Control method and control device of robot system

Abstract

To provide a control method and a control device of a robot system that can perform conveyance of an object with high accuracy.SOLUTION: A control method of a robot system, which holds an object being conveyed by a conveying device and conveys the held object to a target position, includes: a conveyance starting position predicting step of determining a predicted position at which conveyance of the object to the target position is started; a conveyance route generating step of generating a conveyance route for the object from the predicted position to the target position; a conveyance starting step of starting conveyance of the held object to the target position; and a correcting step of correcting the conveyance route, using a difference between a starting position at which the conveyance is started and the predicted position.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control method and a control device for a robot system. [Background technology]

[0002] For example, the tracking control method for a robot described in Patent Document 1 includes the steps of continuously capturing images of a workpiece being transported by a conveyor with a camera positioned directly above the conveyor and detecting the position and transport speed of the workpiece based on the image capture results, and estimating a target position for the tracking operation by repeated calculations from the workpiece transport speed and the robot operation time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-105217 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, even if the robot can start tracking the workpiece being transported by the conveyor, it does not necessarily mean that the robot can pick up the workpiece and transport it to the target position. In particular, when the transport path after picking up is predetermined, if the actual position where the transport after picking up starts deviates from the start point of the transport path, the deviation directly leads to a deviation from the target position. [Means for solving the problem]

[0005] A control method for a robot system according to the present invention is a control method for a robot system that holds an object to be transported by a transport device and transports the held object to a target position, comprising the steps of: a transfer start position prediction step of determining a predicted position at which transfer of the object to the target position is to be started; a transport path generating step of generating a transport path of the object from the predicted position to the target position; a conveyance start step of starting conveyance of the held object to the target position; and a correction step of correcting the transport path using a difference between a start position at which the transport is started and the predicted position.

[0006] The control device of the present invention is a control device for a robot system that holds an object to be transported by a transport device and transports the held object to a target position, a transfer start position prediction step of determining a predicted position at which transfer of the object to the target position is to be started; a transport path generating step of generating a transport path of the object from the predicted position to the target position; a conveyance start step of starting conveyance of the held object to the target position; A correction step is executed to correct the transport path using a difference between a start position at which the transport is started and the predicted position. [Brief description of the drawings]

[0007] [Figure 1] 1 is an overall configuration diagram of a robot system according to a preferred embodiment. [Diagram 2] 1 is a flowchart showing a control method for the robot system. [Diagram 3] 11 is a front view showing a state in which the transport device has started transporting the workpiece; FIG. [Figure 4] 4 is a front view showing how the imaging unit images the workpiece. FIG. [Diagram 5] FIG. 11 is a top view showing the generated transport path. [Figure 6] FIG. 4 is a front view showing a state in which the robot holds a workpiece. [Figure 7] FIG. 11 is a top view showing a state in which a positional deviation occurs in a target position. [Figure 8]FIG. 11 is a top view showing a correction transport path. [Figure 9] FIG. 11 is a top view showing a transport path corrected by a first correction method. [Figure 10] FIG. 11 is a top view showing a transport path corrected by a second correction method. [Figure 11] FIG. 11 is a top view showing a transport path corrected by a third correction method. [Figure 12] FIG. 13 illustrates an example of a graphic interface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control method and a control device for a robot system according to the present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0009] FIG. 1 is an overall configuration diagram of a robot system according to a preferred embodiment. FIG. 2 is a flowchart showing a control method of the robot system. FIG. 3 is a front view showing a state in which the transport device starts transporting the workpiece. FIG. 4 is a front view showing a state in which the imaging unit captures an image of the workpiece. FIG. 5 is a top view showing the generated transport path. FIG. 6 is a front view showing a state in which the robot holds the workpiece. FIG. 7 is a top view showing a state in which a positional deviation occurs in the target position. FIG. 8 is a top view showing a corrected transport path. FIG. 9 is a top view showing a transport path corrected by a first correction method. FIG. 10 is a top view showing a transport path corrected by a second correction method. FIG. 11 is a top view showing a transport path corrected by a third correction method. FIG. 12 is a diagram showing an example of a graphic interface.

