JP3078202B2 - Painting posture control method for articulated robot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a posture when a painting operation is performed by an articulated robot (manipulator) having six rotation axes.

[0002]

2. Description of the Related Art Conventionally, a robot (manipulator) having six rotation axes is, for example, as shown in FIG. 6, a turntable that is turned on a base 1 at a rotation angle θ1 about a first axis S1. 2, a first arm 3 that is turned on the turntable 2 at a rotation angle θ2 about a second axis S2 perpendicular to the first axis S1, and a second axis S2 at the tip end of the first arm 3. Rotated at a rotation angle θ3 about a third axis S3 parallel to
Arm 4 and a second arm 4 at the distal end side of the second arm 4.
A third arm 5 rotated at a rotation angle θ4 about a fourth axis S4 along the center of the third arm 5 and a fifth axis (wrist axis) S5 orthogonal to the fourth axis S4 at the tip of the third arm 5 A fourth arm 6 rotated at a rotation angle θ5 about the center, and a tool rotated at a tip end of the fourth arm 6 at a rotation angle θ6 about a sixth axis S6 along the center axis of the fourth arm. It is composed of a holder 7.

[0003] A spray gun for painting (hereinafter referred to as a painting gun) 8 is applied to the tool holder 7 using the articulated robot.
In order to form a uniform coating film on the surface to be coated by holding the robot, conventionally, the posture of the robot is clearly given by the Euler angle. That is, the joints having the first to sixth axes S1 to S6 are driven via actuators and reduction gears, respectively, so that the coating speed by the coating gun 8, the coating distance, and the angle of the spray axis C to the surface to be coated are kept constant. The coating is uniformly performed from the starting point A to the ending point B by moving the coating gun 8 parallel to the surface to be coated along the coating direction while holding.

[0004]

However, in the above-mentioned coating operation, for example, as shown in FIG.
In the posture position where the axis S6 is aligned and in the vicinity thereof, the fourth position
A point at which the rotation of the axis S4 becomes extremely large (referred to as a singular point E)
There is. This is because, in the above configuration, the joint velocity of the manipulator viewed from the Cartesian space velocity is calculated by an equation,

[0005]

(Equation 1) (Ν is a 6 × 1 Cartesian velocity vector, Θ is a joint angle vector of the manipulator, J is a 6 × 6 Jagobian determinant) This is because there is a point where the joint angular velocity becomes extremely large in J ⁻¹ (Θ). Furthermore, since the fourth to sixth axes S4 to S6 intersect, the structure of the wrist shown in FIG.
When the fourth axis S4 is rotated at a high speed with the fourth and sixth axes S6 aligned in a straight line, as shown in FIG. 7, in order to maintain the attitude of the coating gun 8 (the spread angle of the coating pattern), Fifth
The shaft S5 and the sixth shaft S6 also need to be rotated at high speed.

Therefore, if the coating speed is increased beyond a predetermined value, the maximum angular velocity of the joint will be exceeded near the displacement point E, making the coating difficult. The coating speed is reduced by being restricted by the maximum angular speed of the shafts S4 to S6, and there is a problem that the coating speed cannot be increased and efficiency is poor.

SUMMARY OF THE INVENTION The present invention solves the above problems, and eliminates the rotation of a joint at a singular point where two rotating axes are aligned in a multi-joint robot, thereby increasing the painting speed. It is an object to provide a control method.

[0008]

In order to solve the above problems, a method of controlling a painting posture of an articulated robot according to the present invention comprises a first axis, a second axis orthogonal to the first axis, and a second axis. , A fourth axis orthogonal to the third axis, a fifth axis orthogonal to the fourth axis, and a sixth axis orthogonal to the fifth axis. When painting on the surface to be painted by using a painting spray gun that forms a spray axis in the sixth axis direction by a robot, the painting speed is kept constant, the painting distance is kept constant, and the spread angle of the painting pattern Is fixed, the Euler angles are set for each axis so that the spray angle of the spray axis is within a predetermined range, and the fourth or sixth axis is fixed, so that the spray port of the spray gun for coating is coated. At the same time as moving in the direction It is intended to move in a circular arc line of the radius.

In the above structure, when the starting end of the coating is applied, the coating speed on the coating surface in the above-mentioned coating attitude control is applied in such a manner that the coating is applied from the thin film to the predetermined thickness, and the end of the coating is applied. When coating a film, the coating speed is reduced on the coated surface in the above-mentioned coating posture control, and the coating is thinned from a predetermined film thickness.

[0010]

[Function] Normally, it is necessary to keep the coating speed, the coating distance, and the spread angle in the coating pattern direction constant as the requirements for uniform coating work using a spray gun for coating. However, the coating of the spray shaft on the surface to be coated is required. It has been experimentally found that a uniform coating can be obtained when the angle of the spray axis is in the range of about 45 ° to 135 °. Therefore, while keeping the coating speed, coating distance, and divergence angle of the coating pattern by the coating spray gun constant, the position of the discharge port of the coating spray gun is set on an arc whose radius is the coating distance with the coating point as the center. If the spray axis is within a predetermined angle range, the coating can be performed uniformly.

In the above method, the fourth axis or the sixth axis is fixed, and the fifth axis is fixed in a direction orthogonal to the painting direction. The Euler angle of each axis is given to the robot so that the spread angle of the paint pattern and the spray angle of the spray axis become constant. The coating angle of the spray axis is continuously changed by this, and the discharge port of the spray gun for coating is moved on an arc having a coating distance as a radius around the coating point to form the fourth and sixth axes. In the vicinity of a singular point on which a straight line is arranged, there is no high-speed rotation of the joint, and uniform coating can be performed by the spray gun for coating. Therefore, the conventional high-speed rotation of the joint at the singular point is eliminated, and thus the angular velocity of the joint during normal painting work is not restricted, so that the painting speed can be further increased,
Coating work can be performed efficiently.

In the above control method, if the positions of the starting end and the end are different, the positions of the spray guns for painting are different from each other, so that it is extremely difficult to apply the conventional method of rotating the wrist. However, by only accelerating or decelerating only the coating speed under the same attitude control as that of the uniform coating portion, the blur coating can be easily performed. Therefore, the coating thickness of the seam of the coating can be made constant by overlapping the blur coating.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for controlling a painting posture of an articulated robot according to the present invention will be described below with reference to the drawings. The same members as those in the related art are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 1, when a coating gun 8 is moved by using a six-axis articulated robot and a coating film having a constant thickness is formed along a coating line L from a start point A to an end point B,
As the requirements, the moving speed of the coating point P where the spray axis C intersects the surface G to be coated, that is, the coating speed V, the coating distance CD from the discharge port of the coating gun 8 to the coating point P, and the coating for the coating line L It is necessary to keep the spread angle α of the pattern CP constant. However, in order to form a uniform coating film, the coating angle β of the spray axis C with respect to the surface G to be coated does not always need to be 90 °, and the coating angle β is approximately 45 °.
It has been experimentally found that a uniform coating film can be obtained within an appropriate angle range Sβ of from 135 ° to 135 °. Accordingly, in order to keep the coating width constant by the spread angle α of the coating pattern CP, the coating line L is perpendicular to the surface G to be coated.
On the arc line R whose radius is the coating distance CD around the coating point P on the plane H including
If it is β, a uniform coating film can be formed at the painting point P.

Here, for a 6-axis articulated robot,
By giving the coating direction along the coating line L, the coating distance CD, the spread angle α of the coating pattern CP, and the direction of the spray axis C in Euler angles as coating conditions, and giving the condition that the width of the coating pattern CP is not changed, The position of the discharge port of the painting gun (spray gun for painting) 8 is located on the circular arc line R. Here, in order to uniquely determine the posture of the articulated robot, a condition is added that the fourth axis S4 (or the sixth axis S6) having a large angular velocity at the conventional singular point E is fixed.

Under the above conditions, the conventional fourth axis S4 and sixth axis S
6 is a straight line, and in a painting operation including a conventional singular point, Y
Each paint position on the coordinates (paint line direction) and the first to sixth axes
The relationship between the rotation speeds of the axes S1 to S6 is shown in FIG. 2, and the coordinates of the coating gun 8 and the first to sixth axes S1 to S6 are shown.
Are as shown in Table 1.

[0017]

[Table 1] At this time, the trajectory of the articulated robot is schematically shown in FIG.
As shown in FIG. Therefore, each actuator rotates the first axis S1 at a substantially constant angular velocity, rotates the fourth axis S4 about the first axis S1 from the direction of the start point A to the direction of the end point B, and rotates the fourth axis S4 with the second axis S2. The coating distance CD is adjusted by swinging the first arm 3 back and forth, the third axis S3 is rotated to correct the angle change of the fourth axis S4 due to the first arm 3, and the fifth axis S5 is adjusted. It rotates to control the coating angle β of the coating gun 8. As a result, it is possible to eliminate the conventional increase in the rotation speed at the singular point where the fourth axis S4 and the sixth axis S6 are aligned, and to obtain a uniform coating state.

By the way, as shown in FIG. 5, a starting end a from a coating start point A 'to a start point A where a constant coating film thickness T is formed.
At the end b from the end point B to the coating end point B ', the coating formed by the previous coating operation and the coating formed by the next coating operation are overlapped to have a constant thickness. A blur coating for forming the film thickness T 'is performed. In the conventional attitude control for moving the coating gun 8 in parallel, the coating angle β at the start point A and the end point B is usually constant at 90 °, and
Since the distance between the paint gun 8 and the paint gun 8 is the same as the paint distance CD, the paint gun 8 can be accelerated or decelerated and rotated about the fifth axis S5, and the blur coating can be performed at the start end a and the end end b. Could do it.

