Correction method, correction system and storage medium for correcting conveyor tracking information

Abstract

The present invention relates to a correction method, correction system, and storage medium for correcting conveyor tracking information, which can accurately set conveyor tracking information without stopping the conveyor. The correction method of the present invention includes the following steps: (a) temporarily setting conveyor tracking information; (b) capturing a reference object carried on the conveyor at three imaging timings while the conveyor is moving at a fixed speed, thereby acquiring a reference image, a first image, and a second image; (c) analyzing the three images to determine the measured coordinate values of the reference position, the first position, and the second position in the robot coordinate system; and (d) correcting the temporarily set value of the conveyor tracking information so that the position and movement of the conveyor represented by the conveyor tracking information match various measurement results.

Description

Technical Field

[0001] The invention relates to a correction method, a correction system and a storage medium for correcting conveyor tracking information. Background Art

[0002] Patent Document 1 discloses a conveyor tracking system for a robot. In this system, the robot touches a mobile device carried on the conveyor while the conveyor is stopped at a plurality of predetermined positions. The conveyor tracking system is calibrated using the touch positions and an image of the mobile device.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-141935

[0004] However, in the above-mentioned conventional technology, since the conveyor needs to be stopped when the robot touches the moving device, there is a problem in that the productivity of the robot system is reduced. Summary of the Invention

[0005] According to a first aspect of the present invention, a correction method is provided, which is a correction method for correcting conveyor tracking information in a robot system, the robot system comprising: a conveyor; a robot that operates on a workpiece conveyed by the conveyor; an encoder that detects the movement of the conveyor; and a camera that photographs the workpiece to measure the position of the workpiece carried on the conveyor, the conveyor tracking information being information representing the position and movement of the conveyor in the robot coordinate system. The correction method includes the following steps: (a) temporarily setting the conveyor tracking information; (b) when the conveyor moves at a fixed speed, by photographing the reference object carried on the conveyor at the reference shooting timing, the first shooting timing and the second shooting timing respectively, obtaining a reference image, a first image and a second image, and obtaining the measurement values of the encoder at the reference shooting timing, the first shooting timing and the second shooting timing as the reference encoder value, the first encoder value and the second encoder value; (c) by analyzing the reference image, the first image and the second image, respectively obtaining the representative position of the reference object as the reference position, the first position and the second position, and respectively obtaining the measurement coordinate values of the reference position, the first position and the second position in the robot coordinate system; and (d) using the measurement coordinate values including the reference position, the first position and the second position and the measurement results of the reference encoder value, the first encoder value and the second encoder value, correcting the temporary setting value of the conveyor tracking information so that the position and movement of the conveyor represented by the conveyor tracking information match the measurement results.

[0006] According to a second aspect of the present invention, a calibration system for calibrating conveyor tracking information is provided. The calibration system comprises: a conveyor; a robot that operates on a workpiece conveyed by the conveyor; an encoder that detects the movement of the conveyor; a camera that images the workpiece to measure the position of the workpiece carried on the conveyor; and a calibration execution unit that calibrates the conveyor tracking information indicating the position and movement of the conveyor in the robot coordinate system. The correction execution unit performs the following processing: (a) temporarily setting the conveyor tracking information; (b) when the conveyor moves at a fixed speed, by photographing the reference object carried on the conveyor at the reference shooting timing, the first shooting timing and the second shooting timing respectively, obtaining a reference image, a first image and a second image, and obtaining the measurement values of the encoder at the reference shooting timing, the first shooting timing and the second shooting timing as the reference encoder value, the first encoder value and the second encoder value; (c) by analyzing the reference image, the first image and the second image, respectively obtaining the representative position of the reference object as the reference position, the first position and the second position, and respectively obtaining the measurement coordinate values of the reference position, the first position and the second position in the robot coordinate system; and (d) using the measurement coordinate values including the reference position, the first position and the second position and the measurement results of the reference encoder value, the first encoder value and the second encoder value, correcting the temporary setting value of the conveyor tracking information so that the position and movement of the conveyor represented by the conveyor tracking information match the measurement results.

[0007] According to a third embodiment of the present invention, a storage medium is provided, which stores a computer program. In a robot system, the computer program causes a processor to execute processing to correct conveyor tracking information. The robot system comprises: a conveyor; a robot that operates on a workpiece conveyed by the conveyor; an encoder that detects the movement of the conveyor; and a camera that photographs the workpiece to measure the position of the workpiece carried on the conveyor, wherein the conveyor tracking information is information representing the position and movement of the conveyor in the robot coordinate system. The computer program causes the processor to perform the following processing: (a) temporarily setting the conveyor tracking information; (b) when the conveyor moves at a fixed speed, by photographing the reference object carried on the conveyor at the reference shooting timing, the first shooting timing and the second shooting timing, respectively, obtaining a reference image, a first image and a second image, and obtaining the measurement values of the encoder at the reference shooting timing, the first shooting timing and the second shooting timing as the reference encoder value, the first encoder value and the second encoder value; (c) by analyzing the reference image, the first image and the second image, respectively obtaining the representative position of the reference object as the reference position, the first position and the second position, and respectively obtaining the measurement coordinate values of the reference position, the first position and the second position in the robot coordinate system; and (d) using the measurement coordinate values including the reference position, the first position and the second position and the measurement results of the reference encoder value, the first encoder value and the second encoder value, correcting the temporary setting value of the conveyor tracking information so that the position and movement of the conveyor represented by the conveyor tracking information match the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is an explanatory diagram showing the configuration of a robot system in the embodiment.

[0009] Figure 2 This is a functional block diagram of the control device.

[0010] Figure 3 1 is a flowchart showing the correction process steps of conveyor tracking information.

[0011] Figure 4 It is an explanatory diagram showing an example of setting values of conveyor tracking information.

[0012] Figure 5 1 and 2 are explanatory diagrams showing various measurement values at three imaging timings.

[0013] Figure 6 It is an explanatory diagram showing various measured values and calculated values for obtaining correction values of conveyor tracking information.

[0014] Figure 7 It is an explanatory diagram showing various measurement values after the correction processing of the conveyor tracking information.

