JP2012240174A - Calibration device and calibration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a calibration device in which labor and time of calibration caused after starting up the system can be reduced more than those of the first system startup.SOLUTION: The calibration device includes: an estimation means for estimating deviation amount of relative positional relationship between a coordinate system of a three dimension measuring means and a coordinate system of a robot, based on a three dimension position memorized in a second memory means and a three dimension position obtained after starting up the system by the three dimension measuring means; a calculation means for calculating the degree of matching between a two dimension image memorized in the second memory means and a two dimension image obtained after starting up the system by the two dimension measuring means, using the deviation amount estimated by the estimation means; and a correction means for correcting relation information memorized in a first memory means using the deviation amount estimated by the estimation means when the degree of matching calculated by the calculation means is smaller than the threshold amount.

Description

  The present invention relates to a calibration apparatus and a calibration method.

  In order for the robot to work from the information of the vision sensor, it is necessary to convert the coordinate system of the vision sensor to the robot coordinate system, and obtaining this conversion matrix is called calibration.

  It is necessary to perform calibration when the system is started up or when a position shift occurs due to a collision after starting up. The higher the accuracy required for work by the robot, the higher the accuracy required for calibration. For this reason, skilled workers have spent time working, but it takes time and effort, and there are many reworks, which tends to lower the maintainability of a system using a vision sensor that requires calibration.

  On the other hand, in Patent Document 1, the pointing rod is drawn in a rectangle in a state where the pointing rod is gripped by the arm tip of the robot arm device and the pointing rod of the arm tip is projected in the image of the stereo image measuring device. The robot arm is operated as described above, and the coordinate conversion data from the coordinate system of the stereo image measuring device to the coordinate system of the robot arm device is calculated based on the position data at this time. Thereby, according to patent document 1, it is supposed that a calibration operation can be automated.

  Further, in Patent Document 2, in a robot vision system, a checker board is fixed to the tip of a robot arm, and an instruction pin fixed at a mechanically known position is the same point as an intersection on the checker board. It is described that the three-dimensional coordinates of each marker on the checker board in the robot coordinate system are obtained by moving the arm. The right camera and left camera images are analyzed, and the three-dimensional coordinates of the markers on the checker board in the stereo camera coordinate system are obtained. The three-dimensional coordinates of the markers in the robot coordinate system and the stereo camera It is supposed that a rigid body transformation matrix from the stereo camera coordinate system to the robot coordinate system is obtained by associating with the three-dimensional coordinates of the marker in the coordinate system. Thereby, according to patent document 2, it is supposed that a calibration work can be performed automatically.

Japanese Patent No. 3402201 JP 2010-172986 A

  In any of the techniques described in Patent Documents 1 and 2, it is necessary to hold or fix a marker serving as a marker at the tip of a robot arm when performing calibration. For this reason, even after a system start-up, the system is started up even when a position error occurs between the coordinate system of the robot that has already been calibrated and the coordinate system of the vision sensor due to a collision of a predetermined object with the robot. It is necessary to perform the same calibration work as the time. For this reason, the calibration after the system startup requires the same effort and time as those at the system startup.

  For example, when there is a shift in the relative positional relationship between the robot coordinate system and the vision sensor coordinate system in the actual production line, a person enters the production line and causes the robot arm's arm tip to hold the pointer. There is a need. Alternatively, it is necessary to remove the working end effector from the tip of the robot arm and attach a checkerboard to the tip of the robot arm.

  The present invention has been made in view of the above, and an object of the present invention is to provide a calibration device and a calibration method that can reduce the labor and time of calibration after system startup compared to when the system is started up.

  In order to solve the above-described problems and achieve the object, a calibration apparatus according to one aspect of the present invention is a calibration apparatus for calibrating a system having a robot, and is operated by the hand of the robot. A two-dimensional measuring means for acquiring a two-dimensional image around the work area to be performed; a three-dimensional measuring means for acquiring a three-dimensional position around the work area; and a coordinate system of the robot relative to the coordinate system of the three-dimensional measuring means. A first storage means for storing related information describing a relative positional relationship; a two-dimensional image obtained at the time of system startup by the two-dimensional measurement means; and a information obtained at the time of system startup by the three-dimensional measurement means Second storage means for storing a three-dimensional position; three-dimensional position stored in the second storage means; and the three-dimensional measurement means Based on the three-dimensional position acquired after system startup, an estimation unit that estimates a relative positional deviation of the robot coordinate system with respect to the coordinate system of the three-dimensional measurement unit, and the estimation unit Calculation means for calculating a degree of coincidence between the two-dimensional image stored in the second storage means and the two-dimensional image obtained after the system is started up by the two-dimensional measurement means, using the estimated shift amount; And a correction unit that corrects the related information stored in the first storage unit by using the deviation amount estimated by the estimation unit when the degree of coincidence calculated by the calculation unit is smaller than a threshold value. It is characterized by.

