JPH0553592B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an arm control method for an industrial robot in which two arms can cross each other.

Conventional technology and its disadvantages Many manipulator-type industrial robots are currently being proposed for various handling purposes such as welding, painting, and logistics, but considering the appearance of the robot, most of them have one arm. That is, it is a single arm type, and there are not many industrial robots that have two arms.
An example of a robot having two arms is a two-arm rotating robot that is incorporated into a crank press line, as shown in FIG. It is configured in an open state with a phase angle and is arranged so as to horizontally rotate at an angle of 90° about a rotation axis 14 common to the two arms. and
By sequentially arranging the workpiece pedestal 16, the first crank press 18 and the second crank press 20 at a phase angle of 90 degrees, and intermittently rotating the two arms 10 and 12 back and forth by 90 degrees, The arm 10 loads the work on the work pedestal 16 onto the first crank press 18, and the arm 12 loads the work on the first crank press 18 onto the second crank press 20.
Work will be carried out to load the data. but,
In this type of robot, the individual arms have no degrees of freedom relative to each other, so tasks by each arm are always performed simultaneously, so that, for example, while one arm is performing a particular task, the other It was not possible for the arm to move into a preparatory action for the work in question.

There is also an assembly robot, generally called a double-hand type, in which multiple independent manipulators are placed on a common base and each arm is controlled independently; However, there are disadvantages such as an increase in installation space, an increase in manufacturing cost, and a complicated control system.

Furthermore, an industrial robot equipped with two arms and configured to be able to impart independent motion to these arms is disclosed, for example, in Japanese Patent Laid-Open No. 15254/1983. However, in order to cover a wide range of work, the rotation angle of the two arms was set large,
If both arms are configured to cross each other, there is a risk that the workpieces held by the arms will collide and interfere with each other when the arms cross each other.

Purpose of the Invention The present invention was devised in view of the drawbacks inherent in the aforementioned two-arm industrial robot, and the two arms intersect with each other to perform various tasks. A means for solving the problem is to provide an arm control method that prevents the workpieces held on each arm from colliding and interfering with each other. In order to suitably achieve this, the present invention includes disposing a first arm and a second arm on an upright support in a vertical relationship so that they can each independently freely rotate and move forward and backward in a straight line. In an industrial robot configured such that a first arm and a second arm can intersect with each other, the first arm and the second arm respectively hold a workpiece at a workpiece take-out position and transfer it to a workpiece discharge position, and an empty When each arm is operated to return the workpiece from the workpiece release position to the workpiece takeout position, the first arm and the second arm must be operated so that the arms move from one position to the other. The origin to be passed is given at different coordinate positions in the radial direction from the rotation center of both arms, and when each arm goes from the one position to the other position, after passing the unique origin given to each arm. , the movement of the first arm and the second arm is controlled so that they move to the other position and intersect in a vertical relationship in the region where they move from the one position to the other position.

Embodiments Next, a method for controlling a robot arm according to the present invention will be described in detail below using preferred embodiments with reference to the accompanying drawings. FIG. 2 is a side view of a robot that can suitably carry out the method according to the present invention, and FIG. 3 is a perspective view of the robot shown in FIG. 2 installed on a transportation line for physical distribution. The illustrated industrial robot has a plurality of arms arranged at a predetermined height difference on a support such as an upright column, and each of these arms is configured to be capable of horizontal rotation and horizontal expansion/contraction. .

In the drawings, reference numeral 22 indicates a support that forms the base of the robot body, and in this embodiment, this support 22 is a cylindrical upright column attached to a fixed base 24. Depending on the environment, it may be an upright wall or a gate-shaped pedestal. The support body 22 has two sleeves 26, 2 with a predetermined height difference in vertical relationship.
8 are arranged, and a bracket 3 is attached to shoulders 30, 32 provided correspondingly to these sleeves 26, 28.
3 and 35 are pivotably supported. Then, the brackets 33, 35 are moved by DC servo motors 34, 36 disposed on the shoulders 30, 32, respectively.
A horizontal turning motion is applied to the shoulders 30 and 32.

