JPH0655485A - Arm inclination amount measuring device of articulated robot - Google Patents

Abstract

PURPOSE:To correct the error amount generated by the bending of an arm by measuring the inclination amount of the robot arm at each teaching position accurately. CONSTITUTION:A light source 8 is installed on the bottom part of the second arm 4 movable parallel to an installing surface 12, the light flux 15a emitted from the light source 8 is reflected to a semitransparent plate 10 provided on top of the second arm 4 by a reflection plate 11 on the installing surface 12, and a light spot is formed on the semitransparent plate 10. Then, the slipping amount of the light spot is measured by using a camera means 7 and a camera image position operation means installed on top of the second arm 4, and the falling amount of the arm is calculated by using a falling amount calculating means. Consequently, a sensor for measuring the inclination amount exclusively is not necessary to provide, and a minute inclination amount can be measured accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the amount of sagging due to the weight of an arm which causes an error in a robot position command.

[0002]

2. Description of the Related Art Conventionally, a position data input method by teaching has been used as a position command method for an industrial robot.
On the other hand, in recent years, there has been an increasing demand for a method of operating a robot using position data created offline or position data obtained via an image processing device. However, in general, for industrial robots, the positioning reproducibility of the robot itself is satisfactory, but the relative positioning accuracy between the robot and the external environment remains a problem.

As a reference example of the prior art, Japanese Patent Application Laid-Open No. 62-1
No. 57790 is cited. FIG. 6 is a structural model diagram of an articulated robot, and FIG. 7 is a flowchart showing how to provide an error correction value relating to the arm deflection amount with respect to teach data at an arbitrary position.

As shown in FIG. 6, the articulated robot has a base 18, a swivel base 19 rotatably connected via a swivel joint 20, and a swivel base 19 via a first rotary joint 22. And a second arm 23 connected to the first arm 21 via a second rotary joint 24. The tip of the second arm 23 handles a work to handle the work. It is designed to

According to the flow chart shown in FIG. 7, a correction value for the amount of displacement of the handling position due to arm deflection is obtained. In the arm of the robot in the model shown in FIG. 6, the insufficient rigidity of each joint of the swivel joint 20, the first rotary joint 22, and the second rotary joint 24 is the main cause of the deviation of the handling position due to arm deflection. Occurs. In the case of the robot model shown in FIG. 6, even if the teach data on the mesh shown by the solid line in FIG. 6 is created offline, when the robot is actually operated, the points shown by the dotted line in FIG. The robot works. Therefore, the spring constant of each joint is measured in advance, and the amount of deviation due to arm deflection generated at each teaching point is calculated from this spring constant, arm weight, and handling weight to create a correction value table.

Next, a correction value corresponding to each teach data input by MDI (manual data input) is taken out from the correction value table, and a correction calculation is performed based on the correction value and the teach data to calculate the correction data. By operating the robot controller based on this correction data, the tip of the robot is moved to a predetermined teach point.

[0007]

However, since the cause of arm deflection is not only the spring constant of each joint, the above-described method of calculating the amount of deviation due to arm deflection based on the spring constant of each joint is accurate. It is not enough to calculate the amount of arm deflection. Further, in the above-described method, simulation data cannot be created unless accurate data such as arm weight and arm rigidity is known.

In order to solve these problems, an object of the present invention is to provide an apparatus for measuring the arm deflection amount at each teaching point, which is caused by various error factors, with high accuracy and in a simple manner.

[0009]

In order to solve the above problems, according to the present invention, in a multi-joint robot having a tip arm that can move in parallel with respect to a reference plane, a light source attached at the base of the tip arm is used as a reference plane. The light flux emitted in the direction is reflected by the reflector installed on the reference surface toward the semi-transparent plate attached to the tip of the robot arm, and the camera means installed on the top of the semi-transparent plate and the light spot reflected on the semi-transparent plate are reflected. The position of the light spot projected on the semi-transparent plate installed in the field of view of the camera is calculated with the camera image position calculation means capable of measuring the position, and the height change measuring unit is used to measure the position of the tip arm with respect to the reference plane. The amount of change in height is measured, and the amount of change in height of the tip arm with respect to the reference plane is measured from the position of the light spot and the amount of change in height of the tip arm using the amount of deviation calculation means.

