KR20110123942A - Robot calibration method using digital leveler - Google Patents

Abstract

PURPOSE: A calibration method of a vertical articulated robot using a digital leveler is provided to reduce work time by automatically finding and registering the origin point of each axis of robot joints. CONSTITUTION: A calibration method of a vertical articulated robot using a digital leveler is as follows. Each joint of a robot(110) is moved in a pre-determined pose. The angles of the joints at each pose are measured using a digital leveler(130). The origin point of each joint of the robot is detected using the measured angles. The detected positions are registered as the origin point of each joint of the robot.

Description

Calibration method of vertical articulated robot using digital level meter {ROBOT CALIBRATION METHOD USING DIGITAL LEVELER}

The present invention relates to a method for calibrating a robot, and more particularly, to a method for calibrating a vertical articulated robot using a digital level meter for registering an accurate origin of a robot joint.

Robots that are arranged at various industrial sites and perform operations or movements by automatic adjustment are classified into rectangular coordinate robots, cylindrical coordinate robots, polar coordinate robots, and articulated robots according to arm movements. Of these, articulated robots can rotate parts corresponding to the robot's shoulders, elbows, and wrists, just as a human arm has joints. By controlling the movement of each joint, you can work by moving your arms along the surface, or by moving your arms behind and below the workpiece.

As shown in the power transmission structure and shaft configuration diagram of FIG. 1, the six degree of freedom vertical articulated robot is located on the same axis in which the two axes and the three axes are arranged in the configuration of the axes 1AXIS to 6AXIS ranging from one axis to six axes. It exists and drives two axes and three axes respectively. The 5th and 6th axes are the wrist axis of the robot.

Rotation of the 2 axis 2AXIS rotates the 2 axis link through the reducer connected to the 2 axis drive motor 11 by the rotational movement of the 2 axis drive motor 11, and 3 connected to the other end of the 2 axis link The axis link will move.

Rotation of three axes (AXAXIS) rotates the auxiliary link parallel to the three axes through the reduction gear connected to the three axes drive motor 12 axis by the rotary motion of the three axes drive motor 12, and two axes at the end Auxiliary link parallel to is connected to hinge point and moves parallel to 2 axes. Auxiliary link parallel to the three axis is connected to the end is a predetermined distance away from the center of rotation of the three-axis link is to rotate relative to the hinge point connected to the two-axis link.

Parameters according to the coordinate system of the six degree of freedom vertical articulated robot shown in FIG. 2 are shown in Table 1 below.

The transform matrix from the base frame of the 6 DOF vertical articulated robot to the tool is shown below.

From here,

to be.

From here, to be.

는

와 같다. 즉, In the case of a six degree of freedom vertical articulated robot, two and three axes are parallel mechanisms, so

Is

Same as In other words,

to be.

The posture of the robot tip is typically expressed in roll, pitch, and yaw, and has the following relationship with the transform matrix (1).

Meanwhile, in the present specification, the calibration of a robot refers to a task of finding and registering an absolute origin of each joint of the robot, and may also be called mastering. Looking at the calibration method of the conventional 6-degree of freedom vertical articulated robot, the robot joint origin was found after processing the correct hole for each axis and inserting the calibration jig into the movable hole. That is, the hole was machined at the exact position of the robot base, and the calibration jig was inserted into the machined hole by attaching a shaft to the robot end. At this time, since the position becomes a unique position, it is possible to determine how much the joint angle of the robot is at that position. Therefore, when the robot joint angle is set to that value, origin registration is performed.

However, as described above, it takes a lot of time for the operator to manually find the origin manually, there is a problem that the correction accuracy of the origin is different according to the skill of the operator.

Accordingly, an object of the present invention is to provide a calibration method for a vertical articulated robot using a digital horizontal system for automatically finding and registering an origin of a robot joint automatically and accurately.

In order to achieve the above object, a calibration method of a vertical articulated robot using a digital horizontal system according to the present invention is to measure the angle at each posture with a digital level while moving each joint of the robot to a predetermined position, and then measure the angle. The origin of each joint of the robot is detected using the obtained angle, and the position thereof is registered as the origin of each joint of the robot.

Here, the digital level is preferably a 2D digital level that can measure the angle of the front, rear, left and right.

In addition, the robot is a six degree of freedom vertical articulated robot, it is preferable to register the origin of the three to six axes of the robot joint.

