JPH0784618A - Method for setting up coordinate system of robot - Google Patents

Abstract

PURPOSE:To make it possible to quickly set up an optional coordinate system by simple operation without practically teaching plural points and to improve the safeness of operation and the accuracy of reproducing operation. CONSTITUTION:This setting method for an optional coordinate system 11 can set up a coordinate axis direction for indicating the operating direction of an articulated robot 1 having two degree of freedom or more capable of setting up optional position and posture to an optional direction and the coordinate system 11 can be set up by regarding the system 11 as an orthogonal coordinate system and inputting the value of a directional cosine in each axis direction of the system 11. The robot 1 is provided with a force sensor 4 for detecting force in a parallel advancement direction and force in the rotational direction at least in 2 axis directions on an arm head part, a coordinate axis direction for indicating the operating direction of the robot 1 can be set up to an optional direction by applying force for parallel advancement or rotation to two axis directions desired to be set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate system setting method for a robot, and more particularly to a coordinate system setting method which is easy to operate in an articulated robot that operates under force control and can set an arbitrary position and posture. Regarding

[0002]

2. Description of the Related Art As a conventional robot coordinate system setting method, for example, there is a robot control method disclosed in JP-A-61-49205. In this robot control system,
1 using 2 or 3 points in the robot absolute coordinate system
It contains a configuration that defines one local coordinate system, an arbitrary coordinate system.

[0003]

In the conventional method of setting an arbitrary coordinate system in the robot control system, it is necessary to teach the coordinates of two or three points while operating the robot body, which makes the operation complicated. . Further, there are cases where it is difficult to teach the coordinates of two or three points due to the installation position of the work. In such a case, it is impossible to set an arbitrary coordinate system, which is a problem. .

An object of the present invention is to set an arbitrary coordinate system by a simple operation in a short time without actually teaching a plurality of points, and further improve the safety of the operation and the accuracy of operation during reproduction. To provide a coordinate system setting method of.

[0005]

A robot coordinate system setting method according to the present invention is an articulated robot having two or more degrees of freedom capable of setting an arbitrary position and posture, and is used for instructing a movement direction of the robot. This is a method of setting an arbitrary coordinate system that allows the coordinate axis direction to be set in an arbitrary direction.The arbitrary coordinate system is set as a Cartesian coordinate system, and the arbitrary coordinate system is set by inputting the values of the direction cosine for each axis direction of the arbitrary coordinate system. How to set.

The robot coordinate system setting method according to the present invention is a multi-joint type robot having two or more degrees of freedom capable of setting an arbitrary position and posture, and a force in a translational direction is applied to the arm tip portion in at least two axial directions. This is a method of setting an arbitrary coordinate system that has a force sensor that detects the force in the direction of rotation and that allows setting the coordinate axis direction for instructing the movement direction of the robot in any direction. This is a method of setting an arbitrary coordinate system by applying the force of.

In the above method, the arbitrary coordinate system is preferably set by pushing in the two axial directions to be set.

In the above method, preferably, an arbitrary coordinate system is set by applying a rotational force in the two axial directions to be set.

Further, in the coordinate system setting method of the robot according to the present invention, an arbitrary coordinate system can be obtained by combining the above-mentioned coordinate system setting method by numerical input and the above-mentioned coordinate system setting method by applying respective forces. The feature is that it is set.

[0010]

In the robot coordinate system setting method according to the present invention,
In a robot equipped with a force sensor and force control means, it is not necessary to actually move the robot main body to a predetermined teaching point, and a predetermined numerical value is input using a teaching box based on the user's sensory judgment. An arbitrary coordinate system can be set by applying a force to the force sensor in the translational or rotational directions of at least two axes, and the setting of the arbitrary coordinate system is simplified.

[0011]

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

The configuration of the robot system to which the coordinate system setting method according to the present invention is applied will be described with reference to FIG.
In FIG. 4, 1 is a robot body attached to a base (pedestal) 3 and provided with an arm 2, 4 is a force sensor provided at the tip of the arm 2, and 5 is a controller for controlling the operation of the robot body 1. is there. The robot body 1 has a plurality of joints to form a mechanism having at least two degrees of freedom, and each joint has a built-in drive device. The robot main body 1 takes various postures by driving the driving device. An arbitrary work tool (generally, a hand effector) 6 is attached to the tip of the force sensor 4. The controller 5 is composed of a computer, and holds a program and control parameters necessary for controlling the operation of the robot body 1 in its storage device. The robot of this embodiment will be described as a force control robot including a force sensor and including a force control means in the controller. However, the coordinate system setting method according to the present invention is
It is not limited to force control robots.

