Substrate transfer robot

Abstract

To provide a substrate transfer robot using a vertically articulated robot capable of moving an end effector to a correct position.SOLUTION: A substrate transfer robot 100 includes: a vertically articulated robot 102; a camera 104 that images a tool center point (TCP) of an end effector 154; and a robot control device 106. The robot control device includes: a control position calculation unit 158 for calculating control-use coordinates of the TCP; a measured position calculation unit 160 for calculating actual coordinates of the TCP imaged by the camera; a deviation amount calculation unit 162 for calculating a deviation amount between the control-use coordinates and the actual coordinates; a pair storage unit 164 that stores a plurality of pairs of the control-use coordinates and the deviation amount; a correction expression derivation unit 168 that derives a correction expression for converting the actual coordinates into the control-use coordinates from the plurality of pairs; and a coordinate correction unit 172 that derives corrected control-use coordinates by applying the correction expression to input actual coordinates.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a substrate transport robot including a vertical articulated robot having a plurality of arms. [Background technology]

[0002] SCARA robots (horizontal articulated robots) are often used as robots to transport substrates. Because SCARA robots often have limited uses, they are generally designed as dedicated machines for each application, achieving high-precision operation.

[0003] However, designing a dedicated machine means that the applications are limited, and manufacturing costs are higher than for standard (general-purpose) vertical articulated robots. Also, if a general-purpose SCARA robot is used, a linear travel device is often required to expand the operating range area, which increases the cost of the equipment. Therefore, taking into consideration the cost and the wide operating range, it is possible to use a general-purpose vertical articulated robot to transport substrates.

[0004] A vertical articulated robot generally has an axis that rotates the entire arm horizontally, and the axis of each joint of the arm rotates vertically. The arm has an electric motor that serves as an actuator provided at each joint. The electric motor is driven by a drive signal to achieve the target movement of the arm. An end effector, such as a hand on which a substrate (workpiece) is placed, is attached to the tip of the arm.

[0005] However, because vertical articulated robots have a very complicated mechanism, there are error factors such as arm deflection and backlash that can cause errors (deviations) between the actual coordinates of the tool center point (TCP), which is the reference position of the end effector, and the controlled coordinates. Therefore, in the application of transferring substrates, vertical articulated robots have a larger operational error than SCARA robots. In transferring substrates, high precision is sometimes required, with the allowable error of the trajectory of the hand part being less than 1 mm, making it difficult to adopt vertical articulated robots.

[0006] Patent Document 1 describes an alignment device for a vertical articulated robot. This alignment device includes an image processing device and a robot control panel. The image processing device inputs an image of a reference member at the robot's hand from a camera, and calculates position data of the reference member at each point. The image processing device also obtains the position of the center of gravity of the image, and sets it as center position data of the reference member as seen from the alignment position, and compares this with known position data where the center of the reference member should be, for example, the center of the screen, to obtain the amount of deviation.

[0007] Furthermore, the image processing device obtains a correction amount for the position and posture of the robot hand from the obtained deviation amount and provides this to the robot control board. The robot control board obtains a shift amount for the position and posture of the robot hand from the correction amount from the image processing device with respect to the reference data, and adds or subtracts this shift amount to or from the reference data to reproduce the alignment.

[0008] Patent Document 2 describes a device (TCP deviation detection device) that detects deviation in the tool center position of a vertical articulated robot. This TCP deviation detection device uses an imaging device consisting of a stereo camera to detect deviation in the TCP of a tool when a tool (hand) is attached to a robot that has been calibrated in a robot manufacturing factory and then shipped to, for example, a customer and assembled. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Utility Model Application Publication No. 4-114607 [Patent Document 2] JP 2020-059064 A Summary of the Invention [Problem to be solved by the invention]

[0010] As described above, Patent Documents 1 and 2 disclose a method for correcting the position of a vertical articulated robot using a camera, i.e., calibration. However, since high accuracy is required for substrate transportation, it was necessary to further improve the accuracy of the position correction.

[0011] In view of the above problems, an object of the present invention is to provide a substrate transport robot using a vertical articulated robot capable of moving an end effector to an accurate position. [Means for solving the problem]

[0012] In order to solve the above problems, a representative configuration of a substrate transport robot according to the present invention includes a vertical articulated robot having multiple arms, a camera that photographs the TCP which is the reference position of the end effector attached to the arm, and a robot control device that controls the operation of the vertical articulated robot, and the robot control device is characterized in having a control position calculation unit that calculates the control coordinates of the TCP, an actual position calculation unit that calculates the actual coordinates of the TCP photographed by the camera, a deviation amount calculation unit that calculates the deviation amount which is the difference between the control coordinates and the actual coordinates, a pair memory unit that stores multiple pairs of control coordinates and deviation amounts, a correction equation derivation unit that derives a correction equation that converts the actual coordinates into control coordinates from the multiple pairs, and a coordinate correction unit that derives corrected control coordinates using the derived correction equation for inputted actual coordinates.

