JP7479976B2 - Robot arm operation method, robot system, control device and program - Google Patents

Description

The present invention relates to a robot arm operation method, a robot system, a control device, and a program.

In recent years, robot arms have been used to grasp objects such as parts and assemble them in a predetermined position on an object to be assembled. For example, attempts have been made to grasp a fitting object using a robot arm and fit it into the object to be assembled.

Patent document 1 discloses a robot that fits a fitting part into a mated part, and if it determines that there is a jamming condition during the fitting process, it continues the insertion operation and applies a vibration force, the magnitude and direction of which change periodically, to the fitting part via a gripping means.

Patent document 2 discloses an automatic assembly device that, when a detection unit detects an abnormality in part mounting, temporarily retracts the part gripping unit of the assembly robot outside the assembly station and causes the assembly robot to remount the part or continue the operation in a predetermined procedure according to external instructions.

JP 2008-264910 A JP 59-205240 A

However, when applying a vibration force to the mating parts as in Patent Document 1, the vibration force is applied to the sliding surface, and there is a possibility that the parts may be damaged due to friction, wear, etc. Furthermore, when the part gripper is temporarily retracted outside the assembly station as in Patent Document 2, unless the retracted parts are aligned, the accuracy of the assembly will decrease even if the assembly is performed again.

One exemplary objective of an embodiment of the present invention is to provide a robot arm operation method, robot system, control device, and program that are capable of automating high-precision assembly work.

To solve the above problem, an operating method of a robot arm according to one embodiment of the present invention includes, when galling is detected during a first assembly control of an object grasped by a robot arm having a flexible drive mechanism, placing the object in a temporary storage area by a tracing operation, grasping the object placed in the temporary storage area by the robot arm, and starting a second assembly control of the object.

According to the above aspect, when a robot arm having a flexible drive mechanism is used and galling is detected during the first assembly control of an object grasped by the robot arm, the object is placed in a temporary storage area, thereby reducing the possibility of damage to the object or the assembly part. In addition, since the object is placed in the temporary storage area by a tracing motion, the placement control can be performed with high accuracy.

Yet another aspect of the present invention is a robot system. The robot system includes a robot arm having a flexible drive mechanism, and a control device for controlling the robot arm, which executes the steps of placing the object in a temporary storage area by a tracing operation when galling is detected during a first assembly control of an object grasped by the robot arm, grasping the object placed in the temporary storage area by the robot arm, and starting a second assembly control of the object.

Yet another aspect of the present invention is a control device. This control device is configured to execute the steps of placing the object in a temporary storage area by a tracing operation, gripping the object placed in the temporary storage area with the robot arm, and starting a second assembly control of the object when galling is detected during a first assembly control of an object grasped by a robot arm having a flexible drive mechanism.

Yet another aspect of the present invention is a program. This program causes a computer to generate control instructions for executing the steps of placing the object in a temporary storage area by a matching operation, gripping the object placed in the temporary storage area with the robot arm, and starting a second assembly control of the object when galling is detected during a first assembly control of an object gripped by a robot arm having a flexible drive mechanism.

In addition, any combination of the above components or the 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.

The present invention makes it possible to automate highly accurate assembly work.

FIG. 1 is a diagram showing functional blocks of a robot system according to an embodiment of the present invention. FIG. 2 is a schematic side view of the robot arm. FIG. 2 is a schematic diagram showing a robot arm as viewed from above. FIG. 1 is a schematic diagram of the temporary storage site seen from above. 1A to 1C are diagrams illustrating a tracing operation by the robot arm 20. 13A to 13C are diagrams illustrating another aspect of the tracing operation by the robot arm 20. 1 is a flowchart illustrating an example of a method for operating a robot arm. 1 is a flowchart illustrating an example of a method for operating a robot arm. 1A to 1C are schematic diagrams showing an example of a method of operating a robot arm. FIG. 13 is a schematic diagram of a temporary storage site according to a modified example, as viewed from above. 1 is a flowchart illustrating an example of a method for operating a robot arm. 1A to 1C are schematic diagrams showing an example of a method of operating a robot arm.

The present invention will be described below through embodiments of the invention with reference to the drawings. However, 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 reference numerals are used to denote the same or equivalent components, parts, and processes shown in each drawing, and duplicate descriptions will be omitted as appropriate.

Figure 1 is a diagram showing the functional blocks of a robot system according to one embodiment of the present invention. Figures 2 and 3 show schematic diagrams of a robot arm that grasps an object W.

