CN108675142B - Multi-height calibration measurement method and anti-diagonal-pulling and accurate positioning method for crane - Google Patents

Multi-height calibration measurement method and anti-diagonal-pulling and accurate positioning method for crane Download PDF

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CN108675142B
CN108675142B CN201810222013.1A CN201810222013A CN108675142B CN 108675142 B CN108675142 B CN 108675142B CN 201810222013 A CN201810222013 A CN 201810222013A CN 108675142 B CN108675142 B CN 108675142B
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crane
trolley
camera
target
deceleration
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CN108675142A (en
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汪小凯
吴庆祥
徐强
危刚
华林
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Wuhan University of Technology WUT
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Wuhan University of Technology WUT
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C15/00—Safety gear
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C13/00—Other constructional features or details
    • B66C13/16—Applications of indicating, registering, or weighing devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C3/00—Measuring distances in line of sight; Optical rangefinders
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/17—Mechanical parametric or variational design

Abstract

The invention discloses a monocular camera-based multi-height calibration measuring method and a crane diagonal-pulling prevention and accurate positioning method, based on a machine vision technology, accurate measurement of a target position of a monocular camera under different height conditions is realized through multi-height calibration, the multi-height calibration process specifically comprises the steps of dividing a camera depth of field range into a plurality of sections, equally dividing the camera field of view into a plurality of sections in each section of height range according to the transverse direction and the longitudinal direction, and establishing a mathematical model of a pixel distance and an actual distance at different heights by moving a target for a plurality of times in the transverse direction and the longitudinal direction in each section of depth of field variation range in the camera calibration process. The invention has high sensitivity, convenient implementation and strong robustness, greatly improves the operation safety and the working efficiency of the crane, and promotes the automatic, digital and intelligent development of the crane.

Description

Multi-height calibration measurement method and anti-diagonal-pulling and accurate positioning method for crane
Technical Field
The invention belongs to the technical field of crane safety control, and particularly relates to a monocular camera-based multi-height calibration measuring method and a crane diagonal-pulling prevention and accurate positioning method.
Background
The crane is used as a logistics transportation tool, can realize the hoisting and transportation of goods, especially large goods, saves manpower and material resources, greatly improves the working efficiency and promotes the development of economy. Meanwhile, along with the development of industrial automation and digitization level, especially the application of a frequency converter, the electrical automation level of the crane is continuously improved, and the operation stability and safety of the crane are further improved. Meanwhile, according to the practical application condition of the frequency converter on the crane, in the process of decelerating the crane running mechanism, the frequency converter realizes the slow stop of the running mechanism by changing the change rate of the running speed of the running mechanism, thereby reducing the speed change impact of the running mechanism and improving the running stability of the crane. Meanwhile, in the lifting process of the crane, the goods are obliquely pulled and hung, so that the load of the lifting mechanism is increased, and the service lives of a winding drum, a steel wire rope and the like of the lifting mechanism are shortened. Dangerous working conditions such as sliding, overturning, deflection and the like of the goods can be caused by the diagonal pulling and lifting of the goods, and the safety of surrounding equipment and workers is seriously threatened. The existing crane anti-diagonal tension control technology mainly limits the goods to rise in a diagonal tension state through limit switches such as photoelectric switches and resistance switches. This approach has not been able to meet the demands of crane rapidity and intelligence. Further, by analyzing the crane open-loop anti-swing algorithm, the open-loop anti-swing algorithm can restrain the load from swinging by controlling the operation of the crane big trolley, namely, the big trolley has a certain deceleration braking distance in the process of restraining the load from swinging. However, the existence of the deceleration distance will increase the uncertainty of the stop position of the crane, and in the control process of the traditional crane, workers control the crane to continuously adjust at a low speed to realize the accurate positioning of the load, thereby seriously reducing the working efficiency of the crane.
The development direction of the future factory is digital workshop and unmanned factory, the popularization rate of the digital workshop and intelligent factory is 20% by 2020, and the crane is a crucial ring, so that the automation and digitization for accurately positioning the crane become more important. Meanwhile, in order to restrain the deflection of the load, the open-loop anti-swing control algorithm of the crane is researched and applied in a large quantity. The control law of the open-loop anti-swing control algorithm is that the deflection of the load is restrained by controlling the movement of the large trolley, namely the deflection of the load is restrained by controlling the large trolley to move for a section of displacement in the acceleration process of the crane, or the deflection of the load is restrained by controlling the large trolley to move for a section of displacement in the acceleration process of the crane. Therefore, in order to restrain the deflection of the load, the large trolley runs for a shake-proof distance, and the application range of the crane open-loop shake-proof control algorithm is limited.
