Work transport system and control method thereof

Abstract

To shorten the time required for transporting a workpiece in a workpiece transport system that transports a workpiece between stages by using a robot provided in a working area.SOLUTION: A standby position and an operation switching point are determined for each stage. The operation switching point is a position which is pulled back from a stage position to the working area and at which a hand of a robot or a workpiece is at least partially inside a stage when the hand of the robot is located at the operation switching point. The stand-by position is a position where the robot can turn directly to the stand-by position of another stage without interference by the robot, and at which no interference occurs the robot and the workpiece even when the robot is moved to the operation switching point by PTP operation. For each stage, the robot is moved by the PTP operation between the stand-by position of the stage and the operation switching point, and is moved by linear interpolation operation between the operation switching point and the stage position.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a workpiece transport system equipped with an articulated robot for transporting workpieces such as semiconductor wafers, and a control method thereof. [Background technology]

[0002] For example, in semiconductor manufacturing processes, workpieces such as semiconductor wafers must be transported between cassettes that store the workpieces and workpiece processing devices that perform predetermined processing on the workpieces. This requires the ability to load (carry in) and unload (carry out) workpieces into multiple cassettes or multiple workpiece processing devices. Furthermore, the space within which the transport device can operate, i.e., the work area, is often limited for workpiece transport. Therefore, workpieces are often transported using articulated robots, which have multiple arms rotatably connected to each other and transmit rotational force from a motor or other device to the arms to perform movements such as extension and contraction. In robots, the hand on which the workpiece is placed during transport is attached to the arm at the tip via a rotating shaft. A cassette, for example, stacks and holds workpieces like a shelf and has an opening on its front that faces the work area. Workpieces can be loaded and unloaded by inserting the hand into the cassette through the opening. Similarly, the workpiece processing device also has an opening facing the work area, allowing workpieces to be loaded and unloaded through the opening. A single workpiece transport system is comprised of the cassette in which the workpieces are stored, the workpiece processing device, and the articulated robot. Since cassettes are also used to load and unload workpieces from workpiece processing equipment, they are collectively referred to as stages. To improve throughput in semiconductor manufacturing processes, etc., a workpiece transport system that can transport workpieces between stages at high speed is required.

[0003] Patent Document 1 discloses that a horizontal articulated robot is used, and the robot is driven so that the third rotation axis counting from the hand side is positioned on the axis of access to the stage, and then the hand is moved in and out linearly relative to the stage, thereby loading and unloading workpieces at high speed without using a linear motion mechanism. In a workpiece transport system, it is necessary to prevent the robot's arm or hand from colliding with the wall surfaces that partition the work area when the robot moves between stages, and Patent Document 2 by the present inventor discloses that, in order to easily generate a safe path for the robot, several specified waypoints are set in advance for the robot's posture, and the robot's movement path is determined to pass through the specified waypoints.

[0004] In order to shorten the transport time, it is necessary for the transport robot to move at high speed, and as a technology for increasing the speed of robot movement, Patent Document 3 discloses that when the robot moves linearly, its acceleration section, constant velocity section, and deceleration section are further divided into segments and PTP control is performed for each segment. Patent Document 4 discloses that when generating a trajectory for a robot arm, a group of intermediate teaching points is provided between a start teaching point and a target teaching point, and a trajectory is generated and evaluated based on the group of intermediate teaching points, and this is repeated while displacing the group of intermediate teaching points, and a trajectory is generated that passes through the group of intermediate teaching points that has the best evaluation results.

[0005] There are two types of motion for moving a robot: PTP (point-to-point) motion and linear interpolation motion. Assuming a reference point exists on the robot's arm or hand, PTP motion involves specifying only the start and end points of the trajectory traced by the reference point. When the reference point is moved to the target coordinates, each axis of the robot is simultaneously driven to reach the target coordinates. In this case, the motors of each axis of the robot can be operated at their maximum speeds, allowing for a short time to reach the target coordinates. However, the trajectory of the reference point will not be linear, and the shape of the trajectory is not guaranteed. To prevent interference with walls, it is necessary to increase the number of teaching points and perform PTP motion between adjacent teaching points. In contrast, linear interpolation motion involves interpolating the trajectory of the reference point to make it linear when moving the reference point to the target coordinates. While linear interpolation motion guarantees a straight trajectory, it has the disadvantage of taking longer to reach the target coordinates than PTP motion.