[0010]

When the amount of arm deflection changes at each teaching point, the position of the center of gravity of the light spot visible on the semitransparent plate moves with respect to the camera position. It is measured by the position calculation means. On the other hand, the height change amount due to the arm deflection is measured using an arm height change amount measuring unit. Then, the relative arm tilt angle and tilt direction with respect to the robot origin position, which occurs when the robot arm is moved from the robot origin position to each teaching point, are measured as the positional deviation amount and the arm height change amount. Can be derived from.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an external view of an arm deflection measuring device of an articulated robot of the present invention. The base 30 is installed on the mounting surface 12 that serves as a reference surface when the robot is mounted, and the first arm 2 that can swivel in the horizontal direction around the first swivel shaft 3 is provided on the base 30. The first arm 2 is provided with the second arm 4 which can be swiveled in the horizontal plane centering on the second swivel shaft 5 located at the tip, and the tip of the second arm 4 can be vertically moved and swivel in the horizontal plane. An embodiment will be described by taking a horizontal articulated robot having At the tip of the second arm 4 of this robot, camera means 7 for capturing images in a direction facing the mounting surface 12, and between the camera means 7 and the mounting surface 12 and in parallel with the mounting surface 12, the semitransparent plate 1 is provided.
0 and are attached. The robot controller 1 includes a robot motion control means, a camera image position calculation means, and a deflection amount calculation means. A precision surface plate having a very high degree of flatness is used for the mounting surface 12, and a flat reflecting plate 11 that can move upward relative to the mounting surface is installed on the mounting surface. Further, the light source 8 capable of irradiating the light flux 15 a at a certain angle with respect to the reflecting plate 11 on the mounting surface 12 is mounted at the base position of the second arm 4. The light beam 15 a emitted from the light source 8 is reflected by the reflection plate 11 on the mounting surface 12 to form a light spot on the semitransparent plate 10 at the tip of the second arm 4. On the other hand, a jig 17 for measuring a height change generated between the second arm 4 and the reflection plate 11.
And a displacement sensor 14 are attached to the tool shaft 6 of the robot.

In the apparatus configuration shown in FIG. 1, the semitransparent plate 10 and the light source 8 have the same height with respect to the mounting surface 12, and the height L ₀ is a known dimension in advance (see FIG. 2). Further, the direction of the light beam 15a emitted from the light source 8 in the horizontal plane direction is made to coincide with the direction of the tip of the second arm 4. here,
The amount of bending of the arm between the light source mounting position of the second arm 4 and the semitransparent plate mounting position is very small. The camera image position calculation means is calibrated so that the camera image position in the XY directions can be measured with the arm front-rear direction of the second arm 4 as the Y direction and the arm left-right direction perpendicular to the second arm 4 as the X direction. As shown in FIGS. 3 and 4, under the above-described conditions, the camera means 7 and the camera image position calculation means perform the following operations on the light spot 9a projected on the semitransparent plate 10 at the origin positions of the first and second arms. The second arm 4 of the light spot 9c reflected on the semi-transparent plate 10 caused when the arm is moved.
Measure the distance in the front-back direction and the distance in the left-right direction. Further, by measuring the amount of change in height generated between the reflector 11 and the second arm 4, the amount of change in the deflection angle θ _{y of} the second arm 4 in the front-rear direction and the amount of change in the deflection angle θ in the left-right direction are measured. It is possible to calculate _x and.

FIG. 2 is a diagram showing the first stage of the arm deflection measurement. In order to obtain the amount of change in the arm deflection angle of the second arm 4 in the front-rear direction, first, the second arm 4 to the reflection plate 11 of the light beam 15a emitted from the light source 8 at the arm origin position.
The incident angle α with respect to the front-back direction is determined. First reflector 1
The light spot 9 reflected on the semi-transparent plate 10 by reflecting the luminous flux irradiated on
The position y ₁ of the second arm 4 in the front-back direction is measured, and then the light spot of the light beam 15b, which is the reflected light of the light beam applied to the reflection plate 11 and the reflection plate 13 having a different height, is reflected on the semitransparent plate 10. The position y ₂ of the second arm 4 of 9b in the front-rear direction is measured. When the height of the reflection plate 11 with respect to the mounting surface 12 is L ₁ and the height of the reflection plate 13 with respect to the mounting surface 12 is L ₂ , the incident angle α can be obtained from Equation 1.

