Robot control system

Abstract

To enable an operator to perform operation as near as possible to a human cooperation robot, when the operator performs operation together with the human cooperation robot.SOLUTION: Object detection means 3 for detecting presence / absence of an object in a detection range S set near a tool 30 is mounted on a robot arm 10, and a determination unit 44 for determining safety on the basis of a detection result of the object detection means 3 is provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a robot control system. [Background technology]

[0002] Collaborative robots (Human Collaborative Robots) are robots that meet the safety requirements set forth in ISO / TS 15066, JIS B 8433-1, and 8433-2 and can work in the same environment as humans. However, because the tools (end effectors) attached to the end of a collaborative robot's arm can be freely replaced by the user, even if the robot itself is safe, if the tool has sharp edges or protrusions, it may pose a risk of harming humans. Furthermore, when a workpiece is grasped with a transport tool attached to the end of a robot arm, the workpiece may become a hazard if it has sharp edges or generates energy due to its weight or kinetic energy due to its movement speed. Therefore, even if the safety of the robot arm itself is assured by meeting the requirements of the above standards, the safety of the tool attached to the end and the workpiece must be considered. Collaborative robots are notable for their ability to work in the same environment as humans without the need for physical protective fences. However, in reality, safeguards are required to prevent interference between the tool and the human.

[0003] As a safety protection measure as described above, the robot control device disclosed in the following Patent Document 1 has a functional safety unit and an object approach detection unit.

[0004] The functional safety unit monitors the detection results related to the robot and ensures safety by bringing the robot to an emergency stop if any abnormality is detected in the monitoring results. For example, a virtual safety fence can be set up in the virtual space set by the functional safety unit, and if the robot arm or the tool or work attached to it comes into contact with the virtual safety fence, the robot can be brought to an emergency stop, thereby ensuring that moving bodies including the tool and workpiece always operate within a specified range (within the virtual safety fence).

[0005] The object approach detection unit is composed of, for example, a light curtain or a laser scanner, and when it detects that an object (person) has approached the robot more than a preset distance, it brings the robot to an emergency stop to ensure safety. In Patent Document 1 listed below, the object approach detection unit is provided on the fixed side (specifically, on the base of the robot system). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-11357 Summary of the Invention [Problem to be solved by the invention]

[0007] In the above-described safety protection measures, the area in which a worker can work is limited to an area that corresponds to the outside of the virtual safety fence set by the functional safety unit and that is outside the detection range of the object approach detection unit. When taking into account the tools and workpieces that are attached to the tip of the robot arm, the area surrounded by the virtual safety fence and the detection range of the object approach detection unit need to be set wider, which further limits the worker's workable area and makes it difficult to fully enjoy the benefits of using a collaborative robot.

[0008] Therefore, an object of the present invention is to enable a worker to work safely as close as possible to the human-cooperative robot when working together with the human-cooperative robot. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a robot control system for controlling a robot having a robot arm with a tool attached to the tip thereof, the system comprising: A robot control system is provided that includes an object detection means attached to the robot arm and that detects the presence or absence of an object within a detection range set near the tool, and a judgment unit that judges safety based on the detection results of the object detection means.

[0010] In this way, by providing the object detection means on the movable robot arm rather than on the fixed side, the detection range of the object detection means moves in accordance with the movement of the robot arm. Therefore, even when the robot arm moves, the detection range can always be set around the tool at the tip of the robot arm. In this way, by continuously generating a detection range that detects the presence or absence of an object (person) near the moving tool, the area that people cannot enter can be minimized compared to when a fixed detection range is set, allowing people to work close to the robot.

[0011] The robot control system includes a drive control unit that controls the drive of the robot arm and a functional safety unit that detects the operation of the robot arm and monitors safety, and the functional safety unit can include the judgment unit. In this case, the detection result by the object detection means is transmitted to the functional safety unit, and the judgment unit provided in the functional safety unit judges safety based on the detection result by the object detection means.

[0012] As described above, when an object detection means is attached to a robot arm, depending on the posture of the robot arm, there is a possibility that part of the robot arm may enter the detection range of the object detection means. In this case, if the object detection means detects the robot arm as an "object," the determination unit will determine that it is "unsafe" and bring the robot arm to an emergency stop. For example, if the movable range of the robot arm is limited so that the robot arm does not enter the detection range of the object detection means, the above-mentioned problem can be avoided, but this will impose restrictions on the work of the robot arm and reduce work efficiency.

