JP6445114B2 - Work conveying method system having external force monitoring function - Google Patents

Description

  The present invention relates to a transfer system for transferring a workpiece by a robot.

  In order to prevent the robot from coming into contact with surrounding objects or workers and causing a serious accident, the robot has an external force monitoring function for monitoring the force or torque (hereinafter referred to as “external force”) received by the robot from the outside. Robot systems are known. In such a robot system, safety is ensured by stopping the robot when the detected external force exceeds a predetermined threshold. It is particularly important to take such safety measures in the case of a human cooperative robot in which the robot shares a work space with the worker.

  The external force acting on the robot is detected by a force sensor provided at the base of the robot, for example. Specifically, the external force is calculated by subtracting the force (gravity and inertial force) caused by the robot itself when no external force is acting from the detection value of the force sensor.

  In the case of a robot used for the purpose of holding a workpiece and transporting it to a predetermined position, when the workpiece is held, the detection value of the force sensor changes due to the influence of the workpiece. Therefore, in order to monitor the external force, it is necessary to consider the influence of the workpiece. Specifically, the forces (gravity and inertial force) acting on the robot due to the work are calculated by setting the work mass, the center of mass, and the inertia matrix as work parameters. Then, the external force is calculated by further subtracting the acting force caused by the workpiece from the detection value of the force sensor.

  FIG. 7A to FIG. 7C are diagrams illustrating modes when the workpiece 110 is held and transported by the robot 100 according to the related art. The robot 100 includes a hand 102 at the tip of an arm so that the work 110 can be held by the hand 102. The robot 100 includes a force sensor 104 that detects a force acting on the robot 100 at the base.

  FIG. 7A shows the robot 100 positioned at a position where the hand 110 can be held by the hand 102. The hand 102 is in the open position and is separated from the work 110 in the horizontal direction. Therefore, the workpiece 110 is supported only by the workpiece support 120.

  FIG. 7B shows the robot 100 that holds the workpiece 110 by moving the hand 102 in the horizontal direction. The workpiece 110 is placed on the workpiece support 120 as in the state of FIG. 7A. Therefore, the workpiece 110 is still supported only by the workpiece support 120.

  FIG. 7C shows the robot 100 whose position and posture have been changed so that the hand 102 moves upward in the vertical direction. At this time, the workpiece 110 is not in contact with the workpiece support 120. Therefore, the workpiece 110 is supported only by the hand 102 and thus the robot 100.

  In the following description with reference to FIGS. 7A to 7C, it is assumed that the mass of the robot 100 is 200 kg and the mass of the workpiece 110 is 20 kg. For simplicity, consider when the robot 100 is stationary. That is, the inertial force generated when the robot 100 or the workpiece 110 moves is ignored.

  In the state of FIG. 7A, the robot 100 is not in contact with the workpiece 110, and the detection value of the force sensor 104 is not affected by the workpiece 110. Therefore, when no external force is acting, the detection value of the force sensor 104 is equal to the mass of the robot 100 and is 200 kg. In this case, the external force is calculated by subtracting the mass (= 200 kg) of the robot 100 from the detection value (= 200 kg) of the force sensor 104, and becomes 0 kg. Since the external force is not actually acting, it can be said that the calculated value (0 kg) of the external force is accurate.

  In the state of FIG. 7B, the hand 102 applies a force in the horizontal direction so as to hold the workpiece 110, but does not apply a force in the vertical direction. Therefore, when no external force is acting, the detection value of the force sensor 104 is equal to the mass of the robot 100 and is 200 kg.

  On the other hand, since the robot 100 holds the workpiece 110, the external force is calculated in consideration of the influence of the workpiece 110 according to the workpiece parameter. That is, the external force is calculated by subtracting the mass of the robot 100 (200 kg) and the mass of the workpiece 110 (20 kg) from the detection value (200 kg) of the force sensor 104, and becomes −20 kg. In this case, since the external force is not actually acting, the calculated value (−20 kg) of the external force is inaccurate. Therefore, in such a case, the external force acting on the robot 100 cannot be accurately detected.

