CN-121977631-A - Workpiece measurement system and method based on displacement sensor

CN121977631ACN 121977631 ACN121977631 ACN 121977631ACN-121977631-A

Abstract

The invention relates to the technical field of workpiece measurement, in particular to a workpiece measurement system and method based on a displacement sensor. The invention can realize the rapid automatic measurement of the workpiece by matching the displacement sensor with the circular substrate, improves the production efficiency, reduces the manual intervention and reduces the error caused by manual operation, the system is suitable for conical workpieces with spherical crown tops, the measurement accuracy can be still maintained when the workpiece size is larger, and the system is suitable for various industrial application scenes.

Inventors

SUN FENGJU
WANG XIAOSAN
CHEN XUE
GUO YIMENG
BAI TIAN
HUO RUIDONG
ZHANG MENG
TIAN JUNHONG

Assignees

北京航天计量测试技术研究所
北京市计量检测科学研究院

Dates

Publication Date: 20260505
Application Date: 20241129

Claims (6)

1. A workpiece measuring system based on a multi-displacement sensor is characterized by comprising a circular base plate and more than three displacement sensors which are uniformly arranged below the circular base plate and surround a workpiece, wherein the diameter of the circular base plate is not smaller than 3 times of the diameter of a spherical crown of the workpiece, the circular base plate is tightly attached to the top end of the spherical crown, the resolution of the displacement sensors is lower than 1 mu m, the radius of a circle distributed by the sensors is R, which is about 3 times of the radius of the spherical crown at the top end of the workpiece, and the distance between the sensors and the upper end face of a measuring platform, namely the distance between the sensors and the lower end face of the workpiece, is calibrated in advance.
2. The system of claim 1, wherein the number of displacement sensors is 3, the three sensors are assumed to be L 1 、L 2 、L 3 , the coordinate system is defined by taking the bottom end face of the workpiece as an xoy plane, taking the projection of the circle center of the distribution circle of the three sensors on the bottom end face as an origin O, taking the direction of the first displacement sensor as the negative direction of the y axis, taking the direction of the top end of the workpiece as the positive direction of the z axis, and the xyz direction accords with the right rule.
3. The system of claim 2, wherein the coordinate values of the three displacement sensors in the defined coordinate system are (x 1 ,y 1 ,z 1 ),(x 2 ,y 2 ,z 2 ),(x 3 ,y 3 ,z 3 ),, respectively, according to the calibrated dimension values, in the following relation: x 1 =0 y 1 =-R z 1 ＝L 1 z 2 ＝L 2 z 3 ＝L 3 Wherein the displacement values measured by the three displacement sensors are w 1 、w 2 、w 3 respectively, the xy coordinate values of the corresponding three points A, B, C of the substrate are unchanged, and the z coordinate values are added with w 1 、w 2 、w 3 respectively, namely A(x 1 ,y 1 ,z 1 +w 1 ),B(x 2 ,y 2 ,z 2 +w 2 ),C(x 3 ,y 3 ,z 3 +w 3 ); The plane equation of the basal plane of the substrate is satisfied: vector ab= (x 2 -x 1 ,y 2 -y 1 ,z 2 -z 1 ) Vector ac= (x 3 -x 1 ,y 3 -y 1 ,z 3 -z 1 ) Cross multiplying vector AB and vector AC to obtain normal vector n= (ab×ac); The normal vector N is used in a plane equation in the general form ax+by+cz+d=0, wherein A, B, C is three components of the normal vector N, wherein the coordinates of a known point are substituted into the plane equation, the equation is solved to obtain the value of D, and the values of A, B, C and D are substituted into the value ax+by+cz+d=0 to obtain the equation of the plane.
4. The system of claim 3 wherein the angle between the base plane and the xOy plane is obtained By a normal vector of n 1 = (a, B, C) for plane ax+by+cz+d=0 and n 2 = (0, 1), and the angle between the planes is cos θ = |n 1 ·n 2 |/(|n 1 |·|n 2 |), where n 1 | represents the dot product of the vector and n 1 is the modular length of the vector.
5. The system of claim 3 or 4, wherein the workpiece height H is obtained By substituting x=0 and y=0 according to the base equation ax+by+cz+d=0 to obtain the coordinate height value z of the point G, the actual workpiece height is the point M, and the correction amount gm=eg-EM, that is, gm=r/cos θ -R, so that the corrected workpiece height is D- (R/cos θ -R).
6. A method of measuring a workpiece based on a displacement sensor, implemented with a system according to any one of claims 1 to 5, comprising the steps of: The method comprises the steps of sticking a round base plate to the top end of a spherical crown, uniformly arranging three displacement sensors around a workpiece below the round base plate, setting coordinate values of the three displacement sensors in a defined coordinate system to be (x 1 ,y 1 ,z 1 ),(x 2 ,y 2 ,z 2 ),(x 3 ,y 3 ,z 3 ), respectively according to the dimension values obtained by calibration, and obtaining the following relation: x 1 =0 y 1 =-R z 1 ＝L 1 z 2 ＝L 2 z 3 ＝L 3 The displacement values measured by the three displacement sensors are w 1 、w 2 、w 3 respectively, the xy coordinate values of the corresponding three points A, B, C of the substrate are kept unchanged, and the z coordinate values are added with w 1 、w 2 、w 3 respectively, namely A(x 1 ,y 1 ,z 1 +w 1 ),B(x 2 ,y 2 ,z 2 +w 2 ),C(x 3 ,y 3 ,z 3 +w 3 ); Wherein, the plane equation that the basal plane of base plate is located satisfies: vector ab= (x 2 -x 1 ,y 2 -y 1 ,z 2 -z 1 ) Vector ac= (x 3 -x 1 ,y 3 -y 1 ,z 3 -z 1 ) The normal vector is a vector perpendicular to the plane and is calculated by cross multiplication, and the vector AB and the vector AC are subjected to cross multiplication to obtain a normal vector N: N= (AB multiplied by AC); Using the normal vector N in a plane equation, substituting the coordinate of a known point into the plane equation, and solving the equation to obtain the value of D; substituting A, B, C and D values into ax+by+Cz+D=0 to obtain a plane equation; The included angle between the basal plane and the xOy plane is obtained By adopting the following mode that the normal vector of the plane ax+By+Cz+D=0 is n 1 = (A, B, C), the normal vector of the plane xOy is n 2 = (0, 1), and the included angle between the two planes is cos theta= |n 1 ·n 2 |/(|n 1 |·|n 2 |), wherein, the operation of point multiplication of the vector is represented, and the n 1 | represents the modular length of the vector n 1 ; The workpiece height H is obtained By substituting x=0 and y=0 according to the basal plane equation ax+by+cz+d=0, namely, obtaining the coordinate height value of the G point as z, the actual workpiece height as M point, and the correction quantity GM=EG-EM, namely, GM=R/cos theta-R, so that the corrected workpiece height is D- (R/cos theta-R).

