Control device and robot system

Abstract

A control device for controlling a robot is provided, wherein the control device comprises: a force control unit which, based on a detection value from a force detector that detects the force and torque acting on the robot, and a predetermined plurality of force control parameters, causes the robot to perform a predetermined work by means of force control; and a determination unit which records time series data on the predetermined plurality of force control parameters during an execution of the force control and determines, based on the time series data, whether the predetermined work is successful.

Description

Area

[0001] The present disclosure relates to a control device and a robot system. State of the art

[0002] A robotic system is known that is configured to perform screw tightening by force control using a robot that incorporates a force sensor. Generally, in such a robotic system, a user teaches a robot a starting position for a screw tightening operation. The robot is equipped with a screw tightening mechanism, such as a nut driver, and the screw tightening is then performed by force control at a work target. PTL 1 and 2 each describe a configuration of such a robotic system. List of quotations Patent literature [PTL 1] Unexamined Japanese patent publication (Kokai) No. 2019-188503 A [PTL 2] Unexamined Japanese patent publication (Kokai) No. 2002-331428 A Overview: Technical Task

[0003] The desired technology is one that makes it possible to accurately determine, based on force control parameters, whether the result of work performed by a robot based on force control is successful. Technical solution

[0004] An embodiment of the present disclosure is a control device configured to control a robot, wherein the control device includes a force control unit configured to cause the robot to perform a predetermined work based on force control, based on a detection value of a force detector configured to detect a force and a moment acting on the robot, and a plurality of predetermined force control parameters, and a determination unit configured to record individual time series data of the plurality of predetermined force control parameters during an execution of the force control and to determine, based on the individual time series data, whether the predetermined work is successful.

[0005] The tasks, features and advantages of the present invention and other tasks, features and advantages will become more apparent from the detailed description of typical embodiments of the present invention, which are illustrated in the accompanying drawings. Brief description of the drawings Fig. Figure 1 is a graphical representation depicting a configuration of a robot system according to one embodiment. Fig. Figure 2 is a graphical function block representation of the robot system. Fig. 3 is a main flowchart of a screw fastening process. Fig. Figure 4 is a graphic representation illustrating the screw fastening process. Fig. 5A is a graphical representation that schematically depicts a state after screw fastening, if the screw fastening is successful. Fig.Figure 5B is a graphical representation that shows an example of changes in fastening torque, screw fastening depth and angle over time when the screw fastening is successful. Fig. 6A is a graphical representation that schematically depicts a screw fastening condition when a fault cause is an inclined fastening. Fig. 6B is a graphical representation that schematically depicts a screw fastening condition when a cause of failure is screw float. Fig. 6C is a graphical representation that schematically depicts a screw fastening condition when a cause of failure is a pre-drilled hole defect. Fig. 7 is a schedule that represents a repetitive process that is carried out by a repetitive unit when a fault cause is an inclined fastening. Fig.8 is a schedule that represents a repetition process that is performed by the repetition unit when a fault cause is screw float. Fig. 9 is a schedule that represents a repetition process that is performed by the repetition unit when a cause of failure is a prepared bore defect. Fig. 10 is a graphical representation that shows an example of an image displayed by a display control unit on a display unit when an investigation result is successful. Fig. Figure 11 is a graphical representation that shows an example of an image displayed by the display control unit on the display unit when a detection result is error and the cause of the error is a skewed fastening. Fig.12 is a graphical representation that shows an example of an image displayed on the display unit during an execution of a repetition by the display control unit. Fig. Figure 13 is a graphical representation that provides an example of an image representing a work result of an entire screw fastening operation including a repetition operation, the image being displayed by the display control unit. Fig. Figure 14A is a graphic representation that schematically depicts a screw breakage as an example of a faulty screw fastening. Fig. Figure 14B is a graphic representation that schematically depicts a double screw fastening condition as an example of a faulty screw fastening. Fig.Figure 14C is a graphic representation that schematically depicts a case in which a screw is too short as an example of a faulty screw fastening. Description of the embodiments

[0006] Next, embodiments of the present disclosure are described with reference to the drawings. In the referenced drawings, similar components or functional parts are identified by similar reference numerals. For ease of understanding, the drawings may use different scales. Furthermore, the configurations shown in the drawings are examples of an implementation of the present invention, and the present invention is not limited to the configurations shown.

[0007] Fig. Figure 1 is a graphical representation depicting a configuration of a robot system 100 according to one embodiment. As shown in Fig.As shown in Figure 1, the robot system 100 comprises a robot 10, a robot control unit 20 that controls the robot 10, and a programming handheld device 30 connected to the robot control unit 20. A screw fastening device 60, acting as an end effector, is attached to a flange 11 of the robot 10's wrist, with a mounting plate 51 interposed between them. A force sensor (force detector) 70, which detects an external force, is located between the wrist flange 11 and the mounting plate 51. In the configuration described above, based on a detection value detected by the force sensor 70, the robot system 100 can, via the robot 10, position the screw fastening device 60 at a desired location and in a desired orientation, perform screw fastening work via the screw fastening device 60, and simultaneously cause the robot 10 to execute force control.

[0008] As an example, let's assume that robot 10 is a six-axis vertical articulated robot. It should be noted that various types of robots, such as a horizontal articulated robot, a parallel linkage robot, and a dual-arm robot, can be used as robot 10, depending on the work objective. However, a configuration example for robot 10, equipped with a screw-fastening device 60 as an end effector, is shown in Fig. As shown in Figure 1, different types of end effectors can be attached to the robot 10 according to the purpose of the work.

[0009] The robot control unit 20 controls the operation of the robot 10 according to an operating program or a command from the programming handheld device 30. The robot control unit 20 can have a hardware configuration as a general-purpose computer, which includes a processor 21 (see Fig.2) includes a memory (e.g., a ROM, a RAM, or a non-volatile memory), a storage device, an operating unit, an input / output interface, a network interface, and the like.

