JPH01257593A - Method for correcting shifting of center of robot - Google Patents

Abstract

PURPOSE:To eliminate the trouble of calculating the offset amount and to adjust a working point of a working tool by bringing a contact shoe of the working tool into contact with a specified jig, and computing an error between a working point of the working tool and a reference point in control as an offset amount according to data on the contact position. CONSTITUTION:A welding wire (a kind of contact shoe) of a welding torch 8, which is a working tool fitted to a robot, is brought into contact with a jig 9 having a conductive plate disposed within the operating range of a robot. The position data of a robot at the time of detecting the above contact is stored in a storage portion 12, and a difference between the position data on the preceding contact position and this time position data is calculated by an arithmetic portion 11, to compute an error between the position of the forward end 8a of a welding wire and a reference point in control. The error is stored as an offset amount, and the position of the forward end of the welding wire is shifted in the direction of absorbing the offset amount to align the forward end position of the welding wire with the reference point in control, so that shifting of bead after a welding work is reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a misalignment correction method for correcting an error between a work point and a reference point in a robot that works with a work tool attached to the shaft end, and particularly relates to a method for correcting misalignment of a welding torch. This invention relates to a method for automatically correcting errors between work points and reference points, including wire bending.

[Conventional technology]

As a conventional technique of this type, there is a technique disclosed in Japanese Patent Application Laid-Open No. 62-43711.

This conventional technology uses the deformation or conversion of a welding torch as a work tool attached to the robot's wrist.
The relative position between the tip of the wire as a working point and the reference point may change, making it impossible to perform accurate position control. Therefore, the method described below is used to eliminate positional deviation. In other words, if a shift occurs in the relative position between one work point and the reference point due to deformation or replacement of the welding torch, the robot is operated manually and the work point, i.e., the tip of the wire, is positioned at an arbitrary fixed point. And each axis rg of the robot at that time! storing positional data on the moving parts, then changing the posture of the welding torch by manual operation to position its tip at the fixed point, and storing positional data on each driving part of the robot at that time,
By calculating the position and direction between the reference point and the working point, that is, the tip of the wire, from each of the stored position data, the working point can be controlled accurately.

[Problem to be solved by the invention]

-I:, In order to calculate the amount of deviation between the working point of a work tool and the reference point that is actually the object of control, the Joto technique first attaches the working point, that is, the wire tip of the torch, to an arbitrary fixed point. Guide and teach. Next, the posture of 1--chi is changed and the tip of the wire is similarly guided to the fixed point of the script for teaching. This operation is all performed manually. This thing is
This is a serious problem as a method for correcting misalignment of robots used as automatic machines.

In other words, white! 11! During rotation 1, if the torch interferes with the jig due to an error in the operation of the surrounding jig and the torch is deformed, or
When changing the welding wire, if there is a difference in the bending of the wire and a large positional shift occurs in the wire tip position, the conventional technology first shifts from automatic operation to the teaching state and performs the above series of operations manually. The purpose of the present invention is to solve the above-mentioned problems of the prior art by improving the wire tip, that is, the working point, and the control standards due to bending of the wire, deformation of the torch, etc. Eliminate the hassle of calculating the positional deviation of points and shorten the adjustment time.

It's there to provide.

[Means to solve the problem]

The present invention achieves the above object through the following steps.

(1) A contact is provided within the operating range of the robot on a jig consisting of three conductive flat plates and on a part of one work tool.

For example, if the work tool is a welding torch, the contact may be a welding wire, and the jig only needs to be fixed within the operating range, whether it is fixed to the robot fixed part or to peripheral equipment. You can leave it there.

(2) It has a step of applying voltage between the jig described in (1) and the contact.

(3) Move the robot in a preset direction. Setting of this movement direction is performed by a teaching device included in the robot control device.

(4) According to item (3), there is a step of operating the robot and detecting the jig and the contact.

(5) It has a step of storing the robot position data when the contact described in (4) is detected.

(6) Perform the contact position procedure from the operations in (3) to (6) sequentially, calculate the difference between the position data of the previous contact position and the current contact position, and calculate the working point of the work tool and the control It has a process of calculating the error of the reference point.

(7) It has a step of storing the error in item (6) as an offset amount. This offset amount is a correction amount for correcting the error between the working point of the power tool and the control reference point in the conventional misalignment correction method.

(8) It has a step of shifting the working point of the power tool in a direction that absorbs the offset amount in item (7).

According to (1) to (8) above, the working point of one working tool and the reference point for control are made to coincide based on the offset ship.

In the present invention, as described above, the error between the working point of the power tool and the control reference point is calculated as an offset amount, and the working point of the power tool is shifted in a direction that absorbs the offset amount. The control point is set to -i statement.

The calculation means for calculating the offset amount is 3.
The contact of one work tool is brought into contact with a jig having a flat plate, the robot position data of the contact position is stored, the difference between the previous position data and the current position data is calculated, and an offset is calculated.