[0006] In the method described in Patent Document 2, a standby / retraction position is set for each stage within the working area at a position on the near side of the front of the stage, and after the hand is moved to the standby / retraction position, the hand is moved straight toward the inside of the stage using linear interpolation. When moving between the standby / retraction position and a specified via point (or origin position), PTP operation is used. In the method described in Patent Document 1, the robot is first driven so that the third rotation axis counting from the hand side positions the hand on the axis of access to the stage. This position corresponds to the standby / retraction position in the method described in Patent Document 2, and the movement of the hand from this position toward the inside of the stage must be linear, so linear interpolation operation is used to ensure the shape of the trajectory. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-119556 [Patent Document 2] Japanese Patent Application Publication No. 2019-84651 [Patent Document 3] Japanese Patent Application Publication No. 2019-166623 [Patent Document 4] Japanese Patent Application Publication No. 2019-135076 Summary of the Invention [Problem to be solved by the invention]

[0008] As shown in Patent Documents 1 and 2, in a workpiece transport system, if a standby / evacuation position is set on the access axis to the stage but outside the stage, the relationship between the standby / evacuation position and the internal stage position for loading and unloading the workpiece is easy to understand, and robot teaching can be easily performed. However, setting the standby / evacuation position in this manner requires a large robot movement amount due to linear interpolation, which is disadvantageous for reducing transport time. Furthermore, while PTP operation can be used to move a robot between the standby / evacuation position of one stage and the standby / evacuation position of another stage, when the robot arm rotates, the arm and hand must pass through a position in which they are somewhat folded (for example, a designated via point in Patent Document 2) to prevent interference between the arm, hand, and even the workpiece being transported with the inner wall of the work area, which increases the robot's movement time.

[0009] The object of the present invention is to provide a work transport system and a control method thereof that can reduce the time required to transport a workpiece compared to when a standby / retreat position is set on the axis of access to the stage but outside the stage. [Means for solving the problem]

[0010] The work transport system of the present invention is a work transport system having a working area, multiple stages arranged adjacent to the working area, and a robot provided in the working area for loading / unloading workpieces onto / from the multiple stages and transporting the workpieces, wherein a standby position and an operation switching point are defined for each stage, and the operation switching point is a position obtained by pulling back from the stage position of the stage toward the working area, where a part of the robot or a part of a workpiece placed on the robot is inside the stage when the robot is at the operation switching point, and the standby position is a position within the working area where the robot can turn directly to the standby position of another stage without interfering with the inner wall of the working area, and where the robot and the workpiece placed on the robot do not interfere with the inner wall of the working area or the inner wall of that stage, even when the robot moves by point-to-point (PTP) operation to the operation switching point of the stage corresponding to the standby position, and the robot moves between the standby position and the operation switching point of that stage by PTP operation, and the robot moves by linear interpolation operation between the operation switching point of that stage and the stage position.

[0011] According to the workpiece transport system of the present invention, a part of the robot or a part of the workpiece is moved to a position inside the stage 20. switching The robot moves between the standby position and the operation switching point using PTP operation. switching Since the robot moves between the point and the stage position by linear interpolation, the distance traveled by the robot's linear interpolation is shorter than in conventional workpiece transport systems, thereby reducing the time required to transport the workpiece. In addition, there is no need to fold the robot's arms when moving between the standby positions of one stage and another, which also reduces the transport time.

[0012] In the workpiece transport system of the present invention, it is preferable that the robot moves between standby positions in a PTP manner. By moving the robot between standby positions in a PTP manner, it is possible to further reduce the transport time.

