JP2003117879A - Wafer carrying robot and wafer carrying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer carrying robot and a wafer carrying method capable of promptly detecting the occurrence of an overloading state regardless a rotating state of a servo motor of the wafer carrying robot. SOLUTION: In this wafer carrying robot 1, a servo motor 11 is drive- controlled by a velocity command outputted from a motor controlling microcontroller 12. An actual torque value measured from a current value passed to the servo motor 11 is compared with a threshold value, thereby determining an overloading state of the servo motor 11. At that time, the motor controlling microcontroller 12 calculates the threshold value by adding a specified value 16 stored in the motor controlling microcontroller 12 to a theoretical torque value calculated on the basis of the outputted velocity command value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer transfer robot and a wafer transfer method for transferring a wafer by controlling a servomotor based on a speed command.

[0002]

2. Description of the Related Art Conventionally, a wafer transfer robot is used in a semiconductor manufacturing apparatus and moves back and forth between various processing apparatuses such as a vacuum chamber and an open cassette for storing wafers.
This is for transferring one or a plurality of wafers. This wafer transfer robot is provided with a servo motor and a motor control microcomputer, and the servo motor is drive-controlled by a speed command output from the microcomputer based on an instruction of the transfer movement amount by the user. And, for example,
The wafer is transferred by a speed command following a speed waveform in which the wafer is transported from a stopped state to a certain speed, travels at a constant speed, and then decelerates to a stop.

Here, in this wafer transfer robot, for example, when the wafer transfer robot collides with an obstacle or the like, and the speed falls far below the speed command, the microcomputer is controlled to approach the speed waveform.
The torque of the servo motor may become abnormally high.
Further progress at such a time may damage the wafer transfer robot or the wafer. Therefore, an overload state in which the torque of the servo motor becomes abnormally large is detected to avoid this problem. For this purpose, the motor control microcomputer feeds back the current passed through the servo motor and calculates the actual torque value of the servo motor based on this signal. When the calculated actual torque value of the servo motor exceeds a predetermined threshold value, it is determined that an overload state due to a collision or the like has occurred, and abnormal processing such as motor stop is performed. .

FIG. 10 shows an example of changes in the actual torque value of the servo motor. Here, a graph shows how the actual torque value 100 changes when the wafer transfer robot accelerates from a stopped state, travels at a constant speed for a certain period of time, and then decelerates and stops. As shown in FIG. 10, since the actual torque value 100 of the servo motor changes greatly, a threshold value 101 that can be used over this entire section is selected, and when the actual torque value 100 exceeds this threshold value 101, an overload condition occurs. It is determined that. This threshold 101 is
It is set so that no matter what state the wafer transfer robot is in, it will not be erroneously detected as an overload state due to some error or vibration.

[0005]

However, as shown in FIG. 10, the actual torque value 100 of the servomotor changes greatly, especially when the traveling state of the wafer transfer robot is accelerated.
The waveform also differs depending on whether the speed is constant or decelerated. The actual torque value 100 is the section TA corresponding to the time of acceleration.
Is constant in the section TB corresponding to the constant speed, and is changed to the valley type in the section TC corresponding to the deceleration. Therefore, when the overload state is determined by the threshold value 101, the overload state is not detected in the section TC until a considerably large overload state is reached. For example, as shown by the chain double-dashed line in FIG. 10, even if the actual torque value 100 suddenly increases due to collision with an obstacle near the end of the section TC, that value reaches the threshold value 101. It is judged that it is overloaded for the first time. Therefore, the torque is further increased from the collision until the overload state is detected,
In some cases, there is a problem that the robot may be damaged.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and it is possible to quickly detect the occurrence of an overload state regardless of the rotating state of the servo motor of the wafer transfer robot. An object of the present invention is to provide a wafer transfer robot and a wafer transfer method that enable the above.

[0007]

The invention according to claim 1 made in order to solve this problem, the current value of the servo motor when the wafer is transferred through the rotation of the servo motor by the speed command. In a wafer transfer robot that detects an overload by comparing the actual torque value measured via the threshold value, the threshold value is calculated based on the theoretical torque value calculated from the speed command. Characterize.