In the robot, a base coordinate system 11 which is a coordinate system fixed to the base unit 3, a force sensor coordinate system 12 at the center of the force sensor 4, and an arbitrary coordinate determined by a unit vector represented by the base coordinate system 11. The system 13 is set. These coordinate systems 11, 12 and 13 are orthogonal coordinate systems in which three axes X, Y and Z are orthogonal to each other. The coordinate system setting method according to the present invention relates to this arbitrary coordinate system setting method, and 1) a setting method by inputting a numerical value, 2) a setting method by a pressing force (substantially the same even if a pulling force), 3) ) Rotational force setting method 4)
Four setting methods, that is, a setting method using a combination of a pressing force and a rotating force, are used.

First, a method of setting a coordinate system by inputting numerical values will be described with reference to FIGS.

In FIG. 1, reference numeral 21 is a teaching box having operation buttons and keys and an arbitrary coordinate system setting screen 21a.
The robot body 1 is taught by operating 1. The teaching content input in the teaching box 21 is set inside the controller 5. In the internal structure of the controller 5 shown in FIG. 1, only essential parts relevant to the gist of the present invention are shown. The controller 5 includes an arbitrary coordinate system data input processing unit 22, an arbitrary coordinate system data storage unit 2
3, a force control calculator 24 and a servo circuit 25 are included.
The arbitrary coordinate system data input processing unit 22 is for inputting data relating to the arbitrary coordinate system. The data input by the teaching box 21 and the arbitrary coordinate system data input processing unit 22 is stored in the arbitrary coordinate system data storage unit 23. The force control calculation unit 24 uses the data stored in the arbitrary coordinate system data storage unit 23 to perform coordinate conversion.

The structure and operation of the force control calculator 24 will be outlined. The force control calculation unit 24 has a built-in means for executing position and force control inside, and various types of control for executing position parameters and force control parameters prepared in advance according to the contents of work and virtual compliance control. Various control arithmetic expressions for generating parameters and control commands are set. In order for the force control calculation unit 24 to generate a control command, information regarding the actual position and force of the robot body 1 is required. The data regarding the position output from the position sensor (for example, the angle meter by the encoder) provided at each joint of the robot body 1 is input to the force control calculation unit 24 through the servo circuit 25. In addition, the data regarding the force output by the force sensor 4 described above also includes the force control calculation unit
Entered in. Based on the difference between the set position target value and the actual position of each part, and the difference between the set force target value and the actually detected force, and using various set control parameters and control arithmetic expressions. A control command is generated so that the target value is achieved. The generated control command is given to the drive device of each part of the robot body 1 via the servo circuit 25. For details, see Japanese Patent Application Laid-Open No. 1-2223.
No. 16 publication.

Next, a method of setting an arbitrary coordinate system will be described with reference to FIGS. 2 and 3. The process according to the flowchart shown in FIG. 2 is executed by the arbitrary coordinate system data input processing unit 22.

Step 31 is a step for inputting a numerical value. In step 31, the numerical value of each direction cosine is input as N vector in the X-axis direction, O vector in the Y-axis direction, and A vector in the Z-axis direction. The direction cosine of the N vector is N (Nx, Ny, Nz), the direction cosine of the O vector is O (Ox, Oy, Oz), and the direction cosine of the A vector is A (Ax, Ay, Az). Input is made by operating the operation keys of the box 21 and in the state as shown in the arbitrary coordinate system setting screen 21a shown in FIG. In the array of numerical values displayed on the arbitrary coordinate system setting screen 21a of the teaching box 21, the vertical arrangement is N, O, A, and the horizontal arrangement is each value in the X-axis direction, Y-axis direction, and Z-axis direction. Is. After inputting the respective values of N, O and A, an end button (not shown) is operated. When it is confirmed in the determination step 32 that the end button has been operated, the process proceeds to step 33. Step 3
Reference numeral 3 is a step for determining whether or not the input N and O form a pressing state in the correct direction. In step 33, the inner product of the N vector and the O vector is calculated, and this calculated value is set to a certain value α (about 0.001).
Compare the magnitude relationship with the value). In the comparison of step 33, when the calculated value is larger than α, the process moves to step 35, an error message is displayed, and the operator is urged to re-input. The operator who sees this error message performs re-entry, returns to step 31, and repeats steps 31 to 33 described above. If the calculated value is equal to or less than α in the comparison in step 33, the process moves to step 34 to calculate the vector A ′ based on the following (Equation 1).

