JPH0323315B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement for facilitating manual operation of a playback type industrial robot that has an operation mode that allows manual position and attitude control via an operation panel. .

Industrial robots are used for welding, cutting, and various other tasks, and playback type industrial robots have a manual mode in which the end effector can be moved manually and its posture can be set. In many cases, the end effector is moved to a desired teaching point by controlling each axis of the robot by operating the robot, and its position and orientation data is captured.

These robots come in rectangular coordinate types, cylindrical coordinate types, articulated types, etc. depending on the purpose and usage mentioned above, and the position and posture are controlled using each coordinate system, but in manual mode. When operating the end effector, a unique orthogonal coordinate is set for the end effector, and a switch is provided to move the end effector in the direction of the coordinate axis, thereby making it easier to move the end effector in the direction of the coordinate axis.
It was proposed in Publication No. 139810 and is widely used.

This is done because in the case of manual operation, it is often more convenient to be able to move the end effector in its longitudinal axis and two directions perpendicular to it, rather than moving it in each axis direction of the robot's coordinate system. It is. However, even if it is possible to operate in this way, it is generally necessary to operate in each of the three axes, and it is not only difficult to operate each of the three axes at the same time, but also difficult to operate each axis individually. It's surprisingly troublesome. Therefore, it would be better to reduce the number of axes to be operated as much as possible, but for example, during teaching, the relevant teaching points are on straight lines, curves, planes, curved surfaces, etc. formed by the workpiece, so it is necessary to connect the end effector and the workpiece. distance,
In particular, if it can be operated while maintaining a constant distance in the front-rear axis direction, the number of axes to be operated can be reduced to two or less, making the operation much easier. In addition, as a technology to maintain a constant distance between the robot and the workpiece, a distance sensor is installed to detect the distance between the robot and the target object and is activated during teaching.Accurate teaching is achieved by maintaining the distance to the target object. In addition, Japanese Patent Application Laid-open No. 127683/1983 discloses a robot that works while accurately maintaining the distance to a target by acting during playback, but it is difficult to perform work performed by a robot on a moving target. It is intended to be accurate, and
It does not facilitate manual movement of the end effector during teaching or the like.

This invention focuses on these points, and has a manual mode that allows position and orientation control using an operating means, and a system for moving the end effector in the direction of the coordinate axes of a rectangular coordinate system set in the end effector. In a playback type industrial robot having an operating means, the operating means is an operating means for a coordinate axis other than a specific axis of a rectangular coordinate system set in an end effector. Further, distance setting means for setting a desired distance value between the end effector and the workpiece, and distance measuring means for measuring the distance between the end effector and the workpiece are provided. Furthermore, means for determining the difference between the output of the distance setting means and the output of the distance measuring means and decomposing the difference into each axis component of the robot's coordinate system, and means for commanding each axis component to the driving means of each control axis. and is provided. The most common embodiment is one in which one particular axis is the longitudinal axis of the end effector.

An embodiment of this invention will be described in detail below with reference to the drawings. This example is an articulated robot that uses a welding torch as the end effector.
This invention is not limited to this embodiment.

1 is an industrial robot, and in this example,
As shown in the figure, it is a multi _{-articulated robot with five rotational degrees of freedom α1 to α5 .} The robot 1 is equipped with an MIG welding torch 2 as an end effector.
3 is a conduit tube that guides the consumable electrode TW of the torch 2.

4 is a known welding power supply device. The device 4 includes a spool 4a that winds up the consumable electrode TW of the torch 2, and a welding power source 4 between the electrode TW and the workpiece WK.
b.

Reference numeral 5 denotes a known computer as a main part of the control device of this embodiment. Computer 5 has
Including CPU and memory.

A power supply 4b is connected to the bus line B of the computer 5.

The bus line B is further connected to a servo system _Sα1 for the _α1 axis of the robot R. α ₁ for servo system Sα ₁
The shaft power Mα ₁ and the encoder that outputs its position information
Contains _Eα1 . In addition, the bus line B includes an α _2- axis servo system Sα ₂ , an α _3- axis servo system Sα ₃ , and
An α ₄ -axis servo system Sα ₄ and an α ₅ -axis servo system Sα ₅ are connected.

RE is a remote control panel that forms part of the control device and serves as a control panel, and is equipped with a group of manually operated snap switches SW. Then, by tilting the snap switch sticks for each of the X, Y, Z, φ, and θ control axes (orthogonal coordinate axes for control fixed to the base 1a of the robot 1) from the neutral position shown in the figure to the "U" side, the In the direction of increasing control axis position information,
The end effector is configured so that when it is pushed to the "D" side, the end effector is moved in the opposite direction. It is assumed that the control axes φ and θ represent a turning angle and an attitude angle with respect to the orthogonal coordinate axes, respectively. These configurations require an algorithm for coordinate transformation by the computer 5 between the multi-joint system of the mechanism and the orthogonal coordinate system of the control. However, since the details are well known, I will not discuss them in detail.

