Robot control device

Abstract

To provide a robot control device that allows reduction in tact time while keeping cost low.SOLUTION: A robot control device includes: a point cloud data detection unit for detecting coordinate data corresponding to a workpiece W on which a manipulator 2 works as workpiece point cloud data from three-dimensional image data containing the workpiece W; an error calculation unit for calculating an error by comparing the detected workpiece point cloud data with a prestored reference point cloud data serving as a reference; and a sensor control unit for starting sensing by a laser sensor 3 from a sensing start position corresponding to the calculated error in a direction of approaching the workpiece W.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a robot control device. [Background technology]

[0002] When performing work using an industrial robot, the position of the object is measured and corrected to the correct position in order to prevent misalignment caused by an error in the placement of the object or an error in the robot's processing. Methods for measuring the position of an object include, for example, a method using a 2D camera and a laser sensor, and a method using a 3D camera. Patent Document 1 listed below discloses a method for measuring the position and orientation of an object using a 2D CCD camera and a laser sensor, and Patent Document 2 listed below discloses a method for measuring the position of an object using 3D data measured by a 3D measuring device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3556589 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-222568 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the method using a 2D camera and laser sensor has the problem that the 2D camera cannot accurately measure the distance to the target, and the laser sensor has a narrow range of detection. The method using a 3D camera has the problem that 3D cameras with high detection accuracy are expensive, resulting in high costs. To avoid these problems, when using a 2D camera and laser sensor, it is possible to sense the target by feel from a distance so that the laser sensor does not interfere with the target, but this increases the takt time. Furthermore, when using a 3D camera, it is possible to use an inexpensive three-dimensional camera to reduce costs, but this reduces detection accuracy and increases the possibility that the laser sensor will interfere with the target.

[0005] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a robot control device that can reduce takt time while suppressing costs. [Means for solving the problem]

[0006] A robot control device according to one aspect of the present invention includes a point cloud data detection unit that detects three-dimensional coordinate data corresponding to an object as object point cloud data from three-dimensional image data including the object on which an industrial robot is working, an error calculation unit that calculates an error by comparing the detected object point cloud data with pre-stored reference point cloud data, and a sensor control unit that causes a sensor to start sensing in a direction approaching the object from a sensing start position corresponding to the calculated error.

[0007] According to this aspect, three-dimensional object point cloud data corresponding to an object detected from three-dimensional image data including the object is compared with reference point cloud data to calculate an error representing a deviation from a reference position, and the sensor can start sensing from a sensing start position corresponding to the error. As a result, even if the object is deviated from the reference position by an error, the sensor's sensing start position can be shifted to match the error, thereby improving the efficiency of the sensing operation. Furthermore, since it is sufficient to capture three-dimensional image data, there is no need to use an expensive 3D camera.

[0008] In the above aspect, the error calculation section may calculate the error based on the distance between the object point cloud data and the reference point cloud data.

[0009] According to this aspect, it is possible to control the start position of the sensor by using the distance by which the object point cloud data is separated from the reference point cloud data as an error.

[0010] In the above aspect, the error calculation unit may calculate the distance between each point included in the object point cloud data and the approximate plane corresponding to the reference point cloud data, and calculate the average value of the calculated distances as the error.

[0011] According to this aspect, it is possible to reduce the amount of calculation required to calculate the error.

[0012] In the above aspect, the error calculation unit may calculate the distance between points that are in a corresponding positional relationship in the object point cloud data and the reference point cloud data, and calculate the average value of the calculated distances as the error.

[0013] According to this aspect, it is possible to improve the accuracy of calculating the error.

[0014] In the above aspect, the sensing start position may be set based on the criterion that the industrial robot including the sensor does not interfere with the object even if the sensor moves a distance corresponding to the error from the sensing start position toward the object.

