JP3944580B2 - Robot arm - Google Patents

Description

  The present invention is a robot arm having one end as a base and the other end pivoted on a hand-side joint shaft, and a pantograph type first arm and second arm having a joint between the one end and the other end. It is about.

  When carrying out operations such as transport and assembly by the robot arm, a reaction occurs as the arm moves. Due to this reaction, a large force is applied to the arm base, so that the base structure and the installation part must be strengthened.

  However, if the base structure or installation part of the robot arm is strengthened, its size and weight increase. Also, the reaction caused by the arm generates vibration, which degrades the work accuracy or the vibration propagates to other equipment and has an adverse effect. Therefore, it is necessary to reduce the work efficiency by suppressing the maximum speed of the arm. In some cases.

The reaction caused by the movement of the arm increases as the arm increases in size and speed, and is a serious problem particularly in high-speed operation such as semiconductor bonding work.
JP-A-6-79661

  The present invention has been proposed in view of the above, and provides a robot arm that can eliminate or greatly reduce the reaction caused by the movement of the arm with a simple mechanism, and can improve work accuracy and work efficiency. For the purpose.

In order to achieve the above object, according to a first aspect of the present invention, there is provided a first arm having one end as a base and the other end pivoted on a hand side joint shaft, and having a joint between the one end and the other end. And a pantograph-type robot arm provided with a first arm, a first counterweight projecting in a direction opposite to the first arm with respect to the base, and a second arm with respect to the base A second counterweight projecting in a direction opposite to the first counterweight, and the center of gravity of the first counterweight and the first arm is always present at the base, and the second counterweight The center of gravity position of the entire arm and the second arm is always present at the base .

According to a second aspect of the present invention, in the first aspect of the present invention , the first actuator that rotates the first arm via one end side, and the rotation shaft of the first actuator. A first flywheel that works so as to cancel the reaction moment, a second actuator that rotates the second arm through one end, and a rotation axis of the second actuator And a second flywheel that works to cancel the reaction moment.

According to a third aspect of the present invention, in the second aspect of the present invention , the first flywheel is provided on a rotation shaft of the first actuator via a gear train. Is reversely rotated by a gear train, and the second flywheel is provided on a rotation shaft of the second actuator via a gear train, and is rotated reversely by the gear train. Yes.

Furthermore, in the invention according to claim 4 , the first arm and the second arm having one end as a base and the other end pivotally connected to a hand side joint shaft, each having a joint between the one end and the other end, are provided. In a pantograph type robot arm, a first actuator that rotates the first arm through one end side, and a first actuator that works to cancel the reaction moment with respect to the rotation axis of the first actuator. A first flywheel, a second actuator for rotating the second arm through one end, and a second fly that works to cancel the reaction moment with respect to the rotation axis of the second actuator. And a wheel.

  In the robot arm according to the present invention, the counterweight protrudes from the base in the direction opposite to the arm, so that the force component of the reaction force can be eliminated with a simple mechanism. In addition, since the flywheel that works to cancel the reaction moment with respect to the rotation axis of the actuator that rotates the arm is provided, the moment component of the reaction force can be greatly reduced. In other words, the reaction caused by the movement of the arm can be eliminated or greatly reduced by a simple mechanism, whereby the vibration generated in the base and the installation part can be reduced, and the working accuracy can be improved. Further, high-speed work is possible, and work efficiency can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, a robot arm to which the present invention is applied will be described with reference to FIGS.

  FIG. 1 is an external view of a robot arm to which the present invention is applied, and FIG. 2 is a diagram schematically showing the arm structure. A robot arm 1 to which the present invention is applied has a mechanism combining a horizontal articulated structure and a pantograph type parallel link, and includes a first arm 2 and a second arm 3. The two arms 2 and 3 are pivoted at one end to the base 4 and the other end to the hand side joint 5. The first arm 2 includes an intermediate joint 20, a base side link 21 between the base 4 and the intermediate joint 20, and a tip side link 22 between the intermediate joint 20 and the hand side joint 5. The second arm 3 includes an intermediate joint 30, a base side link 31 between the base 4 and the intermediate joint 30, and a distal end side link 32 between the intermediate joint 30 and the hand side joint 5.

