Robot control device, robot control method, and robot control program

Abstract

To provide a robot control device, a robot control method and a robot control program which can set control parameters corresponding to work contents.SOLUTION: A robot control device comprises a control part that makes a robot perform work. The control part determines control parameters on the basis of a table which regulates a correspondence relation between work contents of the work which is performed by the robot and levels of control parameters for the robot. The table includes, as the control parameters, command follow-up performance showing performance of following-up of the robot to a position command and an operation completion determination reference showing a reference for determining operation completion of the robot, which can change a level of the command follow-up performance and a level of the operation completion determination reference respectively.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a robot control device, a robot control method, and a robot control program.

Background Art

[0002] Industrial robots need to operate according to the work of each operator. However, since the work content varies depending on the operator, the parameters for operating the robot are generally set as general-purpose values that can widely correspond to the entire work area (the movable range of the robot) as initial values. In this way, setting general-purpose parameters has the advantage that the robot can operate in the same way over the entire work area. Conversely, it is difficult to locally improve the accuracy, such as increasing the accuracy of the robot operation in a specific work area. In view of this point, Patent Document 1 discloses a robot control device capable of setting dedicated parameters for a specific work area.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, depending on the type of work performed by the robot, the control parameters required by the operator, such as whether to prioritize speed or vibration suppression, differ. Therefore, the robot control device is required to set control parameters that meet the operator's demands. It is difficult for the robot control device of Patent Document 1 to address this point.

Means for Solving the Problems

[0005] The robot control device of the present invention is a robot control device having a control unit for causing a robot to perform a task, The control unit determines the control parameters based on a table that defines the correspondence between the content of the task to be performed by the robot and the level of the robot's control parameters. The table includes, as control parameters, command tracking ability, which indicates the robot's ability to follow position commands, and operation termination criteria, which indicate the criteria for determining the end of the robot's operation. A robot control device characterized by being able to change the level of command tracking and the level of the operation completion determination criterion.

[0006] The robot control method of the present invention determines the control parameters based on a table that defines the correspondence between the work to be performed by the robot and the level of the robot's control parameters. The table includes, as control parameters, command tracking ability, which indicates the robot's ability to follow position commands, and operation termination criteria, which indicate the criteria for determining the end of the robot's operation. A robot control method characterized by the ability to change the level of command tracking and the level of the operation completion determination criterion.

[0007] The robot control program of the present invention determines the control parameters based on a table that defines the correspondence between the work to be performed by the robot and the level of the robot's control parameters. The table includes, as control parameters, command tracking ability, which indicates the robot's ability to follow position commands, and operation termination criteria, which indicate the criteria for determining the end of the robot's operation. A robot control program characterized by the ability to change the level of command tracking and the level of the operation completion determination criterion. [Brief explanation of the drawing]

[0008] [Figure 1]This is a perspective view showing the overall configuration of a robot system according to a preferred embodiment. [Figure 2] This is a diagram of a table. [Figure 3] This is a graph showing the speed of the control parameters. [Figure 4] This graph shows the command tracking performance of the control parameters. [Figure 5] This graph shows the criteria for determining the termination of control parameter operation. [Figure 6] This graph shows the criteria for determining the termination of control parameter operation. [Modes for carrying out the invention]

[0009] The robot control device, robot control method, and robot control program of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

[0010] Figure 1 is a perspective view showing the overall configuration of a robot system according to a preferred embodiment. Figure 2 is a diagram showing a table. Figure 3 is a graph showing the speed of the control parameters. Figure 4 is a graph showing the command tracking performance of the control parameters. Figure 5 is a graph showing the criteria for determining the end of operation of the control parameters. Figure 6 is a graph showing the criteria for determining the end of operation of the control parameters.

[0011] The robot system 1 shown in Figure 1 includes a robot 2, a robot control device 3 that controls the driving of the robot 2, and a display device 4 and an input device 5 connected to the robot control device 3.

[0012] ≪Robot 2≫ Robot 2 is a horizontal articulated robot (SCARA robot) and is used for various tasks such as holding, transporting, assembling, and inspecting workpieces such as electronic components. However, the application of Robot 2 is not particularly limited. Furthermore, Robot 2 is not limited to a horizontal articulated robot; for example, it may be a 6-axis vertical articulated robot.

[0013] The robot 2 has a base 21 fixed to the floor surface and a robot arm 22 connected to the base 21. The robot arm 22 has a first arm 221 whose base end is connected to the base 21 and is rotatable about a first axis J1 with respect to the base 21, and a second arm 222 whose base end is connected to the tip of the first arm 221 and is rotatable about a second axis J2 parallel to the first axis J1 with respect to the first arm 221. A working head 24 is provided at the tip of the second arm 222.

