ACCURACY TRACEABILITY METHOD BASED ON PRECISION COORDINATE CONTROL NETWORK FOR WORKSHOP MEASUREMENT POSITIONING SYSTEM

• US 20160265903A1
• Filed: 03/25/2014
• Published: 09/15/2016
• Est. Priority Date: 11/20/2013
• Status: Active Grant

• Current Assignee: Tianjin University
• Original Assignee: Tianjin University
• Inventors: ZHU, Jigui, LIN, Jiarui, REN, Yongjie, YANG, Linghui, REN, Yu
• Granted Patent: US 9,658,055 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 7/4972 Alignment of sensor

Abstract

The present invention relates to an accuracy traceability method based on precision coordinates control network for workshop Measurement Positioning System, which includes the steps: setting a plurality of SMR (Spherically Mounted Retroreflector) nests and stations in the measurement space; forming a global control point by using SMR; measuring all the 3-d coordinates of global control points in all the laser tracker stations; using the range value measured by the laser tracker as constraints to calculate the 3-d coordinates of global control points by using the dynamic weighting method; arranging a plurality of transmitters and calibrating the transmitters in combination with precision coordinate control network; measuring all global control points and measured points simultaneously by using wMPS, and using the 3-d coordinates of global control points as the constraints for adjustment calculation to obtain the 3-d coordinates of the measured points. The present invention takes advantages of accurate range measurement of laser tracker as a constraint to achieve the followings: obtaining high accuracy 3-d coordinates of global control points, constructing precision coordinate control network and using it as the measurement standards of wMPS, achieving on-site accuracy traceability, and thus improving the measurement accuracy of wMPS.

Claims

1. An accuracy traceability method based on precision coordinate control network for wMPS (workshop Measurement Positioning System), comprising the following steps:

Step 1;

providing N SMR nests and M stations in the measurement space and arranging a laser tracker (201) in station 1;

Step 2;

arranging an SMR (202) on SMR nest 1 to form a global control point 1, measuring 3-d coordinates of global control point 1, and by the same manner, moving the SMR (202) to SMR 2, SMR 3 . . . until SMR N−

1 and SMR N respectively to measure the 3-d coordinates of global control point 2, global control point 3 . . . until global control point N−

1 and global control point N;

Step 3;

arranging the laser tracker (201) on station 2, station 3 . . . until station M−

1 and station M in sequence, and repeating the step 2 after each time the laser tracker (201) is moved, thus obtaining measurements for all the global control points via all the stations and in the step 2 and step 3, the laser tracker (201) must measure at least 3 global control points at each station;

Step 4;

calculating the positions (locations and orientations) of stations according to the 3-d coordinates of all global control points at all stations, thus obtaining initial iteration values of 3-d coordinates of all the stations and global control points;

Step 5;

using the range value from station to global control point measured by the laser tracker (201) as a constraint to establish optimization goal equation for adjustment calculation;

by using the dynamic weighting method, tracing the measurement accuracy of 3-d coordinates of global control points to that of the interferometer range measurement of the laser tracker (201), thus establishing the precision coordinate control network;

Step 6;

arranging and initializing a plurality of transmitters (101), and then calibrating the transmitters in combination with the precision coordinate control network to establish the measurement network;

Step 7;

measuring the global control points and measured points simultaneously by using wMPS (workshop Measurement Positioning System), and using the 3-d coordinates of global control points as the constraint for adjustment calculation to obtain the 3-d coordinates of the measured points, and finally tracing the obtained 3-d coordinates of the measured points to the precision coordinate control network.

2. The accuracy traceability method based on precision coordinate control network for workshop Measurement Positioning System according to claim 1, wherein the detailed steps of establishing the precision coordinate control network of step 5 comprise:

Step 5-1;

according to the 3-d coordinates of global control points in individual station coordinates, calculating the range value r_ij of the laser tracker;

wherein, i represents the i^th station, i=1,2, . . . ,M;

j represents the i^th global control point, j=1,2, . . . ,N;

Step 5-2;

taking the coordinates of station 1 as the global coordinates to calibrate each stations, and calculating the 3-d coordinates of global control points (x_j⁰ y_j⁰ z_j⁰) and station (X_j⁰ Y_j⁰ Z_j⁰) of the laser tracker in global coordinates, which are taken as the initial values during the optimization process;

Establishing redundant range equations in global coordinates, the formula is expressed as follows;

l_ij=√

{square root over ((x_j−

X_i)²+(y_j−

Y_i)²+(z_j−

Z_i)²)} 

 

(2)

Wherein, l_ij is range value, formula (1) is expanded by (x_j⁰ y_j⁰ z_j⁰) and (X_j⁰ Y_j⁰ Z_j⁰)via first order Taylorseries expansion to obtain;

3. The accuracy traceability method based on precision coordinate control network for wMPS (workshop Measurement Positioning System) according to claim 1, wherein the SMR (202) is 1.5 inches SMR;

and the detailed steps of calibrating the transmitters in combination with the precision coordinate control network of step 6 comprise;

Step 6-1;

Replacing the SMR (202) of the global control point with the receiver (104) which has same size and shape as a 1.5 inches SMR;

keeping the locations of the SMR nests (203) unchanged during replacing process, thus keeping the 3-d coordinates of the global control points unchanged;

Step 6-2;

arranging the transmitters (101) in the measurement space, and arranging at least four global control points between every two transmitters for receiving signals from both transmitters simultaneously;

Step 6-3;

arranging a plurality of scale bars at multiple locations in the measurement space after rotating speeds of the transmitters (101) are stabled, and completing the calibration of wMPS by using scale bars and global control points, and finally forming the measurement network.

4. The accuracy traceability method based on precision coordinate control network for workshop measurement positioning system according to claim 1, wherein the detailed steps of calibrating the transmitters in combination with the precision coordinate control network of step 7 comprise:

Step 7-1;

keeping all the receivers (104) located in the global control points and all the transmitters (101) unchanged;

Step 7-2;

arranging receivers (104) in the measured points of measurement space, each receiver (104) must receive signals from at least two transmitters (101) simultaneously;

Step 7-3;

measuring the global control points and measured points simultaneously by using the measurement network formed by transmitters 101, and using the 3-d coordinates of global control points as the constraints for adjustment calculation to obtain the 3-d coordinates of the measured points, and finally tracing the obtained 3-d coordinates of the measured points to the precision coordinate control network.