Control device

Abstract

A control device that controls a robot that carries an end effector and executes a predetermined work includes: a force control unit that executes force control on the basis of a detection value from a force detector capable of detecting a force and a torque acting on the robot; and a speed changing unit that, when an operation based on force control is executed, changes the speed related to the progress of the force control and the operation speed of the end effector while cooperating with each other on the basis of the detection value of the force detector.

Description

Technical Field

[0001] This disclosure relates to control devices. Background Technology

[0002] Robot systems are known to have an end effector mounted on the front end of a multi-joint robot, which is then moved by force control to perform a specified task. For example, Patent Documents 1 and 2 describe robot systems capable of performing force-controlled thread tightening operations using a thread tightening machine mounted on the robot.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-331428

[0006] Patent Document 2: Japanese Patent Application Publication No. 2018-24075 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] When a robot equipped with an end effector performs force-controlled tasks, the force control parameters are typically fixed and pre-tuned by the user. However, in force-controlled tasks, there are sometimes parts that can be executed at a higher speed than the speed related to the progress of force control when using the pre-tuned fixed parameters. A technology is desired that can reliably execute force-controlled actions and reduce task cycle time.

[0009] Methods for solving problems

[0010] One aspect of this disclosure is a control device for controlling a robot equipped with an end effector and performing a prescribed task. The control device includes: a force control unit that performs force control based on detection values ​​from a force detector, wherein the force detector is capable of detecting forces and torques acting on the robot; and a speed change unit that, when performing an action based on the force control, simultaneously changes the speed related to the progress of the force control and the operating speed of the end effector based on the detection values ​​from the force detector.

[0011] These objects, features, and advantages of the invention will become more apparent from the detailed description of typical embodiments of the invention shown in the accompanying drawings. Attached Figure Description

[0012] Figure 1 This is a diagram illustrating the device structure of a robot system according to one embodiment.

[0013] Figure 2 This is a functional block diagram of the robot system.

[0014] Figure 3 It is a diagram used to illustrate the various stages of thread tightening.

[0015] Figure 4 It is a diagram showing the detected force value, the progress speed of force control, and the rotation speed of the thread tightening machine during thread tightening.

[0016] Figure 5 This is a graph showing the time progression of torque detection values ​​during position / attitude correction when the speed adjustment of this embodiment is not performed, as a comparative example.

[0017] Figure 6 This is a graph showing the time progression of torque detection values ​​during the speed adjustment of position / posture error in this embodiment.

[0018] Figure 7 It is a graph showing the detected value of the thread tightening force and the correction speed of the position / posture error.

[0019] Figure 8 This is an example of a settings screen used to set the termination conditions.

[0020] Figure 9 This is a diagram used to illustrate a force-controlled grinding action.

[0021] Figure 10 This diagram is used to illustrate force-controlled deburring operations.

[0022] Figure 11 This diagram illustrates the speed adjustment in this embodiment when the tool comes into contact with objects such as burrs during actions such as deburring.

[0023] Figure 12 This is a flowchart illustrating the speed adjustment process in the force control of this embodiment. Detailed Implementation

[0024] Next, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the referenced drawings, the same structural or functional parts are labeled with the same reference numerals. For ease of understanding, the scale of these drawings has been appropriately changed. Furthermore, the embodiments shown in the drawings are examples for carrying out the invention, and the invention is not limited to the illustrated embodiments.

[0025] Figure 1 This is a diagram illustrating the device structure of a robot system 100 according to one embodiment. (See diagram for example.) Figure 1As shown, the robot system 100 includes: a robot 10, a robot control device 20 for controlling the robot 10, and a teaching pendant 30 connected to the robot control device 20. A thread tightening machine 60, serving as an end effector, is mounted on the flange 11 of the wrist of the robot 10 via a mounting plate 51. A force sensor (force detector) 70 for detecting external forces is installed between the flange 11 of the wrist and the mounting plate 51. In this configuration, the robot system 100 can set the thread tightening machine 60 to a desired position / posture via the robot 10, and, based on the detection value detected by the force sensor 70, cause the robot 10 to perform a force-controlled thread tightening operation. As described in detail below, the robot control device 20 simultaneously changes the speed related to the progress of force control and the operating speed of the end effector based on the detection value of the force detector, thereby shortening the cycle time of the force-controlled operation.

[0026] As an example, robot 10 is a six-axis vertical articulated robot. Furthermore, robot 10 can also be used, depending on the task at hand, as various types of robots such as horizontal articulated robots, parallel linkage robots, and dual-arm robots. Figure 1 The example shown is a structure in which a thread tightening machine 60 is mounted on a robot 10 as an end effector. Various types of end effectors can be installed on the robot 10 depending on the purpose of the operation.

[0027] The robot control device 20 controls the actions of the robot 10 according to an action program or instructions from the teach pendant 30. The robot control device 20 may have a hardware structure that functions as a general-purpose computer, which includes a processor 21 (see reference 20). Figure 2 ), memory (ROM, RAM, non-volatile memory, etc.), storage devices, operating units, input / output interfaces, network interfaces, etc.

[0028] The teach pendant 30 is used as an operating terminal for teaching or setting various parameters of the robot 10. The teach pendant 30 can be a teaching device composed of a tablet terminal or the like. The teach pendant 30 can have a hardware structure similar to a general-purpose computer, which includes a processor, memory (ROM, RAM, non-volatile memory, etc.), storage device, operating unit, and display unit 31 (see reference). Figure 2 Input / output interfaces, network interfaces, etc.

[0029] As an example, the thread tightening machine 60 is an angle-type thread tightening machine (nut tightening machine). The thread tightening machine 60 has a main body 61 and a head 62 connected to the front end of the main body 61. The main body 61 internally includes a control unit 161 and a motor 162 (see reference). Figure 2The head 62 holds the sleeve 65, which serves as a tool. The screw 81 is held in the sleeve 65. The thread tightening machine 60 is connected to the robot control device 20 and, according to instructions from the robot control device 20, tightens the screw 81 into the threaded hole of the object.

[0030] The thread tightening machine 60 is mounted on one side of the mounting plate 51, and the other side of the mounting plate 51 is mounted on the flange 11 of the robot 10. In this structure, the thread tightening machine 60 can be set to a desired position / posture by the robot 10 to perform thread tightening operations on the object.

