CN101424551B - Active vision non-contact type servomechanism parameter measurement method and apparatus thereof - Google Patents

Abstract

The invention provides an active vision non-contact servo mechanism parameter measuring device, consisting of a measuring screen, a servo mechanism mounting platform, an image acquiring and processing system, and a red light laser light source, wherein a servo mechanism to be detected is provided with the red light laser light source which is positioned on the servo mechanism mounting platform and is arranged in front of the measuring screen, a digital camera is arranged behind the measuring screen to image on the screen. Firstly, the device shoots a picture of a gridiron pattern on the measuring screen by the camera which is demarcated; secondly, the servo mechanism controls a main frame to give a command so as to control the rotation of the servo mechanism to be detected, a computer extracts laser point coordinates of the image, the rotational angle at each moment of the servo mechanism to be detected is calculated and recorded in real time, the motion parameters of the servo mechanism to be detected such as the angular velocity, the pointing accuracy, and the overshoot are calculated by the rotational angle; the measuring method is simple, convenient and flexible, and the device and the measuring method realize the measurement in real time and with high accuracy of the movement parameters of a biaxial servo mechanism through the non-contact way.

Description

Active vision non-contact type servomechanism parameter measurement method and device thereof

(1) technical field

The present invention relates to a kind of active vision non-contact type servomechanism parameter measurement method and device thereof, by contactless mode, it has realized the pointing accuracy of two servo control mechanisms, angle range, angular velocity, angular acceleration, the isoparametric real-time high-precision of overshoot are measured.Belong to technical field of computer vision.

(2) background technology

Servo control mechanism is a kind of mechanical hook-up that is widely used in many fields, and as in equipment such as satellite antenna, radar antenna, wherein the performance parameter to servo control mechanism has strict requirement.Traditional measuring method is at each corner and angular velocity of independent measurement, is divided into the mechanical measuring means of contact and contactless measuring method.These methods are not only installed complexity, change the structure of system, and more crucial be the parameter of each rotating shaft of independent measurement, the precision of total system can not be described.Because have mechanical clearance in the gearing of servo control mechanism, so there are error in actual sensing and the vector determined by two corners.Therefore the traditional measuring method sensing that can't measure servo control mechanism reality.

Computer vision is to obtain location to the objective world, measurement, a cognitive research field by analysis image, along with development of technology and development, is applied to some field in the engineering in recent years gradually.Existing literature search is found:

1. U.S. Patent number, US7,204,596B2, title: Projector with Tilt Angle MeasuringDevice, the laser beam that plural laser instrument produces around this patent utilization projector lens is incident upon on the screen, resolves the angle of inclination of projector by the relative position relation of luminous point in the photographic images.This patent is applied to measure the inclination angle of stationary body, is not suitable for kinetic measurement.

2. Chinese patent application number: 200610029122.9, based on the rotation-speed measuring device of computer vision, this patent is gathered the rotation blurred picture of testee, and the unique point on the object is fuzzy to be camber line, stretching after treatment is straight-line segment, measures length of straigh line and calculates rotating speed.This method can only be surveyed the object of single shaft rotation, can't be applied to the servo measuring system of multiaxis rotation.And be subjected to camera shutter time and resolution constraint, measurement range and precision are not high.

3. Chinese patent application number: 200610010435.X, title: contactless three-axle air floating table corner measuring apparatus and measuring method thereof, the patent readme is " utilize theory on computer vision and in conjunction with measurement target drone and ccd video camera mount message, calculate the rotational parameters of air floating table table top ".This patent mainly contains following weak point:

Video camera and laser instrument all need to be installed on the testee, can't use the demanding occasion of load weight;

Adopt colour TV camera, compare, under the situation of same image data amount, can reduce the resolution of image with B;

Rely on the rotation angle of measuring mounted LEDs lamp measurement air floating table on the target, the angle measurement scope is limited in the very little scope.

Because above limiting factor, this patent can't be applied in the accurate fields of measurement of big angle range, high-revolving servomechanism installation kinematic parameter.

(3) summary of the invention

(1) purpose

The object of the present invention is to provide a kind of active vision non-contact type servomechanism parameter measurement method and device thereof, it has overcome the shortcoming and defect of traditional contact measurement method, can measure each kinematic parameter of servo control mechanism, and its outer corner measurement scope and measuring accuracy are applied widely far above existing contactless measurement process.

(2) technical scheme

One, a kind of active vision non-contact type servomechanism parameter measurement device, it constitutes by measuring screen, servo control mechanism mounting platform, image acquisition and disposal system, red laser light source: the red laser light source is housed on servo control mechanism to be measured, it place on the servo control mechanism mounting platform and be placed in measure screen before, be placed with digital camera to screen imaging at servo control mechanism to be measured rear, view data is sent to Computer Processing through image pick-up card.

