CN104215185A - Method for calibrating central position of transformer by virtue of light-pen type portable three-coordinate measurement system - Google Patents

Abstract

The invention discloses a method for calibrating the central position of a transformer by virtue of a light-pen type portable three-coordinate measurement system. The method comprises the following steps of: realizing self-calibration on the central position (that is, a light pen measurement head) of the transformer by virtue of the own characteristics of the system, shooting a light pen image by using a CCD camera, transmitting the light pen image to a computer and carrying out real-time processing, obtaining a rotation and translation matrix from a light pen coordinate system to a camera coordinate system by virtue of the transmission and projection relationship of the camera, and establishing a system of nonlinear equations, wherein the solution of the system of nonlinear equations, which is evaluated through the least-squares generalized inverse method is the coordinates of the central position of the transformer under the light pen coordinate system. The method is high in timeliness, simple to operate, easy to realize, stable and rapid, and capable of helping the system top realize high-accuracy three-coordinate measurement in a measurement field.

Description

Utilize the method that the portable coordinate measuring machine of light pen is demarcated transformer center

Technical field

The invention belongs to transformer testing technical field, more particularly, relate to the using method of the portable coordinate measuring machine of light pen, namely utilize the method that the portable coordinate measuring machine of light pen is demarcated transformer center.

Background technology

In T & D Technology field, transformer is conventional electric component, significant to the stability of whole terminal power transmission and transformation, its inner structure, character and the cooperate degree with whole power transmission and transformation network are often concentrated on to its research, to play its performance better, often ignore the mensuration about position resolver aspect, under the state namely under transformer day-to-day operation state or in ectocine, the demarcation of change in location.This problem seems very little, but can affect the stable operation of power transmission and transformation network to a certain extent.Three-dimensional coordinates measurement technology has very important effect in the industrial production, is mainly divided into contact and contactless two kinds.Contact type measurement is that obtain measured surface shape information, more representational survey instrument is three coordinate measuring machine, and this measuring method precision is high, but efficiency is relatively low, and measurement range is also relatively little by gauge head contact testee surface.Non-contact measurement mainly utilizes laser equipment or CCD camera to detect measured object surface, and combining image treatment technology obtains the shape information of measured surface, and wherein vision three-dimensional coordinates measurement is the Typical Representative of non-cpntact measurement.This measuring method precision is one to two orders of magnitude lower than contact type measurement generally, but adopt spot speed soon, and measurement range is large.The portable three coordinate measuring machine of light pen is formed primarily of CCD camera, computing machine and light pen, can realize on-site rapid measurement.It is using light pen as contact measurement instrument, using CCD camera as vision-based detection means, achieve the perfect adaptation of vision non-contact type measurement and contact type measurement, there is the advantages such as lightweight, simple to operate, precision is higher, measurement range is large, be subject to the great attention of various countries gradually.

The light pen three coordinate measuring machine that current international market is released have Metronor company of Norway two/the V-STAR/M system etc. of mono-CCD camera measuring system and Geodetic company of the U.S., domestic light pen measuring system research is started late, and is also still in conceptual phase at present.The different pattern of the replaceable one-tenth of gauge head as the light pen of contact measurement instrument, to adapt to more complicated measurement target, as deep hole, hidden place etc.Usually, because when pattern is different or gauge head is installed, dynamics is different, each head center position installed also often has deviation, must carry out gauge head staking-out work before therefore measuring.Therefore complete the demarcation of head center position fast and accurately in measure field, this scaling method becomes one of gordian technique in portable three-coordinate measuring system gradually.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, there is provided a kind of method utilizing the portable coordinate measuring machine of light pen to demarcate transformer center, the demarcation being about to fast realize accurately in measure field measuring head center position in light pen-type portable three-coordinate measuring system applies in the scaling method of transformer center.

Technical purpose of the present invention is achieved by following technical proposals:

The gauge head of light pen is demarcated different from the gauge head correction principle of three coordinate measuring machine conventional in industry, it is the diameter and the deflection deformation that correct gauge head that the gauge head of three coordinate measuring machine corrects, main use standard ball is carried out, in the maximum magnitude of standard ball, 5 more than equally distributed points are surveyed with manual, operating rod and automatic mode, computer software just carries out the fitting operation of ball after receiving the coordinate of these points, obtain the sphere centre coordinate of matching ball, diameter and shape error, the diameter of matching ball is deducted the diameter of standard ball, just obtain the diameter correcting rear gauge head.It is then solve the coordinate figure of head center position under light pen coordinate system that the gauge head of light pen is demarcated.

The ultimate principle of technical solution of the present invention is: utilize a standard cone, light pen gauge head is placed in taper hole, slowly rotate light pen, CCD camera absorbs image and after passing to computer disposal, obtain the rotation translation matrix of light pen coordinate system and camera coordinates system, because standard cone and CCD camera are relatively-stationary, and light pen is originally as rigid objects, according to the location invariance of gauge head center under light pen coordinate system and under camera coordinates system, by the coordinate of Algorithm for Solving gauge head center under light pen coordinate system, owing to selecting to control in transformer center by gauge head center, this resolving also just obtains the coordinate of transformer center.