[0013] It is preferable that when the movement of the vertical articulated robot is controlled to move it to a predetermined position, the deviation amount calculation unit determines the deviation amount using a camera without moving the vertical articulated robot any further.

[0014] It is preferable that the above-mentioned deviation amount calculation unit controls the operation of the vertical articulated robot to move it to a specified position, then recognizes the TCP using a camera, and if the actual position of the TCP deviates from the controlled specified position, moves the vertical articulated robot so that the TCP reaches the specified position to eliminate the deviation, and calculates the deviation amount by acquiring encoder values ​​before and after the vertical articulated robot moves to eliminate the deviation. Effect of the Invention

[0015] According to the present invention, it is possible to provide a substrate transport robot using a vertical articulated robot capable of moving an end effector to an accurate position. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram illustrating an overall configuration of a substrate transport robot according to an embodiment of the present invention. [Diagram 2] 2A to 2C are diagrams illustrating the operation of the vertical articulated robot of FIG. 1. [Diagram 3] FIG. 3 is a diagram showing the operation of the vertical articulated robot subsequent to FIG. 2. [Figure 4] FIG. 2 is a block diagram showing the functions of the substrate transport robot of FIG. [Diagram 5] 5 is a flowchart showing the operation of the substrate transport robot of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown.

[0018] 1 is a diagram illustrating the overall configuration of a substrate transport robot 100 in an embodiment of the present invention. The substrate transport robot 100 includes a vertical articulated robot 102 having multiple arms 101, a camera 104, a robot control device 106, and an input device 108. The vertical articulated robot 102 is an industrial robot, and is used, for example, when storing substrates (workpieces 110) shown in FIG. 2 in racks 112A and 112B, and when transporting the workpieces 110 from the racks 112A and 112B to a stage 114.

[0019] The vertical articulated robot 102 is, for example, a six-axis robot, and includes a base 116, a first axis 118, a rotating frame 120, a second axis 122, a lower arm 124, a third axis 126, and an upper arm 128. The upper arm 128 has a connecting arm 130, a holding arm 132, and a fourth axis 134, and rotates as a whole about the third axis 126 and the fourth axis 134.

[0020] The base 116 is installed on the floor of a factory, etc. A connector 138 to which the harness is connected is attached to a side surface 136 of the base 116. Note that the connector 138 can also be attached to other side surfaces 140, 142 of the base 116, taking into consideration the direction in which the harness is pulled out.

[0021] When the base 116 is installed on a floor, the first shaft 118 is supported in a direction parallel to the installation surface 144 (hereinafter referred to as the horizontal direction). The swivel frame 120 rotates by the first shaft 118. The second shaft 122 is supported by the swivel frame 120 in a direction perpendicular to the first shaft 118. The lower arm 124 rotates by the second shaft 122. In other words, the rotation direction of the second shaft 122 is the direction in which the angle between the lower arm 124 and the first shaft 118 changes. The third shaft 126 is supported parallel to the second shaft 122 by a tip 146, which is the end of the lower arm 124 opposite to the second shaft 122.

[0022] The connecting arm 130 of the upper arm 128 is rotatably connected to the lower arm 124 via a third shaft 126. The holding arm 132 is connected to the connecting arm 130 via a fourth shaft 134 extending in the longitudinal direction of the holding arm 132 so as to be rotatable about the fourth shaft 134.

[0023] An end effector 154 is attached to the tip 148 of the holding arm 132 via a fifth shaft 150 and a sixth shaft 152. The end effector 154 is a hand on which the workpiece 110 is placed, as shown in Figures 2 and 3. The fifth shaft 150 and the sixth shaft 152 are supported at the tip 148 of the holding arm 132 in a direction perpendicular to the fourth shaft 134. This allows the end effector 154 to maintain a free insertion posture with respect to the workpiece 110 stored in the racks 112A, 112B (see Figure 2).

[0024] In this way, the vertical articulated robot 102 has the first axis 118 arranged horizontally, and the rotating frame 120 rotates in a direction approximately perpendicular to the installation surface 144. This allows the second axis 122 and subsequent axes and arms to perform circular motion in a direction approximately perpendicular to the installation surface 144 by the first axis 118.