Workflow is: at first by the gridiron pattern pattern on the video camera photographed screen, to camera calibration; Give an order by the servo control mechanism main control system then and control servo rotation, computing machine extracts laser spots coordinate in the image, result in conjunction with camera calibration, calculate and write down servo control mechanism to be measured in real time at each corner constantly, calculate servo control mechanism kinematic parameters to be measured such as angular velocity, pointing accuracy, overshoot by corner.

1. measurement screen

The effect of measuring screen is to receive laser beam, makes the video camera of photographed screen can capture laser spots.For the three-dimensional coordinate that calculates luminous point provides a constraint, promptly only need calculate the three-dimensional coordinate that luminous point two coordinates in the two-dimensional coordinate system on screen just can obtain luminous point simultaneously.This constraint condition can avoid using the binocular vision system of two video cameras, has not only reduced system cost, and is easy to use, and precision is better than unconfined biocular systems.Because screen is as a constraint of measuring in calculating, so the screen plane degree is had certain requirement.

As an improvement of the present invention, in vision measurement, adopt the splicing of polylith screen board, not only widened the scope of measurement of angle greatly, improved the uneven phenomenon of imaging resolution in the plane simultaneously.The design of screen need be considered numerous factors, comprises bulk that measuring error, measurement environment allow and realizability etc.After taking all factors into consideration, camera parameters 2/3 inch CCD, lens focus 12mm, video camera apart from screen 5m about, with this understanding, screen height is designed to 1.6m.During the screen angle design, need to consider error component.Fig. 8 is a horizontal sectional view, and when horizontally rotating, laser spots E moves on screen, the respective imaging angle when servo

Defined parameters , it is worth more little explanation

With ψ more near linear relationship, thereby it is more little to quantize the error bring.According to geometric relationship, can derive

Wherein α is 1/2 of video camera horizontal field of view angle, is to have decided parameter; θ is half angle of screen wall 101 and 102.When θ changes, calculate corresponding parameters var successively, obtaining optimal angle is 35 °, but considers processing and design conveniently, finally designing angle theta is 45 °.Similarly, the λ angle among vertical cross-section diagram Fig. 9 is designed to 30 °.

As a further improvement on the present invention, when applying the present invention to outdoor portable measuring equipment, measuring screen design is light foldable structure, is convenient to transportation, installs and uses.The supporting construction of screen is the bulb grid structure, lightly is easy to dismounting; Use a plurality of web members that revolve to connect screen on the grid structure, can regulate the distance between rack and the screen regional, to satisfy the requirement of screen plane degree; Screen adopts plastic honeycomb board to make core, and fiberglass is pasted on the surface, and is both light, satisfies the rigidity Design requirement again.

2. servo control mechanism mounting platform

The servo control mechanism mounting platform is the support platform of servo control mechanism to be measured.The purpose of using the servo control mechanism mounting platform is in order to guarantee servo control mechanism installation to be measured in place, to make laser beam not exceed the screen boundary.Determine the relativeness between servo coordinate system and the screen coordinate system simultaneously, be used to calculate servo corner.

Servo control mechanism mounting platform among the present invention needed to carry out accurate adjustment before servo control mechanism to be measured is measured.Its adjusting process is: builds a station at the transit more than 0.1/1000 with two measuring accuracy, and collocation special software platform, utilize transit to regulate the flatness of servo control mechanism mounting platform, the flatness precision of guaranteeing the servo control mechanism mounting platform is less than 1/500; Servo control mechanism to be measured is installed on the servo control mechanism mounting platform, utilizes transit to determine servo control mechanism to be measured and measures relative position relation between the screen.

As an improvement of the present invention, the servo control mechanism mounting platform is designed to light, demountable structure, is applicable to outdoor portable measuring equipment.

3. image acquisition and disposal system

Image acquisition and disposal system are the key components of this patent, and it is made up of high resolution digital camera, the department of computer science image measurement software of unifying.The hardware of computer system comprises image pick-up card, display and order input equipment, image measurement software is the realization part of measuring the servo control mechanism kinematic parameter, is made up of demarcating module, image processing module, kinematic parameter computing module and data management module.

Image pick-up card is installed in the mainframe box of computer system, and digital camera is connected to by stube cable on the input interface of image pick-up card, and image measurement software is installed on the operating system platform of computer system.

The present invention adopts the industrial digital CCD B of high resolving power, two-forty, compares with colour TV camera, and under same data rate situation, the resolution of B is higher about 1.7 times than colour TV camera.Under the data rate certain condition, resolution of video camera and frame rate are contradictory relations, and native system had both required high-acruracy survey, need enough frame rate to solve the high speed problems of measurement again, after taking all factors into consideration, select resolution 1390 * 1024, the B of frame rate 30fps.

