JPH0732281A - Robot control device - Google Patents

Abstract

PURPOSE:To correctly position a working point on a working path to improve working accuracy by providing a control means so that a position and an attitude based on teaching data can be corrected to position the working point on the working path according to coordinates detected by a sensor. CONSTITUTION:The ridge line of a step formed by overlapping two plane-state substances Ws is adopted as a working path. This ridge line swings a laser beam outputted by a sensor S in the direction perpendicular to the ridge line to detect a part wherein the output is changed steplikely. Coordinates in a coordinates system fixed to the sensor S in a detecting point existing on a working path is operated by the sensor S. When a working point is positioned on a given working path according to teaching data, in consideration of a delay to the detecting point in a working point these coordinates are added, finely adjusting the positioning of the working point on the working path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot controller for fixing a tool to a tool base, holding a workpiece by a robot, and controlling the position and posture of the robot to machine the workpiece. The present invention relates to an improved device for accurately positioning on a predetermined processing path.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Laid-Open No. 2-82302, a tool is fixed, the workpiece is grasped by a robot hand, and the workpiece is moved relative to the tool, thereby Robots for welding and cutting are known.
With this robot, the welding speed and the cutting speed can be kept constant.

[0003]

In the case of such processing, the control of the position and orientation of the robot is performed according to the teaching data that is taught and input in advance. For this reason,
It is difficult to accurately position the machining point on the machining path when the teaching is not accurate, the temperature changes, the weight change of the workpiece, or the like. The present invention is made to solve the above problems, and an object thereof is to position a machining point on a machining path in a robot that fixes a tool and grips a workpiece with a hand. By making it accurate, the processing accuracy is improved.

[0004]

The structure of the invention for solving the above-mentioned problems is to fix a tool on a tool base, to make a robot hold a work, and to control the position and posture of the robot according to teaching data to make a work. In a robot control device for machining an object, the tool is fixed at a position advanced from the machining point of the tool in the machining path on the workpiece and is arranged at a certain relative position with respect to the tool. A sensor that detects the coordinates of a detection point existing above, and a control unit that corrects the position and orientation based on the teaching data according to the coordinates detected by the sensor and controls so that the processing point exists on the processing path. That is to say.

[0005]

Function The detection point exists at a position advanced from the processing point. That is, the detection point is set in the area through which the processing point will pass. The machining path is detectably formed on the workpiece. For example, when two planar objects are overlapped and welded, the ridge line of the step formed by overlapping the two planar objects is the machining path. This ridge line can be detected as a portion in which the laser output from the sensor swings in a direction perpendicular to the ridge line and the output thereof changes stepwise. With this sensor, the coordinates of the detection point existing on the machining path in the coordinate system fixed to the sensor are calculated. Then, when the machining point is positioned on the predetermined machining path according to the teaching data, this coordinate is considered in consideration of the delay of the machining point with respect to the detection point, and fine adjustment of the positioning of the machining point on the machining path is performed. Done. As a result, the processing point can be accurately positioned on the predetermined processing path, and the processing accuracy can be improved.

[0006]

According to the present invention, the machining path is controlled by controlling the position and orientation of the robot according to the teaching data, and when actually machining, the position of the machining path is detected by the sensor and the position of the machining path is detected. The position and orientation of the robot are controlled by the deviation from the ideal position. Further, since the sensor and the tool are fixed, it is not necessary to attach many wires on the robot side, and a simple and safe system can be configured.

[0007]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 is a mechanism diagram showing the mechanism of a 6-axis articulated robot. 10 is the robot body, and the body 1 is on the floor
A base 12 for fixing 0 is disposed, and a column 13 is fixedly mounted on the base 12, and the column 13 includes a body 14
Is rotatably arranged. The body 14 rotatably supports the upper arm 15, and the upper arm 15 rotatably supports the forearm 16. Body 1
4, the upper arm 15 and the forearm 16 are rotationally driven about axes a, b, and c by servomotors M1, M2, and M3 (see FIG. 3), respectively. This rotation angle is detected by the encoders E1, E2, E3. A wrist 17 is rotatably supported on the tip of the forearm 16 about the d axis, and a hand 18 is rotatably supported on the wrist 17 about the e axis.

Further, the hand 18 is rotatably supported around the f axis. Then, the workpiece W is held by the hand 18. The workpiece W is a combination of two U-shaped objects in cross section, and the ridge line of the stepped portion of the joint portion serves as a machining path, and the machining path is a portion to be welded.
The d-axis, e-axis, and f-axis are servomotors M4, M5, and M6.
Driven by.