[0031] Force sensor 70 is, for example, a six-axis force sensor that detects forces acting in mutually orthogonal X, Y, and Z axes, as well as torques about each axis. Furthermore, in this embodiment, the force sensor 70 is configured to detect external forces acting on the robot 10, but it could also be configured to detect external forces using the detection values ​​of torque sensors installed on each axis of the robot instead of a force sensor.

[0032] Figure 2 This is a functional block diagram of robot system 100. (Example) Figure 2 As shown, the robot control device 20 includes: a motion control unit 121, a force control unit 122, a parameter adjustment unit 123, a force data processing unit 124, a speed change unit 125, a setting unit 126, and a termination condition determination unit 127. These functional blocks can be functional elements implemented by the processor 21 of the robot control device 20 executing software.

[0033] The robot control device 20 has a storage unit 22. The storage unit 22 is a storage device, such as a non-volatile memory or a hard disk device. The storage unit 22 stores the motion program for controlling the robot 10, various setting information including force control parameters or motion parameters, etc.

[0034] The motion control unit 121 controls the movement of the robot 10 according to the motion program or according to the instructions from the teach pendant 30. The robot control device 20 includes a servo control unit (not shown) that executes servo control of the motors 111 for each axis according to the instructions generated by the motion control unit 121 for each axis.

[0035] The force data processing unit 124 provides the following functions: calculating the external force (force and torque) acting on a specified part (such as the thread tightening machine 60) of the robot 10 based on the detection value of the force sensor 70. The position and orientation of the force sensor 70 can be calculated based on the position and orientation of the coordinate system of the front end of the robot 10's wrist, and the relative position information of the force sensor 70 relative to the front end of the wrist. The force data processing unit 124 can calculate the magnitude and direction of the force or torque in any pre-set coordinate system of the robot 10 based on the position, orientation, and detection value of the force sensor 70.

[0036] The force control unit 122 performs the following functions: it executes force control based on the force information calculated by the force data processing unit 124 and the specified force control parameters. The motion control unit 121 performs the following functions: it causes the robot 10 to perform force-controlled actions based on the instructions of the force control unit 122.

[0037] The parameter adjustment unit 123 provides, for example, the following function: by having the robot 10 repeatedly perform force-controlled actions (position / posture correction actions in thread tightening operations, precision fitting operations, etc.), the force control parameters (pressing force, force control gain (pressing direction, position / posture error direction), etc.) are adjusted. The user can apply the force control parameters obtained in advance using the function of the parameter adjustment unit 123 as the force control parameters of the motion program.

[0038] The speed change unit 125 provides the following function: when performing a force-controlled action, it changes the speed related to the progress of force control and the speed of the end effector simultaneously based on the detection value of the force detector.

[0039] The setting unit 126 provides functions for setting functions related to the motion program. The functions of the setting unit 126 include the following: in programming that uses icons corresponding to various functions of the robot, a user interface is provided for detailed settings of each icon.

[0040] The termination condition determination unit 127 has the following function: to determine whether the force-controlled operation has ended based on the prescribed termination determination conditions.

[0041] The thread tightening machine 60 includes: a motor 162 for rotating a sleeve 65, and a control unit 161 for driving and controlling the motor 162. The control unit 161 drives and controls the motor 162 according to instructions (including the specification of motion parameters, etc.) from the motion control unit 121. The control unit 161 may be composed, for example, a microcomputer chip incorporating a CPU, memory (ROM, RAM, non-volatile memory, etc.).

[0042] The following describes a thread tightening operation performed under the control of the robot control device 20, which uses force control.

[0043] To understand the thread tightening operation of this embodiment, a general force-controlled thread tightening operation will be described here. In a force-controlled thread tightening operation, the robot 10 (sleeve 65) is first positioned at the taught thread tightening start position, and while correcting for position / posture errors, the screw 81 is inserted into the threaded hole and tightened. In a force-controlled thread tightening operation like the one described above, generally fixed values ​​are used for parameters such as pressure, the rotational speed of the thread tightening machine, force control gain, and force control progress speed. However, in force-controlled operations, there are sometimes parts where the force control progress speed can be executed at a higher speed than the fixed speed. On the other hand, in order to shorten the cycle time, dividing the operation into programs and generating an action program by setting parameters such as progress speed for each segment requires a lot of effort. In view of this situation, the robot control device 20 of this embodiment provides the following function: when performing a force-based operation, it automatically changes the speed related to the progress of force control in coordination with the motion speed of the end effector based on the detection value of the force detector.

[0044] The following describes two examples of actions performed by the robot control device 20 in a force-controlled thread tightening operation, where the speed related to the progress of force control is simultaneously changed in coordination with the movement speed of the end effector. Furthermore, in the two examples described below, the robot control device 20, from the viewpoint of the shift in the magnitude of the force detector's reading, divides the force-controlled thread tightening operation into... Figure 3 The speed is controlled in three stages as shown.

[0045] like Figure 3 As shown on the left, the first stage involves using force control to correct the positional and posture errors (position / posture errors) of the robot 10 (sleeve 65) positioned at the thread tightening start position. Here, as... Figure 3 In the first stage, represented as distance d, the positional error can be defined as the offset of the center of the front end of screw 81 relative to the centerline C1 of threaded hole 91. For example... Figure 3 In the first stage, as represented by angle θ, the posture error can be defined as the inclination of the central axis C2 of screw 81 (sleeve 65) relative to the center line C1 of threaded hole 91. In the first stage, the position error d and posture error θ are corrected by force control.

[0046] like Figure 3As shown in the center, the second stage is when the position error d1 / posture error θ1 is close to convergence, and force control is used to move the screw 81 along the thread tightening axis to begin thread tightening. (As shown in the center) Figure 3 As shown on the right, the third stage is the stage of using force control to move the screw 81 axially and fasten the screw 81 to the threaded hole 91.

[0047] (Example of the first action)

[0048] In the first action example, the robot control device 20, based on the detection value of the force detector, simultaneously changes the force control progress speed and the rotational speed of the thread tightening machine 60 in the first to third stages, respectively. Here, the force control progress speed is, for example, the target speed that moves the robot 10 (sleeve 65) towards the target force (here, the pressing direction of the screw 81 (thread tightening axis direction)). Figure 3 As shown, the first stage corresponds to the initial state where the robot 10 (sleeve 65) is positioned at the starting position. Therefore, the position / posture error is relatively large here, and the detection value (force / torque) of the force detector becomes larger. When the speed change unit 125 detects that the force detector detection value is large (for example, when the detection value exceeds a predetermined threshold), it sets the force-controlled progress speed to a low speed mode (first speed mode) and sets the rotation speed of the thread tightening machine 60 to a low speed mode (first action speed mode). The threshold used to detect whether the force detector detection value is large can be, for example, an experimental value or a theoretical value.

