JPH0411357B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an interference prevention method in a robot that prevents a tool attached to the wrist of the robot from interfering with the robot body etc. due to rotation of the wrist. It is something.

<Prior Art> In general, in a six-axis control robot, a wrist portion is supported at the tip of the robot body so as to be able to rotate around three mutually orthogonal axes, and each of these axes has a defined range of motion. The wrist can be moved freely within this range.

<Problems to be Solved by the Invention> By the way, in a 6-axis control laser processing machine in which this type of robot is applied to laser processing, a relatively long tool (torch) is attached to the tip of the wrist. Even if the movement of the part is within the above-mentioned movable range, a situation may occur where the tool interferes with the robot body or the wrist part.

However, at present, interference with tools is only avoided based on the judgment of the operator, and for example, during teaching, it is necessary to use a considerable amount of nerve to avoid interference with tools.

<Means for Solving the Problems> The present invention has been made to solve the above-mentioned conventional problems, and includes a robot body equipped with a wrist portion on which a tool is attached so as to be controllable in at least two axes, The angles of the two axes whose representative points coincide with the coordinate values of the representative points of the robot body or the wrist are calculated in advance, and the angular range where the tool interferes with the robot body or the wrist is set and stored for each of the two axes. When the command angles of the two axes both fall within the angular range stored in the storage device when commanding the movement of the wrist part, an error message is output to limit the movement of the wrist part.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 shows a laser processing machine using a six-axis control robot, and this laser processing machine is based on a Cartesian coordinate robot 10. As shown in FIG. robot 10
consists of two columns 11 parallel to each other, a table 12 that is guided and slidable on the columns 11 in the X-axis direction, and a carriage 13 that is guided and slidable on the table 12 in the Y-axis direction. , and a head 14 that is guided and slidable on the carriage 13 in the Z-axis direction. Furthermore, head 14
A fourth axis wrist part 15 is supported at the tip of the fourth axis wrist part 15 so as to be rotatable around an axis parallel to the Z axis, and a fifth axis wrist part 15 is supported at the tip of the fourth axis wrist part 15 so as to be rotatable around an axis line perpendicular to the fourth axis wrist part 15. A sixth axis wrist part 17 is supported at the distal end of the fifth axis wrist part 16 so as to be pivotable about an axis perpendicular to the fifth axis wrist part 16.
A tool (torch) 18 is attached to the sixth axis wrist portion 17, and a laser beam emitted from a laser oscillator (not shown) is irradiated from the tool 18 toward the workpiece.

In the following description, the fourth, fifth, and sixth axis wrist portions 15, 16, and 17 will simply be referred to as the fourth axis, the fifth axis, and the fourth axis.
This is abbreviated as the 6th axis.

Figure 2 shows the robot control circuit.
is a central processing unit consisting of a microcomputer, etc., and this central processing unit 20 includes a memory 2.
5. Servo motor drive circuit 2 that drives the servo motors M1 to M6 for each axis attached to the robot.
2a to 22f, operation panel 26 for instructing teaching points, etc.
is installed. Each servo motor drive circuit 2
2a to 22f calculate the deviation between the output data output from the central processing unit 20 and the outputs of the encoders E1 to E6 connected to the servo motors M1 to M6, and adjust the speed according to the magnitude of this deviation. The servo motors M1 to M6 are driven by the servo motors M1 to M6.

The memory 25 stores data representing the positioning point of the tool 18, and the operation panel 26
The robot operating program input by the operation is stored. Further, the memory 25 is provided with an area for storing data representing the interference area, and data of the interference area calculated as described later is stored in this area.

Next, in the 6-axis controlled laser processing machine configured as described above, the angular region where the tool 18 interferes with the robot body (head 14) or the fourth axis is set by a combination of rotations of the fifth and sixth axes. The processing will be explained with reference to FIGS. 3 to 7.

First, let us explain the process of setting the operating limit of the fifth axis with reference to Figure 3. In the figure, O ₅ is the rotation center of the fifth axis, and this is the coordinate origin O ₅ (x=0, y=
0). Further, P ₁ and P ₂ indicate representative points of the robot body 14, and P ₅ indicates a representative point of the tip of the tool 18. Here, the representative point P ₁ of the robot main body 14,
If the x-coordinate value of the straight line P ₁ and P ₂ connecting P ₂ is -m, then
The tool 18 is rotated by the clockwise rotation movement of the fifth axis.
interferes with the robot body 14 when the x-coordinate value of the representative point _P5 at the tool tip becomes greater than -m. Therefore, the x-coordinate value x5 of tool representative point _P5
By finding the angle α such that x5=-m,
You can now set the operating limits for the 5th axis.

The following describes the angle α and the process of calculating the interference occurrence area of the fifth axis from this angle α. Here the 6th
The intersection of the axis of rotation of the shaft and the center line of the tool 18 is O ₆
Then, the distance between the two points O ₅ and O ₆ is l ₁ , the distance from point O ₆ to the tip of the 6th axis is l ₂ , and the axial length of the tool 18, that is, from the tip of the 6th axis to the tip of the tool. The distance t ₁ and the radius dimension t ₂ of the tool 18 are registered in the memory 25 as known dimensions. The tip representative point _P5 of the tool 18 described above is set at the point where the tip surface of the tool 18 intersects a straight line parallel to the tool center and offset by the radial dimension _t2 in the radial direction,
The intersection of this straight line and the straight line connecting the points O ₅ and O ₆ is
Define O ₆ ′.

Therefore, the angle .alpha. at which the x-coordinate value of the point _P5 becomes -m can be calculated using the following equation from two right triangles having one side in common as shown in FIG.

