Robot arm operation method, robot system, teaching method and program

Abstract

Provided is a method which is for operating a robot arm 20 that has a flexible drive mechanism 40 and in which the robot arm 20 is used to assemble an object W to an assembly part M, said method comprising bringing the object W held by the robot arm 20 close to the assembly part M from an oblique direction with respect to the assembly part M and performing a following operation for causing the object W to follow the assembly part M.

Description

[Technical Field]

[0001] The present invention relates to a robot arm operation method, a robot system, a teaching method, and a program. [Background technology]

[0002] In recent years, robot arms have been used to hold objects such as parts and assemble them at predetermined positions on the target object. For example, attempts have been made to use a robot arm to hold a mating object and mate it with the target object.

[0003] Patent Document 1 discloses a robot that brings a first object moved by a robot arm into contact with a second object having an insertion portion, and then rotates and translates the first object using the robot arm based on the force detection results, thereby inserting the first object into the insertion portion. With this configuration, the first object can be quickly inserted into the insertion portion of the second object, particularly even if the cross-sectional shape of the first object in a direction perpendicular to the insertion direction is not a perfect circle.

[0004] Patent Document 2 discloses that the success or failure of preliminary fitting of an insert member and a receiving member is determined based on a change in the distance between the base and the movable part of an automated assembly device, and if the preliminary fitting is unsuccessful, the insert member is retracted and rotated a predetermined amount, and then the preliminary fitting operation is performed again. With this configuration, even if the insert member and receiving member have non-circular cross sections in a direction perpendicular to the fitting direction, these members can be fitted together without any problems. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-226021 [Patent Document 2] International Publication No. 2015-181891 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in either configuration, the mating operation is performed based on contact pressure and distance changes in the robot arm or assembly device, so high-precision positioning is required, and control delays can cause damage to the target object or the assembly site. In particular, mating itself is difficult when the mating clearance is extremely small.

[0007] An exemplary object of an embodiment of the present invention is to provide a robot arm operation method, a robot system, and a program that are capable of automating high-precision assembly work. [Means for solving the problem]

[0008] In order to solve the above problems, a method for operating a robot arm according to one embodiment of the present invention is a method for assembling an object to an assembly location using a robot arm having a flexible drive mechanism, the method including bringing the object held by the robot arm close to the assembly location from an oblique direction and performing a tracing operation to cause the object to trace the assembly location.

[0009] According to the above aspect, a robot arm having a flexible drive mechanism is used to move an object held by the robot arm toward an assembly portion from an oblique direction, thereby performing a tracing operation in which the object traces the assembly portion. This makes it possible to smoothly and easily bring the object and the assembly portion into contact with each other while preventing damage to both the object and the assembly portion, and to assemble the object and the assembly portion with high precision by the tracing operation. Therefore, it becomes possible to automate high-precision assembly work.

[0010] Yet another aspect of the present invention is a robot system including a robot arm having a flexible drive mechanism and a holding mechanism capable of holding an object, and a control device for assembling the object at an assembly location using the robot arm, the control device being configured to perform a tracing operation in which the object held by the robot arm approaches the assembly location from an oblique direction and traces the object along the assembly location.

[0011] Yet another aspect of the present invention is a teaching method for teaching an operation to a robot system including a robot arm having a flexible drive mechanism and a holding mechanism capable of holding an object, and a control device for assembling the object to an assembly location using the robot arm, the teaching method teaching the robot system to move the object held by the robot arm toward the assembly location from an oblique direction and to perform a tracing operation in which the object traces the assembly location.

[0012] The teaching can be performed by methods such as online teaching or offline teaching.

[0013] Yet another aspect of the present invention is a program that is executed on a computer for assembling an object to an assembly location using a robot arm having a flexible drive mechanism, the program causing the computer to execute a tracing operation of bringing the object held by the robot arm closer to the assembly location from an oblique direction and tracing the object to the assembly location.