  According to the present invention, when a relative positional shift of the coordinate system of the robot with respect to the coordinate system of the three-dimensional measurement unit occurs during system operation, the shift is performed using the measurement data of the two-dimensional measurement unit and the three-dimensional measurement unit. Therefore, there is no need to install a dedicated measurement object for calibration, and there is no need for an operator to enter the robot work area. As a result, it is possible to reduce the labor and time of calibration after the system is started up than when the system is started up.

FIG. 1 is a diagram illustrating a configuration of a calibration apparatus according to an embodiment. FIG. 2 is a diagram illustrating a configuration of the calibration apparatus according to the embodiment. FIG. 3 is a flowchart showing the operation of the calibration apparatus when the system is started up. FIG. 4 is a conceptual diagram showing the positions and orientations of the five observation positions. FIG. 5 is an observation image of the marker at each observation position. FIG. 6 is a flowchart showing the operation of the calibration apparatus after system startup. FIG. 7 is a diagram illustrating a configuration of a calibration apparatus according to a modification of the embodiment.

  Embodiments of a calibration apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
A calibration apparatus 100 according to an embodiment will be described.

  As illustrated in FIG. 1, the calibration apparatus 100 calibrates the robot system RS including the robot RB and the 3D sensor 21. The calibration is to obtain a transformation matrix for performing coordinate transformation from the coordinate system (x, y, z) of the 3D sensor 21 to the coordinate system (X, Y, Z) of the robot RB, for example.

  First, the robot system RS that is the target for calibration performed by the calibration apparatus 100 will be described.

  The robot RB is, for example, a multi-joint robot with 6 degrees of freedom, and a flange RB2 is provided at the tip of the robot arm. For example, a robot hand RB1 is mounted on the flange RB2 as a working tool. The 3D sensor 21 and the 2D sensor 11 are attached to the flange RB2 along with tools such as the robot hand RB1. As a result, the robot RB performs operations such as assembly and processing on a predetermined object placed on the work table WT in the work area WA.

The origin of the robot coordinate system (X, Y, Z) is, for example, on the bottom surface of the base of the robot RB, and is defined with the Z axis as the vertical direction. In FIG. 1, the robot coordinate system (X, Y, Z) is drawn with a slight shift for convenience. The flange coordinate system (X _F , Y _F , Z _F ) is a coordinate system defined for the flange RB2 at the hand of the robot RB, and is similarly drawn slightly shifted in FIG. The position and orientation of the flange coordinate system (X _F , Y _F , Z _F ) are controlled by the robot controller RC.

In order to measure the position of the object using the 3D sensor 21 and operate the robot RB based on the measured position, the position data of the object obtained by the 3D sensor 21 is converted into data on the coordinate system on which the robot RB operates. . That is, the relationship between the coordinate system (x, y, z) of the 3D sensor 21 and the coordinate system (X, Y, Z) in which the robot 30 operates is obtained in advance. Parameters for converting the flange coordinate system (X _F , Y _F , Z _F ) defined in the flange RB2 at the tip of the robot arm into the robot coordinate system (X, Y, Z) are stored in advance in the storage unit RC3 of the robot controller RC. It is remembered. Since the 3D sensor 21 is attached to the flange RB2, parameters (rotation matrix and translation vector) for converting the sensor coordinate system (x, y, z) into the flange coordinate system (X _F , Y _F , Z _F ). ) Should be calibrated. Thereby, the coordinates of the object in the sensor coordinate system detected by the 3D sensor 21 can be converted into coordinates in the flange coordinate system, and further converted into coordinates in the robot coordinate system.

  The robot controller RC includes a central processing unit (CPU) composed of a microprocessor, a ROM memory, a RAM memory, a nonvolatile memory, a digital servo circuit for robot axis control, a servo amplifier, A signal input / output device, a communication interface connected to the image processing device, and the like are provided. These electronic components functionally configure a control unit RC1, a calculation unit RC2, and a storage unit RC3.

