Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
1997-12-12
2001-02-06
Grant, William (Department: 2786)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S063000, C700S178000, C318S568180
Reexamination Certificate
active
06185480
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an interference preventing method for industrial robots and handling robots used for the same, and more particularly, a method which can return a robot which is made to stop its operation by the occurrence of a trouble to a predetermined position and prevents the interference of the robot with an object disposed around the robot during a handling operation in which works which are stacked on a work stack base is gripped one by one and works are fed to a working machine such as a press or a press brake or a packaging machine such as a binder one by one and are stacked on a stack base one by one, and a robot used for the method.
BACKGROUND OF THE INVENTION
Conventionally, as shown in
FIG. 7
, this type of robot is disposed in front of a working machine
50
such a press brake. The robot is constructed such that a first arm
53
which is rotatable on a horizontal axis (a first axis J
1
) is radially connected to an upper portion of a support strut
51
mounted on a floor by means of a first rotated joint
52
. A second arm
55
which is rotatable on a horizontal axis (a second axis J
2
) is radially connected to a distal end of the first arm
53
by means of a second rotated joint
54
. A third arm
57
which is rotatable on a horizontal axis (a third axis J
3
) is connected to a distal end of the second arm
55
in a coaxial direction by means of a third rotated joint
56
. A hand
59
which is rotatable on a horizontal axis (a fourth axis J
4
) is connected to a distal end of the third arm
55
by means of a fourth rotated joint
58
. These rotated joints are respectively provided with servo motors M
1
,M
2
,M
3
,M
4
and position detecting means such as encoders for detecting the rotating positions of these rotated joints. By constantly detecting the position of the hand
59
with the position detecting means, the rotating angles of these rotated joints are controlled such that the hand
59
traces a plurality of points which are preliminarily taught and stored in memory. The coordinates of the position of the center of the hand
59
is Cartesian coordinates made of an X coordinate (a direction of arrow X) which is a traverse distance of the hand
59
when the hand
59
is moved in parallel in a horizontal direction by a combination of the rotations of the first to third rotated joints and a Y coordinate (a direction of Y) which is a traverse distance of the hand
59
when the hand
59
is parallelly moved in a vertical direction by a combination of the rotations of the first to third rotated joints. The posture of the hand
59
is controlled by two polar coordinates made of an A coordinate which is a rotating angle of the hand
59
around the fourth axis J
4
and a B coordinate which is a rotating angle of the hand
59
around the third axis J
3
. The origin of the coordinates of four axes is arbitrary and a basic posture of the robot may be predetermined as such an origin. The hand
59
is provided with a gripping element such as a vacuum cup
60
. The servo motors M
1
to M
4
are controlled by a microcomputer installed in a control panel
61
.
With such a robot
62
, a series of operations which comprise descending the hand
59
to suck and pick up a work which is not yet subjected any working from a work supply base
63
, advancing and inserting one edge of the work into the working machine
50
to bend the work, retracting the work from the working machine
50
to a predetermined position where the hand is rotated about a horizontal axis, subjecting the other edge of the work to the working of the working machine
50
, and stacking the work on a product stacking base
64
after working on the work is completed, and returning the hand
59
to the work supply base
63
to pick up a next work which is not yet subjected to any working, are carried out as a cycle and these cyclic operations are repeated. It must be noted, however, that the lifting amount of the hand is changed corresponding to the height of works remaining on the work supply base
63
as well as on the product stacking base
64
.
To carry out the above-mentioned repetitious operations in a most efficient manner, the robot
62
is preliminarily taught so as to execute operations on the above-mentioned four axes in an overlapping manner or simultaneously. Since the robot
62
carries out the operations in accordance with sequences and timings which are preliminarily taught, no trouble occurs so long as the operations are carried out in a normal routine. However, when a trouble such as dropping of the work in the midst of the routine work occurs and the operation of the robot is stopped accordingly, the robot
62
is returned to a fixed position where the position of the work can be determined, e.g. a position on the work supply base or a position on the mold of the working machine and the work is gripped again. Then, the work is returned to a position where the robot is stopped while being gripped by the robot and the robot is operated again in accordance with a program of the original routine. Conventionally, in such a case, a next target position to which the hand is to be moved is taught and the hand is moved to the target position with an automatic manipulation or the hand is moved to the target position with a manual manipulation such that the hand is moved little by little by manually operating the axes one after another.
To move the hand to the taught target position with the automatic manipulation, however, the operations on the four axes are carried out simultaneously without any sequence, the work or the hand may heavily comes into contact with objects located around the robot and accordingly the hand may be broken or ruptured. On the other hand, the manual manipulation which is carried out by operating the axes one after another at a low speed takes a considerable operating time thus lowering an operating efficiency.
Accordingly, it is an object of the present invention to provide an interference preventing method which can enhance the efficiency in an operation to return the robot to the normal operation after the occurrence of a trouble and the robot which can carry out the method.
DISCLOSURE OF INVENTION
The interference preventing method for industrial robots according to the present invention is characterized in that, an operation to automatically move a hand of a robot toward a taught target position, comprises a step of reading the present position of the hand, a step of computing the difference between the taught target position and the present position of the hand, a step of judging whether this difference is within a predetermined range or not, a step of setting the moving speed of the hand to a predetermined normal speed when the difference is within the predetermined range, a step of setting the moving speed of the hand to a predetermined low speed when the difference is out of the predetermined range, and a step of moving the hand automatically to the target position at the set speed. The above-mentioned ‘predetermined range’ is determined in view of the kind of operation, the size of the work or the size and shape of an object disposed around the robot. The above-mentioned ‘movement of the hand’ includes a revolution of the hand around a horizontal axis or a vertical axis in addition to the traverse of the central point of the hand in a space. In this case, the central point of the hand does not move and the hand is only angularly shifted.
According to the method of the present invention, present positions are determined by a plurality of coordinates and the difference between the taught target position and at least coordinates on one axis is computed and the judgement is made based on the difference. Alternatively, it may be possible to set the moving speed of the hand to a low speed when at least one of the coordinates is out of the predetermined range.
The handling robot according to the present invention is a type of a robot which repeats an operation to pick up a work from a predetermined position and transfer the work to another p
Nakajima Atsushi
Shiomichi Yukimasa
Takahashi Toshiyuki
Browdy and Neimark
Garland Steven R.
Grant William
Toyo Kohan Co., Ltd
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