Multi-point weighing device for centroid measurement with high-precision repeatable positioning

Abstract

The present invention discloses a multi-point weighing device for centroid measurement with a high-precision repeatable positioning function. The device includes a base, a support device, a measuring platform, and multiple weighing mechanisms. The support device is fixedly mounted on the top surface of the base, and the upper surface of the support device is provided with multiple ball sockets. The upper surface of the measuring platform is used to fix the object to be measured, and the measuring platform is provided with multiple positioning members, one end of the positioning member is a ball head, and the other end is a flange. The ball heads protrude from the lower surface of the measuring platform, and the ball heads correspond to the ball sockets one by one. Multiple weighing mechanisms are arranged between the top surface of the base and the lower surface of the measuring platform. The weighing mechanisms include a weighing sensor and a lifting device for lifting the weighing sensor. The device can position the measuring platform through the cooperation of the multiple ball heads and ball sockets. Each time the center of mass of an object is measured, the measuring platform is always lifted from the same determined position, thereby improving the accuracy of the center of mass measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of centroid measurement, and in particular relates to a multi-point weighing device for centroid measurement with a high-precision repeated positioning function. Background Art

[0002] There are two main types of center of mass measurement methods: static and dynamic. Static methods include the suspension method and multi-point weighing, while dynamic methods generally include the compound pendulum method, moment of inertia method, and rotational balance method. The multi-point weighing method is widely used due to its simplicity, convenience, low cost, and suitability for measuring large products such as rockets, satellites, missiles, and submarines.

[0003] The multi-point weighing method uses the readings of three or four load cells and their relative positional relationship to calculate the center of mass of the product under test. In the measuring state, the measuring platform, to which the test piece is attached, is lifted by the load cells until it is separated from the support device and supported by the load cells. In the non-measuring state, the measuring platform falls back onto the support device. Therefore, the measuring platform frequently switches between the lifted and unlifted states. To improve the accuracy of center of mass measurement, the measuring platform should always be lifted from a defined position so that the test piece and the load cells maintain a defined position during the measuring state. However, no domestic or international literature currently describes a positioning design with high-precision, repeatable positioning capabilities for multi-point weighing devices. Summary of the Invention

[0004] In view of this, the present invention provides a multi-point weighing device for centroid measurement with a high-precision repeated positioning function, which can perform high-precision repeated positioning of the measuring platform, so that there is a definite position between the workpiece to be measured on the measuring platform and the weighing sensor, thereby improving the accuracy of the centroid measurement.

[0005] The present invention adopts the following technical solutions:

[0006] A multi-point weighing device for centroid measurement with high-precision repeatable positioning function, including a base, a support device, a measuring platform and multiple weighing mechanisms;

[0007] The support device is fixedly mounted on the top surface of the base, and a plurality of ball sockets are arranged on the upper surface of the support device;

[0008] The upper surface of the measuring platform is used for fixing and mounting the workpiece to be measured, and a plurality of positioning members are provided on the measuring platform, one end of the positioning member is a ball head, and the other end is a flange, the ball head protrudes from the lower plane of the measuring platform, and the ball head corresponds to the ball socket one by one;

[0009] A plurality of weighing mechanisms are arranged between the top surface of the base and the lower plane of the measuring platform; the weighing mechanism includes a weighing sensor and a lifting device for lifting the weighing sensor;

[0010] In the non-measurement state, the measuring platform is supported on the upper end of the supporting device by the cooperation of multiple ball heads and multiple ball sockets; in the measuring state, the lifting device can lift the weighing sensor, and the lifted weighing sensor can lift the measuring platform to a state where the ball head is disengaged from the ball socket, and the weight of the measuring platform and the workpiece to be measured fixedly mounted on the measuring platform is entirely borne by the weighing sensor.

[0011] Furthermore, the measuring platform is provided with a stepped hole for installing the positioning member;

[0012] The positioning member is fixedly mounted on the step hole;

[0013] A gasket is sandwiched between the lower end surface of the flange of the positioning member and the step surface of the step hole, which is used to adjust the contact state between the ball head and the ball socket in the non-measuring state until a critical state is reached: the upper plane of the support device is in contact with the lower plane of the measuring platform, and the circumferential surfaces of multiple ball sockets are in full contact with the circumferential surfaces of the corresponding ball heads.

[0014] Furthermore, a top screw hole is provided on the flange of the positioning member;

[0015] The measuring platform is provided with a stepped hole for installing the positioning member;

[0016] The positioning member is fixedly mounted on the step hole;

[0017] A top screw is provided in the top screw hole, and the lower end of the top screw abuts against the step surface of the step hole, so as to adjust the contact state between the ball head and the ball socket in a non-measuring state until a critical state is reached: the upper plane of the support device is in contact with the lower plane of the measuring platform, and the circumferential surfaces of the multiple ball sockets are in full contact with the circumferential surfaces of the corresponding ball heads.

