Patent Application
20230302651
The present invention relates to a target detection method and detection device including a calibration function.
Conventionally, there is known a technique that welds a workpiece with another workpiece while gripping the workpiece by an arm robot. In this case, a dedicated positioning mechanism (including a mold or a jig for positioning) is used to position (detect positions and postures of) not only the arm robot, but also the workpiece gripped by the arm robot. However, the positioning mechanism needs to be separately provided, and therefore equipment cost is high and a wide equipment installation space is necessary. Moreover, positioning mechanisms the number of which corresponds to the number of car models are necessary, and, therefore when the number of car models is large, the number of times of set-up changes becomes large, and a total set-up change time becomes longer. Furthermore, every time a new car model is launched, a similar problem occurs.
Patent Literature 1 describes a method for positioning at least one object at a final posture in a space by an industrial robot. This method uses a first industrial robot, a first optical imaging device, and at least one second optical imaging device to position the object. The first industrial robot can adjust the object to a predetermined position. The first optimal imaging device is calibrated in a three-dimensional spatial coordinate system, and is positioned at a known first position in a known direction. The second optimal imaging device is calibrated in the three-dimensional spatial coordinate system, and is positioned at a known second position in the known direction.
The first optical imaging device includes a first camera, a first driving unit, and a first angle measurement unit. The first camera is optically calibrated to capture an image in a predetermined first field of view. The first driving unit is a component that determines a direction of the first camera to adjust a position of the first field of view. The first angle measurement unit detects an angular direction of the first camera, and is calibrated in the spatial coordinate system for finding the first field of view in the spatial coordinate system.
The second optical imaging device includes a second camera, a second driving unit, and a second angle measurement unit. The second camera is optically calibrated to capture an image in a predetermined second field of view. The second driving unit is a component that determines a direction of the second camera to adjust a position of the second field of view. The second angle measurement unit detects an angular direction of the second camera, and is calibrated in the spatial coordinate system for finding the second field of view in the spatial coordinate system.
However, Patent Literature 1 does not describe a function of calibrating a change (such as a temperature) in external environment, has difficulty in maintaining accuracy set at a beginning, and therefore has had a room for improvement.
The present invention has been made based on an awareness of the above-described problem, and an object of the present invention is to provide a target detection method and detection device that include a calibration function and can maintain detection accuracy of a target irrespectively of a change (such as a temperature) in external environment.
A target detection method including a calibration function according to the present embodiment includes: a step of calculating a quantitative value; a step of, at a first position information generation device, measuring a first target; a step of, at a second position information generation device, measuring a second target; a step of calculating a position of the second target using the first position information generation device as a position reference based on a measurement value of the first target obtained by the first position information generation device, a measurement value of the second target obtained by the second position information generation device, and the quantitative value; and a step of calibrating the quantitative value before measuring a third target using the second position information generation device.
According to the present invention, it is possible to provide a target detection method and detection device that include a calibration function and can maintain detection accuracy of a target irrespectively of a change (such as a temperature) in external environment.
First, terms in this description are defined.
A “position information generation device (3D scanner)” in this description is a device that obtains shape information of workpieces (e.g., an upper sash, an upright column sash, a door frame, a bracket, or the like) and a grip device (e.g., a robot arm or the like) of the workpiece, and other targets (e.g., a robot arm, or a marker or a fixed object provided near the robot arm) as point group data. Each point information of the point group data can be read as “a position and a posture of a target”. Each point information (the position and the posture of the target) of the point group data can be expressed as numerical values of coordinates X, Y, and Z whose origin is a 3D scanner origin, and normal directions I, J, and K of the coordinates X, Y, and Z. In this description, a “3D scanner” is also referred to as a “second position information generation device”.
