JPH02256481A - Relative distance control method between robot and work and correction data preparing device thereof - Google Patents

Abstract

PURPOSE:To easily prepare correction data by determining a distance when an end effector is separated from a work after the end effector is brought into contact with the surface of the work based on the drive quantity of a robot, and storing the correction data based on the distance and the output signal of a distance sensor. CONSTITUTION:The distance when an end effector T is separated from the surface of a work W after a contact detecting means 222 detects that the end effector T is brought into contact with the surface of the work W is determined based on the drive quantity of a robot. Correction data are stored in the memory 223b in a signal processing circuit 223a based on the distance and the output signal of a distance sensor HS. Correction data can be thereby easily prepared. The distance between the end effector and the surface of the work W is controlled to be kept constant according to the correction data, thus no fine manual adjustment is required for the distance sensor HS or the like.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a mutual distance control method for maintaining the mutual distance between the surface of a workpiece and an end effector of a robot at a predetermined value, and a calibration data creation device for the same. Regarding.

(Prior Art and Its Issues) Automatic cutting robots that use a torch that generates a laser beam, for example, are widely used as robots that work on press-formed sheet metals. In order to perform a cutting operation using such an automatic cutting robot, it is necessary to teach the automatic cutting robot teaching data regarding a virtual cutting line of a workpiece to be worked. When performing automatic cutting work, the torch moves according to this teaching data and operates to draw a three-dimensional smooth cutting line.

However, the surfaces of many identical workpieces do not necessarily have exactly the same unevenness, and the unevenness usually differs from workpiece to workpiece due to causes such as strain caused by pressing. However, as a result, if the distance between the torch and the workpiece surface is not constant, the relationship between the focus of the laser beam and the workpiece surface may shift, making it impossible to cut cleanly. Therefore, when moving the torch according to the teaching data, control may be performed to keep the distance between the torch and the workpiece surface constant.

To perform such control, the torch is provided with a distance sensor that measures the distance to the workpiece, and control is performed to maintain the sensor output, such as voltage, at a predetermined constant value.

(Problem to be Solved by the Invention) However, there are various errors in the sensor output,
This error can be caused by, for example, the heat generated when using a torch, the length of the senna probe wire, changes in the bending state of the workpiece surface, or
It may change due to changes over time in the characteristics of the amplifier that electrically amplifies the sensor output.

Therefore, in order to correct such errors, after manually bringing the torch close to the surface of the workpiece, set the torch at a certain distance from the surface of the workpiece using, for example, a feeler gauge, and then In order to obtain a predetermined sensor output, the sensor output was calibrated by operating a zero adjustment knob provided on an amplifier for the distance sensor.

However, with this conventional method, each time the distance sensor is calibrated, the distance between the torch and the workpiece surface must be manually adjusted to maintain a constant distance. Since adjustments had to be made manually, it took time and effort to calibrate the distance sensor.

(Object of the Invention) This invention was made to solve the above-mentioned problems, and when performing mutual distance control to maintain a constant distance between an end effector such as a torch and a workpiece surface,
It is an object of the present invention to provide a mutual distance control method that can easily calibrate a distance sensor, and a calibration data creation device for the same.

(Means for Solving the Problems) In order to solve the above problems, in the first configuration of the present invention,
In a mutual distance control method for maintaining a mutual distance between the work surface and the end effector at a predetermined reference distance using a distance sensor when controlling the operation of the end effector of the robot on the surface of the work, the following step is provided. has.

(a) Prior to causing the robot to perform the work,
a step of detecting contact of the end effector with the work surface by a contact detection means provided in association with the robot;

(b) moving the end effector so as to increase the distance from the work surface, and determining the distance based on the amount of drive of the robot;

(c) In step (b), storing calibration data representing the relationship between the sensor output signal of the distance sensor and the distance in a storage means.