Disclosure of Invention
The invention aims to provide a multi-height calibration measuring method based on a monocular camera and a crane diagonal-pulling prevention and accurate positioning method.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a multi-height calibration measurement method based on a monocular camera comprises the following steps:
s1, selecting a monocular camera, and acquiring the following parameters: maximum height Δ l within the depth of field of the camera, maximum lateral field of view 2X of the camera, maximum longitudinal field of view 2Y of the camera, and maximum working distance l of the cameraH；
S2, placing the target in the visual field range and the depth of field range of the monocular camera, dividing delta l into H sections, wherein the height of each section is delta lhH1, 2, 3.. H, dividing half of the maximum transverse field of view X into m segments at each segment height, each segment having a transverse distance Δ XhiI 1, 2, 3.. m, dividing half of the maximum longitudinal field of view Y into n segments at each segment height, each segment having a longitudinal distance Δ Yhj，j＝1，2，3...n；
S3, at each height, according to the transverse movement direction from delta Xh1To Δ XhmMoving to respectively obtain the transverse distance delta u of the target imageshiFrom Δ Y in the direction of longitudinal movementh1To delta YhnMoving to respectively obtain the longitudinal distance delta v of the target imageshj；
S4, calibrating formula according to monocular camera
Figure GDA0002266538350000021
Solving the scale factor b and the camera internal parameter kxhiAnd kyhjInitial coordinates u in image coordinates expressed in physical units0And v0Measuring the field depth range of the monocular camera according to the solved calibration formula of the monocular cameraAnd the transverse distance delta X and the longitudinal distance delta Y of the object to be measured in the visual field range, wherein delta X is f (l)cm、Δu)，ΔY＝f(lcmΔ v), in which lhDistance between monocular camera and target,/cmThe distance between the monocular camera and the object to be measured is delta u and delta v, which are respectively the transverse distance and the longitudinal distance of the image of the object to be measured by the monocular camera.
According to the technical scheme, the target is square, four vertexes of the square target are connected in opposite angles, a connecting line intersection point is used as a center to serve as a center circle, and four intersection points of the center circle and two diagonal lines are used as circle centers to be respectively pasted with the small round targets.
Correspondingly, the invention also provides a monocular camera-based multi-height calibration measuring method and a crane diagonal-pulling prevention and accurate positioning method, which comprise the following steps:
s1, mounting the monocular camera at the bottom of a trolley of the crane, placing the anti-diagonal-pulling controlled target on a hook, and accurately positioning the target as a mobile target;
s2, according to the multi-height calibration measurement method based on the monocular camera, the moving distance delta X of the trolley and the moving distance delta Y of the cart are obtained by combining the calibration formula of the monocular camera according to the rope length l of the crane, the transverse distance delta u and the longitudinal distance delta v of the target image measured by the monocular camera.
According to the technical scheme, the monocular camera is provided with the light source.
According to the technical scheme, one end of the winding drum of the crane is provided with the encoder for measuring the length of the rope.
According to the technical scheme, the set trolley is accelerated to the set trolley running speed v in the anti-diagonal-pulling control processcThe combined displacement of the maximum acceleration and deceleration displacement of the trolley under the condition of immediate decelerationIn the formula tcaAnd tcdRespectively the acceleration and deceleration time of the trolley when the delta X is>scmaxThe trolley undergoes three stages of acceleration, uniform speed and deceleration; when DeltaX is less than or equal to scmaxThe trolley undergoes two acceleration and decelerationAnd (5) stage.
According to the technical scheme, the speed v for accelerating the cart to the set running speed v of the cart is set in the anti-diagonal-pulling control processtThe combined displacement of the maximum acceleration and deceleration displacement of the cart under the condition of immediate deceleration
Figure GDA0002266538350000032
In the formula ttaAnd ttdRespectively the acceleration and deceleration time of the cart; when Δ Y is>stmaxThe cart is subjected to three stages of acceleration, uniform speed and deceleration; when DeltaY is less than or equal to stmaxIn time, the cart undergoes two phases of acceleration and deceleration.