Select gauge head center to control in transformer center, if gauge head center is respectively (u, v, w) with the coordinate of light pen coordinate system under camera coordinates system ^t, (x, y, z) ^t.Be tied to the rotation translation relation of camera coordinates system from light pen coordinate according to spatial point, known:

$\left[\begin{array}{c}x\\ y\\ z\end{array}\right]=\left[\mathrm{RT}\right]\·\left[\begin{array}{c}u\\ v\\ w\\ 1\end{array}\right]---\left(1\right)$

Rotating translation matrix R and T can by camera Perspective transformation model and in conjunction with document (Yuan J S-C, Ageneral photogrammetric method for determining object position and orientation, IEEE Trans on Robotics and Automation, 1989,5 (2): 129-142) newton-Gaussian processes in solves and obtains.

If when light pen turns to i-th position, the actual coordinate of gauge head center under camera coordinates system is (ui, vi, wi) ^t, ideal value is (u, v, w) ^t, then can obtain optimization objective function:

$g\left(X\right)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\left(f_i\right)}^2---\left(2\right)$

Wherein $f_i(x,y,z,u,v,w)=\sqrt{{(u_i-u)}^2+{(v_i-v)}^2+{(w_i-w)}^2},$ Optimized variable X=(x, y, z, u, v, w), the i.e. coordinate of gauge head center under light pen coordinate system and camera coordinates system.

The Nonlinear System of Equations of system is:

fi(x，y，z，u，v，w)＝0i＝1，2，L，n?(3)

The generalized inverse of least square solution can be used to solve this system of equations, corresponding coordinate (u, v, w) can be obtained ^t, (x, y, z) ^t.This programme is further illustrated in conjunction with above-mentioned steps.

The first step: CCD camera and standard cone are all fixed, adjustment relative position makes light pen be imaged on CCD camera as plane centre position, and under certain amplitude is rocked, the image at all light target mark reference mark still can ensure presenting as in plane; Gauge head is placed in the taper hole of standard cone by hand-held light pen, slowly rotate light pen, CCD camera absorbs the light pen image of different positions and pose, and pass to computing machine by gigabit network cable and process in real time, by image filtering, Threshold segmentation, black and white upset, Contour extraction and least square ellipse matching, obtain all reference mark centre coordinate;

Second step: CCD camera is calibrated in advance, utilize center, reference mark from the coordinate camera coordinates system to ideal the perspective projection relation as plane, and the orthogonality of rotation matrix, can be solved by Gauss-Newton iteration method and rotate translation matrix R and T;

3rd step: because every width image can obtain 3 nonlinear equations, optimized variable X has 6 unknown numbers, therefore the initial value of X can be calculated by images more than two width;

4th step: after gathering n width image, namely can obtain the Nonlinear System of Equations f containing n equation _i(x, y, z, u, v, w)=0, i=1,2, L, n, utilize the generalized inverse of least square solution to solve this system of equations;

5th step: carry out convergence and judge, during the absolute difference < 0.01 of adjacent two near-optimal solution, stops iterative computation, by (x, y, z) in the optimized variable X that obtains for the last time ^tas the coordinate figure of gauge head center under light pen coordinate system, the coordinate figure of transformer center under light pen coordinate system can be obtained.

The present invention is the self-calibration utilizing the feature of system itself to realize transformer center (i.e. light pen gauge head), use CCD camera picked-up light pen image, and be transferred to computing machine and process in real time, camera transmission projection relation acquisition light pen coordinate is utilized to be tied to the rotation translation matrix of camera coordinates system, and set up Nonlinear System of Equations, the solution of the Nonlinear System of Equations asked by the generalized inverse of least square is the coordinate of center under light pen coordinate system of gauge head.This algorithm is by force ageing, simple to operate, easily realizes, fast stable, can realize high-precision three-dimensional coordinates measurement in measure field help system.

Accompanying drawing explanation

Fig. 1 is in the portable coordinate measuring machine of light pen, image acquisition schematic diagram, the slowly rotation light pen of left-right and front-back during collection.

Fig. 2 is perspective projection schematic diagram, is the basis asking for image rotational transformation matrix.

Embodiment

Technical scheme of the present invention is further illustrated below in conjunction with specific embodiment.This programme can realize utilizing the portable coordinate measuring machine of light pen to demarcate transformer center, by realizing the position finding of light pen gauge head.