[0018] Furthermore, the weighing mechanism includes a weighing sensor, a weighing sensor mounting plate, an upper support for a tension spring, a tension spring, a lower support for a tension spring, a guide post, a steel ball bushing guide seat, a steel ball bushing, a lifting cylinder and a bracket;

[0019] The bracket is fixedly mounted on the top surface of the base, the lower portion of the bracket is fixedly connected to the lifting cylinder, and the upper portion of the bracket is fixedly connected to the steel ball bushing guide seat, and the steel ball bushing guide seat is provided with a cylindrical through hole;

[0020] The steel ball bushing is sleeved in the cylindrical through hole of the steel ball bushing guide seat, and the guide column is sleeved in the steel ball bushing;

[0021] One end of the piston rod of the lifting cylinder abuts against the lower end of the guide post, and the upper end of the guide post is fixedly connected to the lower end of the weighing sensor mounting plate;

[0022] The weighing sensor is fixedly connected to the weighing sensor mounting plate;

[0023] The tension spring upper support is symmetrically arranged on both sides of the weighing sensor mounting plate;

[0024] The tension spring is symmetrically arranged on both sides of the bracket with lower supports;

[0025] The upper support for the tension spring on each side is connected to the lower support for the tension spring through the tension spring, and the tension spring is in a vertical state;

[0026] When the piston rod of the lifting cylinder extends upward, the weighing sensor is lifted. When the piston rod of the lifting cylinder retracts, the weighing sensor is reset under the action of its own weight and the tension spring.

[0027] Furthermore, the weighing device further includes a lifting mechanism;

[0028] The jacking mechanism is arranged between the top surface of the base and the lower plane of the measuring platform;

[0029] When the workpiece to be measured is installed, the lifting mechanism lifts the measuring platform to a state where the ball head is separated from the ball socket.

[0030] Furthermore, displacement sensors are provided on two opposite sides of the outer circumferential surface of the measuring platform along the Z direction and two opposite sides along the Y direction, for monitoring the displacement of the measuring platform in the Z direction and the Y direction;

[0031] Among them, the vertical direction is the X direction, the horizontal direction is the Z direction, and the direction perpendicular to the Z direction in the horizontal plane is the Y direction, which satisfies the right-hand rectangular coordinate system rule;

[0032] Furthermore, the weighing device also includes a measuring tool;

[0033] The measuring tool includes an outer tool frame and an inner tool frame. The inner tool frame is rotatably connected to the outer tool frame via a rotating pin arranged along the Z direction. The inner tool frame can rotate relative to the outer tool frame around the axis of the rotating pin. A slewing bearing is fixedly installed on the inner bottom surface of the inner tool frame. The workpiece to be measured is coaxially fixedly connected to the slewing bearing. The slewing bearing can drive the workpiece to be measured to rotate around the axis of the slewing bearing.

[0034] Furthermore, the weighing device further comprises a torsion bar, a driving mechanism, a braking mechanism and a photoelectric sensor, and the supporting device is an air bearing;

[0035] The rotor of the air bearing is coaxially fixed to one end of the torsion bar, and the other end of the torsion bar is fixed to the base;

[0036] The driving mechanism is fixedly connected to the base and can drive the measuring platform to rotate at a set angle, so that the torsion bar is in a torsion state;

[0037] The photoelectric sensor is fixedly connected to the base and can measure the torsional period of the measuring platform;

[0038] The braking mechanism is fixedly connected to the base and can stop the measurement platform from torsionally swinging.

[0039] Furthermore, the number of the positioning members is three.

[0040] Beneficial effects:

[0041] (1) A support device is fixedly installed on the top surface of the base, and a plurality of ball sockets are arranged on the upper surface of the support device; a workpiece to be measured is fixedly installed on the upper surface of the measuring platform, and a plurality of positioning members are arranged on the measuring platform, one end of the positioning member is a ball head, and the other end is a flange, the ball head protrudes from the lower plane of the measuring platform, and the ball head and the ball socket correspond one to one; a plurality of weighing mechanisms are arranged between the top surface of the base and the lower plane of the measuring platform; the weighing mechanism includes a weighing sensor and a lifting device for lifting the weighing sensor; in a non-measuring state, the measuring platform is supported on the upper end of the support device by the cooperation of the plurality of ball heads and the plurality of ball sockets; in a measuring state, the lifting device can lift the weighing sensor, and the lifted weighing sensor can lift the measuring platform to a state where the ball head and the ball socket are separated, and the weight of the measuring platform and the workpiece to be measured fixed on the measuring platform is entirely borne by the weighing sensor.

