JP2001121460A - Parallel link mechanism for robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving parallel link mechanism of spatial six-degrees of freedom having high rigidity and capable of producing high speed (high acceleration). SOLUTION: At least three unit-links 12, 13, 14 are provided in parallel between a fixing part and moving parts. Each of the respective unit-links is constituted by the following elements: three arms 121, 122 (not shown in the figure) and 123, anchors 124 fixed to a fixed-side member, a first driving articulate 125 being a rotary driving articulate of one degree of freedom connecting both the anchor and the first arm, a second driving articulate 126 being the rotary driving articulate of one degree of freedom connecting the first arm and the second arm, follower articulates 127 being a rotary follower articulate of one degree of freedom connecting the second arm and the third arm, and there axial free articulates 128 being rotary follower articulate of there degrees of freedom connecting the third arm and the moving-side member 11. The turning axis of the second driving articulate is in parallel with the turning axis of the first driving articulate. The turning axis of the follower articulate is at right angles to the turning axis of the first/second driving articulates. Further, by substituting the driving articulates for a turning angle meter/turning force meter, the parallel link mechanism can be used as a displacement/load sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel mechanism used for a drive mechanism, a displacement / load detection mechanism, or a buffer mechanism of an industrial robot in which high speed is particularly important.

[0002]

2. Description of the Related Art In industrial robots, efforts are constantly being made to increase speed and reproducibility of positioning in order to improve productivity and quality.

In order to freely move the moving part with respect to the fixed part in the industrial robot, a plurality of links must be interposed between the two parts. As a method of providing a plurality of links between the fixed unit and the moving unit, there are a serial link system in which they are arranged in series and a parallel link system in which they are arranged in parallel. In addition, when there is a parallel arrangement even in a part, it is classified into a parallel link system. The serial link method has an advantage that the moving range of the moving unit can be widened, but has a disadvantage that it is weak against a large load and that the positioning of the operating unit is low because errors of each link are accumulated. On the other hand, the parallel link method has advantages in that although the moving range is narrow, the load is distributed to each link, so that the rigidity is high and the positioning error of the moving unit is small. Here, high rigidity leads to high-speed operation (more precisely, high acceleration).

For example, in a bonding robot for bonding a lead wire to each terminal of a semiconductor chip, a moving range of a moving portion may be small, but a high-speed and high-level balance is required. As described above, in a robot requiring particularly precise and high-speed work, the parallel link method is exclusively adopted in consideration of the above characteristics.

Various proposals have been made for the parallel link. For example, JP-A-7-28110
No. 2 discloses a mechanism in which six direct-acting links are arranged in parallel between a fixed part (base) and a moving part. In JP-A-8-11080 and JP-A-8-11081,
A mechanism in which three linear actuators are arranged between a fixed part (base plate) and a moving part (end effector) is disclosed. JP-A-9-109083 discloses a mechanism in which six linear actuators are arranged between a fixed part (base part) and a moving part (end effector part).

[0006]

As described above, all of the parallel link mechanisms proposed hitherto use a linear motion actuator. Linear actuators are usually
It is driven using hydraulic pressure, a rack and pinion, a ball screw, or the like. However, since the link portion itself includes a driving element, there is a problem that the mass of the link portion is large and it is difficult to increase the speed.

The present invention has been made to solve such a problem, and an object of the present invention is to use a plurality of rotary actuators in parallel between a fixed part and a moving part to achieve high rigidity. Another object of the present invention is to provide a link mechanism capable of achieving high speed (high acceleration).

As a parallel link mechanism using a rotary actuator, six arms are arranged in parallel between a base portion (fixed portion) and an end effector portion (moving portion), and each arm is provided on the base portion. A 6-DOF parallel robot provided with a motor for driving has been developed (HE
XA. Jointly developed with Tohoku University Graduate School of Engineering, Department of Aerospace Engineering, Spacecraft Systems Laboratory, University of Montpellier, and Toyota Koki. ht
tp: //www.space.mech.tohoku.ac.jp/research/parallel
/hexa97/hexa97-j.html). The link mechanism according to the present invention employs a completely different mechanism, and has a feature that the number of links (arms) between the fixed part and the moving part may be at least three.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a parallel link mechanism for driving a first member and a second member relatively with six degrees of freedom in space.
The parallel link mechanism includes at least three unit links having a two-degree-of-freedom driving function for connecting the first member and the second member. Each unit link includes a first arm and a second arm, and a second arm. One-degree-of-freedom rotary drive joint connecting one member and the first arm, one-degree-of-freedom rotary drive one-degree-of-freedom rotary joint connecting the first arm and the second arm, and connecting the second arm and the second member And a three-degree-of-freedom rotation driven joint.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first member and the second member are
Either one corresponds to the fixed part and the other corresponds to the moving part. In the present invention, any one of the fixing portions may be used. In particular, when the present invention is used as a driving mechanism, it is desirable that the first member provided with the one-degree-of-freedom rotational driving joint is on the fixing portion side. This is because the driving joint generally has a large mass due to a motor, a speed reduction mechanism, and the like.