[0013] Therefore, it is preferable to be able to mute detection by the object detection unit in the interference area between the detection range and the robot arm. As a result, even if the robot arm enters the detection range of the object detection unit while it is operating, the detection results in these interference areas are not used to determine safety, so the robot arm can continue operating.

[0014] In order to set the detection range of the object detection means close to the moving tool, it is desirable to attach the object detection means as close to the tip of the robot arm (near the tool) as possible. However, the most distal link of a robot arm to which the tool is attached is usually not very large, so it is often difficult to attach the object detection means to this link. Therefore, if the robot arm has a distal link to which the tool is attached and a second link from the tip that is rotatably attached to the distal link, it is preferable to attach the object detection means to the second link from the tip. [Effects of the Invention]

[0015] As described above, the robot control system according to the present invention allows a worker to work in the vicinity of the robot when working in cooperation with the robot. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a side view of the robot and the control device. [Figure 2] FIG. 2 is a side view of the robot. [Figure 3] FIG. 2 is a block diagram of a control device. [Figure 4] FIG. 10 is a view of the tip of the robot arm and the workpiece as viewed from the direction of the rotation axis of the sixth link. [Figure 5] 10 is a side view showing interference between the detection range of the object detection means of the robot and the robot arm. FIG. [Figure 6] 10A and 10B are diagrams conceptually illustrating the detection range of an object detection means and an interference area with a robot arm. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] 1 shows a robot 1 used, for example, in an automobile assembly line. This robot 1 is controlled by a robot control system according to one embodiment of the present invention. This robot control system has a control device 2 and object detection means 3.

[0019] The robot 1 is, for example, a vertical articulated robot, and in this embodiment, as shown in FIG. 2, has a six-axis robot arm 10. The robot arm 10 has a first link 11 to a sixth link 16 arranged in order from a base 20, and a first joint J1 to a sixth joint J6 arranged on the base end side (base 20 side) of each of the links 11 to 16. The first link 11, which is the base end side, is attached to the base 20 via the first joint J1, and a tool 30 is attached to the tip end (opposite the sixth joint J6) of the sixth link 16, which is the tip end side. The tool 30 attached to the sixth link 16 is replaceable, and in this embodiment, a gripper that grips a workpiece W is attached as the tool 30. Note that the robot 1 is not limited to the above, and may be, for example, a vertical articulated robot with axes other than six (e.g., four, five, or seven), a horizontal articulated robot (SCARA robot), a parallel link robot, an orthogonal robot, or the like.

[0020] 3, the control device 2 has a drive control unit 41 and a functional safety unit 42. The drive control unit 41 drives the motors of the first joint J1 to the sixth joint J6 of the robot arm 10 to control the operation of the robot arm 10.

[0021] The functional safety unit 42 monitors for the presence or absence of abnormalities related to functional safety and includes a calculation unit 43 that performs calculations using detection results from the various detection units, a determination unit 44 that monitors the drive control unit 41 and the input state of safety signals from the surrounding area to determine safety, and a command unit 45 that issues commands to the drive unit of the robot arm 10 based on the results of the determination unit 44. The functional safety unit 42 is connected, for example, to a rotation speed detection unit (not shown) that detects the rotation speed of each of the joints J1 to J6 of the robot arm 10. The rotation speeds of each of the joints J1 to J6 detected by each rotation speed detection unit are transmitted to the calculation unit 32, and the calculation unit 43 calculates the position, movement speed, movement direction, etc. of the robot arm 10 using these detection results. Based on this calculation result, the determination unit 44 determines safety, and if it is not safe, the command unit 45 issues commands to the motors of each of the joints J1 to J6 of the robot arm to slow down or stop the robot arm 10, or to cut off power to stop the robot arm 10 depending on the stop mode.

[0022] As described above, the drive control unit 41 and the functional safety unit 42 are provided as separate systems, so that even if the drive control unit 41 fails, safety can be ensured by the functional safety unit 42.