[0025] 1. The TCP is the reference position (center position) of the end effector 154 attached to the upper arm 128 of the vertical articulated robot 102. The TCP may recognize the end effector 154 and determine the coordinates of its center position, or a mark such as a protrusion or marker may be provided and recognized on the image. The robot control device 106 controls the operation of the vertical articulated robot 102. The input device 108 is a device for inputting commands, parameters, etc. to the robot control device 106.

[0026] Figure 2 is a diagram showing the operation of the vertical articulated robot 102 in Figure 1. Figure 3 is a diagram showing the operation of the vertical articulated robot 102 subsequent to Figure 2. Here, an operation of transporting the workpiece 110 stored in the rack 112A to the stage 114 in a situation where the layout (arrangement) of the racks 112A, 112B and the stage 114 is narrow will be described.

[0027] 2, the vertical articulated robot 102 moves the lower arm 124 and the upper arm 128 closer to the rack 112A, and further rotates the second axis 122 and the subsequent axes as appropriate. This allows the end effector 154 attached to the upper arm 128 to be inserted under the workpiece 110, and the workpiece 110 to be placed on the end effector 154.

[0028] 3, the swivel frame 120 is rotated in the direction indicated by the arrow B to bring the lower arm 124 and the upper arm 128 closer to the stage 114, and further the second axis 122 and the subsequent axes are rotated as appropriate. This allows the end effector 154 attached to the upper arm 128 to be moved onto the stage 128, and the workpiece 110 to be transported to the stage 114.

[0029] The vertical articulated robot 102 can not only transport the workpiece 110 stored in the rack 112A to the stage 114, but also transport the workpiece 110 from the rack 112B to the stage 114 and transport the workpiece 110 between the racks 112A and 112B.

[0030] Here, when the swivel frame 120 is rotated in the directions of the arrows A and B, the second axis 122 and the subsequent axes and arms are positioned higher than the first axis 118 with respect to the installation surface 144 (here, the floor surface). Therefore, when the end effector 154 is rotated in one of the directions of the arrows A and B, the vicinity of the third axis 126 moves like a pendulum, and the tip 146 of the lower arm 124 does not jump out backward and cause interference. Therefore, there is no risk that the vicinity of the third axis 126 will collide with peripheral equipment such as the racks 112A and 112B and the stage 114. Therefore, according to the vertical articulated robot 102, it is possible to move each arm in a space-saving layout while ensuring a wide operating area.

[0031] Furthermore, in vertical articulated robot 102, only first axis 118 is arranged horizontally, and rotating frame 120 rotates in a substantially vertical direction, so the axes and arms from second axis 122 onwards can use the structure of existing vertical articulated robots as is. Therefore, vertical articulated robot 102 is inexpensive, easy to maintain and easy to manufacture, as parts are standardized to reduce manufacturing costs.

[0032] However, as described above, in the application of substrate transportation, the vertical articulated robot 102 may require high accuracy in the allowable error of the trajectory of the end effector 154. However, in the vertical articulated robot 102, the existence of error factors such as arm deflection and backlash may cause an error (deviation) between the actual coordinates of the TCP of the end effector 154 and the controlled coordinates.

[0033] Therefore, the substrate transport robot 100 employs a configuration that can move the end effector 154 to an accurate position by using a correction formula derived from a pair of deviation amounts between the actual coordinates and the controlled coordinates of the TCP of the end effector 154. This will be specifically described below with reference to Figs. 4 and 5.

[0034] Fig. 4 is a block diagram showing the functions of the substrate transport robot 100 of Fig. 1. Fig. 5 is a flow chart showing the operation of the substrate transport robot 100 of Fig. 4.

[0035] In the substrate transport robot 100, first, the camera 102 photographs the TCP of the end effector 154 (step S100). The camera 102 photographs the TCP of the end effector 154 during a transport operation in which the vertical articulated robot 102 transports the workpieces 110 stored in the racks 112A and 112B to the stage 114, or transports the workpieces 110 between the racks 112A and 112B.

[0036] Next, in step S102, the position detection unit 156 of the robot control device 106 detects the position of each joint of the arm 101 based on the position signal output from the encoder of the arm 101. Furthermore, the control position calculation unit 158 ​​calculates the control coordinates of the TCP of the end effector 154 attached to the arm 101 from the detected position of each joint.