α=90゜−(A1+A2) tanA1=(l ₂ +t ₁ )/(l ₁ −t ₂ ) From the angle α calculated in this way, the angular range of the fifth axis in which the tool 18 does not interfere with the robot body 14 is an angle a in the + direction (clockwise) from the original position shown by the two-dot chain line in FIG. One direction (counterclockwise)
The angle b becomes the angle b, and these angles a and b are stored in a predetermined data area of the memory 25 as the upper limit value and lower limit value of the interference occurrence area of the fifth axis.

Next, the process of setting the operating limit of the sixth axis will be explained with reference to FIG. In the same figure, O ₆ indicates the rotation center of the sixth axis, which is the coordinate origin O ₆ (x=0, y=
0). Further, P ₃ and P ₄ indicate representative points of the robot main body 14, and P ₆ indicates a representative point of the tool 18.
Here, if the x-coordinate value of the straight lines P ₃ and P 4 connecting the representative points P ₃ and _{P 4 of} the robot body 14 is m, the tool 18 is moved toward the robot body by the counterclockwise rotational movement of the sixth axis. 14 occurs when the x-coordinate value of the representative point _P6 of the tool 18 becomes smaller than m. Therefore, by finding the angle β such that the x-coordinate value x6 of _P6 satisfies x6=m, it becomes possible to set the operating limit of the sixth axis.

The angle β and the process of calculating the interference occurrence area of the sixth axis from this angle β will be described below.

In this case, based on the same idea as in the case of the fifth axis mentioned above, the angle β at which the x-coordinate value of the point P ₆ is m is calculated from the two right triangles with one side in common shown in Fig. 6 as follows. It can be calculated like an expression.

β=90°−(A3+A4) tanA3=t ₂ /l ₂ sinA4=m/√ ₂ ² + ₂ ² Therefore, the angular range of the 6th axis in which the tool 18 does not interfere with the robot body 14 is the two points in FIG. From the original position indicated by the chain line, there is an angle c in the + direction (clockwise) and an angle d in one direction (counterclockwise), and these angles c and d are stored in the memory 25 as the upper and lower limits of the interference occurrence area of the 6th axis. is stored in a predetermined data area.

Incidentally, FIG. 7 shows a flowchart for calculating the upper limit values, lower limit values a, b, c, and d of the interference occurrence area of the fifth and sixth axes mentioned above.

Next, the operation of the six-axis controlled laser processing machine will be explained based on the flowchart of FIG.

First, in step 50, the wrist parts 15, 16,
17 operation commands θ4, θ5, θ6 are given, and then in step 51, the upper and lower limits a,
b, c, d are read. In step 52, it is determined whether the command angle θ5 of the fifth axis is larger than the upper limit value a and smaller than the lower limit value b (a≦θ5≦b), and if NO, the process moves to step 53 and the operation command is issued. If the answer is YES, the process moves to step 54. In step 54, it is determined whether the command angle θ6 of the sixth axis is larger than the upper limit value c and smaller than the lower limit value d (c≦θ6≦d), and if NO, the process moves to step 53 and the operation starts. The command is executed, and if the answer is YES, the process moves to step 55, where a message indicating the occurrence of interference is output.

In this way, only when the command angles of the 5th and 6th axes are both in the interference generation area, an error message indicating that interference has occurred is output and the robot operation command is stopped, and the 5th and 6th axes If any one of the commanded angles is outside the interference occurrence area, the operation command is executed assuming that there is no risk of interference.

In the above embodiment, an example was described in which a 6-axis control robot was applied to a laser processing machine.
The present invention can also be applied to work robots for welding, painting, etc. where tools attached to the wrist may interfere with the robot body, etc., and the number of control axes is not limited to six axes. Without,
This can be applied to a robot having a wrist portion that can be controlled in at least two axes.

<Effects of the Invention> As described above, the present invention calculates in advance the angles of the two axes of the wrist of the robot at which the representative point of the tool coincides with the coordinate values of the representative point of the robot body or the wrist. The angle range in which the tool interferes with the robot body or the wrist is set respectively, and it is determined whether the tool attached to the wrist interferes with the robot body, etc. depending on the combination of the operation command angles of the two axes when the operation is commanded. The system determines the difference between the robot and the wrist and outputs an error message based on the determination result to prevent the tool from interfering with the robot body or wrist, which requires a high-speed processing device with a small amount of calculation and storage capacity. The safety of the robot can be improved without causing any problems, and since there is no need to be nervous during teaching, the load on the operator can be reduced and the teaching time can be shortened.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIG. 1 is a perspective view showing an example in which a 6-axis control robot is applied to a laser processing machine, FIG. 2 is a diagram showing a robot control circuit, and FIGS. The figure shows the operation for setting the interference angle area of the 5th and 6th axis wrist parts, Figures 5 and 6 are model diagrams of Figures 3 and 4, and Figure 7 shows the interference angle area. A flowchart for setting and FIG. 8 is a flowchart for executing the operation command. 14... Robot main body, 15, 16, 17... Wrist part, 18... Tool.

Claims (1)

[Claims] 1 A method in which a robot body is provided with a wrist part that can be controlled in at least two axes, and a tool attached to the wrist part is prevented from interfering with the robot body or the wrist part, and the representative point of the tool is calculating and determining angles on two axes that correspond to the coordinate values of representative points of the wrist, and setting and storing angular regions in which the tool interferes with the robot body or the wrist for each of the two axes;
A method for preventing interference in a robot, which outputs an error message to limit the movement of the wrist part when command angles of two axes both fall within the set interference region when the wrist part is commanded to operate.