The “position information generation device (laser tracker)” in this description is, for example, a device that can calculate three-dimensional information (position information and an angle) of a target based on an own coordinate system of the position information generation device. The “position information generation device (laser tracker)” radiates, for example, laser light, and obtains three-dimensional position information of a target when the laser light reflected by the target returns to a light emission source. Three-dimensional information of a target (position information and an angle) can be read as “a position and a posture of a target”. The “position information generation device (laser tracker)” has a wide measurement range, so that, if there are the “position information generation device (laser tracker)” and the target or a touch probe with a marker described later, it is possible to accurately calculate a dimension between each equipment, accuracy, an origin position, and the like. In this description, the “position information generation device (laser tracker)” is also referred to as a “first position information generation device”.
The “marker” in this description is, for example, one type of a target for the first position information generation device (laser tracker) and the second position information generation device (3D scanner) to obtain position coordinates and angles. The position coordinates and the angles of the “marker” are calculated using the first position information generation device (laser tracker) or the second position information generation device (3D scanner) as an origin. The position coordinates and the angles can be expressed as the coordinates X, Y, and Z and angles Rx, Ry, and Rz, and the angles Rx, Ry, and Rz can be each expressed by 4×4 matrix data (matrix data) that uses unit vectors (I, J, and K) of change amounts from a reference X axis, a reference Y axis, and a reference Z axis, and movement amounts (X, Y, and Z) from a reference point as described later. The “marker” is attached to, for example, a grip part at a distal end of a robot arm, and is used to obtain, as a numerical value, operation accuracy of the robot arm (an absolute position of the grip part on a three-dimensional space) that uses the first position information generation device (laser tracker) or the second position information generation device (3D scanner) as the origin. Furthermore, the marker is additionally used widely for a touch probe with a marker for contacting and measuring a target workpiece as described later, a type of a marker attached to a 3D scanner for measuring a target workpiece without contact, or the like. For any measurement information, the marker is used for arranging a workpiece at the origin of the first position information generation device (laser tracker) or the second position information generation device (3D scanner).
The “touch probe with the marker” in this description refers to, for example, a touch probe that can calculate a position of a target workpiece on a three-dimensional space that uses the first position information generation device (laser tracker) or the second position information generation device (3D scanner) as the origin by making a probe distal end touch and measure the target workpiece in a state where the first position information generation device (laser tracker) or the second position information generation device (3D scanner) locks onto a target part of the “touch probe with the marker”.
The “3D scanner with the marker” in this description can calculate point group information obtained by the second position information generation device (3D scanner) as the origin of the first position information generation device (laser tracker) from a marker origin coordinate/angle from the origin of the first position information generation device (laser tracker) and an origin coordinate/angle (described later) of the second position information generation device (3D scanner) from the marker origin by, for example, 3D-scanning a target workpiece in a state where, for example, the first position information generation device (laser tracker) locks onto a target part of the “3D scanner with the marker”. As for a relationship between the marker origin position and the origin position of the second position information generation device (3D scanner), at a time of installation, position information of a reference block calculated by using the first position information generation device (laser tracker) and the touch probe with the marker, and position information of the reference block captured by the second position information generation device (3D scanner) are matched (calibrated) to calculate origin/angle information of the second position information generation device (3D scanner). Generally, the second position information generation device (3D scanner) has characteristics that accuracy lowers when an image capturing range is widened, and therefore is not suitable for capturing images in a wide range, and the second position information generation device (3D scanner) alone has a limitation for an operation of entire equipment described later. Therefore, a measure to use the first position information generation device (laser track) is taken to widen the image capturing range and a measurement range. However, as described later, by appropriately combining the first position information generation device (laser tracker) and the second position information generation device (3D scanner), the target detection method and detection device according to the present embodiment can use the first position information generation device (laser tracker) only for initial setting (calibration), and then correct a final position using the second position information generation device (3D scanner) and a shape marker. Consequently, for example, it is not necessary to equip the dedicated first position information generation device (laser tracker) with each of a plurality of manufacturing lines, and use the first position information generation device (laser tracker) between the plurality of manufacturing lines.
