CN110345838B - A method for measuring the working radius of a four-axis centrifuge - Google Patents

Abstract

The invention provides a method for measuring the working radius of a four-axis centrifuge, which belongs to the technical field of inertial device testing equipment. The four-axis centrifuge in the present invention is mainly composed of a main shaft and three worktable rotary shafts, which can test multiple accelerometers at the same time. The distance between the three workbenches was firstly measured by using the theodolite to measure the 120° evenly spaced error of the three workbenches, and then the difference between the working radii of the three workbenches was measured, and then a standard cylinder and a 1m vernier caliper were used. The accurate distances between the three worktables' rotation axes are measured, and finally the working radii of the three worktables are accurately calculated based on these parameters. Compared with the commonly used direct radius measurement method and the inverse calculation radius method, the invention can accurately and efficiently measure the working radius of the four-axis centrifuge, and can be used in the case that the main shaft axis is difficult to lead out.

Description

A method for measuring the working radius of a four-axis centrifuge

technical field

The invention relates to a method for measuring the working radius of a four-axis centrifuge, and belongs to the technical field of inertial device testing equipment.

Background technique

For the test of inertial devices, especially accelerometers, the single gravity field roll test can only generate excitation of ±1g, which is not enough to simulate the real flight environment of the aircraft, and cannot effectively stimulate the nonlinear error term coefficient related to the specific force of the inertial device. . Therefore, it is necessary to use a high-precision centrifuge to generate centripetal acceleration greater than 1g to calibrate and test inertial devices.

The four-axis centrifuge is mainly composed of a rotary main shaft, three worktables (A, B, and C) that can rotate continuously for 360°, a shaft system, and a turntable control cabinet. The control system can control the 4 shaft systems to run in the speed and position mode, so that the 4 shaft systems work according to the instructions, and give the specified acceleration input to the accelerometer. When the main shaft of the centrifuge rotates at a constant angular velocity ω, and the working radius of the centrifuge is R, the centripetal acceleration provided by the centrifuge is Rω ² . Obviously, the working radius error of the centrifuge will directly affect the input accuracy of the accelerometer, and ultimately affect the test and calibration accuracy of the accelerometer. Therefore, it is very important to accurately measure the working radius of the centrifuge. Conventional centrifuge radius measurement methods include the use of high-precision measuring rods/blocks and micrometers, laser interferometer measurement, direct measurement of working radius by invar meter ruler/caliper comparison method, etc., and use of accelerometer to calculate radius back Methods. However, due to the limitation of the structure of the main shaft and worktable of the four-axis centrifuge, these direct measurement methods cannot be applied to the four-axis centrifuge. At the same time, the accuracy of the inverse calculation of the working radius is limited by the accuracy of the accelerometer and the dynamic error of the centrifuge. When the accuracy of the accelerometer is not high, the test error is large. Therefore, a new working radius measurement method must be designed for the four-axis centrifuge.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the above-mentioned problems in the prior art, and further provide a method for measuring the working radius of a four-axis centrifuge.

The purpose of this invention is to realize through the following technical solutions:

A method for measuring the working radius of a four-shaft centrifuge. The four-shaft centrifuge described in the present invention includes a main shaft and three small table shafts A, B, and C. Ideally, the axes of rotation of the A, B, and C shafts are the same as The axes of the main shafts are parallel and evenly distributed at 120° on a circle with a radius of 0.5m. The centripetal acceleration generated by the rotation of the main shaft at a uniform angular rate is used to calibrate multiple acceleration sensors; the measurement method of the present invention includes the following steps:

Step 1: The centrifuge table axis 120° evenly spaced error test:

1) Use a spirit level to measure the parallelism between the rotation axes of the three worktables of the centrifuge. The parallelism error should not be greater than ±20″, otherwise compensation should be made when calculating the working radius later.

2) Install the target on the main shaft end of the centrifuge and the installation surfaces of the three workbenches, set up the theodolite, rotate each shaft system and observe each target, and adjust the target to its respective axis of rotation,

3) Measure the distance D from the center reference of the theodolite to the axis of the main shaft,

4) Use the theodolite to align the rotation axis of the main shaft, rotate the main shaft, make the rotation axis of the worktable A, the vertical axis of the theodolite and the main shaft rotation axis in the same vertical plane, record the horizontal angle α ₁ of the theodolite, and assume that the main shaft at this time at the 0° position,

5) the main shaft is rotated by 120° and 240° respectively, the theodolite is aligned with the axis of rotation of workbench B and workbench C respectively, and the horizontal angles _α2 and α3 _of the theodolite are recorded;

△α₃₁＝-△α₁₂-△α₂₃；6) When R is the nominal radius of the centrifuge, the calculated uniform errors are:

Δα ₃₁ =-Δα ₁₂ -Δα ₂₃ ;

