JPH0760607A - Automatic tcp setting method - Google Patents

Abstract

PURPOSE:To eliminate labor to set a TCP (tool center point), and shorten setting time by setting the point automatically as the TCP only by applying forces to a point desired to set as the TCP in two directions by an operator. CONSTITUTION:When a TCP is set, first of all, a point desired to be set as the TCP is determined in a grinding wheel 6a of a grinder 6 by an operator. That is, a point A positioned on the edge of the grinding wheel 6a is determined as the point desired to be set as the TCP. Next, forces 11 and 12 are applied in two directions considered as orthodonal to each other at the point A by fingers or the like, and the respective forces 11 and 12 are detected by a sensor 4 on the robot body side, and about the applied forces, a straight line containing them is calculated by a controller according to a detected force signal. The Z axis and the Y axis are determined according to the respective orthogonal forces, and the X axis is determined by operation of the outer product according to orthogonal coordinates of a right hand system. A posture (that is, a coordiante system in a grinding tool) can be set by this operation with the point A as the TCP.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TCP automatic setting method, and more particularly to a TCP automatic setting method used in a force control robot.

[0002]

2. Description of the Related Art A force control robot is a robot that performs force control together with position control when performing work, and can perform work involving force. A grinding robot can be cited as an example of a conventional force control robot. The grinding robot is equipped with a force sensor on a wrist located at the tip of an arm of a robot body, and a grinding tool (generally a work tool) is attached to the tip of the force sensor. The grinding tool is
For example, a grinder provided with a grindstone. Further, the force sensor has a function of detecting a force and a moment which the grinding tool receives from the grinding object when the grinding tool contacts the grinding object and performs grinding, for example, and is a six-axis force sensor. The force information obtained through the force sensor is used as actual force data when the force element is controlled by the control means.

In the force control robot, the T
CP (TOOL Center Point) is set. This TCP is a point set on the grinding tool (on the coordinate system defined by the grinding tool), and is set based on the position and orientation. As TCP, the grinding point of the grindstone that contacts the object to be ground is used.

[0004]

According to the conventional TCP setting, which position is from the reference position of the robot in each axial direction of the coordinate system X, Y, Z of the robot hand and what is its posture? For the position, the distance was actually measured with a ruler, for the posture, the mounting angle of the grindstone was calculated, and the obtained numerical value was manually input by operating the key input pendant to set it. Conventional TCP
However, the setting method described above has a problem in that it is difficult to set the TCP correctly because the values may be wrong.

An object of the present invention is to provide an automatic TCP setting method which can easily set a TCP in a force control robot in a short time.

[0006]

The automatic TCP setting method according to the present invention is a method applied to a force control robot in which a work tool is attached to the tip of an articulated robot body via a force sensor. , Determine a point to be TCP in the work tool, apply a force in the first direction at the point, apply a force in the second direction substantially orthogonal to the first direction at the point, and output the force sensor The first straight line including the first direction is obtained based on the signal relating to the force in the first direction, and the second straight line including the second direction is obtained based on the signal relating to the force in the second direction output from the force sensor. A straight line is determined, the position of the point is determined based on the first and second straight lines, and a third straight line orthogonal to the two straight lines is determined. The position of the point and the first to third straight lines are defined. TCP is set with the coordinate system of three orthogonal axes.

In the above method, preferably, a straight line that replaces the second straight line is obtained based on the first and third straight lines, and the first and third straight lines and the newly obtained straight line Define a coordinate system with three axes.

In the above method, preferably, it is the operator who applies the force at the point in the first and second directions.

[0009]

In the automatic TCP setting method according to the present invention, when the operator defines a point to be TCP in the work tool and adds it in the first and second directions orthogonal to that point, the controller on the robot side A first straight line including the first direction and a second straight line including the second direction are obtained based on the force signal output from the force sensor, and the position of the point is determined based on the first and second straight lines. A third straight line that is orthogonal to the two straight lines is obtained, the position and orientation of the point are obtained, and TCP is automatically set. When the condition that the first straight line and the second straight line are orthogonal to each other is not satisfied, the first straight line and the third straight line are used to obtain a straight line that is orthogonal to the two, and the second straight line is obtained.
Use as a straight line. In this way, the three orthogonal axes X, Y,
A coordinate system composed of Z is generated and used as a posture.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a side view of the arm tip of a force control robot such as a grinding robot, and FIG. 2 is a front view of the arm tip. 1 and 2, a force sensor 4 is attached to a wrist portion 2 of an arm 1 of an articulated robot body (not shown) via an attachment plate 3. The mechanism of the articulated robot body is well known. The force sensor 4 is a 6-axis force sensor and has a function of sensing forces in each direction of three orthogonal X, Y, and Z axes and a moment about each axis. A grinder 6 as a grinding tool is further attached to the tip of the force sensor 4 by a grinder holder 5. The grindstone 6a is attached to the rotary drive shaft of the grinder 6. Therefore, the force and moment applied to the grindstone 6a and the grinder 6 can be detected by the force sensor 4.

