JPH02284886A - Position teaching correcting method for workpiece positioning device - Google Patents

Abstract

PURPOSE:To optimize a positioning target value based on a position teaching data input to a workpiece positioning device by adding the correction, based on a condition of distributing measured position data, to the positioning target value based on the position teaching data input to the workpiece positioning device. CONSTITUTION:A position teaching data, stored in a teaching data memory 71 of a control unit 70 and input through a communication interface 73 by a command of a CPU72, is received to a controller 45 outputting a target value, corresponding to this data, to a servo amplifier 50. A servo constant setting part 53 in this servo amplifier 50 compares a position command from the control ler 45 with an input from an interface 51 showing speeds of servomotors 12, 11, 18, determining a servo constant K deciding a position loop gain in accor dance with the compared deviation. This constant K is input as a speed com mand to a constant setting part 54, and in accordance with a deviation between the input to this part 54 and the input from the interface 51, a servo constant K' is determined, operating the servomotor positioning a workpiece.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a position teaching correction method for optimizing a positioning target value based on position teaching data input to a workpiece positioning device that positions a workpiece during vehicle body assembly. It is related to.

(Prior Art) As a vehicle body assembly apparatus using a workpiece positioning device, there is one described in, for example, Japanese Patent Application Laid-open No. 110581/1981. This device is equipped with multiple workpiece positioning devices (robots) and welding robots on a frame installed on the main body temporary assembly stage of the car body assembly line. The workpieces that make up the main body of the machine are positioned, and the positioned workpieces are spot welded by a welding robot to temporarily assemble the main body.

(Problems to be Solved by the Invention) When positioning a workpiece using a positioning target value based on position teaching data using such a workpiece positioning device, in a conventional example, position data is sent to a position measuring means when positioning is completed. As long as the obtained position data is within a certain range (hereinafter referred to as in-position width) centered on the positioning target value based on the position teaching data (i.e. set value), the positioning In the conventional method, the positioning target value is repeatedly used as is, assuming that a predetermined positioning accuracy has been achieved.

By the way, even if the position data falls within the in-position width in each positioning step, it may not be desirable in terms of positioning accuracy. That is, when the data distribution of the position data is analyzed, it becomes a normal distribution state where the positioning target value and the data distribution center value match, as shown in FIG. ).

In (b), the deviation from the target value is used instead of the position data, but the content is the same) is ideally within the in-position width. As shown in , even if all the position data is within the in-position width, the distribution center may deviate from the positioning target value (this deviation may occur, for example, due to backlash or mechanical failure of the workpiece positioning device). be).

If a deviation occurs between the distribution center of position data and the positioning target value in this way, the accuracy of in-position width management will decrease, making it difficult to optimize the positioning target value based on the position teaching data input to the workpiece positioning device. It will no longer be possible to convert it into a value.

An object of the present invention is to solve the above-mentioned problems by adding correction based on the distribution state of measured position data to a positioning target value based on position teaching data input to a workpiece positioning device.

(Means for Solving the Problems) For this purpose, a position teaching correction method for a workpiece positioning device according to the present invention uses position teaching data input to a workpiece positioning device that positions a workpiece constituting a vehicle body or a main part of the vehicle body. Based on this, when determining the positioning target value,
At the time of completion of positioning, each time a predetermined positioning accuracy is achieved, position data is measured by the position measuring means, and when the obtained position data reaches a predetermined number, the data distribution center value obtained by data distribution analysis of these position data is calculated. , calculate the deviation from the positioning target value based on the position teaching data,
The present invention is characterized in that the next positioning target value is determined by adding a correction to the positioning target value to eliminate the deviation.

(Function) The workpiece positioning device positions the workpiece constituting the vehicle body or the main part of the vehicle body using a positioning target value based on input position teaching data.

Here, the position measuring means measures the position data of the workpiece every time a predetermined positioning accuracy is achieved upon completion of positioning, and when the obtained position data reaches a predetermined number, a data distribution analysis of these position data is performed. Through this analysis, the data distribution center value is determined, and the deviation between this value and the positioning target value based on the position teaching data is calculated.

This deviation occurs, for example, due to a mechanical failure in the pack runch or the workpiece positioning device, and when this deviation occurs, the actual workpiece positioning position always tends to be positive or negative with respect to the positioning target value of the workpiece positioning device, which is preferable. do not have.