According to the technical scheme, the accurate positioning displacement of the trolley is set to be SpcThe trolley undergoes two stages of uniform speed and deceleration in the accurate positioning process, and the constant speed time of the trolley is at the moment
According to the technical scheme, the precise positioning displacement of the cart is set to be SptThe cart goes through two stages of uniform speed and deceleration in the accurate positioning process, and the cart is at the uniform speed at the moment
Figure GDA0002266538350000034
The invention has the following beneficial effects: the method is based on a machine vision technology, and realizes the accurate measurement of the target position of the monocular camera under the condition of different heights through multi-height calibration, the multi-height calibration process specifically comprises the steps of dividing the depth of field range of the camera into a plurality of sections, equally dividing the field of view of the camera in each section of height range into a plurality of sections according to the transverse direction and the longitudinal direction, and establishing mathematical models of pixel distances and actual distances at different heights by moving targets for a plurality of times in the transverse direction and the longitudinal direction in each section of depth of field variation range in the camera calibration process. In addition, the monocular camera-based multi-height calibration measurement method is applied to the anti-diagonal pulling and accurate positioning of the crane, the anti-diagonal pulling control in the lifting process of the crane is realized, the vertical lifting of the load is realized, the operation safety of the crane and the control accuracy of an open-loop anti-swing control algorithm are improved, and the accurate unloading of the target position is realized through the open-loop anti-swing control of the crane based on the machine vision guidance.
The monocular camera-based multi-height calibration and measurement method realizes the measurement of the target position, has high sensitivity, convenient implementation and strong robustness, greatly improves the operation safety and the working efficiency of the crane, and promotes the automation, digitization and intelligent development of the crane.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic diagram of a machine vision guidance based crane anti-diagonal pulling and precise positioning system;
FIG. 2 is a schematic diagram of calibration of a crane anti-diagonal drawing and precise positioning system camera based on machine vision guidance;
FIG. 3 is a schematic target diagram of a machine vision guidance based crane anti-diagonal pulling and precise positioning system;
FIG. 4 is a schematic diagram of the control process of the trolley in the anti-diagonal-pulling control;
FIG. 5 is a schematic view of a cart control process in the anti-diagonal-pulling control;
FIG. 6 is a schematic diagram of the control process of the cart without anti-roll;
fig. 7 is a schematic diagram of the control process of the cart without anti-rolling.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 2, a monocular camera-based multi-height calibration measurement method includes the following steps:
s1, selecting a monocular camera, and acquiring the following parameters: maximum height Δ l within the depth of field of the camera, maximum lateral field of view 2X of the camera, maximum longitudinal field of view 2Y of the camera, and maximum working distance l of the cameraH；
S2, placing the targetWithin the visual field range and the depth of field range of the monocular camera, the delta l is divided into H sections, and the height of each section is delta lhH1, 2, 3.. H, dividing half of the maximum transverse field of view X into m segments at each segment height, each segment having a transverse distance Δ XhiI 1, 2, 3.. m, dividing half of the maximum longitudinal field of view Y into n segments at each segment height, each segment having a longitudinal distance Δ Yhj，j＝1，2，3...n；
S3, at each height, according to the transverse movement direction from delta Xh1To Δ XhmMoving to respectively obtain the transverse distance delta u of the target imageshiFrom Δ Y in the direction of longitudinal movementh1To delta YhnMoving to respectively obtain the longitudinal distance delta v of the target imageshj；
S4, according to the calibration formula of the monocular camera:
Figure GDA0002266538350000041
solving the scale factor b and the camera internal parameter kxhiAnd kyhjInitial coordinates u in image coordinates expressed in physical units0And v0Measuring the transverse distance delta X and the longitudinal distance delta Y of the object to be measured in the field depth range and the field range of the monocular camera according to the solved calibration formula of the monocular camera, namely delta X ═ f (l)cm、Δu)，ΔY＝f(lcmΔ v), in which lhDistance between monocular camera and target,/cmThe distance between the monocular camera and the object to be measured is delta u and delta v, which are respectively the transverse distance and the longitudinal distance of the image of the object to be measured by the monocular camera.
