Robot control method and control device

Abstract

When using a horizontal articulated robot to transport workpieces, the cycle time for workpiece transport is reduced. [Solution] When performing a rotational movement in which the hand 30 is facing a first direction with the arms 21 and 22 folded over, and the hand 30 is rotated to face a second direction, and a lateral movement in which the arms 21 and 22 are driven to move the hand 30 in a direction perpendicular to the second direction, the rotational movement is divided into a first rotational movement with a rotation amount of φ-θ and a second rotational movement with a rotation amount of θ, with the angle between the first direction and the second direction being φ. The movement is then combined with the second rotational movement and the lateral movement as a combined movement, and the first rotational movement and the combined movement are performed in succession.

Description

Technical Field

[0001] The present invention relates to the control of an industrial robot suitable for transporting a workpiece (hereinafter referred to as a robot), and more particularly to a control method and a control device capable of operating a horizontal articulated robot arranged in a narrow space at high speed.

Background Art

[0002] In the manufacture of liquid crystal display panels and organic EL (electroluminescence) display panels, it is necessary to transfer a workpiece, i.e., a glass substrate, between process chambers that perform respective processes via a transfer chamber (transport chamber). Since each process chamber is generally maintained under reduced pressure conditions or vacuum conditions, it is preferable to transfer the workpiece under reduced pressure or vacuum when transferring the workpiece between the process chambers.

[0003] An example of a robot for transfer used for such an object is disclosed in Patent Document 1. The robot described in Patent Document 1 is arranged in a transfer chamber when a plurality of process chambers are arranged so as to surround the transfer chamber. And this robot is a horizontal articulated robot, and includes a base fixed to the floor surface of the transfer chamber, a lifting mechanism that moves up and down with respect to the base, a first arm having one end attached to the lifting mechanism so as to be rotatable in a horizontal plane, a second arm having one end attached to the other end of the first arm so as to be rotatable in a horizontal plane, and a hand capable of holding a workpiece to be transferred. The hand is an elongated member that can hold a workpiece at each of its both ends, and is attached to the other end of the second arm at the central portion in the longitudinal direction so as to be rotatable in a horizontal plane. In this robot, the hand can be swung in a horizontal plane by rotating the first arm with respect to the lifting mechanism or by rotating the hand with respect to the second arm.

[0004] The process chamber is equipped with an inlet / outlet that opens toward the transfer chamber. When loading a workpiece into the process chamber and unloading a workpiece from the process chamber using the robot described in Patent Document 1, the hand is first moved to a position facing the inlet / outlet so that its longitudinal direction is perpendicular to the inlet / outlet. This position is called the access position. By moving the hand positioned at the access position along its longitudinal direction so that the end of the hand enters the process chamber, the workpiece held by the end of the hand can be loaded into the process chamber, and the workpiece inside the process chamber can be unloaded while being held by the end of the hand. The movement of moving the end of the hand from the access position into the process chamber is called the entry movement, and the movement of moving the end of the hand from inside the process chamber back to the access position is called the retreat movement. Both the entry movement and the retreat movement are classified as linear movement movements in which the hand is moved along a certain direction while maintaining the orientation of the hand in a certain direction. When performing the entry movement and retreat movement toward the process chamber, the hand moves along a certain reference line so that the longitudinal centerline of the hand coincides with that line. This straight line is called the access reference line. The access reference line is defined for each process chamber and is a straight line perpendicular to the entrance / exit of that process chamber and passing through the access position of that process chamber. If a movement in which the hand moves along a reference line pointing in a constant direction while keeping the hand's orientation constant is called a linear movement, then both entry and retreat movements are classified as linear movements, and the reference line in such linear movements is the access reference line. When transporting a workpiece between process chambers, the orientation of the access reference line differs for each process chamber, so it is necessary to perform a rotation movement, which is a movement that changes the orientation of the hand within the transfer chamber. If the angle between the access reference lines of the source and destination process chambers is φ, then the rotation angle of the hand during a rotation movement is φ. When transporting a workpiece between process chambers, the robot will perform three movements in succession: a retreat movement in the source process chamber, a rotation movement of the hand, and an entry movement in the destination process chamber.

[0005] Incidentally, when transporting workpieces using a transport robot, multiple movement actions are usually performed sequentially by the robot. Each movement action involves the robot accelerating from its starting point and moving, and then decelerating and stopping at its end point. When transporting workpieces between process chambers using the robot described in Patent Document 1, as mentioned above, three movement actions—reverse movement, rotation movement, and entry movement—are performed sequentially. When two movement actions are performed sequentially, if the robot stops at the end point of the first movement action (i.e., the starting point of the second movement action), the total time required for the two movement actions becomes longer. To shorten the required time, as shown in Patent Document 2, an overlap action can be performed in which the second movement action starts before the first movement action reaches its end point. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-139854 [Patent Document 2] Japanese Patent Publication No. 2022-57452 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] When the horizontal articulated robot described in Patent Document 1 is installed in a transfer chamber and used to transport workpieces between process chambers arranged to surround the transfer chamber, the hand's rotational movement is usually performed with the arm folded and the center of rotation in the rotational movement located on the longitudinal centerline of the hand. If the center of rotation of the hand's rotational movement lies on the access reference line of each process chamber, workpieces can be transported between process chambers by continuously executing a retraction movement, a rotational movement, and an entry movement. However, if, for example, the access reference line of the destination process chamber does not pass through the center of rotation of the hand's rotational movement, it is necessary to rotate the hand so that its longitudinal direction is parallel to the access reference line, and then move the hand laterally while maintaining the orientation of the hand's longitudinal direction so that it aligns with the access reference line of the destination process chamber. This movement is called a lateral movement. However, intervening with such a lateral movement increases the time it takes to complete the transport of the workpiece.

