JPS623307A - Method for correcting mechanical original point of horizontal multi-joint robot - Google Patents

Abstract

PURPOSE:To correct the mechanical original point of a robot through the numerical control without having no mechanical change, by positioning the robot at a point in a working rage and calculating the shift of a revolving angle in a reset mode to the mechanical original point based on only the revolving angle of an arm which is read when the robot is positioned. CONSTITUTION:The right and left arms are used for positioning of a robot when the turning angle of the 2nd arm is positive and negative centering on the mechanical original point respectively. In this case, the actual revolving angles of the 2nd arm are st at theta2R and theta2L with right and left arms respectively. Then, theta2R=theta2L, phi2R=theta2R-DELTAtheta and phi2L=theta2L-DELTAtheta are defined as phi2R and phi2L respectively. Therefore DELTAtheta=-(phi2R+phi2L)/2 is obtained. Thus the numerical controller stores the angle information on the 2nd arm obtained when the robot is at a certain point by means of the right and left arms. Then a shift amount DELTAthetacan be obtained with the mechanical original point from said angle informa tion.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for correcting a mechanical origin in a horizontal articulated robot.

Conventional technology In recent years, the number of tasks using articulated robots has increased, but in order for an articulated robot to accurately position itself at a certain point in a Cartesian coordinate system, it is necessary to accurately measure the angle between adjacent arms. Must. Furthermore, if this angle measurement is not accurate, linear interpolation will not be performed with high precision, making CP control (continuance path control, hereinafter abbreviated as CP control) and palletizing functions impossible.

Once the angle between the arms is accurately measured at a certain reference point, the rotation angle can then be measured accurately using a sensor such as a rotary encoder.

However, since the conventional method uses the origin signal for each rotation of the limit switch and rotary encoder, the position of the reference point depends on the accuracy of the position of the sensor such as the limit switch and rotary encoder. Therefore, it is extremely difficult to accurately measure the angle between the arms.0 Below, with reference to the drawings, the above-mentioned conventional method for detecting the mechanical origin of an articulated robot will be described by way of example.

FIG. 4 is an external view of the horizontal articulated robot, and by rotating the first arm 1 and the second arm 2, the position of the workpiece 3 attached to the tip of the second arm is controlled.

Further, FIG. 5 is a schematic diagram of the arm portion, and the rotation angle θ1 of the first arm 1 and the rotation angle θ2 of the second arm are set as shown in the figure. Here, 04 and θ2 are positive for counterclockwise rotation, and the position of the workpiece 3 when the first arm 4 and second arm 2 are on a straight line is 01 = θ220 at the machine origin, so this The machine origin must be accurately recognized by the numerical control device.

FIG. 6 is a principle diagram of a conventional mechanical origin detection method using a limit switch. The light shielding plate 4 is interlocked with the rotation of the second arm 2, and after it unblocks the light receiving surface of the limit switch 6, it detects the rotation angle when the origin signal of each revolution of the rotary encoder directly connected to the drive motor is detected. In the numerical control device, θ2=o.

However, in this case, depending on the accuracy of the mounting of the limit switch and rotary encoder, in reality, as shown in FIG. 7, when returning to the mechanical home position, θ2=Δθ instead of θ2=o.

Therefore, if the rotation angles of the first arm 1 and the second arm 2 recognized by the numerical control device are ψ4 and ψ2, respectively, and the arm lengths are r4 and r2, respectively, then the warp position in the orthogonal coordinates is If the center of rotation of the first arm 1 is the coordinate work point, and the direction of the first arm 1 when returning to the mechanical origin is the y-axis direction, then q1==ψ4, θ2=ψ2+Δθ.

In other words, there is a deviation in positioning due to Δθ, and even if the numerical control device performs linear interpolation using ψ4 and ψ2,
The trajectory of the workpiece will not be a straight line.

Conventionally, in order to correct this Δθ, it was necessary to change the positions of the limit switch and rotary encoder.

Problems to be Solved by the Invention However, in order to mechanically correct Δθ in this way, it is necessary to install the limit switch and rotary encoder with extremely high precision, which is difficult and impractical. There was a problem that.

The present invention solves the above-mentioned problems by making it possible to calculate Δθ and correct the origin using a simple movement of the robot while using the conventional mechanism for detecting the mechanical origin.

Means for solving the problem In order to solve the above problem, the mechanical origin correction method of the present invention performs positioning at a certain point within the operating range, and at that time, only the rotation angle of the arm read by the numerical control device is used. The system is equipped with a configuration that calculates Δθ based on this and performs origin correction.

Functions In the present invention, the functions described above are as follows.

That is, the deviation of the origin can be calculated using only highly accurate angle information from the rotary encoder without using uncertain values such as the length of the arm.

Furthermore, since linear interpolation can be performed with high precision, CP control and palletizing functions can be performed with high precision.

Furthermore, since it is very easy to operate and does not require any skill, it also helps improve work efficiency.

EXAMPLE Hereinafter, a mechanical origin correction method according to an example of the present invention will be described with reference to the drawings.