[0049] Here, regarding the progress rate of force control, low-speed mode refers to the situation where the speed is below the reference progress rate. The reference progress rate (hereinafter also referred to as the reference progress rate) is, for example,

[0050] • A fixed progress speed set by the user via the settings screen, or

[0051] The standard values ​​are derived from various parameters such as the length of the screw body, the thread pitch, the thread tightening time, and the screw rotation speed.

[0052] Regarding the operating speed of the thread tightening machine 60, low-speed mode refers to a rotational speed that is lower than the reference rotational speed. The reference rotational speed (hereinafter also referred to as the reference rotational speed) is, for example,...

[0053] • The rotation speed is preset by the user via the settings screen, or

[0054] • Standard values ​​derived from parameters such as the length of the screw body, the thread pitch, and the thread tightening time.

[0055] In this way, the robot control device 20 appropriately corrects the position / posture by setting the progress speed of force control during the correction of the position / posture error of the robot 10 to a low-speed mode, so that the screw 81 can be reliably inserted into the threaded hole 91. In addition, at this time, the robot control device 20 also cooperatively sets the rotation speed of the thread tightening machine 60 to a low-speed mode, thereby protecting the screw 81 and reliably correcting the position / posture.

[0056] In the second stage, the position / posture error is corrected in the first stage, bringing the position / posture error to near convergence, thus reducing the detection value of the force detector. Specifically, the detection values ​​of the force in the translational direction (force in the XY direction in the figure) and the torque (WPR) related to the position / posture correction decrease. Therefore, when the detection value (translational force, torque) of the force detector becomes small (for example, when the detected value is below a specified threshold), the speed change unit 125 sets the force control progress speed to a high-speed mode (second speed mode) and sets the rotational speed of the thread tightening machine 60 to a high-speed mode (second operating speed mode). Here, regarding the progress speed, the high-speed mode is, for example, a progress speed that is faster than the aforementioned reference progress speed. Regarding the operating speed of the thread tightening machine 60, the high-speed mode is, for example, a rotational speed that is faster than the aforementioned reference rotational speed.

[0057] In the second stage, the position / orientation error is close to convergence, and the screw 81 is in the initial stage of tightening into the threaded hole 91. Therefore, the second stage allows for increased force control progress speed and increased rotational speed of the thread tightening machine 60. Thus, by simultaneously increasing both the force control progress speed and the rotational speed of the thread tightening machine 60 in the second stage, the overall cycle time for thread tightening can be shortened.

[0058] In the third stage, the screw 81 is in a state of being tightened while rotating in the threaded hole 91, so the detection value of the force detector is relatively large. Therefore, when the detection value (force / torque) of the force detector increases (for example, when the detection value exceeds a specified threshold), the speed change unit 125 sets the progress speed of the force control to a low speed mode and sets the rotation speed of the thread tightening machine 60 to a low speed mode.

[0059] Thus, in the third stage, the robot control device 20 sets the force control progress speed to a relatively low speed and the rotation speed of the thread tightening machine 60 to a relatively low speed, so as to properly tighten the screw 81 into the threaded hole. This avoids large posture errors during the tightening of the screw 81 into the threaded hole, enabling stable thread tightening.

[0060] By controlling the speed of the first action example as described above, the progress speed of parts that could have been increased in operations using force control can be improved, thereby shortening the overall cycle time of the operation.

[0061] The first action example can be described as an action example that can switch between a first speed mode and a second speed mode based on the detection value of the force detector. In the first speed mode, the force-controlled progress speed and the rotational speed of the thread tightening machine 60 are both set to a first rotational speed. In the second speed mode, the force-controlled progress speed is set to a second speed, which is lower than the first speed, and the rotational speed of the thread tightening machine 60 is also set to a second rotational speed, which is lower than the first rotational speed. This structure improves the progress speed of parts that could otherwise be increased in force-controlled operations, thereby shortening the overall cycle time of the operation.

[0062] Figure 4 This is a chart showing examples of measured values ​​detected by a force detector during thread tightening operations. Figure 5 The graphs represent curves G1, G2, and G3 of the force detection values ​​in the X, Y, and Z directions based on the force sensor 70. Here, X, Y, and Z are represented by... Figure 3 The measured values ​​are based on a coordinate system where the axial direction (pressing direction) of the thread tightening is defined as the Z direction, and the two directions orthogonal to it are defined as the X and Y directions. Furthermore, the forces in the X and Y directions are defined as translational forces. Additionally, in... Figure 4 To facilitate understanding, the time progression of the detection values ​​is shown to roughly correspond to the first to third stages. Figure 4 In this context, the situation where the absolute value of the force increases in the negative direction is also defined as the situation where the force increases.

[0063] The speed change unit 125 can determine the first stage where the position / posture error is relatively large by at least one of the following judgment criteria (a1) and (a2) based on the detection value of the force detector.

[0064] (Judgment Criterion a1): The detected value of the force in the translation direction increases.

[0065] exist Figure 4 In the example, curve G1 (detection force in the X direction) changes significantly in the negative direction (refer to the part indicated by arrow B). The speed change unit 125 can determine that it is in the first stage when curve G1 (detection force in the X direction) changes significantly in the negative direction.

[0066] (Judgment Criterion a2): Immediately after the thread tightening begins, the detected value of the force in the pressing direction (Z direction) increases.

[0067] Given the positional error at the start of thread tightening, and the positional error of screw 81 relative to threaded hole 91, the detected force in the pressing direction is considered to be relatively large (refer to...). Figure 4 The curve G3 at the start of thread tightening. Therefore, the speed change unit 125 can determine that it is in the first stage when the detected value of the force in the Z direction (curve G3) increases after the thread tightening begins.

[0068] When it is determined that it is in the first stage, the speed change unit 125 sets the force control progress speed to low speed mode as described above, and sets the rotation speed of the thread tightening machine 60 to low speed mode.