[0010] The programming handheld device 30 is used as an operator interface for teaching the robot 10, displaying information, and configuring various types of settings. A teaching device equipped with a tablet computer or similar device can be used as the programming handheld device 30. The programming handheld device 30 can have a hardware configuration as a general-purpose computer, including a processor, memory (e.g., ROM, RAM, or non-volatile memory), a storage device, an operator interface, and a display unit 31 (see Fig. 2) includes an input / output interface, a network interface, and the like.

[0011] As an example, it is assumed that the screw fastening device 60 is an angle-type screw fastening device (a nut wrench). The screw fastening device 60 includes a body unit 61, inside of which are a control unit 161 and a motor 162 (see Fig. 2) are included, and a head unit 62 which is connected to the tip of the body unit 61. The head unit 62 holds a sleeve 65 as a tool. The sleeve 65 holds a screw 81. The screw fastening device 60 is connected to the robot control unit 20 and fastens the screw 81 to a screw hole in a target object by rotating the sleeve 65 according to a command from the robot control unit 20.

[0012] The screw fastening device 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, with a force sensor 70 inserted between them. In this configuration, the screw fastening device 60 can be adjusted to a desired position and orientation by the robot 10, and the screw fastening operation can be performed on a target object.

[0013] For example, the force sensor 70 is a six-axis force sensor that detects a force acting on each of the mutually orthogonal x, y, and z axes, and a moment about each axis. It should be noted that, although in the present embodiment an external force acting on the robot 10 is detected by the force sensor 70, an external force can also be detected based on a detection value from a torque sensor provided on each axis of the robot instead of the force sensor.

[0014] Fig. Figure 2 is a graphical function block representation of the robot system 100. As in Fig.As shown in Figure 2, the robot control unit 20 includes an operating control unit 121, a force control unit 122, a force data processing unit 123, a determination unit 124, a repetition unit 125, a display control unit 126, and a setting unit 127. The function blocks can be functional components that are provided by the execution of a program by the processor 21 of the robot control unit 20.

[0015] The robot control unit 20 includes a memory unit 129. For example, the memory unit 129 is a storage device configured with non-volatile memory or a hard disk device. An operating program for controlling the robot 10, various types of setting information including force control parameters and an operating parameter, and the like, are stored in the memory unit 129.

[0016] The operating control unit 121 controls the operation of the robot 10 according to the operating program or a command from the programming handheld device 30. The robot control unit 20 includes a servo control unit (not shown) which performs servo control on the motor 111 on each axis according to a command to the axis generated by the operating control unit 121.

[0017] The force data processing unit 123 provides a function for calculating an external force (a force and a moment) acting on the robot 10 (the screw fastening device 60) based on a detection value from the force sensor 70. The position and orientation of the force sensor 70 can be calculated from the position and orientation of a coordinate system at the wrist tip of the robot 10 and from relative position information of the force sensor 70 with respect to the wrist tip. Based on the position, orientation, and detection value of the force sensor 70, the force data processing unit 123 can calculate the magnitude and direction of a force and a moment in any predefined coordinate system.

[0018] The force control unit 122 has a function for performing force control based on force information calculated by the force data processing unit 123 and specified force control parameters.

[0019] The operating control unit 121 has a function to cause the robot 10 to perform an operation based on force control according to a command provided by the force control unit 122.

[0020] The investigation unit 124 has a function for acquiring time series data for each of a plurality of force control parameters during the execution of a force control operation and for determining, based on the time series data, whether the work performed by the robot 10 is successful. The investigation unit 124 also has a function for analyzing and specifying a cause if a screw fastening operation is unsuccessful, based on the acquired individual time series data of the force control parameters.

[0021] The repetition unit 125 performs a repetition of a screw fastening operation based on a cause of error specified by the investigation unit 124.

[0022] The display control unit 126 provides a function for displaying various types of information about the result of the execution of the screw fastening (e.g. success / failure and a cause of the failure) based on a determination result by the determination unit 124.

[0023] The setting unit 127 provides a function for accepting input of various parameters. For example, the setting unit 127 can be configured to display a user interface for accepting input of various parameters on the display unit 31 of the programming handheld device 30 and to accept input from the control unit.

[0024] A main sequence of a screw fastening process based on force control, which is carried out by the robot control unit 20, is described with reference to Fig.3. The main process is primarily executed under the control of the processor 21 of the robot control unit 20. First, the input of various parameters required for the screw fastening process is accepted (step S1). Force control parameters and operating parameters of the screw fastening device 60 (e.g., rotational speed) are entered. Next, the robot control unit 20 (operating control unit 121) positions the screw fastening device 60 at a previously programmed starting position for the screw fastening operation by controlling the robot 10, rotates the screw fastening device 60 forward, and begins the screw fastening process based on the force control (step S2).

[0025] In force control for screw fastening, parameters such as pressing force, tightening torque, screw tightening depth, angle (an angle between the drive axis of a fastener and the centerline of a fastening hole), tightening time, and the like are set, and operational control is performed. Such parameters relating to force control are referred to herein as force control parameters. The screw fastening process is described with reference to... Fig. 4 described. An arrow A in Fig. 4 specifies a pressing direction, and the force control unit 122 performs a control such that the pressing force in the pressing direction equals a target force. A measured value of the pressing force is acquired based on a detection value from the force sensor 70.

[0026] In Fig.Figure 4 represents an angle θ, an angular error defined as the angle between the centerline C1 of a screw bore 91 and the drive axis C2 of the sleeve 65 (screw 81). The force control unit 122 performs a control operation based on a detection value from the force sensor 70 such that the angular error becomes, for example, zero; that is, the torque detected by the force sensor 70 in the direction of the angle θ becomes, for example, zero. Fig.Figure 4 further represents a position error d, which is defined as the misalignment between the center line C1 and the center of the tip of screw 81. The force control unit 122 can correct the position of the robot 10 based on the detection value of the force sensor 70 so that the position error d of screw 81 approaches zero. It should be noted that measurements of the magnitude and direction of the angle can be acquired based on the position and orientation of the robot 10 (the screw fastening device 60). For example, the mounting position of the screw fastening device 60 relative to a flange coordinate system defined for the robot 10 is known. Accordingly, the position and orientation of the screw fastening device 60 (i.e., the magnitude and direction of the aforementioned angle) can be determined based on the position and orientation of the robot 10.