  In the state of FIG. 7C, the detection value of the force sensor 104 is 220 kg. When the mass of the robot 100 (200 kg) and the mass of the workpiece 110 (20 kg) are subtracted from the detection value (220 kg) of the force sensor 104, the external force becomes 0 kg. Accordingly, in this state, the external force acting on the robot 100 can be accurately detected.

  As described above, in the conventional method, the external force is accurately measured in the process from the time when the workpiece is held (see FIG. 7B) to the time when the workpiece is supported only by the robot (see FIG. 7C). The intended external force monitoring function does not work.

  Patent Document 1 discloses a robot control device that maintains a stationary state of a robot when the robot holds an object or releases the holding state. According to this related technology, it is possible to prevent the robot from operating unexpectedly when switching parameters due to a change in the holding state of the object.

International Publication No. 2012/077335

  However, in the related art disclosed in Patent Document 1, safety in the process from holding a workpiece until the workpiece is supported only by a robot is not considered.

  Therefore, there is a need for a transport system that can prevent a contact accident and ensure safety in the process from when the robot holds the workpiece to when it supports the workpiece.

According to the first aspect of the present application, there is a transport system for transporting a workpiece by a robot, the robot having a tool capable of holding the workpiece, a workpiece support for supporting the workpiece before conveyance, and acting on the robot A force detection unit that detects a force or torque to be performed, a parameter switching unit that switches a work parameter so that a force or torque acting on the robot due to the work can be calculated according to a holding state of the work, Based on the force or torque acting on the robot detected by the force detector and the work parameter, an external force calculator for calculating the external force acting on the robot, and the external force calculated by the external force calculator is a threshold value A robot stop unit for stopping the robot when exceeding, and the work held by the tool, And a relative movement unit that moves the work support relative to each other, and the relative movement unit can move the work and the work support relative to each other without changing the position and posture of the robot. A transport system is provided.
According to the second aspect of the present application, in the transport system according to the first aspect, the relative movement unit moves the work support so as to be separated from the work held by the tool.
According to a third aspect of the present application, in the transport system according to the first or second aspect, the relative movement unit moves the tool so that the work held by the tool is separated from the work support. Move.
According to a fourth aspect of the present application, in the transfer system according to any one of the first to third aspects, the tool is a robot hand.

  These and other objects, features and advantages of the present invention will become more apparent by referring to the detailed description of the exemplary embodiments of the present invention shown in the accompanying drawings.

According to the transport system according to the present application, the relative movement unit moves the work and the work support relative to each other, and the robot remains stationary at that time. That is, the robot does not operate in the process from holding the workpiece until the workpiece is supported only by the robot. Therefore, it is possible to reliably prevent the robot from coming into contact with surrounding objects or workers.
In addition, the relative movement between the workpiece and the workpiece support provided by the relative movement unit is a simple operation compared to the operation of the robot. Therefore, the operator can predict the operation of the transport system very easily and can prevent the occurrence of an accident.

It is the schematic which shows the conveyance system which concerns on 1st Embodiment. It is the schematic which shows the conveyance system which concerns on 1st Embodiment. It is a block diagram which shows the function of the conveyance system which concerns on one Embodiment. It is a flowchart which shows the flow of a process of the conveyance system which concerns on one Embodiment. It is the schematic which shows the conveyance system which concerns on 2nd Embodiment. It is the schematic which shows the conveyance system which concerns on 2nd Embodiment. It is the schematic which shows the conveyance system which concerns on 2nd Embodiment. It is the schematic which shows the conveyance system which concerns on 3rd Embodiment. It is the schematic which shows the conveyance system which concerns on 3rd Embodiment. It is a block diagram which shows the function of the conveyance system which concerns on another embodiment. It is the schematic which shows the conveyance system which concerns on related technology. It is the schematic which shows the conveyance system which concerns on related technology. It is the schematic which shows the conveyance system which concerns on related technology.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The components of the illustrated embodiment are appropriately scaled to assist in understanding the present invention. In addition, the same reference numerals are used for the same or corresponding components throughout a plurality of embodiments.

