KR100305944B1 - Calibration method for off-line application of robots in the bodywork production line - Google Patents

Abstract

More particularly, the present invention relates to a method of calibrating a robot, and more particularly, to a method of calibrating a robot using a method of calibrating an absolute position error occurring due to errors of various devices on a work line And more particularly, to a calibration method for off-line program application of a robot of a vehicle body production line which increases the reliability of the offline program method by minimizing the number of the robot.

When a work program of a robot used in a vehicle body line is generated by an off-line method, a special calibration operation for a body line has not been performed conventionally, so that a position error due to an absolute position error of the robot is very large, However, according to the calibration method for applying the off-line program of the vehicle body production line robot of the present invention, the absolute position error is only 0.5 to 2 mm And it takes approximately one hour to generate the actual robot program using the offline program with the increased reliability. In addition, it is possible to accurately determine whether the robot is operable or not, Of the robot used in When an up-program is input to a computer, it is possible to judge an accurate robot operation state.

Description

Calibration method for off-line application of robots in the bodywork production line

More particularly, the present invention relates to a method of calibrating a robot, and more particularly, to a method of calibrating a robot using a method of calibrating an absolute position error occurring due to errors of various devices on a work line And more particularly, to a calibration method for off-line program application of a robot of a vehicle body production line which increases the reliability of the offline program method by minimizing the number of the robot.

Currently, the method of determining the layout of the car body production line is modeled on a computer, and a method of roughly determining the position of the robot, the work tool to be used such as the welding gun, and the position of other devices is used. The purpose of this work is to examine the possibility of mutual interference between robots, welding guns, devices, and the possibility of robot operation by virtually determining the layout of the robot on the computer before installing the layout of the actual body production line. Especially, it is very important to determine the position of the robot and to decide the welding tool, which is the working tool to be used.

When the layout installation of the actual bodywork production line is completed through these operations, a work program of the robot should be created. In this case, since it takes a considerable amount of time to generate the robot work program using the actual robot teaching machine, the offline programming method is used to generate the work program using the robot modeled on the computer in order to reduce the time required.

However, the actual layout state has a considerable positional error with the layout modeled on the computer due to installation errors of various devices. In order to reduce this error, it is necessary to find and calibrate a device that generates an error on the bodywork line.

However, currently, there is no special calibration method for the bodywork production line. For this reason, a work program of the bodywork production line robot is created and input to the robot is used. In other words, after generating a robot work program that defines only a rough way point, the robot program is completed by performing precise teaching about the welding point using the robot teaching machine.

In the conventional method as described above, various devices are modeled on a computer by referring to the design drawings, and a work program of the robot is generated using the models.

Figure 1 shows this modeled state. In this case, an error occurs in the mounting position between the actual vehicle body line and the modeled vehicle body line on the computer. When the work program generated on the computer is input to the actual robot due to such an error, a considerable absolute position error occurs, Since it is impossible to teach, it must be satisfied with the creation of a work program that approximates to an approximate position.

In this case, if the robot work program is generated by using the offline program method, the completeness is extremely low. Therefore, there is a problem that it takes a considerable time to work on the on-line for generating a work program.

To solve this problem, a calibration method that minimizes the absolute position error of a robot installed on a vehicle body line is required, but a satisfactory calibration method has not been developed yet.

It is therefore an object of the present invention to provide a method and apparatus for generating a work program of a robot of a vehicle body production line by an offline programming method, And to provide a calibration method for offline program application of a robot of a bodywork production line which increases the reliability of the offline programming method by minimizing the position error.

1 shows a body welding process modeled on a computer,

2 is a conceptual diagram showing a calibration device using a non-contact method.

3 is a conceptual diagram showing a calibration apparatus using a contact-type method,

4 is a perspective view showing a measurement jig.

Description of the Related Art

1: Laser sensor 2: Welding gun

3: robot 4: reference plane on the vehicle body conveying device

5: Fixing jig 6: Body reference coordinate system [W]

7: Measuring jig 8: Vehicle transport device

9: Body

^W T _J : Distance from [W] to the body position fixing jig

^W T _R : Distance from [W] to robot

^R T ₆ : Distance from robot to end of robot

⁶ T _T : Distance from end of robot to welding spot of welding gun

In order to accomplish the above object, a calibration method for applying an offline program to a robot of a vehicle body production line of the present invention includes a non-contact method using a laser sensor and a contact method using a measurement jig.