Select the programmable function of shutter parameter in addition for use, image processing module by software, can regulate shutter speed automatically, make and have only the imaging in image of high-brightness laser point, eliminate the conditions of streaking that motion blur produces simultaneously, reduce the difficulty of luminous point recognition and tracking, simplify and handle, thereby reach the real-time requirement.

Two, a kind of non-contact type servomechanism parameter measurement method, its step is as follows:

1. Camera calibration

Video camera is placed in correct position, and the visual field can cover whole measurement screen, and the upper edge that guarantees observed measurement screen in the visual field along with the upper edge of rectangular field along parallel, by the calibration algorithm of software video camera is demarcated;

Listed the coordinate system that relates in the servo motion measurement method of parameters among Fig. 4,101,102 and 103 is three curtain walls measuring screen, and the corresponding coordinate system of each curtain wall is respectively O ₁(x ₁, y ₁, z ₁), O ₂(x ₂, y ₂, z ₂) and O ₃(x ₃, y ₃, z ₃), the coordinate system O of servo control mechanism to be measured _s(x _s, y _s, z _s) initial point at 101 and 102 equidistant points, and x _sAxle and z _sOn equidistant point, z _sAnd y ₁, y ₂Axle is parallel, and servo control mechanism to be measured is around z _sShaft angle is called the position angle, around y _sShaft angle is called the angle of pitch, around x _sShaft angle is called roll angle; O _i(x _i, y _i) be image coordinate system.

The method of demarcating is as follows: extract the angular coordinate in the gridiron pattern in 101,102 and 103 in image, calibration algorithm (the Z.Zhang.A Flexible New Technique for CameraCalibration.IEEE Trans.on Pattern Analysis and Machine Intelligence that adopts Zhang Zhengyou to propose, 22 (11): 1330-1334,2000.), according to the image coordinate and the screen coordinate of angle point, video camera is demarcated.Thereby determined image coordinate system O _s(x _s, y _s, z _s) and screen coordinate system O ₁(x ₁, y ₁, z ₁), O ₂(x ₂, y ₂, z ₂) and O ₃(x ₃, y ₃, z ₃) transformational relation

2. light source is demarcated

Before each measurement beginning, servo control mechanism to be measured is reset to the initial position at zero point, image measurement software extracts the luminous point in the image automatically, and obtains the initial position at zero point of luminous point;

3. brightness is demarcated

The view data that collects is by analysis adjusted shutter speed to the measurement requirement scope, gets rid of most backgrounds, only keeps the luminous point of high brightness;

4. measure in real time

Send instruction by the servo control mechanism main control system, servo control mechanism to be measured is rotated, start working by command input system control survey system simultaneously; The computer system calling graph is as the image of the real-time acquisition camera of data acquisition module, after the figure image intensifying is carried out in the process pre-service, cut apart the identification luminous point, and carry out luminous point and extract location and luminous point recognition and tracking, and calculate the sub-pix coordinate of luminous point in image in real time, and reconstruct its three-dimensional coordinate by the image coordinate of luminous point, calculate corresponding optical axis vector, be scaled the corner of servo control mechanism to be measured at last, output in real time shows on display;

The three-dimensional reconstruction of luminous point coordinate, method is as follows:

If image coordinate (u, v) ^T, corresponding screen coordinate (X, Y, Z) ^T, imaging system is as follows:

$s\left[\begin{array}{c}u\\ \mathrm{<figure-callout\; id="1"\; label="v"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">v</figure-callout>}\\ 1\end{array}\right]=\left[\begin{array}{ccc}{f}_x& 0& c_x\\ 0& f_{\mathrm{<figure-callout\; id="0"\; label="y\; c\; y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">y</figure-callout>}}& c_y{}_{}\\ 0& 0& 1\end{array}\right]\&CenterDot;\left[\begin{array}{ccc}{r}_{11}& r_{12}& r_{13}\\ r_{21}& r_{22}& r_{23}\\ r_{31}& r_{32}& r_{33}\end{array}\right]\&CenterDot;\left[\begin{array}{c}X\\ Y\\ Z\end{array}\right]+\left[\begin{array}{c}{t}_x\\ t_y\\ t_z\end{array}\right]---\left(1\right)$

Wherein S is a scale factor, $A=\left[\begin{array}{ccc}{f}_x& 0& c_x\\ 0& f_{\mathrm{<figure-callout\; id="0"\; label="y\; c\; y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">y</figure-callout>}}& c_y{}_{}\\ 0& 0& 1\end{array}\right]$ Be the camera intrinsic parameter matrix, $R=\left[\begin{array}{ccc}{r}_{11}& r_{12}& r_{13}\\ r_{21}& r_{22}& r_{23}\\ r_{31}& r_{32}& r_{33}\end{array}\right]$ Be rotation matrix, $t=\left[\begin{array}{c}{t}_x\\ t_y\\ t_z\end{array}\right]$ Be offset vector, R and t are referred to as external parameters of cameras.

