JPS5958504A - Origin offset adjusting method for arthrosis type robot - Google Patents

Abstract

PURPOSE:To find an origin offset easily and automatically by operating and teaching a robot so that a meter installed at the tip end of the robot indicates the same value at four optional different points in respective measurement planes. CONSTITUTION:A micrometer is attached to the tip end of the robot to measure (n-1) mutually different planes (n; degree of freedom of robot). Further, measurements are taken at four properly distant points in respective planes. Then, all of angles obtained by an angle detector at respective attitudes are stored in a storage device 10 and substituted in an equation and a calculating device 11 calculates an angle offset. The calculated angle offset is corrected by a correcting device 11 and a track taught to the robot is realized by an executing device 15.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The invention relates to a method for automatically adjusting the origin offset of an articulated robot.

Conventional Structure and Problems Conventionally, FTP control has been used for robot positioning control. Therefore, the deviation of the robot's origin poses a problem in position reproducibility. However, even if the reproducibility varies among individual robots, it is sufficient that the reproducibility is stable for each robot.

The next problem is how to control points between points using FTP *U control. This control method is interpolation. When interpolation is performed by a computer, the robot's positional accuracy is determined by the following two factors: (1) Mechanical deviation measurement, and (2) Calculation accuracy of the computer. It is not difficult to eliminate the factor (■). However, it has traditionally been difficult to eliminate the factor (2) due to the following two factors.

■ The center of rotation and center of bending cannot be accurately determined from the top and outside of the machine.

@ It is not possible to detect minute angles with ordinary instruments.

Because of these problems, it is necessary to use some auxiliary means to determine the mechanical deflection from data collected by some auxiliary means.

Purpose of the Invention The present invention provides a method for adjusting the origin offset of an articulated robot, which allows the origin offset to be easily and automatically determined and eliminates the wasted time of carefully aligning the origin of each axis as in the conventional method. It is to be.

Structure of the Invention The present invention is a method for adjusting the origin offset of an articulated robot having n degrees of freedom (n is a positive integer), in which (n-1) different planes are used as measurement planes, and each Draw the micrometer installed at the tip of the robot at four arbitrary different points on the measurement plane in a posture that is approximately perpendicular to the measurement plane, so that the indicated values of the micrometer at these four points are the same value. The robot is operated and taught, and the error formula of the tip coordinate determined by the set point system fixed to the robot [δE] The error of the robot tip position due to p angle offset [P]; Angle offset and robot tip position This method calculates and adjusts the origin offset from a matrix of constants determined by the error of .

DESCRIPTION OF EMBODIMENTS Offsets can be divided into (1) angular offsets and (2) length offsets. Since the amount of error in the length offset that affects the tip trajectory is smaller than that in the angular offset, it is sufficient to mainly find the angular offset.

Here, if an arbitrary joint angle θ is taken as a reference, that is, if the angle offset δθ□=O for a joint angle 0□, then the degree of freedom for the angle offset will be reduced by one.

Now, let E be the tip of the robot with n degrees of freedom considering the offset, express it in a Cartesian system, and perform tiller expansion. Assuming that the terms of θ0.2nd order and above are extremely small and therefore ignored as the basis for the angular offset, the relationship between the position error of the robot tip and the angular offset is expressed as a linear simultaneous equation [JE]; the robot tip position error vector caused by the angular offset. [Q]: If the angular offset vector can be expressed in the form of a matrix [F] formula that expresses the relationship between the angular offset and the tip position error when the angle θ is used as the reference angle, the angular offset vector can be easily determined.

Next, we will describe how to obtain the coefficient matrix corresponding to [Q] in equation 1).

A micrometer is attached to the tip E of the robot, and (n-1) different planes are measured. n is the robot's degree of freedom. Furthermore, measurements are taken at four appropriately spaced points on each plane. At these four points, the micrometer is applied in a direction substantially perpendicular to the measurement plane, and the micrometer's indication is transmitted to the control device shown in FIG. 2 as the same position. This control device will be explained later.

FIG. 1 shows the measurement plane teaching operation. In the figure, 1 is a surface plate, 2 is a right-angled surface plate, 3 is a micrometer,
4 is the tip of the robot.

