object to the origin in the X direction, the vertical distance l from the origin to the connecting line of the right open support at the bottom of the quadrangular pyramid and the left open support at the bottom of the quadrangular pyramid, and the vertical distance l from the origin to the bottom of the left open support at the bottom of the quadrangular pyramid in the Y direction. 2 , the vertical distance c from the origin to the upper surface of the isosceles V-groove trapezoidal platform in the Z direction; the vertical distance r from the origin to the bottom of the object to be measured in the Y direction.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention transforms a general weighing bridge and adopts the three-point support tilt measurement principle. During measurement, the object only needs to be fixed in one position. The three-dimensional coordinates of the object's center of mass can be obtained by reading the readings of the weighing sensor mechanism when the weighing bridge is horizontal and tilted. Compared with the traditional bilateral measurement method of the weighing bridge, the measurement error caused by the need to move the object is eliminated, the measurement steps are simplified, and the measurement efficiency is improved.

[0025] (2) The present invention can obtain the three-dimensional coordinates of the center of mass of an object by introducing two weighing sensors. Compared with the traditional multi-point support weighing method, it reduces the accuracy error caused by the introduction of a large-range weighing sensor and saves tooling costs.

[0026] (3) The present invention takes into account the measurement error caused by air buoyancy during the measurement process, further improving the accuracy of object center of mass measurement. It is low in cost and safe and convenient to use. It can not only measure objects of conventional shapes, but also perform three-dimensional center of mass position measurement on large-mass heterogeneous objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0028] Figure 2 It is a front view of the present invention and a schematic diagram of measuring the centroid coordinates in the Y direction and the Z direction in the horizontal plane of the measuring device;

[0029] Figure 3 is a top view of the present invention;

[0030] Figure 4 It is a side view of the present invention and a schematic diagram of measuring the centroid coordinates in the X direction and the Z direction in the horizontal plane of the measuring device;

[0031] Figure 5 It is a side view of the tilted state of the present invention and a schematic diagram of measuring the centroid coordinates of the measuring device in the X direction and the Z direction. DETAILED DESCRIPTION

[0032] In order to more clearly express the technical solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings.

[0033] The three-dimensional measurement device of the object center of mass in this embodiment is composed of a pad, two weighing sensor mechanisms, and a triangular weighing bridge mechanism; the weighing sensor mechanism is composed of a scale pan and a weighing sensor; the triangular weighing bridge mechanism is composed of a T-shaped support with a quadrangular pyramid base, an isosceles V-groove trapezoidal platform, a right open support with a quadrangular pyramid base, and a left open support with a quadrangular pyramid base.

[0034] The tetrahedral pyramid bottom T-shaped support of the triangular weighing bridge mechanism is placed on a cushion block, and the tetrahedral pyramid bottom right open support and the tetrahedral pyramid bottom left open support are respectively placed at the center of the weighing pans of the two weighing sensor mechanisms.

[0035] Specifically, Figure 2 , Figure 3 , Figure 4 As shown, the pad is at the same horizontal height as the weighing sensor mechanism, and the triangular weighing bridge mechanism is placed on it. It has a total length of 220mm, a total length of the upper base of 60mm, and a total length of the lower base of 320mm. It is made of 304 stainless steel. The load-bearing platform is an isosceles V-groove trapezoidal platform, which can be used to place heterogeneous objects such as spheres and prevent the objects being measured from falling.

[0036] Specifically, Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown, the isosceles V-groove trapezoidal platform in the triangular weighing bridge mechanism is matched with the tetrahedral pyramid T-shaped pillar through three pins, and the isosceles V-groove trapezoidal platform and the sharp cones of the tetrahedral pyramid T-shaped pillar are positioned on the same vertical line; the right open pillar of the tetrahedral pyramid and the left open pillar of the tetrahedral pyramid are matched with the two corners of the bottom side of the isosceles V-groove trapezoidal platform through two pins respectively, and the bottom side of the isosceles V-groove trapezoidal platform is parallel to the line connecting the sharp cones of the right open pillar of the tetrahedral pyramid and the left open pillar of the tetrahedral pyramid and are in the same plane.