1, the robot system 100 includes a robot arm 20, a control device 10 for controlling the robot arm 20, a display device 60, and an input device 62. The robot system 100 according to the present embodiment grasps an object W to be assembled, and performs an operation of assembling the object W to an assembly portion R1 of a mold M1, which is an example of an object to be assembled. Here, the manner of assembly is not particularly limited, but may include, for example, fitting. The shape of the object W is not particularly limited, but as an example, in FIG. 2 and FIG. 3, it is formed in a substantially cylindrical shape. In addition, the shape of the assembly portion R1 can be arbitrarily configured according to the manner of assembly, but as an example, in FIG. 2 and FIG. 3, it is configured as a recess for fitting the object W, that is, a substantially cylindrical recess slightly larger than the dimensions of the object W.

The robot system 100 according to this embodiment further executes temporary placement control to place the target object W in a specified temporary placement area if galling is detected during assembly control. In Figs. 2 and 3, as an example, a temporary placement area R2 provided on the stage M2 is shown. The shape of the temporary placement area R2 is not particularly limited, but as an example in Figs. 2 and 3, it is configured as a recess having a substantially trapezoidal bottom surface whose dimensions are larger than those of the assembly site R1.

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, and one or more series elastic actuators 40. 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.

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

The end effector 20E (an example of a "gripping mechanism") has a function of gripping an object W. The end effector 20E is attached to the tip of a link 20L that corresponds to a wrist portion, and is configured to be able to grip the object W by sandwiching it between movable plates 20E1 and 20E2 that are opened and closed by an actuator, for example. However, the end effector 20E is not limited to this, and may be, for example, one that includes multiple suction pads for gripping the surface of the object W and an actuator that generates negative pressure on the suction pads based on a control signal transmitted from the control device 10, or one that grips the object W by electromagnetic force. The robot arm 20 shown as an example in this embodiment can perform assembly control and temporary placement control by a drive mechanism that is distinct from the gripping mechanism.

The robot arm 20 according to this embodiment is equipped with a series elastic actuator 40 provided in at least one joint 20J that connects the links 20L together. For example, the series elastic actuator 40 is mounted on all of the joints 20J of the robot arm 20. In other words, all of the drive mechanisms for the six axes, including the translational force components of the X-axis, Y-axis, and Z-axis, and the rotational force components about each of these three axes, are equipped with a series elastic actuator 40.

The series elastic actuator 40 (an example of a "flexible drive mechanism") is composed of, for example, a drive unit 42, an elastic body 44 connected to the drive unit 42, and a sensor 46. 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). The leaf spring has high torsional rigidity and is therefore suitable for the tracing operation described later in this embodiment. The power output from the drive unit 42 in the series elastic actuator 40 is transmitted to the output side link 20L via the elastic body 44, causing it to rotate. The sensor 46 acquires information for detecting galling. For example, when detecting galling based on torque, the sensor 46 is composed of a displacement sensor for acquiring the displacement amount of the mechanical spring as information indicating the torque when the target object W contacts the assembled object by the robot arm 20. Furthermore, the series elastic actuator 40 according to this embodiment is equipped with a sensor (not shown) for acquiring the displacement amount of the mechanical spring.

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 driving 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 that controls impedance based on the spring constant and displacement of the mechanical spring.

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 that transmits power to a mechanical spring. Furthermore, the series elastic actuator 40 may include a damper mechanism that absorbs impacts based on viscosity, and a clutch mechanism for switching the transmission of power. When a viscous body such as a damper mechanism having viscosity 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 the link angle over time is considered as the torque.

When 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 consisting of, for example, a servo motor. The drive unit 30 rotates the output side link 20L around the 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, and therefore it is possible to change the position and posture of the end effector 20E corresponding to the tip of the link 20L.

The control device 10 includes a control command acquisition unit 11, an assembly control execution unit 12, a jam detection unit 13, an error processing unit 14, and a temporary placement control execution unit 15.

The control command acquisition unit 11 acquires control commands for controlling the servo motors corresponding to the drive units 30 of the robot arm 20 and the servo motors of the serial elastic actuator 40. The control commands are generated based on various information including the start position and posture at that time of the reference position of the robot arm 20 (for example, the center point of the end effector 20E corresponding to the hand tip position), the target position and posture at that time, the allowable range in which the reference position of the robot arm 20 can deviate from the target position based on the target position, and the movement path connecting the start position and one or more target positions. As will be described later, in the operation method of the robot arm according to this embodiment, it is possible to acquire a path in which the object W grasped by the robot arm 20 interferes with the assembly part and/or the temporary storage area. The control command acquisition unit 11 acquires control commands for controlling each servo motor to move the reference position along the path by arithmetic processing or the like. For example, the control command acquisition unit 11 calculates the rotation angle of each servo motor for positioning the reference position on the path by inverse kinematics calculation (inverse kinematics), and generates a control command based on the calculated rotation angle.