Both of the DC servo motors 34 and 36 are of a type that integrally incorporates a tachometer generator and a pulse encoder, and a signal from the tachometer generator is sent to a motor driver provided in the control section, and a signal from the pulse encoder is sent to the motor driver provided in the control section. are respectively fed back to the encoder unit, and
It is configured to digitally servo control the appropriate rotation speed of the DC servo motor. Note that the rotational power from the DC servo motors 34 and 36 is transmitted to the brackets 33 and 35, respectively, via appropriate timing belts and other mechanical elements such as gear trains.
The brackets 33, 35 are connected to an arm 42, which will be described later.
44, the support body 22 is horizontally rotated at a required rotation angle.

In the illustrated embodiment, the shoulder 30 is located vertically above and the shoulder 3 is located vertically below.
Holders 38 and 40 are attached to the brackets 33 and 35, which are horizontally pivotably supported on the holder 2, respectively, and a first arm 42 and a second arm 44 are disposed on these holders 38 and 40, respectively, so as to be able to move forward and backward. . That is, each arm can slide forward and backward in the horizontal direction with respect to the holder, for example via a linear motion bearing (linear way), and the forward and backward movement of these arms is controlled by the holder 38, DC servo motor 46, which is attached to 40, respectively.
Granted by 48. DC servo motor 46,
Like the servo motors 34 and 36, 48 has a built-in tachometer generator and a pulse encoder, and is set to an appropriate rotation speed by a digital servo control command from the control unit.
The forward and backward movement of the is accomplished through the use of a linear movement mechanism such as a ball, screw, or rack and pinion.

A hand portion such as a gripper or a finger is attached to each tip of the first arm 42 and second arm 44 of the industrial robot configured as described above, and in this embodiment, the degree of freedom of this hand portion is further improved. In order to do this, various exercise functions such as rotation of the wrist (wrist) and a function of raising and lowering the hand are additionally provided. That is, wrists 50 and 52 are attached to the tips of the arms 42 and 44, respectively, so as to be able to rotate horizontally, and DC
Servo motors 54 and 56 provide horizontal rotation to each wrist. This rotation may be either a rotation in one direction or a reciprocating rotation at a predetermined central angle. Furthermore, a bending motion and a swinging motion of the wrist may be added.

Furthermore, in the lists 50, 52, pneumatic cylinders 58, 60 are respectively vertically mounted as linear actuators, and these cylinders 58,
At the tips of the piston rods 62 and 64 of 60, vacuum cups 66 and 68 are provided as hand portions, respectively. In this case, the cylinder 58,
The length of the cylinder 60 is set to be shorter than the cylinder 58 because the sleeves 26 and 28 have a height difference, but the corresponding vacuum cups 66 and 68 are The maximum descent limits are designed to be equal.
Moreover, the hand part is not limited to this vacuum cup, and of course various types such as a gripper with claws and fingers with multiple fingers can be used depending on the purpose of use.

In this way, in the industrial robot according to the illustrated example, each arm basically has two degrees of freedom: horizontal rotation and forward/backward movement, and since both arms can independently rotate, they cannot cross each other. It's becoming possible. In addition, in order to have a mutual intersection function,
Both arms are provided with a step above and below so that they do not come into contact or interfere with each other during their operation, and each hand section moves in separate trajectories as will be described later. In addition, in this embodiment, as described above, two degrees of freedom are additionally provided: the movement of the number of revolutions of the wrist and the movement of the hand section up and down.
Although not shown, the sleeves 26 and 28 can be moved up and down relative to the support 22 manually or automatically, and the support 22 itself can be connected to a rotary actuator or the like so as to be rotatable. It is extremely easy to design, which further expands the degrees of freedom and working area.

Effects of the Embodiment Next, the robot arm control method according to the present invention will be explained in relation to a robot that can suitably implement the method. As mentioned earlier, the illustrated example robot has two arms, and these arms are configured to be able to intersect with each other, so that the hand section provided at the end of the arm does not collide with interference during work. Therefore, it is necessary to control the movement trajectory.

There are various control methods to program and teach the movement pattern of this arm.
In this embodiment, the required work is stored in the robot,
A teaching/playback method is preferably used in which the task is repeatedly executed by reading out the order, position, and other information of the task. For example, data input through teaching work is stored in a main memory (CPU) in a microcomputer in a control unit (not shown).
The stored data is processed by a microcomputer and given to the digital servo unit. Digital DC servo control of the DC servo motor is performed by a control unit consisting of a digital servo unit, a motor driver, a DC servo motor, a tacho generator, and a pulse encoder corresponding to each axis.

