JP5401748B2 - Robot and teaching method thereof - Google Patents

Description

  The present invention relates to a robot capable of teaching a target position and a teaching method thereof.

  Conventionally, a robot having a displaceable arm is used when a workpiece such as a silicon wafer used for manufacturing a semiconductor or a glass substrate used for manufacturing a liquid crystal display panel is transported. This type of robot has a function of teaching a target position in advance in order to accurately convey a workpiece to a predetermined position.

  In recent years, with the increase in size of semiconductor wafers and glass substrates, teaching to robots has become increasingly difficult, and the level of skill required for operators has also increased. Therefore, there is a demand for a technique that can easily cause a teaching error due to an operator's lack of skill and that can teach a robot an accurate position without depending on the skill of the operator.

  Japanese Patent Application Laid-Open No. 2004-228561 describes a method for obtaining a teaching point by detecting the position of a target with a three-axis SCARA robot. In this system, the end effector of the robot is moved toward the target added to the cassette or the like and brought into contact with the target. At this time, changes in torque and speed are detected. Then, by comparing torque and speed changes between when the end effector contacts the target and when it does not, the contact point between the end effector and the target is detected, and the position of the target is obtained from the detected contact point. Calculate the teaching point.

US Pat. No. 6,242,879

  However, in the conventional teaching method described above, when the end effector is brought into contact with the target, the end effector and the target are deformed or particles are generated. In order to prevent such a problem, it is necessary to operate the robot at a very low speed. In this case, however, the position detection accuracy becomes low due to the fluctuation and time-dependent elements of the robot drive system. There is a problem of end. Here, the variable element includes torque fluctuation and friction, and the time-varying element includes hysteresis and the like.

  The present invention has been made in view of the above-described problems, and can detect the position of the target with high accuracy without causing deformation of the end effector and the target and preventing the generation of particles. An object is to provide a robot and a teaching method thereof.

  The robot according to the present invention includes a robot arm having a wrist shaft rotatably provided at a tip, arm driving means for driving the robot arm to displace, wrist axis driving means for rotating the wrist axis, and the arm driving. And robot control means for controlling the wrist axis driving means, the robot control means being attached to the wrist axis by controlling the arm driving means to move the tip portion of the robot arm. The contact member is brought into contact with the teaching target, and the posture of the robot arm and the angular position of the wrist shaft when the wrist shaft starts angular displacement due to contact between the contact member and the teaching target are detected, The teaching point position is determined based on the detection result.

  Preferably, the wrist shaft driving means includes a motor that rotationally drives the wrist shaft, and an encoder provided on the motor, and the robot control means is configured to change the angular displacement of the wrist shaft to a position of the encoder. It is comprised so that it may detect by the change of.

  Preferably, an end effector attached to the wrist shaft is further provided, and the contact member is the end effector.

  Preferably, an end effector attached to the wrist shaft is further provided, and the contact member is a member held by the end effector.

  Preferably, the end effector has a holding means for holding a plate-like member, the contact member is the plate-like member held by the end effector, and the teaching target accommodates the plate-like member. It is a container for doing.

  Preferably, the robot control means substantially sets a control loop gain of the wrist axis driving means at a time when the contact member is expected to contact the teaching target based on a provisional position of the teaching target given in advance. Is configured to be zero.

  Preferably, the robot control means is configured to make the control loop gain substantially zero immediately before the time when the contact member is expected to contact the teaching target.

  Preferably, the robot arm is configured to be displaced and driven with a degree of freedom in the X-axis, Y-axis, and Z-axis directions.

  Preferably, the robot control means is configured to detect a plurality of teaching points existing at different positions.

  Preferably, the wrist shaft is freely rotatable around a rotation axis in the Z-axis direction.

  Preferably, the robot arm is configured to be displaced and driven with a degree of freedom in the X-axis, Y-axis, and Z-axis directions, and the robot control means is configured to move in the Z-axis direction. The contact member is brought into contact with the target at a plurality of different positions in the Z-axis direction with respect to a target whose position in the X-axis direction and the Y-axis direction changes according to the position, and the plurality of different positions The position of the teaching point in the direction of the Z-axis is determined based on the detection result in.