Of the memories constituting the storage unit RC3, the ROM memory stores a system program for controlling the system, and the RAM memory is used for temporary storage of data for processing performed by the CPU. The nonvolatile memory stores operation program data and various setting values necessary for system operation. These various setting values include parameters for converting the flange coordinate system (X _F , Y _F , Z _F ) defined in the flange RB2 of the robot RB into the robot coordinate system (X, Y, Z), that is, the flange coordinates Related information (for example, parameters such as a rotation matrix and a translation vector) describing the relative relationship between the system (X _F , Y _F , Z _F ) and the sensor coordinate system (x, y, z) is also included. The robot controller RC controls the position and orientation of the flange RB2 and simultaneously updates and outputs the data in real time. The storage unit RC3 according to the present embodiment is provided inside the robot controller RC, but may be a storage device provided outside.

  The manual operation panel PA is a panel for manually operating the robot RB, and the robot RB can be manually operated by operating buttons, joysticks, and the like provided on the panel.

  Next, the configuration of the calibration apparatus 100 will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of the calibration apparatus 100.

  The calibration device 100 includes a control unit 90, a two-dimensional measurement unit 10, a three-dimensional measurement unit 20, a first storage unit 30, a second storage unit 40, an estimation unit 50, a calculation unit 60, a comparison unit 65, and a correction unit. 70 and a display unit 80.

  The control unit 90 generally controls each unit in the calibration apparatus 100.

  The two-dimensional measuring unit 10 acquires a two-dimensional image around the work area WA. The work area WA is an area for performing work by the robot hand RB1 of the robot RB. For example, the two-dimensional measurement unit 10 acquires a two-dimensional image at each of a plurality of measurement positions around the work area WA.

  Specifically, the two-dimensional measurement unit 10 includes a 2D sensor 11 and a signal processing unit 12. The 2D sensor 11 captures a two-dimensional image at each of a plurality of measurement positions, and a plurality of images captured by the 2D sensor 11. The signal processing unit 12 performs predetermined signal processing (analog signal processing or the like) on the image signal of the two-dimensional image.

  The two-dimensional measurement unit 10 supplies, for example, the acquired two-dimensional images at a plurality of measurement positions to the second storage unit 40 via the control unit 90 when the system is started up. The two-dimensional measurement unit 10 supplies, for example, the acquired two-dimensional images at a plurality of measurement positions to the calculation unit 60 via the control unit 90 after starting up the system.

  The three-dimensional measuring unit 20 acquires a three-dimensional position around the work area WA. For example, the three-dimensional measurement unit 20 acquires a three-dimensional position at each of a plurality of measurement positions around the work area WA. The three-dimensional measurement unit 20 supplies the acquired three-dimensional positions of a plurality of measurement positions, for example, to the second storage unit 40 or the estimation unit 50 via the control unit 90.

  Specifically, the three-dimensional measurement unit 20 includes a 3D sensor 21, a signal processing unit 22, and a calculation unit 23, and the 3D sensor 21 includes a right sensor 211 and a left sensor 212. A two-dimensional image of each of a plurality of measurement positions is captured by the right sensor 211, a two-dimensional image of each of the plurality of measurement positions is captured by the left sensor 212, and a plurality of two images captured by the right sensor 211 and the left sensor 212 are captured. The signal processing unit 22 performs predetermined signal processing (analog signal processing or the like) on the image signal of the three-dimensional image to generate a three-dimensional image signal, and the calculation unit 23 uses a plurality of measurement positions from the generated three-dimensional image signal. Is obtained.

  The three-dimensional measurement unit 20 supplies, for example, the acquired three-dimensional positions of a plurality of measurement positions to the second storage unit 40 via the control unit 90 when the system is started up. The three-dimensional measuring unit 20 supplies, for example, the acquired three-dimensional positions of a plurality of measurement positions to the estimating unit 50 via the control unit 90 after starting up the system.

The first storage unit 30 is included in, for example, the storage unit RC3 of the robot controller RC described above, and stores related information 31. The related information 31 is information describing the relative positional relationship of the coordinate system (X, Y, Z) of the robot with respect to the coordinate system of the three-dimensional measuring unit 20, that is, the sensor coordinate system (x, y, z). Related information 31 is, for example, the sensor coordinate system (x, y, z) a flange coordinate system _{(X F, Y F, Z} F) parameters be converted into (e.g., parameters such as a rotation matrix _{R h} and translation vector _{T h} ) And parameters for converting the flange coordinate system (X _F , Y _F , Z _F ) to the robot coordinate system (X, Y, Z) (for example, parameters such as the rotation matrix R _f and the translation vector T _f ), etc. .