In the preferred embodiment of the present invention, as shown in fig. 3, the target is a square, four vertexes of the square target are connected diagonally, a line intersection point is used as a center to make a center circle, and four intersection points of the center circle and two diagonal lines are used as centers to respectively paste a small circular target, so as to improve the measurement accuracy and robustness of the vision measurement system.
A method for preventing inclined pulling and accurately positioning a crane based on machine vision guidance is shown in figures 1 and 2 and comprises the following steps:
s1, mounting the monocular camera at the bottom of a trolley of the crane, placing the anti-diagonal-pulling controlled target on a hook, and accurately positioning the target as a mobile target;
s2, according to the multi-height calibration measurement method based on the monocular camera, the moving distance delta X of the trolley and the moving distance delta Y of the cart are obtained by combining the calibration formula of the monocular camera according to the rope length l of the crane, the transverse distance delta u and the longitudinal distance delta v of the target image measured by the monocular camera.
In a preferred embodiment of the present invention, as shown in FIG. 1, a monocular camera is configured with a light source.
In a preferred embodiment of the invention, as shown in fig. 1, the drum of the crane is fitted at one end with an encoder for measuring the rope length.
In the preferred embodiment of the invention, as shown in fig. 4, the set cart is accelerated to the set cart running speed v during the anti-diagonal pull controlcThe combined displacement of the maximum acceleration and deceleration displacement of the trolley under the condition of immediate decelerationIn the formula tcaAnd tcdRespectively the acceleration and deceleration time of the trolley when the delta X is>scmaxThe trolley undergoes three stages of acceleration, uniform speed and deceleration; when DeltaX is less than or equal to scmaxThe trolley undergoes two stages of acceleration and deceleration;
in a preferred embodiment of the present invention, as shown in fig. 5, the acceleration of the cart is set to the set cart running speed v during the anti-diagonal pull controltThe combined displacement of the maximum acceleration and deceleration displacement of the cart under the condition of immediate deceleration
Figure GDA0002266538350000052
In the formula ttaAnd ttdRespectively the acceleration and deceleration time of the cart; when Δ Y is>stmaxThe cart is subjected to three stages of acceleration, uniform speed and deceleration; when DeltaY is less than or equal to stmaxIn time, the cart undergoes two phases of acceleration and deceleration.
In the preferred embodiment of the present invention, as shown in FIG. 6, the cart is set to be precisely determinedBit shift of SpcThe trolley undergoes two stages of uniform speed and deceleration in the accurate positioning process, and the constant speed time of the trolley is at the moment
In the preferred embodiment of the present invention, as shown in fig. 7, the cart is set to the precise positioning displacement SptThe cart goes through two stages of uniform speed and deceleration in the accurate positioning process, and the cart is at the uniform speed at the moment
Figure GDA0002266538350000054
The invention is applied to the anti-diagonal drawing and accurate positioning of a crane, as shown in figure 1, a vision measuring system comprises an encoder 8, an industrial personal computer 9, an industrial camera 10, a light source 11 and a target 12, the crane system comprises a PLC 1, a cart frequency converter 2, a cart 5, a trolley frequency converter 3, a trolley 6, a lifting frequency converter 4, a lifting mechanism 7 and the like, wherein the PLC is connected with the encoder and the industrial personal computer, the data of the lifting rope length measured by the encoder can be transmitted to the industrial personal computer, the industrial personal computer is connected with the industrial camera, the target position is calculated by using a target image acquired by the industrial camera and the rope length measured by the encoder, and the target position is obtained based on the pixel distance obtained by multi-height calibration and a mathematical model of the actual distance, so as to determine the control rule of; the PLC is connected with the cart frequency converter, the trolley frequency converter and the lifting frequency converter, the frequency of the frequency converters is changed to control the cart, the trolley and the lifting mechanism to respectively run, the industrial camera and the light source are installed below the trolley running mechanism, and the direction of the optical axis is vertical.
