Robot system, control method and control program of robot system

Abstract

To enable an operator of a robot to more easily grasp a finished state of a workpiece.SOLUTION: A robot system 1 includes: a robot arm 2 that holds a polishing tool 4 or a workpiece 3; a force sensor 233 or an encoder 242 that acquires reaction force data 60 related to a reaction force acting on the robot arm 2 due to contact between the polishing tool 4 and the workpiece 3; and the control unit 58. The control unit 58: separates the reaction force data 60 when the polishing tool 4 and the workpiece 3 are relatively moved while being in contact with each other, into a higher-frequency component 61 and a lower-frequency component 62 than a predetermined reference frequency; and causes a display unit 53 to display at least the higher-frequency component 61.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a robot system for performing processing by bringing a processing tool into contact with a workpiece, and a control method and a control program therefor.

Background Art

[0002] In polishing work or deburring work using a robot, there are cases where the feeding operation is performed following the surface shape of the workpiece with the tool pressed against the workpiece (see, for example, Patent Document 1). In this type of robot system, it is useful if the operator of the robot can easily grasp the finished state of the workpiece.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made in view of the above circumstances, and an object thereof is to enable an operator of a robot to more easily grasp the finished state of a workpiece.

Means for Solving the Problems

[0005] The robot system according to the present invention includes: a robot that holds a processing tool or a workpiece; an acquisition unit that acquires reaction force information regarding a reaction force acting on the robot due to contact between the processing tool and the workpiece; a separation unit that separates the reaction force information when the processing tool and the workpiece are relatively moved while being in contact with each other into a high-frequency component and a low-frequency component higher than a predetermined reference frequency; a display control unit that causes at least the high-frequency component to be displayed on a display unit; and is provided with.

Advantages of the Invention

[0006] According to the present invention, an operator of a robot can more easily grasp the finished state of a workpiece.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0009] [Configuration of Robot System] FIG. 1 is a diagram showing a robot system 1 according to the present embodiment. As shown in this figure, the robot system 1 performs polishing of a workpiece (workpiece to be processed) 3 with a polishing tool 4 held by a robot arm 2. More specifically, the robot arm 2 performs a feeding operation (reciprocating operation) along the feeding direction Y while pressing the polishing tool 4 against the workpiece 3 along the pressing direction X. Specifically, the robot system 1 includes a robot arm 2 and a control device 5.

[0010] In this embodiment, the robotic arm 2 is a vertically articulated robot, and includes a base portion 21, a plurality of arms 22, an end effector 23, a plurality of joint portions 24, and a controller 28 (see FIG. 2). However, the robotic arm 2 is not limited to a vertically articulated robot.

[0011] The plurality of arms 22 are connected in series with each other, with the base portion 21 fixed to an environment (e.g., factory floor, arm holding table, etc., not shown) as the base end portion. The end effector 23 is connected to the tip of the plurality of arms 22. A force sensor 233 is provided on the end effector 23 (see FIG. 2). The force sensor 233 detects the load (force) and torque (moment) received by the end effector 23 and outputs them to the controller 28. Note that the force sensor 233 only needs to be able to detect at least one of the load in the pressing direction X and the moment about an axis orthogonal to the pressing direction X. The plurality of joint portions 24 rotatably connect the base portion 21, the plurality of arms 22, and the end effector 23. Each joint portion 24 is provided with a motor 241 that drives the arm 22 (or end effector 23) connected to the tip side of the joint portion 24, and an encoder 242 that detects the position (speed) of this motor 241 and outputs it to the controller 28 (see FIG. 2). The controller 28 controls the operations of each part of the robotic arm 2 based on a control command from the control device 5. Specifically, the controller 28 drives each motor 241 and outputs the information detected by each encoder 242 and force sensor 233 to the control device 5.

[0012] In this embodiment, the polishing tool 4 is a grinding wheel. The polishing tool 4 is held in a predetermined state by the end effector 23 of the robotic arm 2 and pressed against the workpiece 3 during processing. In this embodiment, the workpiece 3 to be polished is a metal plate-like body. The workpiece 3 is fixed substantially horizontally on the support base 31. Note that the shape and material of the workpiece 3 are not particularly limited as long as they can be polished by the polishing tool 4. For example, the surface shape of the workpiece 3 to be polished may include a curved surface with irregularities.

