Transfer device and its program, and method for correcting the position of a workpiece holding device.

Abstract

The present invention provides a transfer device that allows for alignment between a workpiece and a workpiece holding device using a simple configuration. [Solution] The transfer device moves the workpiece W placed on the stocker 30 to a predetermined position. The transfer device comprises a hand 22 that holds the workpiece W, a first robot 11 that moves the hand 22, a long-range photoelectric sensor 24 that outputs an ON signal or OFF signal as detection information for the presence or absence of an object in front of it at a predetermined distance, and a control device 4. When the stocker 30 is in the area in front of the hand 22, the control device 4 causes the first robot 11 to perform a movement operation that changes the posture and position of the hand 22, and calculates the distance Xd between the hand 22 and the stocker 30 based on the output information of the long-range photoelectric sensor 24 before and after the movement operation, and the posture information and position information of the hand 22.

Description

Technical Field

[0001] The present disclosure relates to a transfer device that moves a workpiece placed on a stocker to a predetermined position, a position correction method for a workpiece holding device, and a program that causes the transfer device to operate.

Background Art

[0002] When moving a workpiece placed on a stocker, it is necessary to align the robot hand and the workpiece so that the robot hand clamps a predetermined position of the workpiece. Patent Document 1 discloses a transfer device in which a distance measuring sensor capable of distance measurement is installed at the tip of a robot hand, and the alignment is performed based on the measurement value of the distance measuring sensor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] A distance measuring sensor measures the distance to an object based on the timing difference between laser light irradiation and light reception. Such a distance measuring sensor is excellent in precise distance measurement, but is very expensive. The application of the distance measuring sensor may cause an increase in the cost of the transfer device.

[0005] An object of the present disclosure is to provide a transfer device, a program thereof, and a position correction method for a workpiece holding device, which can align a workpiece and the workpiece holding device with a simple configuration.

Means for Solving the Problems

[0006] A transfer device according to one aspect of the present disclosure is a transfer device for moving a workpiece placed on a stocker to a predetermined position, comprising: a holding device for holding the workpiece; a robot for moving the holding device and outputting current posture information and current position information of the holding device; a first sensor for detecting the presence or absence of an object within a predetermined distance in front of the holding device, which outputs an on signal or an off signal; and a control device, wherein when the stocker is in the area in front of the holding device, the control device causes the robot to perform a movement operation to change the posture and position of the holding device, and calculates the distance between the holding device and the stocker based on the output information of the first sensor before and after the movement operation and the posture information and position information of the holding device.

[0007] A method for correcting the position of a workpiece holding device relating to another aspect of this disclosure is a method for correcting the position of a workpiece holding device in a transfer device that moves a workpiece placed on a stocker to a predetermined position, wherein the transfer device includes a robot that moves the holding device and outputs current attitude information and current position information of the holding device, and a first sensor that outputs an on signal or an off signal as detection information for the presence or absence of an object in front of it at a predetermined distance, The position correction method comprises, when the stocker is located in the front region of the holding device, causing the robot to perform a movement that changes the posture and position of the holding device, and calculating the distance between the holding device and the stocker based on the output information of the first sensor before and after the movement, and the posture and position information of the holding device.

[0008] A program relating to yet another aspect of this disclosure is a transfer device for moving a workpiece placed on a stocker to a predetermined position, the program comprising: a holding device for holding the workpiece; a robot for moving the holding device and outputting current posture information and current position information of the holding device; a first sensor for detecting the presence or absence of an object within a predetermined distance in front of the device, which is a program for operating the transfer device, wherein the program causes the control device to perform a movement operation that changes the posture and position of the holding device when the stocker is in the area in front of the holding device, and calculates the distance between the holding device and the stocker based on the output information of the first sensor before and after the movement operation and the posture information and position information of the holding device. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a transfer device and its program, as well as a method for correcting the position of a workpiece holder, that can align a workpiece with a workpiece holder using a simple configuration. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a perspective view showing the overall structure of a workpiece processing system to which the transfer device of this disclosure is applied. [Figure 2] Figure 2 is a top view of the workpiece processing system shown in Figure 1. [Figure 3] Figure 3 is a perspective view of the hand unit, which is the end effector of the robot. [Figure 4A] Figure 4A is a plan view of the hand unit shown in Figure 3. [Figure 4B] Figure 4B is a side view of the hand unit shown in Figure 3. [Figure 5] Figure 5 is a perspective view of the hand. [Figure 6] Figure 6 is a perspective view showing the gripping state of the workpiece by the hand, and an enlarged perspective view of the main VIA. [Figure 7]Figure 7 is a block diagram showing the control configuration of the workpiece processing system. [Figure 8] Figure 8 is a process chart for transferring a workpiece to the workpiece clamp device. [Figure 9] Figure 9 is a flowchart illustrating an example of stocker distance measurement processing performed by the control device. [Figure 10] Figure 10 is a diagram schematically showing a series of operations of the hand in the stocker distance measurement processing. [Figure 11] Figure 11 is a flowchart illustrating an example of stocker type identification processing performed by the control device. [Figure 12] Figure 12 is a diagram schematically showing a series of operations of the hand in the stocker type identification processing. [Figure 13] Figure 13 is a flowchart illustrating an example of yaw posture adjustment processing performed by the control device. [Figure 14] Figure 14 is a diagram schematically showing a series of operations of the hand unit in the yaw posture adjustment processing. [Figure 15] Figure 15 is a flowchart illustrating an example of roll posture adjustment processing performed by the control device. [Figure 16] Figure 16 is a diagram schematically showing a series of operations of the hand unit in the roll posture adjustment processing. [Figure 17] Figure 17 is a diagram schematically showing a modification example of a series of operations of the hand in the stocker distance measurement processing. [Modes for Carrying Out the Invention]

[0011] Hereinafter, embodiments of the transfer device, the program thereof, and the position correction method for a workpiece holding device according to the present disclosure will be described with reference to the drawings. The following embodiments show an example in which the transfer device of the present disclosure is applied to a workpiece processing system that performs predetermined processing on a workpiece. The transfer device transfers the workpiece from a workpiece storage location to a workpiece processing position of the workpiece processing system. The predetermined processing performed on the workpiece by the workpiece processing system includes, for example, polishing, cutting, severance, welding, painting, rust prevention, heating and the like of the workpiece. The transfer device of the present disclosure can also be applied to devices that do not involve predetermined processing on workpieces. For example, the transfer device of the present disclosure can also be applied to a transshipment device that reloads workpieces from one location to another, a workpiece cargo handling device for trucks, ships and the like.

[0012] [Overall Configuration of Workpiece Processing System] FIG. 1 is a perspective view showing the overall structure of a workpiece processing system 1 to which the transfer device of the present disclosure is applied. FIG. 2 is a top plan view of the workpiece processing system 1. The workpiece processing system 1 performs predetermined processing on an elongated workpiece W. The workpiece W shown in the present embodiment has a length of several meters and an arc shape. In FIG. 1 and FIG. 2, XYZ direction indicators are attached for convenience of description. The respective X, Y and Z directions are directions orthogonal to one another. Among these directions, the Z direction corresponds to the vertical direction of the workpiece processing system 1.

[0013] The workpiece processing system 1 comprises a processing chamber 10, a first robot 11, a second robot 12, a workpiece clamping device 13, and a stocker 30. The processing chamber 10 is a space for the first robot 11 and the second robot 12 to perform predetermined processing on the workpiece W. The first robot 11, the second robot 12, and the workpiece clamping device 13 are arranged within the processing chamber 10. The first robot 11 and the second robot 12 are 6-axis articulated robots. The first robot 11 and the second robot 12 are equipped with the necessary end effectors to grip the workpiece W and perform various processing on the workpiece W. The workpiece clamping device 13 holds the workpiece W to be processed. In this embodiment, the position of the workpiece clamping device 13 is the workpiece processing position. The stocker 30 is a trolley that can hold multiple workpieces W and be transported by an operator.

[0014] The processing room 10 is a rectangular space. The processing room 10 is partitioned by the first column 15A, the second column 15B, the third column 15C, and the fourth column 15D, the first panel 16A and the second panel 16B, and the first shutter 17A and the second shutter 17B. The first column 15A to the fourth column 15D are located at the four corners of the processing room 10 and stand perpendicular to the ground. The first panel 16A is located between the first column 15A and the second column 15B. The second panel 16B is located between the third column 15C and the fourth column 15D. The first shutter 17A is located between the first column 15A and the third column 15C. The second shutter 17B is located between the second column 15B and the fourth column 15D. Note that in Figure 1, for ease of understanding, the interior of the processing room 10 is depicted by viewing through the first panel 16A.

[0015] The first panel 16A and the second panel 16B, as well as the first shutter 17A and the second shutter 17B, partition the internal space of the processing chamber 10 from the external space, preventing chips and other debris generated during the processing of the workpiece W from scattering into the external space. The first shutter 17A is opened when the workpiece W to be processed is brought into the processing chamber 10. The second shutter 17B is opened when the processed workpiece W is removed from the processing chamber 10.

[0016] The workpiece clamping device 13 holds the workpiece W to be processed above the processing chamber 10. Figure 1 illustrates a workpiece clamping device 13 that holds an arc-shaped workpiece W at three points spaced apart in the X direction. The workpiece clamping device 13 is positioned between the support base of the first robot 11 and the support base of the second robot 12. The workpiece clamping device 13 is supported by a crossbeam 14. The crossbeam 14 extends in the X direction near the ceiling of the processing chamber.

