JP2000039911A - Robot controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a robot controller which can check whether or not interference is caused without extremely limiting the strict positioning movable area of a work. SOLUTION: A robot hand part 3 is modeled with spheres having their centers at tip points A, B, and C and beams connecting the centers of the spheres, the movable area of the robot hand part 3 is set according to the shape of a box 5, and in the said movable areas, the movable areas of respective axes are further limited according to the positions and attitudes of the spheres and the beams.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot control device for preventing interference between a robot and a box when picking an object in a box, for example.

[0002]

2. Description of the Related Art For example, in a teaching playback type robot that operates as taught, if there is no interference with surroundings during teaching, work can be performed without any problem. There is no problem if there is no interference. This is the same when performing a picking operation, for example. However, since the target work is positioned and picked, there is little problem with interference.

[0003]

However, even with this picking operation, there is a problem that the work positioning operation is troublesome and the configuration of the positioning system becomes complicated. Also, as another measure, the position and orientation of the work are detected by image processing without strictly positioning the work, and the robot may perform picking work based on the result, but this image processing prevents interference. Therefore, the movable area was extremely limited.

The present invention has been made in view of the above-described problems, and has as its object to provide a robot control device that determines a movable region so as not to limit the movable region extremely even if image processing is performed without strictly positioning the work. Aim.

[0005]

The present invention that achieves the above object has the following matters specifying the invention. According to a first aspect of the present invention, in a robot control device for preventing interference between a robot and an object, a robot hand portion is modeled by a sphere and a beam connecting the centers of the sphere, and the robot hand portion is movable. The region is set based on the shape of the object, and the movable region of each axis is further limited from the position and orientation of the sphere and the beam within the movable region.

According to a second aspect, in the first aspect, an intersection between the beam and a boundary of the shape of the object is determined to further limit the movable area.

According to a third aspect of the present invention, in the first or second aspect, the movable region is further limited in consideration of the thickness and inclination of the beam.

According to a fourth aspect of the present invention, in the above-described first, second, or third aspect, the movable area is checked on a path during a robot operation.

A fifth invention is based on the fourth invention, wherein:
Before reaching the interference area during the movement of the movable area, the vehicle is driven at a limited speed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, an example of an embodiment of the present invention will be described with reference to FIGS. FIG.
(A) is a schematic diagram of an example of the entire robot, and (b) shows a wrist portion and a robot hand portion at the tip. In FIG. 1, the robot arm 1 has a robot hand portion 3 having a picking gripper 2 at the tip thereof.
Based on FIG. 1, a model is created in which the wrist part 4 and the hand part 3 are simulated by beams, and spheres are arranged so that end points (apex parts) and members can be included or approximated.

That is, as shown in FIG. 2, a sphere is set about the rotation axis of the wrist 4 around the end point C, and then a sphere is set about the end point (not the rotation axis but the vertex) B of the hand section 3. Further, a sphere is set with the center of the grip portion of the hand portion 3 as the end point A, and these axes C, B, and A are connected to form a beam. In this case, TCP is an abbreviation of Tool Center Point, and indicates the tip of the hand.

The setting of the sphere and the beam is performed in consideration of the presence or absence of interference with the object, the end points are set at the axes, angles and vertices of the joints, and the radius of the sphere is set to the radius of the rotation axis, the member Is set as the radius of the sphere containing. The robot can be modeled by the setting of the sphere and the beam, and the processing can be performed with a relatively small amount of calculation based on the presence or absence of interference.

On the other hand, for example, when picking a workpiece,
Specify the target of interference. For example, the box 5 shown in FIG.
And a coordinate system (referred to as a work frame) is set in accordance with the box 5. Next, a movable area is set according to the shape of the box 5. In a rectangular coordinate system as shown in FIG.
The movable area inside the box and above the box as shown in FIG. Inside the box 0 ≦ x ≦ x _max 0 ≦ y ≦ y _max 0 ≦ z (1) Upper part of the box x <0, x _max <xy <0, y _max <yz _max <z ... (2)

The coordinates inside and above the box are shown in FIGS.
In the example, it is related to the work frame.
Based on the position and posture of the TCP end of the hand on the robot side
It is necessary to perform necessary coordinate transformation. For example, the coordinate system
As the coordinate system based on the robot and the workpiece
Coordinate system or image processing device for image processing
There is a coordinate system that has a different coordinate system.
It is important. In this example, the position / posture of the hand tip TCP
Is given, the work flow at each of the points A, B, and C in FIG.
Position and orientation on the game. Work frame
Position and posture of the hand tip TCP^WT_PWhen
If given^PT _TFrom TCP to tool frame
Matrix,^TT_A,^TT_B,^TT_CThe tool
When the positions and postures of points A, B, and C in the
Points A, B, and C in the frame are as follows.^W T_A=^WT_P・^PT_T・^TT_A ^W T_B=^WT_P・^PT_T・^TT_B ^W T_C=^WT_P・^PT_T・^TT_C … (3)

The points A, B, and C obtained in this manner exist inside the box and above the box. This condition is obtained by taking into account the sphere radii r _A , r _B , and r _C.
(2) becomes the following equation. <About the point A> (movable area of the _{box) r A ≦ x ≦ x max} -r A r A ≦ y ≦ y max -r A r A ≦ z Also, (the movable region of Hakogai) x <-r _{A , x max + r A <x} y <-r A, y max + r A <y z max + r a ≦ z

[0016] <Regarding point _{B> r B ≦ x ≦ x} max -r B r B ≦ y ≦ y max -r B r B ≦ z ( movable area of the box) also (movable area of Hakogai) x < −r _B , x _max + r _B <xy <−r _B , y _max + r _B <yz _max + r _B ≦ z

<Regarding Point C> (Movable area inside box) r _C ≤ x ≤ x _max- r _C r _C ≤ y ≤ y _max- r _C r _C ≤ z Also, (movable area outside box) x < −r _C , x _max + r _C <xy <−r _C , y _max + r _C <yz _max + r _B ≦ z

As described above, if the end points A, B, and C are within the ranges of x, y, and z satisfying the above conditions, no interference occurs. That is, the positions of the points A, B, and C are obtained, and it is determined whether or not the positions are within the movable region.