[0013] FIG. 2 is a block diagram showing a schematic control configuration of the robot system 1. As shown in this figure, the control device 5 is a computer that controls the operation of the robot system 1. Specifically, the control device 5 includes an operation unit 52, a display unit 53, a storage unit 56, and a control unit 58.

[0014] The operation unit 52 is an operation means for the user (operator of the robot arm 2) to perform various operations for operating the control device 5, and includes, for example, a pointing device such as a mouse and a keyboard. The display unit 53 is, for example, a liquid crystal display, an organic electroluminescence display, or other display, and displays various information based on a display signal from the control unit 58. Note that the display unit 53 may be a touch panel that also serves as a part of the operation unit 52, or may perform voice output.

[0015] The storage unit 56 is a memory configured to include, for example, a RAM (Random Access Memory) and a ROM (Read Only Memory), stores various programs and data, and also functions as a work area for the control unit 58. In the storage unit 56 of the present embodiment, in addition to an operation program (not shown) for automatically controlling the robot arm 2 to perform a predetermined polishing process on the workpiece 3, a polishing control program 561 for executing a polishing control process (see FIG. 3) described later is stored in advance. Further, the storage unit 56 has a reaction force data storage area 562 for storing data on the reaction force in the pressing direction X described later.

[0016] The control unit 58 is configured to include, for example, a CPU (Central Processing Unit) and controls the operations of each part of the control device 5. Specifically, based on the operation content of the operation unit 52, the control unit 58 causes the display unit 53 to display various information, or expands a program pre-stored in the storage unit 56 and executes various processes in cooperation with the expanded program.

[0017] [Polishing control process] Subsequently, the polishing control process executed during the polishing operation (polishing process) will be described. FIG. 3 is a flowchart showing the procedure of the polishing control process, FIG. 4 is an example of the generated waveform of the reaction force in the pressing direction X received by the robot arm 2 from the workpiece 3, and FIG. 5 is a diagram showing an example of the display on the display unit 53 in the polishing control process.

[0018] The polishing control process is a process that performs predetermined control based on the reaction force received by the robot arm 2 from the workpiece 3 during the polishing operation. This polishing control process is executed by the control unit 58 of the control device 5 reading and expanding the polishing control program 561 from the storage unit 56 in accordance with the start of the polishing operation based on the user operation on the control device 5. The polishing operation is started by expanding a predetermined operation program for automatically controlling the robot arm 2. The polishing control program 561 may be a part of the operation program.

[0019] In the polishing operation of the present embodiment, the robot arm 2 moves in the feed direction Y while pressing the polishing tool 4 against the workpiece 3 to polish the surface of the workpiece 3. More specifically, the robot arm 2 reciprocates between the start point and the end point of a predetermined movement line while generating a substantially constant pressing force by moving the polishing tool 4 following the surface shape of the workpiece 3 by position control.

[0020] As shown in FIG. 3, when the polishing control process is executed, first, the control unit 58 starts the feeding operation of the polishing tool 4 and starts the polishing operation on the surface of the workpiece 3 (step S1). Specifically, the control unit 58 moves the polishing tool 4 to a predetermined machining start position on the workpiece 3 by the robot arm 2 and presses it against the surface of the workpiece 3. Then, in this state, the control unit 58 moves the polishing tool 4 in the feed direction Y to start polishing a predetermined movement line on the surface of the workpiece 3. Here, the "movement line" is the movement locus of the polishing tool 4 on the surface of the workpiece 3 during machining, and its shape is not limited to a straight line. Also, the movement line may be set in advance or may be set by the user each time. Note that the initial value of the position in the pressing direction X (i.e., the pressing force) at the time of the first polishing is set in advance based on, for example, the design data of the workpiece 3 or the like.