  FIG. 1A and FIG. 1B are schematic views showing a transport system 10 according to the first embodiment. The transfer system 10 includes a robot 20 and a workpiece support 30 that is disposed within a movable range of the robot 20 and that has a workpiece 40 disposed on an upper surface thereof. The robot 20 is, for example, a vertical articulated robot as illustrated.

  In one embodiment, the robot 20 is installed on a force sensor 21 that detects a force acting on the robot 20. The robot 20 has a base 22 attached to the force sensor 21, a body 23 attached to the base 22 so as to be rotatable about a rotation axis extending in the vertical direction, and a body 23 at one end. The lower arm 24 rotatably attached, the upper arm 25 rotatably attached to the lower arm 24 at the other end of the lower arm 24, and the upper arm 25 rotatably attached to the upper arm 25 at the distal end thereof. Wrist 26. The robot 20 is operable such that each joint is driven by a servo motor and has various positions and postures. Since the configuration of the robot 20 is well known, detailed description is omitted in this specification.

  The wrist 26 of the robot 20 is provided with a tool that releasably holds the workpiece 40. In the illustrated embodiment, the tool is a hand 27 that releasably holds the workpiece 40 by opening and closing. The hand 27 is, for example, a fluid pressure hand or an electric hand that is opened and closed by a servo motor. FIG. 1A shows a state in which the workpiece 40 is held by the hand 27 driven in the closing direction.

  The tool capable of holding the workpiece 40 may have a form other than the hand. For example, the tool may be an adsorption-type tool that adsorbs the workpiece 40 using negative pressure or a magnet.

  The workpiece support 30 includes a pedestal 31 fixed to the floor surface, a support part 32 extending away from the pedestal 31, and a support column 33 provided between the pedestal 31 and the support part 32. I have. The support part 32 has a table-like form, so that the workpiece 40 can be placed on the support part 32. The support column 33 can be moved up and down in the vertical direction by the motor 34, so that the support portion 32 can move toward or away from the pedestal 31.

  FIG. 1B shows a state in which the support pillar 33 is moved downward and the support portion 32 of the work support 30 is separated from the work 40. That is, in the state of FIG. 1B, the work 40 is supported by the hand 27, and the robot 20 receives gravity acting on the work 40. As described above, according to the present embodiment, since the support portion 32 that is movable in the vertical direction is provided, the workpiece 40 can be separated from the workpiece support 30 without changing the position and posture of the robot 20.

  FIG. 2 is a block diagram illustrating functions of the transport system 10 according to an embodiment. As illustrated, the transport system 10 includes a robot 20, a work support 30, and a control device 50 that controls the robot 20 and the work support 30. The control device 50 includes a command creation unit 51, a force detection unit 52, a parameter switching unit 53, an external force calculation unit 54, a robot stop unit 55, and a relative movement unit 56. The control device 50 is, for example, a general personal computer, and includes a CPU that executes various calculations, a RAM that temporarily stores calculation results of the CPU, a ROM that stores various programs and parameters, a mouse, and a keyboard. And the like, a display device for displaying various information, and the like. In one embodiment, a control device that controls the robot 20 and a control device that controls the workpiece support 30 may be provided separately.

  The command creation unit 51 creates a command for the robot 20 according to a predetermined robot program 57, for example. The robot 20 operates in accordance with a command from the command creation unit 51. In addition, the command creation unit 51 may create a command in response to an input signal. For example, the command creation unit 51 creates a command to stop the robot 20 in accordance with the stop signal output from the robot stop unit 55. In addition, the command creating unit 51 may be configured to create a command according to information input by an operator operating an input device.