In the above description, the procedure for determining whether or not the points A, B, and _C taking into account the radii r _A , r _B , and r _C are within the movable range has been described. Can be As shown in FIG. 5, when the intersection between the beam connecting the points A and B and the plane including the side wall of the box 5 is equal to or smaller than z _max, interference occurs, and the beam connecting the points C and B is also illustrated. Interference occurs as shown in FIG. Therefore, it is necessary to determine the interference between these beams and the side wall surface of the box 5.

Further, in the modeled beams shown in FIGS. 2, 5, and 6, the thickness is not considered. Therefore, interference may actually occur in the modeled beam. Therefore, the beam is modeled by a cylinder, and the thickness of the beam is considered. That is, when the radius of the cylinder is r, in the beam interference check shown in FIGS. 5 and 6 described above, the intersection with the beam satisfies the condition of z _max + r <z to prevent interference.

Further, as shown in FIG. 7, even when the intersection of the beam and the plane including the side wall of the box 5 satisfies the condition of the above expression z _max + r <z, the beam is positioned at an angle to the box 5. Sometimes interference can occur. Therefore, the beam and the box 5
The length l shown in FIG. 7 is obtained by obtaining the angle θ at which the plane intersecting the plane including the side wall. That is, as shown in FIG. 7, the limit at which the beam and the box 5 interfere with each other is that when the angle θ is determined, l = r / cos θ is determined, and this l is z _max + (r / cos).
sθ) <z.

In the above description, the interference is determined in consideration of the points A, B, and C, the beams connecting them, the thickness of the beam, and the inclination of the beam. A check is made to see if there is any interference with the target point before the start. However, even if the target point is within the operable range, interference may occur on the path to the target point. Therefore, if the above-described check is performed in real time on the route, interference can be reliably prevented.

In the case where interference occurs on the above-mentioned route, that is, while moving, in order to minimize damage to the equipment, an area sensor or a touch sensor is provided to monitor the interference between the robot and the box. If interference occurs, the robot may be stopped immediately. However, in order to further improve the security, the operation speed is limited by using the minimum value of the distance to the interference area at each check point in real time. That is, when the distance to the boundary of the movable area (the distance to the interference area) is obtained at points A, B, and C as shown in FIG. 8, in the case of point A, x _A −
r _A , when (x _max −r _A ) −x _A is not zero at the other wall, y _A −r _A at one wall along the y axis, and (y _max) at the other wall. When −r _A ) −y _A is not zero, or when z _A −r _A is not zero along the z-axis, no interference occurs and the distance to the interference area can be obtained.

Further, as shown in FIG. 9, when the distance of the beam to the boundary of the movable area is obtained, the beam coordinate value is larger than z _max (z−z _max ), and the beam coordinate value is larger considering r. _{(z- (z max + r)} ), when in consideration of r and the slope is large beam coordinate values (z- (z _max +
r / cos θ)), the distance to the interference area can be obtained without causing interference.

On the other hand, the deceleration start distance l _d is set, and the distance l to the interference area determined as described above is the deceleration start distance l _d.
If it is larger, the operation is performed without limiting the speed. If it is smaller than l _d , the speed is limited by, for example, the following formula. When the specified speed v _P minimum speed v _min operating speed and v,
v = (l / l _d ) v _P , and when v is v <v _min , v =
Let v _min . As a result, it is possible to minimize the damage to the device due to the interference.

[0026]

As described above, according to the present invention, in a robot control apparatus for preventing interference between a robot and an object, a robot hand portion is provided with a sphere centered on an end point and a center of the sphere. Modeling with the connected beam, and setting the movable area of the robot hand part from the shape of the object, further move the movable area of each axis within the movable area from the position and orientation of the sphere and beam. Because of the limitation, the presence or absence of interference can be checked in advance, so that there is no damage to the equipment and the presence or absence of interference can be checked with a simple model, so strict positioning of the work and extreme restrictions on the movable area Disappears.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a robot.

FIG. 2 is a modeled explanatory diagram.

FIG. 3 is an explanatory view of a box.

FIG. 4 is an explanatory diagram of a movable region.

FIG. 5 is a beam interference state diagram.

FIG. 6 is a beam interference state diagram.

FIG. 7 is an explanatory diagram of arm interference.

FIG. 8 is an explanatory diagram up to an interference region.

FIG. 9 is an explanatory diagram up to a beam interference region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Robot arm 2 Grasping part 3 Robot hand part 4 Wrist part 5 Box A, B, C Endpoint

Claims (5)

[Claims] A robot controller for preventing interference between a robot and an object, wherein a robot hand is modeled by a sphere and a beam connecting the centers of the sphere, and a movable area of the robot hand is provided. Is set from the shape of the object, and the movable region of each axis is further limited from the position and orientation of the sphere and the beam within the movable region, wherein the movable region of each axis is further limited. 2. The robot controller according to claim 1, wherein an intersection of the beam and a boundary of the shape of the object is determined to further limit a movable area. 3. The robot control device according to claim 1, wherein the movable region is further limited in consideration of the thickness and inclination of the beam. 4. The robot control device according to claim 1, wherein the movable area is checked on a path during the robot operation. 5. The robot control device according to claim 4, wherein the robot is operated at a limited speed before reaching the interference region during the movement of the movable region.