The positioning method comprises the following steps:
s1, setting system initialization parameters: establishing communication connection among an industrial camera, an industrial personal computer, a PLC and each operating mechanism, and inputting the operating speeds of each gear of the cart, the trolley and the hoisting mechanism;
s2, calibrating an industrial camera: placing the target at the vertical center and recording as an initial position, acquiring an initial position target image and recording the position of the initial position target image by an industrial camera, and then moving the target along the movement direction of the trolley by a target distance delta XhiMoving the target m times, simultaneously acquiring a target position image by the industrial camera when moving the target each time, and calculating the distance delta u corresponding to the target imagehi(ii) a Moving the target distance delta Y along the moving direction of the carthjMoving the target n times, simultaneously acquiring a target position image by the industrial camera when the target is moved each time, and calculating the distance delta v corresponding to the target imagehjFinally, calculating a visual measurement mathematical model of the actual distance and the pixel distance according to an industrial camera calibration formula;
s3, an anti-diagonal tension measurement process: the crane hoisting mechanism runs, when the hoisting rope length is in a tensioning state, the industrial camera collects a target image in real time and transmits the target image to the industrial personal computer, the industrial personal computer calculates the distance and the direction between the target position and the load position according to an image processing algorithm, and then the distance and the direction of the inclined pulling horizontal displacement of the load in the trolley direction and the trolley direction are respectively Sc1And St1；
S4, an anti-diagonal-pulling control process in the trolley direction: if Sc1>10mm, prevent drawing control to one side on the dolly direction, according to the operation process of hoist, the hoist prevent drawing control process to one side divide into with higher speed, at the uniform velocity and slow down, perhaps accelerate, slow down two processes, according to the dolly set parameter can know that the dolly is the displacement that closes of the biggest acceleration and the displacement that slows down does:
Figure GDA0002266538350000061
if Sc1＞ScmaxV is used in the control process of preventing the car from being inclinedc/tcaAccelerated running time tcaThen with vcRun time
Figure GDA0002266538350000062
Finally with-vc/tcdDeceleration running time tcdThen stopping; if Sc1≤ScmaxV is used in the control process of preventing the car from being inclinedci/tcaAccelerated running time t1And finally with-vci/tcdDeceleration running time t2Then stopping, wherein the lifting hook is vertically zero above the load;
s5, an anti-diagonal pulling control process in the cart direction: if St1>10mm, prevent drawing control to one side on the cart direction, according to the operation process of hoist, the hoist prevent drawing control process to one side divide into with higher speed, at the uniform velocity and slow down, perhaps accelerate, two processes of slowing down, can know the cart maximum acceleration and the displacement that closes of slowing down the displacement according to cart set parameter and do:
Figure GDA0002266538350000063
if St1＞StmaxV is used in the control process of preventing the cart from being inclinedt/ttaAccelerated running time ttaThen with vtRun time
Figure GDA0002266538350000064
Finally with-vt/ttdDeceleration running time ttdThen stopping; if St1≤StmaxV is used in the control process of preventing the cart from being inclinedti/ttaAccelerated running time t3And finally with-vti/ttdDeceleration running time t4Then stopping, wherein the lifting hook is vertically zero above the load;
s6, if St1<10mm and Sc1<10mm, the crane hoisting mechanism automatically controls the load to hoist to a safe height;
s7, accurate positioning measurement and control process of the trolley: setting the accurate positioning displacement of the trolley as Spc. The accurate positioning target is placed at the target position in the accurate positioning process, and v is used as v when the industrial camera acquires the image of the accurate positioning targetcRun at uniform timeThen with-vc/tcdDeceleration running time tcdStopping, wherein the stopping position is a target position;
s8, accurate positioning measurement and control process of the cart: setting the precise positioning displacement of the cart as Spt. In the accurate positioning process, the accurate positioning target is placed at the target position to serve as an industrial phaseWhen the machine acquires the accurate positioning target image, v is usedtRun at uniform timeThen with-vt/ttdDeceleration running time ttdStopping, wherein the stopping position is a target position;
s9, accurately positioning and controlling the process when the anti-shaking is started: the distances between the load position and the target position in the cart direction and the trolley direction are respectively StAnd ScThe sum of the acceleration distance and the deceleration distance of the open-loop anti-swing is S in the direction of the cart and the trolleyotAnd SocWhen S ist<SotOr Sc<SocWhen the system is used, a low-speed operation control strategy is adopted for control; when S ist>SotOr Sc>SocWhen the crane is at St＝SotWhen the speed of the cart is reduced, the cart starts to be controlled to prevent shaking; sc＝SocWhen the cart and the trolley are decelerated to stop, the load is right above the target position;
and S10, the hoisting mechanism operates again to place the load at the target position.