For example, the sensor coordinate system (x, y, z) is converted into the flange coordinate system (X _F , Y _F , Z _F ) by the following formula (1).

Further, for example, the flange coordinate system (X _F , Y _F , Z _F ) is converted into the robot coordinate system (X, Y, Z) by the following formula (2).

すなわち、この式がセンサ座標系（ｘ，ｙ，ｚ）をロボット座標系（Ｘ，Ｙ，Ｚ）に変換する式である。 Combining Equation (1) and Equation (2) yields the following Equation (3).

That is, this expression is an expression for converting the sensor coordinate system (x, y, z) to the robot coordinate system (X, Y, Z).

  The second storage unit 40 receives and stores the two-dimensional image acquired at the time of system startup from the two-dimensional measurement unit 10 via the control unit 90. For example, the second storage unit 40 stores two-dimensional images at a plurality of measurement positions as a two-dimensional image group 41. In the two-dimensional image group 41, a measurement position and a two-dimensional image are associated with each other for a plurality of measurement positions.

  The second storage unit 40 receives and stores the three-dimensional position acquired at the time of system startup from the three-dimensional measurement unit 20 via the control unit 90. For example, the second storage unit 40 stores three-dimensional positions of a plurality of measurement positions as a three-dimensional position group 42. In the three-dimensional position group 42, the measurement position and the three-dimensional position are associated with each other for a plurality of measurement positions.

  The estimation unit 50 receives the three-dimensional position acquired after the system startup from the three-dimensional measurement unit 20 via the control unit 90. In response to this, the estimation unit 50 accesses the second storage unit 40 via the control unit 90, and reads the three-dimensional position acquired at the time of system startup from the second storage unit 40 via the control unit 90. Then, the estimation unit 50 is a robot for the coordinate system (x, y, z) of the three-dimensional measurement unit 20 based on the three-dimensional position acquired at the time of system startup and the three-dimensional position acquired after the system startup. The amount of shift in the relative positional relationship of the RB coordinate system (X, Y, Z) is estimated. The estimation unit 50 supplies the estimated deviation amount to the calculation unit 60 via the control unit 90.

  The calculation unit 60 receives the estimated shift amount from the estimation unit 50 via the control unit 90. Further, the calculation unit 60 receives a two-dimensional image acquired after the system startup from the two-dimensional measurement unit 10 via the control unit 90. In response to this, the calculation unit 60 accesses the second storage unit 40 via the control unit 90, and reads the two-dimensional image acquired at the time of system startup from the second storage unit 40 via the control unit 90. Then, the calculation unit 60 calculates the degree of coincidence between the two-dimensional image acquired at the time of system startup and the two-dimensional image acquired after the system startup, using the deviation amount estimated by the estimation unit 50. For example, the calculation unit 60 calculates the individual coincidence between the two-dimensional image acquired at the time of system startup and the two-dimensional image acquired after the system startup for each of a plurality of measurement positions. A total sum of the calculated individual matching degrees is obtained, and the total is calculated as the above matching degree. The calculation unit 60 supplies the calculated degree of coincidence to the comparison unit 65 via the control unit 90.

  The comparison unit 65 receives the calculated degree of coincidence from the calculation unit 60 via the control unit 90. The comparison unit 65 compares the calculated degree of coincidence with a threshold value, and supplies the comparison result to the correction unit 70 and the display unit 80 via the control unit 90.

  The correction unit 70 receives the comparison result from the comparison unit 65 via the control unit 90. When the comparison result indicates that the degree of coincidence calculated by the calculation unit 60 is smaller than the threshold value, the correction unit 70 stores the amount of deviation estimated by the estimation unit 50 in the first storage unit 30. The related information 31 is corrected.

  The display unit 80 receives the comparison result from the comparison unit 65 via the control unit 90. When the comparison result indicates that the degree of coincidence calculated by the calculation unit 60 is equal to or greater than the threshold value, the display unit 80 displays an object indicating a direction to be corrected according to the deviation amount estimated by the estimation unit 50. The image related to the robot RB is displayed in an overlapping manner. Specifically, the display unit 80 includes a display 81 and a display control unit 82. For example, the direction to be corrected illustrated in FIG. Display data in which objects indicated by arrows are superimposed is generated by the display control unit 82, and an image as shown in FIG. 1 corresponding to the display data is displayed on the display 81.