In addition, the origin registration method includes the steps of placing all axes of the robot at the point estimated as the origin; Measuring the pitch, which is a tilt defined based on the y direction of the robot base coordinate system by rotating the 4 axes by ± 90 °, and correcting the 3-axis error to register the 3-axis origin; Measuring the pitch by rotating the 4 axes to 0 °, and then correcting the 5 axis errors to register the 5 axis origins; Measuring a roll, which is an inclination defined based on the x direction of the robot base coordinate system by rotating the 5 axes by 90 °, and then registering the 4 axis origin by correcting the 4 axis error; After measuring the roll by rotating the five axes to 0 °, it is preferable that the six-axis error is corrected and the six-axis origin is registered.

을 계산하는 단계와;

를

만큼 회전시켜 그 상태를 3축의 원점으로 등록하는 단계를 포함하는 것이 바람직하다. In addition, the process of registering the three-axis origin, the step of measuring the pitch β _{+ 90} after rotating the four axes to 90 °; Measuring pitch β- ₉₀ after rotating the four axes to −90 °; Sum of pitch β _{+ 90} and pitch β _-90

Calculating a;

To

It is preferable to include the step of rotating as much as to register the state as the origin of the three axes.

In addition, the process of registering the five-axis origin, the step of measuring the pitch β ₀ after rotating the four axes to 0 °; It is preferable to include the step of rotating θ ₅ by pitch β ₀ and registering the state as the origin of five axes.

In addition, the process of registering the four-axis origin, measuring the roll γ ₉₀ after rotating the five axes to 90 °; It is preferable to include rotating the θ ₄ by roll γ ₉₀ and registering the state as the origin of four axes.

In addition, the process of registering the six-axis origin, measuring the roll γ ₀ after rotating the five axes to 0 °; and rotating the θ ₆ by roll γ ₀ to register the state as the origin of the six axes.

According to the present invention, by automatically finding and registering the origin of each axis of the robot joint using a digital level, it takes the advantage of not only less work time but also improve the precision of the origin.

1 is a power transmission structure and axis configuration diagram of a six degree of freedom vertical articulated robot.
2 is a conceptual diagram illustrating a coordinate system of a six degree of freedom vertical articulated robot.
Figure 3 is a block diagram of a device for performing a robot calibration using a digital level in accordance with the present invention.
4 is a conceptual diagram illustrating the installation of the digital horizontal system of FIG. 3.
5 is a flow chart illustrating a calibration method of a vertical articulated robot using a digital horizontal system according to the present invention.
6 is a flowchart for explaining a process of registering a three-axis origin in FIG.
7 is a flowchart for explaining a process of registering a 5-axis origin in FIG.
8 is a flowchart for explaining a process of registering a 4-axis origin in FIG.
9 is a flowchart for explaining a process of registering a six-axis origin in FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the following will describe a preferred embodiment of the present invention, but the technical idea of the present invention is not limited thereto and may be variously modified and modified by those skilled in the art.

As shown in FIG. 3, the device configuration for calibrating a robot using a digital level according to the present invention is a robot 110 by a jig 120 for measuring a posture of a robot 110 and a robot 110 as a calibration target. The robot controller 150 is connected through the communication cable 140 to receive the output signal measured by the digital leveler 130 and the digital leveler 130 installed in the distal end of the 110, the robot controller 150 for controlling the operation of the robot Is made of. Here, the digital leveler 130 and the robot controller 150 may transmit and receive data through serial communication (eg, RS232C).

In the calibration method of a vertical articulated robot using a digital horizontal system according to the present invention, the angle of each posture is determined by the digital horizontal system 130 while moving each joint of the robot 110 to a predetermined position through the above-described device configuration. After the measurement, the origin of each joint of the robot 110 is detected using the measured angle, and the position is registered as the origin of each joint of the robot 110.

In this case, the digital level 130 may be a 2D digital level that can measure the angle of the front, rear, left and right. The robot 110 is a six degree of freedom vertical articulated robot, and may register an origin of three to six axes among joints of the robot 110.

5 is a flowchart illustrating a calibration method of a vertical articulated robot using a digital horizontal system according to the present invention, 6 is a flowchart illustrating a process of registering a three-axis origin in FIG. 5, and FIG. Flow chart for explaining the process of registering the 5-axis origin, Figure 8 is a flow chart for explaining the process of registering the 4-axis origin in Figure 5, Figure 9 illustrates the process of registering the 6-axis origin in Figure 5 Flowchart for

는 i번째 로봇 관절의 움직인 각도,

는

,

는

, roll은 로봇 베이스 좌표계의 x방향을 기준으로 정의된 기울기, pitch는 로봇 베이스 좌표계의 y방향을 기준으로 정의된 기울기를 의미한다. First, let's define the term

Is the angle of movement of the i-th robot joint,

Is

,

Is

, roll is the slope defined based on the x direction of the robot base coordinate system, and pitch is the slope defined based on the y direction of the robot base coordinate system.