[0069] When entering the second stage, as the position / posture error decreases, the detected values ​​of force (translational force) or torque in the X and Y directions decrease. Here, the speed control unit 125 can detect the decrease in translational force and determine that it is in the second stage. When it is determined to be in the second stage, the speed control unit 125 sets the force control progress speed to a high-speed mode, as described above, and sets the rotational speed of the thread tightening machine 60 to a high-speed mode.

[0070] When entering the third stage, screw 81 is in a state of being tightened and moving simultaneously within threaded hole 91, thus easily subjecting to large forces in the X or Y directions. Therefore, as... Figure 4 As shown, the detected force value in the X or Y direction increases. Therefore, the speed change unit 125 can determine that it is in the third stage by detecting the increase in force in the X or Y direction. When it is determined that it is in the third stage, as described above, the speed change unit 125 sets the force control progress speed to a low speed mode and sets the rotation speed of the thread tightening machine 60 to a low speed mode.

[0071] As described above, the speed adjustment unit 125 can make accurate speed adjustments corresponding to the force-controlled thread tightening stage based on the detection value of the force detector, thereby shortening the overall cycle time of the thread tightening operation.

[0072] (Example of the second action)

[0073] Next, a second action example will be described when the robot control device 20 performs a task using force control. This second action example is an action example in which, in addition to the speed adjustment action in the first action example, the speed for correcting position / posture errors is also adjusted. The following will explain how the speed for correcting position / posture errors is adjusted.

[0074] Reference Figure 5 and Figure 6 The second action example will be explained. Figure 5This is a graph illustrating an example of the measured force values ​​when robot 10 corrects for position / posture errors during a thread tightening operation without applying the second action example. Furthermore, in Figure 5 In the diagram, the horizontal axis represents time, and the vertical axis represents torque. Figure 5 The chart shown corresponds to the raw detection values ​​of the force detector applied to robot 10, i.e., the case where position / pose errors are corrected using standard parameters. Figure 5 The diagram illustrates the torques Mx about the X-axis, My about the Y-axis, and Mz about the Z-axis. The X, Y, and Z axes are... Figure 4 The coordinate system shown corresponds to this. For example... Figure 5 As shown, under the condition that the correction rate of position / or posture error is standard, the detected value of the force detector (in this case, torque) shows a gradual change.

[0075] Figure 6 It means in such Figure 5 A graph showing the shift in force detection values ​​applied to position / posture error correction when performing the second action under those observed detection values. Furthermore, in Figure 6 In the diagram, the horizontal axis represents time, and the vertical axis records the measured values ​​corresponding to the torque as torque. Figure 6 The torques T4, T5, and T6 correspond to the torques Mx, My, and Mz, respectively. In this embodiment, when the speed change unit 125 detects that the force detector's value exceeds a predetermined threshold and becomes large, it considers this as a state of increased position or posture error and sets the position / posture correction speed to a high-speed mode (first correction speed mode) to quickly correct the position or posture error.

[0076] Here, the high-speed mode for position / pose error correction will be explained. In force-controlled position and pose error correction, the larger the position and pose error, the larger the detected value (force / torque) of the force detector. Furthermore, in force control, generally speaking, the robot is made to move by multiplying the deviation of these detected values ​​from a reference value by the force control gain to obtain the command value. In addition, the reference value in the deviation calculation is usually zero. Therefore, generally speaking, the larger the force control detected value, the higher the position and pose correction response speed. In this embodiment, the speed change unit 125 monitors the force / torque detected values ​​within a certain time range. When the maximum value of the detected value exceeds a predetermined threshold and becomes large, the maximum value (or a value above the maximum value, a value equivalent to the maximum value, or a value based on the maximum value, etc.) is applied as the detected value for a period of time within that certain time range, thereby performing position / pose correction based on force control at high speed. Such an action mode related to position / pose correction is called the high-speed mode for position / pose error correction.

[0077] Regarding the position / attitude correction speed, the low-speed mode (second correction speed mode) refers to a speed mode where the position / attitude correction is slower than the high-speed mode mentioned above. For example, it is suitable for situations where the raw detection values ​​of the force detector are directly applied to perform force-based position / attitude correction. Figure 5 (The action shown).

[0078] Reference Figure 5 and Figure 6 The specific actions for correcting the position / posture error in the second action example will be explained. The speed change unit 125 performs this action in the following process.

[0079] (Process 1) First, the speed change unit 125 sets a certain time range for the control of this action example.

[0080] (Process 2) The speed change unit 125 detects the maximum value of the force / torque detection value that exceeds the specified threshold within a certain time range (for example, the peak value that exceeds the specified threshold is taken).

[0081] (Process 3) The speed change unit 125 uses the detected maximum value as the detection value in the position / attitude error correction (fixes the detection value in the position / attitude error correction to this maximum value), thereby setting the position / attitude correction speed to high speed mode.

[0082] (Procedure 4) When the detected value is below the threshold, set the position / attitude correction speed to low speed mode (the original detection value of the force detector is directly applied as the detection value in the position / attitude error correction).

[0083] In process 1, the speed change unit 125 sets a time range of 2 to 7 seconds as a certain time range and sets the threshold to 15N. Furthermore, in process 2, the observed value is as follows... Figure 5 As shown, the maximum value of the detected torque My (15.01 Nm) exceeds the threshold (15 Nm). At this time, the speed change unit 125 sets the maximum value (15.01 Nm) as the detected value of the torque My for a certain time range (2 seconds to 7 seconds) (refer to...). Figure 6 Therefore, the force control unit 122, for a time range of 2 to 7 seconds, considers the detected value of torque My to be 15.01 Nm (i.e., considers a large posture error to be continuous), and rapidly corrects the posture error related to torque My (process 3).

[0084] Regarding forces / torques detected within a certain time range that do not exceed a threshold, there is almost no position / attitude deviation. Therefore, the speed change unit 125 sets the position / attitude correction speed to a low-speed mode (process 4). Figure 5In the example of the chart, the detected values ​​for torque Mx and torque Mz are below the threshold (15 Nm). Therefore, the speed change unit 125 corrects the position / attitude in a low-speed mode for the attitude correction around the X-axis corresponding to torque Mx and the attitude correction around the Z-axis corresponding to torque Mz.

[0085] By employing speed control based on position / or posture as described above, it is possible to accurately detect large deviations in position and posture, thereby improving correction speed. This second action also shortens the overall cycle time of the thread tightening operation.

[0086] The speed change unit 125 performs the above-mentioned processes 1 to 4 while sequentially shifting a certain time range to 2 to 7 seconds, 3 to 8 seconds, 4 to 9 seconds, etc., thereby enabling control of the speed of position / posture change for the entire thread tightening operation.

[0087] Figure 7 This diagram shows an example of the measured value detected by the force detector during thread tightening and the state of the speed adjustment unit 125 adjusting the position / attitude error at this time. Furthermore, the measured values ​​here are compared with... Figure 4 The same applies as shown. In the first stage where a relatively large position / attitude error occurs, as the position / attitude error correction work proceeds, the detected value (curve G1) or torque in the translation direction becomes relatively large. In the first stage, the speed change unit 125 detects that the maximum value of the detected translation force or torque exceeds a predetermined threshold, which is considered a state of large position / attitude error, and sets the position / attitude error correction speed to a high-speed mode.

[0088] When entering the second stage of position / attitude error convergence, the detected value of translational force or torque decreases. Since the detected value of translational force or torque is below a threshold, the speed control unit 125 sets the position / attitude error correction speed to a low-speed mode. Then, when entering the third stage, the screw 81 is tightened in the threaded hole 91, and the translational force or torque becomes a large value exceeding the threshold. Correspondingly, the speed control unit 125 sets the position / attitude error correction speed to a high-speed mode.

[0089] In this way, the speed change unit 125 can accurately grasp the position / orientation error state and appropriately set the position / orientation correction speed. This action can automatically shorten the processing time of the parts of the thread tightening assembly that can shorten the processing time, thereby shortening the cycle time of the entire thread tightening assembly.

[0090] Furthermore, in the second action example described above, the following operation is defined as the high-speed mode for position / posture error correction: when the maximum value of the detected force or torque within a certain time range is detected, and this maximum value exceeds a predetermined threshold, the maximum value (or a value exceeding it) is set as the detected value in position / posture error correction. This definition is merely one example; for instance, the high-speed mode for position / posture error correction could also be the following action: when the detected force / torque value within a certain time range exceeds a reference value, the reference value (or a value exceeding it) is set as the detected value in position / posture error correction.

[0091] The low-speed mode in position / attitude error correction simply refers to a speed mode where the correction speed for position / attitude error is low compared to the high-speed mode described above.

[0092] Furthermore, although the speed adjustment of the position / posture error in the second action example is described above as being performed based on the speed adjustment of the force control progression in the first action example, there could also be an action example where the speed adjustment of the position / posture error in the second action example is performed instead of the speed adjustment of the force control progression in the first action example. That is, there could also be an action example (the third action example).

[0093] (Example of the third action)

[0094] • In the first stage, the position / posture error correction is set to high speed mode, and the end effector's motion speed is set to low speed mode.

[0095] • In the second stage, the position / pose error correction is set to low speed mode, and the end effector's motion speed is set to high speed mode.

[0096] • In the third stage, the position / posture error correction is set to high speed mode, and the end effector's motion speed is set to low speed mode.

[0097] Next, the setting function of the setting unit 126 for setting the end conditions of the thread tightening operation, which is used to speed up the thread tightening operation, will be explained. Here, the robot control device 20 is configured to accept icon-based programming, where the icons represent the robot's function commands, and the setting unit 126 is configured to provide a function for detailed setting of each icon. Figure 8 The setting screen 300 displays the function icon 301 corresponding to the thread tightening function provided by the setting unit 126. The setting unit 126 displays the setting screen 300 on the display unit 31 of the teach pendant 30 and accepts input to the setting screen 300 by the user through the operation unit of the teach pendant 30.

[0098] like Figure 8As shown, the setting screen 300 includes target force, force control progress speed, thread tightening depth, force termination threshold, and speed termination threshold as settings related to force-controlled thread tightening. The setting screen 300 also includes setting buttons 311 to 314 for setting the termination conditions of force-controlled thread tightening.

[0099] (1) Setting button 311 is a button used to set the following: the pressing force of the thread tightening reaches the target force as the end condition of thread tightening.

[0100] (2) Setting button 312 is a button used to set the following: the thread tightening depth is set to the range of the specified minimum to maximum value as the thread tightening end condition.

[0101] (3) Setting button 313 is a button used to set the following: when the force (pressing pressure) is the end condition, the pressing pressure exceeds the threshold specified here (90% of the target force) as the end condition. When both setting button 311 and setting button 313 are set to ON, the thread tightening ends when the target force exceeds the judgment threshold set here.

[0102] (4) Setting button 314 is a button used to set the following: the speed of robot 10 (sleeve 65) is less than the judgment threshold set here, as the end condition.

[0103] Furthermore, the termination conditions (1) to (4) presented here are merely illustrative, and the termination conditions are not limited to these. For example, torque can also be used as a termination condition. In this case, it is also possible to... Figure 8 The settings screen also includes settings for setting the torque threshold (torque threshold at the end) as a termination condition, as well as a setting button.

[0104] The termination condition determination unit 127 determines that the thread tightening is complete when all termination conditions set to be enabled are met.

[0105] In the setting screen 300, it is possible to determine whether each setting of the termination condition will function as a termination condition. Therefore, users who want to achieve high-speed thread tightening can avoid unnecessary control by setting the minimum required termination condition to "on". For example, when there are individual differences in screw length, monitoring the thread tightening depth is particularly important. Therefore, in such cases, only the setting button 312 needs to be turned on.

[0106] The above-described embodiment is a structural example of using a nut tightening machine as a thread tightening mechanism (end effector) mounted on the robot 10. However, as a thread tightening mechanism, there are also structural examples using an auxiliary axis motor or a robot wrist axis. In the structure using an auxiliary axis motor, a mounting plate is installed on the flange 11 of the robot 10, the auxiliary axis motor is fixed to the mounting plate, and a thread tightening sleeve is fixed to the drive shaft of the auxiliary axis motor. In this structure, the robot control device 20 (speed change unit 125) changes the speed related to the progress of force control and the rotational speed of the auxiliary axis motor simultaneously based on the detection value of the force detector. In the structure using the robot wrist axis (drive shaft of the wrist), a sleeve is fixed to the wrist axis of the robot 10. In this structure, the robot control device 20 (speed change unit 125) changes the speed related to the progress of force control and the rotational speed of the wrist axis motor simultaneously based on the detection value of the force detector.