Because measuring screen is the plane, thus z ≡ 0 wherein, so equation has unique solution, by (u, v) ^TSolve (X, Y, 0) ^TLinear computing method are suc as formula shown in (2) and (3),

$\left[\begin{array}{c}x\\ y\\ z\end{array}\right]=A^{-1}\&CenterDot;\left[\begin{array}{c}u\\ v\\ 1\end{array}\right]---\left(2\right)$

$\left[\begin{array}{c}X\\ \mathrm{<figure-callout\; id="0"\; label="Y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">Y</figure-callout>}\\ 0\end{array}\right]=R^{-1}\left[\begin{array}{c}x/z\\ y/z\\ 1\end{array}\right]-t---\left(3\right)$

Wherein $\left[\begin{array}{c}x\\ y\\ z\end{array}\right]$ Be the coordinate in the camera coordinate system, this is to be calculating under the linear case in the supposition system.Be considered to the distortion in the picture, more accurate computing method are

$\left[\begin{array}{c}x\\ y\\ z\end{array}\right]=A^{-1}\&CenterDot;\left[\begin{array}{c}u\\ v\\ 1\end{array}\right]---\left(2\right)$

$\left\{\begin{array}{c}x=\tilde{x}(1+k_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+k_2{r}^4)+2p_1\tilde{x}\tilde{y}+({\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+2{\tilde{x}}^2)\\ y=\tilde{y}(1+k_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+k_2{r}^4)+2p_2\tilde{x}\tilde{y}+p_1({\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+2{\tilde{y}}^2)\end{array}\right.---\left(4\right)$

Wherein ${\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2={\tilde{x}}^2+{\tilde{y}}^2$

$\left[\begin{array}{c}\mathrm{<figure-callout\; id="0"\; label="X\; Y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">X</figure-callout>}& \\ Y\\ 0\end{array}\right]=R^{-1}\left[\begin{array}{c}\tilde{x}/z\\ \tilde{y}/z\\ 1\end{array}\right]-t---\left(5\right)$

X in the formula (4) and y are the revised coordinates of distortion, k ₁And k ₂Be coefficient of radial distortion, p ₁And p ₂Be the tangential distortion coefficient, obtain by camera calibration.Solve x and y for people (5) formula by equation, finally separated.In actual development process, from the linear computation model nonlinear model finally of beginning, the screen coordinate positioning error is reduced to about 1mm from 10mm, has improved an order of magnitude.

If being tied to the rotation matrix of servo control mechanism coordinate system to be measured by screen coordinate is R _s, offset vector is t _s, the coordinate of luminous point under screen coordinate system is (X, Y, 0) ^T, the coordinate under servo control mechanism coordinate system to be measured is (X _s, Y _s, Z _s) ^T, then luminous point at the coordinate of screen coordinate system OXYZ and luminous point at servo control mechanism coordinate system O to be measured _sX _sY _sZ _sCoordinate between transformational relation provide by (6) formula:

$\left[\begin{array}{c}{X}_s\\ Y_s\\ Z_s\end{array}\right]=R_s\left[\begin{array}{c}\mathrm{<figure-callout\; id="0"\; label="X\; Y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">X</figure-callout>}& \\ Y\\ 0\end{array}\right]+t_s---\left(6\right)$

Can calculate luminous point thus at servo coordinate system O to be measured _sX _sY _sZ _sUnder coordinate (X _s, Y _s, Z _s) ^TThen the rotational angle of servo control mechanism to be measured can be calculated by formula (7), (8).Wherein, the position angle of servo control mechanism to be measured is:

${\mathrm{\&theta;}}_A=\arctan \left(\frac{Y_s}{X_s}\right)---\left(7\right)$

The angle of pitch of servo control mechanism to be measured is:

${\mathrm{\&theta;}}_P=\arctan \left(\frac{Z_s}{X_s}\right)---\left(8\right)$

5. subsequent treatment

After measuring end in real time, the luminescent spot track data of the automatic analytic record of software, divide different phase according to mode of motion, point to state, transient motion stage, overshoot stage as static state, carrying out real-time parameter calculates, calculate the kinematic parameter under the various stages, finally export the parameter such as pointing accuracy, rotational angular velocity, angle of rotation acceleration, angle range, overshoot, settling time of servo control mechanism to be measured; The test rating that contrast is set judges whether servo control mechanism to be measured reaches requirement.