The steps S1-S10 of the monocular camera-based multi-height calibration and measurement method and the crane anti-diagonal-pulling and accurate positioning method are only used for explaining the application of the monocular camera-based multi-height calibration and measurement method machine in crane safety control, and the method comprises all implementation processes of a crane anti-diagonal-pulling control system based on machine vision guidance and a crane accurate positioning system based on open loop anti-sway, and only needs to be initially set in the installation and debugging process according to use requirements in practical application.
The operation of the various components of the present invention is described in detail below.
The industrial camera transmits acquired image information to the industrial personal computer in a Gige mode, the industrial personal computer sends target position information to the control center PLC in a USB 485 serial port communication mode, and finally the PLC controls the large trolley and the lifting frequency converter to operate in communication modes such as Profinet or Profibus-DP.
Calibrating an industrial camera: according to the vision measurement principle, the industrial camera simultaneously projects a model consisting of an image coordinate system, a camera coordinate system (X, y, z) and world coordinates (X)w，Yw，Zw) Three major coordinate systems, wherein the image coordinate system further includes an image coordinate system (u, v) in units of pixels and an image coordinate system (X, Y) in units of physical units. Considering that only the relative distance between the load position and the target position needs to be calculated in the practical application process of the crane, the change of the crane in the world coordinate system can be ignored. Meanwhile, the crane cart and the crane trolley move independently, so that the calibration rules of the industrial camera in the cart and trolley directions are the same, the height of the working space of the crane is assumed to be h, and the calibration formula of the industrial camera is as follows:
Figure GDA0002266538350000081
wherein b is a scale factor, kxhiAnd kyhjAs camera intrinsic parameters, u0And v0As initial coordinates in image coordinates expressed in physical units, lnThe length of a hoisting rope of the crane is set, m is the number of transverse sections in the visual field range of the camera, and i is the ith section in the visual field range of the camera; n is the number of longitudinal sections in the camera view range, and j is the jth section of the camera view; h is the number of segments of the depth range of the camera.
Determination of a mathematical model of vision measurement: determining the working height l according to the practical application requirement of the crane within the maximum visual field and depth of field range of the cameraHMaximum lateral distance to field of view of 2smaxWhen the variation range of the load height is Deltal, the maximum diagonal-pulling angle of the loaded cable is tan thetamax＝smax/lnAnd further has a height of Δ l per segment of
Figure GDA0002266538350000082
i is 1, 2, n, n is more than or equal to 2, and the camera vision range is divided into a plurality of sections on each section of height, namely, the distance of each section in the trolley motion direction of the camera vision transverse range is delta XhiLongitudinal extent of camera field of viewEach section of distance in the moving direction of the cart is delta YhjIn the actual calibration process, the target distance delta X is respectively moved along the direction of the trolley and the direction of the trolley on each section of depth of field heightwiAnd Δ YhjMoving m and n times respectively, simultaneously collecting target position images by the industrial camera when moving the target each time, and calculating the distance delta u corresponding to the target imageshiAnd Δ vhjAnd finally, calculating a visual measurement mathematical model of the actual distance and the pixel distance according to an industrial camera calibration formula.
Designing a visual measurement method: in order to improve the measurement accuracy and robustness of the vision measurement system, a four-target characteristic point target is designed based on geometric symmetry. Specifically, four vertexes of the square target are connected diagonally, a circle is made by taking a connecting line intersection point as a center, focuses of the circle and the two diagonal lines are selected as centers of four target feature points, and each target feature point is a circle with the same size. If the collected target image of the industrial camera contains four target feature points, obtaining the central coordinates of each target feature point through image processing, respectively calculating the distance between the central coordinates of every two target feature points, respectively comparing the distances, and averaging the central points of the two coordinate points corresponding to the two longest distances to obtain a target position; if the industrial camera collects images of three target feature points, the central position of each feature point is obtained through image processing, the distance between the central coordinates of every two feature points is calculated, then the coordinate distance is judged, and the midpoint coordinate of the two target feature points corresponding to the longest distance is recorded as the target position. If the industrial camera collects the images of the two target feature points, the center coordinates of each feature point are respectively obtained through image processing, and the midpoint coordinates of the center coordinates of the two target feature points are calculated, so that the target position is obtained. If the industrial camera acquires a target feature point image, the center coordinates of the feature points are obtained through image processing, and therefore the target position is obtained.