[0010] 1 includes a robot 2, an imaging unit 3, a control device 4, a transport device 6, and a display device 8. Note that the robot 2, the imaging unit 3, and the transport device 6 have already been calibrated, and their relative positional relationships with each other are already known.

[0011] In the robot system 1, the transport device 6 transports a workpiece W as an object along a transport direction A, the control device 4 detects the transport status of the workpiece W based on the image G acquired by the imaging unit 3 and the transport speed of the workpiece W, and the robot 2 holds the workpiece W while running parallel to (tracking) the workpiece W being transported based on the detected transport status, and transports the held workpiece W to a target position. In this embodiment, the workpiece W is transported in a state housed in a box-shaped case C as shown in Fig. 1. However, this is not limited to this, and for example, the workpiece W may be transported in an exposed state.

[0012] As shown in FIG. 1, the robot 2 is a six-axis vertical articulated robot having six drive shafts, and includes a base 21, a robot arm 22 rotatably connected to the base 21, and an end effector 23 attached to the tip of the robot arm 22. The robot arm 22 is a robotic arm in which a plurality of arms 221, 222, 223, 224, 225, and 226 are rotatably connected, and includes six joints J1 to J6. Among these, the joints J2, J3, and J5 are bending joints, and the joints J1, J4, and J6 are torsion joints. The end effector 23 is appropriately selected depending on the target work. In the illustrated configuration, the end effector 23 is configured to suck and hold the workpiece W by an air chuck.

[0013] In addition, each of the joints J1, J2, J3, J4, J5, and J6 is provided with a motor M and an encoder E that detects the amount of rotation of the motor M. During operation of the robot system 1, the control device 4 executes servo control (feedback control) for each of the joints J1 to J6 such that the rotation angle of the joints J1 to J6 indicated by the output of the encoder E matches a control target.

[0014] The transport device 6 is a belt conveyor, and includes a belt 62, transport rollers 63 that feed the belt 62, a motor 61 that drives the transport rollers 63, and an encoder 64 that outputs a signal according to the amount of rotation of the belt 62 to the control device 4. During operation of the robot system 1, the control device 4 executes servo control (feedback control) to match the transport speed of the workpiece W indicated by the output of the encoder 64 with a target transport speed that is a control target.

[0015] The imaging unit 3 is a camera that captures an image of the workpiece W from above the transport device 6 and outputs the captured image to the control device 4. The imaging area of ​​the imaging unit 3 is located upstream of the work area of ​​the robot 2 in the transport direction A. The position of each pixel in the image output from the imaging unit 3 is associated with a position on the transport path by the control device 4. Therefore, when the workpiece W is present within the angle of view of the imaging unit 3, the coordinates (position) of the workpiece W at the time the image was captured (hereinafter also referred to as the "image acquisition time Ti") can be identified based on the position of the workpiece W in the image of the imaging unit 3.

[0016] The control device 4 controls the driving of the robot 2, the imaging unit 3, and the transport device 6. The control device 4 is, for example, composed of a computer, and has a processor (CPU) for processing information, a memory communicatively connected to the processor, and an external interface for connecting to an external device. Various programs executable by the processor are stored in the memory, and the processor can read and execute the various programs stored in the memory. Some or all of the components of the control device 4 may be disposed inside the housing of the robot 2. The control device 4 may also be composed of multiple processors.

[0017] The configuration of the robot system 1 has been briefly described above. Such a robot system 1 operates as follows. First, the control device 4 operates the transport device 6 and controls the driving of the control device 4 so that the transport speed of the workpiece W detected based on the output of the encoder 64 becomes the target transport speed. In this state, the workpiece W is supplied to the transport device 6, and the transport device 6 starts transporting the workpiece W. Next, the control device 4 captures the workpiece W passing through the imaging area with the imaging unit 3 and acquires an image G in which the workpiece W is captured. Next, the control device 4 detects the coordinates of the workpiece W at the time when the image G was acquired from the image G. Next, the control device 4 calculates the position of the workpiece W at each future time from the coordinates of the workpiece W and the transport speed of the workpiece W at the time when the image G was acquired, and calculates a control signal for the robot 2 based on the calculated position. Then, the control device 4 drives the robot 2 with the calculated control signal and causes the robot 2 to perform a predetermined task on the workpiece W being transported.

