CN105571545B - A kind of five-axis linkage machine tools axis of rotation geometric parameter measurement method - Google Patents

Abstract

The invention discloses a method for measuring the geometric parameters of the rotation axis of a five-axis linkage machine tool based on a trigger type probe, belonging to the field of numerical control systems and machine tool structure parameter measurement, and includes the steps of instrument installation, parameter setting, collision acquisition and RTCP parameter calculation. Through the numerical control system, drive the probe probe to collide with the standard ball and lock the machine tool coordinates of the collision point, calculate the center coordinates of the standard ball corresponding to each teaching point according to the coordinates, and use the least squares data processing method to calculate the coordinates of each standard ball The coordinates of the center of the sphere are fitted to the axis direction and spatial position of the active rotation axis and the driven rotation axis to obtain the RTCP parameters. The method of the invention can complete the automatic and precise measurement of the geometric parameters (ie RTCP parameters) of the rotary axis of the five-axis linkage machine tool, and realize the precise control of the center point of the rotary tool.

Description

A method for measuring the geometric parameters of the rotary axis of a five-axis linkage machine tool

technical field

The invention relates to the technical field of numerical control system and machine tool structural parameter measurement, and aims to realize a method for measuring the geometric parameter of the rotary axis of a five-axis linkage machine tool.

Background technique

Rotary tool center control RTCP (Rotational Tool Center Point) technology is an extremely important function of the five-axis linkage CNC system. The RTCP function can directly program the trajectory of the tool center point, making the CNC program independent of the specific machine tool structure. The CNC system will automatically calculate And keep the tool center always on the programmed track, the non-linear error caused by the movement of the rotary axis will be compensated by the movement of the linear axis. When the five-axis machine tool does not have the RTCP function, the tool rotates around the center of the rotary axis when the rotary axis moves, and the tool center point changes in the workpiece coordinate system.

The measurement accuracy of the geometric parameters of the rotary axis of the five-axis machine tool, that is, the RTCP parameters, determines the quality of the RTCP function. Traditional manual measurement methods use dipsticks, dial gauges and square gauges to measure RTCP parameters. Its flaws and limitations are as follows:

1) The axis directions of the driving shaft and the driven shaft are not measured, and the default two axes are parallel to the corresponding coordinate axes and orthogonal to each other, which is the premise of the manual measurement method. However, in practice, the two axes are not necessarily parallel to the coordinate axes, nor are they necessarily orthogonal to each other. This measurement premise cannot be guaranteed, which will cause measurement errors.

2) The general inspection of the roundness of the baseball head and the concentricity of the center of the ball head and the axis of rotation of the spindle has low accuracy, which is not suitable for high-precision measurement occasions, resulting in errors in measurement.

3) The measurement of the double turntable structure requires that the driving shaft can rotate 90° in the positive or negative direction, and not all machine tools have this angular stroke.

4) The operation steps are cumbersome, the degree of automation is low, and the quality of the measurement results often has a lot to do with the experience of the machine tool testers.

In order to solve the defects of manual measurement accuracy and use limitations, realize the automation of measurement to the greatest extent, and realize the precise control of the center point of the rotating tool, it is necessary to seek a better measurement method.

Contents of the invention

In order to solve the defect of manual measurement of RTCP parameters of a five-axis machine tool and the limitations of occasions, the invention provides a method for measuring the geometric parameters of the rotation axis of a five-axis linkage machine tool to realize automatic measurement of RTCP parameters.

The invention uses a trigger type measuring head and a standard ball as a measuring instrument, and secondarily develops a functional interface for automatic measurement of geometric parameters of a five-axis machine tool based on the HNC8. HNC8 is a high-end CNC system developed by Wuhan Huazhong Numerical Control Co., Ltd., and provides a secondary development platform for the development of various complex functions and special interfaces. The numerical control system is equipped with a powerful macro program function similar to high-level language for users. Users can use macro variables to perform arithmetic operations, logic operations, loops and subroutine operations.