[0013] In the workpiece transport system of the present invention, the robot is, for example, a horizontal articulated robot including a base, a base-side link rotatably connected to the base, an arm-side link connected to the base-side link, an arm rotatably connected to the arm-side link, and a hand rotatably connected to the arm for holding a workpiece. In this horizontal articulated robot, the base-side link and the arm-side link form a link mechanism that regulates the movement trajectory of the center point of the connecting axis between the arm-side link and the arm so that it follows a predetermined straight line. By applying the present invention to a workpiece transport system including a horizontal articulated robot whose horizontal movement is greater than its vertical movement, it is possible to further shorten the transport time when the robot is turning, thereby significantly reducing the overall transport time.

[0014] The control method of the present invention is a method for controlling a robot in a work transport system having a working area, a plurality of stages arranged adjacent to the working area, and a robot provided in the working area for loading / unloading workpieces onto / from the plurality of stages to transport the workpieces, wherein a standby position and an operation switching point are determined for each stage, and when moving the robot between the standby position for each stage and a stage position of that stage, the robot is moved between the standby position of that stage and the operation switching point using a PTP operation, and the robot is moved between the operation switching point and the stage position of that stage using a linear interpolation operation, the operation switching point is a position obtained by pulling back from the stage position of the stage towards the working area, and is a position where, when the robot is at the operation switching point, part of the robot or part of a workpiece placed on the robot is inside the stage, and the standby position is a position within the working area where the robot can turn directly relative to the standby position of another stage without interfering with the inner wall of the working area, and is a position where the robot and the workpiece placed on the robot do not interfere with the inner wall of the working area or the inner wall of that stage, even when the robot moves by PTP operation to the operation switching point of the stage corresponding to the standby position.

[0015] According to the control method of the present invention, a part of the robot or a part of the workpiece is moved to the stage. Ji'sOperates in a position that is inside switching The robot moves between the standby position and the operation switching point using PTP operation. switching The robot is moved between the point and the stage position by linear interpolation, so the distance traveled by linear interpolation is shorter than with conventional control methods, thereby reducing the time required to transport the workpiece. In addition, there is no need to fold the robot's arms when moving between the standby positions of one stage and another, which also reduces the transport time.

[0016] In the control method of the present invention, it is preferable to move the robot between standby positions by PTP operation, which makes it possible to further reduce the transport time.

[0017] In the control method of the present invention, the robot is, for example, a horizontal articulated robot including a base, a base-side link rotatably connected to the base, an arm-side link connected to the base-side link, an arm rotatably connected to the arm-side link, and a hand rotatably connected to the arm for holding a workpiece. In this horizontal articulated robot, the base-side link and the arm-side link form a link mechanism that regulates the movement trajectory of the center point of the connecting axis between the arm-side link and the arm so that it follows a predetermined straight line. By applying the present invention to control a horizontal articulated robot in a workpiece transport system equipped with a horizontal articulated robot whose horizontal movement is greater than its vertical movement, it is possible to further shorten the transport time when the robot is turning, and significantly reduce the overall transport time. [Effects of the Invention]

[0018] According to the present invention, the time required to transport the workpiece can be reduced compared to when the standby / retraction position is set at a position on the axis of access to the stage but outside the stage. [Brief explanation of the drawings]

[0019] [Figure 1]1 is a schematic plan view showing a workpiece transport system according to an embodiment of the present invention; [Figure 2] FIG. 1 is a schematic cross-sectional view of a horizontal articulated robot. [Figure 3] 1A to 1C are diagrams illustrating a method for controlling a robot according to the present invention. [Figure 4] 10A and 10B are diagrams showing the steps of workpiece transport using a conventional control method. [Figure 5] 1A to 1C are diagrams showing the steps of workpiece transport according to a control method based on the present invention. [Figure 6] FIG. 10 is a diagram showing the positions of the workpiece and the hand over time, comparing the cases where a conventional control method and a control method according to the present invention are implemented; DETAILED DESCRIPTION OF THE INVENTION