First, a non-contact method using a laser sensor will be described.

A calibration method for off-line program application of a vehicle body production line robot according to the present invention is a method for measuring three or more reference planes (Pn) provided with a vehicle body locating pin, which is a work object, A second step of defining a vehicle body reference coordinate system [W] by using the values measured in the first step and the above-mentioned values; and a second step of measuring the position of at least three of the locating pins Jn existing within the working range of the robot with a laser sensor A fourth step of measuring the coordinate system [T] of the work point, which is data necessary for performing calibration in the robot work range, by a laser sensor, and a fourth step of measuring the error of the position measured in the third step A fifth step of inputting pins Jn on a computer to modify the modeling of the vehicle body conveying device, and a fifth step of calibrating using the data measured in the fourth step Claim 6 is characterized in that comprising the step of performing.

Hereinafter, an embodiment of a calibration method for off-line program application of the robot of the vehicle body production line of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a view showing a body welding process modeled on a computer, and FIG. 2 is a conceptual diagram showing a calibration device using a non-contact method.

As shown in FIG. 2, a method for calibrating an offline program of a spot welding robot according to an embodiment of the present invention uses a laser sensor 1, (S1) of measuring at least three reference planes (Pn) provided with a location pin (vehicle body position fixing pin) for fixing a vehicle body, which is an existing work object, A second step (S2) of defining a reference coordinate system [W]; measuring the position of at least three of the locating pins (Jn) existing in the working range of the robot with the laser sensor (1) A fourth step S4 of measuring the coordinate system [T] of the contact point of the welding gun 2, which is data necessary for carrying out the calibration on the working range of the robot, by the laser sensor 1, The location pins (Jn) measured in the third step (S3) Input and comprises a fifth step (S5) of modifying the models of the car body conveying device (8), a sixth step of using the data measured in the first step 4 (S4) to perform a calibration (S6).

The reference plane Pn is three of P1, P2, and P3, and the location pin Jn is three of J1, J2, and J3.

Hereinafter, the operation of the calibration method for applying the offline program of the spot welding robot according to the embodiment of the present invention will be described in detail.

The body welding work line is composed of a robot 3, a welding gun 2, a body-moving device 8, and various jigs. In the calibration method of the present invention, the reference coordinate system [W] on the vehicle body 9 is measured in order to minimize the measurement error, and all the measurements are performed based on the measurement. In addition, the measurement error of the data for calibration is minimized by measuring the position error of the jig for positioning the vehicle body 9 with respect to the vehicle body reference coordinate system [W].

This calibration operation is basically carried out in the following state in the state shown in FIG.

First, the reference plane Pn of the vehicle body conveying device 8 is measured using the laser sensor 1. [ The positions of all the jigs on the vehicle body conveying device 8 are determined based on the reference plane Pn. Further, this reference plane is defined for the vehicle body reference coordinate system [W], and thus is used for determining the vehicle body reference coordinate system [W]. That is, the position and direction vector of the body reference coordinate system [W] are defined using the measured values here. The definition of this body reference coordinate system [W] is very important and in order to minimize the measurement error that occurs during the calibration, the data necessary for the calibration should be measured based on this coordinate system [W].

Next, a portion for generating a measurement error is a jig for positioning the vehicle body 9. [ Even if the body reference coordinate system [W] is accurately defined, if the position of the jig for positioning the work body 9, which is an object to be worked, can not be accurately measured, errors are accumulated, resulting in a measurement error. For this reason, J1, J2, J3 and J4 of the position pin Jn, which is the position of the jig, are measured using the laser sensor 1. [ This position is defined for the vehicle body reference coordinate system [W]. That is, the position ( ^W T _J ) of the measurement point in FIG. 2 is measured. Here, ^W T _J represents the distance from [W] to J.

In this way, it is possible to minimize the measurement error occurring during the calibration.