[0042] In this way, the measuring platform is positioned by cooperating with multiple ball heads and ball sockets, so that the measuring platform can have a unique and determined position relative to the supporting device in the non-measuring state. Therefore, each time the center of mass of the object is measured, the measuring platform is always lifted from the same determined position, so that the position between the workpiece installed on the measuring platform and the weighing sensor is determined in the measuring state, thereby improving the accuracy of the center of mass measurement; moreover, even if the measuring platform produces a slight lateral displacement when being lifted, resulting in the ball head not being able to be completely aligned with the ball socket, the circumferential surface of the ball socket has a guiding effect on the ball head, so that the ball head can still fall into the ball socket, thereby ensuring that the measuring platform always has a determined position relative to the supporting device in the non-measuring state, and therefore has a high-precision repeatable positioning function.

[0043] (2) A stepped hole for installing a positioning member is provided on the measuring platform, and the positioning member is fixedly installed in the stepped hole; a gasket is sandwiched between the lower end surface of the flange of the positioning member and the stepped surface of the stepped hole, which is used to adjust the contact state between the ball head and the ball socket in the non-measuring state until a critical state is reached: the upper plane of the support device is in contact with the lower plane of the measuring platform, and the circumferential surfaces of the multiple ball sockets are in full contact with the circumferential surfaces of the corresponding ball heads.

[0044] In this critical state, on the one hand, because the upper plane of the support device fits with the lower plane of the measuring platform, the bearing area of ​​the support device on the measuring platform is increased, so that the support device is evenly stressed, which is conducive to maintaining the stability of the device and improving the accuracy of the center of mass measurement. It also avoids the problems of low relative surface support reliability and insufficient point support force caused by the multi-point support positioning of the measuring platform formed by the cooperation of multiple ball heads and multiple ball sockets; on the other hand, because the circumferential surfaces of the multiple ball sockets maintain full-circle contact with the circumferential surfaces of the corresponding ball heads, this improves the positioning accuracy of the measuring platform, thereby improving the center of mass measurement accuracy.

[0045] (3) A top screw hole is provided on the flange of the positioning member; a step hole for installing the positioning member is provided on the measuring platform; the positioning member is fixedly installed in the step hole; a top screw is provided in the top screw hole, and the lower end of the top screw abuts against the step surface of the step hole, which is used to adjust the contact state between the ball head and the ball socket in the non-measuring state until a critical state is reached: the upper plane of the support device is in contact with the lower plane of the measuring platform, and the circumferential surfaces of the multiple ball sockets are in full contact with the circumferential surfaces of the corresponding ball heads.

[0046] In this way, by turning the top screw, the contact state between the ball head and the ball socket can be adjusted quickly and conveniently to quickly reach the critical state: the upper plane of the support device fits into the lower plane of the measuring platform, and the circumferential surfaces of multiple ball sockets are in full contact with the circumferential surfaces of the corresponding ball heads.

[0047] (4) The lifting mechanism is arranged between the top surface of the base and the lower surface of the measuring platform. When the workpiece to be tested is installed, the lifting mechanism lifts the measuring platform until the ball head and the ball socket are separated. This can avoid the problem of severe impact between the positioning member and the ball socket when the workpiece to be tested is installed on the measuring platform, which may cause damage to the positioning accuracy of the device.

[0048] (5) The measuring tool comprises an outer tool frame and an inner tool frame. The inner tool frame is rotatably connected to the outer tool frame via a rotating pin arranged along the Z direction. The inner tool frame can rotate relative to the outer tool frame around the axis of the rotating pin. A rotary bearing is fixedly installed on the inner bottom surface of the inner tool frame. The workpiece to be measured is coaxially fixed to the rotary bearing. The rotary bearing can drive the workpiece to be measured to rotate around the axis of the rotary bearing.

[0049] In this way, when measuring the center of mass of the test piece in each direction of X, Y and Z, a measurement can be made every time the angle is rotated, obtaining multiple measurement quantities, thereby improving the accuracy of the center of mass measurement; and the direct measurement of the axial center of mass of the test piece can be converted into the measurement of the offset between the two axial centers of mass, which is simple and fast.

[0050] (6) When the supporting device is an air bearing, the rotor of the air bearing is coaxially fixed to one end of the torsion bar, and the other end of the torsion bar is fixed to the base; the driving mechanism is fixed to the base and can push the measuring platform to rotate to a set angle, so that the torsion bar is in a torsion state; the photoelectric sensor is fixed to the base and can measure the torsion period of the measuring platform; the braking mechanism is fixed to the base and can stop the measuring platform from torsion.