  Two servo motors (actuators) 7 and 8 are connected to the base 4, the first servo motor 7 horizontally drives the first arm 2, and the second servo motor 8 horizontally drives the second arm 3.

  When the two servo motors 7 and 8 rotate in opposite directions, the two arms 2 and 3 are opened or closed at an angle formed by the base side link 21 and the base side link 31 around the base 4. The pantograph operation is controlled as a whole, and the hand-side joint 5 approaches or moves away from the base 4 side accordingly and moves in the radial direction.

  Further, when the two servo motors 7 and 8 rotate in the same direction, the hand side joint 5 is on the circumference centered on the base 4 while the angle formed by the base side link 21 and the base side link 31 is constant. Move tangentially.

  A hand link 6 extends downward from the hand side joint 5. The hand link 6 includes a drive mechanism (not shown) and a hand attached to the lower end side, and the hand moves vertically and rotates by the drive mechanism.

  Accordingly, the hand can move in the radial direction, the tangential direction, and the vertical direction with respect to the base portion 4 and rotate, and the robot arm 1 performs the parts transfer operation, assembly operation, and the like using the hand.

  Next, the case where the present invention is applied to the robot arm 1 will be described based on the first and second embodiments.

  In the first embodiment, a configuration for eliminating the force component of the reaction force will be described.

  FIG. 3 is a diagram for explaining the concept when the force component of the reaction force of the robot arm is erased, and FIG. 4 is a diagram showing an actual configuration example.

  In order to eliminate the force component of the reaction force acting in the translation direction, the pantograph mechanism (arm mechanism) 102 composed of the first arm 2 and the second arm 3 is moved left and right with respect to the base 4 as shown in FIG. And the left and right arm mechanisms 102 and 103 are operated symmetrically with respect to the joint of the base 4. Here, the other arm mechanism 103 includes a first arm 2A and a second arm 3A. In the robot arm 101 having such a two-unit structure, it means that the two arm mechanisms 102 and 103 interact with each other as a counterweight of the other arm mechanism. It is on the joint.

  Here, considering that (force component of reaction force) = (mass) × (acceleration of the center of gravity position), how the arm mechanisms 102 and 103 move in the virtual robot arm 101 of the above two-unit configuration. Even so, it can be seen that the force component of the reaction force does not occur at all because the center of gravity position does not move, that is, the acceleration is zero.

  In the present invention, as shown in FIG. 4 as an actual configuration example, one arm 2A, 3A out of the arms 2, 3, 2A, 3A is replaced with counterweights 11, 13 having the same action.

  That is, the first counterweight 11 protrudes from the base 4 via the short shaft 12 in the direction opposite to the first arm 2 (base side link 21), and the second arm 3 (base A second counterweight 13 is projected through a short shaft 14 in the direction opposite to the side link 31).

  In the robot arm 1A configured as described above, the entire center of gravity position of the first counterweight 11 and the first arm 2 always exists in the base portion 4, and the entire center of gravity position of the second counterweight 13 and the second arm 3 is the base portion. 4 is always present. Accordingly, the force component of the reaction force can be eliminated with a simple mechanism.

  In the second embodiment, a case will be described in which a configuration for reducing the rotational moment generated during the movement of the arm is added to the configuration for eliminating the force component of the reaction force described above.

  FIG. 5 is a diagram for explaining the concept when the rotational moment generated during the movement of the robot arm is reduced, and FIG. 6 is a diagram showing an actual configuration example.

  In order to reduce the moment component acting in the rotation direction, an arm mechanism as shown in FIG. 5 in which two robot arms 1A in FIG. 4 are combined is assumed. Since the position of the center of gravity of each robot arm 1A does not move as described above, the position of the center of gravity of the entire mechanism also does not move, and no force component of reaction force is generated regardless of how the two robot arms 1A move. Ingredients occur).

