Robot control system

Abstract

To adjusts a relative position of a movable robot with respect to a target.SOLUTION: A robot control system 1 comprises: a hand part 11 having a plurality of electromagnets 10; a robot 12 that moves the hand part 11; a movable carrier 13 to which a base end of the robot 12 is fixed; and a control part 15 that controls the robot 12 so that the hand part 11 is moved. The control part 15 switches the robot 12 into an external force following-up mode while moving the hand part 11 to a vicinity of a target 20 having a plurality of magnetization objects 21 to be magnetized by the plurality of electromagnets 10, respectively; obtains a relative positional relation between the movable carrier 13 and the target 20, using a position and an attitude of the hand part 11 of a time point when the plurality of electromagnets 10 respectively magnetize the plurality of magnetization objects 21; and controls the robot 12 in a position control mode using the relative positional relation. This configuration enables the robot control system to control the robot highly accurately.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a robot control system for controlling a movable robot.

Background Art

[0002] In order for a movable robot to perform highly accurate work, it is necessary to perform more accurate positioning of the robot. Therefore, for example, in a robot that can be transported by an automated guided vehicle, highly accurate positioning is performed by inserting a positioning pin into a hole provided on the floor surface (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the method described in Patent Document 1 can perform highly accurate positioning of a movable robot, it is necessary to prepare a special pedestal or provide a positioning hole on the floor surface for this purpose, resulting in a problem of high cost.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a robot control system that can realize calibration for alignment between a movable robot and a target with a simple configuration.

Means for Solving the Problems

[0006] To achieve the above object, a robot control system according to one aspect of the present invention includes a hand unit having two or more electromagnets, a robot for moving the hand unit, a mobile cart to which the proximal end side of the robot is fixed, and a control unit for moving the hand unit by controlling the robot. The control unit switches the robot to an external force following mode with the hand unit moved to the vicinity of a target having two or more magnetic attachment targets to which the two or more electromagnets are respectively magnetically attached, and uses the position and orientation of the hand unit when the two or more electromagnets are respectively magnetically attached to the two or more magnetic attachment targets to obtain the relative positional relationship between the target and the mobile cart, and controls the robot in a position control mode using the relative positional relationship.

Advantages of the Invention

[0007] According to the robot control system according to one aspect of the present invention, the relative positional relationship between the mobile cart and the target can be obtained with a simple configuration, and the robot can be controlled with higher accuracy using the same.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6

Best Mode for Carrying Out the Invention

[0009] Hereinafter, the robot control system according to the present invention will be described using embodiments. In the following embodiments, components and steps with the same reference numerals are the same or corresponding, and repeated descriptions may be omitted. The robot control system according to the present embodiment can perform highly accurate calibration for aligning the position of the mobile cart and the target by magnetically attaching two or more electromagnets of the hand part and two or more magnet-attaching targets of the target while the robot on the mobile cart is in the external force following mode, thereby obtaining the relative positional relationship between the mobile cart and the target.

[0010] FIG. 1 is a block diagram showing the configuration of a robot control system 1 according to the present embodiment. The robot control system 1 according to the present embodiment includes a hand part 11, a robot 12 for moving the hand part 11, a mobile cart 13 to which the proximal end side of the robot 12 is fixed, a storage part 14 in which teaching data is stored, and a control part 15 for controlling the robot 12 using the teaching data.

[0011] The hand part 11 includes electromagnets 10a and 10b. When the electromagnets 10a and 10b are not particularly distinguished, they may be referred to as electromagnet 10. The same applies to other configurations. In the present embodiment, the case where the hand part 11 has two electromagnets 10 will be mainly described, but the number of electromagnets 10 of the hand part 11 may be two or more, and the number is not limited. For example, the hand part 11 may have three or more electromagnets 10.

[0012] As an example, when the hand part 11 holds the target 20, two electromagnets 10a and 10b may be provided on the surface in contact with the target 20. The on / off control of the electromagnet 10 may be performed by the control part 15. Also, the two or more electromagnets 10 may be, for example, strong enough to hold the target 20.

[0013] The target 20 is used to calibrate the alignment of the carriage 13 using the hand unit 11, and for example, it may be an object to be held by the hand unit 11. In the present embodiment, the case where the target 20 is an object to be held by the hand unit 11 will be mainly described. In this case, the target 20 may be, for example, an object to be transported by the robot 12, or a component to be assembled by the robot 12, etc. In addition, in FIG. 1, the case where the target 20 is placed on the floor surface is shown, but the target 20 may be placed on, for example, a shelf or a table.

[0014] The target 20 has two or more magnetizable objects 21 to which two or more electromagnets 10 are magnetically attached respectively. In the present embodiment, the case where the target 20 has two magnetizable objects 21a and 21b that are magnetically attached to two electromagnets 10a and 10b respectively will be mainly described. The magnetizable object 21 may be, for example, any one of an electromagnet, a permanent magnet, and a ferromagnetic material. When the magnetizable object 21 is a ferromagnetic material, it is preferable that there is no ferromagnetic material other than the magnetizable object 21 around the magnetizable object 21 of the target 20. In the present embodiment, the case where the magnetizable object 21 is a permanent magnet will be mainly described. Also, as an example, the magnetizable object 21 may be provided on the surface of the target 20 that contacts the hand unit 11 when the hand unit 11 holds the target 20. When the magnetizable object 21 is an electromagnet, the electromagnet may be turned on and off manually, for example, or may be turned on and off by wireless communication by the robot control system 1. In the latter case, for example, the electromagnet that is the magnetizable object 21 may be turned on only when it is desired to exert a magnetic force between the electromagnet 10 and the magnetizable object 21.

