JP5024689B2 - Assembly robot and its control method - Google Patents

Description

  The present invention relates to an assembly robot for assembling a workpiece on an object via an intermediate member and a control method therefor.

“Force control” is a technique that measures the force and moment applied to the work from the force sensor attached to the hand of the robot or the torque of the robot joint, and changes the position and speed of the hand according to this.
Force control is used, for example, for fitting work of precision parts. Adjustment parameters in force control are a virtual spring, a virtual damper, a virtual mass, and the like.

  For example, Patent Documents 1 to 6 disclose that force control is used when a workpiece is assembled to an object by a robot.

Japanese Patent Application Laid-Open No. H10-228561 detects failure from the force applied during work.
In Patent Document 2, an in-process component that has failed in work is recognized by an image sensor and removed to continue operation without stopping operation.
Patent Document 3 re-plans the work procedure after the failure based on the recognition result of the position / posture of the part using the image sensor.

Patent Document 4 stores correspondence of articles used in a plurality of processes, and executes automatic processing in association with articles in each process.
Patent Document 5 optimizes the gripping force to prevent breakage and deformation even when a member is weak in strength by internal force management control, and is assembled to another member.
In Patent Document 6, after controlling the position of each actuator so that the origin of the workpiece coordinate moves to the target coarse position, the workpiece is positioned in the rolling, pitching and yawing directions based on the work coordinate system. The work is assembled while controlling the force.

Japanese Patent No. 3366248, “Robot Control Method and Device” JP 2009-782 A, “Robot Control System and Robot Hand” Japanese Patent Application Laid-Open No. 7-152420, “Assembly device by robot” Japanese Patent No. 2547899, “Control Method and Control Device for Automatic Device” JP 2009-279678 A, “Automatic assembly apparatus, automatic assembly method, and display apparatus” Japanese Patent Application Laid-Open No. 9-128023, “Work Assembly Method and Apparatus”

  Patent Document 3 proposes a means of trying the work itself again after a failure, but Patent Document 1 and Patent Document 2 other than that do not disclose anything about retry after the failure.

In the means of Patent Document 3, the target state of each part, the position and orientation of the part at a predetermined point in time during assembly, and the work procedure are all identified and stored, so that the work procedure is re-planned and assembled. You can continue working.
However, this means has a lot of information to prepare in advance and is complicated. In particular, in assembly work that requires precise force control, it is necessary to judge all differences in minute situations as separate events, and to accurately determine the state and position of minute parts that affect the work. Requires an image sensor capable of high-resolution and high-precision measurement and image recognition processing.

  The present invention has been developed to solve the above-described problems. That is, an object of the present invention is to execute an assembly operation for assembling a workpiece on an object via an intermediate member without performing image recognition processing using an image sensor, and determine whether the assembly operation is successful or unsuccessful. It is an object to provide an assembly robot capable of determining a fitting state between a workpiece and an intermediate member when an assembly operation is unsuccessful, and a control method therefor.

According to the present invention, a robot hand having a force sensor for measuring an external force and gripping a workpiece;
A robot arm capable of moving the position and posture of the robot hand in a three-dimensional space;
A robot control device that controls the robot arm and executes an assembly operation for assembling the workpiece onto an object via an intermediate member;
The robot controller determines the success or failure of the assembly work from the position of the workpiece during the assembly work and the measured external force,
When the assembly operation is unsuccessful, the workpiece is returned to the position before the assembly operation,
Next, for the fixing member to which the intermediate member cannot be fitted, the fixing member is virtually regarded as the object, and the assembly operation is performed again.
An assembly robot is provided, wherein a fitting state between the workpiece and the intermediate member is determined from the position of the workpiece being re-executed and the measured external force.

According to the present invention, a robot hand having a force sensor for measuring an external force and gripping a workpiece;
A robot arm capable of moving the position and posture of the robot hand in a three-dimensional space;
(A) controlling the robot arm, and performing an assembly operation for assembling the workpiece onto an object via an intermediate member;
(B) determining the success or failure of the assembly operation from the position of the workpiece during the assembly operation and the measured external force;
(C) When the assembly work is unsuccessful, the work is returned to the position before the assembly work,
(D) Next, for the fixing member to which the intermediate member cannot be fitted, the fixing member is virtually regarded as the object, and the assembly operation is re-executed.
(E) Provided is a method for controlling an assembly robot, wherein a fitting state between the workpiece and the intermediate member is determined from the position of the workpiece being re-executed and the measured external force.

According to the above-described apparatus and method of the present invention, the assembly of assembling the workpiece onto the object through the intermediate member pre-fitted to the workpiece or the object by the robot hand having the force sensor, the robot arm, and the robot controller. Work can be performed.
Further, the success or failure of the assembling work can be determined from the position of the workpiece during the assembling work and the measured external force.

  Further, when the assembly work is unsuccessful, that is, when an abnormality is detected, the work gripped by the robot hand is returned to the position before the assembly work, and the assembly work is performed by force control on the fixed member where the intermediate member cannot be fitted in another place. By re-executing, it is possible to determine the fitting state of the intermediate member, that is, the presence or absence of the intermediate member that can be detached from the workpiece, from the position of the workpiece being re-executed and the measured external force.

  Further, during the assembling operation, if the intermediate member is correctly fitted to the workpiece, the intermediate member has returned to the ideal position (regular position) again, so that the assembling operation can be retried as it is. Further, if the intermediate member is not properly fitted to the workpiece, the intermediate member cannot be returned to the ideal position (regular position). Therefore, it is determined that it is difficult to continue the assembly work using the workpiece, and the intermediate member Assembling work can be performed using a new work that is correctly fitted.

Therefore, by this determination, (1) detection of presence / absence of intermediate member at the time of assembly failure, (2) check of soundness of intermediate member and its soundness, (3) determination of use of new parts at failure of sounding of intermediate member The effect which can perform operation | movement, (4) prevention of operation stop of an apparatus, etc. is acquired.

It is an embodiment figure of the assembly robot by this invention. It is a figure which shows the example of the assembly | attachment object article. It is a flowchart of the control method by this invention. It is a figure which shows the state by which the workpiece | work was assembled normally. It is a figure which shows the state which detected the abnormality during the assembly and stopped. It is explanatory drawing of the operation | movement which makes the intermediate member which has come off from the workpiece | work fitted to a workpiece | work by the fixing member which an intermediate member cannot fit. It is explanatory drawing of the operation | movement which detects that the intermediate member has remove | deviated from the workpiece | work using a fixing member. It is a figure which shows the relationship between the relative position of a workpiece | work and a fixing member, and the fitting state of a workpiece | work and an intermediate member.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

FIG. 1 is an embodiment diagram of an assembly robot according to the present invention.
In this figure, an assembly robot 10 is an automatic device for assembling a workpiece 1 to an object 2 via an intermediate member 3, and includes a robot hand 12, a robot arm 16, and a robot control device 20.

In this example, the intermediate member 3 is fitted to the workpiece 1 in advance, and the workpiece 1 is assembled to the object 2 by fitting the intermediate member 3 to the object 2.
In addition, this invention is not limited to this, The intermediate member 3 may be previously fitted to the target object 2, the intermediate member 3 may be fitted to the workpiece | work 1, and the workpiece | work 1 may be assembled | attached to the target object 2. FIG.
Hereinafter, the case where the intermediate member 3 is previously fitted to the workpiece 1 will be described.

  In the embodiment described later, the intermediate member 3 is a cylindrical member, and the workpiece 1 is fitted to the upper end thereof, and the robot hand 12 grips the workpiece 1.

  The robot hand 12 has a force sensor 14 that measures an external force, and grips the workpiece 1.

The force sensor 14 is a sensor that detects an external force acting on the workpiece 1.
In this example, the force sensor 14 is a six-axis sensor capable of measuring a force (Fx, Fy, Fz) in three orthogonal axes and a torque (Tx, Ty, Tz) around each axis, and can be moved three-dimensionally. 6 degrees of freedom external force (forces Fx, Fy, Fz in three directions and torques Tx, Ty, Tz around three axes) acting on the robot arm 16 is detected.
In addition, this invention is not limited to this, As long as the external force which acts on the workpiece | work 1 is detectable, another force sensor may be sufficient.

The robot arm 16 is configured such that the robot hand 12 is attached to the hand, and the position and posture of the robot arm 16 can be moved in a three-dimensional space.
In this example, the robot arm 16 is a robot arm of an articulated robot, but the present invention is not limited to this and may be another robot.

The robot control device 20 stores the operation conditions of the workpiece 1 in each operation in the storage device 21 and controls the robot arm 16.
The robot control device 20 is, for example, a numerical control device, and controls the robot arm 16 to six degrees of freedom (three-dimensional position and rotation about three axes) by a command signal.

The operation condition of the work 1 in each operation stored in the storage device 21 includes a precondition, a success condition, and a failure condition.
The storage device 21 stores operation conditions and control methods corresponding to the respective operations.
The control method is position control, speed control, or force control, and the force control is impedance control or damping control, but the present invention is not limited to this, and other force control methods may be used.

  The storage device 21 further stores a trajectory data table for each operation. The trajectory data table includes TCP target positions (X, Y, Z) of the robot hand 12 and pressing direction vectors.

FIG. 2 is a diagram illustrating an example of an assembly target article targeted by the present invention.
The present invention is directed to an assembly operation in which the workpiece 1 is assembled to the object 2 via the intermediate member 3.
In FIG. 2A, the intermediate member 3 is a cylindrical member, the workpiece 1 has a hole 1a that fits into the upper part of the intermediate member 3 on the lower surface thereof, and the object 2 has a lower part of the intermediate member 3 on the upper part thereof. And a hole 2a to be fitted.
In FIG. 2 (B), the intermediate member 3 is a cylindrical member having a flange 3a, the workpiece 1 has a hole 1a fitted to the upper part of the intermediate member 3 on the lower surface, and the object 2 is intermediate in the upper part. It has a hole 2 a that fits into the lower part of the member 3.

In the example of FIG. 2A, the upper end of the hole 1a is closed, and the position where the upper surface of the intermediate member 3 is in contact with the upper surface of the hole 1a is the normal initial position.
In the example of FIG. 2B, the hole 1a passes through, and the position where the upper surface of the flange 3a contacts the lower surface of the workpiece 1 is the normal initial position.

  Other structures are the same in FIGS. 2A and 2B. Hereinafter, the case where the assembly target article is shown in FIG.

The hole 1a of the workpiece 1 is a cylindrical hole, and its inner diameter is slightly larger than the diameter of the intermediate member 3, so that it can be inserted while maintaining concentricity until the upper part of the intermediate member 3 reaches the initial position described above. It has become.
The difference between the inner diameter of the cylindrical hole 1a and the diameter of the intermediate member 3 is, for example, 0.01 mm.

In FIG. 2A, the object 2 is fixed so as not to move to the work table 4 (see FIG. 1).
The hole 2a of the object 2 is a cylindrical hole, the inner diameter thereof is slightly larger than the diameter of the intermediate member 3, and the concentricity is maintained until the lower part of the intermediate member 3 reaches a predetermined position of the cylindrical hole 2a. It can be inserted.
The difference between the inner diameter of the cylindrical hole 2a and the diameter of the intermediate member 3 is, for example, 0.01 mm.

The robot control device 20 controls the robot arm 16 and executes an assembly operation for fitting the intermediate member 3 fitted to the workpiece 1 to the object 2.
This assembly work includes, for example, the following three operations (1) to (3).
Operation (1) is a proximity operation until the lower end of the intermediate member 3 is inserted into the upper portion of the cylindrical hole 2a. In this operation, it is necessary to determine whether or not the insertion is successful.
The operation (2) is an operation immediately after the start of fitting. In this operation, it is necessary to correct the displacement of the position and posture of the workpiece 1 so that the cylindrical holes 1a and 2a coincide.
Operation (3) is an insertion operation during fitting. In this operation, it is necessary to insert the intermediate member 3 while correcting the displacement of the position of the workpiece 1 so that the cylindrical holes 1a and 2a coincide.
Therefore, in the operations (2) and (3), the workpiece 1 is moved toward the target object 2 along the axis of the cylindrical hole 2a of the target object 2.

  FIG. 3 is a flowchart of the control method according to the present invention. In this figure, the method of the present invention comprises the steps S1 to S8.

In step S <b> 1 (work gripping step), the robot hand 12 grips the work 1 (work 1 with the intermediate member 3) in which the intermediate member 3 is fitted at the normal initial position described above.
In step S2 (assembly step), the robot arm 16 is controlled, and an assembly operation for fitting the intermediate member 3 fitted to the workpiece 1 to the object 2 is executed.

In step S3 (assembly determination step), the success or failure of the assembly work is determined from the position of the workpiece 1 during the assembly work and the measured external force.
For example, in the above-described three operations (1) to (3), if the external force detected by the force sensor 14 in each operation range exceeds a preset threshold value, it is determined as a failure, and if the external force is equal to or less than the threshold value, the operation is successful. Judge.
If it is successful (Yes) in step S3, the assembly work is terminated.

FIG. 4 is a diagram illustrating a state in which the workpiece is normally assembled by the three operations (1) to (3).
In this example, the portion of the intermediate member 3 that protrudes downward from the work 1 while the upper surface of the intermediate member 3 is in contact with the upper surface of the hole 1a (the lower portion from the intermediate portion) is the object 2. It is inserted into the cylindrical hole 2a while maintaining concentricity.
Therefore, the workpiece 1 can be positioned on the object 2 via the intermediate member 3 in this state.
The intermediate member 3 is not limited to one, and may be two or more. By using two or more intermediate members 3, the relative position and posture of the workpiece 1 with respect to the object 2 can be accurately positioned.

FIG. 5 is a diagram illustrating a state in which an abnormality is detected and stopped during assembly.
For example, in the operations (1) and (2), when galling or insertion failure occurs during assembly, the resistance in the insertion direction for moving the workpiece 1 toward the object 2 becomes excessive, and this is detected by the force sensor 14. Thus, the abnormality can be detected and the apparatus can be stopped.

  If it is a failure (No) at step S3 in FIG. 3, the workpiece 1 is returned to the position before the assembly work at step S4 (return step). That is, in this operation, the workpiece 1 is moved in a direction away from the object 2 along the axis of the cylindrical hole 2 a of the object 2.

Next, in step S5 (reassembly step), the fixing member 5 is virtually regarded as the object 2 and the assembling operation is re-executed with respect to the fixing member 5 into which the intermediate member 3 cannot be fitted.
The fixing member 5 to which the intermediate member 3 cannot be fitted is a member that does not have the hole 2a into which the intermediate member 3 is fitted. In the example described later, the upper surface is a fixed flat plate with a horizontal surface, but the object 2 without the hole 2a. It may be.
The fixing member 5 is fixed so as not to move to the work table 4 (see FIG. 1) at a position different from the object 2.

  In step S6 (fitting determination step), the fitting state of the workpiece 1 and the intermediate member 3 is determined from the position of the workpiece 1 being re-executed and the measured external force.

FIG. 6 is an explanatory view of the operation of fitting the intermediate member 3 that has come off the workpiece 1 to the workpiece 1 by the fixing member 5.
In this figure, (A) is a state in which the workpiece 1 is returned to the position before the assembly work in step S4, (B) is a state in which the assembly work is being re-executed in step S5, and (C) is a state after the re-execution. It is a schematic diagram which shows.
In the re-execution of the assembling operation in FIG. 6B, the assembling operation is re-executed with the fixing member 5 virtually regarded as the object 2 with respect to the fixing member 5 into which the intermediate member 3 cannot be fitted.

As shown in FIG. 6, in the method of the present invention, when the assembly work is unsuccessful (No in step S <b> 3), the inserted workpiece 1 with the intermediate member 3 is retracted in the direction away from the target object 2. 3 is removed from the object 2, the workpiece 1 is returned to the position before the assembly work (A), and the intermediate member 3 prepared in advance is moved to the place of the fixing member 5 where the fitting is impossible (step S4).
Next, with respect to the fixing member 5 to which the intermediate member 3 cannot be fitted, the fixing member 5 is virtually regarded as the object 2 and the assembly work (operations (1) to (3)) is performed again (B) ( C). If the intermediate member 3 is not detached by this assembling operation, the intermediate member 3 that is about to be detached by the pressing operation of moving the workpiece 1 toward the object 2 is attached to the workpiece 1 again (FIG. 6C).

Here, when the intermediate member 3 is ideally assembled to the workpiece 1, the upper surface position of the workpiece 1 for which the pressing control (reassembly operation) is completed is “ideal position a”, so that the assembly operation in step S2 is not hindered. The upper surface range of the work 1 for which the pressing control is completed when the intermediate member 3 is assembled to the work 1 is defined as an “allowable range b”.
At the ideal position a, the intermediate member 3 is located at the normal initial position in FIG.
Further, in the allowable range b, the intermediate member 3 is not in the initial position, but is positioned in a range where the intermediate member 3 can be positioned at the initial position in FIG.

In step S6 of FIG. 3, when the position of the workpiece 1 at the completion of re-execution of the assembly work in step S5 is the ideal position a or the allowable range b described above, the intermediate member 3 is in the allowable position. The workpiece 1 with the member 3 can be reused as it is.
Therefore, in this case, the process returns to step S2, and an assembly operation for fitting the intermediate member 3 fitted to the workpiece 1 to the object 2 is executed.

FIG. 7 is an explanatory diagram of an operation for detecting that the intermediate member 3 is detached from the workpiece 1 using the fixing member 5.
In this figure, (A) is a state in which the intermediate member 3 is detached from the workpiece 1, (B) is an initial state of re-execution of the assembly work, and (C) is an intermediate member 3 during re-execution of the assembly work. (D) is a schematic diagram showing a state in which the pressing operation has further progressed by a predetermined threshold or more from the position of (C).

If the intermediate member 3 is disengaged from the work 1, as shown in FIGS. 7C and 7D, when the pressing operation is performed by re-execution of the assembly work (step S5), the upper surface position of the work 1 is the ideal position. The workpiece 1 moves to a position advanced from a by force control.
Therefore, when the pressing is not completed (the pressing force is not detected) even if the ideal position a is exceeded and the allowable range b is exceeded, it is assumed that there is no intermediate member 3, and the workpiece 1 to be gripped in step S7 (dispensing step) is taken. Dispensing as a failed part, returning to S1, gripping the new workpiece 1 with the intermediate member 3 and continuing the operation.

Further, when the intermediate member 3 is detached and the intermediate member 3 cannot be assembled to the ideal position even after the pressing operation, the ideal position a and the allowable range b are not entered. Before proceeding, an abnormality in which the detected external force exceeds the threshold value is detected.
Therefore, if an abnormality in which the external force exceeds the threshold value is detected before entering the allowable range b, the intermediate member 3 is not assembled to the workpiece 1 in step S8 (dispensing step), and the gripped workpiece 1 is dispensed as a failed part. Returning to step S1, the new workpiece 1 with the intermediate member 3 is gripped and the operation is continued.

FIG. 8 is a diagram illustrating the relationship between the relative position between the workpiece 1 and the fixing member 5 and the fitting state between the workpiece 1 and the intermediate member 3.
In this figure, a is the ideal position described above, and b is the allowable range described above.
Further, c is an abnormal position where pressing is not completed even if the allowable range b is exceeded, and d is an abnormal position where the external force exceeds the threshold before entering the allowable range b.

When the upper surface of the workpiece 1 is normally positioned at the ideal position a or the allowable range b at the completion position of the pressing operation for moving the workpiece 1 toward the fixing member 5, as described above, the intermediate member 3 is set at the allowable position. It can be judged that there is.
When the upper surface of the work 1 is located at the abnormal position c, it can be determined that the intermediate member 3 is not present as described above.
Furthermore, when the upper surface of the workpiece 1 is located at the abnormal position d, it can be determined that the intermediate member 3 is not assembled to the workpiece 1 as described above.
Therefore, it is possible to determine whether or not to retry the gripped work 1 and the state of the intermediate member 3 at the completion position of the pressing operation for moving the work 1 toward the fixed member 5 as shown in FIG. it can.

In the above-described example, the intermediate member 3 is previously fitted in the hole 1a of the workpiece 1 (the workpiece 1 with the intermediate member 3), but the present invention is not limited to this.
That is, when the workpiece 1 is assembled not to the workpiece 1 with the intermediate member 3 attached to the workpiece 1 but to the “object 2 with the intermediate member 3” in which the intermediate member 3 is attached to the object 2. Also good. In this case, since it is detected that the intermediate member 3 is erroneously attached to the workpiece 1, it is possible to detect the presence of the intermediate member 3 by the pressing operation in the same manner as the pressing operation described above.

  In the above-described example, the workpiece 1 and the object 2 have the fitting holes 1a and 2a, the intermediate member 3 is a cylindrical member (bar or pin shape), and the intermediate member 3 is fitted into the fitting holes 1a and 2a. Although they are adapted, the relationship between the hole and the cylindrical member may be reversed.

As described above, according to the apparatus and method of the present invention, the intermediate member 3 that is preliminarily fitted to the workpiece 1 or the object 2 by the robot hand 12 having the force sensor 14, the robot arm 16, and the robot controller 20. Assembling work for assembling the workpiece 1 to the object 2 can be executed via the.
Further, the success or failure of the assembling work can be determined from the position of the workpiece 1 during the assembling work and the measured external force.

  Further, when the assembly work is unsuccessful, that is, when an abnormality is detected, the work 1 held by the robot hand 12 is returned to the position before the assembly work, and the force control is performed on the fixing member 5 in which the intermediate member 3 cannot be fitted at another place. By re-executing the assembly operation, it is possible to determine the fitting state of the intermediate member 3, that is, the presence or absence of the intermediate member 3 that can be detached from the workpiece 1, from the position of the workpiece 1 being re-executed and the measured external force. .

  Further, during the assembling operation, when the intermediate member 3 is correctly fitted to the workpiece 1, the intermediate member 3 has returned to the ideal position (regular position) again, so that the assembling operation can be retried as it is. Further, if the intermediate member 3 is not properly fitted to the workpiece 1, the intermediate member 3 cannot be returned to the ideal position (regular position), so that it is determined that it is difficult to continue the assembly work using the workpiece 1. The assembly work can be performed using the new workpiece 1 in which the intermediate member 3 is correctly fitted.

  Therefore, by this determination, (1) detection of presence / absence of intermediate member at the time of assembly failure, (2) check of soundness of intermediate member and its soundness, (3) determination of use of new parts at failure of sounding of intermediate member The effect which can perform operation | movement, (4) prevention of operation stop of an apparatus, etc. is acquired.

  In addition, this invention is not limited to embodiment mentioned above, is shown by description of a claim, and also includes all the changes within the meaning and range equivalent to description of a claim.

1 workpiece, 2 object, 3 intermediate member,
4 worktables, 5 fixing members,
10 assembly robot, 12 robot hand, 14 force sensor,
16 robot arm, 20 robot control device,
21 Storage device

Claims (4)

A robot hand having a force sensor for measuring an external force and holding a workpiece;
A robot arm capable of moving the position and posture of the robot hand in a three-dimensional space;
A robot control device that controls the robot arm and executes an assembly operation for assembling the workpiece onto an object via an intermediate member;
The robot controller determines the success or failure of the assembly work from the position of the workpiece during the assembly work and the measured external force,
When the assembly operation is unsuccessful, the workpiece is returned to the position before the assembly operation,
Next, for the fixing member to which the intermediate member cannot be fitted, the fixing member is virtually regarded as the object, and the assembly operation is performed again.
An assembly robot characterized in that a fitting state between the workpiece and the intermediate member is determined from the position of the workpiece being re-executed and the measured external force.   The said intermediate member is previously fitted by the said workpiece | work or target object, This intermediate member is fitted to a workpiece | work and a target object, and the said workpiece | work is assembled | attached to a target object. Assembly robot. A robot hand having a force sensor for measuring an external force and holding a workpiece;
A robot arm capable of moving the position and posture of the robot hand in a three-dimensional space;
(A) controlling the robot arm, and performing an assembly operation for assembling the workpiece onto an object via an intermediate member;
(B) determining the success or failure of the assembly operation from the position of the workpiece during the assembly operation and the measured external force;
(C) When the assembly work is unsuccessful, the work is returned to the position before the assembly work,
(D) Next, for the fixing member to which the intermediate member cannot be fitted, the fixing member is virtually regarded as the object, and the assembly operation is re-executed.
(E) A method for controlling an assembly robot, wherein a fitting state between the workpiece and the intermediate member is determined from the position of the workpiece being re-executed and the measured external force.   The control method according to claim 3, wherein in (E), the presence or absence of the intermediate member and the soundness of fitting with the workpiece are determined.