  Here, when the rotation of one robot arm 1A is driven to be the reverse rotation of the rotation of the other robot arm 1A, the movements of the two robot arms 1A and 1A are mirror images with the same speed and opposite directions. Become. Then, since the moment components of the reaction force generated by the two robot arms 1A and 1A are equal in magnitude and opposite in direction, their sum is zero. That is, in the arm mechanism shown in FIG. 5, one robot arm 1A interacts as a flywheel that cancels out the moment generated in the other robot arm 1A, thereby eliminating both the force component and the moment component of the reaction force. it can.

  In the present invention, as shown in FIG. 6 as an actual configuration example, one robot arm 1A is replaced with two flywheels. That is, the robot arm 1B according to the second embodiment of the present invention has a first servomotor (actuator) 7 that rotates the first arm 2 via one end side, and a rotation shaft 70 of the first servomotor 7. With respect to the first flywheel 71 that works to cancel the reaction moment, the second servomotor (actuator) 8 that rotates the second arm 3 through one end side, and the rotation shaft 80 of the second servomotor 8 And a second flywheel 81 that works to cancel the reaction moment.

  The first flywheel 71 is provided on the rotation shaft 70 of the first servomotor 7 via a gear train 72, and is reversely rotated by the gear train 72, and similarly, the second flywheel 81. Is provided on a rotation shaft 80 of the second servo motor 8 via a gear train 82, and is rotated reversely by the gear train 82.

  Thus, in the second embodiment, the flywheel 71, which works to cancel the reaction moment with respect to the rotary shafts 70, 80 of the servo motors 7, 8 that rotate the first arm 2 and the second arm 3, Since 81 is provided, the moment component of the reaction force can be greatly reduced.

  In this case, the inertia moments of the first arm 2 and the second arm 3 change depending on the arm posture, whereas the inertia moments of the flywheels 71 and 81 are constant. It cannot be erased. However, by appropriately setting the mass (moment of inertia) of the flywheels 71 and 81, the main moment component of the reaction force can be eliminated and sufficiently reduced.

  Next, detailed analysis is performed on the elimination of the force component of the reaction force and the reduction of the moment component.

FIG. 7 is a diagram modeling a robot arm to which the present invention is applied. In the figure, L is the length of the base side links 21, 31 and the tip side links 22, 32, L _A0 is the center of gravity of the base side link 21, L _A1 is the center of gravity of the tip side link 22, and L _B0 is the base side link. 31, L _B1 is the center of gravity of the distal link 32, θ _A is the attitude of the base link 21 and the distal link 32, and θ _B is the attitude of the base link 31 and the distal link 22. .

In this modeled robot arm, the position of the center of gravity of each link (base side link, tip side link) is expressed by the following equation with respect to the base.

は次式のように導かれる。なお、次式のＭ_Ａ０，Ｍ_Ａ１，Ｍ_Ｂ０，Ｍ_Ｂ１はそれぞれ基部側リンク２１、先端側リンク２２、基部側リンク３１、先端側リンク３２の質量である。

From the above formula, force component of reaction force

Is derived as follows: Note that M _A0 , M _A1 , M _B0 , and M _B1 in the following expressions are masses of the base side link 21, the tip side link 22, the base side link 31, and the tip side link 32, respectively.

  Here, by adding a counterweight to the base side links 21 and 31, the mass and the center of gravity are changed.

を満たすようにカウンタウェイト質量・位置を設定すれば、

となり、反力の力成分を消去することができる。

If you set the counterweight mass and position to satisfy

Thus, the force component of the reaction force can be eliminated.

Here, the effect of the counterweight is (mass × center of gravity position), whereas the moment of inertia is (mass × center of gravity position ² ). Therefore, in order to obtain the same effect, the moment of inertia can be reduced by increasing the mass of the counterweight and decreasing the distance from the base joint to the position of the center of gravity.

On the other hand, the moment component m of the reaction force is derived as follows. In the following expressions, I _A0 , I _A1 , I _B0 , and I _B1 are moments of inertia related to the center of gravity of the base side link 21, the tip side link 22, the base side link 31, and the tip side link 32, respectively.