In this case, by simply teaching two points, the starting point P and the ending point Q, the radius can be calculated from these two points to find the motion locus, and the velocity components of each axis such that the circumferential flux is constant can be found. By providing the control section with a circular interpolation function that imparts circular motion to the arm, the arm of the robot can be smoothly controlled. That is, as shown in FIG. 4, the work 70 is moved from point P, which is the work take-out position, to point Q, which is the work discharge position.
When moving the first arm 42 and the second arm 44 between the points P and Q in order to transfer the first arm 42 and the second arm 44 to a point P and Q, both arms are given their own origin located between the P point and the Q point. do. For example, in 1 of FIG. 4, the first arm 42 is given an origin O ₁ through which the arm 42 always passes, and the second arm 44 is given an origin O ₂ through which the arm 44 always passes. These two origins O ₁ and O ₂ are given at different coordinate positions, and the origin O ₁ of the first arm 42 located above is the origin of the second arm 42 located below.
It is set to be located radially outward from the center of rotation of both arms 42, 44 with respect to the origin _O2 of No. 4.

After setting the origin in this way, if teaching from point P to point Q is performed for each arm, the first arm 42 will move as shown in 2 to 4 in Fig. 4.
performs a movement from point P to point Q via the origin O ₁ specific to the arm. The second arm 44 conversely moves from point Q to point P via the origin _O2 unique to the arm.

In this case, both arms 42 and 44 are P
In the process of turning from point to point Q or from point Q to point P, they are controlled to intersect in a vertical relationship. In this way, when the first arm 42 takes out the workpiece 70 from point P and transfers it to point Q (this is taken as the forward path)
In addition, the second arm 44 simultaneously heads from point Q to point P with no load (this is the return trip), and the loci of movement of both arms have different origins, and each arm Since the arms 42 and 44 are arranged with a required height difference, their trajectories do not intersect with each other, and therefore, the hands of both arms 42 and 44 and the workpiece 70 held thereon do not interfere with each other during their reciprocating movements. There's no way we're going to get along.

Next, an example of the operation when the illustrated industrial robot is incorporated into a distribution line will be described with reference to FIGS. 3 and 5. The distribution line shown in FIG. 3 and FIG.
This is for packing containers (for example, cans of salad oil) in an orderly manner into a presentation box 78 that is positioned and placed on a belt conveyor 76 disposed perpendicular to the conveyance direction of this conveyor 72. As clearly shown in FIG. 3, the belt conveyor 76 includes a conveyor 80 for supplying decorative boxes, an intermediate conveyor 82 for positioning the decorative boxes 78, and a conveyor 82 for carrying out the decorative boxes 78 whose contents have been assembled. It is divided into three blocks with a conveyor 84. The intermediate conveyor 82 is configured to maintain a predetermined distance between the plurality of belt conveyors, and an X-direction positioning stopper 86 protrudes from this distance so as to be movable up and down, and a Y-direction positioning stopper 88 also protrudes in the direction shown. ing. Further, a Y-direction positioning pusher 90 is disposed opposite to the Y-direction positioning stopper 88, and a piston rod 94 of a pneumatic cylinder 92 is connected to this pusher 90 so as to impart forward and backward movement in the horizontal direction. It's summery.

Therefore, the gift box 78 is supplied to the intermediate conveyor 82 by the conveyor 80, and is positioned at a predetermined position on the temporarily stopped intermediate conveyor 82 by the stoppers 86, 88 and the pusher 90. Next, the first arm 42 pivots clockwise under the rotational action of the servo motor 34 and reaches a predetermined position on the belt conveyor 72 (this becomes point P).
After that, the pneumatic cylinder 58 is energized to lower the vacuum cup 66 and hold the makeup can 74 under vacuum. Due to the reverse biasing of the cylinder 58, the vacuum cup 66 holds the makeup can 74 and rises slightly, and continues to move to the first position.
The arm 42 pivots counterclockwise toward the top of the cosmetic case 78 positioned on the intermediate conveyor 82 and stops there. During this counterclockwise turning process, the DC servo motor 46 is driven to appropriately move the first arm 42 forward, so that the tip of the first arm 42 returns to the origin as shown in FIG. Draw an arc passing through O ₁ . Also, the DC servo motor 54 provided in the list 50 rotates,
The wrist 50 is twisted clockwise to control the feeding attitude of the makeup can 74. Next, the cylinder 58 is energized and the vacuum cup 66 is lowered to place the cosmetic can 74 at a predetermined position in the cosmetic case 78, after which the vacuum is released and the cosmetic can 74 is released (this release position is at point Q). ).