As shown in FIG. 1, the robot main body having the above-mentioned configuration has a controller 7. Controller 7
Is generally composed of a computer system. The controller 7 has various data processing functions, arithmetic functions, and control functions related to the operation of the robot body. For example, the controller 7 sets the teaching data for the grinding work in the internal storage device when direct teaching is performed on the robot body, and when the grinding work is performed, the teaching data is read and ground. It has a function of setting a work execution unit or executing a grinding work based on teaching data and force and position data detected during the work. For that purpose, the controller 7 gives a drive command signal 7a to each joint driving unit of the robot body, and also outputs a position signal 7b from a position sensor such as an encoder provided in each joint driving unit and the force sensor 4 described above. From the force signals 7c. The controller 7 further has a function of automatically calculating TCP by performing a predetermined calculation by using an output signal of the force sensor 4 generated by a predetermined operation described later. The operation required to automatically obtain TCP is performed by the operator according to the instruction content displayed on the display 8a of the teaching device 8. In the teaching device 8, 8b is an input operation key.

Next, a TCP setting method will be described with reference to FIG. In FIG. 3, similarly to FIG. 1, 4 is a force sensor, 6 is a grinder, and 6a is a grindstone. The grinder holder 5 is shown diagrammatically in a simplified manner, and 6b is a rotary drive shaft of the grinder 6.

In the TCP setting, the position and orientation of the point that should become TCP must be determined. TC of the present invention
In the P setting method, first, the operator uses the TCP on the grindstone 6a.
Determine the points you want to take. In the embodiment shown in FIG. 3, on the operator side, the point A located at the edge of the grindstone 6a is defined as the point to be TCP. Next, the worker applies a force with his / her finger or the like in two directions which are considered to be orthogonal at the point A. In this embodiment, as shown in FIG. 3, a force 11 in the Z-axis direction and a force 12 in the Y-axis direction are applied to the point A.

The actual operation relating to the TCP automatic setting method will be described in detail. TCP is displayed on the display 8a of the teaching device 8.
Is displayed, a message "please press the direction you want to press" is displayed. Therefore, the operator sets the point A to TCP.
Then, the point A is pushed in the direction indicated by the force 11. On the side of the robot body, the force 11 is detected by the force sensor 4, and the controller 7 detects the force 1 based on the force signal 7c output from the force sensor 4.
For 1, the straight line containing it is calculated. The straight line equation is
It is calculated by the force value and the moment value that can be detected by the force sensor 4. In the robot body, a straight line determined by the force 11 is temporarily determined as the Z axis, for example. The operator can also decide which axis to use. Next, the message "Please push in the direction you want to make the Y-axis" is displayed on the display 8a of the teaching device 8. Then, the operator pushes the point A in the direction indicated by the force 12. Direction of force 12 is force 1
It is made as orthogonal as possible to the direction of 1. On the side of the robot body, the force 12 is detected by the force sensor 4, and the controller 7 detects the force 1 based on the force signal 7c output from the force sensor 4.
With respect to 2, a straight line including it is calculated. In the controller 7, when the Z-axis and the Y-axis are determined based on the force 11 and the force 12, the X-axis is also determined by calculating the outer product based on the right-handed orthogonal coordinates. The + and-directions on each axis are
By defining the direction in which the force is applied at point A as +, the directions of the X, Y, and Z axes are determined.

By the above operation, the attitude (that is, the coordinate system in the grinding tool) is set with the point A as TCP. The position of TCP can be calculated, for example, as the intersection of the straight line representing the Z axis and the straight line representing the Y axis. In this way, the position and orientation of point A are determined, and point A
It can be set as a CP.