[0019]

[Equation 1]

At the next step 36, the inner product of the vector A and the vector A'is calculated, and if the calculated value is not less than (1-ε) and not less than 1, an error message is displayed (step 35) and the process returns to step 31. Then, each value of N, O, A is input again. When the calculated value is greater than or equal to (1-ε) and less than or equal to 1 in step 36, the operation for setting the arbitrary coordinate system by inputting a numerical value ends. The arbitrary coordinate system thus set is the arbitrary coordinate system data storage unit 2
3 is stored. However, the worker actually works only by inputting the values of the vectors N, O, and A. The operator sets the arbitrary coordinate system setting screen 2 of the teaching box 21.
Work is performed according to the instruction content displayed in 1a.

As a modified example of the method of setting an arbitrary coordinate system by numerical input, a method of automatically calculating by (Equation 1) without requesting the input of the vector A in step 31, or a value of α in the judgment step 33 A method of setting a large value, obtaining the vector A by (Equation 1), and re-obtaining the vector O by (Equation 2) below can also be considered.

[0022]

[Equation 2]

Next, a method of setting the arbitrary coordinate system by the pressing force will be described with reference to FIGS.

First, in order to express the force value in the base coordinate system, the sensor coordinate system is changed to the axis angle data of each joint by the position sensor, that is, the encoder provided in each axis of the robot body 1 shown in FIG. As shown in FIG. 5, detection is performed via the encoder counter 25b, and the detected value is coordinate-converted by the coordinate conversion unit 26 to be obtained. Next, the pressing direction calculation unit 2
The arbitrary coordinate system is set by the calculation in 7 and is supplied to the arbitrary coordinate system data input processing unit 22. Servo circuit 25 shown in FIG.
Is the encoder counter 25b and the servo amplifier 2 described above.
5a is included. The force signal output by the force sensor 4 is input to the force control calculation unit 24 and the pressing force direction calculation unit 27. Other configurations are the same as those shown in FIG.

In step 41, the arbitrary coordinate system setting screen 21
Based on the pressing instruction in the Z-axis direction displayed in a,
The worker presses the work tool 6 mounted on the robot body 1 in the Z-axis direction. The pressing force in the Z-axis direction is detected by the force sensor 4 and input to the force control calculation unit 24 and the pressing direction calculation unit 27. After the pressing work is completed, press the end button. In step 42, it is confirmed whether or not the end button has been surely pressed. Next step 4
In 3, the force 28 applied in the Z-axis direction is taken in via the force sensor 4 and the pressing force direction calculation unit 27, and is input to the arbitrary coordinate system data input processing unit 22 as force data <Fz>. Here, “<>” represents a vector quantity.

Next, based on the Y-axis direction pressing instruction displayed on the arbitrary coordinate system setting screen 21a, the worker presses the work tool 6 mounted on the robot body 1 in the Y-axis direction (step 44). The pressing force in the Y-axis direction is also detected by the force sensor 4. After the pressing work is completed, press the end button. In step 45, it is confirmed whether or not the end button has been surely pressed. Then in step 46, Y
The force 29 applied in the axial direction is taken in via the force sensor 4 and the pressing force direction calculation unit 27, and is input to the arbitrary coordinate system data input processing unit 22 as force data <Fy>.

Next, using the force data <Fz> and <Fy>, the respective unit vectors Z and Y'are calculated by the following equation (step 47).

[0028]

[Equation 3]

Next, in order to determine whether or not the force is correctly pressed in each of the Z-axis and Y-axis directions, the inner product of each unit vector calculated in (Equation 3) is calculated, and the calculated value is set. The calculated value β (about 0.7) is compared with its magnitude relationship (step 48). When the calculated inner product is greater than or equal to the arbitrary value β, an error message indicating the pressing direction error is displayed (step 49), and the process returns to step 44 and Y
Axial pressing is performed again and the above steps are repeated. When the calculated value of the inner product is smaller than the arbitrary value β in step 48, the following (Equation 4) is performed in step 50.

[0030]

[Equation 4]

As described above, the setting of the arbitrary coordinate system by the pressing force is completed. The set arbitrary coordinate system is stored in the arbitrary coordinate system data storage unit 23. However, the worker actually works only by pressing in the Z-axis direction and the Y-axis direction.

In the above embodiment, the force sensor 4 can be pulled instead of being pushed. In addition, when performing the method of setting the arbitrary coordinate system by the rotational force, the work tool 6
By applying a rotational force to the set axial direction and detecting the rotational force with the force sensor 4, the same processing as described above is performed,
An arbitrary coordinate system can be set. It should be noted that the force sensor 4 can detect the rotation torque. A dedicated torque sensor can be used instead of the force sensor 4.