In order to achieve the above purpose, the present invention provides a method for measuring the geometric parameters of the rotary axis of a five-axis linkage machine tool, which includes the following steps:

S1: Instrument installation, according to the structure type of the machine tool, install the trigger probe and the standard ball, and use the lever meter to calibrate the spindle concentricity of the probe probe;

S2: Parameter setting, set measurement parameters on the CNC system, including measurement type, display order of rotary axis, name of rotary axis, safety height, positioning speed, intermediate speed, trigger speed, standard ball radius, tool length and tool radius 10 basic Parameters and 8 teaching points of the driving axis and 8 teaching points of the driven axis, the teaching points are used to determine the relative position of the standard ball and the measuring head, and the reference point for collision;

S3: Collision acquisition, through the numerical control system, according to the 10 basic parameters determined in step S2 and the coordinates of 8 teaching points of the driving axis and 8 teaching points of the driven axis, the probe probe of the probe is driven to collide with the standard ball and latched The coordinates X, Y, and Z in the machine tool coordinate system at the time of collision, and each teaching point collides 4 times; the collision process is as follows:

The probe probe collides with the vertex of the standard sphere in the negative direction of the Z axis to lock the machine tool coordinate point 1, collides with the equator of the standard sphere in the positive direction of the X axis and locks the machine tool coordinate point 2, and collides with the equator of the standard sphere in the negative direction of the X axis to lock Save the machine tool coordinate point 3, and collide with the standard sphere equator in the positive or negative direction of the Y axis to lock the machine tool coordinate point 4;

Or, the probe probe collides with the vertex of the standard sphere in the negative direction of Z to lock the machine coordinate point 1, collides with the equator of the standard sphere in the positive direction of the Y axis and locks the machine coordinate point 2, and collides with the equator of the standard sphere in the negative direction of the Y axis. Latch the machine tool coordinate point 3, and latch the machine tool coordinate point 4 by colliding with the standard sphere equator in the positive or negative direction of the X axis;

S4: RTCP parameter calculation, according to the latched coordinates of the collision point, calculate the coordinates of the center of the standard ball corresponding to each teaching point; use the least square data processing method to fit the coordinates of the center of each standard ball to the active rotation axis and the slave The axis direction and spatial position of the driving rotating shaft are used to obtain RTCP parameters, and the RTCP parameters include the direction vector of the axis of the driving shaft, the direction vector of the axis of the driven shaft, the offset vector of the axis of the driving shaft and the offset vector of the axis of the driven shaft.

Further, in the step S1 of the geometric parameter measurement method, for the double-oscillating-head and mixed-type machine tools, the standard ball is mounted on the spindle and the measuring head is placed on the workbench; The installation method of placing the standard ball on the turntable.

Further, during the selection process of the teaching point in step S2 of the geometric parameter measurement method, the active rotation axis or the driven rotation axis maintains any angle, and the probe probe in the Z direction is just in contact with the highest point of the standard ball At this time, the coordinates of the five axes in the machine tool coordinate system are the coordinates of the teaching points; in the travel range of the active rotation axis, 8 teaching points of the driving axis are evenly obtained; in the travel range of the driven rotation axis, 8 Moving axis teaching point.

Further, in the geometric parameter measurement method, according to 8 teaching points of the driving axis and 8 teaching points of the driven axis, the coordinates of the center of the standard ball are respectively fitted by the least square method, and the method of calculating the RTCP parameters is as follows:

According to the driving shaft axis parameter L1 (V1, D1) and the driven shaft axis parameter L2 (V2, D2), calculate the common vertical segment L3 (T1, T2) between the straight line L1 and the straight line L2, and the point T1 is the point of L3 on L1 Pedestal foot, point T2 is the vertical foot of L3 on L2;

Among them: L1(V1, D1) is a straight line determined by the direction vectors V1 and D1, L2(V2, D2) is a straight line determined by the direction vectors V2 and D2; D1 is the center of the trajectory circle fitted by the teaching point of the active axis , which is located on the axis of the driving shaft, V1 is the normal vector of the trajectory circle plane, and is the direction of the axis of the driving shaft; D2 is the center of the trajectory circle fitted by the teaching point of the driven shaft, and is a point on the axis of the driven shaft, V2 is the normal vector of the trajectory circle plane, which is the direction of the axis of the driven shaft;

Finally, the obtained RTCP parameters are: axis direction vector V1 of the driving axis, axis direction vector V2 of the driven axis, offset vector (T2-T1) of the axis of the driving axis, and axis offset vector T1 of the driven axis; The origin of the coordinates is the datum.