A tool stand 19 is erected on the floor,
A holder 30 is fixedly mounted on the tool base 19. The welding torch T and the displacement sensor S are fixed to the holder 30. The welding torch T and the displacement sensor S have a positional relationship as shown in FIG. The displacement sensor S is offset by a predetermined distance delta _X in the direction of the processing path A with respect to the welding torch T.

FIG. 3 is a block diagram showing the electrical construction of the robot attitude control device. Reference numeral 20 is a central processing unit including a microcomputer and the like. The central processing unit 20 includes a memory 25, servo CPUs 22a to 22f for driving servo motors, an operation panel 26 for instructing jog operation, instruction of teaching points, an arc welding machine 23 for welding, An input / output interface 24 for inputting a detection signal from the displacement sensor S is connected. A welding torch T is connected to the arc welding machine 23, and a displacement sensor S is connected to the input / output interface 24. The servo motors M1 to M6 for driving the axes a to f attached to the robot are respectively servo CPs.
It is driven by U22a to 22f.

Each of the servo CPUs 22a to 22f outputs output angle data θ _{1 to} θ ₆ output from the central processing unit 20 and outputs α _{1 to} α _{6 of} encoders E1 to E6 connected to the servo motors M1 to M6. The deviation between the servo motors M1 to M6 is operated at a speed according to the magnitude of the calculated deviation.

The memory 25 stores a program P for operating the robot according to the teaching point data.
An A area and a PDA area for storing teaching point data representing the position and orientation of the robot are provided, and position data and orientation data at a plurality of teaching points are stored in the teaching mode.

Next, the operation will be described. FIG. 4 is a flowchart showing a processing procedure regarding teaching of the CPU 20 used in the apparatus of the embodiment. First, in step 100, a teaching attachment (not shown) is attached to the position and orientation of the tip of the welding torch fixed to the tool base at the center of the robot hand flange, and the operation panel 2
The manual operation in 6 teaches the position matrix T obtained by converting the rotation angle diagram (13) of each drive shaft of the robot as described above.

Next, in step 102, the position and orientation of the flange center of the robot hand at each teaching point on the machining path of the workpiece are determined by the rotation angle diagram of each drive shaft of the robot described above (13). Is taught as the converted position matrix F, and this program ends.

Further, the program shown in FIG. 5 is executed. That is, in step 300, as shown in FIG. 6, a point C (C _X, C _X, whose coordinates are known in the robot coordinate system O-XYZ is shown.
The position of C _Y, C _Z ) is read by the displacement sensor S, and the coordinates (C _x, C _y, C _Z ) of the displacement sensor S in the coordinate system O-xyz are calculated. Then, in the next step 302, the coordinate system O-xyz of the displacement sensor S is calculated from these two coordinate values.
A transformation matrix K for transforming the robot coordinate system into the robot coordinate system O-XYZ is calculated. The transformation matrix K is a matrix of 4 × 4 rows that performs posture transformation and translation of position. The conversion matrix K is calculated from the relationship between the unit vector of the robot coordinate system and the unit vector of the displacement sensor coordinate system and the detection result of the point C described above.

Next, the positioning control in the machining operation by this apparatus will be described. First, referring to FIG.
The coordinate system and coordinate conversion of the robot will be described. O-
The XYZ coordinate system is an orthogonal coordinate system (robot coordinate system) fixed in space. Point P represents the tip of the tool fixed to the tool base, and point Q is the center of the flange of the robot hand that holds the workpiece (hereinafter also simply referred to as the "flange center").
Represents At the tip P of the tool, unit vectors e1, e2, and e3 are fixed to the tool to represent the tool posture of the tip of the tool, as shown in the figure. Also, the flange center Q
Unit vectors a1, a2, and a3 fixed to the center of the flange are taken as shown to represent the posture at. The components of these unit vectors are shown in FIG.
It is defined by equation (6).

Further, the position vectors (the components mean Cartesian coordinates) of the points P and Q are defined by the equations (7) and (8) in FIG. Therefore, the position matrix T at the tip of the tool and the position matrix F at the center of the flange are defined by equations (9) and (10) in FIG. Here, the matrix of 3 rows and 3 columns at the upper left is called an attitude matrix. Further, the transformation matrix M is defined by the equation (11) in FIG. This conversion matrix M associates the position matrix F of the flange center Q with the position matrix T of the tip P of the tool. It can be said that the position and orientation of the tip of the tool are represented by a coordinate system Q-a1a2a3 fixed at the center of the flange.
That is, the direction cosine of the e1 vector with respect to the a1, a2, and a3 vectors is (M ₁₁ , M ₁₂ , M ₁₃ ), those of the e2 vector are (M ₂₁ , M ₂₂ , M ₂₃ ), and the e3 vector has They are (M ₃₁ , M ₃₂ , M ₃₃ ). Also, Q
The coordinate component of the P vector in the coordinate system Q-a1a2a3 is
(R _X, R _Y, R _Z ). Therefore, the relationships of the matrices T, F, and M are given by the equation (12) in FIG.