“Point group data” in this description means, for example, three-dimensional information of workpieces obtained by 3D-scanning the workpieces (by capturing images of the workpieces) (e.g., an upper sash, an upright column sash, a door frame, a bracket, and the like) using a device such as a 3D scanner (camera). Furthermore, as illustrated in, for example,
“Reference data” in this description means, for example, data (e.g., masterwork data, design value data, raw data, or CAD data) that serves as criteria for design of the workpieces (e.g., the upper sash, the upright column sash, the door frame, the bracket, and the like).
“Shape fitting point group data” in this description means point group data obtained by matching the above-described “point group data” with the “reference data”.
A “translation matrix” and an “inverse matrix” in this description are expressed by, for example, 4×4 matrix data (matrix data). As illustrated in, for example,
By using the matrix, it is possible to calculate the movement amount of each coordinate as illustrated in
The welding device 1 includes a fixing jig (e.g., a jig of a tact system) 10 that is located at a device center part. The fixing jig 10 supports a welded door frame 11 in a fixed state in a state where, for example, an end part of an upper sash (front main frame) and an end part of an upright column sash (front upright column frame) are aligned. A relative positional relationship between the fixing jig 10 and the doorframe 11 may change every time a workpiece is attached or detached, and therefore a repeatedly positioning function required for normal jigs is unnecessary (because a workpiece position of the door frame 11 is calculated based on an inverse matrix described later). Therefore, the fixing jig 10 may fix any position of the doorframe 11. Note that, for a reason of ease of drawing,
The welding device 1 includes a robot arm 20 and a robot arm 30 that are located on a left side and a right side, respectively, with the fixing jig 10 interposed therebetween in
A relative positional relationship between the robot arm 20 and the lock bracket (illustrated as the bubble in
The welding device 1 includes a welding robot 40 at a position shifted in a depth direction between the fixing jig 10 and the robot arm 20, and a welding robot 50 at a position shifted in the depth direction between the fixing jig 10 and the robot arm 30. The welding robot 40 is configured as, for example, an arm robot that has a plurality of axes (e.g., six axes), and a welding nozzle 41 provided at a distal end part welds the doorframe 11 supported by the fixing jig 10, and the lock bracket gripped by the grip part 21 of the robot arm 20 in a predetermined aligned state. The welding robot 50 is configured as, for example, an arm robot that has a plurality of axes (e.g., six axes), and a welding nozzle 51 provided at a distal end part welds the door frame 11 supported by the fixing jig 10, and the hinge bracket gripped by the grip part 31 of the robot arm 30 in a predetermined aligned state.
The welding device 1 includes a 3D scanner support arm 60 at a rear side of the fixing jig 10 by being sandwiched between the welding robot 40 and the welding robot 50. The 3D scanner support arm 60 is configured as, for example, an arm robot that has a plurality of axes (e.g., six axes), and has an arm distal end part provided with a second position information generation device (3D scanner) 61 and a position correction marker 62. The position correction marker 62 includes, for example, a reflector that can be tracked by the first position information generation device (laser tracker) 70 describe below.
The welding device 1 may be combined with the first position information generation device (laser tracker) 70 and used. The first position information generation device (laser tracker) 70 targets at each component of the welding device 1 (e.g., the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, the hinge bracket gripped by the robot arm 30, the position correction marker 22 of the robot arm 20, the position correction marker 32 of the robot arm 30, the 3D scanner 61, and the position correction marker 62 of the 3D scanner 61), and calculates three-dimensional information (position information and an angle) of each component based on a coordinate system of the first position information generation device 70.
As illustrated in
In the present embodiment, the 3D scanner 61 with the marker is used to scan (capture) the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30, and thereby obtain point group data (three-dimensional information) thereof. That is, the 3D scanner 61 with the marker functions as a “point group data obtaining section”. Furthermore, by obtaining point groups in a state where the first position information generation device (laser tracker) 70 virtually locks onto the 3D scanner 61 with the marker, the point group data obtained by the 3D scanner 61 with the marker is calculated using the first position information generation device (laser tracker) 70 as an origin (the point group data is calculated as a virtual origin accompanying the virtual lock-on of the first position information generation device (laser tracker) 70). This point group data is expressed as, for example, the coordinates X, Y, and Z of each point and the normal directions I, J, and K of the coordinates X, Y, and Z, and an origin of the point group data is expressed by 4×4 matrix data (matrix data) (details will be described later).