[0015] As an example, the hand part 11 may have two electromagnets 10a and 10b as shown in FIG. 2A, and the target 20 may have two magnetizable objects 21a and 21b as shown in FIG. 2B. Note that FIGS. 2A and 2B are views of the hand part 11 and the target 20, respectively, from a direction perpendicular to the contact surfaces of both when the two electromagnets 10a and 10b and the two magnetizable objects 21a and 21b are magnetically attached. In the present embodiment, the case where the contact surfaces of the two electromagnets 10a and 10b and the two magnetizable objects 21a and 21b are on the same plane when they are magnetically attached to each other will be mainly described. Also, the electromagnets 10a and 10b in the hand part 11 and the magnetizable objects 21a and 21b in the target 20 are preferably arranged such that, for example, when viewed from a direction perpendicular to their contact surfaces in a situation where they are magnetically attached, the electromagnet 10a overlaps the magnetizable object 21a and the electromagnet 10b overlaps the magnetizable object 21b. As an example, the distance between the electromagnets 10a and 10b and the distance between the magnetizable objects 21a and 21b may be the same on their arrangement surfaces. It is assumed that the same applies when the number of the electromagnets 10 or the magnetizable objects 21 is three or more.

[0016] The robot 12 moves the hand part 11. The hand part 11 may be attached to the tip of the robot 12 as shown in FIG. 1. The robot 12 may be, for example, a robot having a plurality of arms connected by joints driven by a motor. This robot may be, for example, a vertical articulated robot or a horizontal articulated robot. Also, the robot 12 may be, for example, a Cartesian robot having a plurality of linear axes combined at right angles. The robot 12 may be, for example, for transporting the target 20, for performing an assembly operation using the target 20, or for performing other operations. Also, the base end side of the robot 12 is fixed to a movable carriage 13. Therefore, the robot 12 is movable.

[0017] The mobile cart 13 is a cart for moving the robot 12. The mobile cart 13 may be moved manually, for example, or may have a moving mechanism such as a traveling means for moving the mobile cart 13. The traveling means may have, for example, a plurality of wheels and a driving means for driving at least a part of the plurality of wheels. In the present embodiment, this case will be mainly described. Further, the mobile cart 13 having a moving mechanism may move autonomously or may move in response to an instruction from a user or the like. In the former case, the mobile cart 13 may have, for example, a movement control unit for controlling the moving mechanism. The movement control unit may move the mobile cart 13 near the target 20 by controlling the moving mechanism, for example. The control of this moving mechanism may be, for example, a control for moving the mobile cart 13 along a predetermined path.

[0018] In the storage unit 14, teaching data in the local coordinate system of the target 20 is stored. This teaching data may be teaching data regarding the work performed by the robot 12, for example, the conveyance work of the target 20, the assembly work using the target 20, or other work. Further, in the storage unit 14, information other than the teaching data may be stored, for example. For example, in the storage unit 14, the position and posture of the hand unit 11 in the local coordinate system of the target 20 when two or more electromagnets 10 of the hand unit 11 and two or more magnetic attachment targets 21 of the target 20 are magnetically attached to each other may be stored.

[0019] The process of storing information such as teaching data in the storage unit 14 is not limited. For example, information may be stored in the storage unit 14 via a recording medium, information transmitted via a communication line or the like may be stored in the storage unit 14, or teaching data acquired by the teaching operation of the robot 12 may be accumulated in the storage unit 14 by the control unit 15. The storage unit 14 is preferably realized by a non-volatile recording medium, but may be realized by a volatile recording medium. The recording medium may be, for example, a semiconductor memory, a magnetic disk, an optical disk, or the like.

[0020] The control unit 15 moves the hand unit 11 by controlling the robot 12. For example, the control unit 15 may control the robot 12 so that the hand unit 11 approaches the target 20 in order to hold the target 20 by the hand unit 11. Further, for example, when the target 20 is held by the hand unit 11, the control unit 15 may control the robot 12 to move the target 20 to a desired position. Further, the control unit 15 may switch the on / off state of the electromagnet 10 by switching the energization and non-energization of the electromagnet 10 provided in the hand unit 11. Further, when the magnetically adherable object 21 of the target 20 is an electromagnet, the control unit 15 may, for example, switch the on / off state of the electromagnet.

[0021] In addition, the control unit 15 may switch the operation mode of the robot 12 between an external force following mode and a position control mode. The external force following mode is an operation mode in which the hand unit 11 is moved by an external force. This external force may be, for example, a force generated when the robot is pushed by hand, or a force attracted by a magnetic force. This external force may be, for example, an attractive force due to a magnetic force acting between two or more electromagnets 10 provided in the hand unit 11 and two or more magnet-attracting objects 21 provided in the target 20. When the control unit 15 controls the robot 12 in the external force following mode, for example, it may generate torque in the motors that drive the respective axes of the robot 12 so as to cancel the friction of each axis. Also, as an example, when the control unit 15 controls in the external force following mode, it may control each axis of the robot 12 so as to generate a force that corrects the gravity acting on each axis of the robot 12, the reaction generated by the operation of the front-rear axis, and the Coriolis force. By doing so, when an external force is applied to the hand unit 11, even if the external force is small, the hand unit 11 will be moved according to the external force. This external force following mode is a known mode used, for example, in lead-through teaching of a robot, and a detailed description thereof will be omitted. The position control mode is an operation mode for moving the hand unit 11 attached to the robot 12 to an arbitrary position by driving each axis by the motors of the robot 12. When the control unit 15 controls the robot 12 in the position control mode, for example, it may calculate the angles of the respective joints by inverse kinematics from the desired position and orientation of the hand unit 11, and control the motors so that each joint has the calculated angle, etc., to move the hand unit 11 to the desired position and orientation. This position control mode is a known mode used, for example, when performing operations such as conveyance and assembly using a robot, and a detailed description thereof will be omitted.