[0014] The working head 24 has a spline nut 241 and a ball screw nut 242 coaxially arranged at the tip of the second arm 222, and a spline shaft 243 inserted through the spline nut 241 and the ball screw nut 242. The spline shaft 243 is rotatable about a third axis J3, which is the central axis thereof, with respect to the second arm 222, and is movable up and down in the direction along the third axis J3. The third axis J3 is parallel to the first axis J1 and the second axis J2.

[0015] A payload 26 for mounting an end effector 25 is provided at the lower end of the spline shaft 243. The end effector 25 to be mounted on the payload 26 is not particularly limited and can be appropriately selected according to the work content. In this embodiment, a hand for sucking and gripping an object is used.

[0016] An inertial sensor 27 is arranged on the payload 26, and can detect the acceleration and angular velocity applied to the tip of the robot arm 22.

[0017] In addition, a drive device 231 for rotating the first arm 221 around the first axis J1 with respect to the base 21 is provided inside the base 21. Further, inside the second arm 222, there are provided a drive device 232 for rotating the second arm 222 around the second axis J2 with respect to the first arm 221, a drive device 233 for rotating the spline nut 241 to rotate the spline shaft 243 around the third axis J3, and a drive device 234 for rotating the ball screw nut 242 to move the spline shaft 243 up and down in the direction along the third axis J3.

[0018] Each of the drive devices 231, 232, 233, and 234 includes a motor M as a drive source, a controller C for controlling the drive of the motor M, and an encoder E for detecting the rotation amount of the motor M, and drives the motor M by servo control that feeds back the output of the encoder E.

[0019] ≪Robot control device 3≫ The robot control device 3 has, for example, a control unit 30 that independently controls the drives of the drive devices 231, 232, 233, 234 and the end effector 25 based on a position command Sd from a host computer (not shown) to cause the robot 2 to perform a predetermined operation.

[0020] The robot control device 3 is composed of, for example, a computer and has a processor for processing information, a memory communicably connected to the processor, and an external interface for connecting to an external device. A robot control program Pt executable by the processor is stored in the memory, and the processor reads the robot control program Pt stored in the memory and executes the control method described below.

[0021] In order to operate robot 2, it is necessary to pre-set various control parameters required for controlling robot 2, such as the range of motion, speed, command tracking ability, and operation completion criteria of robot arm 22. In the field of robotics, it is common for manufacturers to appropriately set these control parameters at the time of shipment, taking into consideration safety, operability, etc. However, the content of the work to be performed by robot 2 differs depending on the operator, and the optimal control parameters also differ depending on the work content. Therefore, it is common for manufacturers to set general-purpose control parameters as initial values ​​so that they can be widely applied to various tasks.

[0022] However, general-purpose control parameters may not provide sufficient precision for the tasks required by the operator. Therefore, the robot control device 3 stores the control parameters as a table T and allows the control parameters to be changed upon request from the operator. This makes it possible to operate the robot 2 with control parameters that meet the operator's requirements.

[0023] As shown in Figure 2, the table T includes two types of operations: transporting the object W and assembling the object W. By including both transporting and assembling operations, it can cover most of the tasks performed by the robot 2. Therefore, the robot control device 3 is highly convenient. While the assembly operations are not particularly limited, examples include attaching the object W to other parts by screwing, threading, fitting, etc.; forming holes in the object W with a drill, etc.; and deforming the object W by embossing, bending, etc.

[0024] Furthermore, the table T includes a first transport operation for transporting objects W weighing less than a predetermined weight, and a second transport operation for transporting objects W weighing more than or equal to the predetermined weight. This allows for the subdivision of the transport operation, making it easier to set control parameters that are more specialized for the operator's work. The predetermined weight can be set based on the characteristics of the robot 2, particularly its payload capacity, and can be, for example, 50% of its payload capacity.

[0025] Furthermore, Table T sets appropriate control parameters for the first and second transport operations and assembly. The control parameters include speed, command tracking ability, and operation completion criteria, each of which can be selected from three levels: "high," "medium," and "low." In other words, Table T defines the correspondence between the work content and the control parameter levels. However, the number of levels is not particularly limited; there may be two, four or more, or it may be virtually stepless.

[0026] The speed included in the control parameters represents the movement speed of the tip of the robot arm 22. As shown in Figure 3, a higher level indicates a higher speed of the robot arm 22. Therefore, a higher speed level shortens the time Δt1 it takes for the robot 2 to reach the target position P1 from its current position P0. The speed includes at least one of absolute velocity, acceleration, deceleration, angular acceleration, and angular deceleration.