Determining the anti-diagonal-pulling control strategy of the crane: according to the running process of the crane, the precise process of the crane is divided into acceleration, uniform speed and deceleration, or two processes of acceleration and deceleration. At the same time, in the crane system, the running speed v of the carttAcceleration and deceleration time tta、ttdThe running speed v of the trolleycAcceleration and deceleration time t of trolleyca、tcdThe accurate positioning system selects the transport displacement S of the big car and the small car for setting parameters for the systemt、ScAs a determination condition. According to the trolley setting parameters, the combined displacement of the maximum acceleration displacement and the maximum deceleration displacement of the trolley is as follows:
Figure GDA0002266538350000091
the constant speed time t of the trolley exists in the acceleration, constant speed and deceleration processes of the trolleycvIs calculated by the formula
Figure GDA0002266538350000092
When the trolley is accelerated and uniform, the acceleration time t of the trolley is1And t2
Figure GDA0002266538350000093
Similarly, according to the set parameters of the cart, the combined displacement of the maximum acceleration displacement and the maximum deceleration displacement of the cart is as follows:
Figure GDA0002266538350000094
the constant speed time t of the cart exists in the acceleration, constant speed and deceleration processes of the carttvIs calculated by the formulaWhen the big vehicle is accelerated and uniform, the acceleration time t of the big vehicle3And a deceleration time t4Satisfies the following formula:
Figure GDA0002266538350000096
accurate positioning measurement and control strategy determination of the trolley: setting the accurate positioning displacement of the trolley as SpcThe trolley undergoes two stages of uniform speed and deceleration in the accurate positioning process, and the constant speed time of the trolley is at the moment
Figure GDA0002266538350000097
Large vehiclePrecise positioning measurement and control strategy determination: setting the precise positioning displacement of the cart as SptThe cart goes through two stages of uniform speed and deceleration in the accurate positioning process, and the cart is at the uniform speed at the moment
Determining an accurate positioning control strategy during starting and shaking prevention: the distances between the load position and the target position in the cart direction and the trolley direction are respectively StAnd ScThe sum of the acceleration distance and the deceleration distance of the open-loop anti-swing is S in the direction of the cart and the trolleyotAnd Soc. When S ist<SotOr Sc<SocAnd meanwhile, the control is carried out by adopting a low-speed operation control strategy. When S ist>SotOr Sc>SocAccording to the characteristic of open-loop anti-swing of the crane, namely the acceleration anti-swing control process and the deceleration anti-swing control process of the crane are the same, the accurate positioning system of the crane obtains the running distance S in the deceleration anti-swing process of the large crane trolley according to the running distance in the acceleration anti-swing process of the large crane trolley1、S2。
According to the invention, the depth of field range of the camera is divided into multiple sections, and the visual field range in the depth of field range of each section of camera moves the target for multiple times along the transverse direction and the longitudinal direction respectively, so that mathematical models of pixel distance and actual distance at different heights are established; the multi-height calibration and measurement method based on the monocular camera is based on a machine vision technology, and the accurate measurement of the target position of the monocular camera under the condition of different heights is realized through multi-height calibration; in the practical application process, a plurality of target characteristic points are arranged on the square target, and the different target characteristic points are distributed according to geometric symmetry, so that the robustness of the visual measurement algorithm is further improved; finally, the multi-height calibration and measurement method based on the monocular camera is utilized to realize the anti-diagonal pulling control in the lifting process of the crane, and the accurate positioning in the unloading process is realized through the control of the motion rule of the crane.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.