[0008] The object of the present invention is to provide a control method and a control device that can shorten the cycle time of workpiece transport when transporting a workpiece using a horizontal articulated robot. [Means for solving the problem]

[0009] According to one embodiment, the control method controls a robot having a first arm whose one end is rotatable in a horizontal plane around a first axis, a second arm whose one end is connected to the other end of the first arm via a second axis and is rotatable in a horizontal plane around the second axis, and a hand which is connected to the other end of the second arm via a third axis and is rotatable in a horizontal plane around a third axis, wherein the hand is facing a first direction in the horizontal plane with the first arm and the second arm folded over, and the hand is rotated around the third axis to change the orientation of the hand. When performing a rotational movement, which is a movement in a second direction different from the first direction, and a lateral movement, which is a movement in which the first and second arms are driven to move the hand in a direction perpendicular to the second direction, the rotational movement is divided into a first rotational movement in which the hand rotates by an angle of φ-θ, and a second rotational movement in which the hand rotates by an angle of θ, with φ being the angle between the first and second directions and θ being an angle smaller than φ. The movement is then combined by the second rotational movement and the lateral movement as a combined movement, and the first rotational movement and the combined movement are performed in succession.

[0010] According to one embodiment, the control device controls a robot having a first arm whose one end is rotatable in a horizontal plane around a first axis, a second arm whose one end is connected to the other end of the first arm via a second axis and is rotatable in a horizontal plane around the second axis, and a hand which is connected to the other end of the second arm via a third axis and is rotatable in a horizontal plane around the third axis, and comprises a control unit which generates commands including speed for each of the first to third axes in response to an operation command input from an external source, and a drive circuit which drives each of the motors of the first to third axes based on the command including speed, wherein the control unit controls the first arm and the second arm in a folded state When a robot is made to perform a rotational movement, which is a movement where the hand is rotated around a third axis from a state in which the hand is facing a first direction in the horizontal plane to a second direction different from the first direction, and a lateral movement, which is a movement where the first arm and the second arm are driven to move the hand in a direction perpendicular to the second direction, the rotational movement is divided into a first rotational movement in which the hand is rotated by an angle of φ-θ and a second rotational movement in which the hand is rotated by an angle of θ, with φ being the angle between the first direction and the second direction and θ being an angle smaller than φ, and the movement is made to perform a combined movement by combining the second rotational movement and the lateral movement as a combined movement, and the robot is made to perform the first rotational movement and the combined movement in succession. [Effects of the Invention]

[0011] According to the present invention, when transporting a workpiece using a horizontal articulated robot, the cycle time for workpiece transport can be shortened. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows a robot to which one form of control method is applied, where (a) is a top view and (b) is a front view. [Figure 2] This is a plan view illustrating the robot installed inside the transfer chamber. [Figure 3] This is a plan view showing the movement of the arm and hand based on a conventional control method. [Figure 4] This is a plan view showing the movement of the arm and hand based on one form of control method. [Figure 5] This is a plan view showing the trajectory of the hand. [Figure 6] This graph shows the time evolution of a robot's movement. [Figure 7] This figure shows another example of arm and hand movement. [Figure 8] This figure shows another example of arm and hand movement. [Figure 9] This figure shows another example of arm and hand movement. [Modes for carrying out the invention]

[0013] Next, embodiments for carrying out the present invention will be described. Since the present invention relates to robot control, first, a robot to which a control method of one embodiment of the present invention can be applied will be described. Figure 1 shows an example of such a robot, where (a) is a plan view and (b) is a front view.

[0014] The robot 10 shown in Figure 1 is configured as a horizontal articulated robot for transporting plate-shaped workpieces such as glass substrates. It comprises a base 11 fixed to the floor surface where the robot 10 is installed, a lifting mechanism 12 driven by a motor (not shown) that moves up and down relative to the base 11 as indicated by arrows in the figure, a first arm 21 with one end rotatably connected to the upper surface of the lifting mechanism 12 and extending horizontally, a second arm 22 with one end rotatably connected to the other end of the first arm 21 and extending horizontally, and a hand 30 capable of holding the workpiece to be transported. The connection point between the lifting mechanism 12 and the first arm 21 is axis TH1, and by driving the first arm 21 with a motor (not shown), the first arm 21 can rotate in the horizontal plane around axis TH1. Similarly, the connection point between the first arm 21 and the second arm 22 is axis TH2, and by driving the second arm 22 with a motor (not shown), the second arm 22 can rotate in the horizontal plane around axis TH2.