(

)을 계산한다(S123). 마지막으로,

를

만큼 회전(

)시킨 후, 그 상태를 3축의 원점으로 등록한다(S124). Looking at the method of registering the origin with reference to Figures 5-9, first place all axes of the robot at the point estimated as the origin (S110). Subsequently, after the four axes are rotated by ± 90 °, the pitch, which is a slope defined based on the y direction of the robot base coordinate system, is measured, and the three axes are corrected to register the three axes of origin (S120). Specifically, looking at the process of registering the three-point origin (S120), the pitch β _{+ 90} is measured after rotating the 4 axis to 90 °, the pitch β _-90 is measured after rotating the 4 axis to -90 ° (S121) ), (S122). And the sum of pitch β _{+ 90} and pitch β _-90

(

) Is calculated (S123). Finally,

To

Rotate by

After that, the state is registered as the origin of three axes (S124).

Subsequently, after measuring the pitch by rotating the 4 axes to 0 °, the 5 axis error is corrected to register the 5 axis origin (S130). Specifically, referring to the process of registering the 5-axis origin (S130), the pitch β ₀ is measured after rotating the 4 axes to 0 ° (S131). Then, after rotating θ ₅ by pitch β ₀ (θ ₅ = β ₀ ), the state is registered as the origin of five axes (S132).

Subsequently, after measuring the roll, which is a tilt defined based on the x direction of the robot base coordinate system by rotating the 5 axes at 90 °, the 4 axis error is corrected to register the 4 axis origin (S140). Specifically, looking at the process of registering the four-axis origin (S140), after rotating the five axes to 90 ° to measure the roll γ ₉₀ (S141). Then, after rotating θ ₄ by roll γ ₉₀ , the state is registered as the origin of four axes (S142).

Finally, after measuring the roll by rotating the five axes to 0 °, the six-axis error is corrected to register the six-axis origin (S150). Specifically, looking at the process of registering the six-axis origin (S150), after rotating the five axes to 0 ° to measure the roll γ ₀ (S151). Then, after rotating θ ₆ by roll γ ₀ , the state is registered as the origin of six axes (S152).

In this way, after positioning all axes of the robot at the point estimated as the origin, the origin is registered in the order of three axes, five axes, four axes, and six axes.

Now, more specifically, the calibration method of the vertical articulated robot using the digital horizontal system according to the present invention will be described for each process.

<Initial setting>

로 정의하자. 눈으로 관찰하더라도

는 비교적 작은 값을 가지므로 다음의 관계를 얻을 수 있다. Observe with your eyes and place all joints at their origin. At this time, since before the calibration is performed, the joint will not be located at the exact origin, and an error exists.

Let's define Even if you observe with your own eyes

Since has a relatively small value, the following relationship can be obtained.

<3-axis calibration>

로 갈 것이다. 여기에서

는 위에서 설명한 바와 같이 4축의 원점 오차를 의미한다. 4 axes + 90 °, After moving to -90 °, measure the pitch and define the values as β _{+ 90} and β _-90 . Of course, since the 4 axis is not calibrated yet, it is not exactly positioned at +/- 90 ° , so the actual 4 axis

Will go to From here

As described above, it means the origin error of 4 axes.

Equations 2 and 5 are used to correct the angles of the three axes from the relationship between the pitch and each joint. First, the following approximation is used.

First, rewrite Equation 5 as follows.

인 경우, 수학식 2로부터

를 계산하면 아래와 같다.

If, from equation (2)

The calculation is as follows.

Here, applying equations 8 and 9

이므로,

으로 할 수 있다. Becomes From here,

Because of,

You can do

By calculating α _Z in the same way,

이므로 atan2()로 표현할 필요없이 tan^-1()로 표현할 수 있다. Now, substitute Equation 11 into Equation 5,

Therefore, it can be expressed as tan ^-1 () without having to express it as atan2 ().

일 때, 위와 마찬가지의 방법을 적용하면,

If you apply the same method as above,

to be.

을 추정할 수 있다. 즉, 두 수학식을 더하면

가 소거되므로 다음의 결과를 얻는다. After measuring β _{+ 90} and β _-90 , using Equations 12 and 13

Can be estimated. In other words, if you add two equations

Is eliminated, and the following results are obtained.

으로 추정한 위치가 실제로는

인 위치인 것이다. 그러므로,

를

만큼 회전(

)시켜, 그 상태를

의 원점으로 등록한다.That is

The location estimated by

It is the position that is. therefore,

To

Rotate by

) The state

Register to the origin of.

<5-axis calibration>

으로 간주한다.

에 위치시키면, pitch와 그 관련 수학식은 다음과 같다. Since the calibration of the three axes was completed in the previous procedure,

To be considered.