[0107] The above embodiment is a structural example related to speed adjustment during force-controlled thread tightening. However, the force-controlled speed adjustment structure described above can be applied to various force-controlled operations (grinding, deburring, precision fitting, contouring, friction stir welding, etc.). For example, consider... Figure 9 and Figure 10 The grinding and deburring operations are shown respectively.

[0108] like Figure 9 As shown, in the grinding operation, a grinding tool (grinding machine or polishing wheel) 66 is rotatably mounted on the flange 11A of the wrist of the robot 10A as an end effector. For example, a force sensor 70 is disposed between the flange 11A and the tool 66. The robot control unit 20 executes the grinding operation according to the grinding motion program, moving the grinding tool 66 along a trajectory T on the surface of the object W1 while rotating it. The robot 10A performs force control to control the pressing direction ( Figure 9 The force detected (in the direction of the middle arrow A) is the target force.

[0109] Figure 9The illustrated structural example is one in which the grinding tool 66 is driven by a wrist axis motor mounted on the wrist of the robot 10A. In this configuration, the robot control unit 20 (speed change unit 125) simultaneously changes the speed related to the progress of force control and the rotational speed of the wrist axis motor based on the detection value of the force detector. Alternatively, instead of this structural example, a structure can be used where the grinding tool 66 is driven by an additional axis motor mounted on the robot 10A. In this configuration, the robot control unit 20 (speed change unit 125) simultaneously changes the speed related to the progress of force control and the rotational speed of the additional axis motor based on the detection value of the force detector. Furthermore, in the case of grinding operations, the speed related to the progress of force control can be defined as the robot's movement speed along the target track (track T). Additionally, various termination conditions can be set for the grinding operation. For example, termination conditions can include completing the movement along the length of the target track (track T), completing the movement within the target range (work object range), or detecting a force exceeding / below a specified value.

[0110] like Figure 10 As shown, in the deburring operation, the grinder 67 is mounted on the flange 11A of the wrist of the robot 10A in a state that allows it to rotate via the wrist axis. A force sensor 70 is disposed between the flange 11A and the grinder 67. Following the deburring program, the robot 10A moves the grinder 67 along trajectory T2 on the workpiece W2 to remove burrs located on the edges of the workpiece W2. During the processing of the edges on the upper left side of the workpiece W2 in the figure, force control is executed to press the grinder 67 in the pressing direction indicated by arrow A1 in the figure. Additionally, during the processing of the edges near the front side of the workpiece W2 in the figure, force control is executed to press the grinder 67 in the pressing direction indicated by arrow A2 in the figure.

[0111] Figure 10The illustrated structural example is one where the polisher 67 is driven by a wrist axis motor mounted on the wrist of the robot 10A. In this configuration, the robot control unit 20 (speed change unit 125) simultaneously changes the speed related to the progress of force control and the rotational speed of the wrist axis motor based on the detection value of the force detector. Alternatively, a structure can be used where the polisher 67 is driven by an additional axis motor mounted on the robot 10A. In this configuration, the robot control unit 20 (speed change unit 125) simultaneously changes the speed related to the progress of force control and the rotational speed of the additional axis motor based on the detection value of the force detector. Furthermore, in the case of deburring operations, the speed related to the progress of force control can be defined as the robot's movement speed along the target track (track T2). Additionally, various termination conditions can be set for deburring operations. For example, termination conditions can include completing the length movement along the target track (track T2), completing the movement within the target range (work object range), or detecting a force exceeding / below a specified value.

[0112] Figure 11 It is used for in Figure 9 The grinding operation shown Figure 10 The diagram illustrates the application of the speed adjustment shown in the above-described embodiment during the deburring operation. Furthermore, in... Figure 11 The diagram illustrates a deburring operation using a grinder 67 as the end effector, and the same action is taken when using a tool 66 as the end effector for a grinding operation. Figure 11 This describes the force-controlled behavior of the grinding machine 67 when it comes into contact with a large protrusion M, such as a burr, during deburring operations on workpiece W and detects a large force. Thus, when the grinding machine 67 comes into contact with the protrusion M on a pre-taught path, the robot 10 can avoid the protrusion M. Here, it is shown that the grinding machine 67 comes into contact with the protrusion M while traveling on the pre-taught path R1, and returns to the pre-taught path R4 via avoidance paths R2, R3, and R4. Furthermore, Figure 11 Conceptually representing the behavior of the polisher 67 in avoiding the protrusion M, for example, in a force-controlled polisher 67, the pressing direction is... Figure 11 When considering the depth direction of the paper, the path to be avoided, R2 to R3, can actually be towards... Figure 11 The path to avoid in the forward direction of the paper.

[0113] When the robot performs such an action, the speed control unit 125 of this embodiment can detect a large force (force / torque exceeding a threshold) due to contact with the protrusion M, and set the force control progress speed on paths R2, R3, and R4 when the robot performs the avoidance action to a low-speed mode, and also set the rotation speed of the grinder 67 to a low-speed mode. Then, when the grinder 67 returns to the taught path R5, the speed control unit 125 can set the force control progress speed to a high-speed mode, and also set the rotation speed of the grinder 67 to a high-speed mode.

[0114] With this structure, when in contact with the protrusion M, the force-controlled progress speed is kept low, and the rotation speed of the grinder is also reduced. This prevents the robot from taking unnecessary actions when the grinder 67 comes into contact with larger protrusions such as M, thus stabilizing the motion. Consequently, the cycle time of the entire operation can be reduced.

[0115] Figure 11 The actions described in the text are in Figure 9 The same method can be applied in the grinding operation shown.

[0116] Figure 12 This diagram illustrates the speed adjustment process of force control in the above-described embodiment of the robot control device 20 as a flowchart. Furthermore, the speed adjustment process when applying the first and second action examples described above will be explained here.

[0117] First, the user teaches the parameters related to force control (step S1). Here, for example, the target force, feed rate, thread tightening depth, force control gain, and various other parameters are set. Next, the user... Figure 8 Set the end condition for the force control action in the setting screen (step S2).