On the other hand, the second arm 44 is connected to the first arm 42
Simultaneously with the start of the rotation, the makeup can 74 on the belt conveyor 72 is moved toward the intermediate conveyor 82 while being held under vacuum suction. During this counterclockwise turning process,
The DC servo motor 48 is driven and the second arm 4
The forward movement of step 4 is performed as appropriate, so that the tip of the second arm 44 returns to the origin as shown in FIG.
Draw an arc passing through O ₂ . At this time, the second arm 44 moves from the intermediate conveyor 82 (point Q) to the origin _O1 and then onto the belt conveyor 72 (point P).
It intersects with the first arm 42 which is rotating in a vertical relationship.

Next, the vacuum cup 6 of the second arm 44
The makeup can 74 held at 8 is transferred to the intermediate conveyor 82.
It stops above the upper cosmetic case, and the cosmetic case 74
After releasing it into the cosmetic case 78, the rotation is switched to the clockwise direction. In this case as well, the tip of the second arm 44 draws an arc passing through the origin O ₂ as shown in FIG.
Intersects with the upper and lower relationship. Therefore, even if the first arm 42 and the second arm 44 simultaneously turn in opposite directions and cross each other, the two arms 42 and 44 will not interfere and collide.

Effects of the Invention As explained above, according to the robot arm control method according to the present invention, both arms arranged with a required height difference have different coordinate positions in the radial direction from the rotation center of both arms. Each arm has its own origin, so that the arms always pass through their own origin when moving from one position to the other. In addition, since both arms are controlled to intersect vertically in the process of turning from one position to the other, the hands of both arms and the workpieces held by them do not interfere with each other during their reciprocating movements. Absolutely not.

Moreover, in the present invention, the two arms are independently controlled according to predetermined control commands given to each arm, so while one arm is performing a predetermined task, the other arm starts that task. As a result, the work capacity is doubled and the operating rate is significantly improved. Furthermore, since the two arms can move in the same area, the turning angles of the individual arms can be made the same.
This has many beneficial effects, such as reducing the installation space for the robot and reducing manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing a two-arm rotating robot according to the prior art, FIG. 2 is a side view of a robot in which the method according to the present invention is suitably carried out, and FIG. 3 is shown in FIG. FIG. 4 is a perspective view of the robot installed on a logistics transport line.
FIG. 5 is an explanatory diagram sequentially illustrating the locus of movement when the arms of a book rotate simultaneously, and FIG. 5 is a schematic explanatory diagram showing the state of the locus of movement of two arms in a transportation line for physical distribution. 22... Support body, 42... First arm, 44...
...Second arm, 70...Work, _O1 , _O2 ...Origin, P...Start point, Q...End point.

Claims (1)

[Scope of Claims] 1. A first arm 42 and a second arm 44 are disposed vertically on a support 22 arranged upright so that they can independently rotate freely and move forward and backward in a straight line, In an industrial robot configured such that the first arm 42 and the second arm 44 can intersect with each other, the first arm 42 and the second arm 44 respectively hold the workpiece 70 at the workpiece take-out position P, and the workpiece is removed. When the arms 42 and 44, which have been transferred to the discharge position Q and are now empty, are operated to return from the workpiece discharge position Q to the workpiece take-out position P, each of the first arm 42 and the second arm 44, The arms 42, 44 are in one position P, Q
Origins O ₁ and O ₂ that must be passed while moving from one position to the other position Q and P are given at different coordinate positions in the radial direction from the center of rotation of both arms 42 and 44, and each arm 42 and 44 When moving from the positions P, Q of 1 to the other positions Q, P, the unique origin O ₁ , O ₂ given to each arm 42, 44
After passing through, it moves to the other position Q, P, and from said one position P, Q to the other position Q,
A method for controlling an arm of a robot, comprising controlling the movements of the first arm 42 and the second arm 44 so that they intersect in a vertical relationship in a region in which they move in a direction P.