[0022] When the control unit 15 acquires the relative positional relationship between the target 20 and the mobile cart 13, the robot 12 may be switched to the external force following mode with the hand unit 11 moved to the vicinity of the target 20 having two or more magnetic attachment targets 21. The accuracy regarding the movement of the hand unit 11 to the vicinity of the target 20 is not limited. Before or after such switching to the external force following mode, two or more electromagnets 10 may be turned on. Note that the position in the vicinity of the target 20, which is the movement destination of the hand unit 11, may be a predetermined position, for example. This position is preferably in the vicinity of two or more magnetic attachment targets 21. Also, when the hand unit 11 is present at that position, it is preferable that an attractive force due to the magnetic force of the electromagnet 10 acts between the electromagnet 10 of the hand unit 11 and the magnetic attachment target 21 of the target 20. That is, the vicinity of the magnetic attachment target 21 may be a position close to the magnetic attachment target 21 to such an extent that an attractive force due to the magnetic force acts between the electromagnet 10 and the magnetic attachment target 21.

[0023] With the hand unit 11 of the robot 12 switched to the external force following mode located in the vicinity of the target 20 and two or more electromagnets 10 of the hand unit 11 turned on, an attractive force acts between the electromagnet 10 of the hand unit 11 and the two or more magnetic attachment targets 21 of the target 20. As a result, due to this attractive force, the hand unit 11 moves toward the magnetic attachment target 21, and the two or more electromagnets 10 and the two or more magnetic attachment targets 21 are magnetically attached to each other. That is, the two or more electromagnets 10 of the hand unit 11 and the two or more magnetic attachment targets 21 are magnetically adsorbed. In this way, the hand unit 11 and the target 20 come into contact with each other in a predetermined positional relationship.

[0024] Incidentally, as an example, the position near the target 20, which is the destination of the hand part 11, may be a position where the distances between two or more electromagnets 10 and two or more magnetizable objects 21 magnetically attached to the two or more electromagnets 10 respectively are equal to or less than half of the shortest distance between two of the two or more electromagnets 10. Here, the distance between the electromagnet 10 and the magnetizable object 21 may be, for example, the distance in the plane direction of the contact surface between the two when the two or more electromagnets 10 and the two or more magnetizable objects 21 are magnetically attached. By moving the hand part 11 to such a position, each of the two or more electromagnets 10 can be appropriately magnetically attached to the intended two or more magnetizable objects 21.

[0025] Also, when the magnetizable object 21 magnetically attached to a certain electromagnet 10 is a permanent magnet, it is preferable that when the electromagnet 10 is energized, the polarity on the side of the electromagnet 10 facing the target 20 is opposite to the polarity on the side of the magnetizable object 21 facing the hand part 11. For example, when one is the N pole, it is preferable that the other is the S pole. This is to make a gravitational force act between the two. Also, when the magnetizable object 21 is an electromagnet, it is preferable that the electromagnet of the magnetizable object 21 is energized so as to have the same polarity.

[0026] Also, in FIG. 1 and the like, for the sake of convenience of explanation, the case where a plurality of magnetizable objects 21 protrude from the upper surface of the target 20 is shown, but this is not necessary. As an example, the magnetizable objects 21 may be arranged such that the upper surfaces of the plurality of magnetizable objects 21 and the upper surface of the target 20 are in the same plane.

[0027] The control unit 15 may obtain the relative positional relationship between the target 20 and the mobile carriage 13 by using the position and orientation of the hand unit 11 when two or more electromagnets 10 are magnetically attached to two or more magnetic attachment targets 21 respectively, and control the robot 12 in the position control mode using the relative positional relationship. The relative positional relationship between the target 20 and the mobile carriage 13 may be, for example, the relative positional relationship between the local coordinate system of the target 20 and the local coordinate system of the mobile carriage 13. The relative positional relationship may be, for example, a homogeneous transformation matrix indicating the transformation between the two coordinate systems. The position and orientation of the hand unit 11 when two or more electromagnets 10 are magnetically attached to two or more magnetic attachment targets 21 respectively become predetermined positions and orientations in the local coordinate system of the target 20. This is because the position and orientation of the hand unit 11 are determined according to the arrangement of two or more magnetic attachment targets 21 on the target 20. Further, the control unit 15 can specify the position and orientation of the hand unit 11 in the local coordinate system of the mobile carriage 13 by using the state of the robot 12. The state of the robot 12 may be, for example, the angles of the respective joints when the robot 12 is a vertically articulated robot or a horizontally articulated robot, or may be the positions of the respective linear axes, etc. when the robot 12 is an orthogonal robot. The control unit 15 can calculate the position and orientation of the hand unit 11 in the local coordinate system of the mobile carriage 13, for example, by forward kinematics using the state of the robot 12. Therefore, the control unit 15 uses the predetermined position and orientation of the hand unit 11 in the local coordinate system of the target 20 and the position and orientation of the hand unit 11 in the local coordinate system of the mobile carriage 13 in the state where two or more electromagnets 10 are magnetically attached to two or more magnetic attachment targets 21 respectively, and can obtain the relative positional relationship between the two coordinate systems. The obtained relative positional relationship may be stored in the storage unit 14, for example. In this way, by obtaining the relative positional relationship between the target 20 and the mobile carriage 13, calibration for alignment with the target 20 can be performed on the mobile carriage 13. As a result, for example, even if the position of the mobile carriage 13 is uncertain, work using the robot 12 can be performed with higher accuracy based on the position of the target 20.Note that the control unit 15 may detect, for example, that the electromagnet 10 has magnetically attached to the magnetically attachable object 21 when each axis of the robot 12 stops.