[0020] Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a workpiece transport system according to one embodiment of the present invention. This workpiece transport system is composed of a robot 1, which is an articulated robot, arranged in a working area 40, and a plurality of stages 20 arranged adjacent to the working area 40 and on which workpieces 21 are loaded and unloaded. The workpieces 21 are, for example, semiconductor wafers. Here, five stages 20 are provided, but the number of stages 20 is not limited to this. The stage 20 at the top right of the illustration already contains a workpiece 21. The working area 40 is a space in which the robot 1 can move its hands, arms, etc. without interfering with other objects. In the illustrated example, the working area 40 Although the work area is rectangular, 40The shape of the stage 20 is not limited to a rectangle, but may be a polygon with more vertices, a concave polygon, or even a polygon with some curved sides. Each stage 20 has an opening facing the working area 40, and the hand of the robot 1 can enter the inside of the stage 20 through this opening to load and unload the workpiece 21 onto the stage 20, and the articulated robot 1 can transport the workpiece 21 between stages 20 by moving its links, arms, and hands.

[0021] The robot 1 is a three-link horizontally articulated robot similar to that described in Patent Document 2, and includes two hands 7a, 7b that hold a workpiece 21, an arm 6 that rotatably holds the hands 7a, 7b, a link mechanism 3 that rotatably holds an arm joint J1 at the base end of the arm 6 and operates so that the movement trajectory of the arm joint J1 is a straight line substantially parallel to the arrangement direction of the stages 20, and a base 2 on which the base end of the link mechanism 3 is rotatably supported. The link mechanism 3 is located on the base 2 side and includes a base-side link 4 rotatably held on the base 2, and an arm-side link 5 located on the arm 6 side, and both links 4, 5 are rotatably connected to each other by a link joint J2.

[0022] FIG. 2 shows robot 1, a horizontally articulated robot, in more detail, in a vertical cross section with links 4 and 5, arm 6, and hands 7a and 7b extended. Base 2 includes a lifting cylinder 8 that is driven by a lifting motor (not shown) to move up and down. Base-side link 4 is connected to lifting cylinder 8 and rotatably held by a link mechanism motor 8a built into lifting cylinder 8, allowing it to move up and down relative to base 2 as lifting cylinder 8 moves up and down. Base-side link 4 incorporates a base-side pulley 4a, an arm-side pulley 4b, and a belt 4c, with belt 4c running between base-side pulley 4a and arm-side pulley 4b. The diameter ratio between base-side pulley 4a and arm-side pulley 4b is 2:1. The arm-side pulley 4b is connected to the arm-side link 5, and when the base-side link 4 rotates around the rotation center of the base-side pulley 4a, the rotation angle ratio between the base-side pulley 4a and the arm-side pulley 4b, i.e., the rotation angle ratio between the base-side link 4 and the arm-side link 5, is 1:2. Furthermore, the base-side link 4 and the arm-side link 5 are equal in length. As a result, in the link mechanism 3, the movement trajectory of the center point (arm joint J1) of the connecting shaft that rotatably connects the arm-side link 5 and the arm 6 is restricted to a predetermined straight line.

[0023] The arm 6 is connected to the tip of the arm-side link 5 and is rotatably supported by an arm drive motor 51 built into the arm-side link 5. While FIG. 2 illustrates the arm drive motor 51 built into the arm-side link 5 for ease of explanation, the location of the arm drive motor 51 is not limited thereto. For example, the arm drive motor 51 may be built into the arm 6. The hands 7a and 7b are connected to the tip of the arm 6 and are rotatably supported by frame motors 6a and 6b built into the arm 6. The hands 7a and 7b share a common axis as the center of connection to the arm 6, which serves as the rotation center J3 of the hands 7a and 7b. The hand 7a is positioned above the hand 7b. The robot 1 is provided with a robot controller 10 for driving the robot 1 and controlling its operation. A teaching pendant 15 is connected to the robot controller 10 via a cable 16. The teaching pendant 15 is used by an operator when teaching the robot 1.

[0024] An origin position is also determined for the posture of the robot 1. In the robot 1 of this embodiment, the origin position is a state in which the base side link 4, the arm side ring 5, the arm 6, and the hands 7a, 7b are folded so as to overlap each other, and the tips of the hands 7a, 7b are facing upward in FIG.

