JP2017007065A - Articulated robot positioning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy in positioning an end effector of a vertically articulated robot without causing an increase in cost.SOLUTION: While rotary joints 11, 22, 23, 13 that are arranged so that the rotation axle thereof are directed in a direction crossing with a vertical direction (such as horizontal direction) are fixed, other rotary joints 21, 12, 24 that are arranged so that the rotation axle thereof are directed in a vertical direction and a direct advance joint 30 that is arranged so that the direct advance axis thereof is directed in a direction crossing with a horizontal direction are driven, whereby three-dimensional position of the end effector 3 is adjusted.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for positioning an end effector of a vertical articulated robot.

  As an articulated robot for industrial use, a horizontal articulated robot (for example, refer to Patent Document 1) and a vertical articulated robot (for example, refer to Patent Document 2) are known. The horizontal articulated robot has a high vertical rigidity and can position the end effector with high accuracy, but its movement is limited because of its narrow movable range. On the other hand, the vertical articulated robot has a wide movable range and can perform various operations. However, since the vertical rigidity is low, it is difficult to position the end effector with high accuracy.

JP 2003-266252 A JP-A-11-115838

  Horizontal articulated robots and vertical articulated robots each have the advantages and disadvantages described above. For example, a vertical articulated robot is provided in a process that requires various operations, and the end effector must be positioned with high accuracy. Ideally, a horizontal articulated robot is provided in the process. However, as described above, if different robots are provided according to the work of each process, the equipment cost increases.

  For example, the positioning accuracy of the end effector can be improved by processing each component constituting the link or joint of the vertical articulated robot with high accuracy. However, if each part is processed with high accuracy, the processing cost increases.

  From the above circumstances, the technical problem to be solved by the present invention is to improve the positioning accuracy of the end effector of the vertical articulated robot without incurring high costs.

  In order to solve the above-mentioned problems, the present invention provides a positioning of a vertical articulated robot including a multi-joint arm having a plurality of rotary joints and a rectilinear joint, and an end effector provided at a tip of the multi-joint arm. In another method, the rotary joint arranged so that the rotation axis is in a direction intersecting the vertical direction is fixed, and the other rotary joint arranged so that the rotation axis is in the vertical direction, and the straight axis A vertical articulated robot positioning method is provided that adjusts the three-dimensional position of the end effector by driving a rectilinear joint disposed so as to be in a direction intersecting the horizontal direction.

  Among a plurality of rotary joints provided on the multi-joint arm, a rotary joint (non-vertical axis rotary joint) arranged in a direction where the rotation axis intersects the vertical direction rotates while displacing the end effector in the vertical direction. , Rotation accuracy is susceptible to gravity. On the other hand, the rotation joint (vertical axis rotation joint) in which the rotation axis is arranged in the vertical direction moves the end effector in the horizontal plane without displacing the end effector in the vertical direction, so that the rotation accuracy is not easily affected by gravity. The present inventors pay attention to this point, and in a state where a non-vertical axis rotary joint that is easily affected by gravity is fixed, a vertical axis rotary joint that is not easily affected by gravity and a direction in which the straight axis intersects the horizontal direction The vertical articulated robot is pseudo-driven as a horizontal articulated robot by driving a rectilinear joint arranged in a vertical direction (for example, in the vertical direction). The vertical articulated robot is characterized in that the end effector can be moved freely by driving a plurality of rotary joints. In the present invention, however, a part of the rotary joints are fixed and the vertical articulated robot is fixed. By restricting the operation of the robot, it is possible to prevent a decrease in the rotation accuracy of the rotary joint due to the influence of gravity and to increase the positioning accuracy of the end effector.

  As described above, by using the vertical articulated robot as a horizontal articulated robot in a pseudo manner, the end effector can be positioned with high accuracy without incurring high costs.

It is a side view which shows a vertical articulated robot typically. It is a side view which shows the state which bent the said vertical articulated robot. FIG. 3 is a side view of a horizontal articulated robot simulating the vertical articulated robot in the state of FIG. 2.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the vertical articulated robot 1 of the present embodiment is attached to the articulated arm 2 whose base end (lower end in the figure) is fixed and the distal end (upper end in the figure) of the articulated arm 2. And an end effector 3. As the end effector 3, for example, a hand portion that holds the workpiece, a positioning member that abuts on the workpiece and finely adjusts the position of the workpiece, a welding portion that welds the workpiece, a nut runner that fastens a bolt, or the like is provided.

  The multi-joint arm 2 includes a plurality of links 4 and a plurality of joints provided between two adjacent links 4. The articulated arm 2 of the present embodiment is provided with a rotary joint that rotates the two links 4 around the rotation axis and a rectilinear joint 30 having a vertical lifting axis as joints. In the illustrated example, the articulated arm 2 is provided with a total of eight joints, that is, seven rotary joints and one rectilinear joint 30 (that is, having eight degrees of freedom).

  As the rotary joints, bending joints 11 to 13 for bending the two links 4 and torsion joints 21 to 24 for relatively rotating the two links 4 arranged coaxially are provided. In the present embodiment, the first torsion joint 21, the first bending joint 11, the second torsion joint 22, the second torsion joint 12, the third torsion joint 23, in order from the base end side of the multi-joint arm 2 as the rotation joint. A third bending joint 13 and a fourth torsion joint 24 are provided.

  The rectilinear joint 30 linearly translates the links 4 provided on both sides thereof by, for example, a ball screw mechanism or a rack and pinion mechanism. In the illustrated example, the rectilinear joint is configured to relatively move the links 4 on both sides arranged on the same axis in the direction of the rectilinear axis parallel to both the links 4. The rectilinear joint 30 of this embodiment is provided as the most proximal end joint among the plurality of joints provided in the multi-joint arm 2, and the proximal end side of the rectilinear joint 30 is connected to the fixed link 4. ing. For this reason, the rectilinear axis of the rectilinear joint 30 is fixed in a direction intersecting the horizontal direction, specifically in the vertical direction. When the rectilinear joint 30 is driven, the entire portion of the multi-joint arm 2 on the distal end side relative to the rectilinear joint 30 is parallel to the rectilinear axis direction (vertical direction in the illustrated example) with respect to the fixed base end side link 4. Moving.

  Hereinafter, a method of positioning the end effector 3 of the vertical articulated robot 1 at a predetermined position will be described.

  First, each rotary joint of the vertical articulated robot 1 is rotated so that the rotation axis of the second bending joint 12 is in the vertical direction as shown in FIG. In the illustrated example, the second torsion joint 22 and the third torsion joint 23 are rotated in a state where the links 4 on both sides of the first and third bend joints 11 and 13 are bent by 90 °, whereby the second bend joint is obtained. 12 and the rotation axis of the fourth torsion joint 24 is a vertical direction. Thus, the first bending joint 11, the second torsion joint 22, the third torsion joint 23, and the third bending joint 13 are arranged so that the rotation axis is in a direction (horizontal direction in the present embodiment) intersecting the vertical direction. (These rotary joints are referred to as horizontal rotary joints). On the other hand, the first torsion joint 21, the second bending joint 12, and the fourth torsion joint 24 are arranged so that the rotation axis is in the vertical direction (these rotation joints are referred to as vertical axis rotation joints).

  In this state, the horizontal axis rotary joints 11, 22, 23, and 13 are fixed (in FIG. 2, (F) is added to the reference numerals of the fixed rotary joints). As a method of fixing the horizontal axis rotary joints 11, 22, 23, and 13, for example, a method of restricting rotation with a brake provided in each joint, or a locking of a pin or the like that engages each joint in the rotational direction. A method of restricting rotation by inserting a member can be employed.

  The end effector 3 is moved to a predetermined position by driving only the vertical axis rotary joints 21, 12, 24 and the rectilinear joint 30 with the horizontal axis rotary joints 11, 22, 23, 13 fixed in this manner. At this time, the vertical articulated robot 1 is virtually driven as a horizontal articulated robot 1 ′ having a first horizontal link 41 and a second horizontal link 42 as shown in FIG. 3. In the horizontal articulated robot 1 ′, the base end of the first horizontal link 41 is connected to the first torsion joint 21 via the vertical link 43, and the tip end of the first horizontal link 41 is connected to the second bending joint 12. The The proximal end of the second horizontal link 42 is connected to the second bending joint 12, and the distal end of the second horizontal link 42 is connected to the fourth torsion joint 24 via the vertical link 44. When the first torsion joint 21 is driven, the first horizontal link 41 rotates in the horizontal plane around the rotation axis of the first torsion joint 21. When the second bending joint 12 is driven, the first horizontal link 41 and the second horizontal link 42 are bent in the horizontal plane. Accordingly, the end effector 3 can be disposed at an arbitrary horizontal position within the movable range of the horizontal links 41 and 42 by the first torsion joint 21 and the second bending joint 12.

  Further, the end effector 3 can be displaced in the vertical direction by driving the rectilinear joint 30. Therefore, by driving the first torsion joint 21, the second bending joint 12, and the rectilinear joint 30, the end effector 3 can be disposed at a predetermined three-dimensional position.

  In the present embodiment, the fourth torsion joint 24 is arranged such that the rotation axis is in the vertical direction, and the end effector 3 is arranged on an extension line of the rotation axis. By driving the fourth torsion joint 24, the end effector 3 can be rotated on the spot around the rotation axis of the fourth torsion joint 24.

  Since the horizontal axis rotary joints 11, 22, 23, and 13 are for displacing the end effector 3 in the vertical direction, the rotation angle may be displaced by the weight of the end effector 3. Therefore, by fixing the horizontal axis rotary joints 11, 22, 23, and 13 as described above, it is possible to prevent the rotational angles of these rotary joints from being displaced due to the influence of gravity.

  On the other hand, since the vertical axis rotary joints 21, 12, and 24 rotate the end effector 3 in a horizontal plane, the rotation angle is hardly displaced by the weight of the end effector 3. The rectilinear joint 30 is less susceptible to gravity than the rotary joint. In particular, when having a booster mechanism such as a ball screw mechanism or a rack and pinion mechanism, the rectilinear joint 30 is displaced in the rectilinear axis direction by the weight of the end effector 3 or the like. There is little to do. In this manner, the end effector is driven by driving the vertical rotary joints 21, 12, and 24 and the rectilinear joint 30 that are not easily influenced by gravity, and driving the vertical articulated robot 1 as a horizontal articulated robot 1 ′ in a pseudo manner. 3 can be prevented from being displaced due to its own weight or the like. That is, in the vertical articulated robot 1 capable of various operations, the rotation of the rotary joint due to gravity is prevented by fixing a part of the rotary joints and restricting the operation, thereby increasing the positioning accuracy of the end effector 3. Can be increased.

  The positioning method of the end effector 3 of the vertical articulated robot 1 as described above can be applied to the position correction of the workpiece W as described below.

  First, the workpiece W picked up by another vertical articulated robot is arranged at a predetermined position. The vertical articulated robot 1 is driven with respect to the workpiece W, the end effector 3 (positioning member) is arranged at a predetermined position, and the end effector 3 is brought into contact with the workpiece W. And it is confirmed whether the end effector 3 is correctly arrange | positioned in the predetermined position set beforehand. For example, the coordinates (three-dimensional position and orientation) of the end effector 3 moved to a predetermined position are acquired by a coordinate acquisition unit (not shown). The actual coordinates of the end effector 3 acquired in this way are compared with the coordinates (reference coordinates) of the normal position of the end effector 3 set in advance.