  Next, the operation of the calibration apparatus 100 when the system of the robot system RS is started will be described with reference to FIG. FIG. 3 is a flowchart showing the operation of the calibration apparatus 100 when the system is started up.

  In step S1, the calibration apparatus 100 performs calibration (full calibration) using the marker MK as shown in FIG.

Specifically, the marker MK is disposed on the work table WT (see FIG. 1). The operator operates the manual operation panel PA of the robot RB, sequentially controls the position and orientation of the hand of the robot RB, and executes the detection of the marker MK by the three-dimensional measuring unit 20 for example five times. The RB attitude data R _f and T _f and the coordinates of the marker MK on the sensor coordinate system are recorded in association with each other. At this time, the marker MK (for example, white, black, etc.) is observed at the first to third observation points (for example, observation 1, observation 2, observation 3 shown in FIG. 4) where the hand is moved by the position without changing the posture. The marker MK is observed at the fourth and fifth observation points (for example, observation 4 and observation 5 shown in FIG. 4) in which observations are made on the intersections of diagonal lines in alternately painted patterns, and then both the hand position and posture are changed. (See FIG. 5).

For each observation, the rotation matrix Rf representing the position and orientation of the flange coordinate system (X _F , Y _F , Z _F ) output from the robot controller RC and the translation vector Tf are observed output from the image processing device. The marker MK is recorded in association with the sensor coordinate system (x, y, z).

  An equation that does not include a translation vector is obtained from the first to third observation points, and a rotation matrix is easily obtained. From the first, fourth, and fifth observation points, a general form including a rotation matrix and a translation vector is obtained. Although an equation is obtained, if the rotation matrix is known, an equation with only a translation vector is obtained, and the translation vector can be easily obtained.

For example, the sensor of the marker MK when the posture of the flange RB2 is fixed to _Rfc , that is, the marker MK is observed by moving to the two positions _Tf1 and _Tf2 while keeping the posture of the 3D sensor 21 the same. If the coordinate values on the coordinate system are (x ₁ , y ₁ , z ₁ ) and (x ₂ , y ₂ , z ₂ ), respectively, the coordinates of the marker MK in the robot coordinate system are the same. ) Holds.

When formula (4) is transformed, the following formula (5) is obtained.

Similarly, when the same marker MK is observed by moving to the third position _Tf3 while maintaining the same posture of the 3D sensor 21, the following equation (6) is obtained.

Equation (5), unknowns in Equation (6) is _{R h. Rh} is a 3 × 3 matrix consisting of 9 elements, but since it is a rotation matrix, there is a constraint that the sum of squares of the elements in each column (each row) is 1, and (x ₁ , y ₁ , If z ₁ ), (x ₂ , y ₂ , z ₂ ), and (x ₃ , y ₃ , z ₃ ) are different from each other, the simultaneous equations consisting of Equation (5) and Equation (6) are solved to obtain R _h Can be determined uniquely.

  In this way, after the calibration at the time of starting the system (step S1), the processing of step S2 to step S7 is performed as advance preparation for recalibration after the system is started.

  In step S2, the operator operates the manual operation panel PA of the robot RB to register N measurement positions P (i) (i = 1, 2,..., N) around the work area WA, and the robot controller Save to RC or computer memory. Then, the calibration apparatus 100 sets an initial value 0 to the parameter i for identifying the measurement position.

  In step S3, the calibration apparatus 100 increments the parameter i for identifying the measurement position. For example, for the first time, the calibration apparatus 100 sets i = 1.

  In step S4, the calibration apparatus 100 moves the robot RB to the measurement position P (i). For example, for the first time, the calibration apparatus 100 moves the robot RB to the measurement position P (1).

  In step S5, the calibration apparatus 100 acquires 3D point cloud data bPnt (i) as a three-dimensional position of the measurement position P (i). For example, for the first time, the calibration apparatus 100 acquires 3D point cloud data bPnt (1) of the measurement position P (1) and stores it in the second storage unit 40.

  In step S6, the calibration apparatus 100 acquires a 2D image bImg (i) as a two-dimensional image at the measurement position P (i). For example, at the first time, the calibration apparatus 100 acquires the 2D image bImg (1) at the measurement position P (1) and stores it in the second storage unit 40.

  In step S7, the calibration apparatus 100 determines whether or not the parameter i for identifying the measurement position is smaller than the upper limit value N. When the parameter i is smaller than the upper limit value N (Yes in step S7), the calibration apparatus 100 returns the process to step S3, assuming that there is an unmeasured measurement position, and the parameter i is greater than or equal to the upper limit value N. (No in step S7), the process is terminated assuming that all the measurement positions have been measured.