Therefore, learning control is performed to add correction to the positioning target value to eliminate the deviation, and the next positioning target value is determined.

As a result, the desired normal distribution state is achieved in which the positioning target value and the data distribution center value of the workpiece position data match, and the in-position width management accuracy is improved based on the position teaching data input to the workpiece positioning device. Positioning target values can be optimized.

(Example) Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram illustrating the configuration of a workpiece positioning device used in an embodiment of the method of the present invention, and numeral 4 in the figure indicates the workpiece positioning device.

The workpiece positioning device (hereinafter referred to as locator) 4 is equipped with an approach axis of a three-dimensional orthogonal coordinate system and various working means (not shown).In order to install a plurality of locators 4 in the vehicle body assembly area, a concave frame is used. 2 will be provided. When attaching these locators 4 to the frame 2, for the purpose of making the vehicle body assembly apparatus applicable to various vehicle types and table types, for example, the locators 4 are mounted outside the frame 2 in the conveying direction, in other words, in the three-dimensional direction shown in FIG. Fixing the base 8 of the locator 4 to the slider 7 of a linear guide consisting of a rail 6 laid extending in the Y-axis direction of the original orthogonal coordinate system and a slider 7 engaged with the rail 6. According to this, each locator 4 is supported by the frame 2 on the outside thereof, and is moved in the extending direction of the rail 6, depending on the type of car body to be assembled and the table type. It can be moved horizontally as required.

In this vehicle body assembly apparatus, these locators 4 are used to position and hold the side roof rail of the side body as a workpiece, and the approach shaft 5, which penetrates the base 8 and projects inside the frame 2, is used to position and hold the side roof rail of the side body as a workpiece. A servo motor 12 is connected to the rear end of the approach shaft 5, and this servo motor 12 is connected to the inner side of the approach shaft 5. The screw shaft 13 of the ball screw is connected to the rear end thereof extending through a coupling 14, and a ball nut 15 fixed to the base 8 is screwed onto the screw shaft 13. Here, the tip of the screw shaft 13 is rotatably supported by a bearing 16 fixed to the approach shaft 5.

According to this reciprocating structure, by driving the servo motor 12 to rotate the screw shaft 13, the approach shaft 5 is moved to the heath 8 based on the action of the screw shaft 13 and the ball nut 15 fixed to the base 8. On the other hand, preferably
Under the guidance of the linear guide, it can move forward and backward in the X-axis direction as required together with the screw shaft 13.

Further, in order to drive each locator 4 attached to the frame 2 as described above in the Y-axis direction, a screw shaft 9 of a ball screw is attached to the outside of the frame 2, and this screw shaft 9 A ball nut 0 that is screwed into the ball nut 10 and a servo motor 11 that rotationally drives the ball nut 10 via a timing belt or the like,
Attach to the base 8 of each locator 4.

Furthermore, in this locator 4, a wrist portion 17 is attached to the tip of the approach shaft 5 so that it can be driven forward and backward in a direction perpendicular to the direction of movement of the locator 4, that is, in the X-axis direction in a three-dimensional coordinate system.

Therefore, here, the servo motor 18 is attached to a bracket fixed to the tip of the approach shaft 5, and
While screwing the screw shaft 19 connected to the servo motor 18 into the ball nut 20 fixed to the wrist portion 17,
Also, by engaging the slider 22 fixed to the wrist portion 17 with the rail 21 attached to the approach axis side, the wrist portion 17 is supported on the approach axis 5 by a linear motion guide consisting of the rail 21 and the slider 22. At the same time, the pole nut 20 is moved forward and backward together with the wrist portion 17 with respect to the screw shaft 13 rotating at a fixed position.

Such a wrist portion 17 has a joint portion 24 formed by pivoting a bracket 23 rotatably within a vertical plane at its intermediate portion.
This joint portion 24 can be operated as required by connecting a vehicle type switching cylinder 26 attached to the base member 25 of the wrist portion 17 to the bracket 23 with its piston rod. .

Furthermore, a support device 28 is fixed to the tip of the bracket 23 to contact the outer panel 27a of the side roof rail 27 as a workpiece to position and support it, and is provided to protrude downward from the bracket 23. The yoke 29 includes a clamp cylinder 30 and a clamp connected to the clamp cylinder 30 via a toggle mechanism 31 to abut against the inner panel 27b of the side roof rail 27, in other words to press the side roof rail 27 against the support device 28. Attach the claws 32 respectively.