[0015] According to this aspect, even if the object is shifted from the reference position by an error, the sensing start position can be shifted to match that error, so that even if the sensor moves a distance corresponding to the error, it can move without interfering with the object. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a robot control device that can reduce takt time while suppressing costs. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating a configuration example of a robot system including a robot control device according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a functional configuration of a robot control device. [Figure 3] FIG. 2 is a schematic diagram for explaining the field of view of a laser sensor. [Figure 4] 10A and 10B are diagrams for explaining an example of a correspondence relationship between an error and a sensing start position. [Figure 5] FIG. 10 is a schematic diagram for explaining a sensing start position that is set based on an error. [Figure 6] FIG. 10 is a schematic diagram for explaining a sensing start position that is set based on an error. [Figure 7] FIG. 10 is a schematic diagram for explaining a sensing start position that is set based on an error. DETAILED DESCRIPTION OF THE INVENTION

[0018] A preferred embodiment of the present invention will be described with reference to the accompanying drawings. In each drawing, components with the same reference numerals have the same or similar configurations. Furthermore, since the drawings are schematic, the dimensions and proportions of each component may differ from those of the actual components.

[0019] FIG. 1 is a diagram illustrating the configuration of a robot system 100 including a robot control device 1 according to an embodiment. The robot system 100 includes, for example, the robot control device 1, a manipulator 2, a laser sensor 3, and an imaging terminal 4. Each device can be connected via a network, for example, including a wired or wireless network such as a communication cable. The robot system 100 may also include a teaching pendant. The teaching pendant is an operation terminal through which an operator teaches the manipulator 2 how to operate.

[0020] The manipulator 2 is a welding robot that performs arc welding in accordance with working conditions set in the robot control device 1. The manipulator 2 has, for example, an articulated arm 21 provided on a base member fixed to the floor of a factory or the like, and a welding torch 22 connected to the tip of the articulated arm 21.

[0021] The robot control device 1 is a control unit that controls the operation of the manipulator 2, and includes, for example, a control unit 11, a storage unit 12, a communication unit 13, and a welding power supply unit .

[0022] The control unit 11 controls the manipulator 2 and the welding power supply unit 14, for example, by causing a processor to execute an operation program stored in the storage unit 12. The communication unit 13 controls communication with each device connected via a network.

[0023] Welding power supply 14 supplies welding current, welding voltage, and the like to manipulator 2 in accordance with predetermined welding conditions, for example, to generate an arc between the tip of the welding wire and workpiece (object) W. The welding conditions include data items such as welding conditions, welding start position, welding end position, welding distance, welding torch posture, and the like. The welding conditions include data items such as welding current, welding voltage, welding speed, wire feed speed, and workpiece thickness. Welding power supply 14 may be provided separately from robot control device 1.

[0024] The laser sensor 3 is attached to the tip of the articulated arm 21 of the manipulator 2, and measures the distance to the workpiece W. The laser sensor 3 is, for example, a scanning laser sensor, and includes a light-emitting unit that emits a laser toward the workpiece W, and a light-receiving unit that receives the laser reflected by the workpiece W. The laser emitted by the light-emitting unit is diffusely reflected by the workpiece W and received by the light-receiving unit. The light-receiving unit is, for example, configured by a CCD sensor, and measures the distance from the laser sensor 3 to the workpiece W within its field of view.

[0025] The sensor control unit 31 is a controller that controls the laser sensor 3 and transmits information including the measurement values ​​of the laser sensor 3 to the robot control device 1. The sensor control unit 31 calculates groove information including the cross-sectional shape of the workpiece W, for example, based on distance measurement data (distance information) measured in the process of determining the target position (target coordinates) of the welding torch 22. The sensor control unit 31 transmits the target position and groove information to the robot control device 1. The functions of the sensor control unit 31 may be included in the functions of the control unit 11 of the robot control device 1.