(d) When the robot performs the work, a reference value of the sensor output signal corresponding to the reference distance is determined according to the calibration data, and the robot is controlled so that the sensor output signal matches the reference value. Steps to do.

Further, in a second configuration of the present invention, with respect to a sensor provided on the end effector side of the robot to detect the distance between the end effector and the workpiece surface, an apparatus for creating calibration data for calibrating the distance sensor. We provide a device equipped with the following means.

(a) Contact detection means is provided in association with the robot and detects contact between the end effector and the workpiece.

(b) Movement control means that is activated when creating the calibration data and moves the end effector in a direction away from the work surface after the end effector and the work surface are brought into contact.

(c) In the movement, after the contact detection means detects the contact between the end effector and the workpiece surface, the movement distance of the end effector is specified based on the drive amount of the robot, and the movement distance is determined based on the drive amount of the robot. Means for generating correlation data indicating a correlation between the travel distance and the level of the output signal by capturing the level of the output signal of the distance sensor at each value.

Then, the calibration data is created according to the correlation data.

(Function) After detecting contact between the work surface and the end effector by the contact detection means, the distance when the end effector is separated from the work surface is determined based on the amount of drive of the robot, and that distance and the distance sensor are calculated. Since the calibration data is recorded based on the output signal, the calibration data can be easily created. Further, since the distance between the end effector and the workpiece surface is controlled to be kept constant according to this calibration data, there is no need to manually make delicate adjustments to the distance sensor or the like.

(Embodiment) A. Overview of the structure of the embodiment FIG. 1 is a schematic perspective view showing the mechanical structure of a Cartesian coordinate type laser cutting robot as an example of a robot to which the present invention is applied. In the same figure, this robot RB is
A motor M1 (not shown) is placed on the base 1 in the X direction (
It has a movable table 2 that is movable in the horizontal direction, and a workpiece (not shown) is placed on this movable table 2. A beam 4 is installed at the top of the column 3 installed vertically on both sides of the base 1.
This beam 4 is provided with a moving column 5 that extends in two directions (vertical directions) in the figure and is movable in the Y direction by a motor M2.

Further, at the lower end of this moving column 5, a motor M4 is provided which moves up and down in two directions by a motor M2. As a result, the arm 6 provided eccentrically from the central axis of the moving column 5 rotates in the θ direction in the figure. Also,
A motor M5 is provided on the side of the lower end of the arm 6, which rotates the laser torch T as an end effector in the φ direction in the figure. Furthermore, a hide sensor H8 (described later) is formed that uses this laser torch T to detect the distance between the laser torch T and the surface of the workpiece W.

A laser beam from a laser oscillation device 7 is applied to the laser torch T through a laser guide vibe 8. Further, the control device 9 has a built-in torch distance control device, a microcomputer, etc., which will be described later, and the operation panel 10 is provided with a keyboard, a display, and the like. Further, the external computer 1 is used for inputting/outputting various data and processing data, and is equipped with a CRT 12, a keyboard 13, and the like.

FIG. 2 is a schematic block diagram of the electrical configuration of the robot RB shown in FIG. 1. In FIG. 2, a microcomputer 21 built into a control device 9 is connected to the following devices via a bus BL.

■The above motor M'=Mc, and the encoders E1 to E5 that detect the rotation angles of these motors M1 to M5 (
(not shown in FIG. 1) Mechanism drive system 23 ■Laser oscillation device 7 ■Operation panel 10 ■External combinator 1 Laser torch T receives a laser beam from laser oscillation device 7, and also The relative distance between the laser torch T and the workpiece W is detected by the torch distance control device 22 using a hide sensor H5 provided at the tip of the laser torch T. Note that this system can also be operated under the control of an upper host system (not shown).