The assembly control execution unit 12 executes assembly control to assemble the object W grasped by the robot arm 20 to the assembly part. For example, in the assembly control, the assembly control execution unit 12 elastically deforms the series elastic actuator 40 of the robot arm 20, so that the robot arm 20 executes a tracing operation in which the object W contacts the assembly part and traces it. Here, the tracing operation in the assembly control means moving the object W relatively to the assembly part while bringing the object W into contact with the assembly part. Here, the relative movement is not limited to translational movement, but includes rotating the object W relatively to the assembly part. The assembly control execution unit 12 is configured to elastically deform the elastic body 44 of the series elastic actuator 40 so that the contact pressure detected by the sensor 46 is substantially constant or within a predetermined range. This makes it possible to execute the assembly work while suppressing damage such as galling to the object W or the assembly part.

The galling detection unit 13 detects galling based on information acquired from the sensor 46. For example, the galling detection unit 13 is configured to acquire information indicating the amount of displacement of the elastic body 44 of the series elastic actuator 40 from the sensor 46, and detect galling when the rotational torque acquired based on this exceeds a predetermined threshold value.

However, the method of detecting galling is not limited to this. For example, a force sensor may be installed on the end effector 20E, and the galling detection unit 13 may be configured to obtain information from the force sensor indicating the magnitude of the contact pressure that the target object W receives from the attached object, and detect galling if the contact pressure obtained based on this exceeds a predetermined threshold. The galling detection unit may also be configured to detect galling based on position information of the robot arm 20, for example, based on the difference between a command value and an actual value.

"Scuffing" refers to adhesion that occurs locally. It occurs when two parts come into contact and a protrusion (real contact point) formed on the surface of one part adheres to the other part due to contact with the other part. Between materials that are prone to adhesion, galling can occur even at room temperature. Galling can occur due to variations in the shape precision of the object W or the assembled part, differences in surface roughness or surface shape, uneven contact caused by these, poor lubrication, the inclusion of foreign matter, etc. Galling is also called biting, catching, etc.

"Scaling" refers not only to the actual occurrence of galling, but also to the state immediately preceding the occurrence of galling. For example, it includes a state in which galling has not actually occurred, but the contact pressure between two components exceeds a threshold value and galling will occur if left unchecked.

The error processing unit 14 counts the number of times that the galling detection unit 13 detects galling, and executes a predetermined error process if galling is detected a predetermined number of times or more. The predetermined number of times may be set arbitrarily. The predetermined error process may include, for example, stopping the assembly control, or may include control to return the target object W being assembly controlled to a predetermined starting position.

The temporary placement control execution unit 15 executes temporary placement control to place the object W grasped by the robot arm 20 in a temporary placement site. For example, the temporary placement control execution unit 15 executes a tracing operation in which the robot arm 20 contacts the temporary placement site and traces it by elastically deforming the series elastic actuator 40 of the robot arm 20 in the temporary placement control. Here, the tracing operation in the temporary placement control means moving the object W relatively to a temporary placement position described later while bringing the object W into contact with a contacted portion of the temporary placement site described later. Here, the relative movement is not limited to translational movement, but includes rotating the object W relatively to a predetermined temporary placement position. The temporary placement control execution unit 15 is configured to elastically deform the elastic body 44 of the series elastic actuator 40 so that the contact pressure detected by the sensor 46 is substantially constant or within a predetermined range. This makes it possible to perform assembly work while suppressing damage such as galling to the object W or the predetermined temporary placement site.

Regarding the hardware configuration, the control device 10 can be configured from a computer equipped with 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 non-volatile 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 that connects these. The non-volatile memory element stores, for example, a computer program for executing each process shown in this embodiment. The volatile memory element temporarily stores at least a part of these computer programs and the results of the calculation process. However, at least a part of these calculation elements, non-volatile memory elements, etc. may be installed in a remote location connected to a communication network such as the Internet. For example, the calculation element may be configured to acquire the computer program or necessary data via the communication network.

The control device 10, the robot arm 20, the display device 60, and the input device 62 are each 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 how to operate may be connected to the control device 10. The display device 60 and the input device 62 may be a computer equipped with a display unit and an input unit, or may be configured as an integrated unit such as a touch panel.

Next, the configuration of the temporary storage area will be described with reference to Figure 4. Figure 4 is a plan view of the temporary storage area R2 provided on stage M2.

The temporary storage area R2 is configured as a recess provided on the stage M2, for example, having a substantially trapezoidal bottom surface substantially parallel to the XY plane. Here, the configuration of the stage M2 is not particularly limited as long as the temporary storage area can be formed, but it may be configured of any material such as metal or resin. A temporary storage position P whose dimensions in the XY plane are substantially the same as the dimensions of the target object W is provided on the negative X-axis side of the temporary storage area R2. In addition, the inner circumferential surface of the recess constituting the temporary storage area R2 that extends in the Z-axis direction on the negative X-axis side constitutes the alignment portion T. The curvature of the alignment portion T is set to be the same as the curvature of at least a part of the side surface of the target object W. As a result, when the target object W is placed at the temporary storage position P, the target object W is placed along at least a part or all of the alignment portion T. Note that at this time, the target object W may contact at least a part or all of the alignment portion T.