[0023] In this embodiment, an object detection means 3 is connected to the functional safety unit 42. The object detection means 3 detects whether an object is present within a detection range, and may be, for example, a laser scanner or a camera. The object detection means 3 is attached to the robot arm 10, and in this embodiment, is attached to the fifth link 15 (see FIGS. 1 and 2). The object detection means 3 sets a detection range near the tool 30. For example, as shown in FIGS. 1 and 4, a substantially conical detection range S is set that surrounds the entire circumference of the tool 30 and the workpiece W. In this embodiment, the object detection means 3 are provided at two locations on both diametrical sides of the fifth link 15. The detection ranges S1 and S2 of each object detection means 3 form a partial cone shape of 180° or more (approximately 270° in the illustrated example) (see FIG. 4). The circumferential ends of the detection ranges S1 and S2 of each object detection means 3 overlap with each other, thereby setting a detection range S that surrounds the entire circumference of the tool 30. The object detection means 3 is not limited to the above, and for example, the fifth link 15 may be provided with one object detection means capable of setting a detection range around the entire circumference of the tool 30 and the workpiece W. Alternatively, object detection means may be provided at three or more locations around the circumference of the fifth link 15.

[0024] When the robot 1 performs work, the robot arm 10 is operated by driving each of the joints J1 to J6 of the robot arm 10 based on commands from the drive control unit 41 of the control device 2, and the tool 30 and workpiece W are placed at a predetermined position and in a predetermined posture. At this time, the object detection means 3 constantly detects whether or not an object has entered the detection range S, and this detection result is transmitted to the functional safety unit 42 of the control device 2, and the judgment unit 44 judges safety based on this detection result.

[0025] Specifically, if no object is detected within the detection range S, the determination unit 44 determines that it is "safe" and continues the operation of the robot arm 10. On the other hand, if an object is detected within the detection range S, the determination unit 44 determines that it is "unsafe" and restricts the operation of the robot arm 10. For example, the calculation unit 43 calculates the distance between an object that has entered the detection range S and the tool 30 and workpiece W. If the distance between the object within the detection range S and the tool 30 and workpiece W is equal to or greater than a predetermined value, the determination unit 44 determines that "deceleration is required," and the command unit 45 issues a deceleration command to the joints J1 to J6 to reduce the movement speed of the robot arm 10. Furthermore, if the distance between the object within the detection range S calculated by the calculation unit 43 and the tool 30 and workpiece W is less than a predetermined value, the determination unit 44 determines that "stopping is required," and the command unit 45 issues a stop command to the joints J1 to J6 to bring the robot arm 10 to an emergency stop.

[0026] In this embodiment, by providing the object detection means 3 on the robot arm 10, the detection range S of the object detection means 3 can be moved together with the tool 30, and the detection range S can be always set in the vicinity of the tool 30 and the workpiece W. This makes it possible to set the minimum necessary detection range compared to when a fixed detection range (for example, a virtual safety fence) is set, thereby expanding the range in which a person can work and improving workability.

[0027] For example, if the object detection means 3 is provided on a link (e.g., the first link 11) on the base end side of the robot arm 10, the relative movement range of the tool 30 and workpiece W with respect to the object detection means 3 will increase. In this case, the detection range S of the object detection means 3 needs to be set to include the relative movement range of the tool 30 and workpiece W, so the detection range S is widened and the working range of a person is narrowed accordingly.

[0028] In contrast, if the object detection means 3 is provided near the tip of the robot arm 10, the amount of relative movement of the tool 30 and workpiece W with respect to the object detection means 3 will be small, and the detection range S can be narrowed. In particular, if the object detection means 3 is provided on the sixth link 16, which is the tipmost link of the robot arm 10, the amount of relative movement of the tool 30 and workpiece W with respect to the object detection means 3 will be zero. However, since the sixth link 16 usually has a short length (the distance between the sixth joint J6 and the tool 30), it is often difficult to secure a place to attach the object detection means 3. Furthermore, if the object detection means 3 is too close to the tool 30 and workpiece W, it will be difficult to set a detection range S that surrounds the periphery of the tool 30 and workpiece W.