[0015] The hand 30 is an elongated member as a whole, comprising a hand base 31 rotatably connected to the other end of the second arm 22, and four linearly formed hand forks 32. Two of the four hand forks 32 are fixed to the hand base 31 so as to protrude from it in a first projection direction in the horizontal plane, with a predetermined distance between them and in parallel. The remaining two hand forks 32 are fixed to the hand base 31 so as to protrude from it in a second projection direction in the horizontal plane, opposite to the first projection direction. Therefore, the direction in which these hand forks 32 protrude is the longitudinal direction of the hand 30, and the hand base 31 is located in the center of the hand 30 in the longitudinal direction. At both ends of the hand 30, i.e., at the tips of each hand fork 32, a plurality of support members 33 for holding a workpiece are attached to the hand forks 32 so as to extend in a direction perpendicular to the longitudinal direction of the hand 30. In the illustrated example, four support members 33 are provided at the tip of each hand fork 32. Both ends of the hand 30 in the longitudinal direction, i.e., the positions where the support members 33 are provided, are positions on the hand 30 where the workpiece to be transported is placed. The connection point between the second arm 22 and the hand base 31 is axis S, and by driving the hand base 31 with the illustrated motor, the hand 30 can rotate in the horizontal plane around axis S.

[0016] As shown in Fig. 1(b), a control device 40 is connected to the robot 10 to input an operation command for the robot 10 from the outside and drive and control the robot 10 based on this operation command. Specifically, the control device 40 drives and controls the motors of each axis of the robot 10 (that is, the motor that drives the lifting mechanism 12 and the motors that drive those axes provided on each of the axes TH1, TH2, and S), and includes a control unit 41 that receives an operation command from the outside and a drive circuit 42 that includes a servo driver and the like for driving the motors of each axis. Since the robot 10 is used for transporting the workpiece, the operation command includes a command related to the movement operation for moving the hand 30. The control unit 41 generates a command including the speed for each axis of the robot 10 based on the command of the movement operation, and the drive circuit 42 actually drives the motors of each axis of the robot 10 according to the command for each axis. The drive circuit 42 and the robot 10 are electrically connected by a connection cable 43.

[0017] The robot 10 shown in Fig. 1 is installed, for example, in a transfer chamber for transporting workpieces between process chambers. Fig. 2 shows the installation status of the robot 10 in the transfer chamber 50. Here, as shown in the figure, XY coordinates are defined, and it is assumed that the robot 10 is installed such that the axis TH1 is at the center of the transfer chamber 50. The transfer chamber 50 is surrounded by a plurality of process chambers (six process chambers 51A to 51F in the illustrated example). In the example shown here, the transfer chamber 50 has an octagonal shape with the four corners of a rectangle cut off. One of the pair of sides extending in the Y direction of the octagon has the process chamber 51A provided thereon, and the other has the process chamber 51D provided thereon. Also, two process chambers 51B and 51C are provided on one of the pair of sides extending in the X direction, and two process chambers 51E and 51F are provided on the other.

[0018] Each of the process chambers 51A to 51F has a transfer port 52 that opens toward the transfer chamber 50 for loading and unloading the work W. The position facing the transfer port 52 is the access position, and a straight line orthogonal to the transfer port passing through the access position is the access reference line L. After moving the hand 30 of the robot 10 to the access position, the hand fork 32 of the hand 30 is moved toward the transfer port 52 along the access reference line L so that the longitudinal center line of the hand 30 overlaps with the access reference line L, whereby it can enter the interiors of the process chambers 51A to 51F through the transfer port 52. Therefore, the entry operation is a movement operation for entering the interior of the process chamber from the access position by the hand fork 32, and the retreat operation is a movement operation for retreating the hand fork 32 from the interior of the process chamber to the access position. In the example shown in FIG. 2, a pair of hand forks 32 holding the work W have entered the interior of the process chamber 51A.

[0019] Since the transfer chamber 50 is a narrow space, in order to prevent the hand 30, the work W, the arms 21 and 22, etc. from colliding with the wall surface of the transfer chamber 50, the turning operation of the hand 30 is performed in a state where the arms 21 and 22 are folded, that is, a state where the first arm 21 and the second arm 22 are folded over each other. By rotating the hand 30 around the axis S, a turning operation can be performed around the axis S. Further, when the effective length of the first arm 21, that is, the distance between the axis TH1 and the axis TH2, and the effective length of the second arm 22, that is, the distance between the axis TH2 and the axis S, are equal, if the arms 21 and 22 are folded over each other, the axis TH1 and the axis S overlap, so that a turning operation around the axis S can be performed by rotating the first arm 21 around the axis TH1. In the following description, it is assumed that the effective length of the first arm 21 and the effective length of the second arm 22 are equal.