The temporary storage site R2 is provided with contacted parts S1, S2, and S3 for contacting the object W in temporary placement control. The contacted part S1 is configured to include a part of the bottom surface of the recess constituting the temporary storage site R2 that is adjacent to the temporary placement position P. The contacted part S1 has the same height in the Z-axis direction as the temporary placement position P. The contacted parts S2 and S3 are provided on the inner peripheral surface extending in the Z-axis direction adjacent to the alignment part T of the recess constituting the temporary storage site R2. These contacted parts S1 to S3 have the function of guiding the object W grasped by the robot arm 20 toward the temporary placement position P in temporary placement control. That is, in temporary placement control, the object W grasped by the robot arm 20 moves to the temporary placement position P while remaining in contact with the contacted parts S1, S2, and/or S3. In addition, the position and configuration of the contacted parts are not limited to these contacted parts S1 to S3, and can be arbitrarily configured to match the dimensions and shape of the temporary storage area or temporary storage position, as long as it is possible to perform a tracing operation of the target object W.

In the temporary placement control, the temporary placement control execution unit 15 may bring the object W grasped by the robot arm 20 into contact with an arbitrary position included in the contacted portion S1, and then translate the object W toward the temporary placement position P while keeping it in contact with the contacted portion S1 (while sliding on the contacted portion S1). In addition, in the temporary placement control, the temporary placement control execution unit 15 may bring the object W grasped by the robot arm 20 into contact with an arbitrary position included in the contacted portion S2, and then translate the object W toward the temporary placement position P while keeping it in contact with the contacted portion S2 (while sliding on the contacted portion S2). In addition, in the temporary placement control, the temporary placement control execution unit 15 may bring the object W grasped by the robot arm 20 into contact with an arbitrary position included in the contacted portion S3, and then translate the object W toward the temporary placement position P while keeping it in contact with the contacted portion S3 (while sliding on the contacted portion S3).

Next, the tracing operation in the temporary placement control executed by the robot arm 20 will be described with reference to Figures 5 and 6. As described above, the tracing operation can be executed by the assembly control execution unit 12 during the assembly control, and can be executed by the temporary placement control execution unit 15 during the temporary placement control. Below, as an example, the tracing operation in the temporary placement control in which the target object W is temporarily placed in the temporary placement area R2 will be described.

Figure 5 is a diagram that shows a schematic diagram of a tracing operation by the robot arm 20. As an example of a tracing operation, the figure shows a tracing operation in which the target object W grasped by the robot arm 20 is translated on the contacted portion S1 toward the temporary placement position P.

In FIG. 5, the end effector 20E and the object W grasped by it when the reference position is at the target position are shown by dashed lines, and the actual end effector 20E and the object W grasped by it when the reference position is away from the target position are shown by solid lines. As shown by the dashed lines, at the target position, the object W grasped by the end effector 20E interferes with the contacted portion S1 of the temporary storage area R2. However, in reality, due to the existence of the temporary storage area R2, the contact portion W1 of the object W comes into contact with the contacted portion S1 of the temporary storage area R2.

Here, the contact portion W1 may be, for example, a part of the boundary between the bottom surface and the side surface of the approximately cylindrical shape. The displacement amount 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 object W to the contacted portion S1 of the temporary storage site R2. Then, after the contact portion W1 of the object W contacts the contacted portion S1 of the temporary storage site R2, the robot arm 20 translates the object W in the direction indicated by the arrow in FIG. 6 toward the temporary storage position P while maintaining the state in which the contact portion W1 contacts the contacted portion S1. The robot arm 20 executes the translational movement of the object W, for example, until the object W contacts the alignment portion T. At this time, the robot arm 20 may translate the object W to the temporary storage position P while still keeping it in contact with the contacted portion S2 or S3.

Figure 6 is a diagram showing a schematic diagram of another aspect of the tracing operation by the robot arm 20. As an example of the tracing operation, the figure shows a tracing operation in which the object W grasped by the robot arm 20 is rotated relative to the temporary placement position P. The tracing operation is performed, for example, as described with reference to Figure 5, after the object W grasped by the robot arm 20 reaches the temporary placement position P provided in the temporary placement area R2.