Therefore, in this locator 4, the support device 28 and the clamp claw 32 can be moved to a desired position in the three-dimensional coordinate system as required, and the vehicle type switching cylinder 2
6 can be pivoted around the articulation 24 in a vertical plane, so that the support device 28 and the clamping pawl 32 can position the side roof rail 27 between them in the desired position. The side roof rail 27 can be held and moved to an appropriate position.

FIG. 2 is a diagram illustrating the configuration of the control system of the locator 4, and 40 in the figure indicates an intelligent amplifier.

The intelligent amplifier 40 includes a controller 45,
It is comprised of a servo amplifier 50 and an axis switching unit 60, and is based on the patent application filed in 1986 by the applicant.
This is a function of the intelligent amplifier described in the specification of No. 143482, in which a positioning target value learning control function, which will be described later, is added. The reason for the name "intelligent amplifier" here is that in addition to the -a-like servo amplifier function,
This is because the amplifier has various arithmetic processing functions that were conventionally performed by an external control device (for example, a large computer).

The intelligent amplifier of Japanese Patent Application No. 143482/1982 includes a serial/parallel converter as an input/output interface, a microcomputer for executing instructions as a controller, and a servo controller.
The microcomputer for executing instructions performs communication control and controls the servo controller, and the servo controller is composed of the microcomputer for executing instructions and controls device-determined target values and a position sensor for the servo motor. The servo amplifier converts the position deviation from the actually measured position data fed back into the target speed, and the servo amplifier calculates the difference between this target speed and the actually measured speed fed back from the servo motor's speed sensor. The speed deviation is amplified and supplied to the servo motor as a drive current, and through food pack control, the intelligent amplifier performs positioning functions.

In the intelligent amplifier 40 of the present invention, as shown in FIG.
is stored in the teaching data memory 71 of the arithmetic processing unit (
It receives position teaching data, that is, a setting value corresponding to a desired positioning position (this value is determined according to the vehicle type) inputted via the communication interface 73 according to an instruction from the CPU 72, and responds to this setting value. It outputs a target value to the servo amplifier 50, and also corrects this target value by executing a control program to be described later.
Based on this target value, the servo amplifier 50 performs the same servo control as in the conventional example described above for the X, Y, and Z-axis servo motors 12.1118 as manipulators that position the workpiece via the axis switching unit 60. . Here, the servo amplifier 50 includes, for example, an interface 51,
The interface 51 includes an encoder 56 (this encoder is an absolute encoder that constantly outputs position data) that detects pulses corresponding to the rotation speed of the servo motor 12, 11, 18. The input signal from the type encoder) is sent to the servo constant setting sections 53 and 54 and the controller 4.
5, and the servo constant setting section 53 is input to the controller 45.
The position command from the interface 51 is compared with the input from the interface 51, and a servo constant K that determines the position loop gain is determined according to their deviation, and is inputted as a speed command to the constant setting section 54, and the constant setting section 54 This input is compared with the input from the interface 51, and a servo constant that determines the speed loop gain is determined according to their deviation, and is input to the amplifier 55 as a current command. The servo motors 12, 11.18 are operated based on the feedback current from the motor to position the workpiece.

The axis switching unit 60 is a type of electronic switch that switches the human output for each of the X, Y, and Z axes at predetermined intervals. It can be omitted if provided for each movable axis of the manipulator.

Furthermore, in addition to the above, the control device 70 includes a memory 74 that stores measured position data, and an external interface 77 that connects a pendant 75 and a monitor 76 for data monitoring.
Controller 4 of intelligent amplifier 40 in U72
5).

The controller 45 receives the X and Y signals from the encoder 56.

Servo motor rotation speed and control device 7 corresponding to Z-axis
When the position teaching data (setting value) from 0 is input, the third
The control program shown in the figure is executed to perform position teaching correction according to the method of the present invention for each of the X, Y, and Z-axis servo motors of the servo mechanism of the workpiece positioning device.

That is, first, in step 101, the workpiece positioning device is started, and in step 102, the position teaching data input from the control device 70, that is, the setting value corresponding to the desired positioning position, is set as the positioning target value P2, and in step 103, the operation of the positioning device is completed. At this time, it is determined whether or not a predetermined positioning accuracy has been achieved.