[0017] The stocker 30 includes a first stocker 30A and a second stocker 30B. The first stocker 30A is positioned adjacent to the first shutter 17A, which is one side of the processing chamber 10 in the Y direction. The second stocker 30B is positioned adjacent to the second shutter 17B, which is the other side of the processing chamber 10 in the Y direction. The first stocker 30A holds the workpiece W before processing. The second stocker 30B holds the workpiece W after processing.

[0018] The first robot 11 takes the workpiece W to be processed from the first stocker 30A and transfers it to the workpiece holding position of the workpiece clamping device 13. During this transfer, a hand unit 2 is attached to the tip of the first robot 11 as an end effector. The hand unit 2 grasps the workpiece Wp to be processed from among the workpieces W placed in the first stocker 30A. The hand unit 2 is moved by the operation of the first robot 11, and the grasped workpiece Wp to be processed is carried into the processing chamber 10. After being carried in, the workpiece Wp to be processed is transferred from the hand unit 2 to the workpiece clamping device 13.

[0019] The first robot 11 also processes the workpiece Wp held by the workpiece clamping device 13. When the first robot 11 processes the workpiece Wp, an end effector for processing is attached to the tip of the first robot 11. For example, if the first robot 11 is to polish the workpiece Wp, a polishing brush is attached to the tip of the first robot 11. In this case, the workpiece Wp held by the workpiece clamping device 13 is polished by the polishing brush.

[0020] The second robot 12 removes the processed workpiece Wq from the workpiece clamping device 13 and transfers it to the second stocker 30B. During this transfer, a holding device similar to that of the hand unit 2 described above is attached to the tip of the second robot 12 as an end effector. The second robot 12 also processes the workpiece Wp. When the second robot 12 processes the workpiece Wp, a processing end effector is attached to the tip of the second robot 12.

[0021] [Storage structure] The first stocker 30A is positioned within the reach of the hand unit 2 attached to the first robot 11. The first stocker 30A includes an upper frame 31, a lower frame 32, a vertical frame 33, a support frame 34, casters 35, a handle 36, and a suspension support section 37. The second stocker 30B has the same structure as the first stocker 30A, so its description is omitted. Note that multiple types of the first stocker 30A and the second stocker 30B are prepared, differing in shape and size depending on the type of workpiece W.

[0022] The upper frame 31 is a rectangular frame structure that is long in the X direction. The lower frame 32 is a rectangular frame structure that is long in the X direction and is positioned opposite to and below the upper frame 31. The vertical frame 33 connects the upper frame 31 and the lower frame 32. Three vertical frames 33 are arranged at intervals in the X direction. The three vertical frames 33 connect the upper frame 31 and the lower frame 32 on the side opposite to the side of the first stocker 30A that faces the first shutter 17A.

[0023] The support frame 34 supports the workpiece W. The support frame 34 is fixed at one end to each of the three vertical frames 33 and extends in the Y direction. Three support frames 34 are arranged in the Z direction for each vertical frame 33. Each of the three stages of support frames 34 supports multiple workpieces W. In this embodiment, each of the three stages consists of three vertical frames 33. In other words, a group of three support frames 34 arranged in the X direction supports multiple workpieces W. The multiple workpieces W are supported in the Y direction on the support frames 34 of each stage. The side of the first stocker 30A facing the first shutter 17A is open. Therefore, the hand unit 2 can access the workpieces W on the support frames 34.

[0024] The casters 35 are attached to the underside of the lower frame 32. The casters 35 make the first stocker 30A portable. The handle 36 is attached to one end of the lower frame 32 in the X direction. When transporting the first stocker 30A, the worker grasps the handle 36. The lifting support parts 37 are arranged in pairs on the upper frame 31 at intervals in the X direction. The lifting support parts 37 are fittings having openings into which a lifting hook engages when lifting the first stocker 30A with a crane or the like. The arrangement position and spacing of the pair of lifting support parts 37 differ depending on the type of stocker. In this embodiment, the pair of lifting support parts 37 are used as detection pieces for determining the type of stocker.

[0025] The first stocker 30A is manually transported by an operator to a predetermined location adjacent to the processing chamber 10. Therefore, the positional accuracy of the first stocker 30A is low. For example, the first stocker 30A may be installed in a position deviating from its predetermined location, or it may be installed at an angle with respect to the X direction. The workpiece W placed on the first stocker 30A may also have variations in orientation. If the first robot 11 does not accurately align the hand unit 2 with the workpiece W on the first stocker 30A, it may fail to grasp the workpiece W. Therefore, it is essential for the workpiece processing system 1 to understand the position and orientation of the workpiece Wp to be processed in the first stocker 30A before having the hand unit 2 perform the grasping operation of the workpiece Wp to be processed. The same applies to the positional accuracy of the second stocker 30B and the second robot 12, so a detailed explanation is omitted.

[0026] [Hand unit structure] Figure 3 is a perspective view of the hand unit 2 attached to the first robot 11. Figure 4A is a top view of the hand unit 2, and Figure 4B is a right side view of the hand unit 2. Figures 3 to 4B include directional indicators for up, down, left, and right. These directional indicators are for illustrative purposes only and are not intended to limit the mounting or usage of the hand unit 2 on the robot's tip.

[0027] The hand unit 2 includes a bracket unit 20, a base frame 21B, a right arm 21R, a left arm 21L, and a hand 22 as a workpiece holder for the workpiece W. The bracket unit 20 is a detachable part for attaching the hand unit 2 to the robot tip of the first robot 11. With the bracket unit 20 attached to the robot tip, the hand unit 2 can move in the forward / backward, left / right and up / down directions by the 6-axis movement of the first robot 11, and can rotate in the pitch, yaw, and roll directions. Referring to the direction indicators in Figure 3, pitch indicates the rotation of the hand unit 2 around an axis extending in the left / right direction. Yaw indicates the rotation of the hand unit 2 around an axis extending in the up / down direction. Roll indicates the rotation of the hand unit 2 around an axis extending in the forward / backward direction.

[0028] The base frame 21B is attached to the bracket unit 20. The direction in which the base frame 21B and the bracket unit 20 are aligned is vertical, and the base frame 21B is attached to the upper side of the bracket unit 20. The base frame 21B supports the rear ends of the right arm 21R and the left arm 21L. The right arm 21R and the left arm 21L extend linearly in the front-rear direction. The right arm 21R extends forward from the right end of the base frame 21B. The left arm 21L extends forward from the left end of the base frame 21B. The right arm 21R and the left arm 21L are the same length and are positioned parallel to each other with a gap between them in the left-right direction. In other words, the forward projection length from the base frame 21B is the same for both the right arm 21R and the left arm 21L.

[0029] The hands 22 are attached to the front ends of the right arm 21R and the left arm 21L, respectively. The right hand 22R is attached to the right arm 21R, and the left hand 22L is attached to the left arm 21L. Hereafter, when the right hand 22R and the left hand 22L are not distinguished, they will simply be referred to as hand 22.

[0030] The right hand 22R is equipped with a first long-range photoelectric sensor 24R as the first sensor, a first short-range photoelectric sensor 25R as the fourth sensor, and a first contact sensor 26R as the second sensor. The left hand 22L is equipped with a second long-range photoelectric sensor 24L as the first sensor, a second short-range photoelectric sensor 25L as the fifth sensor, and a second contact sensor 26L as the third sensor. When not distinguishing between the right hand 22R and the left hand 22L, these are simply referred to as the long-range photoelectric sensor 24, the short-range photoelectric sensor 25, and the contact sensor 26.

[0031] Figure 5 is a perspective view of the right hand 22R. The left hand 22L is substantially identical. The hand 22 further includes a base 221, a clamp base 222, a slider 223, a bracket 224, and a clamp 23. The base 221 is fixed to the front end of the right arm 21R or the left arm 21L and supports the various equipment of the hand 22. The clamp base 222 holds the clamp 23 so that it can move vertically. The slider 223 is an integral part of the clamp 23. The slider 223 slides up and down along a guide in the clamp base 222. The bracket 224 is attached near the lower end of the side of the base 221. The bracket 224 supports the short-range photoelectric sensor 25 and the contact sensor 26.

[0032] The long-range photoelectric sensor 24 is mounted on the side of the clamp base 222. The long-range photoelectric sensor 24 outputs an ON signal or an OFF signal as detection information for the presence or absence of an object within a predetermined distance in front of it. The long-range photoelectric sensor 24 is a reflective type photoelectric sensor with a relatively long detectable distance. The long-range photoelectric sensor 24 includes a light-emitting unit OE and a light-receiving unit OR. The light-emitting unit OE consists of a semiconductor light-emitting element that emits inspection light such as visible light or infrared light. The light-receiving unit OR consists of a semiconductor light-receiving element that is sensitive to the inspection light emitted by the light-emitting unit OE. In this embodiment, the long-range photoelectric sensor 24 will be described as outputting an ON signal when an object is present in front of it and the light-receiving unit OR detects the reflected light from the object. The long-range photoelectric sensor 24 may also output an OFF signal when the light-receiving unit OR detects the reflected light.

[0033] As will be detailed later, the long-range photoelectric sensor 24 is used to measure the distance between the hand 22 and the stocker 30. A laser-type distance measuring sensor could be used for accurate distance measurement. However, such distance measuring sensors are expensive. The long-range photoelectric sensor 24 used in this embodiment is simply a sensor that outputs an ON or OFF signal depending on the presence or absence of an object. This type of photoelectric sensor is inexpensive and readily available. Therefore, this embodiment contributes to reducing the cost of the hand unit 2.

[0034] The short-range photoelectric sensor 25 is supported by a bracket 224 such that its light-emitting and receiving surface is located near the front of the clamp 23. The short-range photoelectric sensor 25 outputs an ON signal or an OFF signal as detection information for the presence or absence of an object within a predetermined distance in front of it. The short-range photoelectric sensor 25 is a photoelectric sensor with a shorter detectable distance compared to the long-range photoelectric sensor 24. In this embodiment, a fiber optic sensor is used as the short-range photoelectric sensor 25.