[0014] In addition, any combination of the above components or mutual substitution of the components or expressions of the present invention between methods, devices, systems, computer programs, data structures, recording media, etc. are also valid aspects of the present invention. [Effects of the Invention]

[0015] According to the present invention, highly accurate assembly work can be automated. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing functional blocks of a robot system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic side view of the robot arm. [Figure 3] FIG. 2 is a schematic diagram of a robot arm as viewed from above. [Figure 4] FIG. 10 is a diagram illustrating an example of a method for operating a robot arm. [Figure 5] 10 is a flowchart illustrating an example of a method for operating a robot arm. [Figure 6] FIG. 10 is a diagram for explaining an example of a tracing operation by a robot arm. [Figure 7] FIG. 10 is a diagram for explaining an example of a tracing operation by a robot arm. [Figure 8] 10A and 10B are diagrams illustrating a modified example of the operation method of the robot arm. [Figure 9] 10 is a flowchart showing another modified example of the method for operating the robot arm. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described below through embodiments of the invention with reference to the drawings, but the following embodiments do not limit the invention according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and redundant explanations will be omitted as appropriate.

[0018] Fig. 1 is a diagram showing functional blocks of a robot system according to an embodiment of the present invention, Fig. 2 and Fig. 3 are schematic diagrams of a robot arm that holds an object.

[0019] 1, the robot system 100 includes a robot arm 20, a control device 10 that controls the robot arm 20, a display device 60, and an input device 62. The robot system 100 according to this embodiment holds an insert part W, which is a fitting object (an example of an "object"), and performs a fitting operation to assemble the fitting object into an assembly portion of a mold M, which is a fitting object (an example of an "assembly portion").

[0020] The robot arm 20 holds an object, moves it toward an assembly location, and then performs an operation including a tracing operation in which the object comes into contact with the assembly location and traces it. As shown in Figures 2 and 3, the robot arm 20 is, for example, a vertical articulated robot, and includes a base (not shown), multiple links 20L, multiple joints 20J, an end effector 20E, one or more drive units 30, one or more series elastic actuators 40, and a pressure detection unit 50. However, the robot arm 20 is not limited to a vertical articulated robot, and may be, for example, a horizontal articulated robot device or a parallel link robot device.

[0021] The link 20L is made of a rigid member and includes, for example, a link 20L corresponding to the torso rotatably attached to the base, a link 20L corresponding to the lower arm rotatably attached to the torso, a link 20L corresponding to the upper arm rotatably attached to the lower arm, and a link 20L (not shown) corresponding to the wrist rotatably attached to the upper arm.

[0022] The end effector 20E (an example of a "holding mechanism") has the function of holding an object. The end effector 20E is attached to the tip of a link 20L, which corresponds to a wrist, and is configured to be able to hold an object by sandwiching it between movable plates 20E1 and 20E2 that open and close using an actuator. However, the end effector 20E is not limited to this. For example, the end effector 20E may be equipped with multiple suction pads for holding the surface of the object and actuators that generate negative pressure on the suction pads based on control signals sent from the control device 10, or may hold the object using electromagnetic force. The robot arm 20 shown as an example in this embodiment can perform a tracing operation using a drive mechanism that is distinct from the holding mechanism. Note that the end effector 20E does not necessarily need to be equipped with sensors for acquiring contact pressure or torque along six axes.

[0023] The robot arm 20 according to this embodiment includes a series elastic actuator 40 provided in at least one joint 20J that connects the links 20L. For example, the series elastic actuator 40 is mounted in all of the joints 20J of the robot arm 20.

[0024] The series elastic actuator 40 (an example of a "flexible drive mechanism") is composed of, for example, a drive unit 42 and an elastic body 44 connected to the drive unit 42. The drive unit 42 is composed of, for example, a servo motor. The elastic body 44 is composed of, for example, a mechanical spring (e.g., a leaf spring). Leaf springs have high torsional rigidity and are therefore suitable for the tracking operation of this embodiment. In the series elastic actuator 40, the power output from the drive unit 42 is transmitted via the elastic body 44 to the output-side link 20L, causing it to rotate. Furthermore, the series elastic actuator 40 of this embodiment is equipped with a sensor (not shown) for obtaining the displacement of the mechanical spring.

[0025] The pressure detection unit 50 detects the contact pressure when the robot arm 20 brings the object into contact with the assembly portion. By controlling the contact pressure detected by the pressure detection unit 50 to be substantially constant, a tracing operation can be performed to make the object trace the assembly portion.

[0026] With the above-described configuration of the robot arm 20, an equation of motion is established with parameters including the inertia, mass, and length of the part driven by the series elastic actuator 40, which corresponds to a flexible drive mechanism, external force, and the spring constant of the mechanical spring, which is the elastic body 44. Therefore, the control device 10 is configured to perform mechanical compliance control, which controls impedance based on the spring constant and displacement of the mechanical spring.