In this regard, when the point group data is obtained, all of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30 may be not be 3D-scanned, but part of the doorframe 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30 such as only portions that serve as criteria for product evaluation may be 3D-scanned. This 3D scan may adopt a scheme that obtains a point group while moving a 2D scanner, a scheme that positions a 3D scanner to perform scanning, or a scheme that installs fixed 3D scanners at a plurality of portions to perform scanning. As described later, when point group data is matched with reference data, it is possible to set a necessary number of arbitrary positions on reference data as position references, and align the point group data and the reference data. Furthermore, it is possible to set a priority to each position reference, and prioritize alignment of a more important portion. Consequently, it is possible to control an alignment scheme of the reference data and the point group data. According to the present embodiment, when an error amount of each reference part is great, the welded parts of the lock bracket gripped by the robot arm 20 and the hinge bracket gripped by the robot arm 30 with respect to the door frame 11 are likely to interfere with each other, so that it is possible to perform positioning prioritizing fitting of shapes of the welded parts by setting a high priority to the welded parts compared to other reference parts.
Furthermore, in the present embodiment, reference data (e.g., CAD data) that serves as criteria for design of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30 is arranged (prepared) in advance. This reference data can include an origin (such as a vehicle origin and, in this case, origin of vehicle=origin of position information generation device), and can be data of an aligned state of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30. Furthermore, in the present embodiment, a control section described later is used to calculate shape fitting point group data obtained by aligning point group data with reference data including the origin (vehicle origin). Furthermore, a movement amount of movement of the point group data to the reference data, and the origins of the reference data and the shape fitting point group data are expressed by 4×4 matrix data (matrix data) (details will described later).
The origin coordinates of the shape fitting point group data are the same as coordinates obtained by moving the origin of the point group data obtained at an origin of the position information generation device. Performing inverse matrix transformation on the 4×4 matrix data (matrix) for matching the point group data with this reference data is the same as matching the reference data with the point group data, and therefore gives the origin to the point group data (a state of the shape fitting point group data expressed as an origin of the reference data is expressed in a form of a position reference of point group data). This scheme realizes giving CAD origin information to point group data without an origin.
A result of movement for matching the point group data of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30 with CAD data (reference data) can be expressed by (that is, is equivalent to) a matrix that indicates that the origin has been moved. The matrix is transformed into an inverse matrix to calculate a movement amount for matching the CAD data (reference data) with the point group data. Matching the point group data with the CAD data (reference data) corresponds to a square matrix, and matching the CAD data (reference data) with the point group data corresponds to the inverse matrix, (which corresponds to returning to the origin when seen from the square matrix). That is, when seen from the origin, a state where the CAD data (reference data) and the point group data are matched is moved to match the CAD coordinates with the point group data. In a case where actual workpiece arrangement of part of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30 can be reproduced at positions as indicated in the CAD coordinate system, the positions of part of the door frame 11, the lock bracket, and the hinge bracket are known, so that it is possible to calculate a movement amount between the origins only by calculating a matrix of other part of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30 (in this case, inverse matrix transformation is unnecessary).
By monitoring (continuing tracking) positions of the position correction markers 22 and 32 at all times, the first position information generation device (laser tracker) 70 assists alignment (micro driving) of the lock bracket gripped by the robot arm 20 and the hinge bracket gripped by the robot arm 30. The robot arms 20 and 30 are calibrated in advance by the first position information generation device (laser tracker) 70 and the position correction marker 22, and have improved absolute accuracy in the spatial coordinates.
When the position correction markers 22 and 32 attached to the robot arms 20 and 30 are measured, the first position information generation device (laser tracker) 70 can monitor three-dimensional coordinates at all times by replacing the vehicle origins of the lock bracket gripped by the robot arm 20 and the hinge bracket gripped by the robot arm 30 with markers. Furthermore, an operation is performed according to a difference between a marker target position and a current position, and final positions are corrected to forcibly improve spatial coordinate accuracy of the robot.