Step 2: Centrifuge table A and B, A and C working radius difference test:

1) Rotate the main shaft of the centrifuge so that the common vertical line between the main axis of the centrifuge and the axis of rotation of table A is perpendicular to the projected connection line between the center of the theodolite and the axis of rotation of table A on the horizontal plane. At this time, use the theodolite to align the table The target on A, record the horizontal angle α ₄ of the theodolite, and assume that the main shaft of the centrifuge is at 0° at this time,

2) Rotate the main shaft by 120° and 240°, respectively, align the theodolite with the axis of rotation of the workbench B and workbench C, and record the horizontal angles α ₅ and α ₆ of the theodolite,

3) Calculate the working radius errors of worktables A and B, A and C are respectively

Step 3: Test the distance between two centrifuge workbenches:

1) Install the standard cylinders 1, 2, and 3 on the shaft ends of the workbenches A, B, and C respectively, measure the radial runout of the outer surface of the standard cylinder with a dial indicator, and adjust the standard cylinder to make its axis correspond to the corresponding work. The axes of rotation of the table are coincident,

2) Use vernier calipers to measure the diameters d ₁ , d ₂ , d ₃ of standard cylinders one, two and three,

3) Use a vernier caliper to measure the distance between the outer cylindrical surfaces of the three standard cylinders, which are R ₁₂ , R ₂₃ , and R ₁₃ respectively, and calculate the distance between the rotation axes of the workbenches:

Step 4: Calculate the three working radii of the centrifuge:

According to the measurement and calculation results in steps 2, 3, and 4, it can be known that the radius errors of the three worktables are △R, △R+△r ₂ , and △R+△r ₃ ;

Using the cosine theorem of plane triangle, when R ₀ is the nominal radius of the centrifuge, we can get

Ignoring the second-order small quantities in the formula, we get

Calculate the average value to get the working radius error of table A

Calculate the actual working radius of workbenches A, B and C as

R _A =R ₀ +△R, R _B =R ₀ +△R+△r ₂ , R _C =R ₀ +△R+△r ₃ ;

So far, the detection of the working radius of the four-axis centrifuge is completed.

The beneficial effects of the present invention are:

The method for measuring the working radius of a four-axis centrifuge provided by the present invention overcomes the limitation of the special shaft end structure and worktable distribution structure of the four-axis centrifuge to directly measure the radius by installing a measuring sensor.

The invention not only accurately separates the uniform distribution error of the working table of the centrifuge, but also indirectly and accurately measures three working radii through the geometric relationship between the working tables. At the same time, compared with the method of measuring the radius of the three workbenches by repeatedly installing the measuring instrument, the method proposed by the present invention can complete the measurement of the working radius of all the workbenches through simple installation, thereby improving the measurement efficiency.

The present invention can still be applied when the main shaft axis cannot be drawn out, which reflects the practicability of the method.

Description of drawings

Figure 1 is a schematic diagram of the structure of a four-axis centrifuge.

Figure 2 is a schematic diagram of the distribution of the working table of the four-axis centrifuge.

Figure 3 is a schematic diagram of the test of the difference between the two working radii of the workbenches.

Figure 4 is a schematic diagram of the distance test between workbenches.

Figure 5 is a schematic diagram of the alignment target.

Reference signs in the figure, 1 is the centrifuge base, 2 is the centrifuge main shaft, 3 is the extension shaft end of the centrifuge main shaft, 4 is the workbench A, 5 is the accelerometer tooling of the workbench A, and 6 is the measured acceleration 7 is the workbench B, 8 is the accelerometer tooling of the workbench B, 9 is the workbench C, 10 is the accelerometer tooling of the workbench C, 11 is the theodolite, 12 is the standard cylinder one, 13 is the standard cylinder two, 14 is the standard cylindrical three.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings: the present embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner, but the protection scope of the present invention is not limited to the following embodiments.

As shown in Figure 1, the four-axis centrifuge consists of a centrifuge main shaft 2 and three workbenches, namely workbench A4, workbench B7 and workbench C9. The centrifuge main shaft 2 is arranged on the centrifuge base 1, and the centrifuge main shaft is 2. The table supported by 2 is provided with a table A4, a table B7 and a table C9 at 120° to each other. The centrifuge main shaft extension shaft end 3 of the centrifuge main shaft 2 protrudes from the table, and the table A4 is provided with the acceleration of the table A. Gauge tooling 5, accelerometer tooling 8 of table B is set on table B7, accelerometer tooling 10 of table C is arranged on table C9, accelerometer 6 to be measured is arranged on table A4, centrifuge spindle 2 And worktable A4, worktable B7 and worktable C9 can be fully rotated 360°, clockwise and counterclockwise.

As shown in Figure 2, under ideal conditions, the working radius of the three workbenches, namely workbench A4, workbench B7 and workbench C9, are all 0.5m, and the workbenches should be distributed at equal intervals of 120°, but there are actually uniform distributions. Errors Δα ₁₂ , Δα ₂₃ , Δα ₃₁ and radius errors.

As shown in Figure 3, erect the theodolite 11 to observe the target, rotate the centrifuge main shaft 2, so that the common vertical line between the centrifuge main axis and the rotation axis of the table A4 is the projection of the center of the theodolite 11 and the rotation axis of the table A4 on the horizontal plane The connecting line is vertical. At this time, use the theodolite 11 to align the target on the worktable A4, record the horizontal angle α ₄ of the theodolite 11 , and assume that the centrifuge main shaft 2 is at the 0° position at this time. Rotate the main shaft by 120° and 240° respectively, align the theodolite 11 with the axis of rotation of the workbench B7 and workbench C9, record the horizontal angles α ₅ and α ₆ of the theodolite 11, and calculate the work of workbenches A and B, A and C. The radius errors are

As shown in Figure 4, the standard cylinder one 12 is installed on the shaft end of the workbench A4, the standard cylinder two 13 is installed on the shaft end of the workbench B7, and the standard cylinder three 14 is installed on the shaft end of the workbench C9. Measure the diameters d ₁ , d ₂ and d ₃ of standard cylinders one, two and three, and measure the distance between the outer cylindrical surfaces of the three standard cylinders, which are R ₁₂ , R ₂₃ , and R ₁₃ respectively.

As shown in Figure 5, a copper filament is installed in the center of the target, and the filament in the target can be accurately drawn out by aligning the theodolite to observe the filament in the target.

Example 1:

With reference to Fig. 1, Fig. 2, Fig. 3, Fig. 4 and Fig. 5; the method for measuring the working radius of the four-axis centrifuge of the present invention, the steps are as follows:

Step 1: The centrifuge table axis 120° evenly spaced error test:

1) Use a spirit level to measure the parallelism between the rotation axes of the three worktables of the centrifuge, which are 14.49", 11.85", and 3.69" respectively. The parallelism error is not greater than ±20", so it is not necessary to calculate the working radius later. compensate.

2) Install the target on the shaft end of the main shaft of the centrifuge and the installation surfaces of the three workbenches, set up a theodolite to observe the target, and adjust the target to its respective axis of rotation;

3) Measure the distance D=1380mm from the center reference of the theodolite to the axis of the main shaft;

4) Use the theodolite to align the axis of rotation of the main shaft, rotate the main shaft, make the axis of rotation of worktable A, the vertical axis of the theodolite and the axis of rotation of the main shaft are in the same vertical plane, and record the horizontal angle of the theodolite α ₁ =110°53′06.5 ", and assume that the main axis is at the 0° position at this time;

5) Rotate the main shaft by 120° and 240° respectively, align the theodolites with the axis of rotation of worktable B and worktable C respectively, and record the horizontal angles of the theodolites α ₂ =110°53'17.75" and α ₃ =110°53'01.25 ";

6) R is the nominal radius of the centrifuge. When R=500mm, the calculated uniform distribution errors are

Δα ₃₁ =-Δα ₁₂ -Δα ₂₃ =28.96".

Step 2: Centrifuge table A and B, A and C working radius difference test:

1) Rotate the main shaft of the centrifuge so that the common vertical line between the main axis of the centrifuge and the axis of rotation of table A is perpendicular to the projected connection line between the center of the theodolite and the axis of rotation of table A on the horizontal plane. At this time, use the theodolite to align the table For the target on A, record the horizontal angle of the theodolite α ₄ =132°25'08", and assume that the main shaft of the centrifuge is at 0° at this time;

2) Rotate the main shaft by 120° and 240° respectively, align the theodolites with the axes of rotation of worktable B and worktable C respectively, and record the horizontal angles of the theodolites α ₅ =132° 25'26" and α ₆ =132° 25'06.5 ";

3) Calculate A and B, the working radius errors of A and C are respectively

Step 3: Test the distance between two centrifuge workbenches:

1) Install the standard cylinders 1, 2, and 3 on the shaft ends of the workbenches A, B, and C respectively, measure the outer surface of the standard cylinder with a dial indicator, and adjust its center to the rotation axis of the workbench;

2) Use a vernier caliper to measure the diameter of the standard cylinder d ₁ =90.060mm, d ₂ =90.077mm, d ₃ =90.067mm;

3) Use a vernier caliper to measure the distance between the outer cylindrical surfaces of the three standard cylinders, which are R ₁₂ =956.053mm, R ₂₃ =956.050mm, and R ₁₃ =95.980mm, respectively. And calculate the distance between the two rotation axes of the worktables:

Step 4: Calculate the three working radii of the centrifuge:

According to the measurement and calculation results in steps 2, 3, and 4, it can be known that the radius errors of the three worktables are ΔR, ΔR+Δr ₂ , and ΔR+Δr ₃ respectively.