[0018] Next, the predetermined work will be described. In this embodiment, the predetermined work includes a holding step of holding (picking) the work W to be transported by the transport device 6, and a transport step of transporting the held work W to the target position Pe. The control method of the robot system 1 when performing such work includes a work transport step S1 of transporting the work W by the transport device 6, a transport start position prediction step S2 of determining a predicted position Ps of starting the transport of the work W to the target position Pe, a transport path generation step S3 of generating a transport path E1 of the work W from the predicted position Ps to the target position Pe, a work holding step S4 of holding the work W, a transport start step S5 of starting the transport of the held work W to the target position Pe, and a correction step S6 of correcting the transport path E1 using the difference between the start position Ps' at which the transport of the work W actually started in the transport start step S5 and the predicted position Ps predicted in the transport start position prediction step S2. Hereinafter, each of these steps S1 to S6 will be described in detail based on the flowchart shown in FIG. 2.

[0019] [Work transport step S1] First, the control device 4 starts driving the transport device 6 and makes the transport speed Vs of the workpiece W indicated by the output of the encoder 64 coincide with the target transport speed. As a result, as shown in Fig. 3, the workpiece W placed on the transport device 6 is transported at the target transport speed. The method of supplying the workpiece W to the transport device 6 is not particularly limited, and can be performed using, for example, a robot, a parts feeder, or the like. The workpiece W may also be supplied manually by an operator.

[0020] [Transport start position prediction step S2] When the conveyance of the workpiece W by the conveyance device 6 starts, the control device 4 captures the workpiece W passing through the imaging area with the imaging unit 3, and acquires an image G in which the workpiece W is captured. Next, the control device 4 determines the position (coordinates) of the workpiece W at the time when the image G was acquired, that is, the image acquisition time Ti, based on the acquired image G. Next, as shown in FIG. 4, the control device 4 determines a predicted position Ps, which is a position at which the conveyance start step S5 is to be started, based on the image acquisition time Ti, the position of the workpiece W at the image acquisition time Ti, the conveyance speed Vs, the time required for the workpiece holding step S4, and the like. The predicted position Ps refers to the position of the robot 2, and more specifically, for example, refers to the position of the TCP (tool center point) set at the tip of the robot arm 22.

[0021] However, the method of calculating the predicted position Ps is not particularly limited. For example, in the above-mentioned method, a preset target conveying speed is used as the conveying speed Vs of the workpiece W, but the present invention is not limited to this. For example, while the workpiece W passes through the imaging area, the control device 4 continuously captures images of the workpiece W at a predetermined frame rate using the imaging unit 3, and obtains multiple images in which the workpiece W is captured. Next, the control device 4 may obtain the position of the workpiece W in each image, and calculate the conveying speed Vs of the workpiece W from the amount of deviation of the workpiece W between the images (the distance traveled by the workpiece W) and the frame rate.

[0022] [Transportation route generation step S3] In the transfer path generation step S3, the control device 4 generates a transfer path E1 for the workpiece W from the predicted position Ps obtained in the transfer start position prediction step S2 to the target position Pe, and sets an operation start time Ts for starting the transfer start step S5, as shown in Fig. 5. The transfer path E1 can be set appropriately based on the state of the workpiece W, the range of motion of the robot 2, the surrounding environment of the robot 2 (presence or absence of obstacles, etc.), etc. In addition, the transfer path E1 is a parameter that specifies the movement direction and movement distance of the robot 2.