This contact operation is set in advance by the teaching device included in the robot control device, and when it is actually operated to calculate the offset amount, it is automatically performed at the start of the operation, so the work point of the work tool and Eliminates the trouble of calculating the error in the control reference point, that is, the offset amount,
Adjustment time can be shortened.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the robot is articulated with six degrees of freedom and has robot drive units corresponding to 1.2.3.4.5.6. θl, 02°o3, 04. 05,
06 represents position data (rotation angle) in each drive unit. 7 represents a welding torch fixture, and 8 represents a welding torch. 7 is fixed to the shaft end of the robot 1, and the torch tip Pa is controlled by the interlocking of each driving section.

Conventionally, when performing welding work, as shown in FIG.
Set the control reference point Q at the 0 mm point, measure or calculate the relative position error between the reference point Q and the torch tip Pa as the working point by some method, store it as an offset amount, and calculate the error amount of the reference point Q. The torch tip Pa is corrected and controlled as follows.

The reference point Q is the position data of each axis 01, θ2, θ3.04
, θ5.06, and the position vector Q of the reference point Q
is expressed by a linear equation.

Q=Fa (θ1, 82. θ3. θ4. θ5゜θ
6) (1) Furthermore, the position vector of the torch tip Pa with respect to the reference point Q is Q Pa, and this becomes offset information. Generally, the amount of offset is three-dimensional information, and assuming that it is an offset vector S (Sx, Sy, Sz), the position vector R of the torch tip Pa is expressed by the following equation.

R=Fb (θ1.θ2.θ3.θ4. 05°θ6
．． S) (2) For the offset vector S, define an arbitrary fixed point in three-dimensional space, teach the robot multiple postures at one point, obtain the required number of equations, and solve for the vector S to obtain the offset information. Desired.

Such a robot has three conductive flat plates within its operating range and a conductive contact as part of the working tool. The jig 9 is composed of three iron plates as shown in FIG. 3, and is fixed to a fixed part of the robot. The jig and the robot fixing part are positioned by pins 16 and grooves 17, and fixed by bolts 18, so that they can be attached and detached. The jig may be composed of three electrically conductive flat plates, and may be fixed to the work table.If the work to be performed is welding, the work tool is:

It becomes a welding torch and the contact is the torch tip ie.

It becomes the tip of the wire, so there is no need to add a contact.

It has means for applying voltage between the flat plate and the contact.

A voltage is applied between the jig '9 and the wire tip 8-a.

This voltage application is performed by the voltage application circuit of the calculation unit 11 as a series of operations for detecting the contact position between the jig 9 and the wire tip 8-a, which will be described later. This is done by opening/closing instructions.

It has a means to move the robot in a preset direction.

The robot is manually operated by the teaching device included in the robot control device, and as shown in FIG.
The wire tip 8-a is taught in the order of 1-+PO-)P2-+PO-)P3-)PL.

Kokoni, PO, PL, P2. P3 position vector RO,
R1, R2, and R3 are each represented by the following formula.

RO=Fb (θ01. θ02. θ03. θ
04゜θ05,006,5) R1=Fb (θ11.f712. θ13.θ1
4°θ15. θ16,5) R2=Fb (θ21.022,023.O2
4°O25, f326,5) R3=Fb (θ31.032.fl133.
O34°θ35. θ36. S) Here, 011 to θ16 (i=o to 3) are each Ri
It represents the position data of each axis when determining (i=o~3).

It has means for detecting contact between the jig and the contactor by moving the jig in the operating direction determined by the above teaching.

Using the above teaching points, the robot moves in the first order,
Detects the contact position between the jig and the contact.

This is executed automatically as a series of operations.

According to FIG. 5, (1) The robot is moved in the POP1 direction and the contact position between the jig and the contactor is detected.

■When execution starts, the voltage application circuit between the jig and the contactor is closed.

■The robot's movement direction P is determined by the first teaching point.

Calculate Pl and operate.

■Detects that current has flowed between the jig and the contact, establishes contact between the jig and the contact, opens the voltage application circuit, and stops the robot.

(2) Store position data at the time of contact as position data to be described later.

②Determine the direction of robot movement based on the first-term teaching position data, and make the robot move up to Po.

-H (2) Move the robot in the POP1 direction and detect the contact position between the jig and the contact.

Similarly to (1), the voltage application circuit is closed when execution starts,
The jig and the contactor are brought into contact by current detection, and the position data is stored. After that, operate up to PO.

(3) Move the robot in the POP3 direction and detect the contact position between the jig and the contact.

(1) Similarly to (2), one position data is stored as contact between the jig and the contactor by current detection. After that, operate until PO.

It has means for storing position data of the contact position between the jig and the contact.

The position data at the time when the contact is detected by current detection is stored as the following position data.

The contact positions when moving in the downward direction of POO12Στ are pH, Pl2. Pl3 and its position vector as R11, R12°R13, then R11=Fb (θ111.0112.O113
゜θ114. θ115. θ116,5) R12=Fb (θ121.θ122.θ123°θ
124. θ125. θ126.5) R13=F”6(θ 131 , θ 132 ,
θ 133.

θ134, 111135. θ136. S). Here, 01J1~θ1j6 (j=1~6) is Rlj
The position data of each axis when determining (j=1 to 3) is shown.