[0035] The fiber sensor consists of an optical fiber bundle in which multiple light-emitting and light-receiving optical fibers are arranged coaxially or in parallel. As shown in Figure 4B, laser amplifiers 251 are mounted on the right arm 21R and the left arm 21L. Inside the laser amplifier 251 are a light-emitting element and a light-receiving element. The light-emitting element inputs inspection light to the base end of the light-emitting optical fiber. The light-receiving element is located at the output end of the light-receiving optical fiber and detects the reflected light of the inspection light. In this embodiment, the short-range photoelectric sensor 25 also outputs an ON signal when the light-receiving element detects the reflected light.

[0036] The contact sensor 26 includes a contact probe 26P that contacts the object to be detected. The contact sensor 26 is supported by a bracket 224 such that the contact probe 26P protrudes beyond the front surface of the clamp 23. The contact sensor 26 outputs an ON signal or an OFF signal as detection information regarding whether or not the contact probe 26P is in contact with an object. The contact probe 26P of the first contact sensor 26R of the right hand 22R and the contact probe 26P of the second contact sensor 26L of the left hand 22L have the same forward protrusion height.

[0037] The clamps 23 are a pair of upper and lower members that grip the workpiece W. The pair of clamps 23 are mounted on the hand 22 facing each other in the vertical direction. Each clamp 23 is made of a metal block material having a roughly L-shape. The tip portion of the clamp 23 that contacts the workpiece W is fitted with a tip piece 23T made of resin material. The pair of clamps 23 move in accordance with the vertical movement of the slider 223. When gripping the workpiece W, the pair of clamps 23 move so that the tip piece 23T of the upper clamp 23 and the tip piece 23T of the lower clamp 23 move closer to each other. When releasing the workpiece W, the pair of clamps 23 move so that the upper and lower tip pieces 23T move further apart from each other.

[0038] Figure 6 is a perspective view showing an example of the gripping state of the workpiece Wp to be processed by the hand 22, and an enlarged perspective view of the main part VIA thereof. The workpiece Wp has a roughly Z-shaped cross section perpendicular to the longitudinal direction. Specifically, the workpiece Wp includes a relatively large flat plate portion 271, an upper bent portion 272 connected to the upper end of the flat plate portion 271, a lower bent portion 273 connected to the lower end of the flat plate portion 271, and a folded portion 274 connected to the tip of the lower bent portion 273. In Figure 6, an example is shown in which a pair of clamps 23 grip the lower bent portion 273 which forms a U-shaped groove. The upper bent portion 272 may also be gripped by the pair of clamps 23.

[0039] The long-range photoelectric sensor 24 and the short-range photoelectric sensor 25 may be replaced with other optical sensors that output an ON or OFF signal as detection information for the presence or absence of an object. Instead of optical sensors, electrical sensors such as eddy current sensors or physical sensors such as ultrasonic sensors may be used. In the above embodiment, an example is shown in which the long-range photoelectric sensor 24, the short-range photoelectric sensor 25, and the contact sensor 26 are mounted on the hand 22. These sensors 24, 25, and 26 may also be mounted on the left arm 21L and the right arm 21R, or on an arm that is linked to the hand unit 2.

[0040] [Control Configuration] Figure 7 is a block diagram showing the control configuration of the workpiece processing system 1. The workpiece processing system 1 includes a control device 4. The control device 4 consists of, for example, a processing unit having a processor that performs control functions by reading a program, or a personal computer. The control device 4 comprehensively controls the operation of the first robot 11, the second robot 12, the workpiece clamping device 13, and various other devices provided by the workpiece processing system 1.

[0041] The control device 4 includes a robot control unit 41, a workpiece processing control unit 42, and a storage unit 43. The robot control unit 41 controls the operation of the first robot 11 and the second robot 12, and the operation of the hand unit 2. The first robot 11 includes a robot body 110 that performs 6-axis articulated movement to move the aforementioned hand unit 2. The robot body 110 is capable of linearly moving the hand unit 2, and by extension the hand 22, in the XYZ directions, as well as rotating it in the pitch, yaw, and roll directions. The first robot 11 outputs data regarding the current position and current posture information of the hand 22 of the hand unit 2 to the robot control unit 41. The robot control unit 41 receives output information from the long-range photoelectric sensor 24, the short-range photoelectric sensor 25, and the contact sensor 26 mounted on the hand 22.

[0042] Figure 7 shows an example in which the hand unit 2 is attached to the first robot 11. If other end effectors are attached to the robot body 110, the current position information and current posture information of the end effectors, as well as the output information of the sensors equipped on the end effectors, are input to the robot control unit 41. The control of the second robot 12 and the hand unit 2 by the robot control unit 41 is the same as the control of the first robot 11 and the hand unit 2 described above.

[0043] The robot control unit 41 functionally includes a main body drive control unit 44, a hand drive control unit 45, a distance calculation unit 46, a type discrimination unit 47, and an adjustment angle calculation unit 48. The main body drive control unit 44 controls the movement of the six axes of the robot body 110. The main body drive control unit 44 controls the movement and posture of the hand unit 2 and the hand 22 by controlling the movement of the six axes. The hand drive control unit 45 controls the gripping operation of the workpiece W by the hand 22. The main body drive control unit 44 controls the position and posture of the hand 22 so that the hand 22 can properly grip the workpiece W.

[0044] The distance calculation unit 46 performs a process to calculate the distance between the hand 22 and the stocker 30. When calculating the distance, the distance calculation unit 46 refers to the output information of the ON or OFF signal of the long-range photoelectric sensor 24 and the attitude information and position information of the hand 22 output by the first robot 11. The distance calculation unit 46 performs the distance calculation process when it is detected that the stocker 30 is in the area in front of the hand 22 and a measurement command has been given. The output information of the long-range photoelectric sensor 24 may be either the output of the first long-range photoelectric sensor 24R and the second long-range photoelectric sensor 24L, or both may be used.

[0045] The type determination unit 47 performs a process to determine the type of the stocker 30. To determine the type, the type determination unit 47 refers to the output information of the ON or OFF signal of the long-range photoelectric sensor 24. Specifically, to determine the type, the type determination unit 47 refers to the position information in which the long-range photoelectric sensor 24 detected the presence of a pair of suspension support parts 37 provided on the first stocker 30A. The distance and height position between the pair of suspension support parts 37 are unique information that differs depending on the type of stocker 30. The type determination unit 47 determines the type of stocker 30 from the unique information and the detection information of the pair of suspension support parts 37 by the long-range photoelectric sensor 24.

[0046] The adjustment angle calculation unit 48 performs a process to calculate the adjustment angle for controlling the attitude of the hand 22 with respect to the workpiece W. Based on the contact detection information from the first contact sensor 26R and the second contact sensor 26L, which are spaced apart from each other, and the attitude information of the hand 22 provided by the first robot 11, the adjustment angle calculation unit 48 calculates the adjustment angle of the hand 22 in the yaw direction. The adjustment angle calculation unit 48 also calculates the adjustment angle of the hand 22 in the roll direction based on the output information of the ON or OFF signals from the first short-range photoelectric sensor 25R and the second short-range photoelectric sensor 25L, which are spaced apart from each other, and the attitude information of the hand 22.

[0047] The memory unit 43 stores various information such as parameters, settings, and device data necessary for controlling the work processing system 1. As an example, the memory unit 43 stores type information that associates the position information of a pair of suspension support parts in multiple types of stockers with the height information of the top of the stocker, in order to determine the type of stocker 30.

[0048] [Work Transfer Process Chart] Figure 8 is a process chart showing the steps sequentially executed when transferring a workpiece W. The chart in Figure 8 shows steps P1 to P6 that are sequentially executed when the workpiece Wp to be processed is taken out from the workpiece W placed on the first stocker 30A by the hand 22 of the first robot 11 and transferred to the workpiece clamping device 13 in the processing chamber 10. In the following description, the first stocker 30A will be simply referred to as stocker 30.

[0049] In step P1, the control device 4 performs a process to detect the presence of the stocker 30. Specifically, the process performed in step P1 is to move the hand 22 to a position where the stocker 30 is located in the area in front of the hand 22. The sensor used in step P1 is a long-range photoelectric sensor 24. The aforementioned area in front is the area in front of the hand 22 that falls within the detection range of the long-range photoelectric sensor 24.

[0050] Processes P2 and beyond are executed when the stocker 30 is located in the area in front of the hand 22. In process P2, the control device 4 measures the distance between the hand 22 and the stocker 30. The sensor used in process P2 is a long-range photoelectric sensor 24. Specifically, the control device 4 causes the first robot 11 to perform a movement that changes the posture and position of the hand 22. The control device 4 calculates the distance based on the output information of the long-range photoelectric sensor 24 before and after the movement, as well as the posture information and position information of the hand 22.

[0051] In step P3, the control device 4 performs a process to determine the type of stocker 30. The sensor used in step P3 is a long-range photoelectric sensor 24. The control device 4 controls the movement of the first robot 11 so that the detection range of the long-range photoelectric sensor 24 of the hand 22 passes through a pair of lifting support parts 37 equipped for lifting the stocker 30. The control device 4 determines the type of stocker 30 from the positions where the long-range photoelectric sensor 24 detects each of the pair of lifting support parts 37 and the distance between the pair of lifting support parts 37.