[0026] The photographing terminal 4 is, for example, a 3D camera with a 3D laser scanner function, but may also be a portable terminal with a 3D camera. Portable terminals include, for example, tablet terminals, smartphones, personal digital assistants (PDAs), notebook PCs (personal computers), and other portable terminals. The photographing terminal 4 is preferably fixed in a predetermined position, orientation, and posture to fix its positional relationship with the workpiece W to be photographed.

[0027] To realize a 3D laser scanner function, for example, a LiDAR (Light Detection and Ranging) sensor, a millimeter wave sensor, an ultrasonic sensor, etc. can be equipped.

[0028] The photographing terminal control unit 41 is a controller that controls the photographing terminal 4 and transmits information including image data photographed by the photographing terminal 4 to the robot control device 1. The photographing terminal control unit 41 transmits, for example, three-dimensional image data including the workpiece W photographed by the photographing terminal 4 to the robot control device 1. Note that the function of the photographing terminal control unit 41 may be included in the function of the control unit 11 of the robot control device 1.

[0029] 2 is a diagram illustrating an example of the functional configuration of a robot control device 1 according to the present invention. The functional configuration of the robot control device 1 includes, for example, a point cloud data detection unit 111, an error calculation unit 112, and a sensor control unit 113.

[0030] The point cloud data detection unit 111 detects point cloud data corresponding to the workpiece W from three-dimensional image data including the workpiece W photographed by the photographing terminal 4. Specifically, the point cloud data detection unit 111 detects three-dimensional coordinate data corresponding to the workpiece W included in the image data based on the three-dimensional camera coordinate system, and sets this coordinate data as workpiece point cloud data. The three-dimensional camera coordinate system can be set, for example, with the center of the lens of the photographing terminal 4 as the origin.

[0031] The error calculation unit 112 compares the work point cloud data detected by the point cloud data detection unit 111 with the reference point cloud data to calculate an error. The reference point cloud data is point cloud data corresponding to a reference work W arranged with a reference position, orientation, and posture. It is preferable that the reference point cloud data is detected in advance using the reference work W and stored in the storage unit 12. One example of a method for calculating the error is described below in (a) and (b).

[0032] (a) An approximate plane is created based on the reference point cloud data, and the distance between the approximate plane and each point included in the work point cloud data is calculated. The average of these calculated distances is calculated as the error. The distance between the approximate plane and each point in the work point cloud data can be found as the length of the perpendicular line from each point to the approximate plane, and can be calculated using the equation for the approximate plane and the coordinates of each point in the work point cloud data. This method can reduce the amount of calculation required to calculate the error compared to method (b) below.

[0033] (b) Calculate the distance between points that are in a corresponding positional relationship in the work point cloud data and the reference point cloud data, and calculate the average value of the calculated distances as the error. This method requires more calculations than the above method (a), but can improve the accuracy of error calculation.

[0034] When calculating the average distance values ​​in (a) and (b) above, it is preferable to use the absolute distance values, which makes it possible to cancel out any variations in the points of the point cloud data, thereby improving the accuracy of error calculation.

[0035] The method for calculating the error is not limited to the above methods (a) and (b). For example, the maximum distance among the distances within the reference range may be extracted as the error.

[0036] When the sensor control unit 113 causes the laser sensor 3 to start sensing the workpiece W, it starts from a sensing start position corresponding to the error calculated by the error calculation unit 112.

[0037] The sensing start position is preferably set based on the criterion that even if the laser sensor 3 moves a distance corresponding to the error from the start position toward the workpiece W, the manipulator 2 including the laser sensor 3 will not interfere with (contact with) the workpiece W. This allows the sensing start position to be shifted to match the error even if the workpiece W deviates from the reference position by the amount of the error, so that even if the laser sensor 3 moves a distance corresponding to the error, it becomes possible for the laser sensor 3 to move without interfering with the workpiece W.