Further, in the geometric parameter measurement method, the assignment, collision latch and calculation of the measurement parameters can be realized by using the G code of the numerical control system. The collision action is the basis for collecting required coordinate data, and these data are finally used to calculate RTCP parameters. The principle of collision is that when the probe probe just touches the standard ball and begins to produce a small deformation, the probe sends a trigger signal, the machine tool controls the probe probe to return immediately, and latches the machine tool when the probe probe just touches the standard ball. coordinate.

In the geometric parameter measurement method, the key to calculating the RTCP parameters lies in the calculation of the center of the standard sphere and the fitting of the center of the sphere. The principle is as follows:

1) Calculation of the center of the sphere

According to the 4 spatial coordinate points in the machine coordinate system of the collision latch at the teaching point of the active axis in step S3 Calculate the coordinates Ba _i (X, Y, Z) (i=1,2...8) of the center of the standard sphere at the teaching point of the driving axis, the formula is as follows:

(X-X1) ² +(Y-Y1) ² +(Z-Z1) ² ＝(X-X2) ² +(Y-Y2) ² +(Z-Z2) ²

(X-X1) ² +(Y-Y1) ² +(Z-Z1) ² ＝(X-X3) ² +(Y-Y3) ² +(Z-Z3) ²

(X-X1) ² +(Y-Y1) ² +(Z-Z1) ² ＝(X-X4) ² +(Y-Y4) ² +(Z-Z4) ²

Similarly, the coordinates Bp _i (X, Y, Z) (i=1, 2...8) of the center of the standard sphere at the teaching point of the driven axis can be obtained.

2) Center circle fitting

The locus of the center of the standard sphere is a circle on the space plane. Based on the coordinates of the 8 standard sphere centers of Ba _i (X, Y, Z (i=1, 2...8), use the least squares method to fit the trajectory circle center D1 (X, Y, Z) and the trajectory circle plane normal vector V1 (X, Y, Z), the center of the trajectory circle D1 (X, Y, Z) is a point on the axis of the drive shaft, and the plane normal vector V1 (X, Y, Z) of the trajectory circle is the direction of the axis of the drive axis; according to Bp _i (X, Y, Z) (i=1,2...8) 8 standard ball center coordinates use the least squares method to fit the trajectory circle center D2 (X, Y, Z) and the trajectory circle plane normal vector V2 (X, Y, Z), the center of the trajectory circle D2 (X, Y, Z) is a point on the axis of the driven shaft, and the normal vector of the trajectory circle plane V2 (X, Y, Z) is the direction of the axis of the driven shaft.

3) RTCP parameter calculation

According to the axis parameter L1 (V1, D1) of the driving shaft and the axis parameter L2 (V2, D2) of the driven shaft, calculate the common vertical segment L3 (T1, T2) between the straight line L1 and the straight line L2, point T1 (X, Y, Z ) is the foot of L3 on L1, point T2 (X, Y, Z) is the foot of L3 on L2. L1(V1, D1) represents a straight line determined by direction vectors V1 and D1, and L2(V2, D2) represents a straight line determined by direction vectors V2 and D2.

The RTCP parameters are: axis direction vector V1 (X, Y, Z) of the driving shaft, axis direction vector V2 (X, Y, Z) of the driven axis, offset vector (T2-T1) (X, Y, Z), the axis offset vector T1 (X, Y, Z) of the driven shaft. The above vectors are based on the origin of the machine tool coordinates.

Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

1) Using a standard ball and a trigger probe as a measuring instrument, the equipment is simple and easy to install. It is suitable for double swing heads, double turntables and mixed structures, and the two rotary axes are both orthogonal and non-orthogonal, intersecting and intersecting, and has wide applicability.

2) Secondary development can be carried out on the CNC system to form an independent measurement module interface. Machine tool surveyors can input measurement parameters and complete the entire measurement process with simple operations, which greatly reduces the requirements for machine tool surveyors.

3) The data processing module in the measurement module can accurately calculate the axis direction and axis offset, which changes the limitations of manual measurement of the rotation axis direction and insufficient precision, and realizes the precise control of the center point of the rotating tool.

In a word, the method of the invention can measure RTCP parameters conveniently and accurately, and greatly simplifies the operation of machine tool measuring personnel.

Description of drawings

Fig. 1 is the installation schematic diagram of test machine tool and test instrument in the embodiment method of the present invention;

Fig. 2 is a schematic flow chart of the steps in the method of the embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments, which are not intended to limit the present invention.

Fig. 1 is the physical picture of the test object Tuopu C50AC double turntable five-axis machine tool in the embodiment of the present invention, A turntable is the driving axis, C turntable is the driven axis, and the RTCP parameters of the measurement object are:

1) The axis direction of the rotation axis of A turntable;

2) The axis direction of the rotation axis of the C turntable;

3) A rotary shaft axis offset;

4) The axis of the rotation axis of the C turntable is offset.

Fig. 2 is a schematic flow chart of the steps in the method of the embodiment of the present invention, and the present invention will be further described in detail in conjunction with this figure.

1. Instrument installation. Figure 1 is a schematic diagram of the installation of the test instrument. The measuring head is installed on the spindle, and the standard ball with a diameter of 25mm is adsorbed by the magnetic base on the C turntable. Use a lever gauge to perform concentric calibration of the spindle of the measuring head probe, so that the center of the ball at the end of the probe coincides with the axis of the spindle at a high degree, and the lever gauge needle jumps within 2um during calibration.

2. Parameter setting.

1) Measurement type: double turntable type;

2) The display order of the rotation axis: the coordinate order of the teaching point is consistent with the system setting;

3) Rotary axis name: the name of the active axis comes first, followed by the name of the driven axis, AC;

4. Safety height: When the probe probe approaches the standard ball quickly, the safe distance in the Z direction should be kept from the top of the standard ball, the unit is mm, and the value is 20;

5) Positioning speed: the probe probe quickly approaches the standard ball to a safe height, used for rapid positioning between the probe probe and the standard ball, the unit is mm/min, and the value is 1500;

6) Intermediate speed: the speed at which the probe probe collides with the standard ball and retreats after exceeding the safe height, which is smaller than the positioning speed, the unit is mm/min, and the value is 400;

7) Trigger speed: After the intermediate speed of the probe probe is retracted, the speed at which it continues to collide with the standard ball to accurately collect points is smaller than the intermediate speed, the unit is mm/min, and the value is 200;

8) Standard ball radius: unit mm, value 12.5;

9) Tool length: the distance from the center of the standard ball to the end face of the spindle, in mm, and the value is 273.15;

10) Tool radius: the probe ball radius value. Unit mm, value 3;

11) Teaching points: In this embodiment, the 8 teaching points of the active axis are evenly distributed between -90° and 15° on the A axis, and the 8 teaching points of the driven axis are evenly distributed between 0° and 360° on the C axis , the parameter list is shown in Table 1 and Table 2:

Table 1

initiative x Y Z A C 1 -281.5750 -272.9020 -75.2274 -80.0003 169.2999 2 -281.5750 -251.3027 -79.8707 -67.5006 169.2999 3 -281.5750 -229.2021 -89.4043 -55.0003 169.2999 4 -281.5750 -211.2004 -103.4041 -42.5004 169.2999 5 -281.5750 -194.6009 -121.0047 -30.0003 169.2999 6 -281.5750 -183.6004 -141.6043 -17.5004 169.2999 7 -281.5750 -176.6009 -164.2049 -5.0003 169.2999 8 -281.5750 -174.5004 -187.8040 7.4994 169.2999