6. data management

After the end of test (EOT), the each result of calculation of measuring of record can be inquired about at any time, be added up in database, and can reappear measuring process according to the luminescent spot track coordinate of record, is convenient to the reviewer and the designer analyzes data, searches technical failure.

(3) advantage and effect

1. contactless, low load

Do not contact testee in the measuring process; The additional load of testee has only LASER Light Source, and is in light weight, has only tens to restrain tens grams, applied widely;

2. angle measurement wide ranges

Under the standard conditions, use three curtain walls to form and measure screen, use single camera, the position angle effective range is-90 °～+ 90 °, and the angle of pitch is-15 °～+ 90 °; Under the situation that increases curtain wall and number of cameras, the measurement range of the position angle and the angle of pitch can also further improve.

3. wide dynamic range

Under the image acquisition rates of 30fps, the angle measurement scope under above-mentioned standard conditions, 0～300 °/s of effective range of angular velocity omega, 0～1200 °/s of angular acceleration scope ²

4. simplified image is handled

Adopt the programmable digital camera of shutter parameter, demarcate by the brightness in the software, can regulate aperture time automatically according to concrete environment, reduce background luminance, outstanding luminous point is convenient to extract; High in addition shutter speed can be eliminated the conditions of streaking that motion blur brings, and simplifies the luminous point extraction algorithm, and the precision height;

5. measuring accuracy height, method is flexible

In measuring process of the present invention, the relative position relation of video camera and measurement screen is fixed, so in case after demarcating, the corresponding relation of measuring screen and image is accurately constant, can not change along with the carrying out of measuring as the measuring system of some video camera with object of which movement.Therefore by image coordinate in the conversion of screen coordinate, can use non-linear imaging model, consider radial distortion and tangential distortion coefficient in the optical system, can obtain high-precision result.

Distance can obtain different angle measurement scope and measuring accuracy between adjusting servo control mechanism and the measurement screen, and when distance increased, the angle measurement scope reduced, the measuring accuracy raising; Distance near the time, the angle measurement scope increases, precision reduces.Therefore can select the measurement range and the precision of needs as required flexibly.For example in standard angle measurement scope, the precision of the position angle and the angle of pitch can reach 0.1 °; And when adjusting to angle measurement scope ± 12 °, precision can reach 0.01 °.

6. the automaticity height is easy to use

Video camera does not need to install, and can place flexibly according to actual environment, and indoor, outdoor measurement all is suitable for; The optical parametric of video camera uses the related algorithm of Flame Image Process to calculate automatically and obtains, and measuring process does not need to intervene yet, and the automaticity height is easy to use.

(4) description of drawings

Fig. 1 structural representation of the present invention

Fig. 2 function block diagram of the present invention

Fig. 3 measuring process synoptic diagram

The coordinate system synoptic diagram that Fig. 4 relates to

Fig. 5 demarcating module synoptic diagram

Fig. 6 image processing module synoptic diagram

Fig. 7 kinematic parameter computing module synoptic diagram

Fig. 8 measures the screen level sectional view

Fig. 9 measures the screen vertical cross-section diagram

Symbol description is as follows among the figure:

1 measures screen; 2 servo control mechanism mounting platforms; 3 red laser light sources; 4 servo control mechanisms to be measured; 5 digital cameras; 6 computer systems; 7 image pick-up cards; 8 displays; 9 order input equipments; 10 demarcating modules; 11 image processing modules; 12 kinematic parameter computing modules; 13 data management modules; 14 camera calibrations; 15 light sources are demarcated; 16 brightness are demarcated; 17 image data acquisition; 18 pre-service; 19 luminous points extract the location; 20 luminous point recognition and trackings; 21 three-dimensional reconstructions; 22 real-time parameters calculate; 23 subsequent treatment; 24 servo control mechanism main control systems;

101 screen walls 1; 102 screen walls 2; 103 screen walls 3;

O ₁(x ₁, y ₁, z ₁) screen wall 1 coordinate system; O ₂(x ₂, y ₂, z ₂) screen wall 2 coordinate systems;

O ₃(x ₃, y ₃, z ₃) screen wall 3 coordinate systems; O _s(x _s, y _s, z _s) servo control mechanism coordinate system to be measured;

O _i(x _i, y _i) image coordinate system.

(5) embodiment

See Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, shown in Figure 7, it specifically implements as follows:

(1) a kind of active vision non-contact type servomechanism parameter measurement device, it constitutes by measuring screen 1, servo control mechanism mounting platform 2, image acquisition and disposal system, red laser light source 3: on servo control mechanism 4 to be measured red laser light source 3 is housed, it place on the servo control mechanism mounting platform 2 and be placed in measure screen 1 before, be placed with 5 pairs of digital cameras at servo control mechanism to be measured 4 rears and measure screen 1 imaging, view data is sent to computer system 6 through image pick-up card 7 and handles.