  The present invention is a method for teaching the position of a teaching point to any one of the above robots, wherein the robot control means controls the arm driving means to move the tip of the robot arm, and the wrist axis Contacting the teaching target with the contact member attached to the teaching target, and the posture of the robot arm when the wrist axis starts angular displacement due to contact between the contact member and the teaching target, and the wrist axis Detecting an angular position and determining a position of a teaching point based on the detection result.

The perspective view which showed the robot by one Embodiment of this invention with the wafer cassette. The figure which showed the internal structure of the robot arm of the robot shown in FIG. The block diagram which showed the structure of the control drive system of the robot shown in FIG. The top view for demonstrating teaching operation in the robot shown in FIG. The front view for demonstrating teaching operation in the robot shown in FIG. The top view for demonstrating other teaching operation in the robot shown in FIG. The side view of the target shown in FIG.

  A robot and a teaching method thereof according to an embodiment of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the robot 10 according to the present embodiment includes a robot body 20 that transports a plate-like member (work) such as a semiconductor wafer 50, and robot control means 40 that controls the operation of the robot body 20. ing.

  The robot body 20 can carry out the semiconductor wafer 50 from the wafer cassette 51 or carry the wafer 50 into the cassette 51. Here, the wafer cassette 51 is manufactured based on SEMI (Semiconductor Equipment and Materials International) standard.

  The robot body 20 has a robot base 21, and an arm base shaft 22 extending in the vertical direction, that is, the Z-axis direction is provided on the robot base 21 so as to be movable up and down. The base end portion of the first arm portion 23 is fixed to the upper end of the arm base shaft 22. A proximal end portion of the second arm portion 24 is rotatably attached to the distal end portion of the first arm portion 23.

  A hand 25 as an end effector is rotatably provided at the distal end portion of the second arm portion 24, and the hand 25 is configured such that the semiconductor wafer 50 is placed thereon. The hand 25 includes a holding unit 25A using a vacuum suction mechanism, a gripping mechanism, or the like in order to releasably hold the wafer 50 placed thereon.

  The robot control means 40 is realized by a computer, and executes a storage unit 41 that stores an operation program for controlling the operation of the robot body 20 and an operation program stored in the storage unit 41. And a CPU 42 for controlling the robot body 20.

  The storage unit 41 can also store data related to teaching points for controlling the operation of the robot body 20, and the hand 25 is moved to a predetermined position based on the teaching point data stored in the storage unit 41. It is. The storage unit 41 also stores data related to the shape and dimensions of the hand 25 and data related to the shape and dimensions of the wafer held by the hand 25.

  As shown in FIG. 2, the second arm portion 24 is fixedly attached to a second arm rotating shaft 26 that is rotatably provided at a distal end portion of the first arm portion 23 at a base end portion thereof. Yes. The hand 25 is fixedly attached to a wrist shaft 27 rotatably provided at the distal end portion of the second arm 24 at the base end portion.

  As described above, the robot arm 28 of the robot body 20 includes the arm base shaft 22, the first arm portion 23, the second arm portion 24, the hand 25, the second arm rotation shaft 26, and the wrist shaft 27. This type of robot arm 28 is referred to as a SCARA horizontal articulated arm, and the robot control means 40 controls the operation of the robot arm 28, whereby the hand 25 is moved to a desired direction in the X-axis, Y-axis, and Z-axis directions. Can move to position.

  As shown in FIGS. 2 and 3, the robot body 20 includes a first arm driving means 29 for rotating the first arm portion 23, a second arm driving means 30 for rotating the second arm portion 24, and a wrist shaft. 27 is provided with a wrist shaft driving means 31 for rotationally driving 27 and an elevation driving means 32 for driving the arm base shaft 22 up and down.

  The first arm driving means 29 is disposed in the internal space of the robot base 21 and includes a servo motor 33 and its power transmission mechanism 34. The second arm driving means 30 is disposed in the internal space of the first arm portion 23 and includes a servo motor 35 and its power transmission mechanism 36. The wrist shaft driving means 31 is disposed in the internal space of the second arm portion 24 and includes a servo motor 37 and its power transmission mechanism 38. Each servo motor 33, 35, 37 has a built-in encoder 33A, 35A, 37A.