In FIG. 6, the end effector 20E and the object W held by it at the target position are shown by dashed lines, and the actual end effector 20E and the object W held by it are shown by solid lines. As shown by the dashed lines, the object W held by the end effector 20E at the target position interferes with the alignment part T of the temporary storage site R2. However, in reality, due to the existence of the temporary storage site R2, the contact part W2 of the object W comes into contact with the alignment part T of the temporary storage site R2.

Here, the contact portion W2 may be, for example, a part of the boundary between the bottom surface and the side surface of the approximately cylindrical shape. The displacement amount 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 amount and the spring constant acts from the object W to the temporary storage site R2. The robot arm 20 rotates the object W so that the contact portion W1 of the object W contacts the temporary storage position P of the temporary storage site R2 and the contact portion W2 of the object W contacts the alignment portion T of the temporary storage site R2, and slides the contact portion W1 along the temporary storage position P in the negative direction of the X axis and slides the contact portion W2 along the alignment portion T in the positive direction of the Z axis. The rotational movement is performed until the bottom surface of the object W contacts the temporary storage position P. When the rotational movement is completed, the object W is placed at the temporary storage position P, and the side surface of the object W contacts the alignment portion T.

Next, referring to FIG. 7, the operation method of the robot arm 20 according to this embodiment will be described. FIG. 7 is a diagram showing an example of a basic operation flow of the robot arm 20 according to this embodiment. In this basic operation flow, if galling is detected during the assembly control of the object W to the assembly portion R1, a temporary placement control is executed under a predetermined condition to place the object W in the temporary placement area R2. Then, after the temporary placement control, the assembly control is started again. If galling is detected during the assembly control, the assembly control may be called the "first assembly control", and the assembly control that is started again after the temporary placement control may be called the "second assembly control". Note that the "first assembly control" and the "second assembly control" are merely names that relatively indicate the chronological order of these assembly controls. In other words, if galling is detected again after assembly control has been started via temporary placement control, the assembly control being executed when the galling was detected becomes the "first assembly control," and the assembly control that is started via temporary placement control after the galling is detected becomes the "second assembly control."

First, the assembly control execution unit 12 starts the assembly control of the object W by the robot arm 20 (S10). Specifically, in response to the control by the assembly control execution unit 12, the end effector 20E of the robot arm 20 grasps the object W placed at a predetermined starting position by pinching the top and side surfaces of the object W, and then moves the object W to the assembly site R1 provided on the mold M1, and starts the assembly control of the object W to the assembly site R1. In the case of assembly control executed after the temporary placement control in step S15 described later, the end effector 20E of the robot arm 20 grasps the object W placed in the temporary placement site R2.

When assembly control is started, the galling detection unit 13 determines whether galling has been detected (S11). If the galling detection unit 13 determines that galling has not been detected (S11; No), it determines whether assembly control has ended. If it determines that assembly control has ended (S12; Yes), the process ends. On the other hand, if it determines that assembly control has not ended (S12; No), the process returns to step S11 again. In this way, the galling detection unit 13 determines whether galling has been detected while assembly control is being executed.

When the galling detection unit 13 detects galling (S11; Yes), the error processing unit 14 determines whether the number of galling detections is equal to or greater than a predetermined number (S13). When it is determined that the number of galling detections is equal to or greater than the predetermined number (S13; Yes), the error processing unit 14 executes a predetermined error process (S14). For example, the error processing unit 14 executes control to stop the assembly control as the predetermined error process. The error processing unit 14 may also execute control to return the target object W in the middle of the assembly control to a predetermined starting position.

If it is determined that the number of times that galling has been detected is not equal to or greater than the predetermined number (S13; No), the temporary placement control execution unit 15 executes temporary placement control to place the object W grasped by the robot arm 20 in the temporary placement area R2 (S15). Details of the temporary placement control will be described later. When the object W is placed in the temporary placement area R2 by the temporary placement control, the process returns to step S10, and the assembly control execution unit 12 starts assembly control again. In this way, the start position of the assembly control executed after the temporary placement control may be set based on the position of the alignment unit T.

After assembly control is started again, the above process is repeated until assembly control ends (S12; Yes) or the number of times that galling is detected exceeds a predetermined number and error processing is executed (S13; Yes, S14).

Next, the temporary placement control of the robot arm 20 according to this embodiment will be described with reference to Figs. 8 and 9. This temporary placement control corresponds to the temporary placement control by the temporary placement control execution unit 15 in step S15 described above. Fig. 8 is a diagram showing an example of an operation flow of the temporary placement control of the robot arm 20 according to this embodiment. Fig. 9 is a diagram showing a schematic view of the temporary placement control of the robot arm 20 according to this embodiment.

First, as shown in FIG. 9(a), the robot arm 20 moves the target object W to a temporary storage area R2 provided on the stage M2 (S20). Specifically, the robot arm 20 moves the target object W from the assembly site R1 provided on the mold M1 to within a predetermined area above the contacted portion S1 of the temporary storage area R2.