[0118] Then, the robot control unit 20 (speed change unit 125) begins force control operations on the robot 10, monitoring various parameters including force / torque and termination condition parameters (step S3). Next, the robot control unit 20 (speed change unit 125) determines whether the detected force value (force / torque) exceeds a threshold and increases (step S4). When it is determined that the detected value (force / torque) exceeds the threshold (S4: Yes), the robot control unit 20 (speed change unit 125) sets the force control progress speed to a low speed mode, sets the rotation speed of the thread tightening machine (nut tightening machine) 60 to a low speed mode, and sets the position / attitude correction speed to a high speed mode (step S5).

[0119] On the other hand, in step S4, when it is determined that the detected value (force / torque) is below the threshold (S4: No), the robot control device 20 (speed change unit 125) sets the progress speed of force control to high speed mode, sets the rotation speed of the thread tightening machine (nut tightening machine) 60 to high speed mode, and sets the position / attitude correction speed to low speed mode (step S6).

[0120] Then, the robot control device 20 initiates the force-based operation (step S7). Next, the robot control device 20 (end condition determination unit 127) determines whether the end condition set by the user is met (step S8). If the end condition is not met (S8: No), the process from step S3 onwards is repeated. If the end condition is met (S8: Yes), the operation ends.

[0121] According to the embodiments described above, the speed related to the progress of force-controlled operations can be adjusted based on the detected force / torque value, enabling the speed of the portion of the force-controlled action that can be executed at high speed to be increased. Furthermore, since the speed related to the progress of force control and the operating speed of the end effector can be adjusted cooperatively, force-controlled operations can be executed stably and accurately.

[0122] Furthermore, in the above embodiment, the structure for switching the speed related to the progress of force control and the operating speed of the end effector between two stages—high-speed mode and low-speed mode—was described. However, it is also possible to switch the speed related to the progress of force control and the operating speed of the end effector in multiple stages, depending on the detection value of the force detector (three or more stages). For example, regarding the "first action example" described above, two thresholds (a first threshold and a second threshold lower than the first threshold) can be applied to the force / torque detection value.

[0123] • When the detected force / torque value exceeds the first threshold, it is set to the first speed mode (the highest speed mode).

[0124] • When the detected force / torque value is below the first threshold but exceeds the second threshold, it is set to the second speed mode (second high-speed speed mode).

[0125] • When the detected force / torque value is below the second threshold, set it to the third speed mode (the lowest speed mode).

[0126] The aforementioned "second action example" can also be understood as performing the same three-stage speed adjustment. Furthermore, in the "second action example," the correction speed for position / posture error can be adjusted by adjusting the magnitude of the detection value (input to the force control unit 122) used in position / posture error correction.

[0127] In the embodiments described above, refer to Figure 2 The functional block diagram illustrating the functional allocation is an example; various variations can be constructed regarding the functional allocation of functional blocks. For instance, it could also be used to... Figure 2 An example of a structure in which at least a portion of the functional blocks configured in the robot control device 20 (e.g., setting unit 126) are configured in the teach pendant 30.

[0128] Since the teach pendant 30 functions as the operating terminal of the robot control device 20, the functions including the functions of the teach pendant 30 can also be defined as the functions of the robot control device 20.

[0129] The structure described in the above embodiments can be applied to control devices for various types of machinery capable of carrying tools to perform force-based operations.

[0130] Figure 2 The functional blocks shown can be implemented by one or more processors of the robot control device executing various software stored in the storage device, or they can be implemented by a structure based on hardware such as ASIC (Application Specific Integrated Circuit).

[0131] The various processing procedures related to the progress speed of force control, the correction speed of position / posture error, and the adjustment of the action speed of the end effector in the above embodiments can be recorded on various storage media that can be read by a computer (e.g., semiconductor memory such as ROM, EEPROM, flash memory, magnetic storage media, CD-ROM, DVD-ROM, etc.).

[0132] As described above, according to each embodiment, force-controlled actions can be reliably executed and the overall cycle time of force-controlled operations can be shortened.

[0133] This disclosure has been described in detail, but it is not limited to the various embodiments described above. Various additions, substitutions, modifications, and partial deletions can be made to these embodiments without departing from the core essence of this disclosure, or without departing from the core essence of this disclosure derived from the claims and their equivalents. Furthermore, these embodiments can also be implemented in combination. For example, in the above embodiments, the order of actions or the order of processes are shown as an example, but are not limited thereto. The same applies to the use of numerical values ​​or mathematical formulas in the description of the above embodiments.

[0134] The following notes further describe the above-described embodiments and variations.

[0135] (Note 1)

[0136] A control device (20) controls a robot (10) equipped with an end effector and performing a prescribed task, wherein,

[0137] The control device (20) has:

[0138] A force control unit (122) performs force control based on detection values ​​from a force detector (70), wherein the force detector is capable of detecting forces and torques acting on the robot (10); and

[0139] The speed change unit (125) changes the speed related to the progress of the force control and the operating speed of the end effector simultaneously, based on the detection value of the force detector (70), when performing the force control-based action.

[0140] (Note 2)

[0141] According to the control device (20) described in Appendix 1, wherein,

[0142] The speed related to the progress of the force control includes: the progress speed in the direction of the target force of the force control, or the progress speed along the target trajectory direction.

[0143] (Note 3)

[0144] According to the control device (20) described in Appendix 2, wherein,

[0145] The speed change unit (125) performs the following operations:

[0146] When the detected value exceeds a predetermined threshold, the progress speed of the force control is set to a first speed mode, and the action speed of the end effector is set to a first action speed mode.

[0147] When the detected value is below the specified threshold, the progress speed of the force control is set to a second speed mode that is faster than the first speed mode, and the action speed of the end effector is set to a second action speed mode that is faster than the first action speed mode.

[0148] (Note 4)

[0149] The control device (20) according to any one of Appendices 1 to 3, wherein,

[0150] The speed of progress of the force control includes the speed of correction of position or posture errors in the force control.

[0151] (Note 5)

[0152] According to the control device (20) described in Appendix 4, wherein,

[0153] The speed change unit (125) performs the following operations:

[0154] When the detected value exceeds a specified threshold, the correction speed of the position error or posture error is set to the first correction speed mode;

[0155] When the detected value is below a specified threshold, the correction speed for the position error or posture error is set to a second correction speed mode, which is slower than the first correction speed mode.

[0156] (Note 6)

[0157] According to the control device (20) described in Appendix 5, wherein,

[0158] The speed change unit (125) sets the first corrected speed mode by applying the maximum value of the detected value detected within a certain time range or a value based on the maximum value to the following calculation, wherein the calculation is: in order to correct the position or posture error, the deviation between the detected force or torque value and the reference value is multiplied by the force control gain to calculate the command value for the robot.