Table 2

follower x Y Z A C 1 -254.7888 -393.8996 -174.6999 0.0000 0.0000 2 -333.8890 -363.6998 -174.5994 0.0000 44.9998 3 -368.1888 -286.6990 -174.1997 0.0000 89.9998 4 -338.2415 -208.2367 -173.7368 0.0000 134.9997 5 -261.3366 -173.6701 -173.4783 0.0000 179.9996 6 -182.5136 -203.6070 -173.5775 0.0000 224.9995 7 -147.9459 -280.5108 -173.9765 0.0000 269.9994 8 -177.8826 -359.3324 -174.4414 0.0000 314.9993

3. Collision latch. Through G code programming, 10 basic parameters, 8 teaching points of the driving axis and 8 coordinates of the teaching points of the driven axis, drive the probe probe to collide with the standard ball and latch the coordinate X of the collision point in the machine coordinate system , Y, Z.

1) In this embodiment, the "program jump command" G31 in the HNC8 numerical control system is used to realize the above collision process, and the G31 command code is:

G31L1G01Xx0Yy0Zz0

Among them (x0, y0, z0) is the input target point. When the probe probe collides with the standard ball before feeding to the target point, the system outputs the coordinates X, Y, and Z of the collision point in the machine tool coordinate system.

2) Xa _i , Ya _i , Za _i , Aa _i , Ca _i (i=1,2...8) are the X-axis, Y-axis, Z-axis, A-axis, and C-axis coordinates of the i-th active axis teaching point respectively portion. The machine tool feeds to (Xa _i , Ya _i , Za _i +H, Aa _i ,Ca _i ) (i=1,2…8), where H represents the measurement parameter “safety height” in step S2, at this time the probe The probe is a safe height away from the highest point of the standard ball. The probe probe collides with the vertex of the standard sphere in the negative Z direction to lock the machine tool coordinate point 1 as (X1, Y1, Z1), and then collides with the standard sphere equator in the X positive direction to lock the machine tool coordinate point 2 as (X2, Y2, Z2), and then collide with the standard sphere equator in the X negative direction to lock the machine tool coordinate point 3 as (X3, Y3, Z3), and finally collide with the standard sphere equator in the Y positive direction to lock the machine tool coordinate point 4 as ( X4, Y4, Z4). The 4 points are combined into a matrix:

3) For the teaching points of the driven axis Xp _i , Yp _i , Zp _i , Ap _i , Cp _i (i=1,2...8) are respectively the i-th teaching points of the driven axis X-axis, Y-axis, Z Axis, A-axis, C-axis coordinate components. The machine tool coordinates are fed to (Xp _i , Yp _i , Zp _i +H, Ap _i , Cp _i ) (i=1,2...8), where H represents the measurement parameter "safety height" in step S2. The head probe is a safe height away from the highest point of the standard ball. The probe probe collides with the vertex of the standard sphere in the negative Z direction to lock the machine tool coordinate point 1 as (X1, Y1, Z1), and then collides with the standard sphere equator in the X positive direction to lock the machine tool coordinate point 2 as (X2, Y2, Z2), and then collide with the standard sphere equator in the X negative direction to lock the machine tool coordinate point 3 as (X3, Y3, Z3), and finally collide with the standard sphere equator in the Y positive direction to lock the machine tool coordinate point 4 as ( X4, Y4, Z4). The 4 points are combined into a matrix:

4. RTCP parameter calculation.

1) Calculation of the center of the sphere

According to the 4 spatial coordinate points in the machine tool coordinate system that are latched by the collision at the teaching point of the active axis

Calculate the coordinates Ba _i (X, Y, Z) (i=1,2...8) of the center of the standard sphere at the teaching point of the driving axis, the formula is as follows:

(X-X1) ² +(Y-Y1) ² +(Z-Z1) ² ＝(X-X2) ² +(Y-Y2) ² +(Z-Z2) ²

(X-X1) ² +(Y-Y1) ² +(Z-Z1) ² ＝(X-X3) ² +(Y-Y3) ² +(Z-Z3) ²

(X-X1) ² +(Y-Y1) ² +(Z-Z1) ² ＝(X-X4) ² +(Y-Y4) ² +(Z-Z4) ²

Similarly, the coordinates Bp _i (X, Y, Z) (i=1, 2...8) of the center of the standard sphere at the teaching point of the driven axis can be obtained.