9(b), the robot arm 20 then lowers the grasped object W to bring the contact portion W1 of the object W into contact with the contacted portion S1 (S21). Here, the contact portion W1 is not particularly limited as long as it is a part of the object W, but may be, for example, a part of the boundary between the bottom surface and the side surface of the approximately cylindrical shape.

9(c), the robot arm 20 translates the object W in the negative direction of the X-axis while keeping the contact portion W1 of the object W in contact with the contacted portion S1 with a predetermined contact pressure (S22). As a result, the object W slides on the contacted portion S1 toward the temporary placement position P while keeping the contact portion W1 in contact with the contacted portion S1. Note that at this time, the robot arm 20 may bring any contact portion of the object W into contact with the contacted portion S2 or S3 of the temporary placement site R2 described with reference to FIG. 4, and then move the object W in the negative direction of the X-axis while maintaining the contact state. As a result, the object W that has come into contact with the contacted portion S2 or S3 slides toward the temporary placement position P while being guided by the contacted portion S2 or S3 in the Y-axis direction.

Eventually, as shown in FIG. 9(d), the contact portion W2 of the target object W comes into contact with the alignment portion T provided in the temporary storage area R2. Here, the contact portion W2 is not particularly limited as long as it is a part of the target object W, but may be, for example, a part of the boundary between the top surface and the side surface of the approximately cylindrical shape.

Next, as shown in FIG. 9(e), while the contact portion W1 of the object W is in contact with the temporary placement position P of the temporary placement site R2 and the contact portion W2 of the object W is in contact with the alignment portion T of the temporary placement site R2, the robot arm 20 rotates and moves the object W so that the contact portion W1 slides along the temporary placement position P in the negative direction of the X-axis and the contact portion W2 slides along the alignment portion T in the positive direction of the Z-axis (S23). This rotational movement is performed until the bottom surface of the object W contacts the temporary placement position P. When the rotational movement is completed, the object W is placed at the temporary placement position P and the side of the object W contacts the alignment portion T. This ends the temporary placement control.

Next, the configuration of the temporary storage area R2' according to the modified example will be described with reference to FIG. 10. FIG. 10 is a plan view of the temporary storage area R2' provided on the stage M2.

The temporary placement site R2' is configured as a generally cylindrical recess provided on the stage M2, the dimensions of which are slightly larger than the dimensions of the assembly site R1 provided on the mold M1. In temporary placement control, for example, the target object W may be fitted into the temporary placement site R2'. A temporary placement position P' is provided within the recess of the temporary placement site R2'. The inner circumferential surface of the recess constituting the temporary placement site R2', which extends in the Z-axis direction, constitutes the alignment portion T'. As described above, since the dimensions of the temporary placement site R2' are slightly larger than the dimensions of the assembly site R1, even if galling occurs at the assembly site R1 during assembly control, the possibility of galling occurring in the temporary placement control is reduced.

When the object W is placed at the temporary placement position P', the object W is placed along at least a part or all of the alignment portion T'. At this time, the object W may come into contact with at least a part or all of the alignment portion T'. The assembly control by the assembly control execution unit 12 can, for example, set the position of the object W placed at the temporary placement position P' as the starting position.

Around the recess constituting the temporary storage area R2', a contacted portion S4, which is a surface extending in the XY direction, is provided. The position where the contacted portion S4 is provided is not particularly limited as long as it is around the temporary storage position P'. In the temporary storage control, the temporary storage control execution unit 15 may bring the object W grasped by the robot arm 20 into contact with any position included in the contacted portion S4, and then translate the object W toward the temporary storage position P' while keeping it in contact with the contacted portion S4 (while sliding on the contacted portion S4). In addition, in the temporary storage control, the temporary storage control execution unit 15 may bring the object W grasped by the robot arm 20 into contact with a corner of the temporary storage area R2' (the boundary between the upper surface and the side surface of the approximately cylindrical shape of the recess constituting the temporary storage area R2'), and then rotate the object W toward the temporary storage position P' while keeping it in contact with the corner.

Next, the temporary placement control of the robot arm 20 according to the modified example will be described with reference to Figs. 11 and 12. This temporary placement control corresponds to the temporary placement control by the temporary placement control execution unit 15 in step S15 described with reference to Fig. 7. Fig. 11 is a diagram showing an example of the operation flow of the temporary placement control of the robot arm 20 according to the modified example. Fig. 12 is a diagram showing a schematic view of the aspect of the temporary placement control of the robot arm 20 according to the modified example.

First, as shown in FIG. 12(a), the robot arm 20 moves the target object W to a temporary storage area R2' provided on the stage M2 (S30). Specifically, the robot arm 20 moves the target object W from the assembly site R1 provided on the mold M1 to within a predetermined area above the temporary storage area R2' provided on the stage M2.