  As the power transmission mechanisms 34, 36, and 38, a gear power transmission mechanism including a reduction gear is used. The power of the servo motors 33, 35, and 37 is transmitted to the input side of the speed reducer, and the torque is amplified with a predetermined amplification ratio, and the rotational speed is reduced with the predetermined speed reduction ratio, so that the output side of the speed reducer Is output from. Thus, each of the arm base shaft 22, the second arm rotation shaft 26, and the wrist shaft 27 is rotationally driven by the power output from the output side of the speed reducer. Thereby, each of the 1st arm part 23, the 2nd arm part 24, and the hand 25 is rotationally driven.

  As a modification, the arm base shaft 22, the second arm rotation shaft 26, and / or the wrist shaft 27 may be driven by a direct drive motor.

  The elevation drive means 32 is provided inside the robot base 21 and is realized by a ball screw mechanism using a rotary motor capable of adjusting the amount of angular displacement. For example, the lift drive means 32 includes a screw rod, a screwed body that is screwed to the screw rod, and a rotary motor that rotationally drives the screw rod, and the arm base shaft 22 is fixed to the screwed body. A servo motor 39 having a built-in encoder 39A is used as the rotary motor of the lift drive means 32.

  In the robot main body 20 having the above-described configuration, the arm base shaft 22 is rotationally driven around the rotation axis L 1 with respect to the robot base 21 by the first arm driving means 29. As a result, the first arm portion 23 is rotationally driven around the rotation axis L <b> 1 with respect to the robot base 21.

  The second arm driving shaft 30 rotates the second arm rotation shaft 26 around the rotation axis L <b> 2 with respect to the first arm portion 23. As a result, the second arm portion 24 is rotationally driven around the rotation axis L <b> 2 with respect to the first arm portion 23.

  The wrist shaft 27 is rotationally driven around the rotation axis L <b> 3 with respect to the second arm portion 24 by the wrist shaft driving means 31. Thereby, the hand 25 is rotationally driven around the rotation axis L3 with respect to the second arm portion 24.

  The rotation axes L1, L2, and L3 are parallel to each other and extend in the Z-axis direction (vertical direction). As described above, the robot arm 28 is driven to be displaced with a degree of freedom in the X-axis, Y-axis, and Z-axis directions.

  The robot control means 40 includes encoders 33A, 35A, and 37A for the servo motors 33, 35, 37, and 39 of the first arm drive means 29, the second arm drive means 30, the wrist shaft drive means 31, and the lift drive means 32, respectively. 39A, by obtaining the angular positions of the servo motors 33, 35, 37, 39, the drive means 29, 30, 31, 32 can be feedback controlled. Thereby, the hand 25 can be accurately aligned with the target position.

  Next, a method for teaching the target position in the robot 10 will be described with reference to FIGS. Here, the target is a wafer cassette 51 for housing the semiconductor wafer 50.

  The CPU 42 of the robot control means 40 reads the temporary position data of the wafer cassette 51 stored in the storage unit 41, and the first arm driving means 29, the second arm driving means 30, the wrist axis driving means 31, and the elevation driving means. 32 is controlled, and the wafer 50 held on the hand 25 is inserted into the cassette 51.

  Here, the wafer cassette 51 is set such that the horizontal distance between the left and right inner wall surfaces 52 and 53 is slightly larger than the diameter of the wafer 50 based on the SEMI standard. Therefore, there is a gap on the side of the wafer 50 inserted into the cassette 51 that allows the wafer 50 to move in the left-right direction.

  Next, the robot control means 40 makes the control loop gain of the wrist axis driving means 31 substantially zero, and drives and controls at least one of the first arm driving means 29 and the second arm driving means 30. Then, the wafer 50 held by the hand 25 is brought into contact with one inner wall surface 52 (or 53) of the cassette 51 (a state indicated by phantom lines in FIGS. 4 and 5).

  Here, “to make the control loop gain of the wrist axis driving means 31 substantially zero” means changing the control loop gain from the servo gain of normal operation to a small value including zero to drive the wrist axis. When an external force is applied to the means 31, that is, when the hand 35 and the cassette 51 come into contact with each other, the contact reaction force is minimized, and the servomotor 37 of the wrist shaft drive means 31 responds to this contact reaction force. In other words, the angular position can be substantially freely displaced without substantially resisting. This includes the case where the control loop gain is cut to zero.