According to a second aspect of the present invention, in the wafer transfer robot according to the first aspect, the threshold value is calculated by adding a predetermined value to the theoretical torque value. It is characterized in that the predetermined value is changed depending on whether the rotation state of the motor is acceleration, constant speed, or deceleration.

Further, in the invention according to claim 3, when the wafer is transferred through the rotation of the servo motor according to the speed command, the actual torque value measured through the current value of the servo motor is set as a threshold value. In the wafer transfer method of detecting an overload by comparing with the above, the threshold value is calculated based on a theoretical torque value calculated from the speed command.

The invention according to claim 4 is the wafer transfer method according to claim 3, wherein the threshold value is calculated by adding a predetermined value to the theoretical torque value. It is characterized in that the predetermined value is changed depending on whether the rotation state of the motor is acceleration, constant speed, or deceleration.

According to the wafer transfer robot and the wafer transfer method of the present invention having the above characteristics, the actual torque value is measured from the current value flowing in the servo motor, and the actual torque value is converted into the theoretical torque value calculated from the speed command. The overload is detected by comparing with the threshold value calculated based on the above. Therefore, since the theoretical torque value is calculated each time the speed command is output and the threshold value is calculated based on the theoretical torque value, the threshold value corresponding to the output speed command is used. Even if the actual torque value changes greatly depending on the rotation state of the servo motor of the wafer transfer robot, the difference between the actual torque value and the theoretical torque value is usually within an appropriate range, so it is appropriate. Different thresholds can be used. Therefore, regardless of the rotation state of the servo motor of the wafer transfer robot, it is possible to quickly detect the occurrence of the overload state.

Further, if the threshold value is calculated by adding a predetermined value to the theoretical torque value, the threshold value is changed corresponding to the theoretical torque value. Furthermore, if the predetermined value to be added is changed depending on whether the rotation state of the servo motor is acceleration, constant speed, or deceleration, it is possible to select an appropriate predetermined value corresponding to each state. , A more appropriate threshold can be obtained.

In the wafer transfer robot and the wafer transfer method of the present invention, when a wafer is transferred, it means the time when the whole or a part of the wafer transfer robot moves, regardless of the presence or absence of the wafer.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The wafer transfer robot according to the present embodiment is for transferring one or more wafers in a semiconductor manufacturing process or the like. For example, the wafer transfer robot moves between an open cassette and each processing apparatus. Change. First, an outline of the wafer transfer robot 1 will be described with reference to FIGS. FIG. 2 is a side view of the wafer transfer robot 1, and FIG. 3 is a plan view of the wafer transfer robot 1 with the hand 26 attached.

As shown in FIG. 2, the wafer transfer robot 1
Is a hand part 21 for mounting the hand 26 (see FIG. 3), a slide part 22 for horizontally moving the hand part 21, a turn part 23 for rotating the slide part 22 on a horizontal plane, and a slide part. 22 and the turn portion 23 are configured to include a lift portion 24 that vertically moves. In this embodiment, the wafer transfer method of the present invention is applied to drive the slide portion 22 for description.

The hand 26 attached to the hand section 21 is
It is for holding a wafer (not shown) and has various shapes. Here, FIG. 3 shows an example of a configuration using a substantially U-shaped flat plate. By driving the slide portion 22, the hand portion 21 and the hand 26 are integrally moved in the left-right direction in the drawing, and when taking out a wafer (not shown), as shown by a chain double-dashed line in FIG. It is arranged at a position (hand part 21B, hand 26B) protruding from the main body of the transfer robot 1.

Next, the hand portion 2 is moved by the slide portion 22.
The schematic configuration of the mechanism for moving 1 will be described with reference to FIG. As shown in FIG. 4, a slider 31 slidable along a rail 30 provided on the slide portion 22 is provided.
The belt 32 is fixed by bolts 33. The hand portion 21 is fixed to the slider 31 by a bolt (not shown). Further, the belt 32 is stretched by the pulleys 34 and 35 provided on the slide portion 22, and the pulley 34 has a servo motor (not shown in FIG. 4).
The shaft 36 of the servomotor 11) in FIG.