[0021] When starting the feeding operation, the control unit 58 detects the reaction force in the pressing direction X (pressing reaction force) acting on the robot arm 2 due to the contact with the workpiece 3 (step S2). Specifically, the control unit 58 detects the pressing reaction force based on the output of the force sensor 233 mounted on the end effector 23 or the encoder 242 of each joint portion 24. Thereby, for example, as shown in FIG. 4, reaction force data 60 regarding the pressing reaction force is obtained. FIG. 4 is an example of the raw waveform of the reaction force data 60 when the polishing tool 4 is moved on a predetermined movement line, and the horizontal axis represents the position on the movement line.

[0022] Next, the control unit 58 separates the reaction force data 60 acquired in step S2 into a low-frequency component lower than the reference frequency and a high-frequency component higher than the reference frequency (step S3). The reference frequency is not particularly limited, but is set in advance based on, for example, the size of the unevenness to be extracted as the high-frequency component.

[0023] Next, as shown in FIG. 5(a), the control unit 58 causes the display unit 53 to display the high-frequency component 61 of the reaction force data 60 acquired in step S3 as information regarding the finished state of the surface of the workpiece 3 (step S4). Since the high-frequency component 61 is due to fine unevenness on the surface of the workpiece 3, it corresponds to the surface roughness of the workpiece 3, that is, information on the finished state.

[0024] Also at this time, the control unit 58 causes the display unit 53 to display the low-frequency component 62 of the reaction force data 60 acquired in step S3, together with the high-frequency component 61, as information regarding the surface shape of the workpiece 3. Since the low-frequency component 62 is obtained by separating the high-frequency component 61 corresponding to the fine unevenness and the like on the surface of the workpiece 3, it corresponds to information on the macroscopic surface shape of the workpiece 3. Note that the low-frequency component 62 depends on the setting of the reference frequency, but can be said to be the nominal value of the pressing reaction force, and thus is displayed as "pressing reaction force" in the display examples of FIGS. 5 and 6. Also, in this step, it is sufficient that at least the high-frequency component 61 is displayed.

[0025] When the feed on the moving line is completed, the control unit 58 determines whether or not the high-frequency component 61 of the reaction force data 60 on the moving line is within a predetermined threshold value Th (step S5). That is, in this step, based on the high-frequency component 61, the finishing state of the polishing of the workpiece 3 is determined. The threshold value Th is set in advance according to the desired surface roughness of the workpiece 3, but may be adjusted by the user as appropriate.

[0026] In step S5, when it is determined that the high-frequency component 61 is not within the threshold value Th (step S5; No), the control unit 58 adjusts the position teaching (position control) in the pressing direction X based on the low-frequency component 62 (step S6). Thereafter, the control unit 58 shifts the process to step S1 described above and starts a new feed operation on the same moving line as the previous time.

[0027] Specifically, in step S6, the control unit 58 adjusts the position of the polishing tool 4 in the pressing direction X on the moving line so that the distribution across the moving line of the low-frequency component 62 approaches a constant value. That is, the target trajectory of the polishing tool 4 in the pressing direction X is corrected such that the pressing force is weakened at the position where the low-frequency component 62 was large in the previous feeding operation and the pressing force is strengthened at the position where the low-frequency component 62 was small. As a result, the polishing tool 4 can be moved along a trajectory that more closely follows the surface shape of the workpiece 3, and the pressing force can be made closer to being uniform. A new (for example, the second) feeding operation on the moving line is executed according to the corrected target trajectory, and the reaction force data 60 at that time is acquired (updated), and its high-frequency component 61 and low-frequency component 62 are displayed (steps S1 to S4). At this time, as shown in FIG. 5(b), a high-frequency component 61 that is smaller than the previous one and a low-frequency component 62 that is closer to being constant are obtained. If the high-frequency component 61 still does not fall within the threshold Th, the target trajectory of the polishing tool 4 in the pressing direction X is corrected again based on the low-frequency component 62, and the process proceeds to step S1. Similarly, based on the low-frequency component 62 in the (n - 1)-th feeding operation, the correction of the target trajectory of the polishing tool 4 in the pressing direction X in the n-th time is repeated. That is, as shown in FIG. 5(c), steps S1 to S6 are repeated until the high-frequency component 61 falls within the threshold Th. When the high-frequency component 61 falls within the threshold Th, the finished state of the surface of the workpiece 3 on the moving line reaches the desired state, and the polishing of the moving line is completed.