[0037] Next, the actual position calculation unit 160 calculates the actual coordinates of the TCP photographed by the camera 104 (step S104). Furthermore, the deviation amount calculation unit 162 calculates the deviation amount, which is the difference between the control coordinates of the TCP calculated by the control position calculation unit 158 ​​and the actual coordinates of the TCP calculated by the actual position calculation unit 160 (step S106). Note that the actual position calculation unit 160 is incorporated in the robot control device 106 as an example, but is not limited to this and may be disposed outside the robot control device 106. For example, the actual position calculation unit 160 may be implemented as an incorporated unit in the camera 104, or the actual position calculation unit 160 may be implemented in an external device that is not incorporated in the robot control device 106 or the camera 104.

[0038] Next, the pair storage unit 164 stores a plurality of pairs of the coordinates on the control of the TCP and the amount of deviation (step S108). Furthermore, the deviation amount calculation unit 162 determines whether or not the number of pairs stored in the pair storage unit 164 is sufficient (step S110).

[0039] If the number of pairs is not sufficient in step S110 (No), the arm moving unit 166 drives the electric motors provided at each joint of the arm 101 while referring to the positions of each joint of the arm 101 detected by the position detection unit 154 to move the arm 101 and move the end effector 154 to a predetermined position (step S112).

[0040] After step S112, the substrate transport robot 100 repeats the above-mentioned processes from step S100 to step S108 until the number of pairs stored in the pair storage unit 164 becomes sufficient (step S110, Yes). As an example, in step S106, when the arm moving unit 166 moves the end effector 154 to a predetermined position, the deviation amount calculation unit 162 may obtain the deviation amount between the predetermined position under control and the actual position of the TCP by actual measurement using the camera 104 without further moving the arm 101.

[0041] Alternatively, in step S106, the deviation amount may be calculated by a method similar to visual feedback. In this case, the deviation amount calculation unit 162 first attempts to move the end effector 154 to a predetermined position by the arm moving unit 166, and then recognizes the TCP using the camera 104. Next, when the actual position of the TCP deviates from the predetermined position under control, the deviation amount calculation unit 162 moves the arm 101 so that the TCP reaches the predetermined position, thereby eliminating the deviation. Then, the deviation amount calculation unit 162 may calculate the deviation amount by acquiring, from the position detection unit 156, a position signal (encoder value) output from the encoder before and after the movement of the arm 101 that has been moved to eliminate the deviation.

[0042] Next, if the number of pairs is sufficient in step S110 (Yes), the correction formula derivation unit 168 derives a correction formula for converting the actual coordinates of the TCP into the coordinates under control from the multiple pairs of the coordinates under control of the TCP and the amount of deviation (step S114). This correction formula is a linear interpolation formula (first-order equation), and may be derived from multiple pairs created by plotting the "whole" of the work range that the arm 101 can reach in the transport work. Alternatively, the correction formula may be created for each of the racks 112A and 112B. In this case, for example, the origin may be set to the lower left of the rack 112A to create a linear interpolation formula, and the linear interpolation formula may be used in the transport work for the rack 112A.

[0043] Furthermore, the correction equations derived by the correction equation derivation unit 168 for the whole or for each of the racks 112A and 112B are stored in the correction equation storage unit 170. Since the movement of the vertical articulated robot 102 is three-dimensional, a correction equation may be derived for each of the x, y and z axes.

[0044] Next, in step S116, when the real coordinates of the TCP to be the movement destination are input to the input device 108 (Yes), the coordinate correction unit 172 derives corrected control coordinates for the input real coordinates using the correction formula derived in step S114 (step S118). The corrected control coordinates are the control coordinates of the TCP for actually moving the end effector 154 to the real coordinates of the movement destination TCP.

[0045] Next, the arm moving unit 166 operates the arm 101 to move the end effector 154 to the corrected coordinates (step S120), and ends the process. This allows the arm moving unit 166 to move the end effector 154 to the actual coordinates of the destination TCP, i.e., to an accurate position.

[0046] In this way, the substrate transport robot 100 calculates the amount of deviation, which is the difference between the actual coordinates (actual measured values) of the TCP photographed by the camera 104 and the control coordinates (control values) of the TCP, and further stores a plurality of pairs of the control coordinates and the amount of deviation, and derives a correction formula (linear interpolation formula) from these plurality of pairs. Then, when the actual coordinates of the destination TCP are input into the correction formula, the control coordinates of the TCP for actually moving the end effector 154 to the actual coordinates of the destination TCP are output as corrected coordinates.

[0047] Therefore, according to the substrate transport robot 100, the end effector 154 can be moved to an accurate position by using a correction formula derived from a pair of deviation amounts between the actual coordinates of the TCP and the coordinates under control.