Therefore, when the servomotor 11 is driven, the shaft 36 rotates and the pulley 32 connected to the shaft 36 moves the belt 32, so that the slider 31 fixed to the belt 32 is moved along the rail 30. To move. As a result, the hand portion 21 fixed to the slider 31 can move horizontally along the rail 30. Further, since the position of the hand portion 21 and the rotation amount of the servo motor 11 have a one-to-one correspondence, the position of the hand portion 21 can be controlled by controlling the rotation amount of the servo motor 11.

Next, a servo system for controlling the rotation amount of the servo motor 11 will be described with reference to the block diagram of FIG. As shown in FIG. 1, the servo motor 11 includes a motor control microcomputer 12 that controls the drive of the servo motor 11.
Are connected via the servo driver 13. The servo driver 13 is for outputting a drive current to the servo motor 11 in accordance with a speed command output from the motor control microcomputer 12 as a pulse train. Further, the servo driver 13 outputs an analog signal corresponding to the current value passed through the servo motor 11 to the motor control microcomputer 12
Output to.

The motor control microcomputer 12 is a speed command program 14A for performing speed control processing of the servo motor 11.
And various programs such as an overload detection program 14B for performing overload detection processing, and various data such as a predetermined value 16 used when executing these programs are stored, and each program is sequentially executed to operate the servomotor 11 It is for drive control. The speed command program 14A, based on the movement amount and the speed parameter instructed by the user,
This is a process executed by the motor control microcomputer 12 to calculate the speed command for each unit time. Further, the overload detection program 14B compares the threshold value calculated from the output speed command with the actual torque value obtained from the current value supplied to the servo motor 11 to detect an overload. Is.

Here, FIG. 5 shows the speed command program 14
An example of the velocity waveform 15 in which the velocity command calculated by A is graphed corresponding to time is shown. The motor control microcomputer 12 executes the speed command program 14A, sequentially calculates the speed commands, and outputs the speed commands to the servo driver 13. The resulting velocity waveform 15 has a change in velocity, for example, as shown in the graph of FIG. 5, in which the vehicle accelerates from a stopped state, moves at a certain speed for a certain period of time, and then decelerates to stop. Further, at this time, the motor control microcomputer 12 also calculates the total moving time, the acceleration time, the constant speed time, the deceleration time, and the like. From these times, as shown in FIG.
During acceleration, section TB during constant speed, and section TC during deceleration. This division corresponds to the rotation state division of the servo motor 11. Further, in the example shown in FIG. 5, in order to hold the wafer stably, the velocity waveform 15 is set so as to avoid a rapid change in acceleration.

Further, three kinds of values are stored as the predetermined value 16, and different values are set depending on whether the time point is acceleration, constant speed, or deceleration determined as described above. used. Motor control microcomputer 12
When executing the overload detection program 14B, as shown in the graph of FIG.
Theoretical torque value 17 based on the speed command value output by 2
The threshold value 18 is calculated by adding the predetermined value 16 to. At that time, the speed command output is a predetermined value 16A during acceleration (section TA), a predetermined value 16B during constant speed (section TB),
The predetermined value 16C is used during deceleration (section TC). Here, the size of each predetermined value 16 is such that predetermined value 16A ≧ predetermined value 16C> predetermined value 16B. This is because during acceleration, the resistance due to friction of the rail 30 and the like vary depending on the situation, and the difference from the theoretical torque value 17 tends to increase.

Next, the drive control processing of the servo motor 11 including the overload detection processing of the wafer transfer robot 1 and executed by the motor control microcomputer 12 will be described with reference to the flow chart shown in FIG. This processing is processing including the speed command program 14A and the overload detection program 14B. First, in S1, the motor control microcomputer 12 executes the speed command program 14A, obtains a speed command value based on a user's instruction, and outputs it to the servo driver 13. Further, the theoretical torque value 17 is calculated based on the output speed command value, the predetermined value 16 is added, and the threshold value 18 is calculated. At that time, the rotation state of the servo motor 11 at that time is determined according to the elapsed time from the start of the process execution, and the corresponding value among the stored three kinds of predetermined values 16 is used.

