JPH1133962A - Calibration of three-dimensional position sensor for robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the working time, to save the labor, and to safely perform the calibration by fitting a jig having a characteristic point to a manipulator, and obtaining the combination of a three-dimensional position of the characteristic point with a position of a characteristic point of a pickup image of a camera so as to perform the calibration of the three-dimensional position of the camera. SOLUTION: A red color LED 10 is fitted to a jig so as to be lighted on the basis of a command from a robot main body 1. Position of the LED 10, which is seen from a jig fitting surface of a manipulator 3, is previously recorded in a robot system. The manipulator 3 is moved to a measurement point, and the LED 10 of a tip of the jig is lighted. Images, which are seen from an image pickup camera and a ranging camera, is taken into an image processing part, and the only part lighted by the LED 10 is drawn. An image is processed with binary so as to specify the position of the LED 10 of an image pickup surface of the camera, and the LED 10 of a coordinate system of the manipulator 3 is read from a control part of the manipulator 3. With this structure, labor is saved, and time is shortened, and calibration is safely performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to calibration of a three-dimensional position sensor (integrated processing of different coordinate systems), and more particularly to calibration of a three-dimensional position sensor mounted on a robot having a manipulator.

[0002]

2. Description of the Related Art A conventional robot is fixed to a production line or the like in a factory, and since a work target is also fixed, a series of operations that are previously programmed are often repeated.
In such a case, the repeat position accuracy of the robot was required, and the absolute position accuracy did not matter. But,
Recently, the demand for flexible and advanced robot systems that can respond to changes in work environments and work targets has increased, and visual sensors and position sensors have been used in combination with robots. As an example, there is a work in which the position of an object is measured by a position sensor under various environments, and the robot grasps the object with a manipulator.

In such a case, calibration between the coordinate system of the position sensor and the coordinate system of the manipulator is important in addition to the absolute position accuracy of the manipulator. 5 as a three-dimensional position sensor [conventional example 1]
Take for example. In the drawings, the same reference numerals represent the same or corresponding members. In FIG. 5, reference numeral 5 denotes a laser projector for emitting a slit-shaped laser beam 6, reference numeral 7 denotes an aiming camera for aiming the laser beam 6 on an object to be measured, and reference numeral 8 denotes an imaging camera for imaging the object to be measured and the laser slit light 6. , 9 are objects to be measured. A laser slit light 6 emitted from a laser projector 5 is applied to an object 9 and an image thereof is formed by a camera 8.
And the position of the object 9 is calculated from the position on the image plane by the principle of triangulation. Iguchi and Sato [3D image measurement]
(Tokodo), the measurement principle will be briefly described below.

Assuming that the coordinate system of the imaging plane of the camera 8 is a sensor coordinate system and the coordinate system of the object 9 is an object coordinate system, as shown in FIG. , Z) are projected onto a point P ′ (Xc, Yc) in the sensor coordinate system.
Therefore, the point P ′ in the sensor coordinate system can be represented by performing a perspective transformation and a coordinate transformation on the point P in the object coordinate system. In FIG. 6, the conversion from the target point P in the object coordinate system to the point P ′ in the sensor coordinate system is represented by a matrix as shown in Expression (1).

[0005]

(Equation 1)

Here, H is a variable for homogeneous conversion. Equation (1) represents the line of sight of the camera, and the 3 × 4 C matrix of equation (1) is called a camera parameter. The camera parameters include all data related to the camera, such as the position, posture, and angle of view. Also, the plane of the slit light 6 can be described by the equation (2) in the object coordinate system. P ₁ X + P ₂ Y + P ₃ Z = P ₄ Equation (2) P _{1 to} P ₄ are called project parameters, and the intersection P (X, Y, Z) of the straight line and the plane is defined by these two It is obtained by simultaneous equations.

[0007] To summarize expand equation _{(1), (C 11 -C} 31 Xc) X + (C 12 -C 32 Xc) Y + (C 13 -C 33 Xc) Z = C 34 Xc-C 14 ...... .................. formula _{(3) (C 21 -C 31} Yc) X + (C 22 -C 32 Yc) Y + (C 23 -C 33 Yc) Z = C 34 Yc-C 24 .................. ...... Equation (4)

[0008]

(Equation 2)

In other words, equations (2), (3) and (4) can be expressed collectively as F = QV...... Therefore, if there is an inverse matrix of Q, the intersection P (X, Y, Z) can be obtained from V = Q ⁻¹ F... (9). That is, when the target object is irradiated with the slit light 6, the position of the target object in the object coordinate system can be obtained from these positions in the sensor coordinate system using these parameters. Conversely, these parameters can be calibrated by measuring an object whose position in the object coordinate system is known.