[0015] Description of Reference Numerals

[0016] 100…robot, 110…base, 120…robot arm, 122…joint encoder, 130…moving camera, 200…control device, 210…processor, 212…calibration execution unit, 214…image analysis unit, 220…memory, 230…interface circuit, 240…input device, 250…display unit, 300…conveyor, 310…conveyor encoder, 320…conveyor camera. DETAILED DESCRIPTION

[0017] Figure 1 1 is an explanatory diagram showing an example of a robot system according to one embodiment. The robot system includes a robot 100 , a control device 200 for controlling the robot 100 , and a conveyor 300 for conveying a workpiece to be worked on by the robot 100 .

[0018] The robot 100 includes a base 110 and a robotic arm 120. A mobile camera 130 is provided at the front end of the robotic arm 120. The mobile camera 130 may be provided at a location other than the front end of the robotic arm 120. However, in this case, it is preferable that the mobile camera 130 be provided so as to be able to follow objects flowing on the conveyor 300 and capture images thereof. The robot 100 may be any robot having an arm mechanism with multiple joints. Alternatively, an orthogonal robot combining multiple single axes may be used.

[0019] The conveyor 300 moves at a constant speed along the conveying direction AD. A conveyor encoder 310 is installed on the conveyor 300 to detect the movement of the conveyor 300. Furthermore, a conveyor camera 320 is installed above the conveyor 300 to capture images of objects on the conveyor 300. The position of the conveyor camera 320 is fixed. As described later, conveyor tracking information includes information indicating the position and movement of the conveyor 300.

[0020] exist Figure 1 FIG2 shows a state where a reference object RB for setting conveyor tracking information is being conveyed by conveyor 300. Reference object RB is preferably provided with a marker MK for identifying a representative position of reference object RB. The position of marker MK is determined by analyzing an image of reference object RB, and the position of marker MK can be identified as the representative position of reference object RB. However, marker MK may be omitted. Furthermore, a workpiece, which is the work target of robot 100, may be used directly as reference object RB.

[0021] In the conveyor tracking information calibration process described later, while the conveyor 300 is operating at a constant speed, images of the reference object RB are captured at the base capture timing ST0, the first capture timing ST1, and the second capture timing ST2. These three capture timings ST0, ST1, and ST2 are taken at three different positions sequentially along the conveyor 300 from the upstream side to the downstream side. The conveyor camera 320 captures an image of the reference object RB at the base capture timing ST0, while the mobile camera 130 captures images of the reference object RB at the first capture timing ST1 and the second capture timing ST2. Furthermore, measurement values from the conveyor encoder 310 are acquired at these three capture timings ST0, ST1, and ST2.

[0022] The mobile camera coordinate system Σ of the mobile camera 130 MC Relative to the robot coordinate system Σ R More precisely, the camera coordinate system Σ is moved MC The fingertip coordinate system Σ relative to the robot arm 120 T The fingertip coordinate system Σ is calibrated T The coordinate values of can be transformed into the robot coordinate system Σ using the encoder values of the joints of the robot arm 120 R Therefore, the camera coordinate system Σ is moved MC The coordinate value can be accurately transformed into the fingertip coordinate system Σ T Therefore, any position in the image captured by the mobile camera 130 can be accurately transformed into the robot coordinate system Σ R From this description, it can be understood that the mobile camera coordinate system Σ MC Relative to the robot coordinate system Σ R is calibrated indirectly. "With respect to the robot coordinate system Σ R The phrase "is calibrated" also includes the case where the correspondence is indirectly corrected in the above manner. In addition, the robot coordinate system Σ R The fingertip coordinate system Σ is a coordinate system with the predetermined reference position of the robot 100 as the coordinate origin. T This is a coordinate system having a predetermined reference position at the front end of the robot arm 120 as a coordinate origin.

[0023] The first imaging timing ST1 and the second imaging timing ST2 may be captured using a camera other than the mobile camera 130. For example, a fixed camera having a fixed position relative to the robot 100 may be provided, and the two imaging timings ST1 and ST2 may be captured by the fixed camera. Preferably, the fixed camera is relative to the robot coordinate system Σ Rcalibrated directly. However, using a mobile camera 130 allows for close imaging of the reference object RB. This offers the advantage of narrowing its field of view and improving resolution, enabling the coordinates of the representative position of the reference object RB to be determined with high accuracy. These fixed and mobile cameras 130 serve as the "second camera" in this invention.

[0024] Conveyor camera coordinate system Σ of the conveyor camera 320 CC In the coordinate system relative to the conveyor Σ C Fixed position relationship. Conveyor tracking information includes the conveyor coordinate system Σ C Relative to the robot coordinate system Σ R However, before the conveyor tracking information is corrected, the conveyor tracking information is inaccurate. Therefore, if the position in the image captured by the conveyor camera 320 is transformed into the robot coordinate system Σ R The coordinate value of the conveyor tracking information will contain an error. The error is eliminated by the correction processing of the conveyor tracking information. In other words, the conveyor coordinate system Σ C Relative to the "robot coordinate system Σ" specified by the conveyor tracking information CTI R The positional relationship” is corrected to an accurate relationship. The conveyor camera 320 is equivalent to the “first camera” of the present invention.

[0025] Figure 2 2 is a block diagram illustrating the functions of the control device 200. The control device 200 can be implemented as an information processing device such as a personal computer. The control device 200 includes a processor 210, a memory 220, an interface circuit 230, an input device 240 connected to the interface circuit 230, and a display unit 250. The interface circuit 230 is also connected to the joint encoder 122, the moving camera 130, the conveyor encoder 310, and the conveyor camera 320 in a wired or wireless manner. The joint encoder 122 is a position sensor that measures the position or displacement of multiple joints of the robot arm 120.

[0026] The processor 210 includes a calibration execution unit 212 and an image analysis unit 214. The calibration execution unit 212 performs the calibration processing of the conveyor tracking information, which will be described later. The image analysis unit 214 analyzes images captured by the mobile camera 130 or the conveyor camera 320 to identify the representative position of the reference object RB or the workpiece. Alternatively, the image analysis unit 214 can be configured as part of the calibration execution unit 212. The functions of these units 212 and 214 are implemented by the processor 210 executing a computer program stored in the memory 220. However, some or all of the functions of these units may also be implemented by hardware circuits.

[0027] The conveyor tracking information CTI and the robot control program RP are stored in the memory 220. The conveyor tracking information CTI includes the information representing the robot coordinate system Σ R The robot control program RP is composed of a plurality of instructions for causing the robot 100 to move.