When this process is completed, the data required for the actual calibration is measured. That is, the position [T] at which actual welding occurs in the work space of the robot 3 is measured by using the laser sensor 1. [ Figure 3 shows this measurement procedure. The number of measurement points measured here varies depending on the model parameters of the robot 3, but in the case of a general six-axis articulated robot, it has a measurement point of about 9 to 50 points. Then, at each measurement point, the robot joint value ( ) And the position ( ^W T _J ) of the measurement point at that time are used as input data to perform calibration.

Next, input the measured values of J1, J2, J3, and J4 on the computer to modify the position of the jig being modeled. This is because the positions of J1, J2, J3 and J4 modeled on the computer are the positions in the design, and therefore, it is necessary to correct the actual measured values so that the position of the body 9 as the work object can be corrected.

When these measurements are completed, the measured data is input to the calibration program to perform the calibration. The results are divided into a full calibration and a local calibration depending on whether or not the link parameter of the robot 3 is calibrated. For an in-calibration is also the model parameter of 2 ^W T _R, ^R T _6, ⁶ T _T and the calibration, in the case of a local calibration ^W T _R, ⁶ calibration only model parameters of T _T and ^R T ₆ uses the nominal parameters do.

The full calibration is performed by the following algorithm, in which case there are 50 measurement points for performing the calibration.

= · (One)

= ^W T _T - Forward ( ) (2)

= (3)

Here, Forward () is a forward kinematic function of the robot, Is a parameter of the model to be calibrated, Is the minute change amount of the model parameter, Is the difference between the nominal model parameter and the actual model parameter, and i is the number of measurements.

Local calibration is performed by the following algorithm, where 9 to 12 measurement points are used to perform the calibration.

= ^W T _T - ^W T _nT (4)

Where ^W T _nT is the nominal value of the initially defined [T] and is calculated using the least square method without using the same method as equation (3) .

Next, a case of the contact type method using the measuring jig 7 will be described.

A calibration method for off-line program application of a vehicle body production line robot according to the present invention is a method for measuring three or more reference planes (Pn) provided with a vehicle body locating pin, which is a work object, A second step of defining a vehicle body reference coordinate system [W] by using the values measured in the first step and the above-mentioned values; and a second step of measuring the position of at least three of the locating pins Jn existing within the working range of the robot with a laser sensor A coordinate system [T] of the work point, which is data necessary for calibration in the working range of the robot, is measured by a measuring jig placed on the jig on which the vehicle body is located, MPn), and a fourth step of inputting the location pins (Jn) measured in the third step on a computer to modify the modeling of the vehicle body conveying device And, using the data obtained in the fourth step is characterized in that comprising a sixth step of performing a calibration.

Hereinafter, an embodiment of a calibration method for off-line program application of the robot of the vehicle body production line of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a conceptual diagram showing a calibration apparatus using a contact-type method, and FIG. 4 is a perspective view showing a measurement jig.

As shown in FIG. 3, a method for calibrating an off-line program of a spot welding robot according to an embodiment of the present invention includes the steps of: using a laser sensor 1, A first step (T1) of measuring three or more reference planes (Pn) provided with locating pins for fixing the vehicle body, a second step (T2) of defining a vehicle body reference coordinate system [W] , A third step (T3) of measuring the position of at least three of the locating pins (Jn) in the working range of the robot with the laser sensor (1) and measuring an error with the nominal value, A fourth step (T4) of teaching the coordinate system [T] of the working point, which is data necessary for carrying out, to three or more measuring points (MPn) by the measuring jig (7) provided on the jig on which the vehicle body (9) In the third step (T3), the position pin J a fifth step T5 for inputting the model data of the vehicle body transfer device 8 on the computer and inputting the model data of the vehicle body transfer device 8 onto the computer and a sixth step of performing the calibration using the data measured in the fourth step T4, ).

The reference plane Pn is three of P1, P2, and P3, the location pin Jn is three of J1, J2, and J3, and the measurement point MPn is three of MP1, MP2, and MP3.

Hereinafter, the operation of the calibration method for applying the offline program of the spot welding robot according to the embodiment of the present invention will be described in detail.