[0020] When the rotational movement of the hand 30 is completed and the longitudinal centerline of the hand 30 coincides with the access reference line L of the process chambers 51A to 51F to be accessed, the entry movement can be performed immediately following the rotational movement. However, when the longitudinal centerline of the hand 30 and the access reference line L are parallel but separated, it is necessary to perform a lateral movement to move the hand 30 so that it coincides with the access reference line L while maintaining the longitudinal orientation of the hand. Below, we consider moving the robot 10 from a state in the transfer chamber 50 shown in Figure 2 where the arms 21 and 22 are folded, the hand 30 is extended in the Y direction, and the workpiece W is placed on the -Y side of the hand 30 and the robot 10 is stopped (this state is called the initial state) to a state where the hand fork 32 holding the workpiece W of the hand 30 is inserted into the process chamber 51B and the robot 10 is stopped (this state is called the final state) in order to transport the workpiece W into the process chamber 51B. Assume that the first arm 21 and the second arm 22 overlap in the initial state. In this case, the workpiece W is held by the hand 30 at the end opposite to the process chamber 51B in the initial state. If the direction of the end of the hand 30 that holds the workpiece W, as viewed from axis S, is defined as the direction of the hand 30, then the direction of the hand 30 differs by 180° between the start state and the end state. That is, a rotation angle of 180° is required for the pivoting motion. Also, since the rotation center of the pivoting motion of the hand 30 is off the access reference line L of the process chamber 51B, moving from the initial state to the end state requires a series of movement operations consisting of a pivoting motion of the hand 30 at a rotation angle of 180°, a lateral movement, and an entry movement into the process chamber 51B. Furthermore, when transporting the workpiece W between process chambers 51A to 51F in the transfer chamber 50 as shown in Figure 2, a rotational movement of the hand 30 is generally required. Therefore, setting the initial state in this way, as the state before the rotational movement begins, is appropriate for explaining the operation of the robot 10.

[0021] Figure 3 shows the movement of the arms 21, 22 and hand 30 of the robot 10 when a series of movement operations are performed from the initial state to the final state using a conventional control method. Figure 3(a) shows the initial state. Here, arms 21 and 22 are folded so that the first arm 21 extends in the -Y direction from axis TH1. The second arm 22 is superimposed on the first arm 21, so the figure shows the second arm 22. First, the hand 30 is rotated 180° from the initial state, but here, the hand 30 is rotated clockwise around the axis S of the robot 10. Figure 3(b) shows the state in the middle of the rotation operation, and Figure 3(c) shows the state after the rotation operation is completed. In the state after the rotation operation is completed, the longitudinal centerline of the hand 30 is parallel to the access reference line L, but they do not overlap. Therefore, the hand 30 is moved laterally so that the longitudinal centerline of the hand 30 coincides with the access reference line L. Lateral movement is a movement operation in which the hand 30 is moved in a direction perpendicular to the longitudinal centerline of the hand 30 while maintaining the orientation of the hand 30 in the horizontal plane. In the example shown in Figure 3, the hand 30 needs to be moved a distance D. During lateral movement, all axes TH1, TH2, and S of the robot 10 are driven. Figure 3(d) shows the state after the lateral movement has finished, and the hand 30 has moved to the access position of the process chamber 51B. Subsequently, an entry operation into the process chamber 51B is performed. During the entry operation, all axes TH1, TH2, and S of the robot 10 are also driven. Figure 3(e) shows the state after the entry operation has finished, i.e., the finished state, indicating that the workpiece W has been loaded into the process chamber 51B. Furthermore, by performing the above operations in the reverse direction, the workpiece W can be removed from the process chamber 51B and the state shown in Figure 3(a) can be returned.

[0022] In the movements of arms 21, 22 and hand 30 shown in Figure 3, the lateral movement is performed independently of the rotation and entry movements, which increases the time until the transport of the workpiece W is completed, i.e., the cycle time. Therefore, when controlling the robot based on the control method of this embodiment, the rotation angle of hand 30 in the rotation movement is made smaller than the specified angle, and instead, a combined movement of the rotation and lateral movement of hand 30 at the remaining rotation angle is performed. That is, the rotation movement at a rotation angle of 180° is decomposed into a first rotation movement and a second rotation movement, the first rotation movement is performed alone first, and then a combined movement, which is a combined movement of the second rotation movement and the lateral movement, is performed. Here, a combined movement means a movement in which the rotation movement and the lateral movement are performed simultaneously. Since hand 30 has moved to the access position of the target process chamber when the combined movement is completed, the entry movement can then be performed as described above. Figure 4 illustrates the movements of the arms 21, 22 and hand 30 when the robot 10 is made to perform such a series of movement actions using one embodiment of the control method.

[0023] Figure 4(a) shows the same initial state as shown in Figure 3(a). From the initial state, a rotation is performed first. In this embodiment, the rotation operation at a rotation angle of 180° is divided into a first rotation operation with a rotation angle of 180°-θ and a second rotation operation with a rotation angle of θ, with the first rotation operation being performed first. If a rotation of 180° is required to align the orientation of the longitudinal centerline of the hand 30 with the orientation of the access reference line L, the angle θ is set to, for example, within the range of 15° to 35°. Preferably, 20°≦θ≦30°. As in the case shown in Figure 3, the hand 30 is rotated clockwise during the rotation operation. Figure 4(b) shows the state in the middle of the first rotation operation, and Figure 4(c) shows the state after the first rotation operation has been completed. In this state, the angle between the longitudinal centerline of the hand 30 and the access reference line L is θ, and a further rotation at angle θ is required. Therefore, a combined operation is performed, which is a combination of a second rotation operation with a rotation angle of θ and a lateral movement operation. Figure 4(d) shows the state during the combined operation, and Figure 4(e) shows the state after the combined operation is completed. The state after the combined operation is exactly the same as the state after the lateral movement operation shown in Figure 3(d), and in this state, the hand 30 has moved to the access position for the process chamber 51B. After that, the workpiece W can be loaded into the process chamber 51B by performing an entry operation in the same way as shown in Figure 3. Figure 4(f) shows the state after the entry operation is completed, i.e., the finished state. In the case shown in Figure 4, the workpiece W can be unloaded from the process chamber 51B and the state shown in Figure 4(a) can be returned by performing the above operation in the reverse direction.