[0023] [Work holding step S4] In the workpiece holding step S4, as shown in Fig. 6, the control device 4 controls the driving of the robot 2 to hold the workpiece W being transported on the transport device 6 with the end effector 23. Specifically, the workpiece W is held by performing the steps of: moving the end effector 23 parallel to the workpiece W and positioning it directly above the workpiece W; lowering the end effector 23 to abut against the workpiece W; and suction-holding the workpiece W with the end effector 23. As described above, since the workpiece W is housed in the case C, the end effector 23 continues to move parallel to the workpiece W even after holding the workpiece W. If the parallel movement were to be stopped, the workpiece W would collide with the case C, which could result in damage to the workpiece W, a work error, or the like.

[0024] [Transport start step S5] In the transfer start step S5, the control device 4 first determines whether the operation start time Ts has arrived, and when the operation start time Ts has arrived, starts driving control of the robot 2 so that the workpiece W moves along the transfer path E1 generated in the transfer path generation step S3. However, due to various causes such as variations in the time required for the calculation processing of the control device 4, variations in the time required for communication between each unit, and variations in the transfer speed Vs relative to the target transfer speed, as shown in FIG. 7, the start position Ps' at which this step S5 actually starts may deviate from the predicted position Ps predicted in the transfer start position prediction step S2. In particular, as in this embodiment, in order to avoid contact between the case C and the workpiece W, when the robot 2 is caused to run parallel to the workpiece W and the next operation, i.e., the transfer to the target position Pe of the workpiece W is started, the start position Ps' is likely to deviate from the predicted position Ps.

[0025] When the start position Ps' deviates from the predicted position Ps in this way, the deviation occurs directly at the target position Pe. In other words, the actual transport position Pe' deviates from the target position Pe by the same amount as the deviation of the start position Ps' from the predicted position Ps. Therefore, it is not possible to perform transport work with high accuracy. Therefore, the control device 4 performs a correction step S6 in which the transport path E1 is corrected based on the difference ΔPs (deviation) between the predicted position Ps and the start position Ps' so that the transport position Pe' coincides with the target position Pe.

[0026] [Correction step S6] In the correction step S6, the control device 4 first obtains the start position Ps' at which the transport start step S5 was started. Although the method of obtaining the start position Ps' is not particularly limited, in this embodiment, the start position Ps' is obtained based on the output from the encoder E of each joint J1, J2, J3, J4, J5, and J6 of the robot 2. According to such a method, the start position Ps' can be obtained easily and with high accuracy. Next, the control device 4 generates a correction transport path E2 for moving the workpiece W from the start position Ps' to the predicted position Ps, as shown in FIG. 8. Next, the control device 4 corrects the transport path E1 using the correction transport path E2 by one of the following three methods. In this way, by correcting the transport path E1 using the correction transport path E2, the difference ΔPs between the predicted position Ps and the start position Ps' can be easily canceled.

[0027] -First correction method- In the first correction method, the control device 4 generates a new transport path E3 by combining the transport path E1 and the corrected transport path E2, that is, by adding the transport path E1 and the corrected transport path E2, as shown in FIG. 9. At this time, the robot 2 has already started moving based on the transport path E1. Therefore, the transport path E3 is generated little by little while the robot 2 transports the workpiece W, and the robot 2 updates the transport path E3 every time it receives the generated transport path E3 and transports the workpiece W. This cancels the difference ΔPs between the predicted position Ps and the start position Ps', and the workpiece W can be transported to the target position Pe.

[0028] According to the first correction method, the total moving distance of the workpiece W can be made shorter than the second and third correction methods described below, and the time required for transportation (takt time) can be shortened.

[0029] -Second correction method- In the second correction method, the control device 4, as shown in Fig. 10, transports the workpiece W on the correction transport path E2 before transporting the workpiece W on the transport path E1. That is, the control device 4 performs a correction to add the correction transport path E2 before the transport path E1, and generates a new transport path E3. This cancels the difference ΔPs between the predicted position Ps and the start position Ps', and the workpiece W can be transported to the target position Pe.

[0030] According to such a second correction method, the approach direction to the target position Pe does not change, and appropriate transportation can be performed even when the approach direction to the target position Pe is limited, for example, because the target position is surrounded by walls on three sides. In addition, it becomes easier for the user to predict the route, and it is easier to avoid problems such as contact with an obstacle during transportation in advance.