Image acquisition and disposal system are made up of high resolution digital camera 5, computer system 6 and image measurement software.The hardware of computer system 6 is formed and is comprised image pick-up card 7, display 8 and order input equipment 9, image measurement software is the realization part of measuring servo control mechanism 4 kinematic parameters to be measured, is made up of demarcating module 10, image processing module 11, kinematic parameter computing module 12 and data management module 13.Image pick-up card 7 is installed in the mainframe box of computer system 6, and digital camera 5 is connected on the input interface of image pick-up card 7 by stube cable.Image measurement software is installed on the operating system platform of computer system 6.

Workflow is as follows: at first adjust 5 pairs of gridiron pattern patterns of measuring on the screen 1 of video camera and carry out complete shooting, start 10 pairs of video cameras 5 of demarcating module then and demarcate and preserve nominal data; Give an order by servo control mechanism main control system 24 again and control servo control mechanism 4 rotations to be measured; When servo control mechanism 4 to be measured rotates, laser spots coordinate in the image that image processing module 11 continuous extraction video cameras 5 photograph, data in conjunction with 5 demarcation of 10 pairs of video cameras of demarcating module, calculate and write down servo control mechanism 4 to be measured in real time at each photographic images corner constantly, kinematic parameter computing module 12 is by relatively calculating servo control mechanism 4 to be measured at difference corner constantly, thereby obtains the kinematic parameter of servo control mechanisms 4 to be measured such as angular velocity, pointing accuracy, overshoot.

(2) a kind of active vision non-contact type servomechanism parameter measurement method, its step is as follows:

1. camera calibration 14

Video camera 5 is placed in correct position, and the visual field can cover whole measurement screen 1, and the upper edge that guarantees observed measurement screen 1 in the visual field along with the upper edge of rectangular field along parallel, by the calibration algorithm of software video camera 5 is demarcated;

Listed the coordinate system that relates in the servo motion measurement method of parameters among Fig. 4,101,102 and 103 is three curtain walls measuring screen 1, and the corresponding coordinate system of each curtain wall is respectively O ₁(x ₁, y ₁, z ₁), O ₂(x ₂, y ₂, z ₂) and O ₃(x ₃, y ₃, z ₃), the coordinate system O of servo control mechanism 4 to be measured _s(x _s, y _s, z _s) initial point at 101 and 102 equidistant points, and x _sAxle and z _sOn equidistant point, z _sAnd y ₁, y ₂Axle is parallel.Servo control mechanism to be measured 4 is around z _sShaft angle is called the position angle, around y _sShaft angle is called the angle of pitch, around x _sShaft angle is called roll angle; O _i(x _i, y _i) be image coordinate system.

The method of demarcating is as follows: extract the angular coordinate in the gridiron pattern in 101,102 and 103 in image, calibration algorithm (the Z.Zhang.A Flexible New Technique for CameraCalibration.IEEE Trans.on Pattern Analysis and Machine Intelligence that adopts Zhang Zhengyou to propose, 22 (11): 1330-1334,2000.), according to the image coordinate and the screen coordinate of angle point, video camera 5 is demarcated.Thereby determined image coordinate system O _s(x _s, y _s, z _s) and screen coordinate system O ₁(x ₁, y ₁, z ₁), O ₂(x ₂, y ₂, z ₂) and O ₃(x ₃, y ₃, z ₃) transformational relation.

2. light source demarcates 15

Before each measurement beginning, servo control mechanism 4 to be measured is reset to the initial position at zero point, image measurement software extracts the luminous point in the image automatically, and obtains the initial position at zero point of luminous point;

3. brightness demarcates 16

The view data that collects is by analysis adjusted shutter speed to the measurement requirement scope, gets rid of most backgrounds, only keeps the luminous point of high brightness;

4. measure in real time

Send instruction by servo control mechanism main control system 24, servo control mechanism 4 to be measured is rotated, start working by command input system 9 control survey systems simultaneously; Computer system 6 calling graphs are as the image of data acquisition module 17 real-time acquisition camera 5, after the figure image intensifying is carried out in process pre-service 18, cut apart the identification luminous point, and carry out luminous point and extract location 19 and luminous point recognition and tracking 20, calculate the sub-pix coordinate of luminous point in image in real time; Image coordinate by luminous point reconstructs its three-dimensional coordinate, calculates corresponding optical axis vector, is scaled the corner of servo control mechanism 4 to be measured at last, and output shows on display 8 in real time;