Next, in S2, the motor control microcomputer 12 outputs the speed command value obtained in S1 to the servo driver 13 as a pulse train. In S3, the servo driver 13 outputs the drive current corresponding to the speed command value input from the motor control microcomputer 12 to the servo motor 11. Then, in S4, the servo driver 13
Outputs an analog signal corresponding to the current value passed through the servomotor 11 to the motor control microcomputer 12.

Next, in S5, the motor control microcomputer 12 calculates the actual torque value of the servomotor 11 based on the input analog signal. Then, in S6,
The actual torque value calculated in S5 and the threshold value 18 obtained in S1
Compare with. If it is determined that the actual torque value is larger than the threshold value 18 (S6: YES), it is determined that the overload state is set, and therefore the abnormality process is performed in S7. As the abnormality processing, for example, it is desirable to display a warning to the user along with movement such as stopping on the spot, temporarily retracting, returning to the home position.

Alternatively, when it is determined that the actual torque value is not larger than the threshold value 18 (S6: NO), it is determined that the overload state is not established. Therefore, it is determined whether or not the pulse for the movement amount designated by the user has been output. If not output (S8: NO), the process returns to S1 and the next speed command is output. Then, when all the pulse outputs are completed (S8: YES), this drive control process is completed.

Next, FIG. 8 shows the actual torque value and threshold value 18 when this drive control process is executed and the wafer transfer robot 1 is moved based on the velocity waveform 15 shown in FIG.
The example of the change of is shown in a graph. Actual torque value 10 in FIG.
0 is the same as the actual torque value 100 shown in FIG. The threshold value 18 is calculated by the drive control process described above, and has a waveform similar in shape to the actual torque value 100. For example, as shown in FIG.
Projected hand 26 near the end of section TC during deceleration
When the wafer transfer robot 1 collides with something, such as when the front end of B contacts the obstacle 27 and stops,
As shown by the chain double-dashed line in FIG. 8, the actual torque value 100 sharply increases. Then, the threshold value 18 is immediately exceeded, so that the overload state is quickly detected and the abnormality processing is performed.

As described in detail above, according to the wafer transfer robot 1 and its wafer transfer method of the present embodiment,
The actual torque value is measured from the current value flowing through the servo motor 11, and the actual torque value is compared with a threshold value 18 calculated based on the theoretical torque value 17 calculated from the speed command to detect an overload. Therefore, the theoretical torque value 17 is calculated every time the speed command is output, and the theoretical torque value 17 is calculated.
Since the threshold value 18 is calculated based on, the threshold value 18 corresponding to the output speed command is used. And
Even if the actual torque value changes greatly depending on the rotation state of the servo motor 11 of the wafer transfer robot 1,
Since the difference between the actual torque value and the theoretical torque value 17 is usually within an appropriate range, an appropriate threshold value 18 can be used.
Therefore, regardless of the rotation state of the servo motor of the wafer transfer robot 1, it is possible to quickly detect the occurrence of the overload state.

Further, the threshold value 18 is the theoretical torque value 17
When calculated by adding the predetermined value 16 to the threshold value 18, the threshold value 18 is changed corresponding to the theoretical torque value 17. Further, if the predetermined value 16 added depending on whether the rotation state of the servo motor 11 is acceleration, constant speed, or deceleration is changed, an appropriate predetermined value 16 is selected according to each state. By doing so, a more appropriate threshold value 18 can be obtained.

Further, in the wafer transfer robot 1 of the present embodiment, the threshold value 18 is not stored as a pattern but is calculated each time a speed command is output. Therefore,
No extra memory is required, and it is possible to easily deal with the case where the movement instruction by the user is changed.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. For example, in the above embodiment, the overload detection process by the wafer transfer method of the present invention is applied to the slide part 22 of the wafer transfer robot 1, but the slide part 2
2, each of the turn portion 23 and the lift portion 24 is independently driven and controlled, so that the present invention can be implemented in addition to the slide portion 22.