[0052] In step P4, the control device 4 performs a process to adjust the yaw position of the hand 22 with respect to the workpiece Wp being processed. The sensors used in step P4 are the first contact sensor 26R and the second contact sensor 26L. The control device 4 controls the movement of the first robot 11 to move and yaw rotate the hand 22 so that the first contact sensor 26R and the second contact sensor 26L sequentially contact the workpiece Wp being processed. Based on the contact position information of the first contact sensor 26R and the second contact sensor 26L with respect to the workpiece Wp and the yaw rotation angle information of the hand 22, the control device 4 calculates the yaw position adjustment angle for the hand 22.

[0053] In step P5, the control device 4 adjusts the roll posture of the hand 22 with respect to the workpiece Wp being processed. The sensors used in step P5 are a first short-range photoelectric sensor 25R and a second short-range photoelectric sensor 25L. The control device 4 moves the hand 22 so that either the first short-range photoelectric sensor 25R or the second short-range photoelectric sensor 25L detects the workpiece Wp, and then both the first short-range photoelectric sensor 25R and the second short-range photoelectric sensor 25L detect the workpiece Wp. Based on the detected position information of the workpiece Wp from the first short-range photoelectric sensor 25R and the second short-range photoelectric sensor 25L, the control device 4 calculates the roll posture adjustment angle for the hand 22.

[0054] In step P6, the control device 4 uses the distance information to the hand 22 and various attitude adjustment angles identified in steps P1 to P5 to control the movement of the first robot 11 so that the workpiece Wp to be processed is picked up from the stocker 30 by the hand 22. With the above workpiece transfer process, the gripping position of the workpiece Wp to be processed by the hand 22 can be determined using simple on / off sensors, namely the long-range photoelectric sensor 24 and the short-range photoelectric sensor 25, and the contact sensor 26, without using expensive distance measuring sensors. In addition, by identifying the type of stocker in step P3, the placement position of the workpiece Wp to be processed within the stocker 30 can also be roughly determined. Therefore, the movement path of the hand unit 2 can be easily optimized, contributing to a reduction in the cycle time of the workpiece transfer process.

[0055] The following provides a detailed explanation of specific examples of processes P1 through P5. The following explanation uses the XYZ coordinate system shown in Figures 1 and 2. Specifically, in the following explanation, the rotation of the hand 22 around the X-axis of the workpiece processing system 1 is referred to as pitch, the rotation around the Y-axis as roll, and the rotation around the Z-axis as yaw. Note that directional expressions such as up / down, forward / backward, and left / right may also be used, referring to the unique coordinates of the hand unit 2 shown in Figure 3. Furthermore, the pitch angle, yaw angle, and roll angle of the hand 22 are expressed as α, β, and γ, respectively.

[0056] <Process P1> As preparation before executing process P1, a hand unit 2 is attached to the tip of the first robot 11 as an end effector. The main body drive control unit 44 of the robot control unit 41 controls the movement of the robot body 110 so that the hand 22 of the hand unit 2 is positioned in a predetermined home position. The posture of the hand 22 is such that its tilt relative to the XY plane and XZ plane is zero. That is, the pitch angle α, yaw angle β, and roll angle γ are all zero. The robot control unit 41 activates the first long-range photoelectric sensor 24R of the right hand 22R and the second long-range photoelectric sensor 24L of the left hand 22L to enable object detection. The robot control unit 41 may activate only the first long-range photoelectric sensor 24R or the second long-range photoelectric sensor 24L.

[0057] The main drive control unit 44 moves the hand 22 from the home position to the predetermined starting position (X1, Y1, Z1) of the measurement operation. Then, the main drive control unit 44 moves the hand 22 in the required XYZ directions toward a position where the stocker 30 is assumed to be located in the area in front of the hand 22. When the robot control unit 41 receives an ON signal indicating the presence of the stocker 30 from both the first long-range photoelectric sensor 24R and the second long-range photoelectric sensor 24L, it determines that the stocker 30 is located in the area in front of the hand 22 and completes process P1. The XYZ position of the hand 22 at which the robot control unit 41 recognizes the presence of the stocker 30 is called the reference position. Alternatively, the position at which either the first long-range photoelectric sensor 24R or the second long-range photoelectric sensor 24L outputs an ON signal may be treated as the reference position.

[0058] <Process P2> Figure 9 is a flowchart showing an example of the distance measurement process between the hand 22 and the stocker 30 in step P2. Figure 10 is a schematic diagram showing a series of operations of the hand 22 in the distance measurement process. In step S1, the main drive control unit 44 positions the hand 22 to the reference position. Since the reference position is the position where the stocker 30 is detected, the first long-range photoelectric sensor 24R and the second long-range photoelectric sensor 24L are in a state where they output an ON signal. This state is represented as sensor output SW_ON in Figure 9.

[0059] In steps S2 and S3, the process of detecting the upper end of the stocker 30 is performed. In step S2, the main drive control unit 44 moves the hand 22 from the reference position to one side in the Z direction, i.e., upward. After the hand 22 starts moving, the sensor output SW_ON is in the ON state for a certain period of time. In step S3, the main drive control unit 44 moves the hand 22 to a position where the first long-range photoelectric sensor 24R and the second long-range photoelectric sensor 24L output an OFF signal, i.e., the sensor output SW_OFF state. The position in the hand 22 where the sensor output SW_OFF is in the OFF state is the position where the light receiving unit OR can no longer detect the reflected light of the inspection light emitted by the light emitting unit OE, and corresponds to the position of the upper end of the stocker 30.

[0060] The main drive control unit 44 records the coordinates (X2R, Y2R, Z2R, α2R, β2R, γ2R) of the position where the first long-range photoelectric sensor 24R is switched OFF, and the coordinates (X2L, Y2L, Z2L, α2L, β2L, γ2L) of the position where the second long-range photoelectric sensor 24L is switched OFF. The main drive control unit 44 calculates the coordinates (XM1, YM1, ZM1) of the hand center CP of the hand 22 from the average value of the coordinates (X2R, Y2R, Z2R) and the coordinates (X2L, Y2L, Z2L). The hand center CP is the center position of the opposing pair of clamps 23. The coordinates of the hand center CP are treated as position information of the holding device. The coordinates of the hand center CP (XM1, YM1, ZM1) are determined as the position of the upper end of the stocker 30. The coordinates (XM1, YM1, ZM1) detected in step S3 are used in step P3, which is described below.

[0061] Steps S4 and beyond are processes for measuring the distance between the hand 22 and the stocker 30. As shown in the upper diagram of Figure 10, in step S4, the main drive control unit 44 positions the hand 22 to the reference position and sets the sensor output SW_ON. The state in step S4 is that the hand 22 is in the first position and first orientation, and the long-range photoelectric sensor 24, which acts as the first sensor, outputs the first signal.

[0062] As shown in the middle diagram of Figure 10, in step S5, the main drive control unit 44 rotates the hand 22 by a predetermined pitch angle α. The pitch angle α is the angle at which the sensor output SW_OFF occurs. In the example of Figure 10, the hand 22 is rotated downward by a pitch angle α. The state in step S5 is a second position in which the hand 22 is tilted from the first position by a pitch angle α, which is the first predetermined angle, and the long-range photoelectric sensor 24, which is the first sensor, outputs a second signal.

[0063] In step S6, the main drive control unit 44 moves the hand 22 in the Z direction, which in this embodiment is upward, while keeping it tilted by a pitch angle α. After the hand 22 starts moving, the sensor output SW_OFF is active for a certain period of time. As shown in the lower diagram of Figure 10, in step S7, the main drive control unit 44 moves the hand 22 to a position where the first long-range photoelectric sensor 24R and the second long-range photoelectric sensor 24L output an ON signal, that is, the sensor output SW_ON. The state in step S7 is that the hand 22 has moved to the second position while maintaining the second posture, and the long-range photoelectric sensor 24, as the first sensor, outputs the first signal. The main drive control unit 44 records the coordinates (X3R, Y3R, Z3R, α3R, β3R, γ3R) of the position where the first long-range photoelectric sensor 24R is switched ON, and the coordinates (X3L, Y3L, Z3L, α3L, β3L, γ3L) of the position where the second long-range photoelectric sensor 24L outputs its sensor output ON. The main drive control unit 44 calculates the coordinates (XM2, YM2, ZM2) of the hand center CP of the hand 22 from the average value of the coordinates (X3R, Y3R, Z3R) and the coordinates (X3L, Y3L, Z3L).

[0064] In step S8, the distance calculation unit 46 calculates the distance between the hand 22 and the stocker 30. The distance calculation unit 46 calculates the distance xd between the hand 22 and the stocker 30 based on the distance d of the hand 22's movement in the Z direction between step S5 and step S7 and the pitch angle α. The distance calculation unit 46 calculates the distance xd using the following formula. xd = d / sinα

[0065] As described above, according to this embodiment, since the long-range photoelectric sensor 24 is mounted on the hand 22, the long-range photoelectric sensor 24 follows the movement of the hand 22. For this reason, it is easy to position the long-range photoelectric sensor 24 opposite the stocker 30. Furthermore, the distance xd between the hand 22 and the stocker 30 can be calculated simply by monitoring the ON or OFF signal of the long-range photoelectric sensor 24 and determining the pitch angle α and the movement distance d in the Z direction of the hand 22. In other words, an expensive distance measuring sensor is not required to calculate the distance xd.

[0066] <Process P3> Figure 11 is a flowchart showing an example of the stocker type identification process in step P3. Figure 12 is a schematic diagram illustrating a series of operations of the hand 22 in the stocker type identification process. Figure 12 schematically shows the upper part of the stocker 30. For ease of explanation, Figure 12 includes up, down, left, and right direction indicators for the stocker 30. The stocker 30 includes a stocker body 300 and a pair of suspension support parts 37, namely a right suspension support part 37R and a left suspension support part 37L. The right suspension support part 37R corresponds to the second detection piece. The left suspension support part 37L corresponds to the first detection piece.