[0031] -Third correction method- In the third correction method, the control device 4, as shown in Fig. 11, transports the workpiece W along the transport path E1, and then transports the workpiece W along the corrected transport path E2. That is, the control device 4 performs a correction to add the corrected transport path E2 after the transport path E1, and generates a new transport path E3. This cancels the difference ΔPs between the predicted position Ps and the start position Ps', and the workpiece W can be transported to the target position Pe.

[0032] According to the third correction method, the starting direction from the starting position Ps' remains the same as the transport path E1, and appropriate transport can be performed even when the starting direction is restricted, for example, when the object is surrounded by walls on three sides. In addition, it becomes easier to predict the path, and it is easier to avoid problems such as contact with an obstacle during transport.

[0033] After correcting the transport path E1 by one of the above three correction methods, the control device 4 controls the driving of the robot 2 so that the workpiece W is transported along the corrected transport path E3. According to this control method, even if the start position Ps' deviates from the predicted position Ps, the deviation is canceled during transport of the workpiece W, and the workpiece W can be transported to the target position Pe. Therefore, the workpiece W can be transported with excellent accuracy.

[0034] Returning to FIG. 2, in such a correction step S6, the control device 4 first obtains a start position Ps' based on the output from the encoder E of each joint J1, J2, J3, J4, J5, and J6 of the robot 2 in step S61. Next, the control device 4 obtains a difference ΔPs between the predicted position Ps and the start position Ps' in step S62. Next, the control device 4 determines whether to correct the conveying path E1 based on a result of comparing the difference ΔPs with a preset allowable range in step S63. The preset allowable range may be an allowable range set by the user, an allowable range stored in a memory unit or the like of the robot at the time of shipment, an optimal allowable range stored in a memory unit of the robot by machine learning, etc.

[0035] In step S63, when it is determined that the conveying path E1 is not to be corrected, the drive of the robot 2 is controlled so that the workpiece W moves along the conveying path E1 without correcting the conveying path E1. For example, when the difference ΔPs is within the allowable range, the control device 4 controls the drive of the robot 2 in step S64 so that the workpiece W moves along the conveying path E1 without correcting the conveying path E1. In this way, by not correcting the conveying path E1 when the difference ΔPs is within the allowable range, the workpiece W can be quickly conveyed to the target position Pe, and the time required for conveying (takt time) can be shortened.

[0036] On the other hand, when it is determined in step S63 that the transport path E1 is to be corrected, the control device 4 generates a corrective transport path E2 for transporting the workpiece W from the start position Ps' to the predicted position Ps in step S65. For example, when the difference ΔPs is outside the allowable range, the control device 4 generates a corrective transport path E2 for transporting the workpiece W from the start position Ps' to the predicted position Ps in step S65. Next, the control device 4 selects one of the above-mentioned first, second, and third correction methods as a method for correcting the transport path E1 in step S66. The selection method is not particularly limited, but in this embodiment, the user is allowed to select in advance.

[0037] For example, in this embodiment, the display device 8 displays a graphic interface 80 as shown in FIG. 12, and is configured to receive input from the user via the graphic interface 80. The graphic interface 80 displays a field for selecting one of the first correction method, the second correction method, and the third correction method. Therefore, the user can select one of the first correction method, the second correction method, and the third correction method in consideration of the work content, the work environment, and the like. However, this is not limited to this, and the control device 4 may automatically set the method based on the work content, the work environment, and the like. In this way, by configuring the correction method to be selectable, the transport path E1 can be corrected by a method suitable for the situation, so that the transport work of the work W can be performed more reliably.

[0038] When the first correction method is selected, the control device 4 generates a new transport path E3 by combining the transport path E1 and the corrected transport path E2 in step S671. Next, the control device 4 controls the driving of the robot 2 so that the workpiece W moves along the transport path E3 in step S672. In this manner, the workpiece W is transported to the target position Pe. According to this method, even if the start position Ps' deviates from the predicted position Ps, the difference ΔPs between the predicted position Ps and the start position Ps' is canceled, and the workpiece W can be transported to the target position Pe.