  The force detection unit 52 detects a force acting on the robot 20. The robot 20 according to the embodiment shown in FIGS. 1A and 1B includes a force sensor 21 at the base. Therefore, the force detection unit 52 can detect the force acting on the robot 20 by the force sensor 21. The force detected by the force sensor 21 includes gravity and inertial force acting on the robot 20 itself, in addition to external force acting on the robot 20 from the outside. Further, when the robot 20 holds the workpiece 40, the force sensor 21 further detects the force acting on the robot 20 due to the gravity and inertial force acting on the workpiece 40. In another embodiment, the force sensor 21 may be attached to a part other than the base part of the robot 20, such as the lower arm 24, the upper arm 25, or the wrist 26, or may be incorporated in them. In any case, the force sensor 21 can detect the force acting on the robot 20 on the distal side of the location where the force sensor 21 is attached. In another embodiment, the force detector 52 may be configured to detect torque acting on the robot 20. In this case, a plurality of torque sensors for detecting torque acting on the joint of the robot 20 are provided instead of the force sensor 21.

  The parameter switching unit 53 switches a work parameter used to calculate a force or torque acting on the robot 20 due to gravity and inertial force acting on the work 40 according to the holding state of the work 40. The workpiece parameter includes information on the mass, the center of mass, and the inertia matrix of the workpiece 40. For example, when the workpiece 40 is not held, the parameter switching unit 53 switches the mass, the center of mass, and the inertia matrix of the workpiece 40 to zero. When the workpiece 40 is held, the parameter switching unit 53 acquires the workpiece parameter from the robot program 57 and replaces the current workpiece parameter. In another embodiment, the parameter switching unit 53 may switch the work parameter according to the work parameter input by the operator operating the input device, or the work parameter may be changed according to a signal input from an external device. It may be switched.

  The external force calculator 54 calculates an external force (force or torque) that acts on the robot 20 externally. When the robot 20 holds the workpiece 40, the external force calculator 54 also calculates an external force that acts on the held workpiece 40. The external force calculation unit 54 acts on the robot 20 by subtracting, for example, the force or torque caused by gravity and inertial force acting on the robot 20 when no external force is acting, from the detection value of the force detection unit 52. Calculate the external force. When the robot 20 holds the workpiece 40, the force or torque that acts on the robot 20 due to gravity and inertial force acting on the workpiece 40 when no external force is acting is detected by the force detection unit 52. It is further subtracted from the value.

  The robot stop unit 55 compares the external force calculated by the external force calculation unit 54 with a predetermined threshold value, and outputs a stop signal to the command creation unit 51 when the calculated value of the external force exceeds the threshold value. In response to the stop signal, the command creating unit 51 creates a stop command for stopping the robot 20. In one embodiment, the stop command may include an evacuation command for moving the robot 20 by a predetermined distance in the direction of the external force before stopping the robot 20. In this case, since the robot 20 stops after retreating so that the external force becomes small, the interference state between the robot 20 and surrounding objects or workers can be quickly eliminated. Therefore, a serious accident can be prevented more reliably.

  The relative moving unit 56 relatively moves them so that the positional relationship between the workpiece 40 and the workpiece support 30 (particularly, the support unit 32) changes. For example, in the embodiment shown in FIGS. 1A and 1B, the relative movement unit 56 drives the motor 34 of the work support 30 to move the support unit 32 up and down in the vertical direction, thereby performing a desired relative movement. realizable.

  The operation of the transport system 10 will be described with reference to FIG. FIG. 3 is a flowchart illustrating a processing flow of the transport system 10 according to the embodiment. In step S <b> 301, the robot 20 is moved to a position where the workpiece 40 can be held by the hand 27. That is, the robot 20 is positioned at a position where the workpiece 40 can be held by moving the hand 27 in the closing direction without changing the position and posture of the robot 20.

