CN110174052A - A kind of Hooke's hinge method for testing precision - Google Patents

Abstract

A kind of method for testing precision of Hooke's hinge carries out support fixation after adjusting transiting rod to a certain azimuth by adjusting support；Target ball sphere centre coordinate is measured with laser tracker and is recorded；Calculate the number of the sphere centre coordinate of the target ball positioned at different orientations of measurement, and judge to measure whether number is more than or equal to preset value, if not, then repeat azimuthal adjusting of transiting rod and the test of target ball sphere centre coordinate, if so, the sphere centre coordinate of the target ball positioned at different orientations of acquisition is fitted to a spherical surface and is recorded；Each sphere centre coordinate of the target ball of measurement is calculated at a distance from the spherical surface fitted, the standard deviation sigma of each distance is calculated, uses ± 3 σ as the precision index of evaluation Hooke's hinge.Laser tracker testing efficiency of the present invention is high, and one-shot measurement can complete the acquisition of the sphere center position data of target ball, not only increase testing efficiency, and sphere center position does not need to be fitted, and can improve measuring accuracy to avoid error of fitting.

Description

A Hooke hinge precision testing method

technical field

The invention relates to the technical field of precision equipment, in particular to a method for testing the accuracy of a Hooke hinge.

Background technique

As a hinge mechanism that can provide two degrees of freedom, the Hooke hinge has been widely used in various forms of parallel mechanisms. As an important part of the parallel mechanism, the accuracy of the Hooke hinge has a great influence on the overall motion accuracy of the parallel mechanism, and the clearance of the Hooke hinge is difficult to be corrected and compensated in the kinematic calibration of the parallel mechanism. In order to provide a basis for the selection of Hooke hinges in parallel mechanisms, a test method that can evaluate the manufacturing accuracy of Hooke hinges is needed. At present, there are few public Hooke hinge accuracy testing methods. Patent application number 121510354792.7 discloses a Hooke hinge accuracy testing method. The three-coordinate measuring instrument used in this patent is expensive, not easy to carry, and is obtained by contacting points. The data will be doped with interference items caused by contact deformation, which will have a certain impact on the final test accuracy. In addition, the coordinates of the center of the sphere in this invention patent are obtained through indirect fitting of multiple points on the surface of the standard sphere. This method is not only inefficient, but also has fitting errors, which further affects the test accuracy.

Contents of the invention

In view of this, in order to overcome the defects and problems of the prior art, it is necessary to provide a high-efficiency and high-precision Hooke hinge precision testing method.

A method for testing the accuracy of a Hooke hinge, comprising the following steps:

Step 1, erect the lower U-shape of the Hooke hinge on the test platform;

Step 2, fixedly connecting the transition rod to the upper U-shaped frame of the Hooke hinge;

Step 3, setting the target ball on the transition rod;

Step 4, setting up the laser tracker so that the range of motion of the Hooke hinge is within the testing range of the laser tracker;

Step 5, the transition rod is adjusted to a certain azimuth angle through the adjustment support and then supported and fixed, and the inclination angle of the transition rod can be adjusted through the adjustment support;

Step 6, using the laser tracker to measure and record the coordinates of the center of the target ball to complete a measurement;

Step seven, calculating the number of times of the center coordinates of the target ball located at different azimuth angles, and judging whether the number of measurements is greater than or equal to the preset value, if not, then repeat steps five to six, if so, then go to step Eight;

Step 8, fitting the center coordinates of the target balls obtained at different azimuth angles into a spherical surface and recording;

Step 9, calculate the distance between the center coordinates of the measured target ball and the fitted spherical surface, calculate the standard deviation σ of each distance, and use ±3σ as the accuracy index for evaluating the Hooke hinge .

In one embodiment, the preset value is 10.

In one embodiment, the selection of the azimuth angle of the transition rod satisfies that the target ball is evenly distributed on the upper hemisphere of the Hooke hinge.

In one embodiment, the adjustment support includes a magnetic gauge base and an adjustment support frame, the magnetic gauge base is arranged on the test platform, one end of the adjustment support frame is screwed to the magnetic gauge base, and the One end of the adjustment support frame is used to support the transition rod.

In one embodiment, a U-shaped opening is provided at the end of the adjustment support frame away from the magnetic base, and the transition rod is arranged in the U-shaped opening.

In one embodiment, the lower U-shaped frame of the Hooke hinge is installed on a test platform through a test fixture, and the magnetic gauge base is arranged on the test fixture.

In one embodiment, the laser tracker is set up on the test platform through a tripod, and the height of the tripod is adjustable.

In one embodiment, in step 3, the target ball is magnetically adsorbed to the transition rod.

In one embodiment, in step 3, the transition rod includes a rod body and a target ball seat, one end of the rod body is fixedly connected to the upper U-shaped frame of the Hooke hinge, and the target ball seat is magnetically adsorbed on the The rod body is far away from the end of the upper U-shaped frame, and the target ball is attracted to the target ball seat by magnetic force.