[0014]

[Equation 1]

When the first and second arms are at the origin position, when the reflection plate 11 is used, the position y ₁ of the light spot 9a reflected on the semitransparent plate 10 in the front-rear direction of the second arm 4 and the left-right direction. The position x ₁ is measured by the camera means 7 and the camera image position calculation means. Further, the tool shaft 6 is positioned so that the displacement sensor 14 attached to the tool shaft 6 has a measurable height with respect to the reflection plate 11. Then, the displacement sensor controller 16 measures the distance h ₁ between the displacement sensor 14 and the mounting surface 12.

Next, the first and second arms are moved to arbitrary positions and the light beam 15c emitted from the light source 8 (see FIG. 3).
The reflector 11 is moved to a position where the reflection can be performed. Then, at this arbitrary arm position, the position y _{3 in} the front-rear direction and the position x _{3 in the} left-right direction of the second arm 4 of the light spot 9c reflected on the semi-transparent plate 10.
And are measured by the camera means 7 and the camera image position calculation means as in the case of the arm origin position. Further, the robot tool shaft 6 is positioned at the same height as in the case of the arm origin position, and the displacement sensor controller 16 causes the displacement sensor 14 to move.
・ Measure the distance h ₃ between the mounting surfaces 12.

FIG. 3 is a model diagram for obtaining the arm deflection angle of the second arm 4 in the front-rear direction when the arm is moved with respect to the arm origin position. The amount of change in the sagging angle of the second arm 4 is small, and therefore the amount of change in the angle of the semi-transparent plate 10 with respect to the mounting surface 12 is also small. Therefore, the semi-transparent plate 10 remains on the mounting surface 12 even when the arm is moved. It can be assumed that they are parallel to each other. Therefore, as shown in FIG. 3, the states of the light flux 15a and the light flux 15c are modeled by an isosceles triangle having a solid line as a hypotenuse and an isosceles triangle having a dotted line as a hypotenuse. Here, d _y is the measured value y in the front-back direction of the second arm 4.
₃ is the difference between the measured value y ₁ and h ₀ is the displacement sensor 14.
This is the difference between the measured distance h ₃ between the reflectors 11 and the measured value h ₁ . That is, it is the amount of change in the base and height of the two isosceles triangles shown in FIG. The d _y generated by the change in the amount of deflection of the second arm 4 in the front-rear direction is the amount of change in the deflection angle θ _{y in} the front-rear direction of the second arm 4 and the reflection of the second arm 4 caused by the deflection of the first and second arms as a whole. The height change amount h ₀ with respect to the plate 11 is a factor. Therefore, the second
The amount of change in the deflection angle θ _y of the arm 4 in the front-rear direction is calculated in consideration of the amount of change in height h ₀ of the second arm 4 with respect to the reflector 11.
It is calculated by Equation 2.

[0018]

[Equation 2]

Next, referring to FIG. 4, the second arm 4
A procedure for obtaining the arm deflection angle variation amount θ _x with respect to the left-right direction will be described. As described above, the direction of the light beam 15a that generates the light spot 9a in the horizontal direction is made to coincide with the direction of the tip of the second arm 4, and in the Y direction in the coordinate system of the camera image position calculation means shown in FIG. is there. The lateral movement amount d _x of the second arm 4 of the light spot 9c with respect to the light spot 9a is equal to the second
The amount of change in the tilt angle of the arm 4 in the left-right direction θ _x is a factor. Since the angle of the light beam 15a with respect to the front-rear direction of the second arm 4 is vertical, and the amount of change in the deflection angle θ _{x of} the second arm 4 in the left-right direction is also small, the second value with respect to the measured value d _x
The influence of the height change amount h ₀ of the arm can be ignored. Therefore,
The amount of change θ _{x in} the lateral deflection angle of the second arm 4 is obtained by Equation 3.