[0067] The right suspension support section 37R and the left suspension support section 37L protrude upward from the upper frame 31 and each have a suspension hole 38. When lifting the stocker 30, the worker engages a lifting hook or the like with the suspension hole 38. The distance between the support sections between the right suspension support section 37R and the left suspension support section 37L varies depending on the type of stocker 30. The stocker list in the memory unit 43 describes the distance between the support sections and the type of stocker in association. Figure 12 shows one of the hands 22 of the hand unit 2 and an example of the movement path of the hand 22 in the stocker type identification process. In the stocker type identification process, for example, only the first long-range photoelectric sensor 24R of the right hand 22R is used for measurement. The position of the hand 22 shown in Figure 12 is the starting position (X1, Y1, Z1) of the measurement operation described above.

[0068] In steps S11 to S13, the main drive control unit 44 moves the hand 22 upward by a predetermined distance from the starting position. During the movement, it passes through position F1, which is the reference position in step S11, and position F2, which is the upper end of the stocker 30 in step S12. The moving position F3 in step S13 is the height position of the suspension hole 38. At position F1, the long-range photoelectric sensor 24 is in the sensor output SW_ON state, and at position F2, the sensor output SW_OFF state.

[0069] The state in step S11 corresponds to the state in which the hand 22 is at the third position in the opposing region of the stocker body 300, and the long-range photoelectric sensor 24, which acts as the first sensor, outputs the third signal. The opposing region is the region in which the long-range photoelectric sensor 24 is directly facing the stocker body 300, and is not necessarily the region in which the hand 22 is directly facing the stocker body 300. The state in step S12 corresponds to the state in which the hand 22 is at the fourth position, and the long-range photoelectric sensor 24 outputs the fourth signal. Step S12 is a process to acquire first position information, which is the height information of the top of the stocker 30, i.e., the upper end of the stocker body 300. The XYZ coordinates (XM1, YM1, ZM1) of the upper end of the stocker body 300 have already been acquired in step S3 of process P2. Therefore, from the starting position to position F3, it is simply necessary to move the hand 22 upwards. Of course, in process P2, steps S1 to S3 may be omitted, and the XYZ coordinates (XM1, YM1, ZM1) of the upper end of the stocker body 300 may be determined in steps S11 and S12 performed in process P3.

[0070] In steps S14 to S17, the main drive control unit 44 moves the hand 22 to the right, passing sequentially through the opposing regions of the left suspension support 37L and the right suspension support 37R, creating a state in which the long-range photoelectric sensor 24 outputs a sensor output SW_ON. The state created in steps S14 to S17 corresponds to the state in which the hand 22 moves to the fifth position, which is the opposing region of the suspension support 37 as a detection piece, and the long-range photoelectric sensor 24 outputs a third signal. The type determination unit 47 determines the type of the stocker 30 based on the coordinates (XM1, YM1, ZM1) as the first position information and the second position information, which is the position information of the fifth position.

[0071] In step S13, the hand 22 is outside the opposing area of ​​the stocker body 300, so the sensor output SW_OFF. In step S14, the main drive control unit 44 starts moving the hand 22 to the right. In step S15, when the hand 22 reaches position F4, the left edge of the left suspension support part 37L which is the first detection piece, the long-range photoelectric sensor 24 turns SW_ON. The type discrimination unit 47 records the coordinates (X4, Y4, Z4) of the hand 22 at this time. Position F4 may be set as appropriate. For example, position F4 may be the left or right edge of the suspension hole 38.

[0072] In step S16, the main drive control unit 44 moves the hand 22 further to the right. The long-range photoelectric sensor 24 enters the state of sensor output SW_ON. In step S17, when the hand reaches position F5, the left edge of the right suspension support part 37R which is the second detection piece, the long-range photoelectric sensor 24 enters the state of SW_ON again. The type determination unit 47 records the coordinates (X5, Y5, Z5) of the hand 22 at this time.

[0073] In step S18, the type determination unit 47 calculates the distance between the right suspension support unit 37R and the left suspension support unit 37L from the coordinates of position F4 (X4, Y4, Z4) and position F5 (X5, Y5, Z5). In step S19, the type determination unit 47 compares the distance between the support units and the coordinates (XM1, YM1, ZM1), which are the height information of the top of the stocker 30, with the stocker list in the storage unit 43 as reference information. The stocker list is a database that associates the type of stocker with the distance between the support units and the height information of the top of the stocker 30. In step S20, the type determination unit 47 determines the type of stocker 30 based on the result of the comparison with the stocker list.

[0074] According to the above embodiment, the unique shape of the stocker 30 can be detected based on the on / off signal of the long-range photoelectric sensor 24 and the position information of the stocker body 300 and the suspension support parts 37R and 37L. In other words, when there are multiple stockers 30 having various shapes corresponding to various workpieces W, the type of stocker 30 can be determined using a simple on / off sensor. By determining the type of stocker, the position where the workpiece W is placed on the stocker 30 can also be roughly determined. Therefore, it can contribute to shortening the cycle time of the workpiece transfer process.

[0075] <Process P4> Figure 13 is a flowchart showing an example of the yaw attitude adjustment process in step P4. Figure 14 is a schematic diagram illustrating a series of operations of the hand unit 2 in the yaw attitude adjustment process. In Figure 14, the hand unit 2 and the workpiece Wp to be processed are schematically shown. The workpiece Wp to be processed may be mounted on the stocker 30 with an angular displacement in the yaw direction relative to the hand 22. In step P4, the angular displacement in the yaw direction is detected. The robot body 110 can rotate the hand unit 2 around the axis of the yaw rotation axis 2Y.

[0076] In step S31, the main drive control unit 44 selects a workpiece Wp from among the workpieces W placed on the stocker 30 that the hand 22 will grasp in this operation. When selecting the workpiece Wp, the main drive control unit 44 refers to the information described in the stocker list of the storage unit 43 for the stocker 30 identified in step P4. The main drive control unit 44 also obtains the position information of the workpiece Wp from the storage unit 43.

[0077] In step S32, the main drive control unit 44 moves the hand unit 2 so that the first contact sensor 26R of the right hand 22R and the second contact sensor 26L of the left hand 22L face the workpiece Wp to be processed, based on the position information acquired in step S31. As shown in the upper diagram of Figure 14, in step S33, the main drive control unit 44 moves the hand unit 2 forward FW so that the hand unit 2 approaches the workpiece Wp to be processed. In step S34, the main drive control unit 44 determines whether either the first contact sensor 26R or the second contact sensor 26L outputs an ON signal.

[0078] If the answer in step S34 is NO, the main drive control unit 44 continues to move the hand unit 2 toward the forward FW. If the answer in step S34 is YES, the process proceeds to step S35, and the main drive control unit 44 stops moving the hand unit 2 toward the forward FW. The middle diagram of Figure 14 shows the state in step S35. Figure 14 shows an example where the contact probe 26P of the second contact sensor 26L makes contact with the workpiece Wp to be processed and outputs an ON signal. The main drive control unit 44 records the coordinates (X6L, Y6L, Z6L, α6L, β6L, γ6L) indicating the position and orientation of the left hand 22L at this time. The state in step S35 is when the second contact sensor 26L, acting as the third sensor, makes contact with the workpiece Wp to be processed, and the left hand 22L assumes the sixth position and third orientation.

[0079] In step S36, the main drive control unit 44 rotates the hand unit 2 around the yaw axis 2Y. In step S37, the main drive control unit 44 determines whether the first contact sensor 26R outputs an ON signal. If the result in step S37 is NO, the main drive control unit 44 continues the yaw rotation of the hand unit 2. If the result in step S37 is YES, the process proceeds to step S38, and the main drive control unit 44 stops the yaw rotation of the hand unit 2.

[0080] The lower diagram of Figure 14 shows the state at step S38. The contact probe 26P of the first contact sensor 26R is in contact with the workpiece Wp to be processed and has output an ON signal. The yaw rotation angle θy is defined as the rotation angle of the hand unit 2 from the time the second contact sensor 26L outputs an ON signal until the first contact sensor 26R outputs an ON signal. The main drive control unit 44 records the coordinates (X6R, Y6R, Z6R, α6R, β6R, γ6R) indicating the position and orientation of the right hand 22R at this time.

[0081] The state in step S38 is that the hand unit 2 has rotated by a yaw rotation angle θy, which is a second predetermined angle, until both the first contact sensor 26R and the second contact sensor 26L make contact with the workpiece Wp to be processed, and has taken on a fourth posture. In step S39, the adjustment angle calculation unit 48 calculates the yaw rotation angle θy using the coordinates (X6L, Y6L, Z6L, α6L, β6L, γ6L) recorded in step S35 and the coordinates (X6R, Y6R, Z6R, α6R, β6R, γ6R) recorded in step S38.

[0082] According to the above embodiment, the yaw direction attitude of the right hand 22R and left hand 22L with respect to the workpiece Wp can be controlled using only the on / off signals of two simple contact sensors, the first contact sensor 26R and the second contact sensor 26L. This attitude control can suppress the occurrence of gripping errors of the workpiece Wp by the clamp 23.

[0083] <Process P5> Figure 15 is a flowchart showing an example of the roll attitude adjustment process in step P5. Figure 16 is a schematic diagram illustrating a series of operations of the hand unit 2 in the roll attitude adjustment process. In Figure 16, the hand unit 2 equipped with the first short-range photoelectric sensor 25R and the second short-range photoelectric sensor 25L, and the workpiece Wp to be processed are schematically shown. The workpiece Wp to be processed is placed on multiple support frames 34 of the stocker 30. Ideally, the arc-shaped workpiece Wp to be processed should be supported by the support frames 34 at the same height at its left and right ends. However, as shown in the appendix to Figure 16, the workpiece Wp to be processed may be placed on the stocker 30 with an angle shift in the roll direction. In step P5, the angle shift in the roll direction is detected.