1 The four points on the measuring head surface are A1. A2. A3, A4, a.

b, c a　　　A2　A1 b-A3-Al c=A4-A1 shall be. However, the arrow above the symbol means a vector.

Since the vectors a, b, and c obtained from the measurement points include offsets, they can be written as a=a+Δa b=b+Δb CC+ΔC. However, 71, El, and τ' are vectors obtained from the angle detection device, and Δa, Δb, and ΔC are vectors shifted due to offsets.

Here, A1. A2. From the condition that A3 is on the same plane and the terms of quadratic and higher order are minute and therefore omitted, 0 = (Ma'
+(?'XΔ bean')・7'+(a'Xb'n・Δ
C...... ■ The relational expression - is obtained.

Since there are (n-1) measurement planes, one data of each measurement plane is entered into equation (2), and the angle offset δθ3. When rearranged by ・, δθ□, it becomes .

Here, q-1,..., (n-1)+ q-+, , qT, , q-+, ; Vector for measuring plane q [-(qTt x q10')・Q-), ] , the relationship matrix between the Nuka 2B multiplicity [K] of each measurement plane, the angle offset and the Nuka 23 multiplication of each measurement plane.It is possible to obtain the angle offset using the equation (2).

FIG. 2 shows the control device. 5 is a robot body, 6 is a device for controlling the robot, 7 is a teaching device for making the robot take a desired posture, and 8 is a device for displaying the absolute coordinate position of the tip of the robot in a system such as a Cartesian system.

FIG. 3 shows the flow of processing in this case.

9 is a teaching device that teaches the posture required to find the angle off-seratra by 4 x (degrees of freedom of the robot n-1) on the measurement plane; 10 is each posture at that time, and stores all the angles obtained from the angle detection device. 11 is a storage device l
This is a calculation device that calculates the angle offset by substituting the angle stored in 0 into the 0 equation. Through the processing up to this point, the angular offset required for robot trajectory control is determined.

Therefore, all you have to do next is teach the robot the trajectory you want it to move. 12 is a teaching device that brings the tip of the robot to a teaching point on the trajectory that you want to move, 13 is a storage device that obtains and stores the joint angle with respect to the teaching point on the trajectory from the angle detection device, and 14 is the angle calculated by the calculation device 11. Add the offset to the joint angle obtained in the storage device 13, or
A correction device 15 is an execution device that inputs the corrected angle into a control device and causes the robot to realize the trajectory taught.

It should be noted here that the processing of devices 9 to 12 is performed when the robot is started, and there is no need to calculate the origin offset If every time the robot is taught a trajectory.

Effects of the Invention As described above, according to the present invention, the origin offset can be found extremely easily and automatically, and the problem of origin offset, which has been considered difficult in the past, can be solved. Furthermore, there is an effect that the time wasted in carefully aligning the origin of each axis as in the conventional method is eliminated, and trajectory control can be performed with good judgment.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the measurement plane teaching operation in an embodiment of the present invention, FIG. 2 is a schematic explanatory diagram of the control device, and FIG. 3 is an explanatory diagram showing the flow of the origin offset processing. . 1... Surface plate serving as a stand, 2... Right-angled surface plate, 3... Micrometer, 4... Tip of robot, 5... Main body of robot, 6... Control device, 7... Teaching device, 8...
-Display device, 9...teaching device, 10...storage device,
DESCRIPTION OF SYMBOLS 11... Angle offset calculating device, 12... Teaching device, 13... Storage device, 14... Correction device, 15... Execution device Fig. 2, Fig. 3

Claims (1)

[Scope of Claims] A method for adjusting the origin off-nut of an articulated robot having n (n is a positive integer) degrees of freedom, which are different from each other (n
-1) A micrometer installed at the tip of the robot is applied to four arbitrary different points on each measurement plane in an attitude substantially perpendicular to the measurement plane,
The robot is taught so that the micrometer readings at these four points are the same, and the tip coordinate error formula [δ
E]; Error vector of robot tip position caused by angular offset [P]; Origin offset of an articulated robot, characterized in that the origin offset is requested and adjusted from a matrix of constants determined by the angular offset and the error in the robot tip position. Adjustment method.