Next, a method of setting the arbitrary coordinate system by the rotational force and the pressing force will be described with reference to FIGS. 7 and 8. Basically, it is the same as the method of setting the arbitrary coordinate system only by the pressing force described above. The difference is that instead of applying the pressing force in the Z-axis direction in steps 41 and 42, the rotational force around the Z-axis is 3
This is the point where 0 is added, and the force (moment) data <Mz> relating to the rotational force in the Z-axis direction is input in step 43. The contents of the other calculation processing and determination processing are substantially the same. In this way, the method of setting the arbitrary coordinate system by the rotational force and the pressing force is performed.

In each of the above-mentioned embodiments, the instruction of pressing in each axial direction and the instruction of the rotational force about the axis are merely examples, and the translational force (pressing force) in each axial direction of X, Y, Z. Or a pulling force), and an arbitrary combination of rotational forces around the respective axes.

It is also possible to generate a reaction force in the work tool by turning on a switch for operating the work tool, thereby giving a rotational force.

Further, a setting method of an arbitrary coordinate system can be configured by appropriately combining the coordinate system setting methods utilizing the numerical value input, the pressing force (pulling force), and the rotating force described above. In particular, the coordinate system setting method, which combines the method of inputting numerical values and the method of using pressing force and rotating force, makes it possible to set based on the independence of the operator, and is a desirable method in actual work. .

[0037]

As is apparent from the above description, according to the present invention, it is possible to set an arbitrary coordinate system by directly inputting numerical values, and therefore it is possible to easily set the arbitrary coordinate system. it can. Further, regarding a robot provided with a force sensor, an arbitrary coordinate system can be set by applying a required pressing force (may be pulling force) or rotational force to at least two axis directions to the force sensor. The coordinate system setting work can be performed, the work is safe, and the coordinate system setting can be performed with high accuracy. The coordinate system setting method, which is a combination of a method of using a numerical input and a method of using a pressing force, has the advantage of being convenient in an actual field.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a robot controller that implements a coordinate system setting method by numerical input.

FIG. 2 is a flowchart showing a coordinate system setting method by numerical input.

FIG. 3 is a diagram showing a display screen of a teaching box.

FIG. 4 is a diagram showing a configuration of a robot body and a coordinate system to be set.

FIG. 5 is a block diagram showing a configuration of a robot controller that implements a coordinate system setting method by pressing force.

FIG. 6 is a diagram showing a configuration of a robot body and a coordinate system to be set when a pressing force is applied.

FIG. 7 is a flowchart showing a coordinate system setting method by pressing force.

FIG. 8 is a diagram showing a configuration of a robot main body and a coordinate system to be set when a pressing force and a rotational force are applied.

[Explanation of symbols]

 1 Robot Main Body 2 Arm 4 Force Sensor 5 Controller 6 Work Tool 11 Base Coordinate System 12 Sensor Coordinate System 13 Arbitrary Coordinate System 21 Teaching Box 22 Arbitrary Coordinate System Data Input Processor 23 Arbitrary Coordinate System Data Storage 24 Force Control Calculator 26 Coordinates Conversion unit 27 Pressing force direction calculation unit

Claims (5)

[Claims] 1. A multi-joint robot having two or more degrees of freedom that can be set to an arbitrary position and orientation, and an arbitrary coordinate system that can set an arbitrary coordinate axis direction for instructing the movement direction of the robot. In the method, the arbitrary coordinate system is an orthogonal coordinate system, and the arbitrary coordinate system is set by inputting a numerical value of a direction cosine for each axial direction of the arbitrary coordinate system. System setting method. 2. A multi-joint robot having two or more degrees of freedom that can be set to an arbitrary position and posture, and a force sensor for detecting a force in a translational direction and a force in a rotational direction in at least two axial directions at an arm tip portion. In the method of setting an arbitrary coordinate system, wherein the coordinate axis direction for instructing the movement direction of the robot can be set to an arbitrary direction, the arbitrary coordinate system is applied by applying a translational or rotational force in the two axial directions to be set. A method for setting the coordinate system of a robot, characterized in that 3. The robot coordinate system setting method according to claim 2, wherein the arbitrary coordinate system is set by pushing a force in the two axial directions to be set. Setting method. 4. The robot coordinate system setting method according to claim 2, wherein the arbitrary coordinate system is set by applying a rotational force in the two axial directions to be set. System setting method. 5. A combination of the coordinate system setting method by numerical input according to claim 1 and the coordinate system setting method by applying a force according to any one of claims 2 to 4. A method for setting a coordinate system of a robot, characterized in that an arbitrary coordinate system is set.