[0028] In step S5, when it is determined that the high-frequency component 61 falls within the threshold Th (step S5; Yes), the control unit 58 determines whether a predetermined polishing operation has been completed (step S7). The control unit 58 determines that the predetermined polishing operation has been completed, for example, when the polishing of all the processing target areas of the workpiece 3 has been completed. In step S7, when it is determined that the predetermined polishing operation has not been completed (step S7; No), the control unit 58 changes the moving line (step S8), and then transfers the process to step S1 described above, and executes polishing on the new moving line. On the other hand, when it is determined that the polishing operation has been completed (step S7; Yes), the control unit 58 ends the polishing control process and ends the polishing operation.

[0029] [Technical effects of the present embodiment] As described above, according to the present embodiment, when the reaction force data 60 when the polishing tool 4 and the workpiece 3 are relatively moved while being in contact with each other is separated into a high-frequency component 61 and a low-frequency component 62, at least the high-frequency component 61 is displayed on the display unit 53. The high-frequency component 61 of the reaction force data 60 is due to fine unevenness on the surface of the workpiece 3 and the like, and corresponds to information on the finished state of the workpiece 3. Therefore, the operator of the robot arm 2 can grasp the finished state of the workpiece 3 by visually recognizing the high-frequency component 61 displayed on the display unit 53. Therefore, the operator of the robot arm 2 can more easily grasp the finished state of the workpiece 3.

[0030] Also, according to the present embodiment, the position of the polishing tool 4 held by the robot arm 2 is adjusted based on the low-frequency component 62 of the reaction force data 60. The low-frequency component 62 of the reaction force data 60 corresponds to information on the surface shape of the workpiece 3. Therefore, for example, by controlling the robot arm 2 so that the distribution over the movement line of the low-frequency component 62 approaches a constant value, surface following control following the surface of the workpiece 3 can be suitably executed. Therefore, it is possible to suitably equalize the pressing force even with respect to the surface of the workpiece 3 having unevenness. As a result, polishing unevenness such as over-grinding can be suppressed and the polishing quality can be improved. Also, the pressing force can be controlled only by position control of the robot arm 2. Therefore, for example, in a method of controlling the pressing force by force control, it is necessary to perform position control when bringing the tool close to the workpiece and switch to force control when the tool comes into contact with the workpiece. However, in the present embodiment, such control switching is not necessary. Therefore, the setting and adjustment of the switching operation can be made unnecessary, and the control system can be configured simply.

[0031] Further, according to the present embodiment, the low-frequency component 62 of the reaction force data 60 is displayed on the display unit 53 together with the high-frequency component 61. As a result, the operator can more easily grasp the changes and distribution of the pressing force and the progress of the work.

[0032] Further, according to the present embodiment, based on whether or not the high-frequency component 61 of the reaction force data 60 falls within a predetermined range, the finished state of the polishing of the workpiece 3 is determined. As a result, the finished state of the workpiece 3 can be simply and quantitatively evaluated without the need to actually measure the surface roughness or the like.

[0033] [Others] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments. For example, in the above embodiment, in step S6 of the polishing control process, the control unit 58 adjusts the position in the pressing direction X based on the low-frequency component 62. However, the position in the pressing direction X may be manually adjusted by the user. In this case, for example, when the user operates the operation unit 52 during work to switch to the manual mode, as shown in FIG. 6, the control unit 58 displays the slider 53a and the adjustment handle 53b on the display unit 53. The slider 53a is displayed on the vertical axis of the low-frequency component 62, and the target value of the pressing force can be changed, for example, by a drag operation of the user. The adjustment handle 53b is displayed on the curve of the low-frequency component 62, and the distribution of the pressing force on the moving line can be changed, for example, by a drag operation of the user. As a result, the user can manually adjust the pressing force appropriately, for example, while observing the finished state of the high-frequency component 61. Note that the method of manual adjustment by the user is not limited to the above example. For example, a UI (User Interface) other than a slider or a handle may be used, or numerical input or the like may be relied upon.

[0034] Further, in the above embodiment, the case where the workpiece 3 is fixed and the polishing tool 4 is handled by the robot arm 2 is illustrated. However, the polishing tool 4 may be fixed and the robot arm 2 may handle the workpiece 3.