[0038] The correspondence between the error and the sensing start position is set according to the field of view of the laser sensor 3. For example, as shown in Fig. 3, a case will be described where the field of view V of the laser sensor 3 is 40 to 60 mm. In this case, when the distance between the laser sensor 3 and the workpiece W is within the field of view V, which is 40 to 60 mm, the laser sensor 3 can detect the workpiece W.

[0039] 4, the correspondence relationship between the settable error and the sensing start position when the field of view range V of the laser sensor 3 is 40 to 60 [mm] will be described. As shown in the figure, for example, (1) when the error calculated by the error calculation unit 112 is 0 to 5 [mm], the sensing start position can be set to a position 50 [mm] away from the workpiece W, (2) when the error is 5 to 10 [mm], the sensing start position can be set to a position 60 [mm] away from the workpiece W, and (3) when the error is 10 to 20 [mm], the sensing start position can be set to a position 70 [mm] away from the workpiece W. (1) to (3) will be described with reference to FIGS. 5 to 7.

[0040] (1) When the error calculated by the error calculation unit 112 is 0 to 5 [mm] As shown in FIG. 5, the sensing start position S of the laser sensor 3 is set to a position 50 mm away from the workpiece W. In this case, even if there is a deviation of 5 mm, which is the maximum error, from the set sensing start position S of 50 mm, the actual sensing start position will be 45 to 55 mm away from the workpiece W. Therefore, if sensing is started from the sensing start position S set to 50 mm, even if there is a deviation of 5 mm, which is the maximum error, it is possible to detect the workpiece W within the range of 40 to 60 mm, which is the field of view V of the laser sensor 3. This makes it possible to prevent the manipulator 2 including the laser sensor 3 from interfering with the workpiece W due to not being able to detect the workpiece W.

[0041] (2) When the error calculated by the error calculation unit 112 is 5 to 10 [mm] As shown in Figure 6, the sensing start position of the laser sensor 3 is set to a position 60 [mm] away from the workpiece W. In this case, even if there is a deviation of 10 [mm], which is the maximum error, from the set sensing start position S of 60 [mm], the actual sensing start position will be at a position 50 to 70 [mm] away from the workpiece W. Therefore, by starting sensing from the sensing start position S set to 60 [mm] and repeating sensing while moving in a direction approaching the workpiece W, it is possible to detect the workpiece W within the range of 40 to 60 [mm], which is the field of view range V of the laser sensor 3.

[0042] (3) When the error calculated by the error calculation unit 112 is 10 to 20 [mm] As shown in FIG. 7, the sensing start position is set to a position 70 mm away from the workpiece W. In this case, even if there is a maximum error of 20 mm from the sensing start position S set to 70 mm, the actual sensing start position will be 50 to 90 mm away from the workpiece W. Therefore, by starting sensing from the sensing start position S set to 70 mm and repeating sensing while moving in a direction approaching the workpiece W, it becomes possible to detect the workpiece W within the field of view V of the laser sensor 3, which is 40 to 60 mm.

[0043] Even if the error calculated by the error calculation unit 112 is in a range exceeding 20 [mm], similar to the above (1) to (3), even if a deviation of the maximum error occurs, the sensing start position S may be set so that the minimum value of the actual sensing start position falls within the field of view range V. This makes it possible to prevent the manipulator 2 including the laser sensor 3 from interfering with the workpiece W due to being unable to detect the workpiece W.

[0044] Returning to the explanation of Fig. 2, the sensor control unit 113 senses while moving the laser sensor 3 in a direction approaching the workpiece W, and when the workpiece W is detected, stops the movement of the laser sensor 3. This allows the laser sensor 3 to be stopped when the sensing purpose is achieved, making it possible to reliably avoid interference with the workpiece W.

[0045] When the laser sensor 3 has moved a predetermined distance from the sensing start position toward the workpiece W, the sensor control unit 113 stops the movement of the laser sensor 3 and outputs an error message indicating that the workpiece W could not be detected. The error message may be output to, for example, a display device such as a display, or a loudspeaker device such as a speaker.