A series of steps of detecting the contact between the jig and the contactor and storing the position data are performed in sequence, and the difference between the previous position data and the current position data is calculated to determine the working point of the work tool and the control standard. It has a means to calculate the point error.

A series of procedures for detecting contact between the jig and the contact and storing the position data are sequentially executed according to a previously taught sequence. This will be explained with reference to FIG.

(1) Install a welding torch as a work tool. This welding torch is attached to the final shaft end of the robot via a torch attachment. Any mounting method may be used.

(2) Measure the error or offset between the working point of the work tool, that is, the wire tip of the welding torch, and the control reference point, or use a measuring tool.

As shown in the prior art, it is calculated and determined by teaching three robot postures in which the tip of the wire indicates a fixed point in space. The offset is preferably a value that includes mechanical errors. The offset value is stored as an offset amount S1.

(3) Teach welding work to the target workpiece.

(4) Teaching and storing the movement direction for detecting the contact position (PO→P1→PO→P2→PO-+P3)
I do.

(5) Detect the first contact position, calculate the amount of each contact,
Remember. In addition, at this time, R11 and R12 degrees are obtained.

(6) Welding work is performed automatically.

(7) Detecting that the tip of the torch has shifted due to replacement of the torch or interference between the torch and the workpiece.

(8) When the detection occurs, the second contact position is detected, and the second contact position R21a R23 is expressed by the following equation.

R2j=Fb(θ2j1.θ2j2,02,33,θ2
j4. θ2j5. θ2j6,5L) (j1-3) The detection operation at this time is performed in the same direction as the first detection operation.

(9) The first contact position R11, R12, R1 degree difference vector is generally expressed by the following equation, and thereby a new offset amount S2 can be calculated.

The relationship between each vector is shown in FIG.

It has means for storing the offset amount.

The offset ff1s2 calculated from the differences Veg1 to 1 is stored as a new offset amount. Offset amount S
2 may be stored in the memory stored in Sl.

It has means for shifting the working point of the power tool in a direction that absorbs the amount of offset.

The offset amount is a new correction amount for correcting the deviation between the work point of the work tool and the control base or point, and the position vector of the torch tip is rewritten as the following equation,
It becomes possible to shift the working point of the power tool without changing the position data of each axis.

That is, the second contact position is determined by the position data of the first contact position and the offset amount S2 as follows: R2j=Fb (θ1j1.θ1j2.flllj3
゜θ1j4. θ1j5. θ1j6. S2).

In general, the position vector R2 is R2=Fb (θ11.
θ12. θ13. θ14°θ15. 016. S2) is expressed as

According to the present invention, the deviation between the working point of the power tool and the control reference point can be automatically calculated by only one detection position teaching, and the deviation can be stored as an offset amount and corrected. It can eliminate the hassle of workers.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained.

If you execute the offset calculation procedure for each automatic operation,
The position of the wire tip of a work tool attached to a robot, such as a welding torch, can be checked without bothering the operator.
It can be moved closer to the work point of the work tool at any time, reducing bead displacement after welding work.

Further, corrections to the teaching content due to bead deviation can be reduced and quality can be improved by one.

Furthermore, since the correction method is automatic, the time required to calculate the correction amount can also be reduced.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram used to explain the present invention in detail, Fig. 2 is a diagram showing how the work tool is installed, Fig. 3 is an installation diagram of the contact position detection jig, and Fig. 4 is an implementation of the detection position teaching means. Figure 5 is a flowchart of contact position detection, Figure 6 is a flowchart of misalignment correction, and Figure 7 is a contact position vector. 1 to 6: robot drive unit, 01 to θ6: position of each drive unit Data, 7: Work tool fixture, 8: Work tool, 8-a: Work tool tip, 9: Jig, 1o: Robot controller, 11
: Arithmetic unit, 12: Storage unit, 13: Operation command unit, 14: @
Pressure application part, 15: Detection part, 16: Pin, 17: Groove, 18
: Bolt, Q: Reference point, Pa: Working point No. 1 $ 2 Figure η ~ Figure 4 Figure 6

Claims (1)

[Claims] 1. A robot that attaches a work tool to a mounting jig attached to a robot body, stores the error between the working point of the robot's work tool and a reference point as an offset amount, and corrects the deviation. In the misalignment correction method, (1) within the operating range of the robot, three conductive
(2) applying a voltage between a flat plate and a conductive contact provided on a part of the working tool to move the robot in a preset direction; (3) storing position data of the robot at the contact position; (4) sequentially performing the storing and calculating the difference between the previous position data and the current position data; (5) storing the error and the offset amount; and (6) moving the working point of the power tool in a direction that absorbs the offset amount. 1. A method for correcting center misalignment of a robot, comprising a step of shifting the robot. 2. A robot misalignment correction method according to claim 1, characterized in that a welding wire is used as the contact of the working tool. 3. The method for correcting misalignment of a robot according to claim 1, wherein the robot fixing part is provided with a pin hole and a groove, and the flat plate is removable from the robot fixing part.