  In this way, at each measurement position P (i) (i = 1, 2,..., N), the 2D image bImg (i) and the three-dimensional point group data bPnt (i) are respectively measured, and the second Saved in the storage unit 40.

  Next, the operation of the calibration apparatus 100 after the system startup of the robot system RS will be described with reference to FIG. FIG. 6 is a flowchart showing the operation of the calibration apparatus 100 after the system is started up.

  The calibration apparatus 100 detects that a deviation has occurred in the relative positional relationship of the robot coordinate system (X, Y, Z) with respect to the sensor coordinate system (x, y, z) by using a predetermined sensor (not shown). Then, the simple calibration correction process after step S11 is started.

  In step S11, the calibration apparatus 100 sets an initial value 0 to the parameter i for identifying the measurement position.

  In step S12, the calibration apparatus 100 increments the parameter i for identifying the measurement position. For example, for the first time, the calibration apparatus 100 sets i = 1.

  In step S13, the calibration apparatus 100 moves the robot RB to the measurement position P (i). For example, for the first time, the calibration apparatus 100 moves the robot RB to the measurement position P (1).

  In step S14, the calibration apparatus 100 acquires 3D point cloud data aPnt (i) as a three-dimensional position of the measurement position P (i). For example, if it is the first time, the calibration apparatus 100 acquires 3D point cloud data aPnt (1) at the measurement position P (1).

  In step S15, the calibration apparatus 100 determines whether or not the parameter i for identifying the measurement position is smaller than the upper limit value N. When the parameter i is smaller than the upper limit value N (Yes in step S15), the calibration apparatus 100 returns the process to step S12, assuming that there is an unmeasured measurement position, and the parameter i is greater than or equal to the upper limit value N. (No in step S15), the process proceeds to step S16 on the assumption that all the measurement positions have been measured.

  In this way, the 3D point cloud data aPnt (i) is measured at each measurement position P (i) (i = 1, 2,..., N).

  In step S <b> 16, the calibration apparatus 100 estimates a shift amount of the relative positional relationship of the robot coordinate system (X, Y, Z) with respect to the sensor coordinate system (x, y, z). Specifically, the calibration apparatus 100 estimates a rotation matrix (rotation component) R and a translation vector (translation component) T that minimize the value of the following formula (7).

_N
Σ {bPnt (i) − (R · aPnt (i) + T)} (7)
^{i = 1}
The estimation method is not limited to a specific method, and any method may be used. For example, the rotation matrix R and the translation vector T can be obtained by a technique called an ICP (Iterative Closest Point) method.

  In step S17, the calibration apparatus 100 sets an initial value 0 to a parameter i for identifying a measurement position.

  In step S18, the calibration apparatus 100 increments the parameter i for identifying the measurement position. For example, for the first time, the calibration apparatus 100 sets i = 1.

  In step S19, the calibration apparatus 100 corrects the measurement position using the deviation amount (for example, the rotation matrix R and the translation vector T) estimated in step S16. For example, the calibration apparatus 100 calculates the corrected P ′ (i) using the following formula (8).

      P ′ (i) = R · P (i) + T (8)

  In step S20, the calibration apparatus 100 moves the robot RB to the measurement position P ′ (i). For example, for the first time, the calibration apparatus 100 moves the robot RB to the measurement position P ′ (1).

  In step S21, the calibration apparatus 100 acquires a 2D image aImg (i) as a two-dimensional image at the measurement position P ′ (i). For example, for the first time, the calibration apparatus 100 acquires the 2D image aImg (1) at the measurement position P ′ (1).

  In step S22, the calibration apparatus 100 uses the individual coincidence degree E (i) that is the degree of coincidence between the 2D image bImg (i) acquired at the time of system startup and the 2D image aImg (i) acquired after the system startup. ). For example, at the first time, the calibration apparatus 100 determines the individual coincidence degree that is the coincidence degree between the 2D image bImg (1) acquired at the time of system startup and the 2D image aImg (1) acquired after the system startup. E (1) is calculated. For example, the definition of the degree of coincidence may be evaluated using the background difference of the image.

  In step S23, the calibration apparatus 100 determines whether or not the parameter i for identifying the measurement position is smaller than the upper limit value N. When the parameter i is smaller than the upper limit value N (Yes in step S23), the calibration apparatus 100 returns the process to step S18, assuming that there is an unmeasured measurement position, and the parameter i is greater than or equal to the upper limit value N. (No in step S23), the process proceeds to step S24 assuming that the measurement of all measurement positions has been completed.