[0020]

[Equation 3]

By using the amount of change in the longitudinal deflection angle θ _{y of} the second arm 4 and the amount of the variation in the lateral deflection angle θ _x , the two planes intersecting each other with a certain inclination are shown in FIG. In addition, the amount of change in the deflection angle θ _xy of the second arm 4 with respect to the reflection plate 11 can be obtained by Equation 4.

[0022]

[Equation 4]

Further, the direction β of the camber angle change amount θ _xy with respect to the X-coordinate direction of the camera image position calculation means can be obtained by the equation 5.

[0024]

[Equation 5]

The above calculation of the angle of incidence alpha, the calculation of the variation theta _y in the longitudinal direction of the tilt angle of the second arm, the calculation of the variation theta _x in the lateral direction of the tilt angle of the second arm, fallen in the second arm The calculation of the angle change amount θ _{xy and} the calculation of the direction β of the deflection angle change amount θ _xy with respect to the X coordinate direction are performed using known data (L ₀ , L ₁ ,
L ₂ ) and the data (y ₁ , y ₂ , y ₃ , x measured by the camera image position calculation means and the displacement sensor controller)
_{Based on 1} , x ₃ , h ₁ , h ₃ ), it is calculated by the deflection amount calculating means built in the robot controller according to the procedure described above.

As described above, in the case of the horizontal articulated robot, since the deflection angle data of the robot tool axis 6 depends on the deflection angle data of the second arm 4, it is possible to calculate the deflection angle data of the second arm 4. The deflection angle data of the tool shaft 6 can be obtained. Further, by reading the current coordinates (joint angle) of the robot at the measurement point of each deflection angle data with the robot controller 1, it is possible to create an arm deflection amount database in the robot movable range.

In this embodiment, the second horizontal articulated robot
The measurement was performed by taking the amount of change in the arm deflection angle as an example, but the same measurement can be performed in a multi-joint robot having a mechanism capable of controlling the angle of the tip arm with respect to the mounting surface at any position where the arm can move. Further, in the present embodiment, the mounting surface as the reference surface is a horizontal surface, but the reference surface may be a vertical surface or a surface having an arbitrary inclination.

[0028]

The robot arm deflection amount measuring device according to the present invention adopts a method of reflecting the light beam emitted from the arm side through the reference surface, so that the distance between the arm and the reference surface can be relatively large. Therefore, it is possible to accurately measure a minute amount of change in sagging. Further, by using the camera means and the camera image position calculation means attached to the robot, it is not necessary to use dedicated sensors for measuring the amount of sagging.

[Brief description of drawings]

FIG. 1 is an external view of an arm deflection measuring device of an articulated robot according to an embodiment of the present invention.

FIG. 2 is a diagram showing a first stage of arm deflection measurement of an articulated robot according to an embodiment of the present invention.

FIG. 3 is a model diagram for calculating a longitudinal deflection angle of a second arm 4 according to an embodiment of the present invention.

FIG. 4 is a diagram showing a movement amount of a light spot on a semitransparent plate according to an embodiment of the present invention.

FIG. 5 is a model diagram for calculating the amount of sagging of the second arm 4 with respect to the mounting surface according to the embodiment of the present invention.

FIG. 6 is a structural model diagram of a conventional articulated robot.

FIG. 7 is a flowchart illustrating a conventional method for obtaining an arm deflection amount correction value.

[Explanation of reference symbols] 1 robot controller 2 first arm 4 second arm 7 camera means 8 light source 10 semi-transparent plate 11 reflecting plate 12 mounting surface

Claims (1)

[Claims] 1. A multi-joint robot having a tip arm that can move in parallel to a reference plane, a light source attached to the base of the tip arm, a reflector installed on the reference plane, and a half attached to the tip of the arm. Using a transparent plate, the luminous flux emitted from the light source is reflected by a reflection plate to image the light spot on the semitransparent plate, and the position of the light point projected on the semitransparent plate and the camera means mounted on the semitransparent plate can be measured. The camera image position calculation means calculates the position of the light spot on the semi-transparent plate installed in the camera view direction, and the height change amount measurement unit is used to calculate the height change amount of the tip arm with respect to the reference plane. The arm deflection of the multi-joint robot characterized by measuring the deflection amount with respect to the reference plane of the tip arm from the calculated position of the light spot and the measured change amount of the arm height by using the deflection amount calculation means. amount measuring device.