The control section 90 includes a point group data obtaining section 91, a reference data obtaining section 92, a translation matrix operation section 93, an inverse matrix operation section 94, a target translation matrix operation section 95, and a robot arm control section 96.
The point group data obtaining section 91 obtains (receives an input of) point group data (three-dimensional information) of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30 using the first position information generation device (laser tracker) 70 and the second position information generation device (3D scanner) 61. This point group data may be point group data that uses the first position information generation device (laser tracker) 70 as an origin (virtual origin).
The reference data obtaining section 92 obtains (stores) reference data (e.g., CAD data) that serves as criteria for design of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30. This reference data can include an origin (such as a vehicle origin and, in this case, origin of vehicle=origin of position information generation device), and can be data of an aligned state of the doorframe 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30.
The translation matrix operation section 93 performs an operation on a translation matrix for aligning the point group data with the reference data of the aligned state of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30. The shape fitting point group data obtained by aligning the point group data with the reference data based on the translation matrix can be obtained by this translation matrix operation.
The inverse matrix operation section 94 performs inverse matrix transformation on 4×4 matrix data (matrix) that is calculated by the translation matrix operation section 93 and is used to match the point group data with the reference data. This transformation gives the origin to the above-described point group data (a state of the shape fitting point group data expressed as an origin of reference data is expressed in a form of a position reference of point group data). This scheme realizes giving CAD origin information to point group data without an origin.
For each of the door frame 11 supported by the fixing jig 10, the lock bracket gripped by the robot arm 20, and the hinge bracket gripped by the robot arm 30, the target translation matrix operation section 95 can calculate a movement amount from the origin of one of the lock bracket and the hinge bracket to the other origin thereof by using the inverse matrix from a state where the origin (vehicle origin) is given.
The robot arm control section 96 positions the lock bracket and the hinge bracket at the door frame 11 by moving the lock bracket by the robot arm 20 and moving the hinge bracket by the robot arm 30 based on at least one of the translation matrix and the inverse matrix. More specifically, the robot arm control section 96 causes, for example, each axis (six axes) of the robot arms 20 and 30 to make a micromotion until the positioning target lock bracket and hinge bracket arrive at target positions from initial positions or current positions based on at least one of the translation matrix and the inverse matrix. An instruction value of a micromotion amount at this time is a difference between current positions and target positions of the position correction markers 22 and 32 seen from the first position information generation device (laser tracker) 70. By setting a numerical value of this micromotion amount by coefficient adjustment or the number of times of micromotions, it is possible to perform positioning that does not depend on accuracy of the robot. That is, according to the present embodiment, at two stages of (1) movement of a workpiece (grip part) based on at least one of the translation matrix and the inverse matrix (e.g., movement of one of the origins added to the lock bracket and the hinge bracket to the other one origin with one of these origins serving as a position reference based on the inverse matrix), and (2) movement of the lock bracket and the hinge bracket based on the position correction markers 22 and 32 (correction positioning using the position correction markers 22 and 32 or correction of an operation error in (1)), positioning of the workpieces (the lock bracket and the hinge bracket) is executed. In a state where the robot arm control section 96 positions the lock bracket and the hinge bracket, the welded parts of both of the lock bracket and the hinge bracket are welded by the welding robots 40 and 50.
The function of the control section 90 can be also expressed as follows. That is, the control section 90 obtains three-dimensional data (e.g., point group data), and obtains relative position data (e.g., reference data) of a hand and workpieces. The control section 90 executes spatial positioning processing for fitting best the obtained three-dimensional data (e.g., point group data) and the relative position data (e.g., reference data). The control section 90 outputs a movement amount coordinate value of the workpieces by the hand. The control section 90 executes motion (movement) control of the hand and the workpieces by calculation of the six axes based on robot inverse kinetics.