The first member and the second member are connected by three or more unit links. By using four or more unit links, the rigidity of the connection between the first member and the second member can be increased, and the acceleration on the moving side can be further improved.

Each unit link is composed of two arms serially connected to a first arm and a second arm, and the first member and the first arm are connected by a one-degree-of-freedom rotary drive joint (this is called a first drive joint). The first arm and the second arm are a one-degree-of-freedom rotary drive one-degree-of-freedom rotary driven joint (referred to as a second drive joint) and a second arm.
The arm and the second member are connected by a three-degree-of-freedom rotational driven joint (referred to as a third joint). The rotation axis of the first drive joint connecting the first member and the first arm and the drive rotation axis of the second drive joint connecting the first arm and the second arm are not necessarily parallel, but may be parallel. By doing so, it becomes easy to transmit the driving force from one to the other. That is, as described above, the first member is fixed, and two rotary driving sources such as motors are placed there, one drives the first driving joint in the immediate vicinity, and the other drives the belt or the parallel link mechanism. It is easy to drive the second driving joint by using it. This allows
The mass of the moving part can be made smaller, and a driving mechanism with good acceleration can be realized.

The connection points (that is, the first driving joints) between the three (or four or more) unit links and the first member are not aligned on a straight line. Also, the connection point between the unit link and the second member (that is, the third joint) is not aligned. The restrictions on the degree of freedom and arrangement of each joint, including these, are mathematically expressed as shown in FIG.

The present invention can be carried out in the following various embodiments. First, a third arm is provided between the first arm and the second arm of each unit link, and the one-degree-of-freedom rotational drive function and the one-degree-of-freedom rotational follower function of the second drive joint are separated from each other.
It may be separately allocated between the arm and the third arm and between the third arm and the second arm (of course, vice versa).

Further, these different types of unit links may be mixed and used between the first member and the second member.

In the above description, the case where the parallel link mechanism is used as the drive mechanism is described. By replacing "rotation drive" in the above description with "rotation sensitivity",
Exactly the same mechanism can be used as a parallel link sensor capable of detecting a displacement or a load (force) having six degrees of freedom in space. That is, a displacement / load sensor with six degrees of freedom can be obtained by providing a goniometer for detecting a rotation angle or a tachometer for detecting a rotational force instead of a motor or the like used for a rotary drive joint.

Further, a simple rotational elastic element made of a spring, rubber or the like can be used as a six-degree-of-freedom damper for absorbing a rapid displacement and a rapid load.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a first embodiment of the present invention, a parallel link drive mechanism using three unit links will be described. The basic structure of the parallel link drive mechanism of this embodiment is as shown in FIG. Although only the movable member 11 and the three unit links 12, 13, and 14 are illustrated in FIG. 1, the other ends (fixed ends) 12 of the unit links 12, 13, and 14 are illustrated.
Reference numerals 4, 134 and 144 are fixed to one fixed member (not shown). Hereinafter, the first unit link 12 will be described, but the configuration of the other two unit links 13 and 14 is the same.

As shown in FIG. 2, the unit link 12 of this embodiment comprises the following components. 1st arm 121, 2nd arm 122 (not shown in FIG. 1), 3 arms of 3rd arm 123 ・ Anchor 124 fixed to fixed side member 120 ・ Connection of anchor 124 and first arm 121 The first drive joint 125 is a one-degree-of-freedom rotary drive joint. The second drive joint 126 is a one-degree-of-freedom rotary drive joint that connects the first arm 121 and the second arm 122. The rotation axis of the second drive joint 126 is parallel to the rotation axis of the first drive joint 125. A driven joint 127 that is a one-degree-of-freedom rotational driven joint that connects the second arm 122 and the third arm 123; This driven joint 127
Is perpendicular to the rotation axes of the first and second drive joints 125, 126. A three-axis free joint 128, which is a three-degree-of-freedom rotational driven joint that connects the third arm 123 and the movable member 11;

The first driving joint 125 and the second driving joint 126
As described above, since the rotation axes are parallel as described above and are connected by a rigid arm (first arm 121) having no degree of freedom, for example, as shown in FIGS. And drive motors 125a, 126a for both drive joints 125, 126.
Is fixed to the fixed side member, and the parallel link mechanisms 121b to 121b
A mechanism that drives the second driving joint 126 in two degrees of freedom in 1d can be employed. Further, as shown in FIG. 6, the second driving joint 126 can be driven by the belt 121e. The arrangement of the motor and the like in FIG. 6 is the same as that in the case of FIG.

Returning to FIG. 2, the three-axis free joint 128 is
A spherical joint 128a as shown in FIG. 3A or a universal joint 128b as shown in FIG.
+ It can be realized by a combination of the bearing 128c.