[0084] In step S41, the main drive control unit 44 selects the workpiece Wp to be processed and acquires the position information of the workpiece Wp. Since the position information of the workpiece Wp has already been acquired in step S31 of process P4, step S41 may be omitted. In step S42, the main drive control unit 44 moves the hand unit 2 to a predetermined position based on the position information acquired in step S41. The predetermined position is a position where the short-range photoelectric sensor 25 is in front of the workpiece Wp to be processed, but the short-range photoelectric sensor 25 does not detect the workpiece Wp to be processed.

[0085] In step S43, the main drive control unit 44 moves the hand unit 2 in a straight line downward so that it is positioned at the same height as the workpiece Wp to be processed. In step S44, the main drive control unit 44 determines whether either the first short-range photoelectric sensor 25R or the second short-range photoelectric sensor 25L outputs an ON signal. If the answer in step S44 is NO, the main drive control unit 44 continues to move the hand unit 2 downward.

[0086] If the answer in step S44 is YES, the process proceeds to step S45, where the coordinates of the hand 22 that output the ON signal are recorded. Figure 16 shows an example where the second short-range photoelectric sensor 25L detects the position Z1 of the upper edge of the workpiece Wp to be processed and outputs an ON signal. The main drive control unit 44 records the coordinates (X7L, Y7L, Z7L, α7L, β7L, γ7L) indicating the position and orientation of the left hand 22L at this time. The state in step S45 is that the second short-range photoelectric sensor 25L, acting as the fifth sensor, detects the workpiece Wp to be processed, and the left hand 22L is in the seventh position.

[0087] In step S46, the main drive control unit 44 continues the downward movement of the hand unit 2. In step S47, the main drive control unit 44 determines whether the first short-range photoelectric sensor 25R outputs an ON signal. If the answer in step S47 is NO, the main drive control unit 44 continues the downward movement of the hand unit 2. If the answer in step S47 is YES, the process proceeds to step S48, and the main drive control unit 44 stops the downward movement of the hand unit 2.

[0088] Figure 16 shows an example where, when the hand unit 2 has descended by ΔZ from position Z1, the first short-range photoelectric sensor 25R detects the position Z2 of the upper edge of the workpiece Wp to be processed and outputs an ON signal. In step S48, the main drive control unit 44 records the coordinates (X7R, Y7R, Z7R, α7R, β7R, γ7R) indicating the position and orientation of the right hand 22R at this time. The state in step S48 is that the right hand 22R is in the eighth position, and both the second short-range photoelectric sensor 25L as the fifth sensor and the first short-range photoelectric sensor 25R as the fourth sensor output ON signals indicating the detection of the workpiece Wp to be processed.

[0089] In step S49, the adjustment angle calculation unit 48 calculates the roll rotation angle θs, which is the angular error in the roll direction. The roll rotation angle θs can be calculated using the coordinates (X7L, Y7L, Z7L, α7L, β7L, γ7L) recorded in step S45, the coordinates (X7R, Y7R, Z7R, α7R, β7R, γ7R) recorded in step S48, and the distance Xs between the first short-range photoelectric sensor 25R and the second short-range photoelectric sensor 25.

[0090] [Differentiation] Although embodiments of the present disclosure have been described above, various modified embodiments can be adopted in place of the embodiments described above. For example, in the distance measurement process of step P2, the hand 22 may be operated in a different manner than that shown in Figure 10. Figure 17 is a schematic diagram showing a modified example of a series of operations of the hand 22 in the distance measurement process. The upper part of Figure 17 shows the state in which the hand 22 is in the reference position, corresponding to step S4 in Figures 9 and 10.

[0091] The middle diagram of Figure 17 corresponds to step S5 in Figures 9 and 10. In the example of Figure 10, the hand 22 is rotated downward by a pitch angle α. In contrast, in the modified example, the hand 22 is rotated upward by a pitch angle α. By rotating the hand 22 upward by a pitch angle α, the long-range photoelectric sensor 24 enters the sensor output SW_OFF state. The bottom diagram of Figure 17 corresponds to step S7 in Figures 9 and 10. In the modified example, the hand 22 is moved downward while remaining tilted upward until the sensor output SW_ON state is reached. The distance calculation unit 46 calculates the distance xd between the hand 22 and the stocker 30 based on the Z-direction movement distance d of the hand 22 and the pitch angle α. The distance calculation unit 46 calculates the distance xd using the following formula. xd = d / tanα

[0092] As a further modification, the hand 22 may be moved horizontally to measure the distance between the hand 22 and the stocker 30. In this case, the initial position of the hand 22 is rotated 90 degrees in the roll direction relative to the position shown in Figures 10 and 17. The long-range photoelectric sensor 24 is positioned opposite the upper frame 31 of the stocker 30 near the X-direction end. By rotating the hand 22 by a pitch angle α and moving the hand 22 horizontally, the data necessary for calculating the distance xd can be obtained.

[0093] In the above embodiment, an example was shown in which the hand 22, which serves as a workpiece W holding device, is composed of a pair of right hand 22R and left hand 22L. The hand 22 may be composed of a single unit or of three or more units. In the above embodiment, a clamp 23 was exemplified as a member that generates the holding force for the workpiece W in the hand 22. Instead of the clamp 23, a negative pressure adsorption mechanism or a magnetic adsorption mechanism may be used.

[0094] [Summary of this disclosure] The specific embodiments described above include disclosures having the following configurations.

[0095] A transfer device according to a first aspect of the present disclosure is a transfer device for moving a workpiece placed on a stocker to a predetermined position, comprising: a holding device for holding the workpiece; a robot for moving the holding device and outputting current posture information and current position information of the holding device; a first sensor for detecting the presence or absence of an object within a predetermined distance in front of the holding device, which outputs an on signal or an off signal; and a control device, wherein when the stocker is in the area in front of the holding device, the control device causes the robot to perform a movement operation to change the posture and position of the holding device, and calculates the distance between the holding device and the stocker based on the output information of the first sensor before and after the movement operation and the posture information and position information of the holding device.

[0096] According to the first embodiment, distance information between the holding device and the stocker can be acquired using a first sensor that simply outputs an ON or OFF signal depending on the presence or absence of an object. Therefore, a transfer device can be configured without using expensive distance measuring sensors. Furthermore, by determining the position of the stocker based on the distance information, the position of the workpiece placed on the stocker can also be roughly determined. Therefore, the cycle time of the process from holding to transferring the workpiece can be shortened.

[0097] The transfer device according to the second embodiment is the transfer device according to the first embodiment, wherein the first sensor is mounted on the holding device, and the control device controls the robot when the stocker is in the front region of the holding device, to sequentially create the following states: a state in which the holding device is in a first position and first orientation relative to the stocker and the first sensor outputs a first signal, either the ON signal or the OFF signal; a state in which the holding device is in a second orientation tilted by a first predetermined angle from the first orientation and the first sensor outputs a second signal different from the first signal; and a state in which the holding device moves to a second position different from the first position relative to the stocker while maintaining the second orientation and the first sensor outputs a first signal, and calculates the distance between the holding device and the stocker based on distance information between the first position and the second position and the first predetermined angle.

[0098] According to the second embodiment, since the first sensor is mounted on the holding device, the first sensor follows the movement of the holding device. This makes it easy to position the first sensor opposite the stocker. Furthermore, by simply monitoring the movement of the holding device and the output of the first sensor in response to changes in the attitude of the holding device, the information necessary to calculate the distance between the holding device and the stocker can be obtained.

[0099] In the transfer device according to the third embodiment, in the transfer device according to the first or second embodiment, the control device calculates the distance xd between the holding device and the stocker using the following formula, where d is the distance between the first position and the second position and α is the first predetermined angle. xd = d / sinα

[0100] According to the third embodiment, the distance between the holding device and the stocker can be calculated using a simple mathematical formula, thereby reducing the processing load on the control device.

[0101] The transfer device according to the fourth embodiment is a transfer device according to any of the first to third embodiments, wherein the stocker includes a stocker body and a detection piece positioned at a specific location on the stocker body, the first sensor is mounted on the holding device, and the control device, when the stocker is in the forward region of the holding device, controls the robot to sequentially create the following states: a state in which the holding device is at a third position in the region opposite to the stocker body and the first sensor outputs a third signal, either the ON signal or the OFF signal; a state in which the holding device moves to a fourth position different from the third position and the first sensor outputs a fourth signal different from the third signal; and a state in which the holding device moves to a fifth position which is the region opposite to the detection piece and the first sensor outputs the third signal, and the type of the stocker is determined based on first position information, which is the position information of the fourth position, and second position information, which is the position information of the fifth position.

[0102] According to the fourth embodiment, the unique shape of the stocker can be detected based on the on / off signal of the first sensor and the position information of the stocker body and the detection piece. That is, when there are multiple stockers corresponding to various workpieces, the type of stocker can be determined. By determining the type of stocker, the placement position of the workpiece can also be roughly determined. Therefore, it can contribute to shortening the cycle time of the process.

[0103] The transfer device according to the fifth embodiment is a transfer device according to any of the first to fourth embodiments, wherein the detection piece includes a first detection piece and a second detection piece arranged spaced apart from each other, the first position information is information about the height of the top of the stocker, the second position information is information about the distance between the first detection piece and the second detection piece, the transfer device further includes a storage unit that stores type information relating the type of the stocker, the position information of the first detection piece and the second detection piece, and the height information of the top of the stocker, and the control device determines the type of the stocker by referring to the first position information, the second position information and the type information.