  In this way, the 2D image aImg (i) is measured at each measurement position P ′ (i) (i = 1, 2,..., N), and the corresponding measurement positions P (i) and P ′ (i) are measured. ) (I = 1, 2,..., N), the individual matching degree E (i) is calculated.

In step S24, the calibration apparatus 100 determines whether or not the sum of the individual matching degrees E (i) is larger than the threshold value T _E. That is, the calibration apparatus 100 determines whether or not the following formula (9) is satisfied.

_N
ΣE (i)> T _E (9)
^{i = 1}

  When the mathematical formula (9) does not hold (No in step S24), the calibration apparatus 100 shifts the relative positional relationship of the robot coordinate system (X, Y, Z) with respect to the sensor coordinate system (x, y, z). Assuming that the amount is within the correctable range, the process proceeds to step S25. Alternatively, when the mathematical formula (9) is satisfied (Yes in step S24), the calibration apparatus 100 determines the relative positional relationship of the robot coordinate system (X, Y, Z) with respect to the sensor coordinate system (x, y, z). Assuming that the deviation amount exceeds the correctable range, the process proceeds to step S26.

In step S25, the calibration apparatus 100 corrects the shift amount calculated in step S16 (for example, the rotation matrix R and the translation vector T) in the conversion matrix calculated when the system is started up. For example, the calibration device 100, the rotation matrix _{R h} in Equation (1), with respect to the translation vector _{T h,} respectively, the rotation matrix R, a new rotation matrix obtained by adding the translation vector T _{R h,} the translation vector T Correction to _h is performed.

  In step S26, the calibration apparatus 100 performs full calibration.

  Here, when performing full calibration from the beginning, if the same processing as step S1 is performed, the measurement position and orientation of the calibration marker MK and the jig are changed through trial and error with each of the 2D sensor and the 3D sensor. I have to do it.

  On the other hand, in the present embodiment, the calibration apparatus 100 displays an object indicating the direction to be corrected according to the estimated deviation amount superimposed on the image related to the robot RB. For example, the display control unit 82 generates display data in which, for example, an arrow object indicating the direction to be corrected shown in FIG. 1 is superimposed on the two-dimensional image acquired after the system is started up by the two-dimensional measurement unit 10, and the display is performed. An image as shown in FIG. 1 corresponding to the data is displayed on the display 81. As a result, it is possible to indicate the direction in which direction the next necessary information is obtained in order to perform calibration correction in which direction. That is, full calibration can be performed more easily than in step S1.

  For example, how to move bPnt (i) using the three-dimensional point cloud data bPnt (i) and aPnt (i) (i = 1, 2,..., N) before and after the positional deviation, aPnt (i ), A rotation matrix R and a translation vector T that minimize Equation (7) are calculated. Then, after each measurement position for calibration is converted by the rotation matrix R and the translation vector T, the operator performs fine correction according to the object indicated by the arrow while viewing the live image. After making minor corrections, the calibration program is run to complete the re-startup after misalignment.

  As described above, in the embodiment, the calibration apparatus 100 acquires a two-dimensional image and a three-dimensional position around the work area in advance when the system startup is completed. When the relative relationship between the sensor coordinate system and the robot coordinate system changes due to a collision, or when the 3D sensor is changed by removing and reattaching the 3D sensor for the purpose of adjusting or repairing the sensor itself, the 2 around the work area again. A three-dimensional image and a three-dimensional position are acquired. The correction parameter of the calibration data is calculated by calculating the amount of positional deviation between the three-dimensional point cloud data before and after the occurrence of the positional deviation, and the degree of coincidence between the two-dimensional images before and after the occurrence of the positional deviation is calculated and compared with the threshold value Thus, it is determined whether or not the positional deviation amount is within a correctable range. As a result, when the relative relationship between the robot and the vision sensor is shifted due to a collision or reattachment, the positional shift amount can be automatically corrected and restored if the shift amount is within a correctable range.

  Therefore, when a misalignment occurs during system operation, it is not necessary to perform zero-based full calibration, and 2D and 3D sensor data obtained by photographing the environment around the work area is used, so that the 2D sensor or 3D sensor is fixed. If it is possible, there is no need to install a dedicated measurement object for calibration, and there is no need for an operator to enter the work area of the robot. For this reason, the labor and time of recalibration can be shortened. That is, it is possible to reduce the labor and time of calibration after starting up the system compared to when starting up the system.