[0037] Specifically, a measurement method using the above-mentioned object centroid position three-dimensional measurement device comprises the following steps:

[0038] Step 1: Calibrate the load cell; Use standard weights to calibrate the load cell;

[0039] Step 2: Obtain the air buoyancy density ρa of the experimental environment through an air buoyancy density measuring device;

[0040] Step 3: Calibrate the triangular weighing bridge mechanism;

[0041] Specifically, Figure 2 , Figure 4As shown, a three-coordinate measurement system is established with the tip of the bottom of the tetrahedral pyramid T-shaped support as the origin, the vertical direction from the origin to the line connecting the right open support and the left open support at the bottom of the tetrahedral pyramid as the X-axis, and the line segment direction of the line connecting the right open support and the left open support at the bottom of the tetrahedral pyramid as the Y-axis. A three-coordinate measuring machine is used to obtain the distance a from the contact surface of the tetrahedral pyramid T-shaped support and the object to the origin in the X direction, the vertical distance l from the origin to the line connecting the right open support and the left open support at the bottom of the tetrahedral pyramid in the X direction, the vertical distance l2 from the origin to the tip of the bottom of the left open support at the tetrahedral pyramid in the Y direction, and the vertical distance c from the origin to the upper surface of the isosceles V-shaped groove trapezoidal platform in the Z direction;

[0042] Step 4: Obtain the mass mc, volume V, and vertical distance r from the origin to the bottom of the object in the Y direction;

[0043] Step 5: Place the triangular weighing bridge mechanism at the center of the pad and the two weighing sensor mechanism scales, adjust the weighing sensor mechanism position to make it at the same height as the pad, and adjust the instrument to zero;

[0044] Step 6: Place the object on the triangular weighing bridge mechanism, close to the center of the T-shaped support at the bottom of the quadrangular pyramid, and read the readings m2 and m3 of the two weighing sensor mechanisms. Based on the principle of static moment balance and the measured data, the centroid coordinates (xc, yc) of the object on the OXY plane relative to the origin can be calculated by the following formula:

[0045]

[0046] Where mc is the mass of the object being measured, V is the volume of the object being measured, m2 and m3 are the readings of the two weighing sensor mechanisms, l is the vertical distance from the origin of the coordinate system to the weighing sensor mechanism in the X direction, l2 is the vertical distance from the origin of the coordinate system to one of the weighing sensor mechanisms in the Y direction, and ρa is the air buoyancy density;

[0047] When calculating the center of mass of the object in the Z direction, take out the pad to tilt the weighing bridge by an angle of θ. According to the static moment balance equation and the measurement data output by the two weighing sensor mechanisms at this time, the center of mass coordinate zc of the object under test in the Z direction relative to the origin can be calculated by the following formula:

[0048]

[0049] In the formula, m'2 and m'3 are the readings of the two weighing sensor mechanisms when the weighing bridge is tilted;

[0050] Furthermore, based on the measurement data and coordinate transformation, the three-dimensional coordinates of the center of mass of the object under test relative to itself can be calculated by the following formula:

[0051]

[0052] Where (xc, yc, zc) is the three-dimensional centroid position of the object relative to the coordinate origin, a is the distance from the contact surface between the T-shaped support at the bottom of the tetrahedral pyramid and the object to the origin in the X direction, r is the vertical distance from the origin to the bottom of the object in the Y direction, and c is the distance from the origin to the upper surface of the isosceles V-groove trapezoidal platform in the Z direction.

[0053] In this embodiment, the object to be measured is set as a sphere, wherein the radius r = 35mm, the mass mc = 1479.0879g, the volume V = 187.03cm3, the air buoyancy density ρa = 1.2173kg / m3, the weighing bridge dimensions are l = 200.031mm; l2 = 149.967mm; a = 9.998mm; θ = 14.48°; c = 114.805mm, and the measured values ​​are m2 = 164.78g; m3 = 167.19g

[0054]

[0055] After tilting the weighing bridge, m'2 = 15.65g; m'3 = 29.94g

[0056]

[0057] Finally, the coordinates of the center of mass of the sphere are:

[0058]

[0059] The above only describes in detail the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention, and various changes should be included in the protection scope of the present invention.

Claims

1. A three-dimensional measurement device for the centroid position of an object, characterized in that: The invention comprises a triangular weighing bridge mechanism, a cushion block and two weighing sensors, wherein the cushion block and the two weighing sensors are located in the same horizontal plane, the triangular weighing bridge mechanism comprises a tetrahedral pyramid T-shaped support, a tetrahedral pyramid right open support, a tetrahedral pyramid left open support and a trapezoidal platform, the tetrahedral pyramid T-shaped support of the triangular weighing bridge mechanism is arranged on the cushion block, the tetrahedral pyramid right open support and the tetrahedral pyramid left open support are respectively placed on the two weighing sensors, the trapezoidal platform and the pointed cone of the tetrahedral pyramid T-shaped support are positioned on the same vertical line, the bottom side of the trapezoidal platform is parallel to the connecting line of the pointed cones of the tetrahedral pyramid right open support and the tetrahedral pyramid left open support and are in the same plane, the object to be measured is placed on the upper surface of the isosceles V-groove trapezoidal platform close to the center of the tetrahedral pyramid T-shaped support and close to the main support so as to measure the weighing difference of the cushion block by the triangular weighing bridge mechanism and the value of the weighing sensor when the triangular weighing bridge mechanism is tilted, and the three-dimensional centroid position coordinates of the object to be measured are calculated.