[0028] For example, after two or more electromagnets 10 have magnetically attached to two or more magnetically attachable objects 21 respectively, the control unit 15 may control the robot 12 according to the teaching data stored in the storage unit 14 by using the relative positional relationship between the target 20 and the moving carriage 13. For example, the control unit 15 may convert the teaching data in the local coordinate system of the target 20 stored in the storage unit 14 into teaching data in the local coordinate system of the moving carriage 13 by using the relative positional relationship between the target 20 and the moving carriage 13, and control the robot 12 by using the converted teaching data. More specifically, the control unit 15 converts the position and orientation of the hand unit 11 in the local coordinate system of the target 20 indicated by the teaching data into the position and orientation of the hand unit 11 in the local coordinate system of the moving carriage 13 by using a homogeneous transformation matrix indicating the transformation between the two local coordinate systems, which is the relative positional relationship between the target 20 and the moving carriage 13, and obtains the state of the robot 12 by inverse kinematics from the converted position and orientation of the hand unit 11, and may control the robot 12 so as to achieve the obtained state. The state of the robot 12 may be, for example, the angle of each joint.

[0029] Also, after two or more electromagnets 10 have magnetically attached to two or more magnetically attachable objects 21 respectively, the control unit 15 may, for example, switch the robot 12 to the position control mode and move the hand unit 11 holding the target 20. That is, the operation performed by the robot 12 in the position control mode may be the movement of the target 20. This movement may be performed, for example, for the conveyance of the target 20, or for an assembly operation using the target 20.

[0030] Further, when releasing the holding of the target 20, for example, the control unit 15 may turn off the electromagnet 10, or when the magnetizable object 21 is a permanent magnet, the polarity of the electromagnet 10 may be reversed from that when holding the target 20. Also, when the magnetizable object 21 is also an electromagnet, the electromagnet that is the magnetizable object 21 may be turned on, for example, when the target 20 is held by the hand unit 11, and turned off when the holding is released. The on and off of the electromagnet that is the magnetizable object 21 may be performed, for example, by wireless communication between the control unit 15 and the target 20.

[0031] Note that the storage unit 14 and the control unit 15 may be mounted on the mobile cart 13, for example, or may not be. In the latter case, for example, the control unit 15 may control the robot 12, the electromagnet 10, etc. via wire or wirelessly.

[0032] Next, the operation of the robot control system 1 will be described using the flowchart of FIG. 3. In the flowchart of FIG. 3, the case of transporting the target 20 using the robot control system 1 will be described. Also, it is assumed that the magnetizable object 21 of the target 20 is a permanent magnet.

[0033] (Step S101) The control unit 15 determines whether to transport the target 20. If it is determined to transport the target 20, the process proceeds to step S102, and if not, the process of step S101 is repeated until it is determined to perform the transport. The control unit 15 may determine to transport the target 20, for example, when receiving an instruction to transport the target 20.

[0034] (Step S102) The control unit 15 moves the hand unit 11 near the target 20 by controlling the robot 12. Note that the position of the target 20 may be determined in advance, for example, or may be a position input from the outside.

[0035] (Step S103) The control unit 15 switches the robot 12 to the external force following mode. That is, after this switching, the control unit 15 will control the robot 12 in the external force following mode.

[0036] (Step S104) The control unit 15 turns on two or more electromagnets 10 that the hand unit 11 has. When two or more electromagnets 10 are turned on, an attractive force acts between the two or more electromagnets 10 and two or more magnetic attachment targets 21 of the target 20, and it is assumed that the hand unit 11 moves toward the two or more magnetic attachment targets 21.

[0037] (Step S105) The control unit 15 determines whether the hand unit 11 has stopped. If it has stopped, the process proceeds to step S106. If not, the process of step S105 is repeated until it is determined that the hand unit 11 has stopped. Note that the control unit 15 may determine that the hand unit 11 has stopped, for example, when each axis of the robot 12 no longer changes. Also, when the hand unit 11 has stopped, for example, the hand unit 11 may be in a state of holding the target 20 by the magnetic forces acting between the two or more electromagnets 10 and the two or more magnetic attachment targets 21, respectively.

[0038] (Step S106) The control unit 15 switches the robot 12 to the position control mode. That is, after this switching, the control unit 15 will control the robot 12 in the position control mode.

[0039] (Step S107) The control unit 15 obtains the relative positional relationship between the local coordinate system of the mobile cart 13 and the local coordinate system of the target 20 using the position and orientation of the hand unit 11 at that time. As described above, this relative positional relationship may be a homogeneous transformation matrix indicating the transformation between the two coordinate systems.

[0040] (Step S108) The control unit 15 transports the target 20 to the target position. This transportation to the target position may be performed, for example, using the teaching data stored in the storage unit 14 and the relative positional relationship between the local coordinate system of the mobile carriage 13 and the local coordinate system of the target 20. As an example, the teaching data indicates the movement path of the hand unit 11 in the local coordinate system of the target 20, and the control unit 15 uses the relative positional relationship between the two coordinate systems to obtain the movement path of the hand unit 11 in the local coordinate system of the mobile carriage 13 corresponding to the teaching data, and may control the robot 12 accordingly. Note that the movement path of the hand unit 11 may indicate, for example, changes in the position and posture of the hand unit 11.

[0041] (Step S109) When the transportation of the target 20 to the target position is completed, the control unit 15 releases the holding of the target 20 by the hand unit 11 by turning off the electromagnet 10 of the hand unit 11.