Description

Workpiece measurement system and method based on displacement sensor Technical Field The invention relates to the technical field of workpiece measurement, in particular to a workpiece measurement system and method based on a displacement sensor. Background Two measurement methods are now basically used for the length measurement of workpieces: Caliper measurement is generally used for smaller object measurement, is difficult to match with a caliper measuring tool with a larger measuring range when facing a large-scale workpiece, and because the workpiece is conical, the caliper cannot accurately clamp the top and bottom surfaces of the workpiece due to the limitation of the length of a clamping jaw. The displacement sensor measures, namely a common measuring method with a unit displacement sensor and a double displacement sensor, but the two methods cannot completely eliminate the measuring error caused by the inclination of the substrate. As in the unit shift sensor measurement method of fig. 1, the substrate is not level in both x-axis and y-axis directions, which introduces measurement errors in the height of the workpiece, whereas the dual shift sensor measurement method is shown in fig. 2, although the rotation of the substrate around the direction perpendicular to the connection lines of the two displacement sensors does not introduce a significant measurement error, the deflection around the connection lines of the sensors still introduces a certain measurement error. Disclosure of Invention In view of the above, the invention provides a workpiece length measuring system and method based on a displacement sensor, which can measure parameters such as the length, the mass center, the moment of inertia and the like of a workpiece together, and realize rapid and high-accuracy automatic measurement. In order to achieve the above purpose, the technical scheme of the invention is as follows: The invention provides a workpiece measuring system based on a displacement sensor, which comprises a circular substrate and more than three displacement sensors uniformly arranged around a workpiece below the circular substrate, wherein the diameter of the circular substrate is not smaller than 3 times of the diameter of a spherical crown of the workpiece, the circular substrate is tightly attached to the top end of the spherical crown, the resolution of the displacement sensor is lower than 1 mu m, the radius of a circle distributed by the sensor is R, which is about 3 times of the radius of the spherical crown at the top end of the workpiece, and the distance between the sensor and the upper end face of a measuring platform, namely the distance between the sensor and the lower end face of the workpiece, is calibrated in advance. The three sensors are assumed to be L 1、L2、L3 respectively, the coordinate system is defined as follows, the bottom end face of the workpiece is taken as an xoy plane, the projection of the circle center of the distribution circle of the three sensors on the bottom end face is taken as an origin O, the directional displacement sensor is in the negative direction of the y axis, the directional displacement sensor is in the positive direction of the z axis, and the xyz direction accords with the right rule. The coordinate values of the three displacement sensors in the defined coordinate system are (x1,y1,z1),(x2,y2,z2),(x3,y3,z3), respectively according to the dimension values obtained by calibration, and the three displacement sensors have the following relation: x1=0 y1=-R z1＝L1 z2＝L2 z3＝L3 Wherein the displacement values measured by the three displacement sensors are w 1、w2、w3 respectively, the xy coordinate values of the corresponding three points A, B, C of the substrate are unchanged, and the z coordinate values are added with w 1、w2、w3 respectively, namely A(x1,y1,z1+w1),B(x2,y2,z2+w2),C(x3,y3,z3+w3); The plane equation of the basal plane of the substrate is satisfied: vector ab= (x 2-x1,y2-y1,z2-z1) Vector ac= (x 3-x1,y3-y1,z3-z1) Cross multiplying vector AB and vector AC to obtain normal vector n= (ab×ac); The normal vector N is used in a plane equation in the general form ax+by+cz+d=0, wherein A, B, C is three components of the normal vector N, wherein the coordinates of a known point are substituted into the plane equation, the equation is solved to obtain the value of D, and the values of A, B, C and D are substituted into the value ax+by+cz+d=0 to obtain the equation of the plane. The included angle between the base plane and the xOy plane is obtained By adopting the following mode that the normal vector of the plane ax+by+cz+d=0 is n 1 = (A, B, C), the normal vector of the plane xOy is n 2 = (0, 1), the included angle between the two planes is cos theta= |n 1·n2|/(|n1|·|n2 |), wherein, the operation of point multiplication of the vector is represented, and the model length of the vector n 1 is represented By the|n 1 |. The workpiece height H is obtained By substituting x=0 and y