[0104] According to the fifth embodiment, a first detection piece and a second detection piece are used to determine the type of stocker. The second position information, as position information of the fifth position, is the distance between the first detection piece and the second detection piece. If the distance between the first detection piece and the second detection piece is set to a distance unique to each stocker, the stocker type determination process can be simplified.

[0105] The transfer device according to the sixth embodiment is a transfer device according to any of the first to fifth embodiments, wherein the first detection piece and the second detection piece are a pair of suspension support parts having suspension holes for the stocker.

[0106] According to the sixth embodiment, since the suspension support portion of the stocker is used as a detection piece, there is no need to attach a separate detection piece to the stocker.

[0107] The transfer device according to the seventh embodiment further comprises a second sensor and a third sensor, which include a contact probe and output an ON signal or an OFF signal as detection information of whether or not the contact probe is in contact with an object, the second sensor and the third sensor are spaced apart from each other, and each of the contact probes is mounted on the holding device with the same forward projection height, and the control device controls the robot when a workpiece mounted on the stocker is present in the front region of the holding device, so that the holding device sequentially forms a sixth position and a third posture in which the contact probe of either the second sensor or the third sensor is in contact with the workpiece, and a fourth posture in which the holding device is rotated by a second predetermined angle from the third posture in which the contact probes of both the second sensor and the third sensor are in contact with the workpiece, and the control device controls the posture of the holding device with respect to the workpiece based on the sixth position and the second predetermined angle.

[0108] According to the seventh embodiment, the yaw orientation of the holding device relative to the workpiece can be controlled using only the on / off signals of two contact sensors, the second sensor and the third sensor.

[0109] The transfer device according to the eighth embodiment further comprises, in addition to the first sensor, a fourth sensor and a fifth sensor that output an on signal or an off signal as detection information for the presence or absence of an object within a predetermined distance in front of the transfer device according to any of the first to seventh embodiments, wherein the fourth sensor and the fifth sensor are mounted on the holding device spaced apart from each other, and the control device controls the robot when a workpiece mounted on the stocker is present in the area in front of the holding device, so that the holding device sequentially sets up a seventh position in which either the fourth sensor or the fifth sensor outputs an on signal or an off signal indicating the detection of the workpiece, and an eighth position in which both the fourth sensor and the fifth sensor output an on signal or an off signal indicating the detection of the workpiece, and controls the attitude of the holding device with respect to the workpiece based on the position information of the seventh position and the eighth position.

[0110] According to the eighth aspect, the orientation of the holding device in the roll direction relative to the workpiece can be controlled using only the on / off signals of two object detection sensors, the fourth sensor and the fifth sensor.

[0111] A position correction method for a workpiece holding device according to a ninth aspect is a position correction method for a workpiece holding device that holds a workpiece in a transfer device that moves a workpiece placed on a stocker to a predetermined position, wherein the transfer device includes a robot that moves the holding device and outputs current attitude information and current position information of the holding device, and a first sensor that outputs an on signal or an off signal as detection information for the presence or absence of an object in front of it at a predetermined distance, and the position correction method comprises causing the robot to perform a movement operation that changes the attitude and position of the holding device when the stocker is in the area in front of the holding device, and calculating the distance between the holding device and the stocker based on the output information of the first sensor before and after the movement operation and the attitude and position information of the holding device.

[0112] According to the ninth embodiment, distance information between the holding device and the stocker can be acquired using a first sensor that simply outputs an ON or OFF signal depending on the presence or absence of an object. Therefore, the position of the workpiece holding device can be corrected without using an expensive distance measuring sensor.

[0113] The position correction method for a workpiece holding device according to the tenth embodiment is a position correction method for the ninth embodiment, wherein the first sensor is mounted on the holding device, and when the stocker is in the front region of the holding device, the robot's operation sequentially creates the following states: a state in which the holding device is in a first position and first orientation relative to the stocker, and the first sensor outputs a first signal, either the ON signal or the OFF signal; a state in which the holding device is in a second orientation tilted by a first predetermined angle from the first orientation, and the first sensor outputs a second signal different from the first signal; and a state in which the holding device moves to a second position different from the first position relative to the stocker while maintaining the second orientation, and the first sensor outputs a first signal. The distance between the holding device and the stocker is calculated based on the distance information between the first position and the second position and the first predetermined angle.

[0114] According to the tenth embodiment, since the first sensor is mounted on the holding device, the first sensor follows the movement of the holding device. This makes it easy to position the first sensor opposite the stocker. Furthermore, by simply monitoring the movement of the holding device and the output of the first sensor in response to changes in the attitude of the holding device, the information necessary to calculate the distance between the holding device and the stocker can be obtained.

[0115] The position correction method for a workpiece holding device according to the 11th embodiment is the 9th or 10th position correction method, wherein the stocker includes a stocker body and a detection piece positioned at a specific location on the stocker body, the first sensor is mounted on the holding device, and when the stocker is in the front region of the holding device, the robot's operation sequentially creates the following states: a state in which the holding device is at a third position in the region opposite to the stocker body and the first sensor outputs a third signal, either the ON signal or the OFF signal; a state in which the holding device moves to a fourth position different from the third position and the first sensor outputs a fourth signal different from the third signal; and a state in which the holding device moves to a fifth position which is the region opposite to the detection piece and the first sensor outputs the third signal, and the type of the stocker is determined based on the first position information, which is the position information of the fourth position, and the second position information, which is the position information of the fifth position.

[0116] According to the eleventh embodiment, the unique shape of the stocker can be detected based on the on / off signal of the first sensor and the position information of the stocker body and the detection piece. In other words, when there are multiple stockers corresponding to various types of workpieces, the type of stocker can be determined.

[0117] The position correction method for a workpiece holding device according to the 12th embodiment is a position correction method according to any of the 9th to 11th embodiments, wherein a second sensor and a third sensor are prepared, each including a contact probe and outputting an ON signal or an OFF signal as detection information of whether or not the contact probe is in contact with an object, the second sensor and the third sensor are spaced apart from each other, and each of the contact probes is mounted on the holding device with the same forward protrusion height, and when a workpiece mounted on the stocker is in the front region of the holding device, the robot operation sequentially causes the holding device to be in a sixth position and a third posture in which the contact probe of either the second sensor or the third sensor is in contact with the workpiece, and a fourth posture in which the holding device is rotated by a second predetermined angle from the third posture, in which the contact probes of both the second sensor and the third sensor are in contact with the workpiece, and the posture of the holding device with respect to the workpiece is controlled based on the sixth position and the second predetermined angle.

[0118] According to the twelfth embodiment, the yaw orientation of the holding device relative to the workpiece can be controlled using only the on / off signals of two contact sensors, the second sensor and the third sensor.

[0119] The position correction method for a workpiece holding device according to the 13th embodiment is a position correction method according to any of the 9th to 12th embodiments, wherein in addition to the first sensor, a fourth sensor and a fifth sensor are prepared that output an ON signal or an OFF signal as detection information for the presence or absence of an object in front of a predetermined distance, the fourth sensor and the fifth sensor are mounted on the holding device spaced apart from each other, and when a workpiece mounted on the stocker is present in the front region of the holding device, the robot operation sequentially sets the holding device to a 7th position and a 4th posture in which either the 4th sensor or the 5th sensor outputs an ON signal or an OFF signal indicating the detection of the workpiece, and the holding device to a 5th posture which is rotated by a 3rd predetermined angle from the 4th posture in which both the 4th sensor and the 5th sensor output an ON signal or an OFF signal indicating the detection of the workpiece, and the posture of the holding device with respect to the workpiece is controlled based on the 7th position and the 3rd predetermined angle.

[0120] According to the 13th embodiment, the roll direction attitude of the holding device relative to the workpiece can be controlled using only the on / off signals of two object detection sensors, the fourth sensor and the fifth sensor.

[0121] The program according to the 14th embodiment is a transfer device for moving a workpiece placed on a stocker to a predetermined position, and is a program for operating a transfer device comprising: a holding device for holding the workpiece; a robot that moves the holding device and outputs current attitude information and current position information of the holding device; a first sensor that outputs an on signal or an off signal as detection information for the presence or absence of an object in front of it at a predetermined distance; and a control device, wherein the program causes the control device to perform a movement operation that changes the attitude and position of the holding device when the stocker is in the area in front of the holding device, and calculates the distance between the holding device and the stocker based on the output information of the first sensor before and after the movement operation and the attitude information and position information of the holding device.

[0122] According to the 14th embodiment, distance information between the holding device and the stocker can be acquired using a first sensor that simply outputs an ON or OFF signal depending on the presence or absence of an object. Therefore, a transfer device can be configured without using expensive distance measuring sensors. Furthermore, by determining the position of the stocker based on the distance information, the position of the workpiece placed on the stocker can also be roughly determined. Therefore, the cycle time of the process from holding to transferring the workpiece can be shortened.

[0123] The functions of the elements disclosed herein may be implemented using one or more circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), FPGAs (Field Programmable Gate Arrays), conventional circuits, and / or combinations thereof, which are programmed using one or more programs stored in one or more memories, or otherwise configured to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. A processor may be a programmed processor that executes programs stored in memory. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions individually or in combination with each other, or hardware programmed to perform the enumerated functions individually or in combination with each other. Hardware may be any hardware disclosed herein that is programmed or configured to perform the enumerated functions.