[0027] The tightening torque is a torque in the direction of rotation of the screw 81. The tightening torque can be determined from a detection value of the force sensor 70 as the force or torque received by the robot 10 through the rotation of the screw tightening device 60 (sleeve 65). The screw tightening depth can be detected as the amount of movement of the sleeve 65 in the pressing direction after the robot 10 has positioned the screw 81 in a teach-in position, in which the screw tightening begins. When the tightening torque reaches a target torque value after the start of the screw tightening process, the rotation of the screw 81 can be stopped, and the screw tightening process can be terminated, assuming that the tightening process is complete. The time between the start of the screw tightening and such an end of the screw tightening process is referred to as the tightening working time.

[0028] Next, the investigation unit 124 determines whether the bolt tightening is successful (step S3). Investigation unit 124 determines whether the bolt tightening is successful or not and the cause of the failure based on changes in the detection values ​​of the force control parameters over time, their interrelationships, and the like. Details of the investigation unit 124's determination are described below. If the bolt tightening is unsuccessful (S3: YES), investigation unit 124 diagnoses the cause of the failure, and retry unit 125 performs a retry operation based on the cause of the failure (step S4). If the bolt tightening is successful (S3: NO), this processing ends.

[0029] In step S5, the repetition unit 125 determines whether every necessary repetition operation has been performed. If not every repetition has been performed (S5: NO), processing continues from step S3. If it is determined that every repetition operation has been performed (S5: YES), the investigation unit 124 performs a work determination on the repetition operation (step S6). If the work is successful (S6: YES), this processing ends. If the work is determined to be unsuccessful (S6: NO), the investigation unit 124 determines that the work failed due to an unknown cause and records the fault location (step S7).

[0030] The determination of the operating state by the determination unit 124 when the screw fastening is carried out by the robot control unit 20 (the determination in step S3), the repetitions by the repetition unit 125 based on the determination result (the repetitions based on a loop including steps S4 and S5: NO) and the display of information about the determination result by the display control unit 126 are described below.

[0031] As an example, the investigation unit 124 can determine the state of a screw fastening process based on force control using the following five criteria. (Criterion 1) Whether the screw fastening depth reaches a specified screw fastening depth (a target value). (Criterion 2) Whether the fastening torque reaches a specified target torque (Criterion 3) Whether the pressing force reaches a specified screw fastening pressing force (a target force) (Criterion 4) Whether the angle lies within a specified range of the maximum angle of the screw fastening (Criterion 5) Whether the fastening work time lies within a specified working time

[0032] Criterion 1 is a condition relating to whether the screw fastening depth (the fixing depth) reaches the target value. For example, it can be determined that Criterion 1 is met if the screw fastening depth is within a predefined range. Criterion 2 is a condition relating to whether the fastening torque reaches the target torque. For example, it can be determined that Criterion 2 is met if the detected value of the fastening torque is within a predefined range.

[0033] Criterion 3 is a condition relating to whether the pressing force reaches the target force. For example, it can be determined that criterion 3 is fulfilled if the detection value of the pressing force lies within a predefined range. Criterion 4 is a condition relating to whether the angle during screw fastening (the angle θ in Fig. 4) lies within the specified range of the maximum angle. It can be determined that criterion 4 is met if the angle during screw fastening lies within the range of the maximum angle (e.g., plus or minus a specified angle).

[0034] Criterion 5 is a condition relating to the fastening work time between the start and end of the bolt fastening process. Regarding the working time, Criterion 5 can be determined to be met if the fastening work time is within the target value, or it can be determined that Criterion 5 is met if the fastening work time is within a range between a target minimum time and a target maximum time.

[0035] For example, the investigation unit 124 determines that the bolt fastening operation is successful if all criteria 1 to 5 are met. Investigation unit 124 can determine that the bolt fastening operation is unsuccessful if one or more of criteria 1 to 5 are not met. Investigation unit 124 can perform an investigation into the operation outcome, taking into account changes in parameters related to criteria 1 to 5 over time. Alternatively, investigation unit 124 can perform an investigation into the operation outcome of the bolt fastening operation based on changes in parameters related to criteria 1 to 5 over time and the interrelationships between them.

[0036] It should be noted that, since the detection values ​​of pressing force and tightening torque can exhibit similar properties with respect to changes over time, the investigation unit 124 can determine the operation result based on four criteria, namely criteria 1, 2, 4, and 5, with the exception of criterion 3 regarding pressing force. In other words, the investigation unit 124 can determine that the bolt tightening operation is successful if all criteria 1, 2, 4, and 5 are met. The investigation unit 124 can determine that the bolt tightening operation is unsuccessful if one or more of criteria 1, 2, 4, and 5 are not met. The investigation unit 124 can perform an investigation of the operation result taking into account changes in parameters with respect to criteria 1, 2, 4, and 5 over time.Investigation Unit 124 can conduct an investigation into the outcome of the screw fastening process based on changes in parameters relating to criteria 1, 2, 4 and 5 over time and the mutual relationships between them.

[0037] Fig. Figure 5A is a graphical representation that schematically depicts a state after screw fastening, assuming the screw fastening is successful. The graphical representation shows a state in which the screw 81 is normally fastened to a target object 191. Fig. Figure 5B is a graph that illustrates an example of changes in fastening torque, screw fastening depth, and angle over time when the screw fastening is successful. Fig. 5B represents the vertical axis as the fastening torque, screw fastening depth, or angle, and the horizontal axis as a time axis. T0 and T1 on the time axis in Fig. 5B each designate a minimum working time and a maximum working time as target values ​​for the fastening working time specified as criterion 5. Fig. 5B provides an example in which a time range between the minimum working time T0 and the maximum working time T1 is specified as the target value of the fastening working time and criterion 5 is determined to be OK if the fastening working time lies within the specified time range.