[0039] When the second correction method is selected, in step S681, the control device 4 controls the drive of the robot 2 so that the workpiece W moves along the correction transport path E2. Next, in step S682, the control device 4 controls the drive of the robot 2 so that the workpiece W moves along the transport path E1. In this manner, the workpiece W is transported to the target position Pe. According to this method, even if the start position Ps' deviates from the predicted position Ps, the difference ΔPs between the predicted position Ps and the start position Ps' is canceled, and the workpiece W can be transported to the target position Pe.

[0040] When the third correction method is selected, in step S691, the control device 4 controls the driving of the robot 2 so that the workpiece W moves along the transport path E1. Next, in step S692, the control device 4 controls the driving of the robot 2 so that the workpiece W moves along the corrected transport path E2. In this manner, the workpiece W is transported to the target position Pe. According to this method, even if the start position Ps' deviates from the predicted position Ps, the difference ΔPs between the predicted position Ps and the start position Ps' is canceled, and the workpiece W can be transported to the target position Pe.

[0041] The robot system 1 has been described above. As described above, the control method of the robot system 1 is a control method of the robot system 1 that holds the workpiece W as an object to be transported by the transport device 6 and transports the held workpiece W to the target position Pe, and includes a transport start position prediction step S2 for determining a predicted position Ps at which the transport of the workpiece W to the target position Pe is started, a transport path generation step S3 for generating a transport path E1 of the workpiece W from the predicted position Ps to the target position Pe, a transport start step S5 for starting the transport of the held workpiece W to the target position Pe, and a correction step S6 for correcting the transport path E1 using the difference ΔPs between the start position Ps' at which the transport is started and the predicted position Ps. According to this control method, even if the start position Ps' deviates from the predicted position Ps, the deviation is canceled during the transport of the workpiece W, and the workpiece W can be transported to the target position Pe. Therefore, the workpiece W can be transported with excellent accuracy.

[0042] As described above, in the control method of the robot system 1, the correction step S6 is executed based on the result of comparing the difference ΔPs with a preset allowable range. For example, when the difference ΔPs is outside the allowable range, the conveying path E1 is corrected, and when the difference ΔPs is within the allowable range, the conveying path E1 is not corrected. In this way, as a result of comparing the difference ΔPs with the preset allowable range, when the conveying path E1 is corrected, the difference ΔPs between the predicted position Ps and the start position Ps' can be canceled and the workpiece W can be conveyed to the target position Pe, and when the conveying path E1 is not corrected, the workpiece W can be conveyed quickly to the target position Pe, and the time required for conveying (takt time) can be shortened.

[0043] As described above, in the correction step S6, the correction transport path E2 from the start position Ps' to the predicted position Ps is generated, and the transport path E1 is corrected using the correction transport path E2. This makes it possible to easily cancel the difference ΔPs between the predicted position Ps and the start position Ps'.

[0044] As described above, in the correction step S6, the transport path E1 is corrected by combining the transport path E1 and the corrected transport path E2. According to this correction method, the total moving distance of the workpiece W can be shortened compared to the second and third correction methods, and the time required for transport (takt time) can be shortened.

[0045] As described above, in the correction step S6, the conveying path E1 is corrected by adding the corrective conveying path E2 after the conveying path E1. According to this correction method, the start direction from the start position Ps' is the same as the conveying path E1, and appropriate conveying can be performed even when there is a restriction on the start direction, for example, when the conveying path is surrounded by walls on three sides. In addition, it becomes easier to predict the path, and it is easier to avoid problems such as contact with an obstacle during conveying.

[0046] As described above, in the correction step S6, the conveying path E1 is corrected by adding the corrective conveying path E2 before the conveying path E1. According to this correction method, the approach direction to the target position Pe does not change, and appropriate conveying can be performed even when the approach direction to the target position Pe is limited, for example, because the target position is surrounded by walls on three sides. In addition, it becomes easier to predict the path, and it is easier to avoid problems such as contact with an obstacle during conveying.