[0046] The predetermined distance is preferably set, for example, taking into consideration the error, the sensing start position S, and the field of view range V, so that the laser sensor 3 can move within the field of view range V and the manipulator 2 including the laser sensor 3 will not interfere with the workpiece W. This makes it possible to stop the laser sensor 3 when it has moved the predetermined distance, even if a situation arises in which sensing cannot be performed normally, thereby reliably avoiding interference with the workpiece W.

[0047] As described above, the robot control device 1 according to the embodiment compares the three-dimensional workpiece point cloud data corresponding to the workpiece W detected from the three-dimensional image data including the workpiece W with the reference point cloud data to calculate an error representing a deviation from a reference position, and causes the laser sensor 3 to start sensing from a sensing start position S corresponding to the error. As a result, even if the workpiece W deviates from the reference position by an amount corresponding to the error, the sensing start position S of the laser sensor 3 can be shifted to match the error, thereby improving the efficiency of the sensing operation. Furthermore, the photographing terminal 4 need only be a camera capable of photographing three-dimensional image data, so there is no need to use an expensive 3D camera.

[0048] Therefore, the robot control device 1 according to the embodiment makes it possible to reduce the takt time while suppressing costs.

[0049] [Variations] It should be noted that the present invention is not limited to the above-described embodiment, and can be embodied in various other forms without departing from the spirit of the present invention. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted as being limiting.

[0050] For example, in the above-described embodiment, the photographing terminal 4 is fixedly disposed at a predetermined position, orientation, and posture, but the worker may hold the photographing terminal 4 and photograph the workpiece W from any position. In this case, it is preferable to store reference point cloud data in advance in association with the photographing position.

[0051] In the above-described embodiment, the present invention is described as being applied to a welding robot, but is not limited to this. For example, the present invention can be applied to industrial robots including handling robots that perform picking and other operations.

[0052] Furthermore, although the above-described embodiment has been described using a laser sensor, the present invention can also be applied to sensors other than laser sensors. For example, a touch sensor may be used. Even when a touch sensor is used, the sensing start position of the touch sensor can be changed depending on the error. [Explanation of symbols]

[0053] 1...robot control device, 2...manipulator, 3...laser sensor, 4...photographing terminal, 11...control unit, 12...storage unit, 13...communication unit, 14...welding power supply unit, 21...articulated arm, 22...welding torch, 31...sensor control unit, 41...photographing terminal control unit, 100...robot system, 111...point cloud data detection unit, 112...error calculation unit, 113...sensor control unit, S...sensing start position, V...field of view range, W...work

Claims

1. a point cloud data detection unit that detects, from three-dimensional image data including an object on which an industrial robot works, three-dimensional coordinate data corresponding to the object as object point cloud data; an error calculation unit that calculates an error by comparing the detected object point cloud data with pre-stored reference point cloud data that serves as a reference; a sensor control unit that causes the sensor to start sensing in a direction approaching the object from a sensing start position corresponding to the calculated error; Equipped with the sensing start position is set so that the distance between the sensing start position and the object falls within the field of view of the sensor even when the sensor is deviated by the maximum value of the error in a direction in which the sensor approaches the object. Robot control device.

2. the error calculation unit calculates the error based on a distance between the object point cloud data and the reference point cloud data. The robot control device according to claim 1.

3. the error calculation unit calculates a distance between each point included in the object point cloud data and an approximation plane corresponding to the reference point cloud data, and calculates an average value of the calculated distances as the error. The robot control device according to claim 2.

4. the error calculation unit calculates distances between points in the object point cloud data and the reference point cloud data that are in a corresponding positional relationship, and calculates an average value of the calculated distances as the error. The robot control device according to claim 2.

5. the sensing start position is set based on the criterion that the industrial robot including the sensor does not interfere with the object even when the sensor moves from the sensing start position toward the object by a distance corresponding to the error. The robot control device according to any one of claims 1 to 4.

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