[0124] Computer programs, including computer instructions, are stored in memory. These computer instructions provide logic and routines that enable hardware (e.g., processing circuits or circuits) to perform the methods disclosed herein. These computer programs may be implemented in known formats on computer-readable storage media, computer program products, memory devices, storage media such as CD-ROMs or DVDs, and / or in the memory of FPGAs or ASICs. [Explanation of symbols]

[0125] 1. Workpiece processing system (transfer device) 11. First Robot (Robot) 12. Second Robot 13 Workpiece clamping device 2. Hand unit (part of the holding device) 22 Hand (holding device) 22R, 22L Right hand, Left hand 24. Long-range photoelectric sensor (first sensor) 24R First Long-Range Photoelectric Sensor 24L Second Long-Range Photoelectric Sensor 25 Short-range photoelectric sensors 25R First short-range photoelectric sensor (fourth sensor) 25L Second short-range photoelectric sensor (fifth sensor) 26 Contact Sensor 26P Contact Probe 26R First contact sensor (second sensor) 26L Second contact sensor (third sensor) 30 Stocker 300 Stocker Body 37. Suspension support section (detection piece) 37R Right-hand suspension support section (second detection piece) 37L Left-hand suspension support section (first detection piece) 38 Hanging holes 4. Control device 43 Storage section Double job Xd Distance (distance between the holding device and the stocker) α Pitch angle (predetermined angle)

Claims

1. A transfer device for moving a workpiece placed in a stocker to a predetermined position, A holding device for holding a workpiece, A robot that moves the holding device and outputs the current posture information and current position information of the holding device, A first sensor outputs an ON signal or an OFF signal as detection information for the presence or absence of an object within a predetermined distance ahead, A control device is provided, The control device is When the stocker is located in the front region of the holding device, the robot is made to perform a movement operation that changes the posture and position of the holding device. A transfer device that calculates the distance between the holding device and the stocker based on the output information of the first sensor before and after the movement operation, and the attitude information and position information of the holding device.

2. In the transfer device according to claim 1, The first sensor is mounted on the holding device, The control device, when the stocker is located in the front region of the holding device, controls the robot sequentially, The holding device is in a first position and first orientation relative to the stocker, and the first sensor outputs a first signal, which is either the ON signal or the OFF signal. The holding device is in a second position tilted by a first predetermined angle from the first position, and the first sensor outputs a second signal different from the first signal. The holding device moves relative to the stocker to a second position different from the first position while maintaining the second posture, and the first sensor outputs a first signal, forming a state in which A transfer device that calculates the distance between the holding device and the stocker based on distance information between the first position and the second position and the first predetermined angle.

3. In the transfer device according to claim 2, The control device is a transfer device that calculates the distance xd between the holding device and the stocker using the following formula, where d is the distance between the first position and the second position and α is the first predetermined angle. xd = d / sinα

4. In the transfer device according to claim 1, The stocker includes a stocker body and a detection piece positioned at a specific location on the stocker body. The first sensor is mounted on the holding device, The control device, when the stocker is located in the front region of the holding device, controls the robot sequentially, The holding device is in a third position in the opposing region of the stocker body, and the first sensor outputs either the ON signal or the OFF signal, The holding device moves to a fourth position different from the third position, and the first sensor outputs a fourth signal different from the third signal. The holding device moves to a fifth position which is the region opposite the detection piece, and the first sensor outputs the third signal, forming a state in which A transfer device that determines the type of the stocker based on first position information, which is the position information of the fourth position, and second position information, which is the position information of the fifth position.

5. In the transfer device according to claim 4, The detection piece includes a first detection piece and a second detection piece arranged spaced apart from each other. The first position information is information about the height of the top of the stocker, The second position information is information about the distance between the first detection piece and the second detection piece. The transfer device further includes a storage unit that stores type information relating the type of the stocker, the position information of the first detection piece and the second detection piece, and the height information of the top of the stocker. The control device is a transfer device that determines the type of the stocker by referring to the first position information, the second position information, and the type information.

6. In the transfer device according to claim 5, A transfer device in which the first detection piece and the second detection piece are a pair of suspension support parts having suspension holes in the stocker.

7. In the transfer device according to any one of claims 1 to 6, The system further includes a second sensor and a third sensor that include a contact probe and output an ON signal or an OFF signal as detection information regarding whether or not the contact probe is in contact with an object. The second sensor and the third sensor are spaced apart from each other, and their respective contact probes are mounted on the holding device with the same forward projection height. The control device, when a workpiece mounted on the stocker is present in the front region of the holding device, controls the robot to sequentially: The holding device is in a state where the contact probe of either the second sensor or the third sensor is in contact with the workpiece, and The holding device is in a fourth position, which is rotated by a second predetermined angle from the third position, and in which the contact probes of both the second sensor and the third sensor are in contact with the workpiece. A transfer device that controls the attitude of the holding device relative to the workpiece based on the sixth position and the second predetermined angle.

8. In the transfer device according to any one of claims 1 to 6, In addition to the first sensor, the system further includes a fourth sensor and a fifth sensor that output an ON signal or an OFF signal as detection information for the presence or absence of an object within a predetermined distance ahead. The fourth sensor and the fifth sensor are mounted on the holding device spaced apart from each other. The control device, when a workpiece mounted on the stocker is present in the front region of the holding device, controls the robot to sequentially: The holding device is in a seventh position in which either the fourth sensor or the fifth sensor outputs an ON signal or an OFF signal indicating the detection of the workpiece, The holding device is in a state where both the fourth sensor and the fifth sensor output an ON signal or an OFF signal indicating the detection of the workpiece, A transfer device that controls the attitude of the holding device relative to the workpiece based on the positional information of the seventh and eighth positions.

9. A transfer device that moves a workpiece placed on a stocker to a predetermined position, and a method for correcting the position of a holding device that holds the workpiece, The transfer device includes a robot that moves the holding device and outputs current attitude information and current position information of the holding device, and a first sensor that outputs an on signal or an off signal as detection information for the presence or absence of an object within a predetermined distance in front of it. The position correction method described above is: When the stocker is located in the front region of the holding device, the robot is made to perform a movement operation that changes the posture and position of the holding device. A method for correcting the position of a workpiece holding device, comprising: calculating the distance between the holding device and the stocker based on the output information of the first sensor before and after the movement operation and the attitude and position information of the holding device.

10. In the method for correcting the position of a workpiece holding device according to claim 9, The first sensor is mounted on the holding device, When the stocker is located in the front region of the holding device, the robot's operation sequentially: The holding device is in a first position and first orientation relative to the stocker, and the first sensor outputs a first signal, which is either the ON signal or the OFF signal. The holding device is in a second position tilted by a first predetermined angle from the first position, and the first sensor outputs a second signal different from the first signal. The holding device moves relative to the stocker to a second position different from the first position while maintaining the second posture, and the first sensor outputs a first signal, forming a state in which A method for correcting the position of a workpiece holding device, which calculates the distance between the holding device and the stocker based on distance information between the first position and the second position and the first predetermined angle.

11. In the method for correcting the position of a workpiece holding device according to claim 9, The stocker includes a stocker body and a detection piece positioned at a specific location on the stocker body. The first sensor is mounted on the holding device, When the stocker is located in the front region of the holding device, the robot's operation sequentially: The holding device is in a third position in the opposing region of the stocker body, and the first sensor outputs either the ON signal or the OFF signal, The holding device moves to a fourth position different from the third position, and the first sensor outputs a fourth signal different from the third signal. The holding device moves to a fifth position which is the region opposite the detection piece, and the first sensor outputs the third signal, forming a state in which A method for correcting the position of a workpiece holding device, which determines the type of the stocker based on first position information, which is the position information of the fourth position, and second position information, which is the position information of the fifth position.

12. In the method for correcting the position of a workpiece holding device according to any one of claims 9 to 11, A second sensor and a third sensor are prepared, each including a contact probe, which outputs an ON signal or an OFF signal as detection information regarding whether or not the contact probe is in contact with an object. The second sensor and the third sensor are spaced apart from each other, and the respective contact probes are mounted on the holding device with the same forward protrusion height. When a workpiece mounted on the stocker is located in the front region of the holding device, the robot's operation sequentially: The holding device is in a state where the contact probe of either the second sensor or the third sensor is in contact with the workpiece, and The holding device is in a fourth position, which is rotated by a second predetermined angle from the third position, and in which the contact probes of both the second and third sensors are in contact with the workpiece. A method for correcting the position of a workpiece holding device, which controls the attitude of the holding device relative to the workpiece based on the sixth position and the second predetermined angle.

13. In the method for correcting the position of a workpiece holding device according to any one of claims 9 to 11, In addition to the first sensor, a fourth sensor and a fifth sensor are prepared that output an ON signal or an OFF signal as detection information for the presence or absence of an object within a predetermined distance ahead. The fourth sensor and the fifth sensor are mounted on the holding device spaced apart from each other. When a workpiece mounted on the stocker is located in the front region of the holding device, the robot's operation sequentially: The holding device is in a seventh position in which either the fourth sensor or the fifth sensor outputs an ON signal or an OFF signal indicating the detection of the workpiece, The holding device is in a state where both the fourth sensor and the fifth sensor output an ON signal or an OFF signal indicating the detection of the workpiece, A method for correcting the position of a workpiece holding device, which controls the attitude of the holding device relative to the workpiece based on the position information of the seventh and eighth positions.

14. A transfer device for moving a workpiece placed in a stocker to a predetermined position, A holding device for holding a workpiece, A robot that moves the holding device and outputs the current posture information and current position information of the holding device, A first sensor outputs an ON signal or an OFF signal as detection information for the presence or absence of an object within a predetermined distance ahead, A program for operating a transfer device comprising a control device, The control device, When the stocker is located in the front region of the holding device, the robot is made to perform a movement operation that changes the posture and position of the holding device. A program that calculates the distance between the holding device and the stocker based on the output information of the first sensor before and after the movement, and the attitude information and position information of the holding device.

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