  When the wafer 50 comes into contact with the inner wall surface 52 (or 53) of the cassette 51, the control loop gain of the wrist shaft driving means 31 is substantially zero, so that the hand 25 together with the wafer 50 is angularly displaced around the rotation axis L3. As a result, the wrist shaft 27 is angularly displaced. The angular displacement of the wrist shaft 27 is transmitted to the servo motor 37 via the power transmission mechanism 38, and the servo motor 37 is angularly displaced.

  When the wafer 50 comes into contact with the inner wall surface 52 (or 53) of the cassette 51 as described above, the servo motor 37 is angularly displaced. Therefore, the angular displacement start time of the servo motor 37 is detected by a change in the position of the encoder. Then, the posture of the robot arm 28 and the angular position of the wrist shaft 27 at the time of detection are detected.

  Here, information on the posture of the robot arm 28 is acquired from the encoders 33A, 35A, 39A of the servo motors 33, 35, 39 of the first arm driving means 29, the second arm driving means 30, and the lifting / lowering driving means 32. be able to. Information on the angular position of the wrist shaft 27 can be obtained from the encoder 37A of the servo motor 37 of the wrist shaft driving means 31.

  Based on the shape / dimension data of the wafer 50 stored in the storage unit 41 and the detection result regarding the posture of the robot arm 28 at the time of contact and the angular position of the wrist shaft 27, the robot control means 40 is arranged in the XY plane. The position of the cassette inner wall surface 52 (or 53) is detected.

  The position data is acquired for the inner wall surfaces 52 and 53 on the left and right sides of the wafer cassette 51 by the operation described above. Thereby, the center position of the wafer cassette 51 in the left-right direction (the position of the teaching point) can be determined.

  In addition, as shown in FIG. 5, teaching data may be acquired for the inner wall surfaces 52 and 53 of the wafer cassette 51 at different positions in the Z-axis direction. Thereby, the position of the wafer cassette 51 can be determined more accurately.

  The timing at which the control loop gain of the wrist axis driving means 31 is substantially zero is determined based on the provisional position of the cassette inner wall surfaces 52 and 53 given in advance. The control loop gain may be made substantially zero just before the point at which contact is expected.

  As described above, in the robot 10 according to the present embodiment, the wrist shaft 27 and the wrist shaft driving means 31 act like a switch in the target position teaching operation. Then, the position of the target is detected and taught by detecting the posture of the robot arm 28 and the rotational position of the wrist shaft 27 when the switch is operated.

  In other words, the robot 10 of this embodiment does not detect the target position based on the difference between the command value related to the driving of the robot arm 28 and the current value, but detects the angular displacement of the wrist shaft 27 at the time of contact. is there.

  For this reason, it is not necessary to press the wafer 50 against the target (the inner wall surfaces 52 and 53 of the cassette), and the impact force at the time of contact between the wafer 50 and the target is extremely small (soft touch).

  In addition, since the start point of the angle change of the wrist shaft 27 at the time of contact is captured, the target position can be detected with high accuracy without being affected by the fluctuation elements and the time-varying elements of the drive system of the robot 10.

  Further, since the contact between the wafer 50 and the target is soft touch as described above, it is possible to reliably prevent the wafer 50 held by the hand 25 from being detached by contact with the target by vacuum suction or the like. Then, by performing the teaching operation while actually holding the wafer 50, it is possible to acquire accurate teaching data in accordance with the actual driving situation.

  In the embodiment described above, the wafer 50 held by the hand 25 is used as a contact member with the target (cassette 51). However, as shown in FIG. 6, the hand 25 itself is used as a contact member. The hand 25 may be sequentially brought into contact with the additionally installed target 54 from the left and right sides by the above-described soft touching operation.

  Based on the shape / dimension data of the hand 25 stored in the storage unit 41, the posture of the robot arm 28 at the time of contact, and the angular position of the wrist shaft 27, the robot control means 40 is configured to move the target 54 in the XY plane. Determine the position.