  Subsequently, in step S302, the hand 27 is driven and the work 40 is held by the hand 27 (see FIG. 1A). For example, a reaction force acting on the hand 27 when the workpiece 40 is held is detected, and it is estimated that the workpiece 40 is held when the reaction force reaches a threshold value. Alternatively, it may be estimated that the holding operation of the workpiece 40 has been completed when the hand 27 has reached a predetermined closing position determined in advance according to the shape of the workpiece 40.

  In step S303, the robot 20 is stopped. When the robot 20 is in a stopped state, for example, the command creation unit 51 limits the creation of a new torque command or current command. Thereby, the position and posture of the robot 20 are maintained. According to the present embodiment, the stopped state of the robot 20 is maintained until immediately before the transfer process is started in step S306.

  In step S304, the relative movement unit 56 causes the workpiece 40 and the workpiece support 30 to move relative to each other so that the workpiece 40 is separated from the workpiece support 30 (see FIG. 1B). For example, as can be seen by comparing FIGS. 1A and 1B, the work 40 is separated from the work support 30 by moving the support portion 32 of the work support 30 downward.

  Subsequently, in step S305, the work parameters are switched so as to correspond to the state where the work 40 is held. By switching the workpiece parameter, the external force calculation unit 54 can calculate the external force in consideration of the force or torque acting on the robot 20 due to the gravity and inertial force acting on the workpiece 40, and as a result, the external force is calculated. It will be possible to calculate accurately. The work parameter is input from, for example, the robot program 57 (see FIG. 2).

  In step S306, the robot 20 is driven, and the workpiece 40 held by the hand 27 is conveyed to a predetermined position, for example, a work table or a conveyor. In the transport process of step S306, the external force monitoring function using the force detection unit 52, the external force calculation unit 54, and the robot stop unit 55 is effective.

The embodiment described above has the following advantages.
(1) The position and posture of the robot are not changed from when the robot holds the workpiece until the workpiece is supported only by the robot. Therefore, it is possible to prevent an accident in which the robot contacts a surrounding object or an operator during these processes.

  (2) The relative movement of the workpiece with respect to the workpiece support is brought about only by the downward movement of the workpiece support independent of the robot. Since the operation of the workpiece support is simpler than when the position and posture of the robot are changed, the operator can accurately predict the operation of the workpiece support. Therefore, for example, it is possible to easily evaluate the risk of occurrence of a contact accident, and it is possible to easily execute safety measures such as temporarily leaving the worker from the workpiece support.

  (3) In the step of moving the robot to a position where the workpiece can be held and the step of transferring the held workpiece to a predetermined position, the external force acting on the robot is monitored, and the robot is stopped as necessary. Therefore, even if the robot is in contact with surrounding objects or workers while the robot is operating, a serious accident can be reliably prevented.

  4A to 4C are schematic views illustrating the transport system 10 according to the second embodiment. In the present embodiment, the support portion 32 of the workpiece support 30 is configured to hold the workpiece 40 in a releasable manner. In other words, the pair of support portions 32 extending in a substantially horizontal direction move toward or away from each other so that the workpiece 40 can be held or released. The support portions 32 are each driven by a motor 34. In another embodiment, the support part 32 may have a configuration that opens and closes by fluid pressure.

  FIG. 4A shows the transfer system 10 in which the robot 20 is positioned to a position where the workpiece 40 can be held. In this state, the workpiece 40 is held by the support portion 32 of the workpiece support 30. That is, the workpiece 40 is supported only by the workpiece support 30. FIG. 4B shows a state in which the work 40 is held by closing the hand 27 of the work 40. In this state, the workpiece 40 is still supported by the workpiece support 30.

  FIG. 4C shows a state where the support portion 32 of the workpiece support 30 is moved away from the workpiece 40. At this time, the workpiece 40 is supported only by the hand 27 and by the robot 20 alone.

  The transfer system 10 according to the present embodiment is the same as that described above except that the workpiece 40 can be separated from the workpiece support 30 by the support portion 32 of the workpiece support 30 moving in the horizontal direction. Acts like a form. Therefore, even the transport system 10 having such a configuration can achieve the advantageous effects (1) to (3) described above.