  If the difference between the actual coordinates of the end effector 3 and the reference coordinates is within an allowable range, it is determined that the end effector 3 is accurately placed at a predetermined position and the workpiece W is correctly placed. On the other hand, if the difference between the actual coordinates of the end effector 3 and the reference coordinates exceeds the allowable range, it is determined that the end effector 3 is not accurately arranged at a predetermined position, and the position of the end effector 3 is corrected. . Specifically, the magnitude and direction of the actual coordinate shift with respect to the reference coordinate of the end effector 3 are calculated, and the vertical articulated robot 1 is driven based on the calculated value, and the three-dimensional position of the end effector 3 is corrected. The

  At this time, the amount of movement of the end effector 3 for correction is often small, but it is not easy to perform such minute position correction by the vertical articulated robot 1. In the present embodiment, as described above, among the joints of the multi-joint arm 2, the horizontal axis rotary joints 11, 22, 23, and 13 are fixed, and only the vertical axis rotary joints 21, 12, 24, and the straight joint 30 are driven. By doing so, the end effector 3 can be moved with high accuracy. Thereby, a minute position correction of the end effector 3 becomes possible, and the workpiece W can be arranged at a regular position with high accuracy.

  The positioning method of the vertical articulated robot 1 as described above can be applied to an assembly process for joining a plurality of workpieces (for example, an assembly process of an automobile panel component (side panel, roof panel, door panel, etc.)).

  When assembling relatively large parts such as automobile panel parts, it is necessary to join other workpieces to large workpieces that are accurately placed in the specified position. It is not easy to place in. For this reason, usually, in the assembly process of the panel part of an automobile, a dedicated jig for positioning each other in a state where a plurality of workpieces are combined is often used. On the other hand, according to the positioning method using the vertical articulated robot 1 as described above, since a large workpiece can be accurately placed at a regular assembly position, both of them can be used without using a positioning jig. Work pieces can be combined accurately. This eliminates the need for a jig, thereby reducing costs and improving the versatility of the assembly equipment.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the case where the rotation joint arranged so that the rotation axis is in the horizontal direction is fixed is shown. However, the rotation axis is not limited to this, and the rotation axis is in the horizontal direction and the vertical direction. You may arrange | position so that it may incline with respect to a direction, and may fix the said rotation joint in this state. Specifically, for example, by driving the third torsion joint 23, the rotation axis of the third bending joint 13 is inclined with respect to the horizontal direction and the vertical direction, and the both rotation joints 23 and 13 are fixed in this state. May be.

  The type of the end effector 3 is not limited to the above. For example, the end effector 3 can be tilted by providing the end effector 3 with a rotation shaft or a cam mechanism (that is, the end effector 3 can be rotated around the rotation axis in the direction intersecting the vertical direction). ).

  The configuration of the vertical articulated robot 1 is not limited to the above, and the number, type, arrangement, and the like of joints provided in the articulated arm 2 may be changed as appropriate. For example, in the above-described embodiment, the case where the rectilinear joint 30 is provided as the most proximal joint among the plurality of joints is not limited to this. For example, the rectilinear joint 30 linearly travels between the plurality of rotary joints. A joint 30 may be provided. In this case, the rectilinear joint 30 is driven in a state in which the rectilinear axis is arranged in the vertical direction, and is driven in a state in which the rectilinear axis is arranged in a direction inclined with respect to the horizontal direction and the vertical direction. May be.

  Further, the number of joints provided in the vertical articulated robot 1 is not limited to eight, and may be nine or more or seven or less. Further, the number of rotary joints is not limited to 7, and may be 8 or more, or 6 or less. Further, the number of rectilinear joints is not limited to one and may be two or more.

DESCRIPTION OF SYMBOLS 1 Vertical articulated robot 1 'Horizontal articulated robot 2 Articulated arm 3 End effector 4 Link 11-13 Flexion joint (rotation joint)
21-24 Torsional joint (rotary joint)
30 Straight joint

Claims (1)

A vertical articulated robot positioning method comprising a plurality of rotary joints, an articulated arm having a rectilinear joint, and an end effector provided at a tip of the articulated arm,
With the rotary joint arranged so that the rotation axis intersects the vertical direction fixed, the other rotation joint arranged so that the rotation axis becomes vertical, and the rectilinear axis intersects the horizontal direction A method for positioning a vertical articulated robot that adjusts the three-dimensional position of the end effector by driving a rectilinear joint that is arranged so as to be in a direction to move.

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