[0038] A graph 201 in Fig. 5B represents changes in the angle over time. The angle changes within a preset range of the maximum angle (±θ1 degree) in a region from the beginning to the end of the screw fastening. In this case, the detection unit 124 determines that criterion 4 is OK with respect to the angle.

[0039] A graph 202 in Fig.Figure 5B depicts changes in the fastening torque and the bolt fastening depth over time. Since the fastening torque and the bolt fastening depth typically exhibit changes that increase gradually from the start of the fastening process, these changes are represented by graph 202. Normally, the fastening torque increases gradually from the start of the fastening process, as shown by graph 202, and reaches the target force within the target working time or within the range of the target working time (from T0 to T1). For example, the determination unit 124 can determine that criterion 2 is OK if the fastening torque reaches the target torque (a range from TR1 to TR2).Alternatively, the investigation unit 124 can determine that criterion 2 is OK if the fastening torque reaches the target torque within the target working time.

[0040] Normally, the screw fastening depth gradually increases from the start of the screw fastening process and reaches the target value within the target working time or within the range (from T0 to T1) of the target working time, as illustrated by graph 202. For example, the investigation unit 124 can determine that criterion 1 is OK if the screw fastening depth reaches the target value (a range from D1 to D2). Alternatively, the investigation unit 124 can determine that criterion 1 is OK if the screw fastening depth reaches the target value within the target working time.

[0041] On graph 202, the fastening torque reaches the target force in the range (from T0 to T1) of the target working time, and the bolt fastening ends. In this case, the investigation unit 124 can determine that criterion 5 is OK.

[0042] It should be noted that the pressing force can also be considered to increase gradually from the start of the screw fastening process and reaches the target force within the target working time or within the range of the target working time (from T0 to T1), similar to the fastening torque. Accordingly, the investigation unit 124 can determine that criterion 2 is OK if the pressing force reaches the target force, similar to the fastening torque. Alternatively, the investigation unit 124 can determine that criterion 2 is OK if the pressing force reaches the target force within the target working time.

[0043] Investigation Unit 124 can determine that the screw fastening is unsuccessful if one of the following conditions applies. • the screw fastening depth does not reach the target value (the range from D1 to D2) (criterion 1 is NG), • the fastening torque does not reach the target force (the range from TR1 to TR2) (criterion 2 is NG), • the pressing force does not reach the target force (the target range) (criterion 3 is NG), • the angle of the screw fastening is not within the specified range (±θ1 degrees) (criterion 4 is NG), and • The screw fastening does not end within the specified target working time (from T0 to T1) (criterion 5 is NG).

[0044] Investigation Unit 124 can specify a cause for a failed bolt fastening based on the investigation results of criteria 1 to 5, taking into account changes in the parameters with respect to the criteria over time and the relationships between them. Alternatively, Investigation Unit 124 can specify a cause for a failed bolt fastening based on the investigation results of criteria 1, 2, 4, and 5, taking into account changes in the parameters with respect to the criteria over time and the relationships between them.

[0045] Alternatively, if a screw fastening is unsuccessful, Investigation Unit 124 can specify a cause of failure based on Criterion 1, Criterion 2, and / or Criterion 4. An example of Investigation Unit 124 specifying a cause of failure based on Criterion 1, Criterion 2, and Criterion 4 is given with reference to Fig. 6A to Fig. 6C described.

[0046] Fig. Figure 6A schematically represents a screw fastening condition when the cause of the fault is an inclined fastening. In the inclined fastening condition, screw 81 is located as shown in Fig.Figure 6A shows the screw in a condition where it is fitted into and fastened in an inclined position within a screw hole in the target object 191. Accordingly, in this case, the tightening torque reaches the target torque at an early stage of the screw tightening, and the screw tightening ends at this early stage. The early stage in this case is understood to refer to a stage before the specified range of target working time is reached. The angle increases beyond the maximum angle. The screw tightening depth does not reach the target value. Accordingly, the investigation unit 124 can perform investigations on (criterion 1), (criterion 2), and (criterion 4) as the following investigation results (a1) to (a3) ​​and can determine that the cause of the screw tightening failure is an inclined tightening if investigation results (a1) to (a3) ​​are true. (a1) The fastening depth does not reach the target value, and therefore criterion 1 is NG. (a2) The fastening torque reaches the target torque, and therefore criterion 2 is OK. (a3) The angle increases beyond the maximum angle range, and therefore criterion 4 NG.

[0047] Fig.Figure 6B schematically represents a screw fastening condition when the cause of the error is screw float (fastening float). For example, screw float can occur if the underhead length of screw 81 is greater than a predefined value (a case of screw defect). In this case, when robot 10 (the screw fastening device 60) is positioned at the teach-in position where screw fastening begins, the distance between the tip of the screw and the screw hole is shorter than with a normal screw length, and a situation can arise in which the screw fastening depth, measured as the amount of movement of robot 10 (the screw fastening device 60) from the initial screw fastening position, is less than the target value.Accordingly, the investigation unit 124 can conduct investigations on (criterion 1), (criterion 2) and (criterion 4) as the following investigation results (b1) to (b3) and can determine that the cause of the screw fastening failure is screw float if the investigation results (b1) to (b3) are correct. (b1) The fastening depth does not reach the target value, and therefore criterion 1 is NG. (b2) The fastening torque reaches the target torque, and therefore criterion 2 is OK. (b3) The angle is within the maximum angle range, and therefore criterion 4 is OK.