  Further, in the embodiment, the calibration apparatus 100 displays an object indicating the direction to be corrected according to the estimated shift amount, superimposed on the image related to the robot RB. As a result, the directionality to be corrected is indicated, so that even if the deviation amount exceeds the correctable range, the calibration teaching operation to be re-executed thereafter can be supported and the system can be quickly restored.

  Note that the display unit 80 i of the calibration apparatus 100 i may include an AR (Augmented Reality) tool 81 i as shown in FIG. 7 instead of the display 81 or in addition to the display 81. That is, the worker WP is provided with the AR tool 81i, and the display control unit 82 (see FIG. 2) of the display unit 80i communicates with the AR tool 81i through, for example, a wireless communication line, and sends data to be displayed to the AR tool 81i. Send. In this way, support that facilitates correction of the measurement position may be performed by indicating the direction in which the robot should be moved on the display of the AR tool 81i.

  As described above, the calibration apparatus according to the present invention is useful for calibration of a system having a robot.

DESCRIPTION OF SYMBOLS 10 2D measuring part 20 3D measuring part 30 1st memory | storage part 40 2nd memory | storage part 50 Estimating part 60 Calculation part 80, 80i Display part 100, 100i Calibration apparatus

Claims (4)

A calibration device for calibrating a system having a robot,
Two-dimensional measuring means for acquiring a two-dimensional image around a work area where work is performed by the hand of the robot;
Three-dimensional measuring means for acquiring a three-dimensional position around the work area;
First storage means for storing related information describing a relative positional relationship of the coordinate system of the robot with respect to the coordinate system of the three-dimensional measurement means;
Second storage means for storing a two-dimensional image acquired at system startup by the two-dimensional measurement means and a three-dimensional position acquired at system startup by the three-dimensional measurement means;
Based on the three-dimensional position stored in the second storage means and the three-dimensional position acquired after the system is started up by the three-dimensional measurement means, the coordinate system of the robot with respect to the coordinate system of the three-dimensional measurement means An estimation means for estimating the amount of relative positional deviation;
The degree of coincidence between the two-dimensional image stored in the second storage unit and the two-dimensional image obtained after the system is started up by the two-dimensional measurement unit is calculated using the deviation amount estimated by the estimation unit. Calculation means;
When the degree of coincidence calculated by the calculating unit is smaller than a threshold value, a correcting unit that corrects the related information stored in the first storage unit using the deviation amount estimated by the estimating unit;
A calibration apparatus comprising: Display means for displaying an object indicating a direction to be corrected in accordance with the amount of deviation estimated by the estimation means in an overlapping manner with an image related to the robot when the degree of coincidence calculated by the calculation means is equal to or greater than the threshold. The calibration device according to claim 1, comprising: a calibration device. A calibration method for calibrating a system having a robot,
A first two-dimensional measurement step of acquiring a two-dimensional image around a work area where work is performed by a hand of the robot at the time of starting the system;
A first three-dimensional measurement step of acquiring a three-dimensional position around the work area by a three-dimensional measurement means when the system is started up;
A first storage step for storing related information describing a relative positional relationship of the coordinate system of the robot with respect to the coordinate system of the three-dimensional measuring means;
A second storage step for storing the two-dimensional image acquired by the first two-dimensional measurement means and the three-dimensional position acquired by the first three-dimensional measurement step;
A second two-dimensional measurement step of acquiring a two-dimensional image around the work area after the system is started;
A second three-dimensional measurement step for obtaining a three-dimensional position around the work area after the system is started;
Based on the three-dimensional position stored in the second storage step and the three-dimensional position acquired in the second three-dimensional measurement step, the robot coordinate system is relative to the coordinate system of the three-dimensional measurement means. An estimation step for estimating the amount of deviation of a typical positional relationship;
Calculation for calculating the degree of coincidence between the two-dimensional image stored in the second storage step and the two-dimensional image acquired in the second two-dimensional measurement step, using the deviation amount estimated in the estimation step. Steps,
When the degree of coincidence calculated in the calculation step is smaller than a threshold value, a correction step of correcting the related information stored in the first storage step using the deviation amount estimated in the estimation step;
A calibration method characterized by comprising: When the degree of coincidence calculated in the calculating step is equal to or greater than the threshold value, a display step of displaying an object indicating a direction to be corrected according to the amount of deviation estimated in the estimating step on an image related to the robot. The calibration method according to claim 3, wherein the calibration method is provided.

Images