[0047] As described above, there are multiple methods for correcting the transport path E1, and in the correction step S6, the transport path E1 is corrected using one method selected in advance from the multiple methods. In this way, by configuring the system to be able to select the correction method, the transport path E1 can be corrected using a method suitable for the situation, so that the transport operation of the workpiece W can be performed more reliably.

[0048] As described above, the control device 4 is a control device of the robot system 1 that holds the workpiece W as an object to be transported by the transport device 6 and transports the held workpiece W to the target position Pe, and executes a transport start position prediction step S2 for determining a predicted position Ps at which the transport of the workpiece W to the target position Pe starts, a transport path generation step S3 for generating a transport path E1 of the workpiece W from the predicted position Ps to the target position Pe, a transport start step S5 for starting the transport of the held workpiece W to the target position Pe, and a correction step S6 for correcting the transport path E1 using the difference ΔPs between the start position Ps' at which the transport started and the predicted position Ps. According to such a control device 4, even if the start position Ps' deviates from the predicted position Ps, the deviation is canceled during the transport of the workpiece W, and the workpiece W can be transported to the target position Pe. Therefore, the workpiece W can be transported with excellent accuracy.

[0049] Although the control method and control device for a robot system of the present invention have been described above based on the illustrated embodiment, the present invention is not limited to this, and the configuration of each part can be replaced with any configuration having a similar function. In addition, any other configuration may be added to the present invention. [Explanation of symbols]

[0050] 1...robot system, 2...robot, 21...base, 22...robot arm, 221...arm, 222...arm, 223...arm, 224...arm, 225...arm, 226...arm, 23...end effector, 3...imaging unit, 4...control device, 6...transport device, 61...motor, 62...belt, 63...transport roller, 64...encoder, 8...display device, 80...graphic interface, A...transport direction, C...case, E...encoder, E1...transport path, E2...transport path for correction, E3...transport path, G...image, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6 ...Joint, M...Motor, Pe...Target position, Pe'...Transport position, Ps...Predicted position, Ps'...Start position, S1...Workpiece transport step, S2...Transport start position prediction step, S3...Transport path generation step, S4...Workpiece holding step, S5...Transport start step, S6...Correction step, S61...step, S62...step, S63...step, S64...step, S65...step, S66, S671...step, S672...step, S681...step, S682...step, S691...step, S692...step, Ti...Image acquisition time, Ts...Operation start time, W...Workpiece, ΔPs...Difference

Claims

1. 1. A method for controlling a robot system that holds an object to be transported by a transport device and transports the held object to a target position, comprising: a transfer start position prediction step of determining a predicted position at which transfer of the object to the target position is to be started; a transport path generating step of generating a transport path of the object from the predicted position to the target position; a conveyance start step of starting conveyance of the held object to the target position; and a correction step of correcting the transfer path using a difference between a start position at which the transfer is started and the predicted position.

2. 2. The method for controlling a robot system according to claim 1, wherein the correction step is performed based on a result of comparing the difference with a preset allowable range.

3. 2. The method for controlling a robot system according to claim 1, wherein in the correcting step, a corrected transport path from the start position to the predicted position is generated, and the transport path is corrected using the corrected transport path.

4. 4. The method for controlling a robot system according to claim 3, wherein in the correcting step, the transport path is corrected by combining the transport path and the corrective transport path.

5. 4. The method for controlling a robot system according to claim 3, wherein in the correcting step, the transport path is corrected by adding the corrective transport path after the transport path.

6. 4. The method for controlling a robot system according to claim 3, wherein in the correcting step, the transport path is corrected by adding the corrective transport path before the transport path.

7. A plurality of methods for correcting the transport path are provided, 2. The method for controlling a robot system according to claim 1, wherein in the correcting step, the transport path is corrected using one of a plurality of the correction methods that are preselected.

8. A control device for a robot system that holds an object to be transported by a transport device and transports the held object to a target position, a transfer start position prediction step of determining a predicted position at which transfer of the object to the target position is to be started; a transport path generating step of generating a transport path of the object from the predicted position to the target position; a conveyance start step of starting conveyance of the held object to the target position; and correcting the transport path using a difference between a start position at which the transport is started and the predicted position.

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