Specific implementation process is:

(1) put up system and the relative position of fixed camera and standard cone, light pen gauge head is placed in the vertebral foramen of standard cone, and is fixed on transformer center and lights LED light target reference mark, prepares to start staking-out work;

(2) by the rotation slowly of manual operation light pen left-right and front-back, CCD camera pickup image is transferred to computing machine by gigabit network cable and processes in real time, obtains all reference mark and is calculating every width image corresponding R, T as the coordinate in plane.Calculating the coordinate initial value of gauge head center under light pen coordinate system by 6 width images is (77.153 ,-21.945 ,-117.865);

(3) continue gather piece image and be transferred to computing machine, according to the projection projection relation of camera coordinates system and desirable photo coordinate system, and light pen gauge head center unchangeability under camera coordinates system and light pen coordinate system, asking for the coordinate of gauge head center under light pen coordinate system is (76.411,-20.928 ,-118.412).This coordinate figure and initial value are deducted mutually absolute value for (0.753,1.017,0.547), discovery can not meet convergent requirement (the absolute difference < 0.01 of adjacent two near-optimal solution), then continue to gather image.Often increase piece image, just carry out an iterative computation optimization variable X=(x, y, z, u, v, w), and do and once restrain judgement;

(4) after being calculated by 210 width images, the coordinate figure obtaining last twice is respectively: (75.103 ,-24.258 ,-120.121) and (75.104,-24.260,-120.123), carry out convergence judgement and meet the demands, termination of iterations calculates, complete staking-out work, by (75.104 ,-24.260 ,-120.123) as the coordinate of transformer center at light pen coordinate system.

Above to invention has been exemplary description; should be noted that; when not departing from core of the present invention, any simple distortion, amendment or other those skilled in the art can not spend the equivalent replacement of creative work all to fall into protection scope of the present invention.

Claims (2)

1. utilize the method that the portable coordinate measuring machine of light pen is demarcated transformer center, it is characterized in that, select gauge head center to control in transformer center, if gauge head center is respectively (u with the coordinate of light pen coordinate system under camera coordinates system, v, w) ^t, (x, y, z) ^t.Be tied to the rotation translation relation of camera coordinates system from light pen coordinate according to spatial point, known:

$\left[\begin{array}{c}x\\ y\\ z\end{array}\right]=\left[\mathrm{RT}\right]\&CenterDot;\left[\begin{array}{c}u\\ v\\ w\\ 1\end{array}\right]---\left(1\right)$

Rotate translation matrix R and T can by camera Perspective transformation model and newton-Gaussian processes solve and obtain; If when light pen turns to i-th position, the actual coordinate of gauge head center under camera coordinates system is (ui, vi, wi) ^t, ideal value is (u, v, w) ^t, then can obtain optimization objective function:

$g\left(X\right)=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\left(f_i\right)}^2---\left(2\right)$

Wherein $f_i(x,y,z,u,v,w)=\sqrt{{(u_i-u)}^2+{(v_i-v)}^2+{(w_i-w)}^2},$ Optimized variable X=(x, y, z, u, v, w), the i.e. coordinate of gauge head center under light pen coordinate system and camera coordinates system;

The Nonlinear System of Equations of system is:

fi(x，y，z，u，v，w)＝0i＝1，2，L，n?(3)

Use the generalized inverse of least square solution to solve this system of equations, corresponding coordinate (u, v, w) can be obtained ^t, (x, y, z) ^t.

2. the method utilizing the portable coordinate measuring machine of light pen to demarcate transformer center according to claim 1, is characterized in that, specifically, carry out according to following step:

The first step: CCD camera and standard cone are all fixed, adjustment relative position makes light pen be imaged on CCD camera as plane centre position, and under certain amplitude is rocked, the image at all light target mark reference mark still can ensure presenting as in plane; Gauge head is placed in the taper hole of standard cone by hand-held light pen, slowly rotate light pen, CCD camera absorbs the light pen image of different positions and pose, and pass to computing machine by gigabit network cable and process in real time, by image filtering, Threshold segmentation, black and white upset, Contour extraction and least square ellipse matching, obtain all reference mark centre coordinate;

Second step: CCD camera is calibrated in advance, utilize center, reference mark from the coordinate camera coordinates system to ideal the perspective projection relation as plane, and the orthogonality of rotation matrix, can be solved by Gauss-Newton iteration method and rotate translation matrix R and T;

3rd step: because every width image can obtain 3 nonlinear equations, optimized variable X has 6 unknown numbers, therefore the initial value of X can be calculated by images more than two width;

4th step: after gathering n width image, namely can obtain the Nonlinear System of Equations f containing n equation _i(x, y, z, u, v, w)=0, i=1,2, L, n, utilize the generalized inverse of least square solution to solve this system of equations;

5th step: carry out convergence and judge, during the absolute difference < 0.01 of adjacent two near-optimal solution, stops iterative computation, by (x, y, z) in the optimized variable X that obtains for the last time ^tas the coordinate figure of gauge head center under light pen coordinate system, the coordinate figure of transformer center under light pen coordinate system can be obtained.