  Further, as shown in FIG. 7, the upper end portion of the cylindrical target 54 is tapered, and data relating to this shape is stored in the storage unit 41 in advance. The hand 25 is sequentially brought into contact with the left and right sides of the target 54 at a plurality of different positions in the Z-axis direction. Thereby, the data regarding the diameter of the target 54 in each Z direction position are obtained.

  Based on the diameter data at each Z direction position acquired in this way, the Z direction position at which the diameter of the target 54 changes is specified. Thereby, the position of the teaching point 54A in the Z direction on the target 54 can be determined.

  As mentioned above, although preferable embodiment of this invention was described, the said embodiment can be suitably changed within the scope of the present invention. For example, although the robot according to the above-described embodiment transports a semiconductor wafer (circular substrate), it can be replaced with a glass substrate (rectangular substrate) used for a liquid crystal display panel.

DESCRIPTION OF SYMBOLS 10 Robot 20 Robot main body 25 Hand 27 Wrist axis 28 Robot arm 29, 30 Arm drive means 31 Wrist axis drive means 37 Servo motor 37A Encoder 40 Robot control means 50 Contact member 51 Teaching target

Claims (10)

A robot arm in which a wrist shaft is provided at the tip so as to be horizontally rotatable;
Arm driving means for displacing the robot arm;
Wrist shaft driving means for rotationally driving the wrist shaft;
Robot control means for controlling the arm drive means and the wrist axis drive means,
The robot control means controls the arm driving means to move the tip of the robot arm,
When contacting the teaching target with the contact member attached to the wrist shaft,
Without the wrist shaft driving means resisting the contact reaction force from the teaching target,
Control so that the angular position can be freely displaced,
Detecting the posture of the robot arm and the angular position of the wrist shaft when the wrist shaft starts angular displacement by contact between the contact member and the teaching target;
A robot configured to determine a position of a teaching point based on the detection result. A robot arm in which a wrist shaft is provided at the tip so as to be horizontally rotatable;
Arm driving means for displacing the robot arm;
Wrist shaft drive means including a motor for rotationally driving the wrist shaft, and an encoder provided in the motor;
Robot control means for controlling the arm drive means and the wrist axis drive means,
The robot control means controls the arm driving means to move the tip of the robot arm,
When contacting the teaching target with the contact member attached to the wrist shaft,
Without the wrist shaft driving means resisting the contact reaction force from the teaching target,
Control so that the angular position can be freely displaced,
Due to the change of the position of the encoder due to the contact between the contact member and the teaching target,
Detecting the posture of the robot arm and the angular position of the wrist shaft when it is detected that the wrist shaft has started angular displacement;
A robot configured to determine a position of a teaching point based on the detection result.   The robot according to claim 1, further comprising an end effector attached to the wrist shaft, wherein the contact member is the end effector.   The robot according to claim 1, further comprising an end effector attached to the wrist shaft, wherein the contact member is a member held by the end effector. The end effector has holding means for holding a plate-like member,
The contact member is the plate-like member held by the end effector;
The robot according to claim 4, wherein the teaching target is a container for accommodating the plate-like member.   The robot according to any one of claims 1 to 5, wherein the robot arm is configured to be displaced and driven with a degree of freedom in the X-axis, Y-axis, and Z-axis directions.   The robot according to claim 6, wherein the robot control means is configured to detect a plurality of teaching points existing at different positions.   The robot according to claim 1, wherein the wrist axis is rotatable around a rotation axis in the direction of the Z axis. The robot arm is configured to be driven to be displaced with a degree of freedom in the X-axis, Y-axis, and Z-axis directions,
The robot control means moves the contact member at a plurality of different positions in the Z-axis direction with respect to a target whose position in the X-axis and Y-axis directions changes according to the position in the Z-axis direction. The robot according to claim 8, wherein the robot is configured to contact the target and determine the position of the teaching point in the Z-axis direction based on the plurality of detection results at the plurality of different positions. A method for teaching a position of a teaching point to a robot according to any one of claims 1 to 9,
Controlling the arm driving means by the robot control means to move the tip of the robot arm to bring the contact member attached to the wrist shaft into contact with the teaching target;
The posture of the robot arm and the angular position of the wrist axis when the wrist axis starts angular displacement due to contact between the contact member and the teaching target are detected, and the position of the teaching point is determined based on the detection result. A robot teaching method, comprising: a determining step.

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