The positioning processing according to the present embodiment is executed by, for example, following steps. First, the point group data of the lock bracket and the hinge bracket is aligned with the CAD data (reference data), and movement amounts of the lock bracket and the hinge bracket are output based on translation matrices that are 4×4 matrix data (matrix data). By this means, shape fitting point group data obtained by aligning the point group data with the reference data based on the translation matrix is obtained for the lock bracket and the hinge bracket. Furthermore, the point group data of the door frame 11 is aligned with the CAD data (reference data), and a movement amount of the door frame 11 is output based on a translation matrix that is the 4×4 matrix data (matrix data). By this means, shape fitting point group data obtained by aligning the point group data with the reference data based on the translation matrix is obtained for the door frame 11. Furthermore, an inverse matrix operation is executed based on the calculated translation matrices to give the origin to the point group data. That is, the one origin serves as the position reference to match the other origin the one origin. Alternatively, the shape fitting point group data may be moved to move the origin (vehicle origin) of the reference data together, and match the moved origins of the lock bracket, the hinge bracket, and the door frame 11. Furthermore, the calculated inverse matrices are used to give coordinate values (e.g., CAD coordinates) to the point group data of the lock bracket, the hinge bracket, and the door frame 11. Furthermore, a movement amount of the point group data is calculated in a coordinate system whose origin (vehicle origin) is a position reference, and the robot arms 20 and 30 that grip the lock bracket and the hinge bracket are moved based on the calculated movement amounts to position the lock bracket and the hinge bracket at the door frame 11. According to the present embodiment, the door frame 11 is fixed, and the lock bracket and the hinge bracket are movable, and therefore the movement amounts correspond to movement amounts of the lock bracket and the hinge bracket with respect to the door frame 11 (movement amounts from the CAD coordinates of the lock bracket and the hinge bracket to the CAD coordinates of the door frame 11). Lastly, the lock bracket and the hinge bracket are moved with respect to the door frame 11 based on the calculated movement amounts of the lock bracket and the hinge bracket with respect to the door frame 11 to position the lock bracket and the hinge bracket with respect to the door frame 11.
A process of aligning point group data with reference data according to the present embodiment includes, for example, a forced numerical value movement step of performing forced numerical value (quantitative value) movement on point group information, a best fit step for entire shape fitting of aligning an entire point group and an entire CAD shape, and a reference alignment step of performing detailed alignment with a reference portion such as a portion that serves as criteria for product evaluation.
By the way, at, for example, a time of initial setting (a time of calibration) of the welding device 1, the first position information generation device (laser tracker) 70 measures a position and a posture of the position correction marker 62 of the second position information generation device (3D scanner) 61 every time. Furthermore, as described above, the 3D scanner 61 is supported at a distal end side of the 3D scanner support arm 60, and point group data obtained by the second position information generation device (3D scanner) 61 is replaced with origin data of the first position information generation device (laser tracker) 70.
However, it is concerned that, when temperatures of the second position information generation device (3D scanner) 61 and a surrounding metal thereof increase (e.g., 20° C.) at a time of operation, thereby causing thermal expansion, position accuracy of the 3D scanner 61 varies, and, as a result, an initial origin of the 3D scanner 61 and the origin of the 3D scanner 61 after the temperature rise are misaligned, and alignment accuracy of targets (e.g., the lock bracket, the hinge bracket, and the door frame 11) deteriorates. Thus, continuing 3D scanning a workpiece arranged at the same place for a long time (transforming obtained point group information into a laser tracker origin) causes a problem that a position and a posture of the obtained point group data vary as a time passes (temperature rise process).
Hence, the present embodiment has focused on that, when a distance from the first position information generation device (laser tracker) 70 to the shape marker 80 can be calculated, it is possible to calculate a dimension from the second position information generation device (3D scanner) 61 to the position correction marker 62, and add a function of measuring again the dimension between the 3D scanner 61 and the position correction marker 62 before actually measuring a workpiece, and calibrating positions of both of the 3D scanner 61 and the position correction marker 62. By calibrating on a regular basis the origin position of the 3D scanner 61 that changes in response to an environmental situation such as a temperature, and calibrating the origin position, for example, once per cycle, it is possible to continue maintaining accurate detection of a position and a posture at all times according to the environmental situation such as the temperature.