2) Center circle fitting

The locus of the center of the standard sphere is a circle on the space plane. According to Ba _i (X, Y, Z (i=1, 2...8) 8 standard ball center coordinates, use the least squares method to fit the trajectory circle center D1 (X, Y, Z) and the trajectory circle plane normal vector V1 ( X, Y, Z), the center of the trajectory circle D1 (X, Y, Z) is a point on the axis of the A-axis, and the normal vector V1 (X, Y, Z) of the trajectory circle plane is the direction of the axis of the A-axis; according to Bp _i ( X, Y, Z) (i=1,2...8) 8 standard ball center coordinates use the least squares method to fit the trajectory circle center D2 (X, Y, Z) and the trajectory circle plane normal vector V2 (X, Y , Z), the center of the trajectory circle D2 (X, Y, Z) is a point on the axis of the C-axis, and the plane normal vector V2 (X, Y, Z) of the trajectory circle is the direction of the axis of the C-axis.

3) RTCP parameter calculation

According to the A-axis parameters L1 (V1, D1) and C-axis parameters L2 (V2, D2), calculate the common vertical segment L3 (T1, T2) between the straight line L1 and the straight line L2, and the point T1 (X, Y, Z) is L3 The foot on L1, the point T2 (X, Y, Z) is the foot of L3 on L2.

The RTCP parameters are:

A-axis axis direction vector: V1 (-1.000000, -0.000059, -0.000441)

C-axis axis direction vector: V2 (0.000243, 0.004974, -0.999988)

A axis offset vector: (T2-T1) (0.0000, 0.0738, 0.0004)

C axis offset vector: T1 (-257.7030, -283.3569, -421.7816)

It is easy for those skilled in the art to understand that the above descriptions are only preferred examples of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention all include Within the protection scope of the present invention.

Claims (5)