B. Detailed structure of laser torch T FIG. 3 is a partial sectional view showing details of the laser torch T described above. In the figure, the lower part of the cylindrical housing 40 of the laser torch T is a nozzle tip 41 whose inner and outer diameters decrease conically toward a torch hole 43 at its lower end. Nozzle tip 4 at torch hole 43 portion
The outer peripheral portion of No. 1 is a hide sensor Is having a larger planar area in a portion facing the workpiece W. Further, a lens 42 is provided within the housing 40, and the laser beam LB given from the laser oscillation device 7 is focused by the lens 42 and irradiated onto the workpiece W.

The hide sensor H8 is a sensor that detects the difference in the clearance 9 between the workpiece W and the nozzle tip 41 by a change in capacitance when the laser torch T is directed toward the workpiece W. That is, with respect to a preset relative distance between the laser torch T and the workpiece W, when the two approach each other, the capacitance increases, and conversely, when the two move away from each other, the capacitance decreases. Therefore, by electrically insulating the laser torch T and the arm 6 and comparing the capacitance detected by the hide sensor H3 with a predetermined reference value, the actual relative distance between the laser torch T and the workpiece W can be determined. It can be determined whether the distance is smaller or larger than a preset relative distance.

In this embodiment, as will be described later, the torch distance control device 22 controls the operation of the laser torch T so that the relative distance between the laser torch T and the workpiece W is always constant based on the data detected by the hide sensor H3. Control.

C. Structure of Torch Distance Control Device FIG. 4 is a block diagram showing in more detail the structure of a torch distance control device, etc. to which an embodiment of the present invention is applied. In this embodiment, for example, a hide sensor H8 of a robot RB that performs a cutting operation using a laser beam LB will be explained, but as described above, such a hide sensor H5 makes an important contribution to proper focus control of the laser beam LB. It is a component that fulfills the In the figure, the encoders E, (1-1 to 5) of the mechanism drive system 23 include a speed detector TG realized by, for example, a tacho generator, and a phase detector PG realized by, for example, a pulse generator. configured. The mechanism drive system 23 also includes a speed controller 1 that feeds back the speed signal α1 from the speed detector TG, and a position controller 2 that feeds back the position signal α1 from the phase detector PG. In addition,
In addition to being given a position correction signal Δα1 (described later) from the torch distance control device 22, the mechanism drive system 23 is provided with:
A position setting signal α1o is provided from the microcomputer 21.

On the other hand, the torch distance control device 22 includes a sensor amplifier 221 connected to the hide sensor H8 at the tip of the laser torch T to measure the capacitance between the hide sensor H3 and the work W; A contact detection circuit 222 for detecting that surfaces are in contact, a main controller 223, and a coordinate conversion circuit 224 for converting a distance correction signal ΔM (described later) given from the main controller 223 into a position correction signal Δα1. It is equipped with

＼ The sensor amplifier 221 outputs a sensor output signal V depending on the capacitance between the hide sensor H3 and the workpiece W, for example, as an analog voltage.
is input to the signal processing circuit 223a in the main controller 223. This signal processing circuit 223a has a memory 223b that stores calibration data, as will be described later.

On the other hand, the contact detection circuit 222 is connected to the hide sensor H5 and the workpiece W, and notifies the user that the laser torch T and the workpiece W have come into contact when the resistance value between them becomes almost zero. A contact detection signal S is output.

This contact detection signal S is given to the main controller 223. Note that the contact detection circuit 45 may have other configurations such as a configuration that detects that the capacitance detected by the hide sensor s exceeds a predetermined threshold value.

FIG. 5 is a flowchart illustrating the procedure for calibrating the torch distance control device 22. In the figure, step a1
Now, the operator uses the operation panel 10 to move the laser torch T to the vicinity of the surface of the workpiece W.

At this time, the surface of the work W is selected to be as flat as possible, and the attitude of the laser torch T is adjusted so that the laser torch T is oriented perpendicularly to the surface of the work W.

In step a2, the operator inputs a signal to start the calibration operation on the operation panel 10. From now on, the calibration operation proceeds automatically according to the work program on robot RB. When this start signal is input, the laser torch T
automatically and slowly descends toward the workpiece W (step a3).