[0042] (Step S110) The control unit 15 moves the hand unit 11 in a direction away from the target 20. Note that the hand unit 11 may be moved to, for example, the initial position. Then, it returns to step S101.

[0043] Note that the order of the processes in the flowchart of FIG. 3 is an example, and if the same result can be obtained, the order of each step may be changed. As an example, the electromagnet 10 may be turned on after it is determined as Yes in step S101, that is, at the start time of transportation. Also, although not included in the flowchart of FIG. 3, the mobile carriage 13 may be moved before the transportation of the target 20 starts or after the transportation of the target 20 is completed. By this movement, for example, the robot 12 may be moved to a desired position. Also, when the processes of steps S101 to S110 are performed, it is preferable that the mobile carriage 13 is stopped. Also, in the flowchart of FIG. 3, the process ends due to a power-off or an interrupt of the end of the process.

[0044] Next, the operation of the robot control system 1 according to the present embodiment will be described using a specific example. In this specific example, it is assumed that the magnetizable object 21 of the target 20 is a permanent magnet. Also, it is assumed that the magnetizable object 21 is disposed on the upper surface of the target 20. Further, in this specific example, it is assumed that the robot 12 has a three-axis attitude axis attached to the tip side of a three-axis orthogonal robot whose base end side is fixed to the mobile cart 13, as shown in FIG. 4.

[0045] In FIG. 4, the robot 12 includes a first rotating means 111 that rotates the second rotating means 112 about a first direction (here, the x-axis direction in the xyz orthogonal coordinate system) in the horizontal plane as a central axis, a second rotating means 112 that rotates the third rotating means 113 about a second direction perpendicular to the first direction as a central axis, a third rotating means 113 that rotates the hand portion 11 about a third direction perpendicular to the first and second directions as a central axis, a first moving portion 121 that is a slide shaft for moving the first rotating means 111 in the first direction, a second moving portion 122 that is a slide shaft for moving the first moving portion 121 in a fourth direction (here, the y-axis direction in the xyz orthogonal coordinate system) in the horizontal plane perpendicular to the first direction, and a third moving portion 123 that is a slide shaft for moving the second moving portion 122 in the vertical direction (here, the z-axis direction in the xyz orthogonal coordinate system). Note that the base end side of the third moving portion 123, that is, the lower end side in FIG. 4, may be fixed to the mobile cart 13 as shown in FIG. 4. As an example, the first moving portion 121 may move the first rotating means 111 in the x-axis direction on the lower surface side of the first moving portion 121. Further, as an example, the second moving portion 122 may move one end of the first moving portion 121 in the x-axis direction in the y-axis direction. Also, as an example, the third moving portion 123 may move one end side of the second moving portion 122 in the z-axis direction. Further, the first to third rotating means 111 to 113 may be configured by a three-axis attitude axis connected by a plurality of joints having the first to third directions as rotation axes, respectively. Note that the xyz orthogonal coordinate system may be the local coordinate system of the mobile cart 13.

[0046] In this specific example, as shown in FIGS. 2A and 2B, the hand part 11 has two electromagnets 10a and 10b, and the target 20 is assumed to have two magnetizable objects 21a and 21b. Also, in this specific example, it is assumed that the position and orientation of the hand part 11 in the local coordinate system of the target 20 when the two electromagnets 10a and 10b of the hand part 11 and the two magnetizable objects 21a and 21b of the target 20 are magnetically attached to each other are stored in the storage unit 14. Further, in this specific example, it is assumed that teaching data for transporting the target 20 from the first position to the second position is stored in the storage unit 14. The teaching data is assumed to be teaching data indicating the movement path of the hand part 11 in the local coordinate system of the target 20.

[0047] First, after the mobile cart 13 is moved near the target 20 existing at the first position, when an instruction to transport the target 20 is input to the robot control system 1, in response to the instruction, the control unit 15 moves the hand part 11 near the target 20 (steps S101, S102). Note that the control unit 15 may move the hand part 11 so that the two electromagnets 10 face the lower surface side, for example, at a position above the target 20, which is a predetermined position.

[0048] Next, the control unit 15 switches the robot 12 to the external force following mode and turns on the two electromagnets 10 (steps S103, S104). In the external force following mode, for example, the first moving part 121 may set the force Fx in the x-axis direction to 0, the second moving part 122 may set the force Fy in the y-axis direction to 0, and the third moving part 123 may set the force Fz in the z-axis direction to M. M may be the total weight of the first to third rotating means 111 to 113, the first and second moving parts 121 and 122, and the hand part 11.

[0049] In the external force following mode, due to the magnetic force between the two electromagnets 10 and the permanent magnets which are the two magnetizable objects 21 of the target 20, the hand part 11 moves in the direction approaching the magnetizable object 21, and finally the two electromagnets 10 magnetize to the two magnetizable objects 21 respectively. In this way, the hand part 11 comes into contact with the target 20 existing at the first position.

[0050] When it is detected that the two electromagnets 10 have magnetized to the two magnetizable objects 21 respectively due to the hand part 11 stopping, the control unit 15 switches the robot 12 to the position control mode (steps S105, S106). Also, the control unit 15 uses the position and orientation of the hand part 11 in the local coordinate system of the mobile cart 13 at that time and the position and orientation of the hand part 11 in the local coordinate system of the target 20 stored in the storage unit 14 to obtain a homogeneous transformation matrix indicating the transformation between the two coordinate systems (step S107).