The three-dimensional reconstruction 21 of luminous point coordinate, method is as follows:

If image coordinate (u, v) ^T, corresponding screen coordinate (X, Y, Z) ^T, imaging system is as follows:

$s\left[\begin{array}{c}u\\ v\\ 1\end{array}\right]=\left[\begin{array}{ccc}{f}_x& 0& c_x\\ 0& f_{\mathrm{<figure-callout\; id="0"\; label="y\; c\; y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">y</figure-callout>}}& c_y{}_{}\\ 0& 0& 1\end{array}\right]\&CenterDot;\left[\begin{array}{ccc}{r}_{11}& r_{12}& r_{13}\\ r_{21}& r_{22}& r_{23}\\ r_{31}& r_{32}& r_{33}\end{array}\right]\&CenterDot;\left[\begin{array}{c}X\\ Y\\ Z\end{array}\right]+\left[\begin{array}{c}{t}_x\\ t_y\\ t_z\end{array}\right]---\left(1\right)$

Wherein S is a scale factor, $A=\left[\begin{array}{ccc}{f}_x& 0& c_x\\ 0& f_{\mathrm{<figure-callout\; id="0"\; label="y\; c\; y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">y</figure-callout>}}& c_y{}_{}\\ 0& 0& 1\end{array}\right]$ Be video camera 5 intrinsic parameter matrixes, $R=\left[\begin{array}{ccc}{r}_{11}& r_{12}& r_{13}\\ r_{21}& r_{22}& r_{23}\\ r_{31}& r_{32}& r_{33}\end{array}\right]$ Be rotation matrix, $t=\left[\begin{array}{c}{t}_x\\ t_y\\ t_z\end{array}\right]$ Be offset vector, R and t are referred to as video camera 5 outer parameters.

Because measuring screen 1 is the plane, thus Z ≡ 0 wherein, so equation has unique solution, by (u, v) ^TSolve (X, Y, 0) ^TLinear computing method are suc as formula shown in (2) and (3),

$\left[\begin{array}{c}x\\ y\\ z\end{array}\right]=A^{-1}\&CenterDot;\left[\begin{array}{c}u\\ v\\ 1\end{array}\right]---\left(2\right)$

$\left[\begin{array}{c}\mathrm{<figure-callout\; id="0"\; label="X\; Y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">X</figure-callout>}& \\ Y\\ 0\end{array}\right]=R^{-1}\left[\begin{array}{c}x/z\\ y/z\\ 1\end{array}\right]-t---\left(3\right)$

Wherein $\left[\begin{array}{c}x\\ y\\ z\end{array}\right]$ Be the coordinate in the camera coordinate system, this is to be calculating under the linear case in the supposition system.Be considered to the distortion in the picture, more accurate computing method are

$\left[\begin{array}{c}x\\ y\\ z\end{array}\right]=A^{-1}\&CenterDot;\left[\begin{array}{c}u\\ v\\ 1\end{array}\right]---\left(2\right)$

$\left\{\begin{array}{c}x=\tilde{x}(1+k_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+k_2{r}^4)+2p_1\tilde{x}\tilde{y}+({\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+2{\tilde{x}}^2)\\ y=\tilde{y}(1+k_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+k_2{r}^4)+2p_2\tilde{x}\tilde{y}+p_1({\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+2{\tilde{y}}^2)\end{array}\right.---\left(4\right)$

Wherein ${\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2008102278001E00011.png,H2008102278001E00031.png"\; state="\{\{state\}\}">r</figure-callout>}}^2={\tilde{x}}^2+{\tilde{y}}^2$

$\left[\begin{array}{c}\mathrm{<figure-callout\; id="0"\; label="X\; Y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">X</figure-callout>}& \\ Y\\ 0\end{array}\right]=R^{-1}\left[\begin{array}{c}\tilde{x}/z\\ \tilde{y}/z\\ 1\end{array}\right]-t---\left(5\right)$

In the formula (4)

With Be the revised coordinate of distortion, k ₁And k ₂Be coefficient of radial distortion, p ₁And p ₂Be the tangential distortion coefficient, obtained by camera calibration 14.Solve by equation With

For people (5) formula, finally separated.In actual development process, from the linear computation model nonlinear model finally of beginning, the screen coordinate positioning error is reduced to about 1mm from 10mm, has improved an order of magnitude.