If the rotation angle of each drive shaft of the robot (in the case of 6 axes) is expressed by the equation (13) in FIG. 14, the robot is placed between the rotation angle (13) and the position matrix F of the flange center. There is a certain fixed relationship that can be converted to each other. Further, since the position matrix T at the tip of the tool and the position matrix F at the center of the flange have the relationship of equation (12) in FIG. 14, after all, the rotation angle (13) of the drive shaft and M and F are They are related to each other and can be converted to each other.

Next, interpolation calculation of the position and orientation of the robot and positioning control will be described. In order to interpolate between the teaching points at the designated interpolation cycle, the CPU 20 executes the flowchart showing the processing procedure regarding interpolation in FIG.
In step 200, the position matrix F of the adjacent teaching points taught in step 102 of FIG. 4 is read. Next, in step 202, from the position matrix T of the tip of the tool taught in step 100 of FIG. 4 and the position matrix F at the teaching point read in step 200, from the above equation (12), The conversion matrix M at the teaching point is calculated.

Now, for example, let two adjacent teaching points be A,
As B, the teaching point A will be described with reference to FIG. 10 and the teaching point B with reference to FIG. 11. The position matrix T of the tip of the tool is expressed by equation (9) in FIG. 13, and the position matrix F _A of the flange center at the teaching point A is (1) in FIG.
From expression (0), it is expressed by expression (14) in FIG.

The transformation matrix M _{A at the} teaching point A is given by (15) from the equation (11) in FIG. Here, from Expression (12), Expression (16) in FIG. 15 is obtained. Therefore, the conversion matrix M _{A at} the teaching point A is calculated in (17) of FIG. Similarly, the transformation matrix M _{B at the} teaching point B is (18) in FIG.
Calculated at, and M at two adjacent teaching points A and B
_A and M _B are obtained.

Between the transformation matrices M _A and M _B , the azimuth and position of the rotation main axis and the rotation angle g are determined by the above-described rotation main axis method.
And the posture conversion matrix S _g between them is _calculated as shown in FIG.
It can be obtained as equation (19). Therefore, the distance D _AB between two adjacent teaching points A and B is D _AB ² = | (D _X ² + D _Y ² +
D _Z ² ) |

Next, in step 204, the workpiece W is
Assuming that the designated machining speed of is v, the required time t for machining the distance D _AB is t = D _AB / v. And
Interpolation is performed between the adjacent teaching points A and B at the designated interpolation cycle. If the interpolation cycle specified here is Δt, then t /
Δt = n, and the rotation angle h for each interpolation point is h = g / n. Therefore, the posture conversion matrix S _{h1 at} the interpolation point C ₁ is
From equation (19), it is given by equation (20) in FIG.

Therefore, the transformation matrix M _C1 of 4 rows and 4 columns at the interpolation point C ₁ is calculated as M _C1 = S _h1 · M _A. Next, the routine proceeds to step 206, where F _{C1 is calculated} from the above equation (12).
= T · M _C1 ⁻¹ is derived and 4 lines 4 at the interpolation point C ₁
A position matrix F _C1 of the flange center of the column is calculated.

Therefore, the position and orientation of the flange center of the designated interpolation cycle are converted from the position matrix F _C1 as the rotation angle of each drive axis of the robot as shown in the rotation angle (13), and the position is converted. The position and orientation of the flange center of the robot hand is calculated as the rotation angle of each drive axis converted from the matrix F _C1 .

Next, in step 208 of FIG. 8, the output of the displacement sensor S is input, and the coordinates (N _x, N _y, N) of the point (detection point) on the machining path A in the displacement sensor coordinate system are input _. N _z )
Is calculated. Then, in step 210, step 20
Using the coordinates (N _x, N _y, N _z ) calculated in 8 and the transformation matrix K, the coordinates (N _X, N
_Y, N _Z ) is calculated (FIG. 9). Next, in step 212, the coordinates (L _X, L _Y, L) of the previous detection point after the position deviation correction (hereinafter referred to as “pre-correction detection point”).
_Z ) and the coordinates (N _X, N _Y, N _Z ) of the detected point this time, the unit direction vector r ₀ of the machining path A is calculated by the equation (23) in FIG.
Is calculated.