[0027] Furthermore, command tracking performance indicates the robot 2's ability to follow the position command Sd. As shown in Figure 4, a higher level indicates better tracking of the robot 2 to the position command Sd. Therefore, a higher level of command tracking performance results in a smaller difference Δp between the position based on the position command Sd during movement to the target position P1 and the actual position, and a shorter time Δt1 for the robot arm 22 to reach the target position P1 from its current position P0.

[0028] Furthermore, the operation termination criteria indicate the criteria for determining the end of one operation of the robot 2. The operation is determined to be complete when the amplitude of the residual vibration (hereinafter also referred to as "residual vibration") remaining after the robot arm 22 reaches the target position P1 falls below a predetermined value. In other words, as shown in Figure 5, the higher the level of the operation termination criteria, the smaller the amplitude and the longer the time Δt2 from when the robot arm 22 reaches the target position P1 until the operation termination is determined.

[0029] The method for detecting the actual position and residual vibration of the robot arm 22 is not particularly limited. For example, it can be detected based on the output of the inertial sensor 27. Alternatively, it can be detected based on the output from the encoders E of the drive units 231, 232, 233, and 234. Such detection methods allow for easy and accurate detection of the actual position and residual vibration of the robot arm 22.

[0030] Thus, the work time Δt required for one operation of robot 2 is determined by the sum of Δt1, the time it takes to reach the target position P1 from the current position P0, and Δt2, the time it takes from reaching the target position P1 until the operation is deemed complete. In other words, Δt = Δt1 + Δt2. Note that as the speed and command tracking level are increased, the speed of robot 2 increases, shortening time Δt1, while residual vibration increases, tending to lengthen time Δt2. Conversely, as the speed and command tracking level are decreased, the speed of robot 2 decreases, lengthening time Δt1, while residual vibration decreases, tending to shorten time Δt2.

[0031] Furthermore, the criteria for determining the end of operation are not limited to the amplitude of residual vibration as described above; operation may also be determined to have ended when the difference Δp between the target position P1 and the actual position falls below a predetermined value. In other words, as shown in Figure 6, the higher the level of the operation termination criteria, the smaller the difference Δp and the longer the working time Δt. This detection method also allows for easy and accurate detection of the actual position and residual vibration of the robot arm 22.

[0032] Depending on the nature of the work, it may be preferable to prioritize work time Δt over positional accuracy. In this case, it is preferable to increase the level of speed and command tracking performance and lower the level of the operation completion judgment criterion. Conversely, depending on the nature of the work, it may be preferable to prioritize positional accuracy over work time Δt. In this case, it is preferable to lower the level of speed and command tracking performance and increase the level of the operation completion judgment criterion. Thus, the preferred control parameters differ depending on the nature of the work.

[0033] In the first transport operation, a high operating speed is often required. Therefore, it is effective to increase both the speed and command tracking levels. This shortens the work time Δt, allowing the transport operation to be repeated many times at short time intervals. In addition, in the first transport operation, high positional accuracy is often required when gripping the object W and when placing the gripped object W. Therefore, it is effective to have a reasonably high level of the operation completion judgment criterion while avoiding an excessively long work time Δt. Based on the above, as shown in Figure 2, the control parameters for the first transport operation are initially set to speed "high", command tracking "medium", and operation completion judgment criterion "medium".

[0034] In the second transport operation, the weight of the object W is heavier than in the first transport operation, so high positional accuracy is often not required. Therefore, it is preferable to lower the level of the operation completion criterion to shorten the work time Δt. Also, since the effect of residual vibration is small, it is preferable to increase the levels of speed and command tracking ability to shorten the work time Δt. Accordingly, as shown in Figure 2, the control parameters for the second transport operation are initially set to speed "high", command tracking ability "high", and operation completion criterion "low".

[0035] In assembly work, positional deviations directly lead to a decrease in assembly accuracy, so high command tracking performance is often required. Therefore, increasing the level of command tracking performance is effective. This reduces the difference Δp between the position command Sd and the actual position, allowing assembly work to be performed with excellent accuracy. In addition, in assembly work, it is effective to lower the speed level and move robot 2 slowly in order to improve assembly accuracy. Furthermore, in assembly work, it is effective to increase the level of the operation completion judgment criterion and have robot 2 perform the next operation with less residual vibration in order to improve assembly accuracy. Based on the above, as shown in Figure 2, the control parameters for assembly work are initially set to speed "low", command tracking performance "high", and operation completion judgment criterion "high".