Claims (9)

1. A multi-height calibration measuring method based on a monocular camera is characterized by comprising the following steps:
s1, selecting a monocular camera, and acquiring the following parameters: maximum height Δ l within the depth of field of the camera, maximum lateral field of view 2X of the camera, maximum longitudinal field of view 2Y of the camera, and maximum working distance l of the cameraH；
S2, placing the target in the visual field range and the depth of field range of the monocular camera, dividing delta l into H sections, wherein the height of each section is delta lhH1, 2, 3.. H, dividing half of the maximum transverse field of view X into m segments at each segment height, each segment having a transverse distance Δ XhiI 1, 2, 3.. m, dividing half of the maximum longitudinal field of view Y into n segments at each segment height, each segment having a longitudinal distance Δ Yhj，j＝1，2，3...n；
S3, at each height, according to the transverse movement direction from delta Xh1To Δ XhmMoving to respectively obtain the transverse distance delta u of the target imageshiFrom Δ Y in the direction of longitudinal movementh1To delta YhnMoving to respectively obtain the longitudinal distance delta v of the target imageshj；
S4, calibrating formula according to monocular camera
Solving the scale factor b and the camera internal parameter kxhiAnd kyhjInitial coordinates u in image coordinates expressed in physical units0And v0Measuring the transverse distance delta X and the longitudinal distance delta Y of the object to be measured positioned in the field depth range and the field range of the monocular camera according to the solved calibration formula of the monocular camera, wherein delta X is f (l)cm、Δu)，ΔY＝f(lcmΔ v), in which lhDistance between monocular camera and target,/cmIs the distance between the monocular camera and the object to be measuredAnd the distance delta u and the distance delta v are respectively the transverse distance and the longitudinal distance of the image of the object to be measured by the monocular camera.
2. The monocular camera-based multi-height calibration measuring method according to claim 1, wherein the target is a square, four vertexes of the square target are connected diagonally, a central circle is made with a connecting line intersection point as a center, and small circular targets are respectively pasted with four intersection points of the central circle and two diagonal lines as centers.
3. A crane diagonal pulling prevention and accurate positioning method based on machine vision guidance is characterized by comprising the following steps:
s1, mounting the monocular camera at the bottom of a trolley of the crane, placing the anti-diagonal-pulling controlled target on a hook, and accurately positioning the target as a mobile target;
s2, according to the monocular camera-based multi-height calibration measuring method of claim 1, the trolley moving distance delta X and the trolley moving distance delta Y are obtained by combining the calibration formula of the monocular camera according to the rope length l of the crane, the transverse distance delta u and the longitudinal distance delta v of the target image measured by the monocular camera.
4. The machine vision guidance-based crane diagonal pulling prevention and precise positioning method according to claim 3, wherein the monocular camera is configured with a light source.
5. The machine vision guidance-based crane diagonal pulling prevention and precise positioning method as claimed in claim 3, wherein an encoder for measuring the rope length is installed at one end of a winding drum of the crane.
6. The machine vision guidance-based crane diagonal-pulling prevention and accurate positioning method as claimed in claim 3, wherein the set trolley is accelerated to the set trolley running speed v in the diagonal-pulling prevention control processcThe combined displacement of the maximum acceleration and deceleration displacement of the trolley under the condition of immediate deceleration
Figure FDA0002266538340000021
In the formula tcaAnd tcdRespectively the acceleration and deceleration time of the trolley when the delta X is>scmaxThe trolley undergoes three stages of acceleration, uniform speed and deceleration; when DeltaX is less than or equal to scmaxIn time, the trolley undergoes two phases of acceleration and deceleration.
7. The machine vision guidance-based crane diagonal pulling prevention and accurate positioning method according to claim 3, wherein the set crane is accelerated to the set crane running speed v in the diagonal pulling prevention control processtThe combined displacement of the maximum acceleration and deceleration displacement of the cart under the condition of immediate deceleration
Figure FDA0002266538340000022
In the formula ttaAnd ttdRespectively the acceleration and deceleration time of the cart; when Δ Y is>stmaxThe cart is subjected to three stages of acceleration, uniform speed and deceleration; when DeltaY is less than or equal to stmaxIn time, the cart undergoes two phases of acceleration and deceleration.
8. The machine vision guidance-based crane diagonal pulling prevention and accurate positioning method as claimed in claim 6, wherein the accurate positioning displacement of the trolley is set to SpcThe trolley undergoes two stages of uniform speed and deceleration in the accurate positioning process, and the constant speed time of the trolley is at the moment
Figure FDA0002266538340000023
9. The machine vision guidance-based crane diagonal pulling prevention and accurate positioning method according to claim 7, wherein the accurate positioning displacement of the cart is set to SptThe cart goes through two stages of uniform speed and deceleration in the accurate positioning process, and the cart is at the uniform speed at the moment
Figure FDA0002266538340000024
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