When placed at, the pitch and related equations are as follows.

therefore,

Becomes

Therefore, the pitch + β ₀ is measured by moving θ ₄ to 0 ° (since θ ₄ = δ ₄ since it is not corrected yet). Move to θ ₅ = δ ₅ = β ₀ and register as origin.

4-axis and 6-axis calibration

으로 간주 할 수 있게 되었다.

으로 세팅하였을 때, rotation vector를 고찰하겠다. 수학식 2는 아래와 같이 된다. According to the previous result

Could be considered.

When set to, we will consider the rotation vector. Equation 2 is as follows.

Therefore, Equations 5-7

This is equivalent to an intuitively conceivable result. Since roll (γ) is a form with 4 and 6 axes added, it is not possible to measure 4 and 6 axes independently in this state.

를 구하면 아래와 같다. θ₅=90°일 때 {8}이 {0}과 일치하므로 θ₅=0°일 때 {8}은 {T}To calibrate the four axes, take advantage of the fact that if you rotate θ ₅ = 90 ° in an intuitive way, the jig roll is only determined by θ ₄ . That is, the jig coordinate system and the base frame in the state where θ ₅ = 90 ° are matched, and the jig coordinate system at this time is defined as {8}.

Is obtained as follows. {8} matches {0} when θ ₅ = 90 °, so {8} equals {T} when θ ₅ = 0 °

90 ° is rotated in the pitch direction.

Therefore, the roll is as follows.

In other words, since the value of roll becomes the error of 4 axes, it is possible to correct θ ₄ by measuring the roll with a horizontal gauge. After correcting θ ₄ , set θ ₅ = 0 ° and measure roll to calibrate 6 axes.

On the other hand, although the calibration method of a vertical articulated robot using a digital horizontal system according to the present invention has been described according to a limited embodiment, the scope of the present invention is not limited to a specific embodiment, and having ordinary knowledge in connection with the present invention. Many alternatives, modifications and variations can be made without departing from the scope of the disclosure. That is, six degrees of freedom can be applied to other robots as well as vertical articulated robots in the same way.

Accordingly, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by the embodiments and the accompanying drawings. . The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

110: robot 120: jig
130: level 140: communication cable
150: robot controller

Claims (8)

After moving each joint of the robot to a predetermined posture, measure the angle at each posture with the digital level, and then use the measured angle to detect the origin of each joint of the robot and move the position to the origin of each joint of the robot. Calibration method of a vertical articulated robot using a digital horizontal system characterized in that the registration. The method according to claim 1,
The digital level meter is a calibration method of a vertical articulated robot using a digital level meter, characterized in that the 2D digital level which can measure the angle of the front, rear, left and right. The method according to claim 2,
The robot is a six degree of freedom vertical articulated robot, and the calibration method of the vertical articulated robot using a digital level, characterized in that to register the origin of the three to six axes of the robot joint. The origin registration method according to claim 3,
Positioning all axes of the robot at a point estimated from the origin;
Measuring the pitch, which is a tilt defined based on the y direction of the robot base coordinate system by rotating the 4 axes by ± 90 °, and correcting the 3-axis error to register the 3-axis origin;
Measuring the pitch by rotating the 4 axes to 0 °, and then correcting the 5 axis errors to register the 5 axis origins;
Measuring a roll, which is an inclination defined based on the x direction of the robot base coordinate system by rotating the 5 axes by 90 °, and then registering the 4 axis origin by correcting the 4 axis error;
A method of calibrating a vertical articulated robot using a digital leveling system comprising a step of registering a six-axis origin by calibrating six-axis errors after measuring a roll by rotating five axes to 0 °. The process of claim 4, wherein the registration of the three-axis origin is performed.
Measuring pitch β _{+ 90} after rotating the four axes at 90 °;
Measuring pitch β- ₉₀ after rotating the four axes to −90 °;
Sum of pitch β _{+ 90} and pitch β _-90

Calculating a;

of

And rotating as much as possible and registering the state as an origin of three axes. The process of claim 4, wherein the registering of the 5-axis origin is performed.
Measuring pitch β ₀ after rotating the 4 axes to 0 °;
and rotating the θ ₅ by pitch β ₀ and registering the state as an origin of five axes. The process of claim 4, wherein the registering of the 4-axis origin is performed.
Measuring roll γ ₉₀ after rotating the five axes at 90 °;
and rotating the θ ₄ by a roll γ ₉₀ to register the state as an origin of four axes. The process of registering the six-axis origin of claim 4,
Measuring roll γ ₀ after rotating the 5-axis at 0 °;
and rotating the θ ₆ by roll γ ₀ to register the state as the origin of the six axes.

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