However, in the above posture control, since the coating angle β of the coating gun 8 at the starting point A and the ending point B is not constant, it is not easy to control the coating speed by rotating the wrist as in the prior art. Here, as shown in FIG. 5, the coating is performed by reducing and accelerating the coating speed by the same attitude control method as that of the uniform coating portion. Therefore,
Even if the posture of the coating gun 8 at the start point A and the end point B is not constant, it is possible to perform the faint coating easily regardless of the posture, and to make the coating thickness of the seam of the coating constant. it can.

[0020]

As described above, according to the present invention, the fourth axis or the sixth axis is fixed, and the fifth axis is fixed in a direction orthogonal to the painting direction. Set the rotation direction, so that the coating speed and the spreading angle of the coating pattern and the coating angle of the spray axis are constant.
The Euler angles of each axis are given to the robot. By changing the coating angle of the spray axis continuously, and moving the discharge port of the spray gun for coating on an arc whose radius is the coating distance centered on the coating point, the fourth axis and the sixth axis are moved. There is no high-speed rotation of the joint even near the singular point where
Uniform coating can be performed with a spray gun for coating. Therefore, the conventional high-speed rotation of the joint at the singular point is eliminated, and the angular velocity of the joint during normal painting work is not regulated, so that the painting speed can be further increased and the efficiency can be improved. Painting work can be performed.

In the above control method, if the positions of the start end and the end are different, the positions of the spray guns for painting are different from each other. Therefore, it is extremely difficult to perform the blur coating by the conventional method of rotating the wrist. However, by only accelerating or decelerating only the coating speed under the same attitude control as that of the uniform coating portion, the blur coating can be easily performed. Therefore, the coating thickness of the seam of the coating can be made constant by overlapping the blur coating.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of a method of controlling a painting posture of an articulated robot according to the present invention.

FIG. 2 is a graph showing a rotation speed of a joint of an articulated robot according to the coating control method.

FIG. 3 is a perspective view illustrating an operation of the articulated robot according to the coating control method.

FIG. 4 is a plan view illustrating an operation of the articulated robot according to the coating control method.

FIG. 5 is a graph illustrating operations at a start end and an end according to the coating control method.

FIG. 6 is a perspective view showing a conventional articulated robot.

FIG. 7 is a graph showing a rotational speed of a joint of an articulated robot according to a conventional coating control method.

FIG. 8 is a sectional view showing a structure of a joint of a conventional articulated robot.

[Explanation of symbols]

 S1 1st axis S2 2nd axis S3 3rd axis S4 4th axis S5 5th axis S6 6th axis 8 Spray gun for painting (painting gun) C Spray axis L Painting line P Painting point CD Painting distance CP Painting pattern V Painting Speed G Painted surface α Spread angle of paint pattern β Paint angle R Arc line A Start point B End point

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Sadaya 3-28, Nishikujo, Konohana-ku, Osaka-shi, Osaka Within Hitachi Zosen Corporation (72) Inventor Yukio Saito 5 Nishikujo, Konohana-ku, Osaka-shi, Osaka No. 3-28, Hitachi Zosen Corporation (56) References JP-A-62-241010 (JP, A) JP-A-63-64101 (JP, A) JP-A-8-252495 (JP, A) (58 ) Surveyed field (Int.Cl. ⁷ , DB name) G05B 19/18-19/46 B25J 3/00-3/04 B25J 9/10-9/22 B25J 13/00-13/08 B05B 12/00 -13/06

Claims (2)

(57) [Claims] 1. A first axis, a second axis orthogonal to the first axis, a third axis parallel to the second axis, a fourth axis orthogonal to the third axis, and orthogonal to the fourth axis. The fifth axis and the sixth axis orthogonal to the fifth axis
With a multi-joint robot that is rotatable about each axis, when painting on the surface to be painted using a painting spray gun that forms a spray axis in the sixth axis direction, while maintaining a constant painting speed, The Euler angles are set for each axis, and the fourth or sixth axis is fixed so that the coating distance is constant, the spread angle of the coating pattern is constant, and the spray angle of the spray axis is within a predetermined range. A painting attitude control method for an articulated robot, characterized in that the spraying port of the painting spray gun is moved in the painting direction and, at the same time, is moved on an arc line having the painting distance as a center around the painting point. 2. The method according to claim 1, wherein when the starting end of the coating is coated, the coating speed on the coating surface in the above-mentioned coating posture control is applied in a blurring manner so that the coating film is formed from a thin film to a predetermined film thickness. 2. A method according to claim 1, wherein said coating attitude control is carried out to reduce the thickness of the coating from a predetermined thickness while increasing the coating speed on the coating surface.