[0025] In the method described in Patent Document 2, a standby / retraction position for the stage 20 is set at a position in front of the stage 20 in the working area 40, and linear interpolation is performed when moving the hand from the standby / retraction position to the inside of the stage 20. The standby / retraction position is outside the stage 20 and on the access axis for the stage 20. A similar linear interpolation is performed when returning the hand from the inside of the stage 20 to the standby / retraction position. In contrast, in the workpiece transport system of this embodiment, the standby position is a position that is located within the working area 40 but does not necessarily have to be on the access axis for the stage 20. Instead of locating the standby / retraction position on the access axis for the stage 20, a position on the axis where the hand is pulled back a certain distance from the stage 20 toward the working area 40 is set as the operation switching point. The operation switching point is generally located closer to the stage 20 than the standby position in Patent Document 2. Therefore, generally, when the hand is at the operation switching point, part of the hand or the workpiece is inside the stage 20.

[0026] In this embodiment, the "standby position" is the posture position where the arm is pulled back after workpiece acquisition or storage is completed, or the position reached by a command to move the stage 20 to its front position, and which satisfies the following two conditions: Condition 1: Even if the robot 1 is moved by PTP operation from the standby position to the operation switching point of the stage 20, it will not interfere with the inner wall of the working area or the inner wall of the stage. Condition 2: Even if the stage 20 rotates directly relative to the standby position of the other stage 20, the hand and the workpiece carried on the hand do not interfere with the inner wall of the working area 40 or the like.

[0027] In the present invention, a standby position that satisfies the above conditions can be determined in the same manner as the designated via point described in Patent Document 2, for example. When the posture with the hand or arm folded is the origin position of the robot 1, the robot 1 can also move between the origin position and the standby position by PTP operation. In this embodiment, the fixed position of the workpiece 21 is assumed to be determined on the stage 20, and the position where the workpiece mounting portion of the hand of the robot 1 coincides with the fixed position of the workpiece 21 on the stage 20 is referred to as the "stage position." Therefore, "teaching the stage position" means registering the posture where the center of the workpiece mounting portion of the hand coincides with the center position of the workpiece 21 placed on the stage 20 as coordinates. The workpiece 21 is loaded and unloaded at the stage position. While vertical movement, such as scooping up the workpiece 21, is also required to transport the workpiece 21, the present invention aims to shorten the horizontal transport time, so the following description of the vertical movement of the robot 1 is omitted.

[0028] Next, a control method for the workpiece transport system of this embodiment will be described. In this embodiment, direct movement between the standby position of one stage 20 and the standby position of another stage 20 is possible using PTP movement. Since the link mechanism and arms of the robot 1 do not need to be folded, the transport time can be shortened. Furthermore, in this embodiment, the time required to transport the workpiece between the standby position and the stage position is significantly reduced, thereby further reducing the overall transport time. FIG. 3 is a diagram illustrating the control method of this embodiment. In FIG. 3 and subsequent figures, solid arrows indicate movement using PTP movement, and dashed arrows indicate movement using linear interpolation movement. In this embodiment, the hand is moved between the standby position and the operation switching point using PTP movement, which enables the fastest movement, and between the operation switching point and the stage position using linear interpolation movement. The operation switching point is a position through which the hand passes, and is set so that the movement amount, i.e., the distance, of the linear interpolation movement is as short as possible, under the condition that the hand and the workpiece do not interfere with the inner wall of the stage 20, etc. Since this type of operation switching point is set at a position closer to the stage position than the standby / retraction position in the method shown in Patent Document 2, according to this embodiment, the movement distance due to linear interpolation operation is shortened, and the overall movement time of the hand, i.e., the transport time, is shortened. Below, we will explain the operation according to this embodiment while specifically comparing it with the operation according to the conventional control method.