[0027] The series elastic actuator 40 may be connected to the drive shaft of a servo motor, which is the drive unit 42, and may include a gear for transmitting power to a mechanical spring. Furthermore, the series elastic actuator 40 may also include a damper mechanism that uses viscosity to absorb impacts and a clutch mechanism for switching the transmission of power. When a viscous body, such as a viscous damper mechanism, is added, a viscosity constant is added as a parameter to the equation of motion. For example, an equation of motion is established in which the viscosity constant multiplied by the change in link angle over time is considered as torque.

[0028] If there are links 20L other than the link 20L driven by the series elastic actuator 40, such links 20L are driven by a drive unit 30 configured, for example, by a servo motor. The drive unit 30 rotates the output link 20L around a drive shaft. The drive unit 30 may be mounted on the link 20L. With the above configuration, it is possible to rotate multiple links 20L, thereby changing the position and posture of the end effector 20E corresponding to the tip of the link 20L.

[0029] As shown in FIG. 1 , the control device 10 includes a control command acquisition unit 12, a tracking operation execution unit 14, an error detection unit 16, and a determination unit 18. The control command acquisition unit 12 acquires control commands for controlling the servo motors corresponding to the drive units 30 of the robot arm 20 and the servo motor of the series elastic actuator 40. The control commands are generated based on various information, including a start position and a posture at that time of a reference position of the robot arm 20 (e.g., the center point of the end effector 20E corresponding to the hand position), a target position and a posture at that time, an allowable range within which the reference position of the robot arm 20 can deviate from the target position based on the target position, and a movement path connecting the start position and one or more target positions. As will be described later, the robot arm operation method according to this embodiment can acquire a path that prevents interference between an object held by the robot arm 20 and an assembly site. The control command acquisition unit 12 acquires control commands for controlling the servo motors to move the reference position along the path by performing arithmetic processing or the like. For example, the control command acquisition unit 12 calculates the rotation angle of each servo motor for positioning the reference position on the path by inverse kinematics, and generates a control command based on this.

[0030] The tracing operation execution unit 14 elastically deforms the series elastic actuator 40 of the robot arm 20, causing the robot arm 20 to perform a tracing operation in which the robot arm 20 contacts the assembly portion and traces the object. The tracing operation refers to moving the object relative to the assembly portion while keeping the object in contact with the assembly portion. Here, the relative movement is not limited to translational movement but also includes rotational movement of the object relative to the assembly portion. The tracing operation execution unit 14 is configured to elastically deform the elastic body 44 of the series elastic actuator 40 so that the contact pressure detected by the pressure detection unit 50 is substantially constant or within a predetermined range. This allows the assembly work to be performed while suppressing damage, such as galling, to the object or the assembly portion.

[0031] The error detection unit 16 detects error information based on the measurement value of the contact pressure detected by the pressure detection unit 50 during operation of the robot arm 20. For example, if the pressure detection unit 50 detects that the measurement value of the contact pressure during a tracing operation exceeds a threshold value, the error detection unit 16 determines that there is some kind of defect in the object or the assembly part, and detects error information.

[0032] The determination unit 18 determines the operation of the robot arm 20 after the error based on the error content of the error information detected by the error detection unit 16. Specifically, if the first error information occurs for the first time during the tracing operation, the determination unit 18 causes the robot arm 20 to replace the object and then perform the tracing operation again. On the other hand, if the second error information occurs during the tracing operation again after the object has already been replaced, the determination unit 18 stops the operation of the robot arm 20. If the first error information is detected, it is likely that the error is an abnormality of the object itself, such as a foreign object adhering to the object, and therefore the error problem may be resolved by causing the robot arm 20 to perform the tracing operation again. On the other hand, if the second error information is detected, it is likely that the error is an abnormality of the manufacturing lot unit or the assembly portion itself of the object, and therefore the error problem is likely not resolved even if the object is replaced. Therefore, in such a case, the operation of the robot arm 20 is stopped. Note that the second error information is not limited to the second error, and may be the third or subsequent error. Information according to the type of error determined by the determining unit 18 of the control device 10 (particularly the second error information) may be displayed on the display device 60 to notify the user.