[0032]

According to the wafer transfer robot and the wafer transfer method of the present invention, the actual torque value is measured from the current value flowing in the servo motor, and the actual torque value is calculated based on the theoretical torque value calculated from the speed command. Detects overload by comparing with a threshold. Therefore, since the theoretical torque value is calculated each time the speed command is output and the threshold value is calculated based on the theoretical torque value, the threshold value corresponding to the output speed command is used. Even if the actual torque value changes greatly depending on the rotation state of the servo motor of the wafer transfer robot, the difference between the actual torque value and the theoretical torque value is usually within an appropriate range, so it is appropriate. Different thresholds can be used. Therefore, regardless of the rotation state of the servo motor of the wafer transfer robot, it is possible to quickly detect the occurrence of the overload state.

Further, if the threshold value is calculated by adding a predetermined value to the theoretical torque value, the threshold value is changed corresponding to the theoretical torque value. Furthermore, if the predetermined value to be added is changed depending on whether the rotation state of the servo motor is acceleration, constant speed, or deceleration, it is possible to select an appropriate predetermined value corresponding to each state. , A more appropriate threshold can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a servo system in a wafer transfer robot of the present invention.

FIG. 2 is a side view of the wafer transfer robot of the present invention.

FIG. 3 is a plan view showing a state in which a hand is attached to the wafer transfer robot of the present invention.

FIG. 4 is a diagram showing a schematic configuration of a slide unit of the wafer transfer robot of the present invention.

FIG. 5 is a graph showing an example of a velocity waveform calculated by the wafer transfer robot of the present invention.

FIG. 6 is a graph showing an example of predetermined values stored in the wafer transfer robot of the present invention.

FIG. 7 is a flowchart of drive control processing performed by the wafer transfer robot of the present invention.

FIG. 8 is a graph showing an example of threshold values according to a drive control process performed by the wafer transfer robot of the present invention.

FIG. 9 is a diagram showing an example of movement of the wafer transfer robot of the present invention.

FIG. 10 is a graph showing an example of a threshold value by a drive control process performed by a conventional wafer transfer robot.

[Explanation of symbols]

1 Wafer transfer robot 11 Servo motor 12 Motor control microcomputer 16 predetermined value 17 Theoretical torque value 18 threshold 100 Actual torque value

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akihito Sugino             850, Horinouchi Town, Kasugai City, Aichi Prefecture             Hardy Co., Ltd. Kasugai Office F-term (reference) 3C007 AS05 AS24 BS15 CT04 CT05                       CV03 HS27 HT02 KS28 KS35                       KS37 MS03 MS23                 5F031 CA02 DA01 FA01 FA07 FA09                       FA11 GA47 GA48 GA49 LA08                       LA13                 5H269 AB33 BB12 CC09 EE01 NN07                       PP02 PP03 PP06                 5H301 AA02 BB05 BB14 CC10 DD06                       EE02 GG14 HH20 JJ01 LL01                       LL02 LL08 MM04

Claims (4)

[Claims] 1. When a wafer is transferred through rotation of a servo motor according to a speed command, an actual torque value measured through a current value of the servo motor is compared with a threshold value to prevent an overload. A wafer transfer robot for detecting, wherein the threshold value is calculated based on a theoretical torque value calculated from the speed command. 2. The wafer transfer robot according to claim 1, wherein the threshold value is calculated by adding a predetermined value to the theoretical torque value, and when the rotation state of the servo motor is accelerated. A wafer transfer robot characterized in that the predetermined value is changed depending on whether it is during constant speed or during deceleration. 3. When the wafer is transferred through the rotation of the servo motor according to the speed command, the actual torque value measured through the current value of the servo motor is compared with a threshold value to prevent an overload. A wafer transfer method for detecting, wherein the threshold value is calculated based on a theoretical torque value calculated from the speed command. 4. The wafer transfer method according to claim 3, wherein the threshold value is calculated by adding a predetermined value to the theoretical torque value, and when the rotation state of the servo motor is accelerated. A wafer transfer method characterized in that the predetermined value is changed depending on whether it is during constant speed or during deceleration.