1. A method for measuring the geometric parameters of the axis of rotation of a five-axis linkage machine tool, characterized in that it comprises the following steps: S1: Instrument installation, according to the structure type of the machine tool, install the trigger probe and the standard ball, and use the lever meter to calibrate the spindle concentricity of the probe probe; S2: Parameter setting, set measurement parameters on the CNC system, including measurement type, display order of rotary axis, name of rotary axis, safety height, positioning speed, intermediate speed, trigger speed, standard ball radius, tool length and tool radius 10 basic Parameters and 8 teaching points of the driving axis and 8 teaching points of the driven axis, the teaching points are used to determine the relative position of the standard ball and the measuring head, and the reference point for collision; S3: Collision collection, through the numerical control system, according to the 10 basic parameters determined in step S2 and the coordinates of 8 teaching points of the driving axis and 8 teaching points of the driven axis, drive the probe probe to collide with the standard ball and latch it The coordinates X, Y, and Z in the machine tool coordinate system at the time of collision, and each teaching point collides 4 times; the collision process is as follows: The probe probe collides with the vertex of the standard sphere in the negative direction of the Z axis to lock the machine tool coordinate point 1, collides with the equator of the standard sphere in the positive direction of the X axis and locks the machine tool coordinate point 2, and collides with the equator of the standard sphere in the negative direction of the X axis to lock Save the machine tool coordinate point 3, and collide with the standard sphere equator in the positive or negative direction of the Y axis to lock the machine tool coordinate point 4; or, The probe probe collides with the vertex of the standard sphere in the negative direction of Z to lock the machine coordinate point 1, collides with the equator of the standard sphere in the positive direction of the Y axis and locks the machine tool coordinate point 2, and collides with the equator of the standard sphere in the negative direction of the Y axis and latches it. The machine tool coordinate point 3 collides with the standard sphere equator in the positive or negative direction of the X axis to lock the machine tool coordinate point 4; S4: RTCP parameter calculation, according to the latched coordinates of the collision point, calculate the coordinates of the center of the standard ball corresponding to each teaching point; use the least square data processing method to fit the coordinates of the center of each standard ball to the active rotation axis and the slave The axial direction and spatial position of the moving rotating shaft are obtained to obtain RTCP parameters, and the RTCP parameters include the axial direction vector of the driving shaft, the axial direction vector of the driven shaft, the offset vector of the axis of the driving shaft and the offset vector of the axis of the driven shaft; The calculation method of RTCP parameters is as follows: According to the driving shaft axis parameter L1 (V1, D1) and the driven shaft axis parameter L2 (V2, D2), calculate the common vertical segment L3 (T1, T2) between the straight line L1 and the straight line L2, and the point T1 is the point of L3 on L1 Pedestal foot, point T2 is the vertical foot of L3 on L2; Among them: L1(V1, D1) is a straight line determined by the direction vectors V1 and D1, L2(V2, D2) is a straight line determined by the direction vectors V2 and D2; D1 is fitted by the least squares method from the teaching point of the active axis The center of the trajectory circle is located on the axis of the driving shaft, V1 is the normal vector of the plane of the trajectory circle, and is the direction of the axis of the driving shaft; D2 is the center of the trajectory circle fitted by the least square method from the teaching point of the driven axis, and is A point on the axis of the driven shaft, V2 is the normal vector of the trajectory circle plane, and is the direction of the axis of the driven shaft; Finally, the obtained RTCP parameters are: axis direction vector V1 of the driving axis, axis direction vector V2 of the driven axis, offset vector (T2-T1) of the axis of the driving axis, and axis offset vector T1 of the driven axis; The origin of the coordinates is the datum. 2. The method for measuring geometric parameters as claimed in claim 1, characterized in that, in the process of selecting the teaching point in step S2, the active rotation axis or the driven rotation axis maintains any angle, and the measuring head probe in the Z direction and the When the highest point of the standard ball is just in contact, the coordinates of the five axes under the machine tool coordinate system are the coordinates of the teaching points; within the travel range of the active rotation axis, 8 teaching points of the active axis are obtained evenly; range, evenly acquire 8 slave axis teaching points. 3. The method for measuring geometric parameters as claimed in claim 1 or 2, characterized in that, in step S1, for double-oscillating heads and hybrid structure machine tools, the installation mode in which the spindle is clamped with a standard ball and the workbench is placed with a probe is used. The double turntable type machine tool adopts the installation method of clamping the probe on the spindle and placing the standard ball on the turntable. 4. The method for measuring geometric parameters as claimed in claim 1 or 2, characterized in that, in step S4, the formula for calculating the coordinates of the center of the standard ball at each teaching point is: (X-X1) ² +(Y-Y1) ² +(Z-Z1) ² ＝(X-X2) ² +(Y-Y2) ² +(Z-Z2) ² (X-X1) ² +(Y-Y1) ² +(Z-Z1) ² ＝(X-X3) ² +(Y-Y3) ² +(Z-Z3) ² (X-X1) ² +(Y-Y1) ² +(Z-Z1) ² ＝(X-X4) ² +(Y-Y4) ² +(Z-Z4) ² Among them, (X1, Y1, Z1), (X2, Y2, Z2), (X3, Y3, Z3), (X4, Y4, Z4) are 4 under the machine coordinate system of the collision latch at the teaching point in step S3 space coordinate points, (X, Y, Z) are the center coordinates of the standard sphere to be sought. 5. The geometric parameter measurement method according to claim 1 or 2, wherein, in the geometric parameter measurement method, the assignment, collision latch and calculation of the measurement parameters are realized by using the G code of the numerical control system.