[0036] The table T has been explained above. The robot control device 3 determines control parameters based on this table T. Typically, it determines control parameters by comparing the table T with the work content received from the operator. The robot control device 3 displays a graphic interface on a display device 4 such as a monitor, and the operator selects work content via this graphic interface through input from the input device 5. When work content is received from the operator via the graphic interface, the robot control device 3 sets the control parameters of the selected work content as the control parameters of the robot 2.

[0037] However, the method for determining the control parameters is not particularly limited. For example, the robot control device 3 may select the work content based on the operation program created by the operator and set the control parameters of the selected work content as the control parameters of the robot 2.

[0038] Furthermore, for the transport operation, for example, the operator may select one of the first or second transport operations based on the weight of the object W input via a graphic interface, and the control parameters of the selected operation may be set as the control parameters of the robot 2. Alternatively, the robot 2 may actually transport the object W, measure the weight of the object W based on the output from the inertial sensor 27 at that time, select one of the first or second transport operations based on the measurement result, and set the control parameters of the selected operation as the control parameters of the robot 2.

[0039] With this type of robot control device 3, appropriate control parameters can be set for each task. Therefore, each task can be performed efficiently. Furthermore, by simply selecting the desired task or a task similar to the desired task from a set of pre-set tasks, the control parameters suitable for that task are automatically set. This allows even operators with insufficient knowledge of robot control to easily set appropriate control parameters for each task.

[0040] As mentioned above, the robot control device 3 has pre-set preferred control parameters for each of the first and second transport operations and assembly operations. However, some operators may want to fine-tune each of the control parameters to achieve their desired work. Therefore, the robot control device 3 can change the level of each of the control parameters, namely speed, command tracking ability, and work completion criteria, for each operation stored in the table T, to either "high," "medium," or "low," based on the operator's request.

[0041] The method of modification is not particularly limited, but for example, the operator can use the input device 5 to request a change in the level of each control parameter via the graphic interface displayed on the display device 4. The robot control device 3 changes the level of each parameter in response to the operator's request. With this configuration, control parameters can be set that are more specific to the operator's work content. Therefore, the work content requested by the operator can be achieved more reliably.

[0042] In particular, in this embodiment, each control parameter can be selected from three levels: "high," "medium," and "low," so even operators with insufficient knowledge of robot control can intuitively and easily change the control parameters. Note that the robot control device 3 may automatically change the control parameters based on the work results of the robot 2.

[0043] The robot system 1 has been described above. The robot control device 3 of this robot system 1 has a control unit 30 that causes the robot 2 to perform tasks. The control unit 30 determines the control parameters based on a table T which defines the correspondence between the content of the task to be performed by the robot 2 and the level of the robot 2's control parameters. The table T also includes, as control parameters, a command tracking ability that indicates how well the robot 2 follows a position command Sd, and an operation completion determination criterion that indicates the criteria for determining when the robot 2 has finished moving. The levels of the command tracking ability and the operation completion determination criterion can be changed.

[0044] This allows each task included in Table T to be performed with appropriate control parameters. Furthermore, since the command tracking level and the operation completion judgment level can be changed, control parameters can be set that are more specialized for the operator's work. As a result, the operator's desired work can be achieved more reliably.

[0045] Furthermore, as mentioned above, Table T also includes the speed of Robot 2 as a control parameter, and the speed level can be changed. This allows for the setting of control parameters that are more specific to the operator's task. As a result, the operator's desired task can be performed more reliably.

[0046] Furthermore, as mentioned above, the table T includes both a transport operation to move the object W and an assembly operation to assemble the object W. This allows it to cover most of the tasks performed by robot 2. Therefore, it becomes a highly convenient robot control device 3.

[0047] Furthermore, as mentioned above, the table T includes, as part of its transport operation, a first transport operation for transporting objects weighing less than a predetermined weight, and a second transport operation for transporting objects weighing more than or equal to the predetermined weight. This allows for the subdivision of the transport operation, making it easier to set control parameters that are more specialized for the operator's work. The predetermined weight can be set based on the characteristics of the robot 2, particularly its payload capacity, and can be, for example, 50% of its payload capacity.

[0048] Furthermore, as mentioned above, the operation termination criterion is based on the difference Δp between the target position P1 based on the position command Sd and the actual position. The higher the level of the operation termination criterion, the smaller the difference Δp. This allows for the transport and assembly operations to be performed with appropriate control parameters.

[0049] Furthermore, as mentioned above, the operation termination criteria are based on the amplitude of residual vibration; the higher the level of the operation termination criteria, the smaller the amplitude. This allows for the transport and assembly operations to be performed with appropriate control parameters.