[0051] Then, the control unit 15 uses the homogeneous transformation matrix to obtain teaching data indicating the movement path of the hand part 11 in the local coordinate system of the mobile cart 13 corresponding to the teaching data indicating the movement path of the hand part 11 in the local coordinate system of the target 20 stored in the storage unit 14, and controls the robot 12 using the obtained teaching data, so as to transport the target 20 held by the hand part 11 by the magnetic force of the two electromagnets 10 from the first position to the second position (step S108). When the transportation of the target 20 to the second position is completed, the control unit 15 turns off the electromagnets 10 to release the adsorption of the target 20 and returns the hand part 11 to a predetermined initial position (steps S109, S110). In this way, a series of processes for transporting the target 20 from the first position to the second position is completed.

[0052] As described above, according to the robot control system 1 according to the present embodiment, in the robot 12 in the external force following mode, two or more electromagnets 10 of the hand unit 11 and two or more magnetizable objects 21 of the target 20 can be magnetically attached to each other, and by acquiring the relative positional relationship between the mobile cart 13 and the target 20 at that time, calibration for aligning the mobile cart 13 and the target 20 can be performed with high precision. Therefore, when the mobile cart 13 is stopped near the target 20, even if the accuracy of the position of the mobile cart 13 is low, the robot 12 can perform more accurate work in the local coordinate system of the target 20. For example, work using the teaching data in the local coordinate system of the target 20 stored in the storage unit 14 can be performed with high accuracy.

[0053] In the present embodiment, after two or more electromagnets 10 are magnetically attached to two or more magnetizable objects 21 respectively, the control unit 15 mainly described the case where the robot 12 is switched to the position control mode and the hand unit 11 holding the target 20 is moved, but this is not necessary. For example, the target 20 may be only used for calibration for aligning the target 20 and the mobile cart 13. In this case, for example, work such as conveyance or assembly using a conveyance target or an assembly target arranged in a predetermined positional relationship with respect to the target 20 may be performed by the robot 12.

[0054] Also, in the present embodiment, among two or more objects to be magnetically attached 21, at least two objects to be magnetically attached 21 may have different polarities. In this case, the two or more objects to be magnetically attached 21 may be, for example, permanent magnets or electromagnets. As an example, when electromagnets 10a and 10b are magnetically attached to objects to be magnetically attached 21a and 21b respectively, the sides of the objects to be magnetically attached 21a and 21b facing the electromagnets 10a and 10b are N poles and S poles respectively, and when the electromagnets 10a and 10b are turned on, the sides facing the objects to be magnetically attached 21a and 21b may be S poles and N poles respectively. By doing so, when the two electromagnets 10 and the two objects to be magnetically attached 21 are magnetically attached, the combination of the magnetically attached electromagnet 10 and the object to be magnetically attached 21 will be uniquely determined, and more accurate alignment between the mobile carriage 13 and the target 20 can be achieved.

[0055] Also, in the present embodiment, the case where two electromagnets 10 and two objects to be magnetically attached 21 are magnetically attached respectively has been mainly described. However, as described above, the hand portion 11 may have three or more electromagnets 10, and the target 20 may have three or more objects to be magnetically attached 21. In this case, it is preferable that the three or more electromagnets 10 are arranged so as not to be rotationally symmetric when viewed from a direction perpendicular to the contact surface between the three or more electromagnets 10 and the three or more objects to be magnetically attached 21 during their respective magnetic attachments. Not being rotationally symmetric may mean, for example, not being rotationally symmetric with respect to any axis perpendicular to the contact surface. By doing so, when the three or more electromagnets 10 and the three or more objects to be magnetically attached 21 are magnetically attached appropriately, their relative positional relationship will be uniquely determined, and calibration for alignment can be performed more accurately.

[0056] In this case, for example, the hand unit 11 may have three electromagnets 10a, 10b, and 10c as shown in FIG. 5A, and the target 20 may have three magnetizable objects 21a, 21b, and 21c as shown in FIG. 5B. Note that FIGS. 5A and 5B are views of the hand unit 11 and the target 20, respectively, from a direction perpendicular to the contact surfaces of both when the three electromagnets 10a, 10b, 10c and the three magnetizable objects 21a, 21b, 21c are magnetically attached. In FIGS. 5A and 5B, the three electromagnets 10 and the three magnetizable objects 21 are arranged so as not to be rotationally symmetric, respectively.

[0057] Also, in the present embodiment, when two or more electromagnets 10 and two or more magnetizable objects 21 are magnetically attached to each other, the control unit 15 may check whether both are properly magnetically attached. For example, although a part of two or more electromagnets 10 and a part of two or more magnetizable objects 21 are magnetically attached, there is a possibility that the other electromagnets 10 and magnetizable objects 21 are not magnetically attached. As an example, when two electromagnets 10a, 10b and two magnetizable objects 21a, 21b are magnetically attached, although the electromagnet 10a and the magnetizable object 21a are magnetically attached, and the electromagnet 10b and the magnetizable object 21b are not magnetically attached, if the relative positional relationship between the mobile cart 13 and the target 20 is obtained assuming that the two electromagnets 10a, 10b and the two magnetizable objects 21a, 21b are properly magnetically attached, the relative positional relationship will be inaccurate. Therefore, the control unit 15 may check whether the two electromagnets 10a, 10b and the two magnetizable objects 21a, 21b are properly magnetically attached.