[0051] In this way, the device can also be used to conveniently and quickly measure the moment of inertia of the workpiece to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A schematic diagram of a multi-point weighing and positioning device for centroid measurement provided by the present invention;

[0053] Figure 2 for Figure 1 Schematic diagram of the distribution structure of the positioning parts;

[0054] Figure 3 for Figure 1 Schematic diagram of the structure of the top screw hole and the fastening screw hole provided on the flange of the middle positioning member;

[0055] Figure 4 for Figure 1 Structural diagram of the middle positioning member;

[0056] Figure 5 for Figure 1 A schematic diagram of one installation method of the positioning piece;

[0057] Figure 6 for Figure 1 Schematic diagram of another installation method of the positioning piece;

[0058] Figure 7 for Figure 1 Schematic diagram of the structure of the weighing mechanism;

[0059] Figure 8 This is a schematic diagram of the axial centroid measurement principle;

[0060] Figure 9 This is a schematic diagram of the axial centroid measurement process;

[0061] Among them: 1-adjusting foot, 2-base, 3-lifting mechanism, 4-displacement sensor, 5-braking mechanism, 6-measuring platform, 7-torsion bar, 8-weighing mechanism, 801-weighing sensor, 802-weighing sensor mounting plate, 803-upper support for tension spring, 804-tension spring, 805-lower support for tension spring, 806-guide column, 807-steel ball bushing guide seat, 808-steel ball bushing, 809-ball head pad, 810-lifting cylinder, 811-bracket, 9-support device, 10-torsion pendulum drive mechanism, 11-tooling outer frame, 12-slewing bearing, 13-rotating pin, 14-tooling inner frame, 15-test piece, 16-positioning piece, 17-fastening screw hole, 18-jackscrew hole, 19-gasket, 20-fastening screw, 21-jackscrew. DETAILED DESCRIPTION

[0062] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0063] Example 1:

[0064] like Figures 1-6 As shown, a multi-point weighing device for centroid measurement with high-precision repeatable positioning function is provided, and its structure comprises a base 2, a support device 9, a measuring platform 6 and a plurality of weighing mechanisms 8, wherein:

[0065] A supporting device 9 is fixedly installed on the top surface of the base 2, and a plurality of (three in this embodiment, and distributed in an equilateral triangle) inverted truncated cone-shaped ball sockets (i.e., the small diameter end of the truncated cone-shaped ball sockets faces downward) in the upper plane of the measuring platform 6 can be fixedly installed on the upper plane of the measuring platform 6. In addition, three positioning members 16 are fixedly installed on the bottom surface of the measuring platform 6. One end of the positioning member 16 is a ball head and the other end is a flange. The positioning member 16 is fixedly installed on the measuring platform 6 through the flange. The ball head protrudes from the bottom surface of the measuring platform 6, and the ball head on the positioning member 16 corresponds one-to-one to the ball socket on the supporting device 9; a plurality of weighing mechanisms 8 are arranged between the top surface of the base 2 and the measuring platform 6. Between the bottom surfaces of the measuring platform 6, the weighing mechanism 8 includes a weighing sensor 801 and a lifting device for lifting the weighing sensor 801, and the weighing sensor 801 is fixedly connected to the lifting device; in the measuring state, the weighing sensor 801 can be lifted by the lifting device, and the lifted weighing sensor 801 can lift the measuring platform 6 to a state where the ball head and the ball socket are disengaged, and the weight of the measuring platform 6 and the workpiece to be measured 15 fixedly mounted on the measuring platform 6 is entirely borne by the weighing sensor 801 in the weighing mechanism 8; in the non-measuring state, the weighing sensor 801 is not lifted, and at this time, the measuring platform 6 is supported on the supporting device 9 by the cooperation between the ball head and the ball socket.

[0066] In this way, the measuring platform is supported on the supporting device through the cooperation of the three ball heads and the three ball sockets, and the measuring platform is positioned, so that the measuring platform 6 can have a unique and determined position relative to the supporting device 9 in the non-measuring state. Therefore, each time the center of mass of the object is measured, the measuring platform 6 is always lifted from the same determined position, so that the measured object 15 installed on the measuring platform 6 and the weighing sensor 801 have a determined position in the measuring state, thereby improving the accuracy of the center of mass measurement; moreover, even if the measuring platform 6 produces a small lateral displacement when being lifted, resulting in the ball head not being able to be completely aligned with the ball socket, the circumferential surface of the ball socket has a guiding effect on the ball head, so that the ball head can still fall into the ball socket, thereby ensuring that the measuring platform 6 always has a determined position relative to the supporting device 9 in the non-measuring state, and therefore has a high-precision repeatable positioning function.

[0067] Example 2:

[0068] In the first embodiment, the base 2 is provided with an adjustment foot 1 at its bottom, the support device 9 utilizes a T-shaped air bearing, and the measuring platform 6 is disc-shaped, with its axis passing through the center of the equilateral triangle formed by the three ball sockets. Furthermore, the measuring platform 6 is provided with a stepped hole for mounting a positioning member 16, and the flange of the positioning member 16 is provided with set screw holes 17. In this embodiment, the set screw holes 17 are evenly spaced along the circumference of the flange, allowing set screws 20 to secure the positioning member 16 to the stepped hole through the set screw holes 17. A gasket 19 is sandwiched between the lower end surface of the flange of the positioning member 16 and the stepped surface of the stepped hole. The gasket 19 is used to adjust the fit between the ball head 16 and the ball socket in the non-measurement state until the following critical state is reached: the upper surface of the rotor of the T-shaped air bearing is in contact with the lower surface of the measuring platform 6, and the circumferential surfaces of the three ball sockets are in full contact with the circumferential surfaces of the corresponding ball heads. In this critical state, on the one hand, because the upper plane of the rotor of the T-type air bearing fits with the lower plane of the measuring platform 6, the bearing area of ​​the T-type air bearing on the measuring platform 6 is increased, so that the T-type air bearing is evenly stressed, which is conducive to maintaining the stability of the device and improving the accuracy of the center of mass measurement. It also avoids the problems of low relative surface support reliability and insufficient point support force caused by the three-point support positioning of the measuring platform 6 formed by the cooperation of three ball heads and three ball sockets; on the other hand, because the circumferential surfaces of the three ball sockets maintain full-circle contact with the circumferential surfaces of the corresponding ball heads, this improves the positioning accuracy of the measuring platform 6, thereby improving the center of mass measurement accuracy.

[0069] Example 3:

[0070] Considering that the gasket 19 needs to be repeatedly stacked between the lower end face of the flange of the positioning member 16 and the step surface of the step hole to achieve the above-mentioned critical state, the positioning member 16 also needs to be repeatedly disassembled and assembled, which is inconvenient to operate. In this embodiment, the top screw 21 is used to replace the function of the gasket 19.

[0071] Specifically, refer to Figure 3 and Figure 6 The positioning member 16 is fixedly installed on the step hole of the measuring platform 6 by a fastening screw 20. A top screw hole 18 is circumferentially arranged on the flange of the positioning member 16. In this example, a top screw hole 18 is arranged on both sides of each fastening screw hole 17; a top screw 21 is arranged in the top screw hole 18, and the lower end of the top screw 21 abuts against the step surface of the step hole. By twisting the top screw 21, the contact state between the ball head and the ball socket can be adjusted conveniently and quickly, so as to quickly reach the critical state in which the upper plane of the rotor of the T-type air bearing is in contact with the lower plane of the measuring platform 6 and the circumferential surfaces of the three ball sockets are in full contact with the circumferential surfaces of the corresponding ball heads.

[0072] It is worth noting that, because the measuring platform 6 is made of aluminum alloy in this embodiment, Figure 6 A gasket 19 is provided between the middle top screw 21 and the step surface, but the function of the gasket 19 is to prevent the top screw 21 from directly contacting the step surface with lower hardness, thereby playing a protective role. This is different from the function of the gasket 19 in the second embodiment.

[0073] Example 4:

[0074] Based on any of the above embodiments, the number of weighing mechanisms 8 is set to three and distributed in a regular triangle. Figure 7 As shown, the weighing mechanism 8 comprises a weighing sensor 801 (a force sensor), a weighing sensor mounting plate 802, an upper support 803 for a tension spring, a tension spring 804, a lower support 805 for a tension spring, a guide post 806, a steel ball bushing guide seat 807, a steel ball bushing 808, a ball head spacer 809, a lifting cylinder 810 and a bracket 811, and the connection relationship is as follows:

[0075] The bracket 811 is fixedly mounted on the top surface of the base 2. The lower part of the bracket 811 is fixedly connected to the lifting cylinder 810, and the upper part is fixedly connected to the steel ball bushing guide seat 807. The steel ball bushing guide seat 807 is provided with a cylindrical through hole. The steel ball bushing 808 is sleeved in the cylindrical through hole of the steel ball bushing guide seat 807. The guide column 806 is sleeved in the steel ball bushing 808. A ball head pad 809 is fixedly connected to one end of the piston rod of the lifting cylinder 810. The lower end of the guide column 806 abuts against the ball head pad 809. The guide column 806 The upper end of the bracket 811 is fixedly connected to the lower end of the weighing sensor mounting plate 802, the weighing sensor 801 is fixedly mounted on the weighing sensor mounting plate 802, the upper support 803 for the tension spring is symmetrically arranged on both sides of the weighing sensor mounting plate 802, the lower support 805 for the tension spring is symmetrically arranged on both sides of the bracket 811, and the upper support 803 for the tension spring and the lower support 805 for the tension spring on each side are connected through the tension spring 804, and the tension spring 804 is in a vertical state.

[0076] When the piston rod of the lifting cylinder 810 extends upward, it lifts the guide post 806 via the ball head pad 809. The lifting of the guide post 806 lifts the load cell mounting plate 802, thereby lifting the load cell 801 fixed to the load cell mounting plate 802. When the piston rod of the lifting cylinder 810 retracts, the load cell 801 returns downward under the action of its own weight and the tension spring 804. When the load cell 801 is lifted and returns downward, the steel balls on the steel ball bushing 808 simultaneously roll against the outer circumference of the guide post 806 and the inner circumference of the steel ball bushing guide seat 807. Moreover, due to the existence of this friction, the steel ball bushing 808 will also move vertically upward or downward with the guide post 806, but its movement speed will be slower than that of the guide post 806.