In step a4, the contact detection circuit 222 detects the laser torch T.
It is determined whether or not contact with the workpiece W is detected. If there is no contact, the process returns to step a3 and the laser torch T is further lowered.

If the judgment in step a4 is affirmative, the process moves to step a5, where the microcomputer 21 transfers information to the main controller 223.
A distance signal S is applied to the laser beam T, and the laser torch T rises by a distance 9 corresponding to the distance signal S and then stops.

Referring to FIG. 4, when the distance signal S is given to the signal processing circuit 223a, the distance correction signal Δ9 for moving the laser torch T in two directions by the distance 11 specified by the distance signal S is sent to the signal processing circuit 223a. is output from.

This distance correction signal Δt is processed in the coordinate conversion circuit 224.
Each coordinate value α of the robot coordinate system is converted into a position correction signal Δα1 indicating the correction amount of each coordinate value α (1-1 to 5°, specifically, each coordinate value of x, y, z, θ, and φ). . For example, when the attitude of the laser torch T is set vertically in advance, the position correction signal Δα1 is a drive amount instruction signal for pulling up the laser torch T by a distance 11 in the two directions shown in FIG. This is a signal given to the servo system of motor M8 of 23.

In step a5, set the distance between the laser torch T and the surface of the workpiece W to the initial setting value! 11 is completed, in step a6, the sensor output signal V of the sensor amplifier 221 at this time is transferred to the signal processing circuit 223a.
Read with The level of the sensor output signal V 1 is stored in the memory 223b in the signal processing circuit 223a together with the driving distance signal SR given from the microcomputer 21.

When the process for the first set distance 9□ is completed, the process returns from step a7 to step a5, and the same process is repeated for the next set distance 1□.

In this way, when steps a5 and 86 are repeated for all predetermined set distances, data indicating the correlation between the distance signal SR and the sensor output signal V as shown in FIG. 6 is stored in the memory 223b as correlation data. is stored as. In this example, a sensor III IT output signal vsl"""s7 is obtained for each distance signal S-8.

In step a8, these signal values S-817, vsl
Based on the correlation data of ~vs7, the relationship between the distance signal Sn and the sensor output signal vs is approximated using approximate expressions S, -G(Vs). FIG. 6 shows a curve approximated by the approximation formula 5R-G(Vs). The signal processing circuit 223a stores the approximate expression 〇(V) obtained in this way as calibration data. Note that this approximation expression may be, for example, a polynomial expression, or it may be a line-interpolation line between points P-P7 in FIG.

As described above, the calibration work of the torch distance control device 22 is completed.

Note that, as shown in FIG. 6, a predetermined distance signal S,! If the level of the sensor output signal V corresponding to the distance signal S deviates from the permissible range ΔV, at least one of the hide sensor H8 or the sensor amplifier 221 is set. It is also possible to determine that either one is abnormal. That is, if the calibration is performed as described above, an abnormality can be detected when calibrating the hide sensor H3, which has the advantage of improving usability.

E. When the creation of the torch distance control calibration data during cutting is completed, the robot is actually operated to cut the workpiece W. During such robot operation, a distance signal S1 corresponding to the reference distance p specified by the operator is input from the microcomputer 21 to the signal processing circuit 223a. For example, the distance signal S 2 shown in FIG. 6 is given as a signal corresponding to a reference distance signal S 2 corresponding to a reference distance of 1° (for example, 2 mm).

10 On the other hand, the actual distance between the laser torch T and workpiece W at this time! The sensor output signal V according to the sensor amplifier 2
21 to the signal processing circuit 223a. The signal processing circuit 223a uses the approximate expression S, ! obtained as calibration data.
−G(Vs) to convert the sensor output signal V to the distance signal S
j! Convert to

Then, as shown in the formula below, the microcomputer 21
Distance signal SR and reference distance signal S given from
The difference correction Δ9 between the distance and the distance correction signal is output as a distance correction signal.