Next, in step 214, the coordinates (H _X, H _Y ) of the point (target machining point) on the machining path A at the existing position of the welding torch T (position on the same coordinate as the X coordinate of the welding torch T). _, H _Z ) using the unit direction vector r ₀ and the displacement Δ _X between the welding torch T and the displacement sensor S.
It is calculated by the equation (24).

The target machining point H is a point on the machining path having the same coordinates as the X coordinate of the welding torch T. If there is no machining error, the target machining point H is the coordinates of the tip of the welding torch T. It should match (P _X, P _Y, P _Z ). Therefore, the deviation becomes a positioning deviation. Therefore, the step
At 216, the positioning error E is calculated by the equation (25) in FIG.

Next, in step 218, the position matrix of the flange center calculated in step 206 is translationally corrected by the positioning error E. Next, in step 220, the angle of each axis is calculated from the position matrix F of the flange center corrected in step 218. Next, in step 222, each servo motor is driven based on the angle to control the angle of each axis.

Next, in step 224, the current detection point coordinates (N _X, N _Y, N _Z ) are corrected by the positioning error E and the previous correction detection point coordinates (L _X, L _Y, L _Z ) are corrected. Is stored as Next, in step 226, it is judged whether or not all the interpolation calculation between the two teaching points is completed, and if not completed, the process returns to step 204 and the calculation of the position matrix of the flange center at the next interpolation point and The position deviation is corrected and the positioning control is performed based on the value. If the calculation of all the interpolation points is completed, the process proceeds to step 228, it is determined whether the reading and positioning control of all the teaching points are completed, and if the positioning control is not completed,
In step 200, the interpolation calculation and the positioning control for the next teaching point are executed as described above. or,
In step 228, when the processing for all the taught points is completed, it means that the positioning control for machining is completed, and this program ends.

As described above, according to the present invention, the route during teaching is accurately corrected during machining.
The processing accuracy is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a robot driven by an apparatus of an embodiment and a positional relationship with a tool.

FIG. 2 is an explanatory view showing a positional relationship between a welding torch and a displacement sensor.

FIG. 3 is a block diagram showing an electrical configuration of the apparatus of the embodiment.

FIG. 4 is a flowchart showing a processing procedure of a CPU used in the apparatus of the embodiment when teaching a machining path.

FIG. 5 is a flowchart showing a processing procedure of a CPU for obtaining a conversion matrix between the Sansa coordinate system and the robot coordinate system.

FIG. 6 is an explanatory diagram showing a method of obtaining a conversion matrix between a Sansa coordinate system and a robot coordinate system.

FIG. 7 is a flowchart showing a processing procedure of a CPU during positioning control.

FIG. 8 is a flowchart showing a processing procedure of the CPU at the time of positioning control continued from FIG.

FIG. 9 is an explanatory diagram illustrating a method of calculating a deviation of a machining path.

FIG. 10 is an explanatory diagram showing the relationship between the tip of the tool at the teaching point A, the center of the flange of the robot hand, and the held workpiece.

FIG. 11 is an explanatory diagram showing the relationship between the tip of the tool at the teaching point B, the center of the flange of the robot hand, and the held workpiece.

FIG. 12 is an explanatory diagram showing the positional relationship between the tip of the tool and the center of the flange of the robot hand.

FIG. 13 is an explanatory diagram showing mathematical expressions.

FIG. 14 is an explanatory diagram showing mathematical expressions.

FIG. 15 is an explanatory diagram showing mathematical expressions.

FIG. 16 is an explanatory diagram showing mathematical expressions.

[Explanation of symbols]

 10 ... Robot main body 18 ... Hand 20 ... Central processing unit 25 ... Memory T ... Tool (welding torch) S ... Displacement sensor W ... Workpiece step 208-224 ... Control means

Front page continuation (72) Inventor Ryuji Inada 1-1 Asahi-cho, Kariya city, Aichi Toyota Koki Co., Ltd.

Claims (1)

[Claims] 1. A robot controller for fixing a tool to a tool base, causing a robot to hold a workpiece, and controlling the position and orientation of the robot according to teaching data to machine the workpiece. While being fixed at a position advanced from the machining point by the tool in the machining path on the object,
A sensor arranged at a constant relative position with respect to the tool, for detecting the coordinates of a detection point existing on the machining path, and a position based on the teaching data according to the coordinates detected by the sensor and A robot control device comprising: a control unit that corrects a posture and controls so that the processing point exists on the processing path.