[0024] Figure 5 shows the trajectory of the workpiece W on which the hand 30 is placed, within the XY coordinate system set up as described above in the transfer chamber 50, when the robot 10 is moved from the initial state to the final state. Here, the trajectory of the workpiece W is shown as the trajectory of point A shown in Figures 3(a) and 4(a). Figure 5(a) shows the trajectory obtained by the series of movement operations shown in Figure 3, and Figure 5(b) shows the trajectory obtained by the series of movement operations shown in Figure 4. In Figure 5(a), point P11 corresponds to the state shown in Figure 3(a), point P12 corresponds to the state shown in Figure 3(c), and the arc between points P11 and P12 shows the trajectory when the hand 30 is rotated 180°. Point P13 corresponds to the state shown in Figure 3(d), and the short line segment between points P12 and P13 shows the trajectory during lateral movement. Point P14 corresponds to the state shown in Figure 3(e), and the long line segment between points P13 and P14 shows the trajectory during the approach motion. Meanwhile, in Figure 5(b), point P21 corresponds to the state shown in Figure 4(a), and point P22 corresponds to the state shown in Figure 4(c). The arc between points P21 and P22 shows the trajectory when hand 30 is rotated by an angle of 180°-θ. Point P23 corresponds to the state shown in Figure 4(e), and the short line between points P22 and P23 shows the trajectory during the combined motion. Point P24 corresponds to the state shown in Figure 4(f), and the long line segment between points P23 and P24 shows the trajectory during the approach motion.

[0025] Comparing Figure 5(a) and Figure 5(b), in Figure 5(a), the hand 30, which has been moving in the +X direction, reverses its direction of movement to the -X direction at point P12. This can cause a sudden change in the speed of the hand 30 or induce vibrations near point P12, potentially leading to the workpiece W falling off the hand 30. In contrast, in Figure 5(b), the direction of movement of the hand 30 does not change in a manner that is close to a reversal, thus suppressing sudden changes in speed and vibrations in the hand 30. Furthermore, the length of the trajectory of the hand 30 is shorter in the combined motion than in the lateral movement motion performed alone, and the rotation angle in the rotation motion is also small, so the total length of the trajectory in Figure 5(b) is shorter than the total length of the trajectory in Figure 5(a).

[0026] Figure 6 is a graph showing the elapsed time and change in velocity during a series of movements when the robot moves from the initial state to the final state. Here, the horizontal axis represents elapsed time and the vertical axis represents the velocity of the robot 10, and the velocity is displayed separately for the turning motion, lateral movement motion, and approach motion. Points P11~P14 and P21~P24 in Figure 6 indicate at what point the robot 10 reaches points P11~P14 and P21~P24 shown in Figure 5. Figure 6(a) shows the relationship between elapsed time and velocity in the series of movements shown in Figure 3, and Figure 6(b) shows the relationship between elapsed time and velocity in the series of movements shown in Figure 4. As shown in Figure 6(a), in the series of movements shown in Figure 3, a turning motion is performed first. In the turning motion, the robot 10 accelerates from point P11, then moves at a constant speed, and finally decelerates and stops at point P12. Subsequently, the lateral movement motion starts from point P12. The lateral movement, due to its short distance, does not have a constant speed section and consists of an acceleration section and a current speed section, ending at point P13. Subsequently, the entry movement begins at point P13 and ends at point P14. The entry movement consists of an acceleration section, a constant speed section, and a deceleration section.

[0027] In contrast, as shown in Figure 6(b), in the series of movement movements shown in Figure 4, the turning motion is divided into a first turning motion and a second turning motion, with the first turning motion starting at point P21. The first turning motion consists of an acceleration section, a constant speed section, and a deceleration section, and ends at point P22. Subsequently, a combined motion, which is a combination of the second turning motion and the lateral movement motion, starts at point P22. Since the rotation angle θ of the second turning motion is also small, the combined motion consists of an acceleration section and a deceleration section without a constant speed section, and ends at point P23. Then, an approach motion similar to that shown in Figure 6(a) starts from point P23 and ends at point P24. As can be seen by comparing Figure 6(a) and Figure 6(b), by dividing the turning motion into a first turning motion and a second turning motion, and combining the second turning motion and the lateral movement motion to execute a combined motion, the time from the initial state to the final state can be shortened.

[0028] If a turning motion is divided into a first turning motion and a second turning motion, and the second turning motion is combined with a lateral movement motion to form a combined motion, the time from the initial state to the final state can be further shortened by overlapping the first turning motion with the combined motion, and overlapping the combined motion with the entry motion. Figure 6(c) shows the relationship between elapsed time and velocity in the series of movement motions shown in Figure 4 when overlapping motions are performed. The ratio of the amount of motion (i.e., amount of movement) in the combined motion to the amount of movement during the period that overlaps with the movement motion (first turning motion or entry motion) is called the overlap rate. In the example shown in Figure 6(c), the overlap rate is about 20%. This overlap rate can also be increased. When the overlap rate is increased, the execution time of the combined motion can be increased, and the acceleration and deceleration in the combined motion can be reduced accordingly. Figure 6(d) shows an example where the overlap rate of the combined motion with respect to the first turning motion is 100%, and the overlap rate of the combined motion with respect to the entry motion is also 100%. The combined motion begins when the first turning motion starts to decelerate and ends when the entry motion finishes accelerating. Comparing Figure 6(c) and Figure 6(d), in Figure 6(d), where the overlap rate is 100%, the acceleration and deceleration times in the combined motion are longer, and the acceleration and deceleration are smaller compared to Figure 6(c).