Here, the above equation is transformed using the following relationship.

Then, the moment component m can be arranged as shown in the following equation.

で駆動すれば反力のモーメント成分の主要な項は消去され、

のみに低減される。 In the above equation, I _A and I _B are constants that do not depend on the arm posture. Therefore, flywheels having moments of inertia I _A and I _B are provided,

The main term of the moment component of the reaction force is erased

Only reduced.

  As described above, in the robot arms 1A and 1B according to the present invention, the counterweights 11 and 13 project from the base 4 in the direction opposite to the arms 2 and 3, so that the force component of the reaction force can be simplified. Can be erased. Further, since the flywheels 71 and 81 that act to cancel the reaction moment are provided to the rotation shafts 70 and 80 of the servomotors 7 and 8 that rotate the arms 2 and 3, the reaction moment is greatly reduced. be able to. That is, the reaction caused by the movement of the arms 2 and 3 can be eliminated or greatly reduced by a simple mechanism, thereby reducing the vibration generated in the base 4 and the installation part, and improving the working accuracy. Can do. Further, high-speed work is possible, and work efficiency can be improved.

1 is an external view of a robot arm to which the present invention is applied. It is a figure which shows schematically the arm structure of the robot arm of FIG. It is a figure for demonstrating the view in the case of deleting the force component of the reaction force of a robot arm. It is a figure which shows the actual structural example of the robot arm which erase | eliminates the force component of reaction force. It is a figure for demonstrating the view in the case of reducing the rotational moment which generate | occur | produces at the time of the motion of a robot arm. It is a figure which shows the actual structural example of the robot arm which reduces the rotational moment which generate | occur | produces at the time of an exercise | movement. It is the figure which modeled the robot arm to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Robot arm to which this invention is applied 1A, 1B Robot arm of this invention 11 1st counterweight 12 Short axis 13 2nd counterweight 14 Short axis 2 1st arm 2A 1st arm 20 Intermediate joint 21 Base side link 22 Tip Side link 3 Second arm 3A Second arm 30 Intermediate joint 31 Base side link 32 Tip side link 4 Base 5 Hand side joint 6 Hand link 7 First servo motor 70 Rotating shaft 71 First flywheel 8 Second servo motor 80 Rotating shaft 81 Second flywheel 101 Robot arm 102 Arm mechanism 103 Arm mechanism

Claims (4)

In a robot arm having one end as a base and the other end pivotally connected to a hand-side joint shaft, and having a first arm and a second arm having a joint between the one end and the other end in a pantograph manner,
A first counterweight projecting in a direction opposite to the first arm with respect to the base,
A second counterweight projecting in a direction opposite to the second arm with respect to the base ,
The entire center of gravity position of the first counterweight and the first arm is always present at the base, and the entire center of gravity position of the second counterweight and the second arm is always present at the base.
A robot arm characterized by that. A first actuator for rotating the first arm via one end side;
A first flywheel that acts to cancel the reaction moment with respect to the rotational axis of the first actuator;
A second actuator for rotating the second arm through one end side;
A second flywheel that acts to cancel the reaction moment with respect to the rotational axis of the second actuator;
The robot arm according to claim 1. The first flywheel is provided on a rotation shaft of the first actuator via a gear train, and is rotated in reverse from the rotation shaft by the gear train,
The robot arm according to claim 2, wherein the second flywheel is provided on a rotation shaft of the second actuator via a gear train, and is reversely rotated by the gear train. In a robot arm having one end as a base and the other end pivotally connected to a hand-side joint shaft, and having a first arm and a second arm having a joint between the one end and the other end in a pantograph manner,
A first actuator for rotating the first arm via one end side;
A first flywheel that acts to cancel the reaction moment with respect to the rotational axis of the first actuator;
A second actuator for rotating the second arm through one end side;
A second flywheel that acts to cancel the reaction moment with respect to the rotational axis of the second actuator;
A robot arm characterized by comprising:

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