[0033] Regarding the hardware configuration, the control device 10 may be configured from a computer including, for example, a processor such as a central processing unit (CPU) or a graphical processing unit (GPU), a volatile memory such as a static random access memory (SRAM) or a dynamic random access memory (DRAM), a nonvolatile memory such as a NOR flash memory, a NAND flash memory, or a hard disk drive (HDD), and a communication means such as a bus connecting these. The nonvolatile memory stores, for example, computer programs for executing the processes described in this embodiment. The volatile memory temporarily stores at least a portion of these computer programs and the results of arithmetic processing. However, at least a portion of these computing elements, nonvolatile memory elements, etc. may be installed in remote locations connected to a communication network such as the Internet. For example, the computing elements may be configured to obtain computer programs or necessary data via the communication network.

[0034] The control device 10, robot arm 20, display device 60, and input device 62 are configured to be able to send and receive information via wireless or wired communication means. A teaching device (not shown) for teaching the robot system 100 to perform an operation may be connected to the control device 10. The display device 60 and input device 62 may be a computer equipped with a display unit and an input unit, or may be configured as an integrated device such as a touch panel.

[0035] Next, as an example of an operation method of the robot arm 20 according to this embodiment, a method of fitting an insert part W (an example of an "object") into a mold M (an example of an "assembly portion") having a cylindrical recess formed therein will be described. FIGS. 2 and 3 are schematic side and top views showing how the robot arm 20 fits the object, which is the insert part W, into the recess of the mold M. FIGS. 4(a) to 4(d) show a series of steps in the operation method of the robot arm 20. For ease of explanation, each figure shows a coordinate system in which the vertical direction is the Z-axis direction and the horizontal directions are the X-axis and Y-axis directions. In the following explanation, the insertion axis of the insert part W when inserted into the recess of the mold M coincides with the Z-axis direction.

[0036] 2 and 3, the robot arm 20 includes a link 20L corresponding to a torso rotatably attached to a base, a link 20L corresponding to a lower arm rotatably attached to the torso, a link 20L corresponding to an upper arm rotatably attached to the lower arm, a link 20L (not shown) corresponding to a wrist rotatably attached to the upper arm, an end effector 20E capable of holding an object by sandwiching it between movable plates 20E1 and 20E2, and a joint 20J connecting the links 20L. For example, a series elastic actuator 40 is mounted on the joint 20J connecting the links 20L. In other words, all six-axis drive mechanisms, including translational force components along the X-, Y-, and Z-axes and rotational force components about each of these three axes, are equipped with a series elastic actuator 40.

[0037] The insert part W is formed, for example, in a disk shape. The cylindrical recess formed in the mold M is formed, for example, to be slightly larger (for example, 50 μm larger) than the diameter of the insert part W.

[0038] Conventionally, it has been difficult to fit such objects using the robot arm 20. When holding the side of the object with the end effector 20E, it is necessary to move the object, which is a disk, directly above the recess and then release the hold to allow the object to fall so that the end effector 20E does not interfere with the assembly site. However, if the gap between the object and the recess is small, the object cannot be inserted into the recess even if it is tilted even slightly.

[0039] In contrast, the method of operating the robot arm 20 disclosed in the present disclosure makes it possible to automate highly accurate assembly work.

[0040] Here, a specific process will be described below with reference to FIGS. 4(a) to 4(d) and 5. As shown in FIG. 4(a), the end effector 20E of the robot arm 20 holds the insert part W by pinching the top and side surfaces of the insert part W (S11 in FIG. 5). Next, the robot arm 20 moves the insert part W and brings it closer to the recess of the mold M from an oblique direction (S12 in FIG. 5). Specifically, the insert part W approaches the recess of the mold M from a direction inclined at a predetermined approach angle θ (0°<θ<90°) with respect to the Z-axis direction, which is the insertion axis of the insert part W when inserted into the recess of the mold M. The approach angle θ can be set appropriately depending on, for example, the inclination angle of the insert part W held by the end effector 20E and the respective shapes of the insert part W and the recess of the mold M. By bringing the insert part W into contact with the recess of the mold M at an oblique direction with a predetermined contact pressure, the copying operation can be started without damaging either the insert part W or the mold M. The approach of the insert part W from an oblique direction by the robot arm 20 is performed based on a control command acquired by the control command acquisition unit 12 of the control device 10.