[0029] In the workpiece transport system shown in FIG. 1, consider the case where the upper hand 7a of the robot 1 is used to transport a workpiece 21 stored on the upper right stage 20 to the lower left stage 20. FIG. 4 shows the step-by-step movements of the robot 1 and workpiece 21 using a conventional control method. (a) shows the robot 1 at its origin position. As shown in (b), the robot 1 moves from its origin position to a standby / retract position on the upper right stage 20 using PTP movement. This standby / retract position is on the axis of access to the stage 20. Next, as shown in (c), the hand 7a is moved to the stage position using linear interpolation movement to retrieve the workpiece 21. After retrieving the workpiece 21, the hand 7a is pulled back to the standby / retract position using linear interpolation movement as shown in (d). Thereafter, the robot 1 moves using PTP movement to an intermediate position before rotation, in which the hand 7a is somewhat folded, as shown in (e), so that the hand 7a and workpiece 21 do not interfere with the inner wall of the working area 40 when the arm rotates. Then, the robot 1 rotates using PTP operation and moves to an intermediate position after rotation, where the hand 7a is in a position where it is folded to a certain extent, as shown in (f). The intermediate positions shown in (e) and (f) are, for example, designated waypoints in the control method shown in Patent Document 2. From the intermediate position shown in (f), the robot 1 moves by PTP operation to a standby / retraction position on the lower left stage 20, as shown in (g). Finally, the hand 7a of the robot 1 moves by linear interpolation to the stage position on the lower left stage 20, and stores the workpiece 21 on that stage 20.

[0030] FIG. 5 shows the movements of the robot 1 and the workpiece 21 when the transfer of the workpiece 21 shown in FIG. 4 is performed using the control method of this embodiment. Even with the control method of this embodiment, the robot 1 moves by PTP operation from the origin position shown in (a) to a standby position for the stage 20 at the upper right, as shown in (b). This standby position is not in front of the stage 20, and the hand 7a is in a more folded state than in the case shown in FIG. 5. Then, as shown in (c), the hand 7a moves to the operation switching point by PTP operation, and subsequently moves to the stage position by linear interpolation operation as shown in (d) to acquire the workpiece 21. After acquiring the workpiece 21, the hand 7a returns to the operation switching point by linear interpolation operation as shown in (e), and subsequently returns to the standby position shown in (f) by PTP operation. Next, the robot 1 rotates by PTP operation to the standby position for the stage 20 at the lower left, as shown in (g). The standby position for the stage 20 at the lower left is also not in front of the stage 20, and the hand 7a is also in a folded state. From the standby position shown in (g), the hand 7a moves to the operation switching point by PTP operation as shown in (h), and then moves to the stage position by linear interpolation operation as shown in (i) to store the workpiece 21 on the stage 20. Thereafter, the hand 7a moves to the operation switching point by linear interpolation operation as shown in (j), and returns to the standby position by PTP operation as shown in (k) for the next transfer.

[0031] FIG. 6 compares the movement of the hand 7a and workpiece 21 when the robot 1, which is at the origin position and has the workpiece 21 placed on it, stores the workpiece 21 on the stage 20, using a conventional method (left side of the dashed line) and the method of this embodiment (right side of the dashed line). In the figure, the workpiece 21 is represented by a large circle, and the rotation axis J3, which is the connection center of the hand 7a to the arm 6, is represented by a small circle. The hand 7a itself is represented by a line segment, showing its center line. Time passes sequentially from (a) to (i), which show the origin position. In both control methods, the hand 7a moves from the origin position using PTP operation. In the control method of this embodiment, the hand 7a has already passed the standby position at (c), and at (e), part of the workpiece 21 has already entered the stage 20. At time (f), the conventional control method finally reaches the standby / retract position, whereas the method of this embodiment reaches the operation switching point. Thereafter, in both control methods, the hand 7a moves toward the stage position by linear interpolation, but in the case of this embodiment, the hand 7a reaches the stage position at (h), whereas in the conventional control method, the hand 1 reaches the stage position at (i). Thus, according to the control method of this embodiment, the stage position can be reached earlier, and the transport time can be shortened.

[0032] In the work transport system of this embodiment, the waiting position, operation via point and stage position for each stage 20 may be registered in the robot controller 10, for example, by teaching using the teaching pendant 15, or may be calculated from the shape of the working area 40, the positional relationship of each stage 20 with respect to the working area 40, and the dimensions of the link mechanism 3, arm 6, and hands 7a, 7b in the robot 1, and then registered in the robot controller 40.