The contact type method using the measuring jig 7 is mostly the same as the above-mentioned non-contact type method. That is, the measurement of the body reference coordinate system [W] and the measurement of the jig are the same in order to minimize the measurement error, but the data measurement method for performing the calibration is different from the non-contact method.

Here, the measuring jig 7 is placed on a jig for positioning the car body 9 using the measuring jig 7 as shown in Fig. 4, and the measurement point MPn (MPn) existing on the measuring jig 7 MP1, MP2, and MP3, the coordinate system [T] of the welding gun contact point of the robot 3 is instructed to receive data. Since there is also a manufacturing error on the measuring jig 7, it is necessary to measure the position of each measuring point using a measuring device and correct the position of the measuring point of the jig modeled on the computer. Here, the number of measurement points to be measured is 9 to 12, and when this method is used, full calibration is not possible because there are not many measurement points to be measured, and it is used for local calibration.

As described above, the robot described as the embodiment of the present invention is a robot for spot welding, but the method of the present invention can also be applied to calibration of a robot used for other purposes, thereby minimizing the measurement error during calibration. That is, the present invention is applicable to a method of calibrating a layout of a vehicle body line in which a vehicle body arc welding, sealing, and handling robots are used. This is because all the above-mentioned robot operation states are designed and installed based on the body reference coordinate system.

When a work program of a robot used in a vehicle body line is generated by an off-line method, a special calibration operation for a body line has not been performed conventionally, so that a position error due to an absolute position error of the robot is very large, However, according to the calibration method for applying the off-line program of the vehicle body production line robot of the present invention as described above, the absolute position error is 0.5 to 6 hours, It takes about 1 hour to generate the actual robot program by using the off-line program in which the proximity teaching is possible and the reliability is increased.

Particularly, when a plurality of models are produced in one line, it is necessary to add various devices to the conventional vehicle body line, and it is very helpful to accurately define the position of each device.

In addition, it is possible to accurately judge the possibility of operation and interference of the robot with respect to a new vehicle body, and to provide an excellent effect of determining an accurate robot operation state when a robot's operation program is input to a computer This is a very useful invention in the automobile manufacturing industry.

Claims (7)

A first step of measuring three or more reference planes (Pn) provided with a vehicle locating pin, which is a workpiece, which is a plurality of workpieces existing in the vehicle body transfer apparatus using a laser sensor, and a step A third step of measuring an error between the position pin (Jn) and a nominal value by measuring the positions of three or more of the locating pins (Jn) in the working range of the robot with a laser sensor; A fourth step of measuring a coordinate system [T] of a work point, which is data necessary for performing calibration on the vehicle, by using a laser sensor, and inputting a position value of the location pins Jn measured in the third step on a computer, And a sixth step of performing calibration using the data measured in the fourth step, and a sixth step of performing a calibration using the data measured in the fourth step. Calibration method for offline program application. 2. The method according to claim 1, wherein the reference plane (Pn) is three of P1, P2 and P3. 3. The method according to claim 1 or 2, wherein the location pin (Jn) is three of J1, J2 and J3. A first step of measuring three or more reference planes (Pn) provided with a vehicle locating pin, which is a workpiece, which is a plurality of workpieces existing in the vehicle body transfer apparatus using a laser sensor, and a step A third step of measuring an error between the position pin (Jn) and a nominal value by measuring a position of at least three of the position pins (Jn) in the working range of the robot with a laser sensor; A fourth step of teaching the coordinate system [T] of the working point, which is data necessary for carrying out the calibration on the range, to three or more measurement points (MPn) by the measuring jig provided on the jig on which the vehicle body is located, A fifth step of modifying the modeling of the vehicle body conveying apparatus by inputting a position value of the location pins Jn on the computer, and performing a calibration using the data measured in the fourth step And a sixth step of performing a calibration process for the off-line program of the vehicle body production line robot. 5. The method according to claim 4, wherein the reference plane (Pn) is three of P1, P2 and P3. 6. The method according to claim 4 or 5, wherein the location pin (Jn) is three of J1, J2 and J3. 7. The method according to claim 6, wherein the measurement point (MPn) is three of MP1, MP2, and MP3.