The Hooke hinge accuracy test method above adopts the principle of non-contact measurement, which can avoid the slight deformation or rigid body displacement of the center position of the target ball due to contact force, and improve the test accuracy; in addition, the laser tracker has high test efficiency, and once The measurement can complete the acquisition of the position data of the center of the target ball, which not only greatly simplifies the test process and improves the test efficiency, but also does not need to be fitted to the position of the center of the ball, which can avoid the occurrence of fitting errors and further improve the test accuracy.

Description of drawings

Fig. 1 is the schematic diagram of the Hooke hinge accuracy testing mechanism of an embodiment;

Fig. 2 is a partial schematic view of the Hooke hinge precision testing mechanism shown in Fig. 1;

Fig. 3 is a flow chart of Hooke hinge accuracy test in one embodiment.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. The fixed connection mentioned in the present invention includes direct fixed connection and indirect fixed connection.

Please refer to Fig. 1, Fig. 2 and Fig. 3, the accuracy testing method of the Hooke hinge of an embodiment, comprises the following steps:

S1, set the lower U-shaped frame 3 of the Hooke hinge on the test platform 1 .

In one embodiment, the lower U-shaped frame 3 of the Hooke hinge is set on the test platform 1 through the test fixture 2 . Among them, the test tooling is used to provide a relatively precise installation surface for the tested Hooke hinge and the magnetic table base. Due to the need to fix the magnetic base, the material of the test tool is ferromagnetic.

S2, the transition rod 12 is fixedly connected with the upper U-shaped frame 4 of the Hooke hinge.

In one embodiment, the transition rod 12 is fixedly connected to the upper U-shaped frame 4 of the Hooke hinge by screws. The connection is fixed by screws, which facilitates the installation and disassembly of the transition bar 12 and the upper U-shaped frame 4 .

S3, setting the target ball 7 on the transition rod 12 .

In one embodiment, the target ball 7 is magnetically attracted to the transition rod 12 .

In one embodiment, the transition rod 12 includes a rod body 5 and a target ball seat 6. One end of the rod body 5 is fixedly connected to the upper U-shaped frame 4 of the Hooke hinge, and the target ball seat 6 is magnetically adsorbed on the rod body 5 away from the upper U-shaped frame. 4, the target ball 7 is adsorbed on the target ball seat 6 by magnetic force.

S4 , erecting the laser tracker 10 so that the moving range of the Hooke hinge is within the testing range of the laser tracker 10 .

In one embodiment, the laser tracker 10 is erected on a test platform via a tripod 11 , and the height of the tripod 11 is adjustable.

S5, the transition rod 12 is adjusted to a certain azimuth angle through the adjustment support and then supported and fixed, and the inclination angle of the transition rod 12 can be adjusted through the adjustment support.

In one embodiment, the selection of the azimuth angle of the transition rod 12 satisfies that the target ball 7 is evenly distributed on the upper hemispherical surface of the Hooke hinge.

In one embodiment, the adjustment support includes a magnetic gauge base 9 and an adjustment support frame 8, the magnetic gauge base 9 is arranged on the test platform 1, one end of the adjustment support frame 8 is screwed to the magnetic gauge base 9, and the adjustment support frame 8 One end is used to support the transition rod 12 .

Further, the adjusting support also includes a fixing bracket, and the fixing bracket includes a fixing rod, an adjusting piece and an adjusting screw, and one end of the fixing rod is fixedly arranged on the magnetic gauge base 9 . The adjusting piece is sleeved on the fixing rod. And the positions of the adjusting member and the fixing rod are fixed. A threaded hole perpendicular to the fixed rod is provided on the adjusting member, the adjusting screw and the adjusting member are connected through the threaded hole, and one end of the adjusting screw is fixedly connected with the adjusting support frame 8 . Further, the end of the adjusting screw away from the adjusting support frame 8 is provided with a rotating adjusting member, and the rotating adjusting member is fixedly connected with the adjusting screw. Concave-convex patterns are arranged on the rotary adjusting member, which is convenient for rotating the rotating adjusting member. The rotating movement of the rotating adjusting member drives the adjusting screw to rotate, thereby adjusting the angle of the support frame 8 and achieving the purpose of adjusting the azimuth angle of the transition rod 12 .

In one embodiment, the magnetic gauge base 9 is set on the test fixture 2 .

Further, the end of the adjustment support frame 8 away from the magnetic gauge base 9 is provided with a U-shaped opening, and the transition rod 12 is arranged in the U-shaped opening.

S6, use the laser tracker 10 to measure and record the coordinates of the center of the target ball 7, and complete a measurement.