If being tied to the rotation matrix of servo control mechanism coordinate system to be measured by screen coordinate is R _s, offset vector is t _s, the coordinate of luminous point under screen coordinate system be (X, Y, O) ^T, the coordinate under servo control mechanism coordinate system to be measured is (X _s, Y _s, Z _s) ^T, then luminous point at the coordinate of screen coordinate system OXYZ and luminous point at servo control mechanism coordinate system O to be measured _sX _sY _sZ _sCoordinate between transformational relation provide by (6) formula:

$\left[\begin{array}{c}{X}_s\\ Y_s\\ Z_s\end{array}\right]=R_s\left[\begin{array}{c}\mathrm{<figure-callout\; id="0"\; label="X\; Y"\; filenames="H2008102278001E00051.png"\; state="\{\{state\}\}">X</figure-callout>}& \\ Y\\ 0\end{array}\right]+t_s---\left(6\right)$

Can calculate luminous point thus at servo control mechanism coordinate system O to be measured _sX _sY _sZ _sUnder coordinate (X _s, Y _s, Z _s) ^TThen the rotational angle of servo control mechanism to be measured can be calculated by formula (7), (8).Wherein, the position angle of servo control mechanism to be measured is:

${\mathrm{\&theta;}}_A=\arctan \left(\frac{Y_s}{X_s}\right)---\left(7\right)$

The angle of pitch of servo control mechanism to be measured is:

${\mathrm{\&theta;}}_P=\arctan \left(\frac{Z_s}{X_s}\right)---\left(8\right)$

5. subsequent treatment 23

After measuring end in real time, the luminescent spot track data of the automatic analytic record of software, divide different phase according to mode of motion, point to state, transient motion stage, overshoot stage as static state, carry out real-time parameter and calculate 22, obtain the kinematic parameter under the various stages, finally export the parameter such as pointing accuracy, rotational angular velocity, angle of rotation acceleration, angle range, overshoot, settling time of servo control mechanism 4 to be measured; The test rating that contrast is set judges whether servo control mechanism 4 to be measured reaches requirement.

6. data management

After the end of test (EOT), the each result of calculation of measuring of record can be inquired about at any time, be added up in database, and can reappear measuring process according to the luminescent spot track coordinate of record, is convenient to the reviewer and the designer analyzes data, searches technical failure.

Claims (4)

1. active vision non-contact type servomechanism parameter measurement device, it is characterized in that: it constitutes by measuring screen, servo control mechanism mounting platform, image acquisition and disposal system, red laser light source, the red laser light source is housed on servo control mechanism to be measured, servo control mechanism to be measured place on the servo control mechanism mounting platform and be placed in measure screen before, be placed with digital camera at servo control mechanism to be measured rear to measuring screen imaging;

Described measurement screen is to make core with plastic honeycomb board, and the three dimensions shape that glass-reinforced plastic material is made is pasted on the surface, and it receives laser beam, makes the digital camera of taking the measurement screen can capture laser spots; The supporting construction of measuring screen is to use a plurality of web members that revolve to connect the bulb rack member of measuring screen;

The horizontal support platform that described servo control mechanism mounting platform is a servo control mechanism to be measured, servo control mechanism to be measured places the top of this mounting platform, utilize transit to determine servo control mechanism to be measured and measure relative position relation between the screen, thereby obtain the accurate three dimensional space coordinate of servo control mechanism to be measured;

Described image acquisition and disposal system are made up of digital camera, the department of computer science image measurement software of unifying; The hardware of this computer system comprises image pick-up card, display and order input equipment; This image measurement software is the combination of demarcating module, image processing module, parameter calculating module and data management module; Image pick-up card is installed in the mainframe box of computer system, digital camera is connected on the input interface of image pick-up card and is placed on servo control mechanism mounting platform rear by stube cable, image measurement software is installed on the operating system platform of computer system;

Digital camera is a resolution 1390 * 1024, the CCD B of frame rate 30fps;

The workflow of described active vision non-contact type servomechanism parameter measurement device is: at first take the gridiron pattern pattern of measuring on the screen by digital camera, to digital camera calibration; Give an order by the servo control mechanism main control system then and control servo control mechanism rotation to be measured, image processing module extracts the laser spots coordinate in the image that digital camera photographs continuously, in conjunction with the data of demarcating module to digital camera calibration, calculate and write down servo control mechanism to be measured in real time at each photographic images corner constantly, the kinematic parameter computing module is by relatively calculating servo control mechanism to be measured at difference corner constantly, thereby calculates angular velocity, pointing accuracy, overshoot.

2. a kind of active vision non-contact type servomechanism parameter measurement device according to claim 1, it is characterized in that: this measurement screen is to be spliced by the polylith screen board.

3. a kind of active vision non-contact type servomechanism parameter measurement device according to claim 1, it is characterized in that: this measurement screen is the folding portable structure.

4. a kind of active vision non-contact type servomechanism parameter measurement device according to claim 1, it is characterized in that: this servo control mechanism mounting platform is a demountable structure.

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