[0041] As shown in FIG. 4(b), the robot arm 20 brings the side surface of the insert part W into contact with the corner of the opening end of the recess of the mold M (S13 in FIG. 5). Next, while maintaining the state in which the side surface of the insert part W is in contact with the corner of the opening end of the recess of the mold M, the robot arm 20 performs a tracing operation to insert the insert part W into the recess of the mold M (S14 in FIG. 5). Thereafter, the robot arm 20 rotates the insert part W around the Y axis relative to the recess of the mold M, using the side surface of the insert part that is in contact with the corner of the recess as a fulcrum, thereby causing the insert part W to further trace the recess of the mold M.

[0042] As shown in Figure 4(c), the robot arm 20 rotates the insert part W by applying a rotational force around the Y axis until the insert part W becomes horizontal. In this case, the insert part W may be rotated, or may simply be rotated without being rotated. By rotating the insert part W with the side surface of the insert part W in contact with the recess, it is possible to reduce the possibility that the insert part W will protrude outside the recess of the mold M when the insert part W becomes horizontal.

[0043] Thereafter, as shown in FIG. 4(d), the robot arm 20 presses the surface of the insert part W to fit the insert part W into the recess of the mold M (S15 in FIG. 5).

[0044] As described above, according to this embodiment, a robot arm 20 having a flexible drive mechanism is used to move an object held by the robot arm 20 toward an assembly location from an oblique direction, performing a tracing operation in which the object traces the assembly location. This allows smooth and easy contact between the object and the assembly location while preventing damage to both the object and the assembly location, and the object and the assembly location can be assembled with high precision by the subsequent tracing operation. This makes it possible to automate high-precision assembly work. Furthermore, by using a robot arm 20 having a flexible drive mechanism, it is possible to prevent damage to the surface of the object even when the surface of the object is pressed.

[0045] In the above embodiment, the insert part W is brought into close contact with the recess of the mold M from an oblique direction, but the present invention is not limited to this embodiment and also includes an embodiment in which the insert part W is brought into close contact with the recess of the mold M from an oblique direction toward a position away from the recess. Below, a modified example of this embodiment will be described with reference to Figs. 6 and 7.

[0046] Specifically, as shown in FIGS. 6 and 7 , the insert part W held by the robot arm 20 may be moved diagonally toward the mold M in the X-axis direction, with the target position being a position where the insert part W passes over the recess of the mold M. The insert part W approaches the mold M and contacts the target position. FIG. 6 is a schematic diagram illustrating the difference between the target position and the actual position when the end of the insert part W contacts the surface of the mold M. In the figure, the end effector 20E and the insert part W held thereby when the reference position is at the target position are indicated by dashed lines. Meanwhile, the actual end effector 20E and the insert part W held thereby when the reference position is spaced from the target position are indicated by solid lines. As indicated by the dashed lines, the insert part W held by the end effector 20E interferes with the mold M at the target position. In reality, the end of the insert part W contacts the surface of the mold M due to the presence of an object. The displacement D1 corresponds to the amount of elastic deformation of the elastic body 44 of the series elastic actuator 40. At this time, a force based on the displacement amount and the spring constant acts from the insert part W to the mold M. After the end of the insert part W comes into contact with the surface of the mold M, the robot arm 20 performs a copying operation. Specifically, while maintaining the insert part W in contact with the mold M, the robot arm 20 moves the insert part W in the X-axis direction indicated by the arrow in FIG. 6 toward the recess of the mold M, and brings the side of the insert part W into contact with a corner of the opening end of the recess of the mold M shown in FIG. 7.

[0047] FIG. 7 is a schematic diagram showing the target position when the side of the insert part contacts the corner of the opening end of the recess in the mold M. In this figure, the end effector 20E and the object held by it at the target position are indicated by dashed lines, while the actual end effector 20E and the object held by it are indicated by solid lines. As indicated by the dashed lines, the insert part W held by the end effector 20E interferes with the mold M at the target position. However, in reality, the presence of the mold M causes the side of the insert part W to contact the corner of the opening end of the mold M. The displacement D2 corresponds to the amount of elastic deformation of the elastic body 44 of the series elastic actuator 40. At this time, a force based on the displacement and spring constant acts from the object to the target. The target position may be set so that the displacement D2 is greater than the displacement D1, thereby increasing the force acting from the insert part W on the mold M and improving the stability of the insert part W. Next, the robot arm 20 performs a copying operation to insert the insert part W into the recess of the mold M while maintaining the side surface of the insert part W in contact with the corner of the opening end of the recess of the mold M. The contents described with reference to FIGS. 4(b) to 4(d) and 5 can be applied to the subsequent processing. The contents described with reference to FIG. 7 can also be applied to the copying operation (S14) in FIGS. 4(b) and 5. That is, the copying operation according to this embodiment includes moving the insert part W to a position where the insert part W interferes with the mold M. The contents described with reference to FIGS. 4(a), 4(b), and 4(d) can be applied to each of the operations in FIGS. 8(a), 8(b), and 8(d).