[0028] Figure 3 This is a flowchart illustrating the steps of conveyor tracking information calibration processing. In step S110, calibration processing by the calibration execution unit 212 begins, and the user temporarily sets the conveyor tracking information CTI. Specifically, the calibration execution unit 212 receives the temporary setting value of the conveyor tracking information CTI input by the user and stores it in the memory 220. Alternatively, instead of the user inputting the temporary setting value, a pre-prepared initial value may be registered as the temporary setting value.

[0029] Figure 4 : is an explanatory diagram showing an example of the setting value of the conveyor tracking information CTI. Figure 4 In FIG, the image capturing area SA0 of the conveyor camera 320 at the reference image capturing time ST0 and the image capturing areas SA1 and SA2 of the mobile camera 130 at the first image capturing time ST1 and the second image capturing time ST2 are indicated by dotted lines. In addition, the image capturing area SA0 of the conveyor camera 320 is depicted in an inclined state, which indicates the conveyor coordinate system Σ C With respect to the "robot coordinate system Σ" specified by the conveyor tracking information CTI before correction R The positional relationship is wrong, so the position of the image captured by the conveyor camera 320 relative to the robot coordinate system Σ R Not identified as an accurate location.

[0030] like Figure 4 As shown, the conveyor coordinate system Σ C The coordinate system is defined by the CX axis and the CY axis, which are two axes in the horizontal direction orthogonal to each other, and the CZ axis in the vertical direction, and the CX axis direction is assumed to represent the conveying direction of the conveyor 300. In this embodiment, the conveyor coordinate system Σ C The coordinate origin C0 of the robot coordinate system Σ R The coordinate values c_X0, c_Y0 and the transfer direction angle θcnv indicating the CX axis direction are included in the conveyor tracking information CTI. The transfer direction angle θcnv is the value of the robot coordinate system Σ R The X-axis and the conveyor coordinate system Σ C The angle between the CX axis is the angle measured counterclockwise from the X axis. As mentioned above, the conveyor coordinate system Σ C Conveyor camera coordinate system Σ relative to the conveyor camera 320 CC fixed.

[0031] The temporary setting values of the conveyor tracking information CTI include the following items:

[0032] (A) Robot coordinate system Σ as the coordinate origin C0 of the conveyor 300 R Temporary setting coordinate values of X and Y coordinate values c_X0, c_Y0;

[0033] (B) Temporarily set angle value θcnv of the conveying direction of the conveyor 300;

[0034] (C) Temporary setting speed value Vcnv of the conveyor speed or temporary setting information value (Lr0, Nr0) of the section information.

[0035] The temporary setting information value (Lr0, Nr0) of the section information includes the conveyor movement amount Lr0 of the conveyor 300 in a predetermined specific section on the conveyor 300 and the encoder pulse amount Nr0 of the conveyor encoder 310 corresponding to the conveyor movement amount Lr0. In this embodiment, the "specific section" is set to the section from the first imaging timing ST1 to the second imaging timing ST2. Furthermore, the above-mentioned item (C) as the conveyor tracking information CTI may include both the conveyor speed and the section information, or only one of them. Since the section information includes the conveyor movement amount Lr0 and the encoder pulse amount Nr0 in a specific section on the conveyor 300, it can be considered as a type of information indicating the movement of the conveyor 300.

[0036] The temporary setting value of the conveyor tracking information CTI is set by Figure 3 In this example, the conveyor coordinate system Σ is defined based on the temporary set coordinate values c_X0, c_Y0 of the coordinate origin C0 of the conveyor 300 and the temporary set angle value θcnv of the conveyor 300's transfer direction. C Relative to the robot coordinate system Σ R The positional relationship of the robot coordinate system Σ R and conveyor coordinate system Σ C The coordinate transformation matrix of the coordinate transformation between is used as the temporary setting value of the conveyor tracking information CTI. In addition, as the temporary setting speed value Vcnv of the conveyor speed, a value expressed in the unit [pulse / second] obtained by dividing the number of pulses of the conveyor encoder 310 by time can be used.

[0037] In step S120, the operator places the reference object RB on the conveyor 300 and starts the operation of the conveyor 300. Thereafter, the conveyor 300 operates at a constant speed.

[0038] In step S130, the calibration execution unit 212 performs the following operations: Figure 1The three shooting timings ST0, ST1, and ST2 shown capture images of the reference object RB and obtain encoder measurement values. The conveyor camera 320 performs shooting at the reference shooting timing ST0, and the mobile camera 130 performs shooting at the first shooting timing ST1 and the second shooting timing ST2. Specifically, for example, the conveyor camera 320 repeatedly performs shooting at regular intervals, and can select the timing at which the entire object RB that can be identified as the reference object RB enters its field of view as the reference shooting timing ST0. As the "regular interval", a sufficiently short time of 0.1 to 0.2 seconds is set, for example. The first shooting timing ST1 and the second shooting timing ST2 are the same. In addition, the first shooting timing ST1 is preferably the timing on the upstream side of the working range in which the robot arm 120 can operate on the workpiece. In addition, the second shooting timing ST2 is preferably the timing on the downstream side of the working range in which the robot arm 120 can operate on the workpiece.

[0039] At the three imaging timings ST0, ST1, and ST2, the measurement values of the conveyor encoder 310 and the measurement values of the joint encoder 122 are also acquired. The measurement values of the conveyor encoder 310 are used to determine the position of the conveyor 300 at the imaging timings ST0, ST1, and ST2. In addition, the measurement values of the joint encoder 122 are used to determine the fingertip coordinate system Σ of the robot arm 120 at the imaging timings ST0, ST1, and ST2. T Position and posture. Figure 1 As explained in , due to the movement of the camera coordinate system Σ MC Relative to the fingertip coordinate system Σ T Since it is calibrated, it is possible to accurately transform any position in the image captured by the mobile camera 130 into the robot coordinate system Σ using the measurement value of the joint encoder 122. R The coordinate value of .

[0040] In step S140 , the image analyzing unit 214 analyzes the images captured at the three capturing timings ST0 , ST1 , and ST2 , respectively, and the measured coordinate values of the representative positions of the reference object RB can be obtained.

[0041] Figure 5 It is an explanatory diagram showing various measurement values at three imaging timings ST0 , ST1 , and ST2 . Figure 5 The contents of the reference numerals shown are as follows.

[0042] Images captured at each shooting time

[0043] (a) IM0 : A reference image acquired by imaging the reference object RB by the conveyor camera 320 at the reference imaging timing ST0 .