If the positioning device is operating normally and has achieved a predetermined positioning accuracy, the position data is read from the encoder 56 in step 104, and the deviation between this position data and the positioning target value Pp is calculated in step 105. If the positioning data is larger than the positioning target value Pp, it is considered a plus).

In the next step 106, it is checked whether a predetermined number of deviation data collected in this way, that is, the number required for the data distribution analysis described below, has been obtained.If it is insufficient, data is collected in step 105 until the predetermined number is reached. Repeat.

In the next step 107, data distribution analysis is performed based on these deviation data, and the deviation l of the data distribution center value D7 from the positioning target value Pp is calculated (f=P, -Dm).
, In order to eliminate this deviation l, the next positioning target value PN is determined in step 108 by correction such that p,4=pp+z. Note that the calculation of the deviation data in step 105 may be omitted, and data distribution analysis may be performed directly from the workpiece position data in a step corresponding to step 107.

The effect of the above control will be explained using FIGS. 4(a) and 4(b).

The workpiece positioning device positions the workpiece constituting the vehicle body or the main part of the vehicle body based on the positioning target value based on the position teaching data (setting (1 m)) input from the control device 70. At this time, the control program shown in FIG. By executing steps 103 and 104, each time a predetermined positioning accuracy is achieved, for example, the rotational speed pulse measured by the encoder 56 changes to the in-position width (centered around the positioning target value) shown in FIG. 4(a). (within the range of N pulses), read the position data and use this position data as
By executing steps 105 and 106, the deviation data from the positioning target value (corresponding to deviation=0 in FIG. 4(a)) is converted and captured until the number required for data distribution analysis is reached.

As a result of the data distribution analysis in step 107, the data collected in this way is biased within the in-position width, for example, as shown by curve A in FIG. If it is found that the position shows a negative tendency with respect to the positioning target value Pp, step 108 is executed to cancel this bias, that is, the data distribution center value is set to the positioning target value P.
2, the next positioning target value P8 is determined by adding a correction to the positioning target value Pp to cancel the deviation P (PH-Pp+ffi).

As a result, next time, if the workpiece is positioned using this positioning target value P, the position data distribution will be as shown in Fig. 4(b).
The state of the curve Δ is improved to the state of the curve B, and it is possible to approach the ideal data distribution (normal distribution) shown in FIG.

Therefore, even if the deviation P occurs due to, for example, backlash or a mechanical failure of the workpiece positioning device (for example, poor adjustment of the ball screw), the in-position width management accuracy can be improved by executing the learning control as described above.
The positioning target value based on the position teaching data input to the workpiece positioning device can be optimized.

(Effects of the Invention) Thus, as described above, the position teaching correction method of the workpiece positioning device of the present invention corrects the positioning target value based on the position teaching data input to the workpiece positioning device based on the distribution state of the measured position data. Since the positioning target value and the data distribution center value of the workpiece position data match, the desired normal distribution state is achieved, and the position teaching data input to the workpiece positioning device is improved by improving the in-position width management by 4n degrees. It is possible to optimize the positioning target value based on

[Brief explanation of drawings]

Fig. 1 is a diagram illustrating the configuration of a workpiece positioning device used in an embodiment of the method of the present invention; Fig. 2 is a diagram illustrating the configuration of the control system of the workpiece positioning device on the same side; Flowchart showing a control program of an embodiment of the method of the invention. FIGS. 4(a) and 4(b) are diagrams showing data distribution of deviation data from a positioning target value based on measured position data, respectively. 4...Work positioning device (locator) 11, 12.
18... Servo motor 40... Intelligent amplifier 45... Controller 50... Servo amplifier 60... Axis switching unit 70... Control device Fig. 2 Fig. 3 Fig. 4 (a) (b) )

Claims (1)

[Claims] 1. When determining a positioning target value based on position teaching data input to a workpiece positioning device that positions a workpiece constituting the vehicle body or a main part of the vehicle body, a predetermined positioning accuracy is achieved upon completion of positioning. Each time, the position data is measured by the position measuring means, and when the obtained position data reaches a predetermined number, the positioning target is determined based on the position teaching data of the data distribution center value obtained by data distribution analysis of these position data. 1. A position teaching correction method for a workpiece positioning device, comprising: calculating a deviation from the positioning target value, and adding correction to the positioning target value to eliminate the deviation to determine the next positioning target value.