[0048] Fig. Figure 6C schematically represents a screw fastening condition when the cause of the failure is a pre-drilled hole defect. A pre-drilled hole defect is a situation in which the upper part of a screw hole 191a in the target object 191 is deformed such that it is significantly widened, as shown in Figure 6C. Fig. 6C is shown. Accordingly, the investigation unit can carry out 124 investigations on (criterion 1), (criterion 2) and (criterion 4) as the following investigation results (c1) to (c3) and can determine that the cause of the screw fastening failure is screw float if the investigation results (c1) to (c3) are correct. (c1) The fastening depth gradually increases and reaches the target value, and therefore criterion 1 is OK. (c2) The fastening torque is practically zero until the bolt fastening progresses to a certain degree and subsequently exhibits a change in the form of an increase to the target torque. Therefore, in this case, criterion 2 is determined as NG. (c3) The angle is within the maximum angle range, and therefore criterion 4 is OK.

[0049] The above-mentioned investigation results OK / NG regarding the fastening depth (criterion 1), the fastening torque (criterion 2) and the angle (criterion 4), which have been described above, by investigation unit 124 and the correspondence between the results and the causes of failure specified by investigation unit 124 are repeated below in Table 1. Table 1 Mounting depth (Criterion 1) Fastening torque (criterion 2) Angle (Criterion 4) cause of error NG OK NG angled mounting NG OK OK Screw float OK NG OK prepared borehole defect

[0050] Thus, investigation unit 124 specifies a cause of error in OK / NG determination via the fastening depth (criterion 1), the fastening torque (criterion 2) and the angle (criterion 4), additionally taking into account changes in the force control parameters with respect to the criteria over time.

[0051] Based on a diagnostic result of a fault cause by the investigation unit 124, as described above, the repetition unit 125 performs a suitable repetition process.

[0052] Fig. Figure 7 is a sequence of operations representing a repetition process executed by the repetition unit 125 when a fault is caused by an angled mounting. The repetition process (and each repetition process described below) is executed under the control of the processor 21 of the robot control unit 20. It should be noted that the in Fig. 7 (and Fig. 8 and Fig. 9) The depicted repetition process of the repetition processing corresponds to the processing loop that includes steps S3 (S3: YES), S4 and S5 in the main process ( Fig. 3) includes.

[0053] In the retry process, a fault cause identified by the investigation unit 124 is confirmed (step S11). If a skewed fastening is identified as the fault cause (S11: YES), a process is carried out starting from step S12. In step S12, the retry unit 125 returns a screw to the initial position of the screw fastening by rotating the screw backward. Next, the retry unit 125 corrects the position and orientation of the screw in a direction opposite to the angle (a tilt direction) detected as excessive during the screw fastening and re-executes the screw fastening (step S13). In this case, the position and orientation of the screw are corrected in a direction opposite to a tilt direction in which the detected angle is maximized or where the detected angle is relatively large.

[0054] Next, the repeat unit 125 determines whether the screw fastening is successful (step S14). If the screw fastening is unsuccessful (S14: NO), the process is repeated from step S11. In a situation where a skewed fastening occurs, the repeat unit 125 performs the screw fastening by gradually adjusting the position and orientation of the screw in a direction opposite to the detected angle (one inclination direction) (one loop including steps S11 to S14: NO). If the screw fastening is successful (S14: YES), this process ends. It should be noted that if the cause of the failure is something other than a skewed fastening (S11: NO), the screw fastening is repeated based on other countermeasures (step S15). The above process resolves the skewed fastening and enables proper screw fastening.

[0055] Fig. Figure 8 is a sequence of operations representing a repetition process executed by the repetition unit 125 when a fault cause is screw float. In this repetition process, a fault cause identified by the investigation unit 124 is confirmed (step S21). If screw float is identified as the fault cause (S21: YES), an operation is performed starting from step S22. In step S22, the repetition unit 125 returns a screw to its initial position in the screw fastening by rotating the screw backward. Screw float occurs when a screw is defective. Accordingly, the repetition unit 125 automatically replaces the defective screw with another screw and re-executes the screw fastening process (step S23).

[0056] The repeat unit 125 then determines whether the screw tightening is successful (step S24). If the screw tightening is unsuccessful (S24: NO), the process is repeated from step S21. If the screw tightening is successful (S24: YES), this process ends. It should be noted that if the cause of the failure is something other than screw float (S21: NO), the screw tightening is repeated based on other countermeasures (step S25). The above process can resolve the screw float condition and enable proper screw tightening.

[0057] Fig.9 is a sequence of operations representing a repetition process executed by the repetition unit 125 when a fault cause is a prepared hole defect. In this repetition process, a fault cause identified by the investigation unit 124 is confirmed (step S31). If a prepared hole defect is identified as the fault cause (S31: YES), an operation is performed starting from step S32. In step S32, the repetition unit 125 returns a screw to its initial position in the screw fastening by reversing the screw. The repetition unit 125 then issues an alarm indicating a prepared hole defect, marks the location of the prepared hole defect on a visualized image captured by visualizing a work target object, and moves to the next work location (step S33).

[0058] The repetition unit 125 then determines whether the screw fastening is successful (step S34). If the screw fastening is unsuccessful (S34: NO), the process is repeated from step S31. If the screw fastening is successful (S34: YES), this process ends. It should be noted that if the cause of the failure is something other than a pre-prepared hole defect, the screw fastening is repeated based on other countermeasures (step S35). In the case of a pre-prepared hole defect, the above process triggers an alarm, records and displays information about the cause of the failure, and similar data.

[0059] Thus, based on a cause of error diagnosed by the investigation unit 124, the repetition unit 125 can carry out a suitable repetition process.

[0060] The following describes a function for displaying information about a determination result by the determination unit 124 via the display control unit 126. The display control unit 126 displays information about a determination result by the determination unit 124 on the display unit 31 of the programming handheld device 30.