[0044] As described above, the “conveyor coordinate system ΣC Relative to the robot coordinate system Σ R Therefore, the reference image IM0 captured by the conveyor camera 320 is not correct relative to the robot coordinate system Σ R was not identified as an accurate location. Therefore, Figure 5 In FIG, the reference image IM0 is depicted as being deviated from the correct position.

[0045] (b) IM1 : a first image acquired by photographing the reference object RB by the mobile camera 130 at the first photographing timing ST1 .

[0046] (c) IM2: a second image acquired by photographing the reference object RB by the mobile camera 130 at the second photographing timing ST2.

[0047] As described above, since the mobile camera 130 is relative to the fingertip coordinate system Σ T is calibrated, so in Figure 5 In the robot coordinate system Σ R In the exact position. Figure 5 In the example shown in FIG. 5 , the directions of the sides of the first image IM1 and the second image IM2 are parallel to the transfer direction AD of the conveyor 300 . However, the directions of the first image IM1 and the second image IM2 are arbitrary.

[0048] Measurement values of conveyor encoder 310

[0049] (a) enc0: The measurement value of the conveyor encoder 310 at the reference imaging timing ST0.

[0050] (b) enc1: The measurement value of the conveyor encoder 310 at the first imaging timing ST1.

[0051] (c) enc2: The measurement value of the conveyor encoder 310 at the second imaging timing ST2.

[0052] Coordinate values identified through image analysis

[0053] (a) cnv_X0, cnv_Y0: Robot coordinate system Σ of reference position P0 obtained by analyzing reference image IM0 to find the representative position of reference object RB R The measured coordinate values in .

[0054] The measured coordinate values cnv_X0 and cnv_Y0 of the reference position P0 include errors.

[0055] (b) mc_X1, mc_Y1: The robot coordinate system Σ of the first position P1 obtained by analyzing the first image IM1 to determine the representative position of the reference object RB RThe measured coordinate values in .

[0056] (c) mc_X2, mc_Y2: The robot coordinate system Σ of the second position P2 obtained by analyzing the representative position of the reference object RB R The measured coordinate values in .

[0057] The measured coordinate values mc_X1, mc_Y1 of the first position P1 and the measured coordinate values mc_X2, mc_Y2 of the second position P2 are accurate values. In the present invention, the coordinate values recognized by image analysis are referred to as "measured coordinate values."

[0058] In step S150, the calibration execution unit 212 calculates calibration values for the conveyor tracking information CTI using the measurement results, including the measured coordinate values of the three positions P0, P1, and P2, and the encoder measurement values. The calibration values for the conveyor tracking information CTI are used to modify the temporary settings of the conveyor tracking information CTI so that the position and movement of the conveyor 300 indicated by the conveyor tracking information CTI match the various measurement results.

[0059] Figure 6 1 is an explanatory diagram showing various measured values and calculated values for obtaining the correction value of the conveyor tracking information CTI. Figure 6 Except in Figure 5 In addition to the various measured values shown in , the following calculated values are also added.

[0060] Calculated coordinate values of each position

[0061] (a) mc_X0, mc_Y0: calculated coordinate values of the reference position CP0 obtained by extrapolating the first position P1 and the second position P2 obtained by analyzing the images IM1 and IM2 using the measurement values of the conveyor encoder 310.

[0062] (b) cnv_X1, cnv_Y1: calculated coordinate values of the first position CP1 calculated using the measured coordinate values cnv_X0, cnv_Y0 of the reference position P0 obtained by analyzing the reference image IM0, the temporary set angle value θcnv of the conveyor 300 in the conveyor tracking information CTI, and the measurement value of the conveyor encoder 310.

[0063] (c) cnv_X2, cnv_Y2: Calculated coordinate values of the second position CP2 calculated using the measured coordinate values cnv_X0, cnv_Y0 of the reference position P0 obtained by analyzing the reference image IM0, the temporary set angle value θcnv of the conveyor 300 included in the conveyor tracking information CTI, and the measurement value of the conveyor encoder 310.

[0064] In the present invention, coordinate values recognized by image analysis are referred to as "measured coordinate values," and coordinate values obtained by calculation using measurement results other than images are referred to as "calculated coordinate values."

[0065] The distance between two adjacent locations

[0066] (a) Lm1: The distance between the reference position CP0 and the first position P1 obtained by extrapolation from the first position P1 and the second position P2 represented by the measured coordinate values.

[0067] (b) Lm2: The distance between the first position P1 and the second position P2 represented by the measured coordinate values.

[0068] (c) Lc1: The distance between the reference position P0 represented by the measured coordinate values and the first position CP1 represented by the calculated coordinate values.

[0069] (d) Lc2: The distance between the first position CP1 and the second position CP2 represented by the calculated coordinate values.

[0070] The calculated coordinate values cnv_X1 and cnv_Y1 of the first position CP1 can be calculated, for example, by the following equations.

[0071] cnv_X1=cnv_X0+K(enc1-enc0)×cosθcnv (1a)

[0072] cnv_Y1=cnv_Y0+K(enc1-enc0)×sinθcnv (1b)

[0073] Here, K is the number of pulses of the conveyor encoder 310 converted into the robot coordinate system Σ R The calculated coordinate values cnv_X2 and cnv_Y2 of the second position CP2 are also substantially the same.

[0074] The X coordinate value mc_X0 of the calculated coordinate values mc_X0 and mc_Y0 of the reference position CP0 obtained by extrapolating the first position P1 and the second position P2 is calculated by, for example, the following equation.

[0075] mc_X0=mc_x1+Lm1_x …(2a)

[0076] Lm1_x=Lm2_x×(enc1-enc0) / (enc2-enc1)…(2b)

[0077] Lm2_x=mc_x1-mc_x2 …(2c)

[0078] Here, Lm1_x is the difference in X-coordinate values corresponding to the distance Lm1, Lm2_x is the difference in X-coordinate values corresponding to the distance Lm2, and enc0, enc1, and enc2 are the measured values of the conveyor encoder 310 at the three imaging timings ST0, ST1, and ST2. The Y-coordinate value mc_Y0 can also be calculated in the same way. Alternatively, instead of using equations (2a) to (2c), the calculated coordinate values mc_X0 and mc_Y0 of the reference position CP0 can be obtained by performing an extrapolation operation on the first position P1 and the second position P2 using the time difference between the three imaging timings ST0, ST1, and ST2.