When calibrating each parameter of the position sensor, a conventional concrete example uses a three-dimensional measuring device [conventional example 2] as shown in FIG. 7, reference numeral 19 denotes an LED (light emitting diode), and reference numerals 20 and 21 denote LEDs.
A camera for imaging 19, 22 is a three-dimensional measuring device main body, 23
Is a console for operating the CMM. The cameras 20 and 21 are arranged on both sides of the robot 1 so as to cover the measurement range of the position sensor 2 (the field of view of the imaging camera 8), and first the calibration of the three-dimensional measuring device is performed. Thereafter, as shown in FIG. 7, the laser slit light 6 of the position sensor 2 is applied to the LED 19 using a tripod or the like, and the position of the LED 19 on the imaging surface of the imaging camera 8 is specified by image processing. At the same position, the three-dimensional position of the LED 19 in the coordinate system of the three-dimensional measuring device is measured by triangulation using the cameras 20 and 21.

The LED 19 is manually moved little by little along the plane of the laser slit light 6, and the position of the LED 19 in the coordinate system of the three-dimensional measuring device and the position in the sensor coordinate system are measured in the same manner. After measuring at dozens of points,
Calculate the parameters by the least squares method. However, since the parameters are calculated using the coordinate system of the three-dimensional measuring device as the object coordinate system, if the measurement is performed as it is, the position of the three-dimensional measuring device in the coordinate system will be calculated. In the actual work, calibration was further performed to determine a matrix to be converted to the manipulator coordinate system.

[0012] Furthermore, Japanese Patent Application Laid-Open No.
No. -8186 [Conventional Example 3]. It is a method for automatically performing calibration between the image processing device and the automatic machine. The calibration jig data and the position of the robot equipped with the jig that allows the camera to shoot the jig during calibration are set and taught. In accordance with the calibration command, the robot with the jig moves to the teaching point, and after the movement, the image processing apparatus takes an image of the jig and captures an image. Calibration processing is performed according to the position, jig data and teaching points are set and taught once, and subsequent calibration is automatically performed only by attaching a jig to the robot and inputting a calibration command. Is a means for performing calibration.

[0013]

However, in the method of the conventional example 2, it takes a long time to prepare the three-dimensional measuring device and to calibrate the three-dimensional measuring device itself. In addition, the LED of the CMM must be manually moved at each measurement point. At this time, the laser is irradiated to move the laser along the plane of the laser slit light. I needed to. In addition, the calibration takes a lot of time and labor, such as the need for calibration between the coordinate system of the coordinate system and the coordinate system of the manipulator because the coordinate system and the robot are separate systems. was there.

Further, in the conventional example 3, in the automatic flow process of the robot application, if the setting is taught without repeating the calibration one by one at the time of an abnormal change such as a shift of the camera over time or a change in the optical environment, it becomes necessary. Since the calibration can be performed in response to this, it is slightly different from what the present invention considers. Therefore, an object of the present invention is to provide a safe calibration method that can be performed in a short time and with a small number of people.

[0015]

According to a first aspect of the present invention, a jig having a feature point is mounted on a manipulator of a robot, and a cubic arrangement of the feature point in a reference coordinate system is provided. A plurality of combinations of the original position and the positions of the feature points on the imaging planes of the two cameras of the sensor unit for imaging and aiming are obtained, and the three-dimensional positions of the two cameras of the sensor unit are determined using the results. A calibration method for a three-dimensional position sensor of a robot characterized by performing calibration.

In this way, it is not necessary to use a three-dimensional measuring device at the time of calibration, and the calibration is completed only in the robot system, so that the time and labor can be saved, and the measurement of the operator can be performed. A special effect that the calibration can be performed safely without emitting the laser in the working direction can be achieved.

According to a second aspect of the present invention, in the method for calibrating a three-dimensional position sensor of a robot according to the first aspect, a laser projector and an aiming device for aiming a laser beam emitted from the laser projector. A camera and an imaging camera attached to the aiming camera at a fixed interval at a fixed angle and imaging the object and the laser light, mounted on a robot together with the manipulator, and mounted on the robot. And irradiating the laser light on the imaging surface of the imaging camera to measure the position of the object based on the principle of triangulation from the position of the laser light. Is the way.