[0029] Here, we will explain the control of the robot 10 in a combined motion, which is a combination of the second rotational motion and the lateral movement motion. The rotational motion of the robot 10 is a motion in which the hand 30 rotates around axis S by folding the arms 21 and 22 so that axis S and axis TH1 are coaxial, and then rotating at least one of axis S and axis TH1. Therefore, it is easy to control the rotational motion in response to an external motion command. The lateral movement is a motion in which axis TH1 and axis S are rotated in the same direction and by the same amount of rotation, while axis TH2 is rotated in the opposite direction to axis TH1 by twice the amount of rotation of axis TH1. Therefore, it is easy to control this motion in response to an external motion command. However, it is not possible to simply control the combined motion based on motion commands. Several methods can be considered for controlling the combined motion.

[0030] One control method that can be used for composite motion is point-to-point (PTP) control. PTP motion generally involves specifying only the start and end points of the trajectory that the tip of a tool or hand attached to a robot should take, thereby moving the tool or hand quickly to the end point. In this embodiment, when using PTP motion, the position and orientation of the hand 30 when the first rotation motion is completed, and the position and orientation of the hand 30 when the approach motion starts (i.e., the access position and the orientation of the hand 30 at that position) are specified. The movement path of the robot 10 during composite motion is not specified, and once the amount of movement for each axis between the start and end points of the composite motion is determined, each axis is driven independently according to that amount of movement for each axis. Since the intermediate path is not specified, there is a possibility that the hand 30 may come too close to the wall of the transfer chamber 50, so PTP control is used when there is sufficient distance between the arms 21, 22, the hand 30, the workpiece W and the transfer chamber 50.

[0031] Interpolation (also called CP (continuous path) operation) is a control method that allows specifying the movement path of the robot 10 when performing composite operation. When performing interpolation, there are three methods for interpolating the movement path in composite operation: linear interpolation, circular arc interpolation, and elliptical arc interpolation. Linear interpolation requires relatively little computation to move the robot 10 along the path, but there is a risk that the hand 30 may approach the wall of the transfer chamber 50, although not as much as in PTP operation. When interpolating with a circular arc, for example, the end of the hand 30 that is holding the workpiece W is controlled to move along an arc of a circle centered on the end of the hand 30 that is not holding the workpiece W. However, even when interpolating with a circular arc, there is a risk that the hand 30 may approach the wall of the transfer chamber 50. If the approach of the hand 30 to the transfer chamber 50 is suppressed, elliptical arc interpolation can be used. Elliptical arc interpolation can be achieved by increasing the radius of the circular arc interpolation as the composite operation progresses, while moving the center of the circle away from the process chamber 51B. Interpolation using circular or elliptical arcs allows for smoother movement of the hand 30 compared to interpolation using straight lines.

[0032] Figure 7 shows another example of the movement of arms 21, 22 and hand 30 in this embodiment. The example shown in Figure 7 is similar to the example shown in Figure 4, but differs from the example shown in Figure 4 in that, in the initial state, arms 21 and 22 are folded so that the first arm 21 extends in the +Y direction from axis TH1. Because the direction of the first arm 21 in the initial state is different, the movement of the first arm 21 and the second arm 22 is different from that shown in Figure 4, but the principle of the series of movement operations itself is the same. Figure 7(a) shows the initial state, Figure 7(b) shows the state in the middle of the first rotation operation, Figure 7(c) shows the state after the first rotation operation is completed, Figure 7(d) shows the state in the middle of the combined operation, Figure 7(e) shows the state after the combined operation is completed, and Figure 7(f) shows the final state.

[0033] In the examples shown in Figures 4 and 7, the hand 30 is rotated by rotating the axis S, but the hand 30 can also be rotated by rotating the axis TH1 instead of axis S. Figure 8 shows another example of the movement of the arms 21, 22 and the hand 30 in this embodiment. The example shown in Figure 8 is similar to the examples shown in Figures 4 and 7, but differs from those shown in Figures 4 and 7 in that the hand 30 is rotated by rotating the axis TH1. Because the axis TH1 is rotated, the hand 30 and the arms 21 and 22 overlap during the rotational movement. Figure 8(a) shows the initial state, Figure 8(b) shows the state in the middle of the first rotational movement, Figure 8(c) shows the state after the first rotational movement is completed, Figure 8(d) shows the state in the middle of the combined movement, Figure 8(e) shows the state after the combined movement is completed, and Figure 8(f) shows the final state.

[0034] In the examples shown in Figures 4 and 7, the hand 30 is rotated by rotating the axis S, but the hand 30 can also be rotated by rotating both axis S and axis TH1 simultaneously. Figure 9 shows another example of the movement of the arms 21, 22 and the hand 30 in this embodiment. The example shown in Figure 9 is similar to the examples shown in Figures 4 and 7, but differs from those shown in Figures 4 and 7 in that the hand 30 is rotated by rotating both axis S and axis TH1 simultaneously. Figure 9(a) shows the initial state, Figure 9(b) shows the state in the middle of the first rotation movement, Figure 9(c) shows the state after the first rotation movement is completed, Figure 9(d) shows the state in the middle of the combined movement, Figure 9(e) shows the state after the combined movement is completed, and Figure 9(f) shows the final state.