The operation panel RE is also provided with a speed command rotary switch SV in auto mode. A mode changeover switch SM is also provided, and is configured to switch between manual mode M, test mode TE, and auto mode A. SE is a selection switch, and by switching it upward in the figure and operating the up-down switch SU, welding condition number W is displayed and selected.
Furthermore, by setting switch SE to the left as shown in the figure and operating switch SU, each mode is selected and displayed as either linear interpolation "L" or circular interpolation "C". There is. Furthermore, the operation panel RE is equipped with a start switch ST. The function of the switch ST will be explained in detail in the explanation of the operation described later.

Furthermore, the operation panel RE is provided with various switches that are characteristic of the configuration of this invention. Let's discuss it in detail below.

First, SS is the sensing mode setting switch, and this switch SS is turned from OFF (state shown) to ON.
The sensing mode can be determined by setting the sensing distance (described later) via .

It also has the same configuration as the switch group SW. A manually operated snap switch group SWT in sensing mode is provided. The switch SWT is configured as a switch for manually operating the torch 2 in the local orthogonal control axes Tx and Ty with respect to the T _{and Z} axes of the axis T of the torch 2, as shown.

Each of these switches is also connected to bus line B.

Furthermore, the sensor SN having a configuration unique to this invention will be described.

The torch 2 is assumed to have a distal end 2b of a base 2a which can be attached and detached by, for example, screw means. Then, remove the tip 2a and prepare a separate sensor.
Wear the SN. The details of one embodiment of this sensor SN are as shown in FIG. 2, and the base end of the main body 6 can be attached to and detached from the tip of the base 2a of the torch 2 with a screw 6a. A stylus 6b is fitted into the tip of the main body 6 so that it can move forward and backward, and is urged forward (downward in the figure) by a spring 6c. Stylus 6b
A linear potentiometer 6d is configured at the base of the stylus 6b, and outputs analog information regarding the movement of the stylus 6b. Then, when this sensor SN is attached and the protrusion length of the stylus 6b is , the stylus 6
It is assumed that the tip of b coincides with the operating point P of the torch 2. Furthermore, the local coordinate Tz fixed to the torch 2 as described above in the direction of the axis T of the torch 2, and the two directions perpendicular thereto and mutually perpendicular to the local coordinate Tz are local coordinates Tx and Ty.

As shown, the workpiece WK has a horizontal fillet welding line WL, and welding is to be performed from points P ₁ to P ₂ on this welding line WL.

For this purpose, first, teaching of the user program is executed. In the following explanation, the third
See also figure.

The operator first operates Switch SM to set manual mode. Normally it would be a switch
When one of the SWs is operated, the computer 5 reads each switch on the operation panel RE (processing PR ₁ ),
The position and orientation of the torch 2 are controlled along the X-system control axis (processes PR ₃ to PR ₅ ). First, the operating point P in front of the torch 2 is located at the point _P1 , and its attitude (Euler angle, that is, φ and θ) is determined as appropriate. In this case, if the torch 2 is taught at a position too close to the workpiece W, the protrusion length of the consumable electrode TW during welding (so-called extension length) becomes short, and the welding current becomes excessive. On the other hand, if the torch 2 is taught at a position that is too far from the workpiece W, the welding current during welding will be too low.
In both cases, the welding results are not interesting. Therefore, the operator must pay close attention to the positioning of the torch 2 in the longitudinal axis T direction. In that case,
It is understood that it is difficult to operate only by operating the switch SW.

Therefore, in this embodiment of the invention, the operator first operates the switch SS to turn it on, enter the sensing mode, and set the dimension l.

Then, the computer 5 determines the swelling (processes
PR ₂ ), first, so that the dimension of sensor SN is l,
Control the position of Tz (processing PR ₆ ).

Expressing this as a formula, Tz=K(l-f(L))
becomes. Here, f(L) is the amount detected by sensor SN, and K is a constant.

In other words, depending on whether the output of the sensor SN is larger or smaller than the value corresponding to the set dimension l, if it is large, the torch 2 is moved forward in the Tz direction (towards point P), and if it is small, the torch 2 is moved in the opposite direction. . That is, the computer 5 controls the rotation angle of each of the control axes α ₁ to α ₅ so that the output of the sensor SN becomes a value corresponding to the set dimension l. Also, the operator can switch
When the SWT is operated, the computer 5 reads this (processing PR ₁ and PR ₂ ), and controls the torch 2 while keeping the set dimension l constant as described above.
Position control in Tx direction or Ty direction.