2. The device for three-dimensionally measuring the centroid position of an object according to claim 1, characterized in that: The weighing sensor mechanism includes a weighing sensor and an embedded weighing pan.

3. The device for three-dimensionally measuring the centroid position of an object according to claim 1, characterized in that: The trapezoidal platform is an isosceles V-groove trapezoidal platform, which is matched with the T-shaped pillar at the bottom of a quadrangular pyramid through a pin shaft, and the right open pillar at the bottom of the quadrangular pyramid and the left open pillar at the bottom of the quadrangular pyramid are positioned and matched with the long bottom side of the isosceles V-groove trapezoidal platform through a pin shaft.

4. A method for three-dimensional measurement of the centroid of an object, used to implement the three-dimensional measurement device for the centroid position of an object as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Obtain the air buoyancy density ρ of the experimental environment a , the mass of the object being measured is m c and volume V; Step 2: calibrate the triangular weighing bridge mechanism, take the bottom vertebra of the four-sided pyramid T-shaped support as the origin, take the vertical direction from the origin to the line connecting the right open support and the bottom sharp cone of the left open support of the four-sided pyramid as the X-axis, and take the line segment direction of the line connecting the right open support and the bottom sharp cone of the left open support of the four-sided pyramid as the Y-axis to establish a three-coordinate measurement system; Step 3: Place the triangular weighing bridge mechanism at the center of the pad and the two weighing sensor mechanism scales, and adjust the position of the weighing sensor mechanism to be at the same height as the pad; Step 4: Place the object on the triangular weighing bridge mechanism and close to the center of the T-shaped support at the bottom of the quadrangular pyramid. Read the readings m2 and m3 of the two weighing sensor mechanisms. According to the principle of static moment balance and the measured data, the centroid coordinates (x c ,y c ) can be obtained by the following formula: In the formula, m c is the mass of the object to be measured, V is the volume of the object to be measured, m2 and m3 are the readings of the two weighing sensor mechanisms, l is the vertical distance from the origin of the coordinate system to the weighing sensor mechanism in the X direction, l2 is the vertical distance from the origin of the coordinate system to one of the weighing sensor mechanisms in the Y direction, ρ a is the buoyancy density of air; Step 5: When calculating the center of mass of the object in the Z direction, take out the pad to tilt the triangular weighing bridge mechanism by an angle of θ. According to the static moment equilibrium equation, the center of mass coordinates z of the object in the Z direction relative to the origin are c It can be obtained by the following formula: In the formula, m'2 and m'3 are the readings of the two weighing sensor mechanisms when the weighing bridge is tilted; Step 6: Based on the measurement data and coordinate conversion, the three-dimensional coordinates of the center of mass of the object being measured relative to itself can be calculated by the following formula: In the formula, (x c ,y c , z c ) is the three-dimensional centroid position of the object relative to the coordinate origin, a is the distance from the contact surface of the tetrahedral T-shaped support (4) and the object to the origin in the X direction, r is the vertical distance from the origin to the bottom of the object in the Y direction, and c is the distance from the origin to the upper surface of the isosceles V-groove trapezoidal platform (7) in the Z direction.

5. The method for three-dimensional measurement of the centroid of an object according to claim 4, characterized in that: Use a three-dimensional coordinate measuring machine to obtain the distance a in the X direction from the contact surface between the T-shaped support at the bottom of the quadrangular pyramid and the object, the vertical distance l in the X direction from the origin to the connecting line of the right open support at the bottom of the quadrangular pyramid and the left open support at the bottom of the quadrangular pyramid, the vertical distance l2 in the Y direction from the origin to the tip of the bottom of the left open support at the bottom of the quadrangular pyramid, the vertical distance c from the origin to the upper surface of the isosceles V-groove trapezoidal platform in the Z direction, and the vertical distance r from the origin to the bottom of the object to be measured in the Y direction.

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