[0061] Fig. Figure 10 shows an example of an image M1 that is displayed by the display control unit 126 on the display unit 31 when a detection result is successful. For example, image M1 can be displayed in real time when the detection is performed in step S3 of the main process. As shown in Fig.As shown in Figure 10, image M1 includes a message image 211, which contains a message indicating that the investigation result is successful, and a visualized image 212, which was captured by visualizing a work target object. A border line 213, indicating a work location on the target object, and character information 214, indicating a work number, are superimposed on the visualized image 212. By viewing image M1, a user can immediately identify the work result (OK / NG), the work location on the target object, and the work number. It should be noted that, for example, the characters "OK", the border line, and the work number character information can be displayed in green or blue if the work result is OK, to allow for immediate recognition that the work result is OK.

[0062] Fig.Figure 11 shows an example of image M2 displayed by the display control unit 126 on the display unit 31 when a detection result is "Error" and the cause of the error is a misaligned fastening. For example, image M2 can be displayed in real time when the detection is performed in step S3 of the main process. As shown in Fig.As shown in Figure 11, image M2 includes a message image 221 indicating that the investigation result is an error, and a message image 222 indicating the cause of the error. Image M2 also includes a visualized image 223, which was captured by visualizing a work target object. A frame line 224, indicating the location of the skewed fastening on the work target object, and character information 225, indicating a job number, are superimposed on the visualized image 223. By viewing image M2, a user can immediately identify the unsuccessful work, the cause (skewed fastening), the location of the work on the target object, and the job number. It should be noted that, for example, if the work result is NG, the characters "NG" and "skewed fastening," the frame line, and the job number character information may be displayed in red to allow immediate recognition that the work result is NG.

[0063] Fig. Figure 12 shows an example of an image M3, which is displayed on the display unit 31 during the execution of a repetition by the display control unit 126. The image M4 can be displayed in real time during the execution of the repetition process in step S4 in the main sequence. As shown in Fig.As shown in Figure 12, image M3 includes a message image 231 indicating that a retry is being performed, and a message image 232 indicating that the cause of the retry (the root cause of the fault) is a misaligned fastening. Image M3 also includes a visualized image 233, which was captured by visualizing a target work object. The visualized image 233 includes a border line 234 indicating a work location for the retry, and character information 235 indicating a job number. By viewing image M3, the user can immediately identify the retry operation being performed, the root cause of the fault to be resolved by the retry, and the target location and job number of the retry. For example, a border line 234 and character information 235 indicating the job number may be displayed in red to indicate that the retry is performing a recovery.

[0064] Fig.Figure 13 is an example of image M4, displayed by the display control unit 126, representing the work result of an entire screw fastening operation, including a repetition operation. For example, image M4 can be displayed in real time when processing is performed in step S6 of the main flow. As shown in Fig.As shown in Figure 13, image M4 includes a message image 241, indicating that image M4 is a result of the overall work, including a repetition, and a visualized image 242, which was captured by visualizing a work target object. Border lines 243, 245, and 247, indicating work locations, and individual character information 244, 246, and 248, indicating their work numbers, are superimposed on the visualized image 242. In image M4, each work location can be displayed in such a way that a color indicates whether the work at that location was successful or unsuccessful. For example, the display control unit 126 can display frame line 243, character information 244, frame line 245 and character information 246 in blue (or green) and frame line 247 and character information 248 in red if work numbers No. 1 and No. 2 are successful and work number No. 3 is unsuccessful.In this case, a user can immediately identify the work locations on the work target object and the work results at the work locations.

[0065] An inclined mounting, screw float, and a pre-drilled hole defect have been identified and described as examples of failure causes specified by Investigation Unit 124 in the embodiment described above. Investigation Unit 124 can specify various other failure causes besides those described above.

[0066] For example, Fig.Figure 14A schematically represents a screw breakage (fastening failure), which is a breakage of the screw 81 during the fastening of the screw 81 to a target object 191, as an example of a screw fastening failure. The investigation unit 124 can specify a failure cause based on investigation results regarding (criterion 1), (criterion 2), and (criterion 4) and changes in the force control parameters with respect to the criteria over time as follows. In particular, the investigation unit 124 can perform investigations on (criterion 1), (criterion 2), and (criterion 4) as the following investigation results (d1) to (d3) and can specify that the failure cause of the screw fastening is a screw breakage if investigation results (d1) to (d3) are true. (d1) The fastening depth gradually increases and reaches the target value, and therefore criterion 1 is OK. (d2) The fastening torque increases with the start of the screw fastening, but does not reach the target force and exhibits a change in the direction of decrease in the middle, and therefore criterion 2 NG. (c3) The angle is within the maximum angle range, and therefore criterion 4 is OK.

[0067] Fig.Figure 14B schematically represents a double bolt fastening condition, where a bolt is fastened twice at the same work location, as an example of a bolt fastening failure. Investigation Unit 124 can specify a failure cause based on investigation results regarding (Criterion 1), (Criterion 2), and (Criterion 4) and changes in force control parameters with respect to the criteria over time, as follows. In particular, Investigation Unit 124 can conduct investigations on (Criterion 1), (Criterion 2), and (Criterion 4) as the following investigation results (e1) to (e3) and can specify that the bolt fastening failure cause is a double bolt fastening if investigation results (e1) to (e3) are true. (e1) The fastening depth shows no increase and does not reach the target value, and therefore criterion 1 is NG. (e2) The fastening torque does not show a normal increase and remains at a low value, and therefore criterion 2 is NG. (e3) The angle is within the maximum angle range, and therefore criterion 4 is OK.