[0079] For example, the following values are calculated as correction values of the conveyor tracking information CTI.

[0080] (A) Correction values ΔX, ΔY of the coordinate values of the coordinate origin C0 of the conveyor 300

[0081] ΔX=mc_X0-cnv_X0 (3a)

[0082] ΔY=mc_Y0-cnv_Y0 (3b)

[0083] These correction values ΔX and ΔY are the differences between the calculated coordinate values mc_X0 and mc_Y0 of the reference position CP0 and the measured coordinate values cnv_X0 and cnv_Y0 of the reference position P0. Furthermore, these correction values ΔX and ΔY can be considered as values used to bring the calculated coordinate values mc_X0 and mc_Y0 of the reference position CP0 into line with the measured coordinate values cnv_X0 and cnv_Y0 of the reference position P0. By adding these correction values ΔX and ΔY to the provisional coordinate values c_X0 and c_Y0 of the coordinate origin C0, the coordinate values of the coordinate origin C0 in the conveyor tracking information CTI can be corrected to accurate values.

[0084] (B) Correction value Δθ of the conveying direction angle of the conveyor 300

[0085] Δθ=θmc-θcnv (4a)

[0086] θmc=arctan((mc_y2-mc_y1) / (mc_x2-mc_x1)) (4b)

[0087] This correction value Δθ is the difference between the actual measured value θmc of the conveyor direction angle and the provisional set angle value θcnv. Furthermore, this correction value Δθ can be considered a value used to bring the set value of the conveyor direction angle in the conveyor tracking information CTI into line with the actual measured value θmc. By adding this correction value Δθ to the provisional set angle value θcnv, the conveyor direction angle in the conveyor tracking information CTI can be corrected to an accurate value.

[0088] Alternatively, instead of the above-mentioned formula (4a), the correction value θratio of the feed direction angle θcnv may be obtained according to the following formula (5).

[0089] θratio=θmc / θcnv (5)

[0090] This correction value θratio is the ratio of the actual measured value θmc of the transport direction angle to the provisional set angle value θcnv. Furthermore, this correction value θratio can also be considered a value used to bring the set value of the transport direction angle in the conveyor tracking information CTI into line with the actual measured value θmc. By multiplying this correction value θratio by the provisional set angle value θcnv, the transport direction angle can be corrected to an accurate value.

[0091] (C1) Conveyor speed correction value Vratio

[0092] Vratio=Vm / Vcnv=Lm2 / Lc2 (6a)

[0093] Lm2=SQRT((mc_x1-mc_x2) 2 +(mc_y1-mc_y2) 2 ) (6b)

[0094] Lc2=SQRT((cnv_x1-cnv_x2) 2 +(cnv_y1-cnv_y2) 2 ) (6c)

[0095] Here, Lm2 is the distance between the first position P1 and the second position P2, represented by the measured coordinate values; Lc2 is the distance between the first position CP1 and the second position CP2, represented by the calculated coordinate values; Vm is the measured value of the conveyor speed; and Vcnv is the provisional set speed value. Distance Lm2 is proportional to the measured value Vm of the conveyor speed, and distance Lc2 is proportional to the provisional set speed value Vcnv. Furthermore, the correction value Vratio can be represented by the ratio of the first distance value Lm2 between the first position P1 and the second position P2, represented by the measured coordinate values, to the second distance value Lc2 between the first position CP1 and the second position CP2, represented by the calculated coordinate values. Furthermore, the correction value Vratio can be considered a value used to align the set value of the conveyor speed in the conveyor tracking information CTI with the measured value Vm. Multiplying this correction value Vratio by the provisional set speed value Vcnv in the conveyor tracking information CTI corrects the conveyor speed to an accurate value.

[0096] Alternatively, instead of the above-mentioned formula (6a), the correction value ΔV of the conveyor speed may be obtained according to the following formula (7).

[0097] ΔV=Vm-Vcnv=(Lm2 / Δt)-Vcnv (7)

[0098] Here, Δt is the time difference between the two capture timings ST1 and ST2. The correction value ΔV is the difference between the actual conveyor speed value Vm and the provisional set speed value Vcnv, obtained by dividing the distance Lm2 between the two positions P1 and P2 by the time difference Δt. Furthermore, this correction value ΔV can also be considered a value used to align the set conveyor speed value in the conveyor tracking information CTI with the actual conveyor speed value Vm. Adding this correction value ΔV to the provisional set speed value Vcnv in the conveyor tracking information CTI corrects the conveyor speed to an accurate value.

[0099] (C2) Correction values Lratio and Nratio of conveyor movement amount and encoder pulse amount in section information

[0100] Lratio=Lrm / Lr0=Lm2 / Lc2 (8a)

[0101] Nratio=Nrm / Nr0=Lm2 / Lc2 (8b)

[0102] Here, Lrm is the actual measured value of the conveyor movement amount in the interval from the first imaging timing ST1 to the second imaging timing ST2, Lr0 is the temporary set value of the conveyor movement amount, Nrm is the actual measured value of the encoder pulse amount in the interval from the first imaging timing ST1 to the second imaging timing ST2, and Nr0 is the temporary set value of the encoder pulse amount. Furthermore, Lm2 is given by equation (6b) above and is the distance between the first position P1 and the second position P2 represented by the measured coordinate values. Furthermore, Lc2 is given by equation (6c) above and is the distance between the first position CP1 and the second position CP2 represented by the calculated coordinate values. As shown in (8b) above, since the relationship Nrm / Nr0 = Lm2 / Lc2 exists, the calculation of the correction value Nratio in (8b) above can also be performed using the distance ratio Lm2 / Lc2. Alternatively, since the actual measured value Nrm of the encoder pulse amount is also obtained, the calculation of the correction value Nratio can also be performed using the encoder pulse amount ratio Nrm / Nr0.

[0103] The correction value Lratio for the conveyor movement amount can be considered a value used to ensure that the set value for the conveyor movement amount in the section information of the conveyor tracking information CTI is consistent with the actual value of the conveyor movement amount obtained from the measured coordinate values of the first position P1 and the second position P2. Furthermore, the correction value Nratio for the encoder pulse amount can be considered a value used to ensure that the set value for the encoder pulse amount in the section information is consistent with the actual value of the pulse increment of the encoder 310 in the section from the first imaging timing ST1 to the second imaging timing ST2. By multiplying these correction values Lratio and Nratio by their respective temporary set values Lr0 and Nr0, the conveyor movement amount and encoder pulse amount in the section information can be corrected to accurate values.