As shown in FIG. 1, the unit link having the structure described above is connected to the fixed member and the movable member 1 as shown in FIG.
One unit link is provided between each unit link.
Drive and driven joints 125, 126, 127, 128 (3
The movable side member 11 can be freely driven with six degrees of freedom with respect to the fixed side member 120 by disposing the movable side member 11 so that the degree of freedom satisfies the condition of FIG. In the parallel link drive mechanism of the present embodiment, most of the motor and the power transmission mechanism are fixed to the fixed side member 120, and the moving part is substantially an arm (first
Arm to third arm) and joints (first and second driving joints, driven joints)
Only exists, so that the moving side member 1 has a large acceleration.
1 can be driven. In addition, reproducibility of positioning is high. Therefore, by using the parallel link drive mechanism of this embodiment as a micro unit of a macro-micro structure robot, high-speed and high-precision handling of a small object can be achieved while compensating for a narrow movable range which is a problem peculiar to the parallel mechanism. Can be realized. For example, it is possible to configure a robot suitable for use in the field of semiconductor manufacturing and the like, for which higher speed is required in recent years.

In the above embodiment, the first driving joint 125 and the second driving joint 126 are connected to the motors 125a and 126a (FIG. 5).
, But these were not driven joints,
By using a joint for detecting displacement, the parallel link mechanism having the configuration shown in FIG. 1 can be used as a 6-degree-of-freedom displacement sensor as it is. Since the displacement detection joint merely detects a change in the angle of the two arms connected to the joint, it can be realized by providing a rotary encoder between both arms. In addition, by using a rotational force detecting joint instead of a displacement detecting joint, a six-degree-of-freedom load sensor can be provided. The rotational force detecting joint can be realized by interposing a rotational force sensor (for example, a rod that receives a torsion with a strain gauge attached) between two arms connected to the joint.

Next, in the above embodiment, the driven joint 127 is provided between the second driving joint 126 and the three-axis free joint 128 (that is, the movable member 11). It is also possible to provide between the second drive joint 126. However, in this case, the first driving joint 125
When the power is to be transmitted between the second drive joint 126 and the second drive joint 126, the mechanism becomes complicated, so that there is little merit as a drive mechanism. Can be used without any change.

1 and 2, the second driving joint 1 is used.
26 and the driven joint 127 are separate, and the second arm 122 exists between the two. However, the second driving joint and the driven joint can be combined into one.

FIG. 4 shows four unit links 22, 23, 2 between a fixed member (not shown) and a movable member 21.
This is an example in which 4, 25 are provided. Each unit link 22, 2
As for 3, 24, and 25, those of the above embodiment (including various variations described later) can be used as they are. In the parallel link drive mechanism (or displacement sensor / load sensor) of the present embodiment (FIG. 4), the control of the arrangement and operation of each joint is slightly complicated, but the rigidity is increased, so that the acceleration performance and the reproducibility of positioning are improved. Has the feature that it can be made higher.

[Brief description of the drawings]

FIG. 1 is a basic structural diagram of a three-link parallel link driving mechanism according to an embodiment of the present invention.

FIG. 2 is a structural diagram of one unit link used in the parallel link drive mechanism of the embodiment.

FIG. 3 is a structural view showing two examples of a three-axis free joint.

FIG. 4 is a basic structural diagram of a four-link parallel link driving mechanism according to another embodiment of the present invention.

FIGS. 5A and 5B are a perspective view of a parallel link mechanism connecting a first drive joint and a second drive joint, and a plan view of a drive source portion.

FIG. 6 is a perspective view of a belt mechanism that connects a first driving joint and a second driving joint.

FIG. 7 is a mathematical expression showing the degree of freedom and the arrangement of each joint for enabling the link mechanism to operate.

[Explanation of symbols]

11, 21 ... moving side member 12, 13, 14, 22, 23, 24, 25 ... unit link 120 ... fixed side member 121, 122, 123 ... first arm, second arm, third arm 121b to 121d ... parallel Link mechanism 121e Belts 124, 134, 144 Anchor 125 First drive joint 125a First drive joint motor 126 Second drive joint 126a Second drive joint motor 127 Follower joint 128 Three-axis free joint

Claims (4)

[Claims] The first member and the second member are relatively spaced from each other by a space.
A parallel link drive mechanism driven with a degree of freedom, the parallel link mechanism comprising at least three unit links having a two-degree-of-freedom drive function for connecting a first member and a second member. The link includes a first arm and a second arm, a one-degree-of-freedom rotary drive joint (first drive joint) connecting the first member and the first arm, and a one-degree-of-freedom rotary joint connecting the first arm and the second arm. Drive 1
The rotational follower joint (second driving joint), the second arm and the second arm
And a three-degree-of-freedom rotational driven joint for connecting members. 2. The parallel link drive mechanism for a robot according to claim 1, wherein a rotation axis of the first drive joint is parallel to a drive rotation axis of the second drive joint. 3. The at least one unit link, wherein a third arm is provided between the first arm and the second arm.
The one-degree-of-freedom rotational drive function and the one-degree-of-freedom rotational follower function of the driving joint are separated and separately allocated between the first arm and the third arm and between the third arm and the second arm. The parallel link drive mechanism for a robot according to claim 1. 4. The parallel link drive mechanism according to claim 1, further comprising a rotation angle sensor or a rotation force sensor provided in place of the rotation drive source of the rotation drive joint. Degree displacement / load sensor.