The shapes of the shape marker 80 illustrated in
Note that the shape marker 80 may be provided at distal end sides of the robot arms 20 and 30 that grip workpieces (e.g., the lock bracket and the hinge bracket). In this case, the shape marker 80 may be provided instead of/in addition to the position correction markers 22 and 32 of the robot arms 20 and 30.
A processing step for calculating and/or calibrating the above quantitative value can include a following first step to fourth step. (1) A first step (D) of, at the first position information generation device (laser tracker) 70, measuring at least one of the second position information generation device (3D scanner) 61 and the position correction marker 62. (2) A second step (A) of, at the first position information generation device (laser tracker) 70, measuring the shape marker 80 that is a fourth target. (3) A third step (B) of, at the second position information generation device (3D scanner) 61, measuring the shape marker 80 that is the fourth target. (4) A fourth step (C) of calculating and/or calibrating the quantitative value that is an origin position and a posture of the second position information generation device (3D scanner) 61 with the position correction marker 62 serving as the position reference based on measurement results in the first step (D), the second step (A), and the third step (B).
Note that, although the above description exemplifies the case where the shape marker 80 is used both as the second target and the fourth target, a shape marker different from the shape marker 80 located at the position correction reference base may be provided, and these shape marker and shape marker 80 may be used as the second and fourth targets. Furthermore, there may be added a step of providing the fifth target (marker) for securing a position and a posture of the fourth target, that is, the position correction marker 42 as a misalignment calibration shape marker of the second position information generation device (3D scanner) 61, and measuring the fifth target. The position correction marker 62 that is the first target is likely to be misaligned due to a temperature, and therefore measurement may be performed at a time of calibration by interposing the fifth target (marker) whose position is measured first in advance to secure accuracy, and to calculate and/or calibrate the quantitative value that is the origin position and the posture of the second position information generation device (3D scanner) 61 with the position correction marker 62 serving as the position reference.
Alternatively, the quantitative value that is the position and the posture of the second position information generation device (3D scanner) 61 with the position correction marker 62 serving as the position reference may be held in a table as a value that is determined in advance and differs depending on a temperature of the second position information generation device (3D scanner) 61. Furthermore, the quantitative value that is the position and the posture of the second position information generation device (3D scanner) 61 with the position correction marker 62 serving as the position reference may be calculated and/or calibrated based on temperature measurement of the second position information generation device (3D scanner) 61 referring to this table. For example, the quantitative value (calibrated value) matching a measured temperature may be calculated referring to the table that holds the quantitative value (calibrated value) per predetermined temperature range, or the quantitative value (calibrated value) may be calculated by substituting the measured temperature for a calculation formula that uses a temperature as an input parameter.
The above-described quantitative value calibration processing is executed at, for example, a predetermined timing at which a change in environment such as a temperature is concerned (e.g., the calibration processing is executed before 3D scan measurement per cycle). Consequently, it is possible to calibrate a position and a posture between a 3D scanner and a marker, and absorb variations due to an influence of environment (temperature).
As described above, the target detection method according to the present embodiment includes: a step of calculating a quantitative value; a step of, at a first position information generation device, measuring a first target; a step of, at a second position information generation device, measuring a second target; a step of calculating a position of the second target using the first position information generation device as a position reference based on a measurement value of the first target obtained by the first position information generation device, a measurement value of the second target obtained by the second position information generation device, and the quantitative value; and a step of calibrating the quantitative value before measuring a third target using the second position information generation device. Consequently, it is possible to maintain detection accuracy of a target irrespectively of a change (such as a temperature) in external environment. It is possible to calibrate a position and a posture between a 3D scanner and a marker, and absorb variations due to an influence of environment (temperature).
This application claims priority to Japanese Patent Application No. 2022-048768 filed on Mar. 24, 2022, the entire contents of which are incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-048768 | Mar 2022 | JP | national |