[0104] In step S160, the correction execution unit 212 corrects the conveyor tracking information CTI using the correction value obtained in step S150. As a result, the position and movement of the conveyor 300 indicated by the conveyor tracking information CTI are corrected to be accurate.

[0105] Figure 7 This is an explanatory diagram showing various measurement values after the correction processing of the conveyor tracking information CTI, which is different from the values before the correction processing. Figure 6 If the conveyor tracking information CTI is accurately corrected, the conveyor coordinate system Σ is accurately set. C Relative to the robot coordinate system Σ R The positional relationship of the conveyor is also accurately set, and the conveyor speed, section information Lrm, Nrm are also accurately set. Figure 6 The two reference positions P0 and CP0 shown are in the robot coordinate system Σ R Similarly, the two first positions P1 and CP1 and the two second positions P2 and CP2 also coincide with each other. In other words, the conveyor tracking information CTI is corrected so that the measured coordinate values at the reference position, the first position, and the second position coincide with the calculated coordinate values.

[0106] After the conveyor tracking information CTI calibration process is complete, the camera 130 no longer needs to be moved and can be removed from the robot arm 120. When performing work on an actual workpiece, the workpiece's position is identified by analyzing the workpiece image captured by the conveyor camera 320. The subsequent workpiece position can be calculated using the set values of the conveyor tracking information CTI. Therefore, the robot 100 can perform work based on the calculated workpiece position.

[0107] As described above, in the above embodiment, the temporary set value of the conveyor tracking information CTI is corrected using the measurement results, including the images IM0, IM1, and IM2 acquired at the three imaging timings ST0, ST1, and ST2, and the measurement values of the conveyor encoder 310, so that the position and movement of the conveyor 300 indicated by the conveyor tracking information CTI match the measurement results. As a result, the conveyor tracking information CTI can be accurately set without stopping the conveyor 300.

[0108] Other implementation methods:

[0109] The present invention is not limited to the above-mentioned embodiments and can be implemented in various ways without departing from its purpose. For example, the present invention can also be implemented in the following manner (aspect). In order to solve part or all of the technical problems of the present invention, or to achieve part or all of the effects of the present invention, the technical features in the above-mentioned embodiments corresponding to the technical features in the various modes described below can be appropriately replaced or combined. In addition, if the technical feature is not described as an essential technical feature in this specification, it can be appropriately deleted.

[0110] (1) According to a first aspect of the present invention, a correction method is provided, wherein the correction method is a correction method for correcting conveyor tracking information in a robot system, the robot system comprising: a conveyor; a robot that operates on a workpiece conveyed by the conveyor; an encoder that detects movement of the conveyor; and a camera that photographs the workpiece to measure the position of the workpiece carried on the conveyor, wherein the conveyor tracking information is information indicating the position and movement of the conveyor in the robot coordinate system. The correction method includes the following steps: (a) temporarily setting the conveyor tracking information; (b) when the conveyor moves at a fixed speed, by photographing the reference object carried on the conveyor at the reference shooting timing, the first shooting timing and the second shooting timing respectively, obtaining a reference image, a first image and a second image, and obtaining the measurement values of the encoder at the reference shooting timing, the first shooting timing and the second shooting timing as the reference encoder value, the first encoder value and the second encoder value; (c) by analyzing the reference image, the first image and the second image, respectively obtaining the representative position of the reference object as the reference position, the first position and the second position, and respectively obtaining the measurement coordinate values of the reference position, the first position and the second position in the robot coordinate system; and (d) using the measurement coordinate values including the reference position, the first position and the second position and the measurement results of the reference encoder value, the first encoder value and the second encoder value, correcting the temporary setting value of the conveyor tracking information so that the position and movement of the conveyor represented by the conveyor tracking information match the measurement results.

[0111] According to this calibration method, the conveyor tracking information can be accurately set without stopping the conveyor.

[0112] (2) In the above-mentioned correction method, the process (a) may include a process of setting the following values as temporary setting values of the conveyor tracking information: (i) a temporarily set coordinate value representing the coordinate value of the coordinate origin of the conveyor in the robot coordinate system; (ii) a temporarily set angle value representing the moving direction angle of the conveyor; and (iii) a temporarily set speed value representing the conveyor speed or a temporarily set information value of interval information, wherein the interval information may include the conveyor movement amount in the interval from the first shooting timing to the second shooting timing and the encoder pulse amount corresponding to the conveyor movement amount.

[0113] According to this calibration method, the position and movement of the conveyor can be specified by temporarily setting the value of the conveyor tracking information.

[0114] (3) In the above-mentioned correction method, the process (d) may include the following processes: (d1) obtaining a calculated coordinate value of the reference position by extrapolating the first position and the second position using the measured coordinate values of the first position and the second position, and adding the difference between the calculated coordinate value of the reference position and the measured coordinate value to the temporarily set coordinate value of the coordinate origin of the conveyor; (d2) correcting the temporarily set angle value so that the set value of the transfer direction angle in the conveyor tracking information is consistent with the actual measured value of the transfer direction angle obtained based on the measured coordinate values of the first position and the second position. consistent; and (d3) correcting the temporary set speed value so that the set value of the conveyor speed in the conveyor tracking information is consistent with the actual value of the conveyor speed obtained based on the measured coordinate values of the first position and the second position, or correcting the temporary set information value so that the set value of the conveyor movement amount in the conveyor tracking information is consistent with the actual value of the conveyor movement amount obtained based on the measured coordinate values of the first position and the second position, and the set value of the encoder pulse amount is consistent with the actual value of the pulse increment of the encoder in the interval from the first shooting timing to the second shooting timing.

[0115] According to this correction method, the conveyor tracking information can be corrected so that the conveyor tracking information matches the measurement result.

[0116] (4) In the above-mentioned correction method, the camera may include: a first camera, set at a fixed position relative to the conveyor, performing shooting at the reference shooting timing; and a second camera, set on the robotic arm of the robot, performing shooting at the first shooting timing and the second shooting timing, the first camera coordinate system of the first camera may be in a fixed relationship relative to the conveyor coordinate system specified by the conveyor tracking information, and the second camera coordinate system of the second camera may be calibrated relative to the robot coordinate system.