[0159] (Note 7)

[0160] The control device (20) according to any one of Appendices 1 to 6, wherein,

[0161] The control device (20) further includes an end condition determination unit (127) that terminates the force-controlled action based on one or more end conditions specified from a plurality of predetermined end conditions, wherein the end condition is used to terminate the force-controlled action.

[0162] (Postscript 8)

[0163] According to the control device (20) described in Appendix 7, wherein,

[0164] The multiple termination conditions include:

[0165] (1) Apply pressure to achieve the target force;

[0166] (2) The thread tightening depth reaches the specified range;

[0167] (3) The pressure exceeds the threshold set for the target force; and

[0168] (4) The robot's movement speed decreases to below the specified judgment threshold.

[0169] Two or more of them.

[0170] (Note 9)

[0171] The control device (20) according to any one of Appendices 1 to 8, wherein,

[0172] The specified operation is a thread tightening operation, the end effector is a thread tightening mechanism, and the operating speed of the end effector is the rotational speed of the thread tightening mechanism.

[0173] (Postscript 10)

[0174] According to the control device (20) described in Appendix 9, wherein,

[0175] The thread tightening mechanism uses any one of a nut tightening machine, an auxiliary shaft motor, or the robot's wrist axis.

[0176] (Postscript 11)

[0177] The control device (20) according to any one of Appendices 1 to 7, wherein,

[0178] The specified operation is a grinding operation, the end effector is a grinding tool (66), and the operating speed of the end effector is the rotational speed of the grinding tool (66).

[0179] (Postscript 12)

[0180] According to the control device (20) described in Appendix 11, wherein,

[0181] The grinding tool (66) uses an additional axis motor or the wrist axis of the robot (10).

[0182] (Postscript 13)

[0183] The control device (20) according to any one of Appendices 1 to 7, wherein,

[0184] The specified operation is a deburring operation, the end effector is a grinder (67), and the operating speed of the end effector is the rotational speed of the grinder (67).

[0185] (Postscript 14)

[0186] According to the control device (20) described in Appendix 13, wherein,

[0187] The grinder (67) uses an additional axis motor or the wrist axis of the robot (10).

[0188] Symbol Explanation

[0189] 10 robots

[0190] 11 Flange

[0191] 20 Robot control device

[0192] 30 Teaching operation panel

[0193] 51 Mounting Plate

[0194] 60 thread tightening machine

[0195] 65 sleeve

[0196] 61 Main body

[0197] 62 heads

[0198] 70 Force Sensor

[0199] 100 Robot Systems

[0200] 111 motor

[0201] 121 Motion Control Department

[0202] 122 Force Control Department

[0203] 123 Parameter Adjustment Section

[0204] 124 Force Data Processing Department

[0205] 125 Speed ​​Change Section

[0206] 126 Setting Department

[0207] 127 Termination Condition Determination Section

[0208] 161 Control Department

[0209] 162 Motor.

Claims

1. A control device that controls a robot that mounts an end effector and performs a prescribed work, characterized by comprising: a force control section that performs force control based on a detection value from a force detector that detects a force and a moment acting on the robot; and a speed change section that changes, in cooperation with each other, a speed related to progress of the force control and a movement speed of the end effector based on the detection value from the force detector when performing a movement based on the force control.

2. The control device according to claim 1, characterized in that the speed related to progress of the force control includes a progress speed in a target force direction of the force control or a progress speed in a target trajectory direction.

3. The control device according to claim 2, characterized in that the speed change section performs the following actions: when the detection value exceeds a prescribed threshold value, the progress speed of the force control is set to a first speed pattern and the movement speed of the end effector is set to a first movement speed pattern; and when the detection value is below the prescribed threshold value, the progress speed of the force control is set to a second speed pattern that is faster than the first speed pattern and the movement speed of the end effector is set to a second movement speed pattern that is faster than the first movement speed pattern.

4. The control device according to any one of claims 1 to 3, characterized in that the speed related to progress of the force control includes a correction speed of a position error or a posture error in the force control.

5. The control device according to claim 4, characterized in that the speed change section performs the following actions: when the detection value exceeds a prescribed threshold value, the correction speed of the position error or the posture error is set to a first correction speed pattern; and when the detection value is below the prescribed threshold value, the correction speed of the position error or the posture error is set to a second correction speed pattern that is slower than the first correction speed pattern.

6. The control device according to claim 5, characterized in that the speed change section sets the first correction speed pattern by applying a maximum value of the detection value detected within a certain time range or a value based on the maximum value to a calculation for calculating an instruction value for the robot by multiplying a deviation between a detection value of a force or a moment and a reference value by a force control gain in order to correct a position or a posture error.

7. The control device according to any one of claims 1 to 6, characterized by further comprising an end condition determination section that ends the movement based on the force control based on one or more end conditions selected from among prescribed end conditions, wherein the end conditions are used to end the movement based on the force control.

8. The control device according to claim 7, characterized in that the prescribed end conditions include: (1) a pressing force reaches a target force; (2) a screw tightening depth reaches a prescribed range; (3) the pressing force exceeds a determination threshold value set for the target force; and (4) a posture error reaches a prescribed range. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (4) the speed of the robot's movement is reduced to be less than a specified determination threshold, two or more of the above.

9. The control device according to any one of claims 1 to 8, wherein the prescribed work is a screw tightening work, the end effector is a screw tightening mechanism, and the speed of the movement of the end effector is a rotational speed of the screw tightening mechanism.

10. The control device according to claim 9, wherein the screw tightening mechanism uses any one of a nut tightening machine, an additional shaft motor, or a wrist shaft of the robot.

11. The control device according to any one of claims 1 to 7, wherein the prescribed work is a polishing work, the end effector is a polishing tool, and the speed of the movement of the end effector is a rotational speed of the polishing tool.

12. The control device according to claim 11, wherein the polishing tool uses an additional shaft motor or a wrist shaft of the robot.

13. The control device according to any one of claims 1 to 7, wherein the prescribed work is a deburring work, the end effector is a sander, and the speed of the movement of the end effector is a rotational speed of the sander.

14. The control device according to claim 13, wherein the sander uses an additional shaft motor or a wrist shaft of the robot.

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