  FIG. 5A and FIG. 5B are schematic views illustrating the transport system 10 according to the third embodiment. FIG. 6 is a block diagram illustrating functions of the transport system according to the third embodiment. In the present embodiment, unlike the above-described embodiment, the relative movement unit 56 does not move the workpiece support 30, but the position of the hand 27 of the robot 20 can be changed. In other words, the relative moving unit 56 can move the hand 27 in cooperation with the command creating unit 51 configured to create a command for the hand 27.

  As can be seen by comparing FIGS. 5A and 5B, the relative movement unit 56 can extend and contract the support unit 28 of the hand 27 by the command creation unit 51. That is, by reducing the support portion 28, the hand 27 moves upward, so that the work 40 held by the hand 27 is separated from the work support 30.

  Also in the transfer system 10 according to the present embodiment, after the hand 27 holds the workpiece 40, the hand 27 moves upward until the workpiece 40 moves away from the workpiece support 30. The position and posture are not changed. Further, the vertical movement of the hand 27 is simpler than the operation of the robot 20 as in the operation of the work support 30 described with reference to FIGS. 1A and 1B and FIGS. 4A to 4C. . Therefore, even if it is the conveyance system 10 which has such a structure, the advantageous effect (1)-(3) mentioned above is acquired.

  In the present embodiment, the workpiece support 30 is a table-like jig formed so that the workpiece 40 can be placed thereon, but the workpiece support 30 is omitted, and the workpiece 40 is placed directly on the floor surface. May be. Further, when a plurality of workpieces 40 are stacked on each other, another workpiece 40 located below the workpiece 40 to be held acts as a workpiece support. Thus, it should be noted that in the context of the present invention “work support” can be interpreted in various ways.

  Although the present invention has been described with reference to an example in which one of the hand and the workpiece support is operated, the hand and the workpiece support may be moved relative to each other by operating both the hand and the workpiece support. .

  Although various embodiments of the present invention have been described above, those skilled in the art will recognize that the functions and effects intended by the present invention can be realized by other embodiments. In particular, the constituent elements of the above-described embodiments can be deleted or replaced without departing from the scope of the present invention, and known means can be further added. It is obvious to those skilled in the art that the present invention can be implemented by arbitrarily combining features of a plurality of embodiments explicitly or implicitly disclosed in the present specification.

DESCRIPTION OF SYMBOLS 10 Transfer system 20 Robot 21 Force sensor 22 Base 23 Torso part 24 Lower arm 25 Upper arm 26 Wrist 27 Hand (tool)
DESCRIPTION OF SYMBOLS 28 Support part 30 Work support body 31 Base 32 Support part 33 Support pillar 34 Motor 40 Work 50 Control apparatus 51 Command preparation part 52 Force detection part 53 Parameter switching part 54 External force calculation part 55 Robot stop part 56 Relative movement part 57 Robot program

Claims (2)

A transfer system for transferring a workpiece by a robot,
A robot with a tool that can hold the workpiece;
A workpiece support that supports the workpiece before transfer;
A force detector for detecting a force or torque acting on the robot;
A parameter switching unit that switches a work parameter so that a force or torque acting on the robot due to the work can be calculated according to the holding state of the work;
An external force calculation unit that calculates an external force acting on the robot based on the force or torque acting on the robot detected by the force detection unit and the work parameter;
A robot stop unit that stops the robot when the external force calculated by the external force calculation unit exceeds a threshold;
The workpiece held by the tool, and a relative movement unit that moves the workpiece support relative to each other, and
The workpiece held by the tool without changing the position and posture of the robot in the process from holding the workpiece by the relative movement unit until the workpiece is supported only by the robot. Moving the workpiece support so as to be separated from
Conveying system.   The transport system according to claim 1, wherein the tool is a robot hand.

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