[0117] According to this calibration method, three images can be captured by two cameras, and the mobile camera can capture images close to the reference object. Therefore, by narrowing its field of view and improving the resolution, the coordinate values of the representative position of the reference object can be obtained with high precision.

[0118] (5) According to a second aspect of the present invention, a calibration system for calibrating conveyor tracking information is provided. The calibration system includes: a conveyor; a robot that operates on a workpiece conveyed by the conveyor; an encoder that detects the movement of the conveyor; a camera that images the workpiece to measure the position of the workpiece carried on the conveyor; and a calibration execution unit that calibrates the conveyor tracking information indicating the position and movement of the conveyor in the robot coordinate system. The correction execution unit performs the following processing: (a) temporarily setting the conveyor tracking information; (b) when the conveyor moves at a fixed speed, by photographing the reference object carried on the conveyor at the reference shooting timing, the first shooting timing and the second shooting timing respectively, obtaining a reference image, a first image and a second image, and obtaining the measurement values of the encoder at the reference shooting timing, the first shooting timing and the second shooting timing as the reference encoder value, the first encoder value and the second encoder value; (c) by analyzing the reference image, the first image and the second image, respectively obtaining the representative position of the reference object as the reference position, the first position and the second position, and respectively obtaining the measurement coordinate values of the reference position, the first position and the second position in the robot coordinate system; and (d) using the measurement coordinate values including the reference position, the first position and the second position and the measurement results of the reference encoder value, the first encoder value and the second encoder value, correcting the temporary setting value of the conveyor tracking information so that the position and movement of the conveyor represented by the conveyor tracking information match the measurement results.

[0119] According to this calibration system, the conveyor tracking information can be accurately set without stopping the conveyor.

[0120] (6) According to a third embodiment of the present invention, a storage medium is provided, wherein the storage medium stores a computer program, and in a robot system, the computer program causes a processor to execute processing for correcting conveyor tracking information, the robot system comprising: a conveyor; a robot that operates on a workpiece conveyed by the conveyor; an encoder that detects movement of the conveyor; and a camera that photographs the workpiece to measure the position of the workpiece carried on the conveyor, wherein the conveyor tracking information is information indicating the position and movement of the conveyor in the robot coordinate system. The computer program causes the processor to perform the following processing: (a) temporarily setting the conveyor tracking information; (b) when the conveyor moves at a fixed speed, by photographing the reference object carried on the conveyor at the reference shooting timing, the first shooting timing and the second shooting timing, respectively, obtaining a reference image, a first image and a second image, and obtaining the measurement values of the encoder at the reference shooting timing, the first shooting timing and the second shooting timing as the reference encoder value, the first encoder value and the second encoder value; (c) by analyzing the reference image, the first image and the second image, respectively obtaining the representative position of the reference object as the reference position, the first position and the second position, and respectively obtaining the measurement coordinate values of the reference position, the first position and the second position in the robot coordinate system; and (d) using the measurement coordinate values including the reference position, the first position and the second position and the measurement results of the reference encoder value, the first encoder value and the second encoder value, correcting the temporary setting value of the conveyor tracking information so that the position and movement of the conveyor represented by the conveyor tracking information match the measurement results.

[0121] According to this computer program, conveyor tracking information can be accurately set without stopping the conveyor.

[0122] The present invention can also be implemented in various forms other than those described above, such as a robot system including a robot and a robot controller, a computer program for implementing the functions of the robot controller, or a non-transitory storage medium recording the computer program.

Claims

1. A calibration method, characterized in that: The calibration method is a calibration method for calibrating conveyor tracking information in a robot system, the robot system comprising: a conveyor; a robot that operates on a workpiece conveyed by the conveyor; an encoder that detects movement of the conveyor; and a camera that photographs the workpiece to measure the position of the workpiece carried on the conveyor, wherein the conveyor tracking information is information indicating the position and movement of the conveyor in a robot coordinate system. The calibration method comprises the following steps: (a) temporarily setting the conveyor tracking information; (b) capturing images of a reference object carried on the conveyor at a reference capturing timing, a first capturing timing, and a second capturing timing, respectively, while the conveyor is moving at a constant speed, thereby acquiring a reference image, a first image, and a second image, and acquiring measurement values of the encoder at the reference capturing timing, the first capturing timing, and the second capturing timing as a reference encoder value, a first encoder value, and a second encoder value; (c) analyzing the reference image, the first image, and the second image to determine representative positions of the reference object as a reference position, a first position, and a second position, respectively, and determining measured coordinate values of the reference position, the first position, and the second position in the robot coordinate system, respectively; as well as (d) using the measurement results including the measured coordinate values of the reference position, the first position, and the second position and the reference encoder value, the first encoder value, and the second encoder value, to correct the temporary setting value of the conveyor tracking information so that the position and movement of the conveyor indicated by the conveyor tracking information match the measurement results, The step (a) includes setting the following values as temporary setting values of the conveyor tracking information: (i) a temporary set coordinate value representing the coordinate value of the coordinate origin of the conveyor in the robot coordinate system; (ii) a temporarily set angle value representing a conveying direction angle of the conveyor; as well as (iii) a temporary set speed value indicating the conveyor speed or a temporary set information value indicating the section information, The section information includes a conveyor movement amount in a section from the first imaging timing to the second imaging timing and an encoder pulse amount corresponding to the conveyor movement amount. The step (d) includes the following steps: (d1) extrapolating the first position and the second position using the measured coordinate values of the first position and the second position to obtain a calculated coordinate value of the reference position, and adding a difference between the calculated coordinate value of the reference position and the measured coordinate value to the temporarily set coordinate value of the coordinate origin of the conveyor; (d2) correcting the temporarily set angle value so that the set value of the transfer direction angle in the conveyor tracking information is consistent with the actual measured value of the transfer direction angle obtained based on the measured coordinate values of the first position and the second position; as well as (d3) correcting the temporary set speed value so that the set value of the conveyor speed in the conveyor tracking information is consistent with the actual measured value of the conveyor speed obtained based on the measured coordinate values of the first position and the second position, or Correct the temporary setting information value so that the setting value of the conveyor movement amount in the conveyor tracking information is consistent with the actual value of the conveyor movement amount obtained based on the measured coordinate values of the first position and the second position, and the setting value of the encoder pulse amount is consistent with the actual value of the pulse increment of the encoder in the interval from the first shooting timing to the second shooting timing.