[0035] According to the control method of this embodiment described above, the rotational movement of the hand is divided into a first rotational movement and a second rotational movement, and the lateral movement that occurs when the workpiece is transported by the horizontal articulated robot and the second rotational movement are combined and executed as a combined movement. As a result, the second rotational movement and the lateral movement are executed in parallel, the time required for workpiece transport can be shortened. Furthermore, vibrations in the hand can also be suppressed.

[0036] The control of the robot 10 in this embodiment has been described above. The control described above is achieved when the control unit 41 analyzes the operation command input from the outside in the control device and generates a command including the speed for each axis of the robot 10, and the drive circuit 42 actually drives the motor of each axis of the robot 10 according to the command for each axis. In the above description, it was assumed that the rotation angle φ in the turning operation is 180°, but the rotation angle φ in the turning operation is not limited to 180 degrees and may be other angle values.

[0037] The above describes an example of a configuration for carrying out the present invention, but the above technology can take the following configuration.

[0038] (1) A robot control method comprising: a first arm whose one end is rotatable in a horizontal plane around a first axis; a second arm whose one end is connected to the other end of the first arm via a second axis and is rotatable in a horizontal plane around the second axis; and a hand connected to the other end of the second arm via a third axis and is rotatable in a horizontal plane around the third axis, When performing a rotational movement, which is a movement that rotates the hand around the third axis to change the orientation of the hand to a second direction different from the first direction, while the hand is facing a first direction in the horizontal plane with the first arm and the second arm folded over, and when performing a lateral movement, which is a movement that drives the first arm and the second arm to move the hand in a direction perpendicular to the second direction, Let φ be the angle between the first direction and the second direction, and let θ be an angle smaller than φ. The rotational movement is divided into a first rotational movement in which the hand rotates by an angle of φ-θ, and a second rotational movement in which the hand rotates by an angle of θ. A control method in which a movement motion obtained by combining the second rotation motion and the lateral movement motion is treated as a combined motion, and the first rotation motion and the combined motion are executed in succession.

[0039] (2) The control method according to (1), wherein the hand is moved in a point-to-point manner between the start and end points of the composite operation.

[0040] (3) The control method according to (1), wherein the hand is moved between the start and end points of the composite operation by an arc interpolation operation or an elliptic arc interpolation operation.

[0041] (4) The control method according to (1), wherein the hand is moved by linear interpolation between the start and end points of the composite operation.

[0042] (5) The control method according to any one of (1)-(4), wherein when the first turning motion and the combined motion are performed in succession, an overlap motion is performed in which the execution of the subsequent motion is started before the completion of the preceding motion.

[0043] (6) The control method according to any one of (1)-(5), wherein a linear movement motion, which is a movement motion in which the hand moves along the second direction while facing the second direction, is performed in succession with the composite motion.

[0044] (7) The control method according to (6), wherein when the combined motion and the linear motion are performed in succession, an overlap motion is performed in which the execution of the subsequent motion is started before the completion of the preceding motion.

[0045] (8) The control method according to (6), wherein when the first turning motion and the combined motion are performed in succession, and the combined motion and the linear motion are performed in succession, an overlap motion is performed in which the execution of the subsequent motion is started before the completion of the preceding motion, and the ratio of the amount of movement of the robot in the combined motion during the execution of the overlap motion to the amount of movement of the robot in the combined motion is 100%.

[0046] (9) A control device for controlling a robot having a first arm, one end of which is rotatable in a horizontal plane around a first axis; a second arm, one end of which is connected to the other end of the first arm via a second axis and rotatable in a horizontal plane around the second axis; and a hand, the other end of the second arm via a third axis and rotatable in a horizontal plane around the third axis, A control unit that generates commands including speed for each of the first to third axes in response to an operation command input from an external source, A drive circuit that drives each of the motors of the first to third axes based on a command including the speed, Equipped with, When the control unit causes the robot to perform a rotational movement, which is a movement operation in which the hand is facing a first direction in the horizontal plane with the first arm and the second arm folded together, and rotates the hand around the third axis to change the orientation of the hand to a second direction different from the first direction, and a lateral movement operation, which is a movement operation in which the first arm and the second arm are driven to move the hand in a direction perpendicular to the second direction, Let φ be the angle between the first direction and the second direction, and let θ be an angle smaller than φ. The rotational movement is divided into a first rotational movement in which the hand rotates by an angle of φ-θ, and a second rotational movement in which the hand rotates by an angle of θ. A control device that causes the robot to perform the first rotational movement and the combined movement in succession, with the combined movement being a combined movement obtained by combining the second rotational movement and the lateral movement.

[0047] According to the configuration described in (1), the rotational movement of the hand is divided into a first rotational movement and a second rotational movement, and the lateral movement and the second rotational movement are combined and executed as a combined movement, so that the second rotational movement and the lateral movement are executed in parallel, the time required for the robot to move can be shortened.