12(b), the robot arm 20 lowers the grasped object W to bring the contact portion W1 of the object W into contact with the contacted portion S4 (S31). Here, the contact portion W1 is not particularly limited as long as it is a part of the object W, but may be, for example, a part of the boundary between the bottom surface and the side surface of the approximately cylindrical shape.

12(c), the robot arm 20 translates the object W toward the temporary placement position P' while keeping the contact portion W1 of the object W in contact with the contacted portion S4 with a predetermined contact pressure (S32). As a result, the object W slides on the contacted portion S4 toward the temporary placement position P' while keeping the contact portion W1 in contact with the contacted portion S4.

As shown in FIG. 12(d), the contact portion W1 of the object W enters the interior of the temporary storage area R2', and the contact portion W3 of the object W slides on the corner T1 of the temporary storage area R2' (the boundary between the top surface and the side surface of the approximately cylindrical shape of the recess that constitutes the temporary storage area R2'). Here, the contact portion W3 is not particularly limited as long as it is a part of the object W, but may be, for example, a part of the side surface of the approximately cylindrical shape.

Next, as shown in FIG. 12(e), the robot arm 20 rotates the object W in the direction of the arrow while the contact portion W3 of the object W remains in contact with the corner portion T1 of the temporary storage area R2' (S33). This rotational movement is performed until the object W fits into the upper portion of the temporary storage area R2'.

Next, as shown in FIG. 12(f), the robot arm 20 applies lateral pressure from above to the object W, inserting the object W into the temporary placement area R2' (S34). When the object W comes into contact with the bottom surface of the temporary placement area R2', the lateral pressure ends, and the object W is placed in a fitted state within the temporary placement position P'. At this time, the side of the object W comes into contact with the alignment part T. This ends the temporary placement control.

As described above, the operating method of a robot arm according to one embodiment of the present invention includes, when galling is detected during a first assembly control of an object grasped by a robot arm having a flexible drive mechanism, placing the object in a temporary storage area by a tracing operation, grasping the object placed in the temporary storage area by the robot arm, and starting a second assembly control of the object.

According to this, when a robot arm having a flexible drive mechanism is used and galling is detected during the first assembly control of an object grasped by the robot arm, the object is placed in a temporary storage area, thereby reducing the possibility of damage to the object or the assembly part. In addition, since the object is placed in the temporary storage area by a tracing motion, the placement control can be performed with high accuracy.

In the above aspect, placing the object in the temporary storage area by a tracing motion may include bringing the object into contact with a predetermined contacted portion, and tracing the object toward a predetermined temporary storage position while keeping the object in contact with the contacted portion.

In the above embodiment, the predetermined temporary placement position may be a position where the object comes into contact with a predetermined alignment portion.

In the above aspect, the start position of the second assembly control may be set based on the position of a predetermined alignment portion.

In the above embodiment, the dimensions of the temporary storage area may be set to be larger than the dimensions of the assembly portion provided on the object to be assembled.

In the above embodiment, the drive mechanism may include a series elastic actuator.

In the above aspect, the tracking operation may include causing the target object to track the temporary storage site while elastically deforming the elastic body of the series elastic actuator.

In the above embodiment, the elastic body of the series elastic actuator may be composed of a leaf spring.

In the above aspect, the drive mechanism may include at least one of a magnetic liquid, a mechanical spring, an air spring, a magnetic spring, and a vane motor to provide flexibility.

In the above aspect, the operating method may further include executing a predetermined error process if galling is detected a predetermined number of times or more.

A robot system according to one embodiment of the present invention includes a robot arm having a flexible drive mechanism, and a control device for controlling the robot arm, which executes the steps of placing the object in a temporary storage area by a matching operation when galling is detected during a first assembly control of an object grasped by the robot arm, grasping the object placed in the temporary storage area by the robot arm, and starting a second assembly control of the object.

The control device according to one embodiment of the present invention is configured to execute the steps of placing the object in a temporary storage area by a matching operation, grasping the object placed in the temporary storage area by the robot arm, and starting a second assembly control of the object when galling is detected during a first assembly control of an object grasped by a robot arm having a flexible drive mechanism.

A program according to one embodiment of the present invention causes a computer to generate control instructions for executing the steps of placing the object in a temporary storage area by a matching operation, grasping the object placed in the temporary storage area by the robot arm, and starting a second assembly control of the object when galling is detected during a first assembly control of an object grasped by a robot arm having a flexible drive mechanism.

The present invention is not limited to the above-described embodiment, but can be modified and applied in various ways. Any of the aspects described in the above-described embodiment and modified examples can be applied in combination with other aspects to the extent that it is not inconsistent with the understanding of a person skilled in the art.