2. The calibration method according to claim 1, wherein: The camera includes: a first camera, which is set at a fixed position relative to the conveyor and performs imaging at the reference imaging timing; and A second camera is provided on the robot arm, and performs photography at the first photography timing and the second photography timing. a first camera coordinate system of the first camera is in a fixed relationship with respect to a conveyor coordinate system specified by the conveyor tracking information, A second camera coordinate system of the second camera is calibrated relative to the robot coordinate system.

3. A correction system, characterized in that: The correction system corrects the conveyor tracking information and has: conveyors; a robot for operating on a workpiece conveyed by the conveyor; an encoder to detect movement of the conveyor; a camera for photographing the workpiece to measure a position of the workpiece carried on the conveyor; as well as a calibration execution unit that calibrates the conveyor tracking information indicating the position and movement of the conveyor in the robot coordinate system; The calibration execution unit performs the following processing: (a) temporarily setting the conveyor tracking information; (b) capturing images of a reference object carried on the conveyor at a reference capturing timing, a first capturing timing, and a second capturing timing, respectively, while the conveyor is moving at a constant speed, thereby acquiring a reference image, a first image, and a second image, and acquiring measurement values of the encoder at the reference capturing timing, the first capturing timing, and the second capturing timing as a reference encoder value, a first encoder value, and a second encoder value; (c) analyzing the reference image, the first image, and the second image to determine representative positions of the reference object as a reference position, a first position, and a second position, respectively, and determining measured coordinate values of the reference position, the first position, and the second position in the robot coordinate system, respectively; as well as (d) using the measurement results including the measured coordinate values of the reference position, the first position, and the second position and the reference encoder value, the first encoder value, and the second encoder value, to correct the temporary setting value of the conveyor tracking information so that the position and movement of the conveyor indicated by the conveyor tracking information match the measurement results, The processing (a) includes the step of setting the following values as temporary setting values of the conveyor tracking information: (i) a temporary set coordinate value representing the coordinate value of the coordinate origin of the conveyor in the robot coordinate system; (ii) a temporarily set angle value representing a conveying direction angle of the conveyor; as well as (iii) a temporary set speed value indicating the conveyor speed or a temporary set information value indicating the section information, The section information includes a conveyor movement amount in a section from the first imaging timing to the second imaging timing and an encoder pulse amount corresponding to the conveyor movement amount. The process (d) includes the following processes: (d1) extrapolating the first position and the second position using the measured coordinate values of the first position and the second position to obtain a calculated coordinate value of the reference position, and adding a difference between the calculated coordinate value of the reference position and the measured coordinate value to the temporarily set coordinate value of the coordinate origin of the conveyor; (d2) correcting the temporarily set angle value so that the set value of the transfer direction angle in the conveyor tracking information is consistent with the actual measured value of the transfer direction angle obtained based on the measured coordinate values of the first position and the second position; as well as (d3) correcting the temporary set speed value so that the set value of the conveyor speed in the conveyor tracking information is consistent with the actual measured value of the conveyor speed obtained based on the measured coordinate values of the first position and the second position, or Correct the temporary setting information value so that the setting value of the conveyor movement amount in the conveyor tracking information is consistent with the actual value of the conveyor movement amount obtained based on the measured coordinate values of the first position and the second position, and the setting value of the encoder pulse amount is consistent with the actual value of the pulse increment of the encoder in the interval from the first shooting timing to the second shooting timing.

4. A storage medium, characterized in that The storage medium stores a computer program. In a robot system, the computer program causes a processor to execute processing for correcting conveyor tracking information. The robot system includes: a conveyor; a robot that performs work on a workpiece conveyed by the conveyor; an encoder that detects movement of the conveyor; and a camera that images the workpiece to measure a position of the workpiece carried on the conveyor. The conveyor tracking information is information indicating the position and movement of the conveyor in a robot coordinate system. The computer program causes the processor to perform the following processing: (a) temporarily setting the conveyor tracking information; (b) capturing images of a reference object carried on the conveyor at a reference capturing timing, a first capturing timing, and a second capturing timing, respectively, while the conveyor is moving at a constant speed, thereby acquiring a reference image, a first image, and a second image, and acquiring measurement values of the encoder at the reference capturing timing, the first capturing timing, and the second capturing timing as a reference encoder value, a first encoder value, and a second encoder value; (c) analyzing the reference image, the first image, and the second image to determine representative positions of the reference object as a reference position, a first position, and a second position, respectively, and determining measured coordinate values of the reference position, the first position, and the second position in the robot coordinate system, respectively; as well as (d) using the measurement results including the measured coordinate values of the reference position, the first position, and the second position and the reference encoder value, the first encoder value, and the second encoder value, to correct the temporary setting value of the conveyor tracking information so that the position and movement of the conveyor indicated by the conveyor tracking information match the measurement results, The processing (a) includes the step of setting the following values as temporary setting values of the conveyor tracking information: (i) a temporary set coordinate value representing the coordinate value of the coordinate origin of the conveyor in the robot coordinate system; (ii) a temporarily set angle value representing a conveying direction angle of the conveyor; as well as (iii) a temporary set speed value indicating the conveyor speed or a temporary set information value indicating the section information, The section information includes a conveyor movement amount in a section from the first imaging timing to the second imaging timing and an encoder pulse amount corresponding to the conveyor movement amount. The process (d) includes the following processes: (d1) extrapolating the first position and the second position using the measured coordinate values of the first position and the second position to obtain a calculated coordinate value of the reference position, and adding a difference between the calculated coordinate value of the reference position and the measured coordinate value to the temporarily set coordinate value of the coordinate origin of the conveyor; (d2) correcting the temporarily set angle value so that the set value of the transfer direction angle in the conveyor tracking information is consistent with the actual measured value of the transfer direction angle obtained based on the measured coordinate values of the first position and the second position; as well as (d3) correcting the temporary set speed value so that the set value of the conveyor speed in the conveyor tracking information is consistent with the actual measured value of the conveyor speed obtained based on the measured coordinate values of the first position and the second position, or Correct the temporary setting information value so that the setting value of the conveyor movement amount in the conveyor tracking information is consistent with the actual value of the conveyor movement amount obtained based on the measured coordinate values of the first position and the second position, and the setting value of the encoder pulse amount is consistent with the actual value of the pulse increment of the encoder in the interval from the first shooting timing to the second shooting timing.

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