[0035] In addition, in the above-described embodiment, the case where the robot arm 2 reciprocates the polishing tool 4 along a predetermined movement line (movement locus) for polishing has been exemplified. However, the present invention can be suitably applied not only to processing that repeatedly feeds a predetermined movement line but also to any contact processing that involves bringing a processing tool into contact with a workpiece for processing.

[0036] Also, in the above-described embodiment, "polishing (processing)" of polishing a workpiece with a polishing tool has been described as an example. However, the present invention can be widely applied to processing that involves bringing a workpiece into contact with a processing tool, and is also applicable to, for example, "grinding (processing)". Further, the present invention can be widely applied to teaching devices of various robots (processing machines). For example, the robot according to the present invention includes industrial robots, collaborative robots, support robots, and the like. In addition, the details shown in the above-described embodiment can be appropriately changed without departing from the gist of the invention.

Explanation of Reference Numerals

[0037] 1 Robot system 2 Robot arm (robot) 22 Arm 23 End effector 233 Force sensor (acquisition unit) 242 Encoder (acquisition unit) 3 Workpiece 4 Polishing tool (processing tool) 5 Control device 52 Operation unit 53 Display unit 53a Slider 53b Adjustment handle 56 Storage unit 58 Control unit (separation unit, display control unit, determination unit) 60 Reaction force data (reaction force information) 61 High-frequency component 62 Low-frequency component 561 Polishing control program 562 Reaction force data storage area

Claims

1. A robot that holds a machining tool or a workpiece, an acquisition unit that acquires reaction force information regarding a reaction force acting on the robot due to contact between the machining tool and the workpiece, a separation unit that separates the reaction force information when the machining tool and the workpiece are relatively moved while being in contact with each other into a high-frequency component and a low-frequency component with respect to a predetermined reference frequency, a display control unit that causes at least the high-frequency component to be displayed on a display unit, A robot system comprising:

2. A control unit that adjusts the position of the machining tool or the workpiece held by the robot based on the low-frequency component, The robot system according to claim 1.

3. The control unit controls the robot to feed the machining tool or the workpiece along a predetermined movement locus while bringing the machining tool and the workpiece into contact with each other, adjusts the position in the pressing direction of the machining tool or the workpiece in the next feed operation so that the distribution of the low-frequency component over the movement locus approaches a constant value based on the low-frequency component in the previous feed operation, The robot system according to claim 2.

4. The display control unit displays the low-frequency component together with the high-frequency component, The robot system according to claim 1.

5. A determination unit that determines the finished state of machining of the workpiece based on whether or not the high-frequency component falls within a predetermined range, The robot system according to claim 1.

6. A robot that holds a machining tool or a workpiece, an acquisition unit that acquires reaction force information regarding a reaction force (acting on the robot) due to contact between the machining tool and the workpiece, a separation unit that separates the reaction force information when the machining tool and the workpiece are relatively moved while being in contact with each other into a high-frequency component and a low-frequency component with respect to a predetermined reference frequency, a control unit that adjusts the position of the machining tool or the workpiece held by the robot based on the low-frequency component, A robot system comprising:

7. A robot that holds a machining tool or a workpiece, an acquisition unit that acquires reaction force information regarding a reaction force acting on the robot due to contact between the machining tool and the workpiece, A control method for a robot system comprising: the control unit of the robot system a separation step of separating the reaction force information when the machining tool and the workpiece are relatively moved while being in contact with each other into a low-frequency component and a high-frequency component with respect to a predetermined reference frequency, A display control step of causing at least the high-frequency component to be displayed on a display unit; A control method for a robot system to execute.

8. A robot that holds a processing tool or a workpiece; A control program for a robot system including an acquisition unit that acquires reaction force information regarding a reaction force acting on the robot due to contact between the processing tool and the workpiece, A computer, A separation unit that separates the reaction force information when the processing tool and the workpiece are relatively moved while being in contact with each other into a high-frequency component and a low-frequency component with respect to a predetermined reference frequency; A display control unit that causes at least the high-frequency component to be displayed on a display unit; A control program for a robot system that functions as.

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