[0029] For the above reasons, in this embodiment, the object detection means 3 is provided on the fifth link 15, which is the second link from the tip. The fifth link 15 is often longer than the sixth link, making it easier to secure a location for attaching the object detection means 3. Furthermore, by providing the object detection means 3 on the fifth link 15, the object detection means 3 is positioned slightly away from the tool 30 and workpiece W, making it easier to set a detection range S that surrounds the tool 30 and workpiece W. Furthermore, when the object detection means 3 is provided on the fifth link 15, the tool 30 and workpiece W move relative to the object detection means 3, but this relative movement is limited to rotation around the rotation axis L6 of the sixth joint J6 (see FIGS. 1, 2, and 4). Therefore, the tool 30 and workpiece W do not move significantly relative to the object detection means 3, making it possible to narrow the detection range S and thereby expand the working range of a person.

[0030] 5, during operation of the robot arm 10, the robot arm 10 itself may enter the detection range S of the object detection means 3 (detection range S2 in the illustrated example). If the judgment unit 44 of the functional safety unit 42 judges that it is "unsafe" based on the detection result, the robot arm 10 will be decelerated or brought to an emergency stop. For example, if the posture of the robot arm 10 is restricted so that the robot arm 10 does not enter the detection range S of the object detection means 3, the above-mentioned problem can be avoided, but work efficiency will decrease.

[0031] Therefore, in this embodiment, detection in the interference area between the detection range S of the object detection means 3 and the robot arm 10 is muted (detection is turned off). Specifically, the calculation unit 43 of the functional safety unit 42 generates a virtual model of the robot arm 10 (hereinafter referred to as the "robot arm model 10'") and sets a virtual detection range S' by the object detection means 3 in this virtual space. Then, the actual movement of the robot arm 10 is detected from the detection results of the rotation speeds of the joints J1 to J6, etc., and this is reflected in the robot arm model 10'. At this time, as shown in FIG. 6(A), detection by the object detection means 3 is muted in the interference area M (scattered area) between the virtual detection range S' and the robot arm model 10'. In other words, the detection result of the object detection means 3 in the interference area between the detection range S and the robot arm 10 is not used as material for safety judgment. Then, after a short time, as shown in FIG. 6(B), when the interference area M changes due to the movement of the robot arm model 10', detection in the interference area M after the change is muted. As described above, the interference area M between the virtual detection range S' and the robot arm model 10' at that time is calculated every minute time, and detection in this interference area M is muted to continuously change the detection range S by the object detection means 3.

[0032] That is, the functional safety unit 42 of the robot 1 continuously (actually, every minute period) determines the self-interference area M, and continuously mutes detection in that interference area. This ensures safety by reliably detecting the approach of the tool 30 and workpiece W with a person, and also suppresses a decrease in productivity due to restrictions on the posture of the robot arm 10 and an increase in the no-entry area for people, and makes it possible to minimize slow operation and stoppage measures to ensure safety.

[0033] The present invention is not limited to the above-described embodiment. Other embodiments of the present invention will be described below, but redundant description of points similar to those of the above-described embodiment will be omitted.

[0034] In the above embodiment, the object detection means 3 is provided on the fifth link 15 of the robot arm 10, but this is not limiting. For example, if it is possible to provide the object detection means 3 on the sixth link 16, this may also be done. Furthermore, if it is possible to set the detection range S by the object detection means 3, the object detection means 3 may be provided on any of the first link 11 to the fourth link 14.

[0035] Furthermore, in the above embodiment, the detection range S is provided continuously around the entire circumference of the tool 30 and the workpiece W, but this is not limited to this, and the detection range S may be provided at multiple locations spaced apart in the circumferential direction, for example.

[0036] Furthermore, in the above embodiment, the tool 30 is a gripping portion, but is not limited to this, and may be, for example, a drill, a nut runner, or a welding tool. [Explanation of symbols]

[0037] 1. Robot 2. Control device 3. Object detection method 10 Robotic Arm 10' Robot Arm Model 11~16 1st link~6th link 20 Foundation 30 Tools 41 Drive control unit 42 Functional Safety Department 43 Arithmetic section 44 Judgment section 45 Command Department J1~J6 1st joint to 6th joint S Detection Range S' Virtual detection range double work

Claims

[Claim 1] A robot control system for controlling a robot having a robot arm with a tool attached to the tip thereof, A robot control system comprising: an object detection means attached to the robot arm, which detects the presence or absence of an object within a detection range set near the tool; and a judgment unit which judges safety based on the detection results of the object detection means.

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