[0058] In this case, each of the two or more magnetic attachment targets 21 of the target 20 may be an electromagnet whose on and off states are controlled by the control unit 15. Then, after the two or more electromagnets 10 of the hand unit 11 are magnetically attached to the two or more electromagnets that are the magnetic attachment targets 21 of the target 20 respectively, for each set of the electromagnet 10 of the hand unit 11 and the electromagnet that is the magnetic attachment target 21 of the target, by changing at least one of the magnetic forces, it may be confirmed whether the two or more electromagnets 10 of the hand unit 11 and the two or more electromagnets that are the magnetic attachment targets 21 of the target 20 are magnetically attached respectively. The change in the magnetic force may be, for example, the switching of the on and off states of the electromagnet, or the increase or decrease of the magnetic force generated by the electromagnet. Also, for example, the hand unit 11 may have a first sensor for detecting the electromagnetic induction generated in the coil of the electromagnet 10a and a second sensor for detecting the electromagnetic induction generated in the coil of the electromagnet 10b. The first and second sensors may be, as an example, ammeters for detecting the induced current. And when the two electromagnets 10a, 10b and the two magnetic attachment targets 21a, 21b are magnetically attached respectively, the control unit 15, for example, after both are magnetically attached, switches the on and off states of the electromagnet that is the magnetic attachment target 21a one or more times, and when the electromagnetic induction corresponding thereto is detected by the first sensor, it may be determined that the electromagnet 10a and the magnetic attachment target 21a are magnetically attached. Similarly, the control unit 15 may switch the on and off states of the electromagnet that is the magnetic attachment target 21b one or more times, and when the electromagnetic induction corresponding thereto is detected by the second sensor, it may be determined that the electromagnet 10b and the magnetic attachment target 21b are magnetically attached. By doing so, it is possible to confirm whether the two or more electromagnets 10 and the two or more electromagnets that are the magnetic attachment targets 21 are magnetically attached appropriately. For example, even if the on and off states of the electromagnet that is a certain magnetic attachment target 21 are switched, if the induced current generated thereby is not detected in the coil of the electromagnet 10 that is supposed to be magnetically attached to that magnetic attachment target 21, it can be determined that the two are not magnetically attached appropriately. That is, it can be determined that the two or more electromagnets 10 are not magnetically attached to the two or more magnetic attachment targets 21 appropriately.

[0059] Here, the case where the control unit 15 switches the electromagnet on and off has been described. However, as described above, the control unit 15 may change the magnetic force of the electromagnet so that the magnetic force generated by the electromagnet increases or decreases. Then, depending on whether electromagnetic induction corresponding to the change in the magnetic force of the electromagnet is detected, it may be confirmed whether the electromagnet 10 and the magnet-attracting object 21 are magnetically attached. Also, here, the case where electromagnetic induction corresponding to the switching on and off of the electromagnet, which is the magnet-attracting object 21, is detected by a sensor provided on the electromagnet 10 side has been described. However, the sensor may be provided on the electromagnet side of the magnet-attracting object 21. In this case, electromagnetic induction corresponding to the switching on and off of the electromagnet 10 may be detected by a sensor provided on the electromagnet side of the magnet-attracting object 21.

[0060] Here, the case where it is determined whether two or more electromagnets 10 are appropriately magnetically attached to two or more magnet-attracting objects 21 by detecting electromagnetic induction has been described. However, the same determination may be made by other methods. For example, when two electromagnets 10a and 10b and two magnet-attracting objects 21a and 21b are each to be magnetically attached, after both are magnetically attached, the control unit 15 may switch the polarity of one of the electromagnet 10a and the magnet-attracting object 21a to the opposite. The switching may be performed, for example, for a short time such that the positional relationship between the hand unit 11 and the target 20 does not change significantly. Then, when the hand unit 11 vibrates in response to the switching of the polarity, the control unit 15 may determine that the electromagnet 10a and the electromagnet that is the magnet-attracting object 21a are appropriately magnetically attached. Similarly, the control unit 15 may determine whether the electromagnet 10b and the electromagnet that is the magnet-attracting object 21b are appropriately magnetically attached by switching the polarity of one of the electromagnet 10b and the magnet-attracting object 21b to the opposite. In this way, the control unit 15 can confirm whether two or more electromagnets 10 are appropriately magnetically attached to two or more magnet-attracting objects 21.

[0061] Also, when it is confirmed by the above-described processing that two or more electromagnets 10 are not properly magnetically attached to two or more magnetically attachable objects 21, the control unit 15 turns off the electromagnets 10 and the electromagnets that are the magnetically attachable objects 21, and controls the robot 12 in the position control mode to move the hand unit 11 away from the target 20. Then, with the hand unit 11 moved again near the target 20, the robot 12 is switched to the external force following mode, and the electromagnets 10 and the electromagnets that are the magnetically attachable objects 21 are turned on respectively, so that the two or more electromagnets 10 and the two or more magnetically attachable objects 21 may be magnetically attached. In this case, for example, when moving the hand unit 11 near the target 20, the control unit 15 may move the hand unit 11 to a position different from the position where it was moved in the past.

[0062] In addition, in this embodiment, the case where the target 20 is held by the magnetic force of the electromagnet 10 when the hand unit 11 holds the target 20 has been mainly described, but it does not have to be so. The hand unit 11 may further have holding means for holding the target 20, for example, after the electromagnet 10 is magnetically attached to the magnetically attachable object 21. This holding means may be, for example, clamping means for clamping the target 20, or vacuum suction means for sucking the target 20. In this case, after the target 20 is held by the holding means, the electromagnet 10 may be turned off. Also, in this case, the electromagnet 10 may generate a magnetic force that cannot hold the target 20, for example.