[0068] Fig.Figure 14C schematically presents a case where the length of a fastening is shorter than a specified value (a screw that is too short is assumed as a specific example) as an example of a bolt fastening failure. Investigation Unit 124 can specify a failure cause based on investigation results regarding (Criterion 1), (Criterion 2), (Criterion 3), and (Criterion 4) and changes in force control parameters with respect to the criteria over time, as follows. In particular, Investigation Unit 124 can perform investigations on (Criterion 1), (Criterion 2), (Criterion 3), and (Criterion 4) as the following investigation results (f1) to (f4) and can specify that the failure cause of the bolt fastening is a double bolt fastening if investigation results (f1) to (f4) are true.It should be noted that the situation in which a screw is too short is similar to that of screw floating and therefore the determination result (f4) is added and the screw is determined to be too short if the fastening working time is below a specific value. (f1) The fastening depth does not reach the target value, and therefore criterion 1 is NG. (f2) The fastening torque reaches the target value, and therefore criterion 2 is OK. (f3) The angle is within the maximum angle range, and therefore criterion 4 is OK. (f4) The fastening working time is shorter than a specific value and does not reach the target range, and therefore criterion 5 NG.

[0069] It should be noted that if the cause of the error is "a screw that is too short", the procedure is the same as the repeat procedure if the cause of the error is screw float ( Fig. 8), can be used as a repeating process.

[0070] As described above, the present embodiment enables an accurate determination, based on force control parameters, of whether a result of work based on force control is successful.

[0071] Furthermore, the present embodiment enables an operator to recognize a work result in real time during the execution of the work.

[0072] Furthermore, the present embodiment, based on changes in a plurality of force control parameters during a force control operation over time and the relationships between them, enables a precise specification of the cause of a fault in force-controlled work. The cause of the fault can also be provided to an operator in real time during the execution of the work.

[0073] Although screw fastening (fastening work) in the embodiment described above has been cited and described as an example of work based on force control, work to which the present embodiment is applicable can involve work based on various types of force control. For example, the configuration of the embodiment described above can be applied to a fitting operation. For instance, in a fitting operation, a cylindrical fitting piece is fitted into a bore formed in a mating workpiece. In this case, a press force, a fitting depth, the position of the fitting piece (the angle between the central axis of the fitting piece and the centerline of the mating bore), and the like can be used as force control parameters.Based on measured values ​​of the target values ​​of the parameters, changes in the measured values ​​of the parameters over time, relationships between them and the like, success / failure, a cause for a failure and the like of the pass work can be specified.

[0074] The functional blocks of the in Fig. The graphical function block representation shown in Figure 2 can be provided by the processor in the robot control unit executing different types of software that are stored in the memory device, or can be provided by a configuration primarily based on hardware such as an application-specific integrated circuit (ASIC).

[0075] A program that performs various types of processing according to the embodiment described above, such as screw fastening work and the repeat operation, can be recorded on various computer-readable recording media (e.g., semiconductor memories such as a ROM, an EEPROM and a flash memory; a magnetic recording medium; and optical discs such as a CD-ROM and a DVD-ROM).

[0076] Although the present disclosure has been described in detail, it is not limited to the respective embodiments mentioned above. Various additions, replacements, modifications, partial deletions, and the like may be made to the embodiments without deviating from the essential content of the present disclosure or from the scope of the present disclosure as defined by the content described in the claims and their equivalents. Furthermore, the embodiments may be implemented in combination. For example, the sequence of operations or the processing sequence in the embodiments mentioned above is described as an example and is not limited to it. The same applies if a numerical value or a mathematical expression is used in the description of the embodiments mentioned above.

[0077] The following additional remarks are further disclosed with regard to the above-mentioned embodiments and their modified examples. Supplementary Note 1

[0078] A control device (20) configured to control a robot (10), the control device (20) comprising: a force control unit (122) configured to cause the robot (10) to perform a predetermined work based on a detection value from a force detector (70) configured to detect a force and a moment acting on the robot (10), and a plurality of predetermined force control parameters, and a determination unit (124) configured to record individual time series data of the plurality of predetermined force control parameters during an execution of the force control and to determine, based on the individual time series data, whether the predetermined work is successful. Supplementary Note 2

[0079] The control device (20) according to supplementary note 1, wherein the determination unit (124) is designed to determine, on the basis of a relationship between the individual time series data, whether the specified work is successful. Supplementary Note 3

[0080] The control device (20) according to Supplementary Note 1 or 2, wherein the investigation unit (124) is designed to specify a cause based on a relationship between the individual time series data if the specified work is unsuccessful. Supplementary note 4

[0081] The control device (20) according to any one of the supplementary notes 1 to 3, wherein the specified work is a fastening work and the majority of specified force control parameters include a fastening depth, a fastening torque, an angle between a drive axis of a fastening and a centerline of a fastening hole and a fastening working time. Supplementary note 5

[0082] The control device (20) according to supplementary note 4, wherein the detection unit (124) is designed to determine that the fastening work is successful if criteria (1) to (4) are met as follows: (1) the fastening depth reaches a specified depth, (2) the fastening torque reaches a specified target torque, (3) the angle lies within a specified range of a maximum angle, and (4) The fastening work time is within a specified working time. Supplementary Note 6

[0083] The control device (20) according to supplementary note 5, wherein the detection unit (124) is designed to determine that the fastening work is unsuccessful if at least one of the criteria (1) to (4) is not met. Supplementary note 7

[0084] The control device (20) according to supplementary note 5 or 6, wherein the determination unit (124) is configured to specify a cause of failure at least on the basis of criteria (1) to (3) and the individual time series data of force control parameters with respect to criteria (1) to (3) when the specified work is unsuccessful. Supplementary Note 8

[0085] The control device (20) according to supplementary note 7, wherein the fault cause specified by the investigation unit (124) on the basis of criteria (1) to (3) and the individual time series data of force control parameters with respect to criteria (1) to (3) includes at least one element of skewed fastening, fastening float, prepared hole defect, fastening break and double screw fastening. Supplementary note 9

[0086] The control device (20) according to supplementary note 8, which further includes a repetition unit (125) designed to perform a repetition process based on force control based on the cause of the fault. Supplementary Note 10