[0048] Next, with reference to Figures 8(a) to 8(d), a further modified example of the operating method of the robot arm 20 will be described. In the example shown below, the copying operation includes a rotation operation (see Figure 8(c)) about the Z axis, which is the insertion direction into the recess of the mold M, when inserting the insert part W into the recess of the mold M, but other configurations can be applied by appropriately combining the contents described in any of the above embodiments.

[0049] Specifically, first, as shown in FIG. 8( a), the end effector 20E of the robot arm 20 holds the insert part W by pinching the top and side surfaces of the insert part W. Next, the robot arm 20 moves the insert part W and approaches it obliquely to the recess of the mold M, so that the side surface of the insert part W comes into contact with the corner of the opening end of the recess of the mold M, as shown in FIG. 8( b). In this manner, the robot arm 20 performs a tracing operation to insert the insert part W into the recess of the mold M while maintaining the side surface of the insert part W in contact with the corner of the opening end of the recess of the mold M. At this time, as shown in FIG. 8( c), the insert part W is rotated around the Z axis relative to the recess of the mold M, which is the insertion direction into the recess of the mold M. At this time, while rotating the insert part W around the Z axis toward the recess of the mold, pressure can be applied in the Z axis direction toward the recess. Because the robot arm 20 has a flexible drive mechanism, it can adjust the insert part W so that the outer shapes of the XY plane match with the recess of the mold M, while maintaining a predetermined contact pressure that suppresses damage to both, in both the rotational movement around the Z axis and the pressure movement in the Z axis direction. Thereafter, as shown in FIG. 8(d), the robot arm 20 presses the surface of the insert part W to fit the insert part W into the recess of the mold M.

[0050] According to this embodiment, it is possible to assemble the insert part W into the recess of the mold M with high precision, especially when the shape of the insert part W in the XY plane is asymmetric.

[0051] Next, another modified example of the operation method of the robot arm 20 will be described with reference to Fig. 9. In the example shown below, the operation when an error is detected during the tracing operation differs from that of the above-described embodiments, but the contents already described can be applied to the other operations.

[0052] If the copying operation of the robot arm 20 does not proceed after the robot arm 20 brings the insert part W into contact with the mold M, the error detection unit 16 determines that there is some defect in the insert part W or the mold M and detects first error information (S20 YES). One example of the case in which the first error information is detected is when the pressure detection unit 50 detects a measured value of the contact pressure during the copying operation that exceeds a threshold value, and the copying operation of the robot arm 20 is interrupted.

[0053] Next, the determination unit 18 commands the robot arm 20 to replace the insert part W based on the fact that the error information from the error detection unit 16 is first error information that has occurred for the first time during the copying operation, and the robot arm 20 replaces the insert part W with another insert part W (S21). Thereafter, the copying operation execution unit 14 controls the robot arm 20 to perform the copying operation again with respect to the replaced insert part W (S22).

[0054] Then, if the copying operation of the robot arm 20 does not progress again during the second copying operation after the insert part W is replaced, the error detection unit 16 determines that there is some defect in the insert part W or the mold M and detects second error information (S23 YES). One mode of detecting the second error information is, for example, when the pressure detection unit 50 detects a measured value of the contact pressure during the copying operation that exceeds a threshold value, and the copying operation of the robot arm 20 is interrupted. Note that the mode of detecting the error information is not limited to the above-mentioned detection of the contact pressure, and may also be detection of position information or image information acquired by an imaging device, and the mode is not limited thereto.

[0055] Thereafter, the determination unit 18 stops the operation of the robot arm 20, including the copying operation, based on the fact that the error information from the error detection unit 16 is second error information that occurred during the second copying operation (S24). The second error information means that the copying operation of the robot arm 20 will not proceed even if the insert parts W are replaced. Therefore, the detection of the second error information means that there is a high possibility that multiple insert parts in the production lot are defective or that a defect has occurred in the mold M, which is the assembly part. Since there is a high possibility that the error problem will not be resolved even if the insert parts W are replaced again, the robot arm 20 stops its operation. In this case, the control device 10 may display information on the display device 60 that the operation of the robot arm 20 has stopped, or that there is a high possibility that multiple insert parts in the production lot are defective or that a defect has occurred in the mold M, which is the assembly part.