S7, calculate the number of measured center coordinates of the target ball 7 at different azimuth angles, and determine whether the number of measurements is greater than or equal to a preset value, if not, repeat steps 5 to 6, if yes, go to S8.

That is, continuously adjust the position of the transition rod 12 to make it have different azimuth angles, and test the center coordinates of the target ball 7 when the transition rod 20 is in different azimuth angles. And calculate the number of measurements of the coordinates of the center of the sphere.

The number of measurements refers to the number of measured center coordinates of the target ball 7 located at different azimuth angles.

In one embodiment, the preset value is 10. When the number of tests is less than 10, the azimuth angle of the transition rod 12 is adjusted again, and the coordinates of the center of the target ball 7 are tested. Until the number of tests is equal to 10 times.

S8, fitting the obtained center coordinates of the target ball 7 at different azimuths into a spherical surface and recording.

S9, calculate the distances between the center coordinates of the measured target ball 7 and the fitted spherical surface, calculate the standard deviation σ of each distance, and use ±3σ as the accuracy index for evaluating the Hooke hinge.

The Hooke hinge accuracy test method above adopts the principle of non-contact measurement, which can avoid the slight deformation or rigid body displacement of the center position of the target ball 7 due to contact force, and improve the test accuracy; in addition, the laser tracker 10 has high test efficiency. , the acquisition of the center position data of the target ball 7 can be completed in one measurement, which greatly simplifies the testing process and improves the testing efficiency.

In addition, the laser tracker 10 has the advantage of being easy to carry compared with the three-coordinate measuring instrument, and it is convenient to complete the accuracy test of the Hooke hinge at different locations.

The above are only preferred embodiments of the present invention. It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be regarded as the present invention. protection scope of the invention.

Claims (9)

1. a kind of method for testing precision of Hooke's hinge, which comprises the following steps:

The lower U-shaped frame of Hooke's hinge is set on test platform by step 1；

Transiting rod is fixedly connected by step 2 with the upper U-shaped frame of the Hooke's hinge；

Target ball is set on the transiting rod by step 3；

Step 4 sets up laser tracker, so that the scope of activities of the Hooke's hinge is located at the test model of the laser tracker In enclosing；

Step 5 carries out support fixation, the transiting rod after adjusting the transiting rod to a certain azimuth by adjusting support Tilt angle it is adjustable by the adjusting support；

Step 6 measures the sphere centre coordinate and record of the target ball with the laser tracker, completes one-shot measurement；

Step 7, calculates the number of the sphere centre coordinate of the target ball positioned at different orientations of measurement, and judges to measure number Whether preset value is more than or equal to, if it is not, then repeating step 5 to step 6, if so, carrying out step 8；

The sphere centre coordinate of the target ball positioned at different orientations of acquisition is fitted to a spherical surface and recorded by step 8；

Step 9 calculates each sphere centre coordinate of the target ball of measurement at a distance from the spherical surface fitted, calculates The standard deviation sigma of each distance uses ± 3 σ as the precision index for evaluating the Hooke's hinge.

2. the method for testing precision of Hooke's hinge as described in claim 1, which is characterized in that the preset value is 10.

3. the method for testing precision of Hooke's hinge as described in claim 1, which is characterized in that azimuthal choosing of the transiting rod It takes and meets the target ball and be evenly distributed on the upper half spherical surface of the Hooke's hinge.

4. the method for testing precision of Hooke's hinge as described in claim 1, which is characterized in that the adjusting support includes magnetic power meter Seat and adjustment support frame, the magnetic stand are set on the test platform, one end of the adjustment support frame and the magnetic force Gauge stand is threadedly coupled, and one end of the adjustment support frame is used to support the transiting rod.

5. the method for testing precision of Hooke's hinge as claimed in claim 4, which is characterized in that the adjustment support frame is far from described One end of magnetic stand is equipped with U-shaped opening, and the transiting rod is set in the U-shaped opening.

6. the method for testing precision of Hooke's hinge as claimed in claim 5, which is characterized in that the lower U-shaped frame of the Hooke's hinge is logical Test fixture is crossed on test platform, the magnetic stand is set on the test fixture.

7. the method for testing precision of Hooke's hinge as described in claim 1, which is characterized in that the laser tracker is passed through three Foot prop is set up on the test platform, the tripod it is height-adjustable.

8. the method for testing precision of Hooke's hinge as described in claim 1, which is characterized in that in step 3, by the target ball magnetic Power is adsorbed on the transiting rod.

9. the method for testing precision of Hooke's hinge as claimed in claim 8, which is characterized in that in step 3, the transiting rod packet The body of rod and target ball seat are included, one end of the body of rod is fixedly connected with the upper U-shaped frame of the Hooke's hinge, and the target ball seat passes through magnetic force It is adsorbed on the one end of the body of rod far from the upper U-shaped frame, the target ball is by magnetic-adsorption on the target ball seat.