Using the cosine theorem of plane triangle, when R ₀ is the nominal radius of the centrifuge, it can be obtained;

Ignoring the second-order small quantities in the formula, we get

Calculate the average value to get the working radius error of table A

Calculate the actual working radius of workbenches A, B and C as

R _A =R ₀ +△R=499.92775mm,

R _B =R ₀ +△R+△r ₂ =500.04000mm,

R _C =R ₀ +ΔR+Δr ₃ =499.91840 mm.

The above are only preferred specific embodiments of the present invention, and these specific embodiments are based on different implementations under the overall concept of the present invention, and the protection scope of the present invention is not limited to this, any person familiar with the technical field Changes or substitutions that can be easily conceived by a skilled person within the technical scope disclosed by the present invention shall be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (1)

1. A method for measuring the working radius of a four-axis centrifuge, the four-axis centrifuge includes a main shaft and three small workbenches A, B, C shafts, ideally the workbench A, B, C shafts The axis of rotation is parallel to the axis of the main shaft, and evenly distributed at 120° on a circle with a radius of 0.5m. The centripetal acceleration generated by the rotation of the main shaft at a uniform angular rate is used to calibrate multiple acceleration sensors; it is characterized in that it includes the following steps: Step 1: The centrifuge table axis 120° evenly spaced error test: 1) Use a spirit level to measure the parallelism between the rotation axes of the three worktables of the centrifuge. The parallelism error should not be greater than ±20″, otherwise compensation should be made when calculating the working radius later. 2) Install the target on the main shaft end of the centrifuge and the installation surfaces of the three worktables, set up the theodolite, rotate each shaft system and observe each target, and adjust the target to its respective rotation axis, 3) Measure the distance D from the center reference of the theodolite to the axis of the main shaft, 4) Use the theodolite to align the axis of rotation of the main shaft, rotate the main shaft so that the axis of rotation of worktable A is in the same vertical plane as the vertical axis of the theodolite and the axis of rotation of the main shaft, record the horizontal angle α ₁ of the theodolite, and assume that the main shaft at this time at the 0° position, 5) the main shaft is rotated by 120° and 240° respectively, the theodolite is aligned with the axis of rotation of workbench B and workbench C respectively, and the horizontal angles _α2 and α3 _of the theodolite are recorded; 6) When R is the nominal radius of the centrifuge, the calculated uniform errors are:

Δα ₃₁ =−Δα ₁₂ −Δα ₂₃ ; Step 2: Centrifuge table A and B, A and C working radius error test: 1) Rotate the main shaft of the centrifuge so that the common vertical line between the main axis of the centrifuge and the axis of rotation of table A is perpendicular to the projected connection line between the center of the theodolite and the axis of rotation of table A on the horizontal plane. At this time, use the theodolite to align the table The target on A, record the horizontal angle α ₄ of the theodolite, and assume that the main shaft of the centrifuge is at 0° at this time, 2) Rotate the main shaft by 120° and 240°, respectively, align the theodolite with the axis of rotation of the workbench B and workbench C, and record the horizontal angles α ₅ and α ₆ of the theodolite, 3) Calculate the working radius errors of worktables A and B, A and C are respectively

Step 3: Test the distance between two centrifuge workbenches: 1) Install the standard cylinders 1, 2, and 3 on the shaft ends of the workbenches A, B, and C respectively, measure the radial runout of the outer surface of the standard cylinder with a dial indicator, and adjust the standard cylinder to make its axis correspond to the corresponding work. The axes of rotation of the table are coincident, 2) Use vernier calipers to measure the diameters d ₁ , d ₂ , d ₃ of standard cylinders one, two and three, 3) Use a vernier caliper to measure the distance between the outer cylindrical surfaces of the three standard cylinders, which are R ₁₂ , R ₂₃ , and R ₁₃ respectively, and calculate the distance between the rotation axes of the workbenches:

Step 4: Calculate the three working radii of the centrifuge: According to the measurement and calculation results in steps 2, 3 and 4, it can be known that the working radius errors of the three worktables are ΔR, ΔR+Δr ₂ , and ΔR+Δr ₃ respectively; Using the cosine theorem of plane triangle, when R ₀ is the nominal radius of the centrifuge, we can get:

Ignoring the second-order small quantities in the formula, we get

Calculate the average value to get the working radius error of table A

Calculate the actual working radius of workbenches A, B and C as R _A =R ₀ +ΔR, R _B =R ₀ +ΔR+Δr ₂ , R _C =R ₀ +ΔR+Δr ₃ ; So far, the detection of the working radius of the four-axis centrifuge is completed.

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