[0056] In FIG. 9, if no error information is detected in step S20 (S20 NO), and if no error information is detected in step S23 (S23 NO), the process returns to the tracing operation (S14) in FIG. 5 and continues the tracing operation.

[0057] According to the above embodiment, even if the tracing operation of the robot arm 20 does not progress, if first error information is detected, the robot arm 20 automatically replaces the insert part W and performs the tracing operation again, and only when second error information is detected does the operation of the robot arm 20 stop, thereby reducing manual work as much as possible and improving the automation of assembly using the robot arm.

[0058] As described above, a robot arm operation method according to one embodiment of the present invention is a robot arm operation method for assembling an object to an assembly location using a robot arm having a flexible drive mechanism, and includes bringing the object held by the robot arm close to the assembly location from an oblique direction, and performing a tracing operation to cause the object to trace the assembly location.

[0059] According to this, a robot arm having a flexible drive mechanism is used to bring an object held by the robot arm close to an assembly portion from an oblique direction, and a tracing operation is performed to cause the object to trace the assembly portion, thereby making it possible to smoothly and easily bring the object and the assembly portion into contact with each other while preventing damage to both the object and the assembly portion, and to assemble the object and the assembly portion with high precision by the tracing operation. Therefore, it becomes possible to automate high-precision assembly work.

[0060] In the above aspect, the drive mechanism includes a series elastic actuator.

[0061] In the above aspect, the conforming operation includes causing the object to conform to the assembly portion while elastically deforming the elastic body of the series elastic actuator.

[0062] In the above aspect, the elastic body of the series elastic actuator is made up of a leaf spring.

[0063] In the above aspect, the drive mechanism includes at least one of a magnetic fluid, a mechanical spring, an air spring, a magnetic spring, and a vane motor for imparting flexibility.

[0064] In the above aspect, the copying operation includes moving the object to a position where the object interferes with the assembly portion.

[0065] In the above aspect, the tracing operation includes performing a rotation operation in the insertion direction into the assembly portion when the object is advanced into the assembly portion.

[0066] In the above aspect, the method includes the robot arm replacing the object with another object based on first error information detected during the copying operation, performing the copying operation again to assemble the other object held by the robot arm to the assembly location, and stopping the operation of the robot arm based on second error information detected during the copying operation again.

[0067] A robot system according to one embodiment of the present invention includes a robot arm having a flexible drive mechanism and a holding mechanism capable of holding an object, and a control device for assembling the object to an assembly location using the robot arm, the control device being configured to perform a tracing operation in which the object held by the robot arm approaches the assembly location from an oblique direction and traces the object to the assembly location.

[0068] A program according to one embodiment of the present invention is a program executed on a computer for assembling an object to an assembly location using a robot arm having a flexible drive mechanism, and causes the computer to perform a tracing operation of bringing an object held by the robot arm close to the assembly location from an oblique direction and tracing the object to the assembly location.

[0069] The present invention is not limited to the above-described embodiment and can be applied in various modifications. Any of the aspects described in the above-described embodiment and modifications can be applied in combination with other aspects as long as it is not inconsistent with the understanding of a person skilled in the art.

[0070] In the above embodiment, the mode in which the insert part W is fitted into the recess of the mold M has been described. However, the present invention can also be applied to various other uses, such as holding a flange (an example of an "object") in which a through hole is formed, and assembling the flange to a shaft (an example of an "object") by conforming the wall surface of the through hole to the surface of the shaft (an example of an "object") so that the shaft passes through the through hole; holding a printed wiring board (an example of an "object") to be inspected, and inspecting the inner diameter of a through hole formed in the printed wiring board by conforming the wall surface of a rod-shaped inspection tool (an example of an "object") so that the inspection tool passes through the through hole; and assembling an optical component such as a lens module (an example of an "object") to a precision instrument (an example of an "object").