[0033] According to the workpiece transport system of the present embodiment described above, an operation via point is set at a position where part of the hand or part of the workpiece is inside the stage 20, the robot is moved by PTP operation between the standby position and the operation switching point, and the robot is moved by linear interpolation operation between the operation via point and the stage position, so the movement distance by linear interpolation operation is shorter than when the robot is operated by a conventional control method, and the time required to transport the workpiece can be shortened. Furthermore, direct movement between the standby position of one stage and the standby position of another stage can be performed by PTP operation, and there is no need to fold the link mechanism or arms of the robot 1, which also shortens the transport time. [Explanation of symbols]

[0034] 1...articulated robot; 2...base; 3...link mechanism; 4...base side link; 5...arm side link; 6...arm; 7a, 7b...hand; 8...lifting tube; 10...robot controller; 15...teaching pendant; 20...stage; 21...work; 40...working area.

Claims

1. A workpiece transport system having a working area, a plurality of stages arranged in contact with the working area, and a robot provided in the working area for loading / unloading a workpiece to / from the plurality of stages and transporting the workpiece, A standby position and an operation switching point are defined for each stage, the operation switching point is a position where the stage is pulled back from a stage position toward the working area, and where a part of the robot or a part of a workpiece placed on the robot is inside the stage when the robot is at the operation switching point; the standby position is a position within the working area where the robot can turn directly relative to a standby position of another stage without interfering with an inner wall of the working area, and where the robot and the workpiece placed on the robot do not interfere with the inner wall of the working area or the inner wall of the stage even when the robot moves by point-to-point operation to the operation switching point of the stage corresponding to the standby position, A workpiece transport system, wherein for each stage, the robot moves in a point-to-point manner between the waiting position and the operation switching point of the stage, and the robot moves in a linear interpolation manner between the operation switching point of the stage and the stage position.

2. 2. The workpiece transport system according to claim 1, wherein the robot moves between the waiting positions in a point-to-point manner.

3. The robot comprises: The base and A base side link rotatably connected to the base; an arm-side link connected to the base-side link; an arm rotatably connected to the arm-side link; a hand rotatably connected to the arm to hold the workpiece; A horizontal articulated robot comprising:

3. The work transport system according to claim 1, wherein the base side link and the arm side link form a link mechanism that regulates a movement trajectory of a center point of a connecting shaft between the arm side link and the arm so that the movement trajectory is a predetermined straight line.

4. A method for controlling a robot in a work transport system having a working area, a plurality of stages arranged in contact with the working area, and a robot provided in the working area for loading / unloading a work to / from the plurality of stages and transporting the work, comprising the steps of: A standby position and an operation switching point are defined for each stage; When moving the robot between the standby position and a stage position of the stage for each stage, the robot is moved between the standby position and the operation switching point of the stage by a point-to-point operation, and the robot is moved between the operation switching point and the stage position of the stage by a linear interpolation operation; the operation switching point is a position of the stage pulled back from the stage position toward the working area, and a part of the robot or a part of the workpiece placed on the robot is inside the stage when the robot is at the operation switching point; The waiting position is a position within the working area where the robot can rotate directly relative to a waiting position of another stage without interfering with the inner wall of the working area, and where the robot and the workpiece placed on the robot do not interfere with the inner wall of the working area or the inner wall of the stage even when the robot moves in a point-to-point operation to the operation switching point of the stage corresponding to the waiting position.

5. The method of claim 4 , further comprising moving the robot between the standby positions in a point-to-point motion.

6. The robot comprises: The base and A base side link rotatably connected to the base; an arm-side link connected to the base-side link; an arm rotatably connected to the arm-side link; a hand rotatably connected to the arm to hold the workpiece; A horizontal articulated robot comprising:

6. The control method according to claim 4, wherein the base side link and the arm side link form a link mechanism that regulates a movement trajectory of a center point of a connecting shaft between the arm side link and the arm so as to be a predetermined straight line.

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