[0063] Also, in the present embodiment, the control unit 15 may control, for example, the magnetic forces of two or more electromagnets 10 to weaken as the hand unit 11 approaches the magnetizable object 21. By performing such control, the impact when the hand unit 11 and the target 20 come into contact can be reduced. For example, when the control unit 15 sets the robot 12 to the external force following mode and turns on two or more electromagnets 10, after detecting that the hand unit 11 has started to move due to an external force, the control unit 15 may gradually decrease the power supplied to each of the two or more electromagnets 10 so that the magnetic forces generated by the two or more electromagnets 10 weaken. After the hand unit 11 starts to move due to the magnetic forces generated by the two or more electromagnets 10, the power supplied to the two or more electromagnets 10 may become zero before the two or more electromagnets 10 and the target 20 come into contact, or the energization of the two or more electromagnets 10 may still be performed when they come into contact. In any case, by performing control such that the magnetic forces of the two or more electromagnets 10 weaken as the hand unit 11 approaches the two or more magnetizable objects 21, the impact when they come into contact can be mitigated. For example, the possibility that at least one of them is damaged due to the impact when they come into contact can be reduced. For example, when the hand unit 11 holds the target 20 by the two or more electromagnets 10, the electromagnet 10 may be turned on again after the hand unit 11 comes into contact with the target 20.

[0064] Further, in the present embodiment, as shown in FIG. 6, the robot 12 may further include a force sensor 16 for measuring the force applied to the hand portion 11. The force sensor 16 may be, for example, a three-axis force sensor or a six-axis force sensor. In this case, when controlling the robot 12 in the external force following mode, the control unit 15 may control the robot 12 so that the external force measured by the force sensor 16 becomes zero. The external force measured by the force sensor 16 may be, for example, an external force other than the gravity applied to the hand portion 11. The control unit 15 can identify an external force other than the gravity applied to the hand portion 11, for example, by using the force acquired by the force sensor 16 when the electromagnet 10 is off and the force acquired by the force sensor 16 when the electromagnet 10 is on. Then, when controlling the robot 12 in the external force following mode, the control unit 15 may move the hand portion 11 in the direction of the external force. Further, when the external force following mode continues, the control unit 15 may repeat the movement of the hand portion 11 in the direction of the external force and the identification of the external force.

[0065] Also, in the present embodiment, the case where the robot control system 1 has the storage unit 14 has been mainly described, but it may not be the case. When the robot control system 1 does not have the storage unit 14, the control unit 15 receives, for example, an instruction regarding the position and orientation of the hand portion 11 in the local coordinate system of the target 20, and uses the relative positional relationship between the mobile cart 13 and the target 20 to control the robot 12 according to the received instruction to move the hand portion 11, so that a desired operation according to the instruction may be performed.

[0066] Further, in the above embodiment, each process or each function may be realized by being centrally processed by a single device or a single system, or may be realized by being distributedly processed by a plurality of devices or a plurality of systems.

[0067] In addition, in the above embodiment, each component may be configured by dedicated hardware, or components that can be realized by software may be realized by executing a program. For example, each component can be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. At the time of its execution, the program execution unit may execute the program while accessing a storage unit or a recording medium. Further, the program may be executed by being downloaded from a server or the like, or may be executed by reading a program recorded on a predetermined recording medium (for example, an optical disk, a magnetic disk, a semiconductor memory, etc.). Also, this program may be used as a program constituting a program product. Further, the computer that executes the program may be singular or plural. That is, centralized processing may be performed, or distributed processing may be performed.

[0068] In addition, the above embodiments are examples for specifically implementing the present invention and do not limit the technical scope of the present invention. The technical scope of the present invention is indicated by the claims, not the description of the embodiments, and is intended to include changes within the literal scope of the claims and the scope of equivalent meanings.

Explanation of Reference Numerals

[0069] 1 Robot control system, 10, 10a, 10b, 10c Electromagnets, 11 Hand part, 12 Robot, 13 Mobile cart, 14 Storage unit, 15 Control unit, 20 Target 21, 21a, 21b, 21c Objects to be magnetically attached

Claims

1. A hand part having two or more electromagnets, A robot for moving the hand part, A mobile cart to which the proximal end side of the robot is fixed, A control unit that moves the hand part by controlling the robot, comprising: The control unit switches the robot to an external force following mode with the hand part moved to the vicinity of a target having two or more magnetic attachment targets to which the two or more electromagnets are respectively magnetically attached, and uses the position and orientation of the hand part when the two or more electromagnets are respectively magnetically attached to the two or more magnetic attachment targets to obtain the relative positional relationship between the target and the mobile cart, and controls the robot in a position control mode using the relative positional relationship. A robot control system.

2. Each of the two or more magnetic attachment targets is an electromagnet whose on and off are controlled by the control unit, After the two or more electromagnets of the hand part are respectively magnetically attached to the two or more magnetic attachment targets of the target, the control unit changes at least one magnetic force for each pair of the electromagnet of the hand part and the electromagnet of the magnetic attachment target of the target to confirm whether the two or more electromagnets of the hand part and the two or more electromagnets of the magnetic attachment targets of the target are respectively magnetically attached. The robot control system according to Claim 1.

3. Among the two or more magnetic attachment targets, at least two magnetic attachment targets have different polarities. The robot control system according to Claim 1.

4. The hand part has three or more electromagnets, The target has three or more magnetic attachment targets, The three or more electromagnets are arranged so as not to be rotationally symmetric when viewed from a direction perpendicular to the contact surface between the three or more electromagnets and the three or more magnetic attachment targets during magnetic attachment. The robot control system according to Claim 1.

5. After the two or more electromagnets are respectively magnetically attached to the two or more magnetic attachment targets, the control unit switches the robot to a position control mode and moves the hand part holding the target. The robot control system according to Claim 1.

6. Further comprising a storage unit for storing teaching data in the local coordinate system of the target The robot control system according to any one of claims 1 to 5, wherein the control unit controls the robot according to the teaching data by using a relative positional relationship between the target and the mobile cart.

Images