With reference to the flow chart shown in FIG. 4, only the attitude setting of the automatic TCP setting method according to the present invention will be focused on and further described. As described above, as the input operation of the operator, the force 11 is applied to the point A of the grindstone 6a (step S1), and then the force 12 is applied to the point A (step S2). It is desirable that the angle formed by the forces 11 and 12 be exactly 90 °, but it is 90 ° because it is done by a human.
Is difficult to do. Therefore, in the determination step S3, the angle formed by the forces 11 and 12 is a predetermined condition, that is, 90 °.
If the condition of being included in the range of ± β is satisfied, force 11
And force 12 are treated as being orthogonal to each other, and the process proceeds to step S4. Unless this condition is satisfied, steps S2 and S
3 is repeated. While steps S2 and S3 are repeated, a message is repeated on the display 8a of the teaching device 8 so as to apply a force to the operator in the orthogonal axis direction again. The worker applies force according to the message so that the above conditions are satisfied.

In step S4, a straight line about the X axis is obtained as an outer product based on the Z axis and the Y axis obtained by the forces 11 and 12. Further, in the next step S5, based on the obtained straight line about the X-axis and the Z-axis obtained by the force 11, the Y-axis orthogonal to the Z-axis is accurately calculated again. In this way, after applying the force 11 in the Z-axis direction at the point A, the point A is set as the temporary Y-axis direction in the direction satisfying the predetermined condition.
Then, a force 12 is applied to obtain an X axis orthogonal to both axes based on the obtained Z axis and temporary Y axis. After that, an accurate Y axis is obtained again from the Z axis and the X axis which are orthogonal to each other. In this way, the coordinate system as the posture is accurately obtained. In the final step S6, the determined position and orientation are changed to the teaching device 8
Is displayed on the display 8a.

In the TCP automatic setting method described above, force 11
It is premised that the point to which the force 12 is applied is the same point A on the grindstone 6a. When the force 11 is applied to the grindstone 6a, a linear equation including the direction in which the force 11 is applied is obtained. When force 12 is applied to the grindstone 6a, force 1
An equation of a straight line including the direction obtained by adding 2 is obtained. TC
The position of the point A, which is P, is obtained as the intersection of two straight lines based on the above equation of the two straight lines. However, when the points to which the forces 11 and 12 are applied are different in obtaining each straight line, the intersection of the two straight lines cannot be obtained. Therefore, in such a case, for example, 2
Find the shortest line segment that connects two straight lines, and set the midpoint of the line segment to T
It can also be set as the position of the CP.

[0020]

As is apparent from the above description, according to the present invention, an operator can automatically set a point that he / she wants to use as TCP by applying force in two directions. , TCP can be saved and the setting time can be shortened.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a tip portion of a robot body and a related control unit.

FIG. 2 is a front view of the tip of the robot body.

FIG. 3 is a diagram showing a state in which a force is applied to a grindstone.

FIG. 4 is a flowchart showing a TCP automatic setting method according to the present invention.

[Explanation of symbols]

 1 arm 2 wrist part 4 force sensor 6 grinder 6a grindstone 7 controller 8 teaching device 8a indicator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B25J 19/00 Z G05B 19/42

Claims (3)

[Claims] 1. A TCP automatic setting method applied to a force control robot in which a work tool is attached to a tip portion of an articulated robot main body via a force sensor, and points to be set in the work tool are TCP. The force in the first direction at the point, the force in the second direction substantially orthogonal to the first direction at the point, and the force in the first direction output by the force sensor. A first straight line including the first direction based on a signal related to the second direction, and a second straight line including the second direction based on a signal related to the force in the second direction output from the force sensor. , A third straight line orthogonal to the two straight lines is obtained based on the first and second straight lines, and the position of the point and the first to third straight lines are defined. Set the TCP with the coordinate system of three orthogonal axes. An automatic TCP setting method characterized by the above. 2. The automatic TCP setting method according to claim 1, wherein the second line is based on the first and third straight lines.
An automatic TCP setting method is characterized in that a straight line that replaces the straight line is obtained, and the coordinate systems of the three axes are defined by the first and third straight lines and the newly obtained straight line. 3. The automatic TCP setting method according to claim 1, wherein an operator applies the force in the first and second directions at the point.