[0077] Preferably, the lifting cylinder 810 in the weighing mechanism 8 is a thin cylinder, and in the present embodiment, the stroke of the lifting cylinder 810 is 25 mm, the cylinder diameter is 100 mm, and the maximum output thrust can reach 600 kg. The three lifting cylinders 810 can work together to generate a thrust of 1.8 t, which meets the motion requirements of the measuring platform 6. Moreover, by adjusting the air flow rate of the air inlet and outlet of the lifting cylinder 810, the speed of the piston rod extension and retraction can be adjusted to avoid the problem of excessive speed causing the weighing sensor 801 to impact when lifting the measuring platform 6 or the problem of low measurement efficiency due to too slow speed. It is understandable that the steel ball bushing 808 can be replaced by a more general shaft sleeve. In this case, the outer wall of the shaft sleeve can be fixedly connected to the steel ball bushing guide seat 807, and the guide post 806 is slidably connected to the shaft sleeve. In this way, the weighing mechanism 8 can also play a lifting role.

[0078] The lifting cylinder 810 is in contact with the upper guide column 806 by the ball head pad 809, and no fastening connection is required; the use of the steel ball bushing 808 can ensure the movement accuracy of the guide column 806, and avoid the position change of the weighing sensor 801 due to the gap of the moving pair, thereby reducing the measurement accuracy of the center of mass.

[0079] Preferably, the three load cells 801 utilize German HBM C10 sensors, which have an accuracy of no less than 0.03% and offer the advantages of high precision and reliability. When the measuring platform 6 is elevated, the spherical indenters of the load cells 801 directly contact the lower surface of the measuring platform 6, ensuring the positional accuracy of the contact points.

[0080] Embodiment 5:

[0081] In addition to any of the above embodiments, a lifting mechanism 3 is further provided. The lifting mechanism 3 is staggered with three weighing mechanisms 8, also arranged in an equilateral triangle. The weighing mechanisms 8 are capable of lifting the measuring platform 6 to disengage the ball head from the socket. This prevents severe impact between the positioning member 16 and the socket when the test piece 15 is mounted on the measuring platform 6, thereby damaging the positioning accuracy of the device.

[0082] Example 6:

[0083] When using the above-mentioned multi-point weighing device to measure the center of mass, first, define the coordinate system of the multi-point weighing device and the coordinate system of the workpiece 15 to be measured. For the multi-point weighing device, define the vertical direction 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, and establish a right-handed rectangular coordinate system; for the workpiece 15 to be measured, let its axial direction be the X direction. When the product 1 to be measured is placed vertically (that is, the axial direction is along the vertical direction), its Z direction and Y direction are consistent with the Z direction and Y direction in the coordinate system of the multi-point weighing device.

[0084] A measuring fixture is mounted on the upper surface of the measuring platform 6 to secure a workpiece 15 to be measured. Specifically, the measuring fixture comprises an outer fixture frame 11 and an inner fixture frame 14. The inner fixture frame 14 is rotatably connected to the outer fixture frame 11 via a rotating pin 13 arranged along the Z direction. The inner fixture frame 14 is capable of rotating relative to the outer fixture frame 11 about the axis of the rotating pin 13. Furthermore, a slewing bearing 12 is fixedly mounted on the inner bottom surface of the inner fixture frame 14. The workpiece 15 to be measured is coaxially fixedly coupled to the slewing bearing 12. The slewing bearing 12 is driven by a rotation drive unit. Together, the slewing bearing 12 and the rotation drive unit constitute an automatic rotation mechanism that enables the slewing bearing 12 to drive the workpiece 15 to rotate about its axis.

[0085] Rotating the tooling inner frame 14 about the axis of the rotating pin 13 rotates the workpiece 15 to an axially horizontal position. Therefore, the center of mass of the workpiece 15 can be measured in the Y-axis, Z-axis, and X-axis (i.e., the axial center of mass) within the coordinate system of the workpiece 15. Furthermore, the automatic rotation mechanism enables the workpiece 15 to rotate about its own axis. Therefore, when measuring the center of mass of the workpiece 15 in each direction (X, Y, and Z), a measurement can be made for each rotation angle, resulting in multiple measurements and improving the accuracy of the center of mass measurement. Specifically, when measuring the Y-axis and Z-axis center of mass of the test piece 15, the test piece 15 is driven to rotate by the slewing bearing 12, and the center of mass is measured once every set rotation angle. In this example, the center of mass is measured once every 1° rotation; when the test piece 15 rotates one circle (i.e., 360°), the measurement results at multiple angles can theoretically obtain a series of center of mass coordinate values ​​around the rotation axis, i.e., the central axis of the slewing bearing 12. The curve formed by this series of center of mass coordinate values ​​is theoretically a circle with a radius of r, where r is the distance from the center of mass to the rotation axis.

[0086] like Figure 7As shown, the measurement of the axial center of mass (i.e., the X-axis center of mass) is based on the center of mass measurement principle of the three-point weighing method. The workpiece 15 to be tested is rotated to an axially horizontal posture through the inner frame 14 of the tooling. Through two measurements in the forward and reverse directions, the direct measurement of the axial center of mass of the workpiece 15 to be tested is converted into the measurement of the two axial center of mass offsets, thereby calculating the distance between the axial center of mass and the axis of the rotating pin 13. In addition, the distance between the axis of the rotating pin 13 and the large end face of the workpiece 15 to be tested (i.e., the end face fixed on the slewing bearing 12, i.e., the bottom face of the workpiece 15 to be tested) can be directly measured. Based on this, the distance between the axial center of mass and the large end of the workpiece 15 to be tested can be obtained, and then the axial center of mass coordinates of the workpiece 15 to be tested can be obtained according to the total length of the workpiece 15 to be tested. The calculation of the axial center of mass coordinates of the workpiece 15 to be tested can be specifically referred to. Figure 8 The process, in which Figure 8 The large end in the figure refers to the large end surface of the test piece 15 , and the distance between the center of mass and the rotation axis is the average of the positive center of mass position X1 and the reverse center of mass position X2, that is, (X1+X2) / 2.

[0087] In this multi-point weighing device, during the process of the measuring platform 6 being lifted, the theoretical position of the measuring platform 6 relative to the weighing sensor 801 does not change. However, since the spherical pressure head of the weighing sensor 801 is in direct contact with the measuring platform 6 without positioning, in order to avoid unexpected interference causing the relative position of the measuring platform 6 and the weighing sensor 801 to change, displacement sensors 4 are provided on the outer side of the outer circumferential surface of the measuring platform 6 on two opposite sides along the Z direction and on two opposite sides along the Y direction, which are used to monitor the displacement of the measuring platform 6 in the Z direction and the Y direction.

[0088] Embodiment seven:

[0089] The multi-point weighing device also includes a torsion bar 7, a drive mechanism 10, a brake mechanism 5, and a photoelectric sensor (not shown). These components are used to measure the moment of inertia of the test piece 15. Specifically, the rotor of the T-type air bearing 9 is coaxially fixed to one end of the torsion bar 7, and the other end of the torsion bar 7 is fixed to the base 2. When measuring the moment of inertia, the measuring platform 6 is placed on the T-type air bearing 9, and the test piece 15 is fixed to the slewing bearing 12, thereby measuring the moment of inertia in the X, Y, and Z directions. The drive mechanism 10 is fixed to the measuring base 2 and is used to rotate the measuring platform 6 by a set angle, so that the torsion bar 7 is in a torsion state. The torsion stress is then released through the torsion bar 7, causing the measuring platform 6 to drive the test piece 15 to oscillate back and forth. The photoelectric sensor is fixed to the base and can be used to measure the oscillation period. The brake mechanism 5 is fixed to the base 2 and mainly comprises a brake cylinder 3, which is used to stop the oscillating measuring platform 6 and return it to its original position after the measurement is completed. The entire torsion pendulum device uses the torsion bar method to measure moment of inertia. Its compact structure allows the measuring platform 6 to quickly return to its original position for the next measurement of the test piece 15. Specifically, the brake cylinder 3 is a single-acting cylinder, with a friction plate (not shown) fixed to both the telescopic end of the brake cylinder 3 and the bottom surface of the measuring platform 6. After the measurement is completed, the telescopic end of the brake cylinder 3 is extended, and the two friction plates come into contact, causing the measuring platform 4 to quickly stop its torsion.

[0090] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-point weighing device for centroid measurement with high-precision repeated positioning function, characterized in that: It includes a base, a supporting device, a measuring platform and multiple weighing mechanisms; The support device is fixedly mounted on the top surface of the base, and a plurality of ball sockets are arranged on the upper surface of the support device; The upper surface of the measuring platform is used for fixing and mounting the workpiece to be measured, and a plurality of positioning members are provided on the measuring platform, one end of the positioning member is a ball head, and the other end is a flange, the ball head protrudes from the lower plane of the measuring platform, and the ball head corresponds to the ball socket one by one; A plurality of weighing mechanisms are arranged between the top surface of the base and the lower plane of the measuring platform; the weighing mechanism includes a weighing sensor and a lifting device for lifting the weighing sensor; In a non-measuring state, the measuring platform is supported on the upper end of the supporting device by the cooperation between the plurality of ball heads and the plurality of ball sockets; In the measuring state, the lifting device can lift the load cell, and the lifted load cell can lift the measuring platform to a state where the ball head is disengaged from the ball socket, so that the weight of the measuring platform and the workpiece fixedly mounted on the measuring platform is entirely borne by the load cell; The weighing mechanism includes a weighing sensor, a weighing sensor mounting plate, an upper support for a tension spring, a tension spring, a lower support for a tension spring, a guide post, a steel ball bushing guide seat, a steel ball bushing, a lifting cylinder and a bracket; The bracket is fixedly mounted on the top surface of the base, the lower portion of the bracket is fixedly connected to the lifting cylinder, and the upper portion of the bracket is fixedly connected to the steel ball bushing guide seat, and the steel ball bushing guide seat is provided with a cylindrical through hole; The steel ball bushing is sleeved in the cylindrical through hole of the steel ball bushing guide seat, and the guide column is sleeved in the steel ball bushing; One end of the piston rod of the lifting cylinder abuts against the lower end of the guide post, and the upper end of the guide post is fixedly connected to the lower end of the weighing sensor mounting plate; The weighing sensor is fixedly connected to the weighing sensor mounting plate; The tension spring upper support is symmetrically arranged on both sides of the weighing sensor mounting plate; The tension spring is symmetrically arranged on both sides of the bracket with lower supports; The upper support for the tension spring on each side is connected to the lower support for the tension spring through the tension spring, and the tension spring is in a vertical state; When the piston rod of the lifting cylinder extends upward, the weighing sensor is lifted. When the piston rod of the lifting cylinder retracts, the weighing sensor is reset under the action of its own weight and the tension spring.

2. The multi-point weighing device for centroid measurement with high-precision repeated positioning function according to claim 1, characterized in that: The measuring platform is provided with a stepped hole for installing the positioning member; The positioning member is fixedly mounted on the step hole; A gasket is sandwiched between the lower end surface of the flange of the positioning member and the step surface of the step hole, which is used to adjust the contact state between the ball head and the ball socket in the non-measuring state until a critical state is reached: the upper plane of the support device is in contact with the lower plane of the measuring platform, and the circumferential surfaces of multiple ball sockets are in full contact with the circumferential surfaces of the corresponding ball heads.

3. The multi-point weighing device for centroid measurement with high-precision repeated positioning function according to claim 1, characterized in that: A top screw hole is provided on the flange of the positioning member; The measuring platform is provided with a stepped hole for installing the positioning member; The positioning member is fixedly mounted on the step hole; A top screw is provided in the top screw hole, and the lower end of the top screw abuts against the step surface of the step hole, so as to adjust the contact state between the ball head and the ball socket in a non-measuring state until a critical state is reached: the upper plane of the support device is in contact with the lower plane of the measuring platform, and the circumferential surfaces of the multiple ball sockets are in full contact with the circumferential surfaces of the corresponding ball heads.

4. The multi-point weighing device for centroid measurement with high-precision repeated positioning function according to any one of claims 1 to 3, characterized in that: It also includes a jacking mechanism; The jacking mechanism is arranged between the top surface of the base and the lower plane of the measuring platform; When the workpiece to be measured is installed, the lifting mechanism lifts the measuring platform to a state where the ball head is separated from the ball socket.

5. The multi-point weighing device for centroid measurement with high-precision repeated positioning function according to claim 4, characterized in that: Displacement sensors are provided on two opposite sides of the outer circumference of the measuring platform along the Z direction and two opposite sides along the Y direction, for monitoring the displacement of the measuring platform in the Z direction and the Y direction; The vertical direction is the X direction, the horizontal direction is the Z direction, and the direction perpendicular to the Z direction in the horizontal plane is the Y direction, satisfying the right-hand rectangular coordinate system rule.

6. The multi-point weighing device for centroid measurement with high-precision repeated positioning function according to claim 5, characterized in that: Including measuring tooling; The measuring tool includes an outer tool frame and an inner tool frame. The inner tool frame is rotatably connected to the outer tool frame via a rotating pin arranged along the Z direction. The inner tool frame can rotate relative to the outer tool frame around the axis of the rotating pin. A slewing bearing is fixedly installed on the inner bottom surface of the inner tool frame. The workpiece to be measured is coaxially fixedly connected to the slewing bearing. The slewing bearing can drive the workpiece to be measured to rotate around the axis of the slewing bearing.

7. The multi-point weighing device for centroid measurement with high-precision repeated positioning function according to claim 6, characterized in that: It also includes a torsion bar, a driving mechanism, a braking mechanism and a photoelectric sensor, and the supporting device is an air bearing; The rotor of the air bearing is coaxially fixed to one end of the torsion bar, and the other end of the torsion bar is fixed to the base; The driving mechanism is fixedly connected to the base and can drive the measuring platform to rotate at a set angle, so that the torsion bar is in a torsion state; The photoelectric sensor is fixedly connected to the base and can measure the torsional period of the measuring platform; The braking mechanism is fixedly connected to the base and can stop the measurement platform from torsionally swinging.

8. The multi-point weighing device for centroid measurement with high-precision repeated positioning function according to any one of claims 1 to 3 and 5 to 7, characterized in that: The number of the positioning members is three.

Images