In the above embodiment, the object W is fitted into the mounting portion R1 of the mold M1. However, the present invention can be applied to various other applications, such as gripping a flange (an example of an "object") in which a through hole is formed, and assembling the flange to a shaft by aligning the wall surface of the through hole with the surface of the shaft (an example of an "object to be assembled") so that the shaft passes through the through hole, gripping 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 aligning the wall surface of a rod-shaped inspection tool (an example of an object to be assembled) with the surface of the inspection tool so that the tool passes through the through hole, and assembling an optical component such as a lens module (an example of an "object") to a precision device (an example of an object to be assembled).

In addition to the series elastic actuator, various other driving mechanisms can be used as driving mechanisms with flexibility. Here, "having flexibility" means having elasticity, viscosity, or elasticity and viscosity. Elasticity refers to the property of being deformed when stress is applied and returning to the original shape when the stress is removed, and is sometimes expressed as the term flexibility, which indicates the ease of elastic deformation. Viscosity refers to the property of generating stress that makes the flow speed of a fluid uniform. In order to impart viscosity and elasticity, magnetic fluids, mechanical springs (leaf springs, torsion coil springs), air springs, magnetic springs, vane motors, variable dampers using electro-viscous fluids whose viscosity can be adjusted according to the applied voltage, etc. may be used.

The implementation modes described through the above embodiments of the invention can be used in appropriate combinations or with modifications or improvements depending on the application, and the present invention is not limited to the above-mentioned embodiments. It is clear from the claims that such combinations or forms with modifications or improvements can also be included in the technical scope of the present invention.

10...Control device, 11...Control command acquisition unit, 12...Assembly control execution unit, 13...Cross-section detection unit, 14...Error processing unit, 15...Temporary placement control execution unit, 20...Robot arm, 20E...End effector, 20E1...Moving plate, 20E2...Moving plate, 20J...Joint, 20L...Link, 30...Drive unit, 40...Series elastic actuator, 42...Drive unit, 44...Elastic body, 46...Sensor, 60...Display unit, 62...Input device, 100...Robot system,

Claims (12)

An operating method for assembling an object to a workpiece using a robot arm having a flexible drive mechanism, comprising:
When galling is detected during a first assembly control of the object gripped by the robot arm, the object is arranged so that the object comes into contact with a positioning portion of a temporary storage site by a tracing operation;
Grasping the object placed in the temporary storage area with the robot arm;
Starting a second assembly control of the object;
A method of executing the above. The placing of the object in the temporary storage site by a tracing operation includes:
Bringing the object into contact with a predetermined contact portion;
The method of claim 1 , further comprising: moving the object toward the alignment portion while contacting the contacted portion. The method according to claim 2 , wherein a start position of the second assembly control is set based on a position of the alignment unit. The operating method according to any one of claims 1 to 3, wherein the dimensions of the temporary storage area are set to be larger than the dimensions of the assembly portion provided on the object to be assembled. The method of any one of claims 1 to 4, wherein the drive mechanism comprises a series elastic actuator. The operating method according to claim 5, wherein the tracking operation includes causing the target object to track the temporary storage area while elastically deforming the elastic body of the series elastic actuator. The method of claim 6, wherein the elastic body of the series elastic actuator is composed of a leaf spring. The method of any one of claims 1 to 7, wherein the drive mechanism includes at least one of a magnetic liquid, a mechanical spring, an air spring, a magnetic spring, and a vane motor to provide the flexibility. The operating method according to any one of claims 1 to 8, further comprising: executing a predetermined error process if the galling is detected a predetermined number of times or more. A robot arm having a flexible drive mechanism;
A control device for controlling the robot arm,
When galling is detected during a first assembly control of the object gripped by the robot arm, the object is arranged so that the object contacts an alignment portion of a temporary placement site by a tracing operation;
A step of grasping the object placed in the temporary storage area by the robot arm;
starting a second assembly control of the object;
A control device for executing the above-mentioned
A robot system comprising: A control device for controlling a robot arm having a flexible drive mechanism,
When galling is detected during a first assembly control of the object gripped by the robot arm, the object is arranged so that the object contacts an alignment portion of a temporary placement site by a tracing operation;
A step of grasping the object placed in the temporary storage area by the robot arm;
starting a second assembly control of the object;
A control device configured to be able to execute the above. On the computer,
a step of positioning the object so that the object contacts an alignment portion of a temporary placement site by a tracing operation when galling is detected during a first assembly control of the object gripped by the robot arm having a flexible drive mechanism;
A step of grasping the object placed in the temporary storage area by the robot arm;
starting a second assembly control of the object;
generating control instructions for executing the
Computer program.

Images