In other words, if the current position information is ⁿ and the position command information after time (command issuing interval time) △t is ⁿ⁺¹ , then ⁿ⁺¹ = ⁿ + △Tx △Ty △Tz where △Tx, ΔTy, ΔTz, and ΔTz are distances by which the torch 2 should be moved in the directions of the axes Tx, Ty, and Tz during Δt. or coordinate system Tx, Ty, Tz
It is a transformation matrix from to the absolute coordinate system, and = cosφ −sinφ sinφ cosφ 1 cosθ sinθ 1 −sin cosθ.

At this time, if you are not operating the switch SWT but operating the switches φ and θ among the switch SWs, ⁿ⁺¹ = ⁿ + △ where △ is the absolute coordinate system due to the operation of the switch SWs φ and θ. This is the change in .

In this way, ⁿ⁺¹ is calculated and found (processing PR ₆ ), and then coordinates are transformed from this ⁿ⁺¹ value to obtain command values for each mechanical control axis α ₁ to α ₅ (processing
_PR4 ). The details of this coordinate transformation are well known from, for example, Japanese Unexamined Patent Publication No. 49-50376, and therefore will not be described in detail.

Then, these command values are output (processing PR ₅ ).

Furthermore, as time Δt elapses (processing PR ₇ ), it is determined whether the user program for control is the final one (processing PR ₈ ), and if not, the process returns to processing PR ₁ .

In addition to the above-mentioned embodiments, this invention can also be modified as described below.

(a) When the sensor SN is of a contact type as in this embodiment, its output means may be other means than a potentiometer, such as a differential transformer. Furthermore, the sensor SN may be of a non-contact type, for example, a known electromagnetic type or an optical type.

(b) The sensor SN is not attached to or replaced with the end effector as in the previous embodiment, but is installed symmetrically with the end effector with respect to the α ₅ axis, for example, and is installed integrally with the _end effector.
The end effector and the sensor may be selectively operated by rotating the shaft. (For example, the method disclosed in Japanese Unexamined Patent Publication No. 48-24943.) (c) The mechanical structure of the robot (especially up to the wrist) is not limited to an articulated robot, but may be any other known structure. .

(d) The end effector may be a known cutting torch, gripping tool, painting gun, etc. other than a welding torch.

(e) It is also possible to replace each component with equivalents.

Since the present invention is as described above, it can produce the following unique and remarkable effects.

(A) In a playback type industrial robot that can be controlled in manual mode and is equipped with an operating means to position the end effector in the direction of the coordinate axes of a local rectangular coordinate system set on the end effector, When operating with this operating means, it is only necessary to operate in the directions of two or less axes, making the operation extremely easy and convenient for manual mode operation during teaching and the like. This effect is particularly remarkable in a robot equipped with an end effector such as a cutting torch that is positioned perpendicular to the workpiece.

(B) The configuration is simple, and if a computer is used as the control device in addition to the sensor, it can be implemented by simply adding software.

[Brief explanation of the drawing]

The drawings all show one embodiment of this invention, and the first embodiment is shown in the drawings.
The figures are an overall perspective view and a block diagram, FIG. 2 is a partially enlarged vertical sectional view, and FIG. 3 is a flowchart. 1... Industrial robot, 2... Welding torch (end effector), 5... Computer (control device),
WK...workpiece, RE...control panel, Tx, Ty, Tz...local rectangular coordinate system, SN...distance sensor, SWT...switch (operating means), PR ₆ ...processing (means to make the distance constant).

Claims (1)

[Scope of Claims] 1. A playback type industrial robot having a manual mode and an operating means for moving the end effector in the direction of the coordinate axes of a rectangular coordinate system set in the end effector, comprising: An operation means for moving the end effector in the direction of the coordinate axes of the system is provided for the coordinate axes of the orthogonal coordinate system except for one specific axis, and sets a desired distance value between the end effector and the workpiece. A distance setting means, a distance measuring means for measuring the distance between the end effector and the workpiece, a difference in the outputs of the distance setting means and the distance measuring means, and this difference is calculated for each axis of the coordinate system of the industrial robot. The industrial robot comprises: an output difference decomposition means for decomposing into components; and a command means for commanding the respective axis components to the driving means for the respective axes. 2. The industrial robot according to claim 1, wherein the specific one axis is a longitudinal axis of the end effector.