Thus, it is not necessary to use a three-dimensional measuring device at the time of calibration, and the calibration is completed only in the robot system. Therefore, the time and labor can be saved, and the laser is not emitted. There is a remarkable effect that the calibration can be performed safely.

According to a third aspect of the present invention, there is provided a laser projector mounted on a robot, an aiming camera for aiming a laser beam emitted from the laser emitter, and a fixed distance from the aiming camera. An imaging camera that is attached at a fixed angle and captures an object and the laser light, a manipulator that moves a calibration jig, an LED provided on the calibration jig, and a built-in robot control unit. CPU that performs all control calculations, a memory that stores data, an image processing unit that processes images of the aiming camera and the imaging camera, and a manipulator control unit that controls movement of the manipulator. , And an I / O unit for converting input and output to and from the laser projector and the LED. Operating the controller in various commands,
A calibration device for a three-dimensional position sensor of a robot, comprising an operation unit for displaying an image and displaying parameters to an operator.

Therefore, according to the present invention, a very simple circuit configuration and a device excellent in safety are realized, work efficiency and reliability are improved, and a remarkable effect that a three-dimensional position sensor calibration device can be established. Is recognized.

According to a fourth aspect of the present invention, there is provided the calibration apparatus for a three-dimensional position sensor of a robot according to the third aspect, wherein an LED is mounted on a tip of a manipulator capable of changing a position in three dimensions. Is a calibration device for a 3D position sensor of a robot, characterized in that the 3D position sensor is calibrated by blinking.The feature points to be calibrated are clearly and safely required, and the universality of work is remarkable It is possible to make a contribution.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view illustrating a main part of the first embodiment of the present invention. In FIG. 1, 1 is a robot body, 2
Denotes a sensor unit of the robot main body 1, 3 denotes a manipulator of the robot main body 1, and 4 denotes a calibration jig attached to the manipulator 3.

As shown in FIG. 2, a red L is provided at the tip of the jig.
The ED 10 is attached, and is turned on by a command from the robot body 1. FIG. 3 is a front view showing an image viewed from the imaging camera during the execution of the calibration according to the first embodiment.

FIG. 4 is a block diagram showing a circuit configuration for executing this calibration, wherein 5 is a laser projector, 11 is a robot controller, and C
PU (Central Processing Unit) 12, memory 1 for storing information
3. Image processing unit 14 for processing images, manipulator 3
Manipulator control unit 15 for controlling the laser projector 5
And an I / O unit 16 for converting output information to the LED 10 and sending it out as an appropriate electric signal, and the controller 11 is provided with a command from an operation unit 17 operated by various commands from an operator 18. In addition, the image display and the parameter display are returned to the operator 18 via the operation unit 17.

L viewed from the jig mounting surface of the manipulator 3
The position up to the center of the ED 10 is recorded in the robot system in advance. It is also assumed that the manipulator 3 has already completed calibration. The manipulator 3 is moved to the measurement point, and the operation of the operator 18 causes the LED 10 at the tip of the jig to light up. The LED viewed from the imaging camera 8 and the aiming camera 7 at the timing of this blinking
10 When the light is turned on, the image when the light is turned off is taken into the image processing unit 14,
Only the lighting portion of the LED 10 is extracted from the difference image between the lighting image and the turning-off image.

The image is binarized to determine the center of gravity, and the position of the LED 10 on each camera imaging plane is specified. At the same time, the three-dimensional position of the LED 10 at the tip of the jig in the coordinate system of the manipulator 3 is read from the control unit 15 of the manipulator 3. The same operation is performed by moving the manipulator 3 to the next measurement point by the operation of the operator 18.
The same operation is repeated until a predetermined score is reached, and when the measurement is completed, the respective camera parameters of the aiming camera 7 and the imaging camera 8 are automatically calculated based on the measurement results up to that point.