[0048] According to the configuration shown in (2), the robot can be moved quickly between the start and end points of the composite motion by applying PTP motion. According to the configuration shown in (3), the robot can be moved smoothly while specifying a path between the start and end points of the composite motion by using circular or elliptic interpolation. According to the configuration shown in (4), the amount of computation can be reduced when moving the robot by specifying a path between the start and end points of the composite motion.

[0049] According to the configuration shown in (5), the first rotational movement and the combined movement are overlapped, further reducing the time required for the robot to move. According to the configuration shown in (6), the total time required for the robot to move, including the linear movement which is the actual loading and unloading of the workpiece from the access position to the process chamber, can be reduced. According to the configuration shown in (7), the combined movement and the linear movement are overlapped, further reducing the time required for the robot to move. According to the configuration shown in (8), the combined movement is completely overlapped with other movement movements, further reducing the time required for the robot to move, and also reducing the acceleration and deceleration in the combined movement, which further suppresses the generation of vibrations in the hand.

[0050] According to the configuration shown in (9), the rotational movement of the hand is divided into a first rotational movement and a second rotational movement, and the lateral movement and the second rotational movement are combined to form a combined movement. This allows for control that executes the first rotational movement and the combined movement consecutively, thus providing a control device that can shorten the time required for the robot to move. [Explanation of Symbols]

[0051] 10...Robot, 11...Base, 12...Lifting mechanism, 21...First arm, 22...Second arm, 30...Hand, 31...Hand base, 32...Hand fork, 33...Support member, 40...Control device, 41...Calculation unit, 42...Drive circuit, 43...Connecting cable, 50...Transfer chamber, 51A~51F...Process chamber, 52...Inlet / Outlet, L...Access reference line, W...Workpiece.

Claims

1. A control method for controlling a robot having a first arm, one end of which is rotatable in a horizontal plane around a first axis; a second arm, one end of which is connected to the other end of the first arm via a second axis and is rotatable in a horizontal plane around the second axis; and a hand, the other end of the second arm via a third axis and is rotatable in a horizontal plane around the third axis. When performing a rotational movement, which is a movement operation in which the hand is facing a first direction in the horizontal plane with the first arm and the second arm folded over, and the hand is rotated around the third axis to change the orientation of the hand to a second direction different from the first direction, and when performing a lateral movement, which is a movement operation in which the first arm and the second arm are driven to move the hand in a direction perpendicular to the second direction, Let φ be the angle between the first direction and the second direction, and let θ be an angle smaller than φ. The rotational movement is divided into a first rotational movement in which the hand rotates by an angle of φ - θ, and a second rotational movement in which the hand rotates by an angle of θ. A control method in which the first rotational movement and the combined movement are executed in succession, with the combined movement being a combined movement obtained by combining the second rotational movement and the lateral movement.

2. The control method according to claim 1, wherein the hand is moved in a point-to-point motion between the start and end points of the composite motion.

3. The control method according to claim 1, wherein the hand is moved between the start and end points of the composite operation by an arc interpolation operation or an elliptic arc interpolation operation.

4. The control method according to claim 1, wherein the hand is moved by linear interpolation between the start point and the end point of the synthesis operation.

5. The control method according to any one of claims 1 to 4, wherein when the first turning motion and the combined motion are executed in succession, an overlap motion is performed in which the execution of the subsequent motion is started before the completion of the preceding motion.

6. The control method according to any one of claims 1 to 4, wherein a linear movement motion, which is a movement motion in which the hand moves along the second direction while facing the second direction, is performed in succession with the composite motion.

7. The control method according to claim 6, wherein when the composite operation and the linear movement operation are performed in succession, an overlap operation is performed in which the execution of the subsequent movement operation is started before the completion of the preceding movement operation.

8. The control method according to claim 6, wherein when the first turning motion and the combined motion are performed consecutively, and the combined motion and the linear motion are performed consecutively, an overlap motion is performed to start the execution of the subsequent motion before the completion of the preceding motion, and the ratio of the amount of movement in the combined motion during the execution of the overlap motion to the amount of movement of the robot in the combined motion is 100%.

9. A control device for controlling a robot having a first arm, one end of which is rotatable in a horizontal plane around a first axis; a second arm, one end of which is connected to the other end of the first arm via a second axis and is rotatable in a horizontal plane around the second axis; and a hand, the other end of the second arm via a third axis and is rotatable in a horizontal plane around the third axis. A control unit that generates commands including the speed for each of the first to third axes in response to an operation command input from an external source, A drive circuit that drives each of the motors of the first to third axes based on a command including the speed, Equipped with, When the control unit causes the robot to perform a rotational movement, which is a movement operation in which the hand is facing a first direction in the horizontal plane with the first arm and the second arm folded together, and rotates the hand around the third axis to change the orientation of the hand to a second direction different from the first direction, and a lateral movement operation, which is a movement operation in which the first arm and the second arm are driven to move the hand in a direction perpendicular to the second direction, Let φ be the angle between the first direction and the second direction, and let θ be an angle smaller than φ. The rotational movement is divided into a first rotational movement in which the hand rotates by an angle of φ - θ, and a second rotational movement in which the hand rotates by an angle of θ. A control device that causes the robot to perform the first rotational movement and the combined movement in succession, with the combined movement being a combined movement obtained by combining the second rotational movement and the lateral movement.

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