[0087] The control device (20) according to supplementary note 9, wherein, if the cause of the fault is the inclined fastening, the repetition process includes returning the fastening to an initial fastening position by rotating the fastening backwards, and then adjusting a position of the fastening in a direction opposite to a detected inclination direction of the fastening and re-executing the fastening operation. Supplementary Note 11

[0088] The control device (20) according to Supplementary Note 9, wherein, if the cause of the fault is the fastening float, the repetition procedure includes returning the fastening to an initial fastening position by rotating the fastening backwards, and then replacing the fastening with another fastening and performing the fastening operation again. Supplementary Note 12

[0089] The control device (20) according to Supplementary Note 9, wherein, if the cause of the fault is the prepared hole defect, the repetition process includes returning the fixture to a home position of the fixture by rotating the fixture backwards, and then indicating or recording that the cause of the fault is a prepared hole defect, and moving to a next work location. Supplementary Note 13

[0090] The control device according to any of the supplementary notes 1 to 12, which further includes a display control unit (126) configured to display information about an investigation result by the investigation unit (124) on a display screen. Supplementary Note 14

[0091] The control device (20) according to Supplementary Note 13, wherein the information on the determination result displayed on the display screen includes an image indicating a success or failure of the specified work, an image indicating a cause of failure, and / or an image captured by displaying an image that indicates a work location, a work number, and a success or failure of the work on an image of a work target object. Supplementary Note 15

[0092] A robot system (100) comprising: a robot (10); a force detector (70) configured to detect a force and a moment acting on the robot; a force control unit (122) configured to cause the robot (10) to perform a predetermined work based on a detection value of the force detector (70) and a plurality of predetermined force control parameters; and a determination unit (124) configured to record individual time series data of the plurality of predetermined force control parameters during an execution of the force control and to determine, based on the individual time series data, whether the predetermined work is successful. List of reference symbols 10 robots 11 Flange 20 Robot control unit 21 processor 30 Programming handheld device 31 Display unit 60 screw fastening device 61 body unit 62 head unit 65 Sleeve 70 Force sensor 81 screw 100 robot systems 111 Engine 121 Operating control unit 122 Power control unit 123 Force Data Processing Unit 124 Investigation Unit 125 repetitions 126 Display control unit 127 Setting unit 129 storage units 161 Control unit 162 engine 212, 223, 233, 242 Visualized image QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2019-188503 A

[0002] JP 2002-331428 A

[0002]

Claims

[1] Control device designed to control a robot, wherein the control device comprises: a force control unit designed to cause the robot to perform a predetermined task based on a detection value from a force detector designed to detect a force and moment acting on the robot, and a plurality of predefined force control parameters; and an investigative unit that is trained to record individual time series data of the majority of predefined force control parameters during an execution of the force control and to determine, based on the individual time series data, whether the predefined work is successful. [2] Control device according to claim 1, wherein the determination unit is configured to determine, on the basis of a relationship between the individual time series data, whether the specified work is successful. [3] Control device according to claim 1 or 2, wherein the determination unit is configured to specify a cause based on a relationship between the individual time series data when the specified work is unsuccessful. [4] Control device according to any one of claims 1 to 3, wherein the predetermined work is a fastening work, and the plurality of predetermined force control parameters includes a fastening depth, a fastening torque, an angle between a drive axis of a fastening and a centerline of a fastening bore and a fastening work time. [5] Control device according to claim 4, wherein the detection unit is configured to determine that the fastening work is successful if the following criteria (1) to (4) are met: (1) the fastening depth reaches a specified depth, (2) the fastening torque reaches a specified target torque, (3) the angle lies within a specified range of a maximum angle, and (4) The fastening work time is within a specified working time. [6] Control device according to claim 5, wherein the detection unit is configured to determine that the fastening work is unsuccessful if at least one of the criteria (1) to (4) is not met. [7] Control device according to claim 5 or 6, wherein the determination unit is configured to specify a cause of failure at least on the basis of criteria (1) to (3) and the individual time series data of force control parameters with respect to criteria (1) to (3) when the specified work is unsuccessful. [8] Control device according to claim 7, wherein the fault cause specified by the detection unit at least on the basis of criteria (1) to (3) and the individual time series data of force control parameters with respect to criteria (1) to (3) includes at least one element of an inclined fastening, a fastening float, a prepared bore defect, a fastening break and a double screw fastening. [9] Control device according to claim 8, which further comprises a repetition unit configured to perform a repetition process based on force control based on the cause of the fault. [10] Control device according to claim 9, wherein, if the cause of the fault is the inclined mounting, the repetition process includes Returning the fastener to its initial position by rotating the fastener backwards, and then Adjusting the position of the fastening in a direction opposite to a detected inclination direction of the fastening and repeating the fastening work. [11] Control device according to claim 9, wherein, if the cause of the fault is the fastening float, the repetition process includes Returning the fastener to its initial position by rotating the fastener backwards, and then Replacing the fastening with another fastening and repeating the fastening work. [12] Control device according to claim 9, wherein, if the cause of the fault is the prepared bore defect, the repetition process includes Returning the fastener to its initial position by rotating the fastener backwards, and then Indicate or record that the cause of the failure is a prepared bore defect, and move to the next work location. [13] Control device according to any one of claims 1 to 12, which further comprises a display control unit configured to display information about an investigation result by the investigation unit on a display screen. [14] Control device according to claim 13, wherein the information about the determination result displayed on the display screen includes an image indicating a success or failure of the specified work, an image indicating a cause of failure, and / or an image captured by displaying an image that indicates a work location, a work number and a success or failure of the work on an image of a work target object. [15] Robot system that features: a robot; a force detector designed to detect a force and moment acting on the robot; a force control unit designed to cause the robot to perform a predetermined task based on a force detector recognition value and a plurality of predefined force control parameters; and an investigative unit that is trained to record individual time series data of the majority of predefined force control parameters during an execution of the force control and to determine, based on the individual time series data, whether the predefined work is successful.

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