Here, a project parameter is obtained by utilizing that the laser slit light 6 viewed from the aiming camera 7 is always at a fixed position. Assuming that the camera parameters of the aiming camera 7 are C ′ _{11 to} C ′ ₃₄ , similarly to Expressions (3) and (4), (C ′ ₁₁ −C ′ ₃₁ X′c) X + (C ′ ₁₂ −C ′ ₃₂₎ X′c) Y + (C ′ ₁₃ −C ′ ₃₃ X′c) Z = C ′ ₃₄ X′c−C ′ ₁₄ ... Formula (10) (C ′ ₂₁ −C ′ ₃₁ Y′c) _{X + (C '22 -C'} 32 Y'c) Y + (C '23 -C' 33 Y'c) Z = C '34 Y'c-C' 24 ............ formula (11) is satisfied . When equation (10) and equation (11) are combined,
Equations (5) to (7) are

[0028]

(Equation 3)

It can be rewritten as The components in the third rows of the F and Q matrices indicate project parameters. Here, if X′c is constant, the project parameters can be obtained by using a part of the camera parameters of the aiming camera 7. Specifically, if the laser projector 5 is arranged in a direction parallel to the line of sight of the aiming camera 7, the laser slit light 6 always appears at a fixed position from the aiming camera 7.
In the above method, the project parameters are also automatically calculated and shown to the operator 18 together with the camera parameters. In addition, the positions of the respective measurement points of the manipulator 3 are actually taught as jobs for calibration, so that reproducibility is provided.

[0030]

As described above, according to the present invention, since the relationship between the coordinate system of the manipulator and the coordinate system of the sensor is directly obtained, only one calibration is required, and a three-dimensional measuring device is not required. As a result, labor saving and time reduction of the calibration are realized. Further, since laser light is not irradiated, calibration can be performed safely. In this way, it is possible to achieve a special effect on the efficiency and safety of the calibration, and it can be said that it greatly contributes to this field.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part showing a first embodiment of the present invention.

FIG. 2 is a side view showing a calibration jig used in the present invention.

FIG. 3 is a front view showing an image viewed from an imaging camera during execution of calibration according to the present invention;

FIG. 4 is a block diagram illustrating a circuit configuration according to the first embodiment of the present invention;

FIG. 5 is a perspective view showing an example of a three-dimensional position sensor [conventional example 1].

FIG. 6 is an explanatory diagram showing a relationship between a sensor coordinate system and an object coordinate system in a perspective view.

FIG. 7 is a perspective view showing a state of calibration using the three-dimensional measuring device of Conventional Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Robot main body 2 3D position sensor part 3 Manipulator 4 Calibration jig 5 Laser projector 6 Laser slit light 7 Aiming camera 8 Imaging camera 9 Measurement object 10 Red LED 11 Robot controller 12 CPU 13 Memory 14 Image processing Unit 15 Manipulator control unit 16 I / O (input / output / conversion) unit 17 Operation unit 18 Operator 19 LED of 3D measuring device 20, 21 Camera of 3D measuring device 22 3D measuring device main body 23 3D measuring device console

Claims (4)

[Claims] 1. A jig having a feature point is attached to a manipulator of a robot, and a three-dimensional position of the feature point in a reference coordinate system, and the feature on an imaging surface of two cameras of a sensor unit for imaging and aiming. A method for calibrating a three-dimensional position sensor of a robot, wherein a plurality of combinations with point positions are obtained, and the results are used to calibrate the three-dimensional positions of the two cameras of the sensor unit. 2. The method for calibrating a three-dimensional position sensor of a robot according to claim 1, wherein the laser projector, an aiming camera for aiming a laser beam emitted from the laser emitter, and the aiming camera. An imaging camera that captures the object and the laser light that is attached at a fixed angle at a constant interval from the camera and is mounted on a robot together with the manipulator, and irradiates the object with the laser light, A method for calibrating a three-dimensional position sensor of a robot, comprising: measuring a position of the object based on a principle of triangulation from a position of the laser beam on an imaging surface of the imaging camera. 3. A laser projector mounted on a robot, an aiming camera for aiming a laser beam emitted from the laser emitter, and a fixed angle inclined at a fixed interval from the aiming camera. An imaging camera for imaging the object and the laser beam; a manipulator for moving a calibration jig; an LED provided on the calibration jig; and all controls built in the robot controller. A CPU that performs calculations; a memory that stores data; an image processing unit that processes images of the aiming camera and the imaging camera; a manipulator control unit that controls movement of the manipulator; the laser projector and the LED I to convert input and output to
And a control unit for operating the control unit according to various commands from an operator, and displaying an image and displaying parameters to the operator. Device. 4. The three-dimensional position sensor calibration apparatus for a robot according to claim 3, wherein an LED is mounted on a tip portion of the manipulator capable of changing a position in three dimensions, and the three-dimensional position sensor is blinked by the LED. A calibration device for a three-dimensional position sensor of a robot, wherein the calibration is performed.