Δj! "5R-8J!O-10 Then, the distance correction signal Δg is converted into a position correction signal Δα1 in the robot coordinate system by the coordinate conversion circuit 224, and is given to the mechanism control system 23.

As you can see from the above explanation, the actual distance! When becomes equal to the reference distance fIo, the distance correction signal Δt becomes zero. Therefore, the laser torch T is controlled so that it is always kept at a constant distance fIo from the workpiece W.

In addition, if the calibration data is calibrated using the approximate formula G(V) as described above, the working reference distance 1° of the laser torch T from the workpiece W can be changed from, for example, the above-mentioned 2 mm to another value. Even in this case, an appropriate reference distance signal S1 corresponding to the new reference distance can be obtained based on the approximation formula (V).

In other words, since there is no need to perform a calibration operation every time the setting of the reference distance is changed, there is an advantage that the calibration procedure can be significantly improved.

Note that the hide sensor H8 is not limited to the capacitance detection type of this embodiment, but may use a magnetic distance measuring means or an optical distance measuring means.

(Effects of the Invention) As described above, according to the present invention, after the contact detection means detects contact between the surface of the workpiece and the end effector, the distance when the end effector is separated from the workpiece is calculated by the amount of robot drive. Calibration data is stored based on the distance and the sensor output signal of the distance sensor, so calibration data can be easily created.Furthermore, the distance between the end effector and the workpiece surface can be calculated based on this calibration data. Since it is controlled so as to keep it constant, there is no need to manually adjust the distance sensor, etc., and there is an effect that the distance sensor can be easily calibrated.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing the mechanical configuration of robot RB to which the present invention is applied; FIG. 2 is a block diagram showing the electrical configuration of robot RB shown in FIG. 1; FIG. FIG. 4 is a block diagram showing the electrical configuration of a torch distance control device, etc.; FIG. 5 is a flowchart illustrating an embodiment of the present invention; FIG. FIG. 2 is a diagram showing the contents of calibration data. RB...Robot, 9...Control device, 10...Operation panel, 11.
...External computer, 22...Torch distance control circuit, 221...Sensor amplifier, 222...Contact detection circuit, 223...Main controller, 223a...Signal processing circuit, 224...Coordinate transformation Circuit, T...laser laser torch, W...work, HS...hide sensor

Claims (2)

[Claims] (1) A mutual position control method that uses a distance sensor to maintain a mutual distance between the workpiece surface and the end effector at a predetermined reference distance when controlling the operation of the end effector of the robot on the surface of the workpiece. (a) Prior to causing the robot to perform the work,
After detecting contact of the end effector with the work surface by a contact detection means provided in association with the robot, (b) moving the end effector so as to increase the distance from the work surface; The distance is determined based on the amount of drive of the robot, and (c) the step (b)
), storing calibration data representing the relationship between the sensor output signal of the distance sensor and the distance in a storage means, and (d) when the robot performs the work,
A mutual distance between a robot and a workpiece, characterized in that a reference value of the sensor output signal corresponding to the reference distance is determined according to the calibration data, and the robot is controlled so that the sensor output signal matches the reference value. Control method. (2) A device for creating calibration data for calibrating a distance sensor for a sensor provided on the end effector side of a robot to detect the distance between the end effector and the workpiece surface, comprising: (b) contact detection means, which is provided in association with the robot and detects contact between the end effector and the workpiece; (b) contact detection means is activated when creating the calibration data and causes the end effector to come into contact with the surface of the workpiece; (c) during the movement, the contact detection means detects contact between the end effector and the work surface; The subsequent moving distance of the end effector is specified based on the drive amount of the robot, and the level of the output signal of the distance sensor at each value of the moving distance is taken in to determine the distance between the moving distance and the output signal. A calibration data creation device, comprising means for generating correlation data showing correlation with a level, wherein the calibration data is created according to the correlation data.