[0071] In addition to the series elastic actuator, various other driving mechanisms can be used as flexible driving mechanisms. Here, "flexible" refers to having elasticity, viscosity, or both elasticity and viscosity. Elasticity refers to the property of being deformed when stress is applied and returning to its original shape when the stress is removed, and is sometimes expressed as flexibility, which indicates the ease of elastic deformation. Viscosity refers to the property of generating stress that equalizes the flow rate of a fluid. To impart viscosity and elasticity, magnetic fluids, mechanical springs (leaf springs, torsion coil springs), air springs, magnetic springs, vane motors, variable dampers using electrorheological fluids whose viscosity can be adjusted according to the applied voltage, and the like may be used.

[0072] The embodiments described through the above embodiments of the invention can be combined, modified, or improved as appropriate depending on the application, and the present invention is not limited to the above-described embodiments. It is clear from the claims that such combinations, modifications, or improvements are also included within the technical scope of the present invention. [Explanation of symbols]

[0073] 10...control device, 20...robot arm, 30...drive unit, 40...series elastic actuator, W...insert part, M...mold

Claims

1. A method for operating a robot arm, which assembles an object at an assembly site using a robot arm having a flexible drive mechanism, comprising: bringing the object held by the robot arm closer to the assembly site from an oblique direction; performing a tracing operation of tracing the object relative to the assembly portion; Including, The assembly portion has a recess, The object is brought close to the assembly portion from an oblique direction, the object held by the robot arm is brought close to a corner of an opening end of the recess of the assembly portion from an oblique direction in a state where the object is not in contact with the assembly portion, the tracing operation includes inserting the object into the recess while maintaining the object in contact with a corner of an opening end of the recess. How it works.

2. The method of claim 1 , wherein the drive mechanism comprises a series elastic actuator.

3. The operating method according to claim 2 , wherein the following operation includes causing the object to follow the assembly portion while elastically deforming an elastic body of the series elastic actuator.

4. A method of operating a robot arm, in which an object is assembled to an assembly location using a robot arm having a flexible drive mechanism, comprising: bringing the object held by the robot arm closer to the assembly site from an oblique direction; performing a tracing operation of tracing the object relative to the assembly portion; Including, the drive mechanism comprises a series elastic actuator; the tracing operation includes causing the object to trace the assembly portion while elastically deforming an elastic body of the series elastic actuator, the elastic body of the series elastic actuator is composed of a leaf spring; How it works.

5. The method of claim 1 , wherein the drive mechanism comprises at least one of a magnetic fluid, a mechanical spring, an air spring, a magnetic spring, and a vane motor to provide the flexibility.

6. The operating method according to claim 1 , wherein the tracing operation includes moving the object to a position where the object interferes with the assembly portion.

7. The operating method according to claim 1 , wherein the tracing operation includes performing a rotation operation of the object relative to an insertion direction into the assembly portion when the object is advanced into the assembly portion.

8. replacing the object with another object by the robot arm based on first error information detected during the tracing operation; performing a copying operation again to assemble the other object held by the robot arm to the assembly position; The robot arm stops its operation based on second error information detected during the second tracing operation. A method of operation according to any one of claims 1 to 7, comprising:

9. a robot arm having a flexible drive mechanism and a holding mechanism capable of holding an object; a control device for assembling the object at an assembly location using the robot arm; Equipped with The control device bringing the object held by the robot arm close to a corner of an opening end of a recessed portion of the assembly portion from an oblique direction while the object is not in contact with the assembly portion; performing a tracing operation in which the object is caused to trace the assembly portion and enters the recess while maintaining a state in which the object is in contact with a corner portion of an opening end of the recess; 1. A robotic system configured to:

10. a robot arm having a flexible drive mechanism and a holding mechanism capable of holding an object; a control device for assembling the object to an assembly portion using the robot arm, bringing the object held by the robot arm close to a corner of an opening end of a recessed portion of the assembly portion from an oblique direction while the object is not in contact with the assembly portion; performing a tracing operation in which the object is caused to trace the assembly portion and enters the recess while maintaining a state in which the object is in contact with a corner portion of an opening end of the recess; and instructing the robot system to execute the above. Teaching methods.

11. A program executed on a computer for assembling an object at an assembly site using a robot arm having a flexible drive mechanism, The computer, bringing the object held by the robot arm close to a corner of an opening end of a recessed portion of the assembly portion from an oblique direction while the object is not in contact with the assembly portion; performing a tracing operation in which the object is caused to trace the assembly portion and enters the recess while maintaining a state in which the object is in contact with a corner portion of an opening end of the recess; A program to execute.

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