[0048] Here, the premise for deriving the correction formula will be described. Three coordinate systems are used in the substrate transport robot 100. The three coordinate systems include a first coordinate system that defines the real TCP coordinates (TCP coordinates instructed from outside) input to the input device 108, a second coordinate system that defines the control TCP coordinates used for calculation in the robot control device 106, and a third coordinate system that defines the TCP coordinates photographed by the camera 104.

[0049] First, the robot control device 106 calculates the actual distance between the camera 104 and the end effector 154, and based on this distance, aligns the origin of the first coordinate system with the origin of the third coordinate system to make the first coordinate system coincide with the third coordinate system. Next, the robot control device 106 obtains the relationship between the second coordinate system and the third coordinate system by a pseudo inverse matrix. This makes it possible to obtain the TCP coordinate of the second coordinate system from the TCP coordinate of the third coordinate system, and furthermore, since the first coordinate system and the third coordinate system coincide with each other, it is possible to obtain the TCP coordinate of the second coordinate system by specifying the TCP coordinate of the first coordinate system. Under such a premise, the robot control device 106 derives a correction formula. Note that the origin and the linear direction of the correction formula depend on the measurement situation such as the robot posture, and are not particularly limited.

[0050] The difference between this and so-called visual feedback control (hereinafter, VFB) is that in VFB, the object opposite the end effector or workpiece is recognized on an image, and the end effector or workpiece is gradually moved toward the object, whereas in the present invention, the amount of movement of the arm is corrected using a correction formula obtained in advance. This makes it possible to operate the vertical articulated robot 102 faster than VFB.

[0051] Furthermore, in the substrate transport robot 100, the camera 104 does not need to be permanently installed on the equipment, but only needs to be installed when the correction formula is calculated. In this way, when multiple substrate transport robots 100 are employed, the camera 104 can be shared, thereby reducing the overall cost.

[0052] Although the preferred embodiment of the present invention has been described above with reference to the attached drawings, it goes without saying that the present invention is not limited to substrate transport applications. The present invention is a versatile vertical articulated structure robot that can also be used for handling and loading applications in narrow layouts. It is clear that a person skilled in the art can think of various modified or altered examples within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Industrial Applicability]

[0053] The present invention can be used as a substrate transport robot including a vertical articulated robot having a plurality of arms. [Explanation of symbols]

[0054] 100...substrate transport robot, 101...arm, 102...vertical articulated robot, 104...camera, 106...robot control device, 108...input device, 110...workpiece, 112A, 112B...rack, 114...stage, 116...base, 118...first axis, 120...rotating frame, 122...second axis, 124...lower arm, 126...third axis, 128...upper arm, 130...connecting arm, 132...holding arm, 134...fourth axis, 1 36, 140, 142...side surface of base, 138...connector, 144...mounting surface, 146...tip of lower arm, 148...tip of holding arm, 150...fifth axis, 152...sixth axis, 154...end effector, 156...position detection unit, 158...control position calculation unit, 160...actual position calculation unit, 162...deviation amount calculation unit, 164...pair storage unit, 166...arm movement unit, 168...correction formula derivation unit, 170...correction formula storage unit, 172...coordinate correction unit

Claims

1. A vertical articulated robot having a plurality of arms; A camera that photographs a TCP that is a reference position of the end effector attached to the arm; A robot control device for controlling the operation of the vertical articulated robot, The robot control device includes: a control position calculation unit for calculating a control coordinate of the TCP; an actual position calculation unit that calculates the actual coordinates of the TCP photographed by the camera; a deviation amount calculation unit that calculates a deviation amount that is a difference between the controlled coordinates and the actual coordinates; a pair storage unit that stores a plurality of pairs of the coordinates under control and the deviation amounts; a correction equation derivation unit that derives a correction equation for converting the real coordinates into the controlled coordinates from a plurality of the pairs; a coordinate correction unit that uses the derived correction formula to derive corrected coordinates under control for the input actual coordinates.

2. The deviation amount calculation unit The substrate transport robot according to claim 1, characterized in that when the operation of the vertical articulated robot is controlled to move it to a predetermined position, the amount of deviation is determined using the camera without causing the vertical articulated robot to move any further.

3. The deviation amount calculation unit After controlling the operation of the vertical articulated robot to move it to a predetermined position, the camera is used to recognize the TCP, and if the actual position of the TCP deviates from a predetermined position under control, the vertical articulated robot is moved so that the TCP reaches the predetermined position, thereby eliminating the deviation; 2. The substrate transport robot according to claim 1, wherein the amount of deviation is determined by acquiring encoder values ​​before and after the vertical articulated robot moves to eliminate the deviation.

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