[0050] As mentioned above, the robot control method determines the control parameters based on Table T, which defines the correspondence between the work to be performed by the robot 2 and the levels of the robot 2's control parameters. Table T also includes, as control parameters, command tracking ability, which indicates how well the robot 2 follows a position command Sd, and operation completion criteria, which indicates the criteria for determining when the robot 2 has finished moving. The levels of command tracking ability and operation completion criteria can be changed.

[0051] This allows each task included in Table T to be performed with appropriate control parameters. Furthermore, since the command tracking level and the operation completion judgment level can be changed, control parameters can be set that are more specialized for the operator's work. As a result, the operator's desired work can be achieved more reliably.

[0052] As mentioned above, the robot control program Pt determines the control parameters based on table T, which defines the correspondence between the tasks to be performed by robot 2 and the levels of the robot 2's control parameters. Table T also includes, as control parameters, command tracking ability, which indicates how well robot 2 follows position commands Sd, and operation completion criteria, which indicate the criteria for determining when robot 2 has finished its operation. The levels of command tracking ability and operation completion criteria can be changed.

[0053] This allows each task included in Table T to be performed with appropriate control parameters. Furthermore, since the command tracking level and the operation completion judgment level can be changed, control parameters can be set that are more specialized for the operator's work. As a result, the operator's desired work can be achieved more reliably.

[0054] Although the robot control device, robot control method, and robot control program of the present invention have been described above based on the illustrated embodiments, the present invention is not limited thereto, and the configuration of each part can be replaced with any configuration having a similar function. Furthermore, any other components may be added to the present invention. [Explanation of Symbols]

[0055] 1...Robot system, 2...Robot, 21...Base, 22...Robot arm, 221...First arm, 222...Second arm, 231...Drive unit, 232...Drive unit, 233...Drive unit, 234...Drive unit, 24...Work head, 241...Spline nut, 242...Ball screw nut, 243...Spline shaft, 25...End effector, 26...Payload, 27...Inertial sensor, 3...Robot control device, 30...Control unit, 4...Display device, 5...Input device, C...Controller, E...Encoder, J1...First axis, J2...Second axis, J3...Third axis, M...Motor, P0...Current position, P1...Target position, Pt...Robot control program, Sd...Position command, T...Table, W...Object, Δt...Work time, Δt1...Time, Δt2...Time, Δp...Difference

Claims

1. A robot control device having a control unit for causing a robot to perform a task, The control unit determines the control parameters based on a table that defines the correspondence between the content of the task to be performed by the robot and the level of the robot's control parameters. The table includes, as control parameters, command tracking performance, which shows the difference between the position based on the position command and the actual position, and operation termination criteria, which shows the criteria for determining the end of the robot's operation. The level of command tracking and the level of the operation termination determination criterion can be changed, respectively. A robot control device characterized in that the higher the level of command tracking, the smaller the difference between the position based on the position command during movement to the target position and the actual position.

2. The table further includes the robot's speed as the control parameter, The robot control device according to claim 1, which can change the level of the speed.

3. The robot control device according to claim 1 or 2, wherein the table includes, as part of the work content, a transport operation for transporting an object and an assembly operation for assembling the object.

4. The robot control device according to claim 3, wherein the table further includes, as the transport operation, a first transport operation for transporting objects less than a predetermined weight and a second transport operation for transporting objects of a predetermined weight or greater.

5. The aforementioned operation termination criteria are based on the difference between the target position based on the position command and the actual position. The robot control device according to any one of claims 1 to 4, wherein the higher the level of the operation termination determination criterion, the smaller the difference.

6. The aforementioned criteria for determining the end of operation are based on the amplitude of residual vibration, The robot control device according to any one of claims 1 to 4, wherein the amplitude is smaller the higher the level of the operation termination determination criterion.

7. The control parameters are determined based on a table that defines the correspondence between the tasks to be performed by the robot and the levels of the robot's control parameters. The table includes, as control parameters, command tracking performance, which shows the difference between the position based on the position command and the actual position, and operation termination criteria, which shows the criteria for determining the end of the robot's operation. The level of command tracking and the level of the operation termination determination criterion can be changed, respectively. A robot control method characterized in that the higher the level of command tracking, the smaller the difference between the position based on the position command during movement to the target position and the actual position.

8. The control parameters are determined based on a table that defines the correspondence between the tasks to be performed by the robot and the levels of the robot's control parameters. The table includes, as control parameters, command tracking performance, which shows the difference between the position based on the position command and the actual position, and operation termination criteria, which shows the criteria for determining the end of the robot's operation. The level of command tracking and the level of the operation termination determination criterion can be changed, respectively. A robot control program characterized in that the higher the level of command tracking, the smaller the difference between the position based on the position command during movement to the target position and the actual position.

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