FIG. 3 shows an example of the configuration of a robot drive control device using a mechanical origin correction method according to an embodiment of the present invention. e is an arm angle measuring device, and 7 is a robot numerical control device.

The above embodiment will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows the principle of measuring the deviation Δθ of the mechanical origin using only arm angle information read by the numerical control device 7 when positioning is performed at a certain point P using two methods. Now, when the rotation angle of the second arm is positive with respect to the machine origin, it is called positioning by the right arm, and when it is negative, it is called positioning by the left arm. The actual rotation angle of the second arm when positioning is performed using the right arm and left arm is 02R, respectively.
1θ2Ll and the values recognized by the numerical control device are each ψ2R
If 1ψ2L, then the following relational expression is obtained.0 From this, the following relational expression is obtained.

Δθ=-(ψ2R+ψ2L)/2 As a result, the numerical control device can store the angle information of the second arm when positioning the right and left arms at a certain point, and calculate the deviation Δθ of the mechanical origin from that value. can.

Based on the above principles, the second method for performing mechanical origin correction is
This will be explained along the flowchart shown in the figure. First, in step 1, when the mechanical origin is on the straight line between the first arm 1 and the second arm 2, the angle information obtained by the numerical control device 7 in that case is (θ4, θ2) = (0, 0). Define that there is. In step 2, a home return signal is issued from the numerical controller to return the robot to the home position. In step 3, the angle information is read from the arm angle measuring device 6 to the numerical control device (θ4
, θ2)=(0,0). In step 4, the robot is positioned with the right arm at a certain point within the operating range by teaching. In step 6, the angle information θ2-θ2R at the time of positioning in step 4 is read from the arm angle measuring device 6 into the numerical control device 7 and stored. Next step 6.
At 7, teach to the same point with the left arm in the same way as the right arm, θ2=
Read and store θ2L. In step 8, from the angle information obtained in step 6.7, Δθ= (2R+θ2
Δθ is calculated from the relational expression L)/2. In step 9, the rotation angle of the arm after returning to the origin stored in step 3 is changed and stored as (θ4, θ2)=(otΔθ).

As described above, according to this embodiment, when performing normal positioning, the numerical control device performs positioning by correcting the rotation angle of the second arm by Δθ, and also when performing linear interpolation etc. Highly accurate positioning is possible by performing calculations while correcting only Δθ.

Effects of the Invention As described above, the present invention measures the deviation from the mechanical origin that occurs when returning to the origin by using only the angle information read into the numerical control device from the arm angle measuring device without making any mechanical changes. By using a mechanical origin correction method that does not require the same skill as conventional methods, relatively simple and highly accurate mechanical origin correction can be performed without impairing workability.

Further, this machine origin correction allows positioning and linear interpolation to be performed with high precision, so that CP control and palletizing functions can be performed with high precision.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of calculating the deviation Δθ in an embodiment of the present invention, Fig. 2 is a flowchart of the mechanical origin correction method based on the principle, Fig. 3 is a block diagram of the embodiment, and Fig. 4 is a horizontal External view of the articulated robot, Figure 6 is a schematic diagram of the arm part,
FIG. 6 is a principle diagram of a conventional mechanical origin detection method, and FIG. 7 is an explanatory diagram showing the deviation from the mechanical origin during return to origin. 1...First arm, 2...Second arm, 3...Workpiece, 4...Shade plate, 6...
... Limit switch, 6 ... Arm angle measuring device, 7 ... Numerical control device. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] A symmetrical arm mechanism that allows two methods for positioning at a certain point by interlocking the first and second arms of a horizontal articulated robot; using an arm angle measuring device that measures the rotation angle of the second arm, and a numerical control device that reads the angle of the arm measured by the arm angle measuring device and controls positioning;
As a method of determining the difference Δθ between the angle information when the robot returns to its mechanical origin, which is measured by the arm angle measuring device and read into the numerical control device, and the actual angle between the arms, the rotation angle of the first arm and the second arm is determined. are respectively θ_1 and θ_
2, the machine origin is the case where the first arm and the second arm are on a straight line, and the rotation angle of the arm at that time is (θ_1, θ
_2) = (0, 0) and (1) step of returning the robot to the mechanical origin (2) the rotation angle of the arm when executing step 1 is (θ_1, θ_2) = (0, 0) (3) Step of positioning the second arm by rotating it counterclockwise from the mechanical origin to a certain point within the operating range. (4) Storing the angle information from the arm angle measuring device when step 3 is executed. Step of reading θ_2=θ_2_1 into the numerical control device (5) Step of positioning by rotating the second arm clockwise from the machine origin to the positioning point of step 3 (6) Step of reading θ_2=θ_2_2 in the same way as step 4 (7) Angle information θ_2 obtained from step 4 and step 6
Using _1, θ_2_2, calculate Δθ from Δθ=-(θ_2_1+θ_2_2)/2 (8) Change the arm rotation angle in step 2 to (θ_4, θ_2)=(0, Δθ) and define A method for correcting the mechanical origin of a horizontal articulated robot, characterized by comprising: