JPH11887A - Parallel link manipulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parallel link manipulator capable of improving the precision of a ball nut used for expanding links and the control precision of the expansion of the links. SOLUTION: A base plate 1 and a travelling plate 2 are connected to each other via a center shaft 3 and three links 4. The center shaft 3 has the front end fixed to the center of the travelling plate 2 and the rear end passed into the center of the base plate 1 via a spline bearing 52 assembled in the movable part of a universal joint 5. Each link 4 has the front end connected to the peripheral edge of the travelling plate 2 via the universal joint 7 and the rear end connected to the peripheral edge of the base plate 1 via a ball nut 62 assembled in the movable part of the universal joint 6. The expansion of the link 4 is detected by using a displacement converter to directly detect the axial displacement of the link 4 to the ball nut 62.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel link manipulator used in an arm device of an industrial robot.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional parallel link manipulator. A universal joint 5 is arranged at a central portion of the base plate 1, and a universal joint 6 is arranged at each of three peripheral portions of the base plate 1. A ball spline bearing 52 is incorporated in the movable core portion 51 of the universal joint 5, and a rear end portion of the center shaft 3 having a spline shaft penetrates the ball spline bearing 52. On the other hand, a ball nut 69 is incorporated in the movable core portion 61 of the universal joint 6. A screw is formed at the rear end of each link 4, and the screw is fitted to the ball nut 69. Ball nut 69
Are driven by a servomotor (not shown), and each link 4 is expanded and contracted according to the rotation of the ball nut 69.

[0003] At the center of the traveling plate 2, the tip of a center shaft 3 is fixed vertically, and at the three peripheral edges of the traveling plate 2, universal joints 9 are arranged. The tips are connected respectively. An end effector 13 such as a tool is disposed on the front surface of the traveling plate 2, and various works such as painting, welding, and processing are performed on the work 14.

The universal joint 5 is a universal joint capable of tilting about two axes perpendicular to the axis of the center shaft 3, and rotation about the center axis of the center shaft 3 is restricted. The universal joint 6 is a universal joint capable of tilting about two axes orthogonal to the axis of each link 4, and the rotation of each link 4 about the axis is restricted. The universal joint 9 is a universal joint having three degrees of freedom capable of tilting around two axes orthogonal to the axis of each link 4 and rotating around the axis of each link 4.

In the parallel link manipulator having the above configuration, the three-dimensional position of the traveling plate 2 is controlled by driving the ball nut 69 to extend and contract each link 4 independently. At this time, the posture of the traveling plate 2 is restrained by the center shaft 3, and a state parallel to a concentric spherical surface centered on the swing center of the universal joint 5 is always maintained. Usually, the amount of expansion and contraction of each link 4 is converted from the rotation angle of the ball nut, and the rotation angle of the ball nut is detected by the encoder.

(Problems of the conventional device) a. In order to restrain the rotation of each link 4 driven by the ball nut 69, a ball spline is required at a fitting portion between the ball nut 69 and each link 4. However, in order to make the ball nut 69 and the ball spline coexist. In this case, a ball nut 69 having a large lead must be used, and the accuracy and rigidity are poor.

[0007] b. As a universal joint 9 connecting the traveling plate 2 and each link 4 so that no torsional force is applied to each link 4 with the change of the three-dimensional position and posture of the traveling plate 2, 3 A universal joint having a degree of freedom, for example, a spherical bearing is required.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional parallel link manipulator, and an object of the present invention is to provide a parallel link manipulator with a ball spline. The restriction on the lead of the ball nut is reduced by enabling the use of the ball nut of the type without the hole, thereby increasing the accuracy of the amount of expansion and contraction of each link and increasing the rigidity of the fitting portion between the ball nut and each link. It is in.

[0009]

The parallel link manipulator according to the present invention has a first universal joint capable of tilting about two axes at a central portion, and tilting about two axes at three positions on a peripheral portion. A base plate provided with a second universal joint, a traveling plate provided with a third universal joint capable of tilting around two axes at three peripheral edges, and a traveling plate disposed opposite to the base plate; A spline bearing incorporated in the movable core portion of the universal joint, a ball nut incorporated in the movable core portion of the second universal joint, and a front end portion fixed to the central portion of the traveling plate, and a rear end portion thereof. A center shaft supported by a base plate in a state in which rotation around the axis is restricted and slidable in the axial direction via the spline bearing and the first universal joint; A third universal joint connected to the traveling plate, a rear end portion of which is fitted with the ball nut, and three links; In a parallel link manipulator that controls the three-dimensional position of the traveling plate with respect to the base plate by independently controlling the amount of expansion and contraction of the link, the third universal joint has two degrees of freedom that restrains rotation of the link about its axis. Wherein the expansion / contraction amount detecting means is a displacement converter for directly detecting an axial displacement of the link with respect to the ball nut.

According to the parallel link manipulator of the present invention, since the amount of expansion and contraction of each link is detected using the displacement converter which directly detects the axial displacement of each link with respect to each ball nut, the tertiary movement of the traveling plate can be reduced. With the change of the original position and posture, even if the relative rotation occurs between each link whose rotation around the axis is restricted by the third universal joint and the ball nut, the amount of expansion and contraction of each link can be accurately determined. Can be detected. Therefore, it is possible to use a ball nut having no ball spline and a small lead, and a universal joint having two degrees of freedom such as a universal joint as the third universal joint. As a result, the accuracy of the control of the amount of expansion and contraction of each link can be improved, and the rigidity of the fitting portion between the ball nut and each link can be increased.

[0011]

1 to 3 show a configuration of a parallel link manipulator according to the present invention. In the drawing, 1 is a base plate, 2 is a traveling plate, 3 is a center shaft, 4 is a link, 5 is a universal joint (first universal joint), 6 is a universal joint (second universal joint), and 7 is a universal joint ( A third universal joint), 51 is a movable core part of the universal joint 5,
52 is a spline bearing, 61 is a movable core part of the universal joint 6, 62 is a ball nut, 13 is an end effector such as a tool, 14 is a work, 21 is a linear scale part of a displacement transducer, and 22 is a scale slider of a displacement transducer. Represents a part.

FIG. 1 is a schematic configuration diagram of a parallel link manipulator of the present invention. The base plate 1 is arranged on the ceiling side of the apparatus, and is supported by a support frame 12 from the periphery. The space sandwiched between the bottom surface 11 and the base plate 1 is a work area. The work 14 is fixed to the bottom surface 8 side of the apparatus, and various operations such as painting, welding, and processing are performed by the apparatus.

A universal joint 5 is arranged at the center of the base plate 1, and three universal joints 6 are arranged at a peripheral edge of the base plate 1 at positions separated from each other by 120 degrees. A ball spline bearing 52 is incorporated in the movable core portion 51 of the universal joint 5, and the rear end of the center shaft 3 having the spline shaft penetrates therein. On the other hand, a ball nut 62 is incorporated in the movable core portion 61 of the universal joint 6. A screw is formed at the rear end of each link 4, and the screw is fitted to the ball nut 62. The ball nut 62 is a servo motor 63
(FIG. 2), each link 4 expands and contracts according to the rotation of the ball nut 62.

At the center of the traveling plate 2, the tip of a center shaft 3 is fixed vertically, and at the periphery of the traveling plate 2, three universal joints 7 are located at positions 120 degrees apart from each other on the circumference. Placed,
The distal end of each link 4 is connected to each universal joint 7.

The universal joint 5 is capable of tilting about two axes perpendicular to the axis of the center shaft 3, and the rotation of the center shaft 3 about its axis is restricted. The universal joint 6 can tilt about two axes orthogonal to the axis of each link 4, and the rotation of each link 4 about the axis is restricted. Similarly, the universal joint 7 can be tilted around two axes orthogonal to the axis of each link 4, and the rotation of each link 4 around the axis is restricted.

In the parallel link manipulator having the above-described configuration, the three-dimensional position of the traveling plate 2 is controlled by driving the ball nut 62 to extend and contract each link 4 independently. At this time, the posture of the traveling plate 2 is constrained by the center shaft 3, and a state parallel to a concentric spherical surface centered on the swing center of the universal joint 5 is always maintained.

FIG. 2 is a detailed view showing the structure of the connecting portion between the rear end of each link 4 and the base plate 1 in the parallel link manipulator shown in FIG. A ball nut 62 is rotatably housed inside the movable core portion 61 of the universal joint 6, and a threaded portion formed at the rear end of the link 3 is fitted into the ball nut 62.
The ball nut 62 is driven by a servomotor 63 supported by the movable core 61. Further, the linear scale portion 21 and the roller guide 23 of the displacement converter are fixed to the movable core portion 61, and these are arranged in parallel to the axial direction of the link 4. On the other hand, at the rear end of the link 4, a bracket 24 is supported so as to be rotatable around the axis of the link 4, and a scale slider portion 22 of a displacement transducer is attached to the bracket 24. The scale slider section 22 is guided by the roller guide 23 and moves along the linear scale section 21.

FIG. 3 is a detailed view showing the structure of the connecting portion between the tip of each link 4 and the traveling plate 2 in the parallel link manipulator shown in FIG. The universal joint 7 can tilt about two axes orthogonal to the axial direction of each link 4, and the rotation of each link 4 about the axis with respect to the traveling plate 2 is restricted.

[0019]

According to the parallel link manipulator of the present invention, even if the relative rotation occurs between each link and the ball nut due to the change of the three-dimensional position and the attitude of the traveling plate, the rotation of each link can be prevented. The amount of expansion and contraction can be accurately detected. Accordingly, it is possible to use a ball nut having no ball spline and a small lead. In addition, a universal joint having two degrees of freedom, such as a universal joint, can be adopted as a joint between the distal end of each link and the traveling plate. As a result, it is possible to increase the accuracy of controlling the amount of expansion and contraction of each link and increase the rigidity of the fitting portion between the ball nut and each link. Further, the structure of the third universal joint can be simplified as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a parallel link manipulator of the present invention, (a) is a plan view, and (b) is a front view.

FIG. 2 is a detailed view showing a structure of a connecting portion between a rear end of the link and a base plate in the parallel link manipulator of the present invention, (a) is a cross-sectional view in the axial direction of the link, and (b) is A in FIG. FIG. 2 shows a cross-sectional view of a part A.

FIG. 3 is a detailed view showing a structure of a connecting portion between a link tip and a traveling plate in the parallel link manipulator of the present invention, FIG. 3 (a) is a cross-sectional view perpendicular to the axis of a center shaft, and FIG. FIG. 2 shows an axial sectional view of a shaft.

4A and 4B are diagrams showing a schematic configuration of a conventional parallel link manipulator, wherein FIG. 4A is a plan view and FIG. 4B is a front view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base plate, 2 ... Traveling plate, 3 ... Center shaft, 4 ... Link, 5 ... Universal joint (1st universal joint), 6 ... Universal joint (2nd Universal joint), 7 ... Universal joint (third universal joint), 9 ... Universal joint with three degrees of freedom (spherical bearing), 11 ... Bottom surface, 12 ... Support frame, 13 ... End effector, 14 Work, 21 Linear scale part of displacement transducer, 22 Scale slider part of displacement transducer, 23 Roller guide, 24 Bracket, 51 Movable core part, 52: Ball spline bearing, 61: Movable core part, 62: Ball nut (no ball spline), 69: Ball nut ( With Lumpur spline).

Claims (1)

[Claims] 1. A base plate having a first universal joint capable of tilting around two axes at a central portion, and a second universal joint capable of tilting around two axes at three positions on a peripheral portion; A third universal joint capable of tilting around two axes is provided at three positions on the peripheral edge, a traveling plate arranged opposite to the base plate, and a spline bearing incorporated in the movable core of the first universal joint A ball nut incorporated in the movable core portion of the second universal joint, a tip portion is fixed to a central portion of the traveling plate, and a rear end portion is the spline bearing and the first universal joint. And a center shaft supported by the base plate in a state where rotation around the axis is restricted and slidable in the axial direction, and a distal end portion is connected to the traveling plate via the third universal joint. And three links whose rear ends are fitted to the ball nuts; and an expansion / contraction amount detecting means for detecting the amount of expansion / contraction of each of the links, by independently controlling the amount of expansion / contraction of each of the links. A parallel link manipulator that controls a three-dimensional position of the traveling plate with respect to the base plate, wherein the third universal joint is a two-degree-of-freedom universal joint that restricts rotation of the link about an axis; And a displacement converter for directly detecting an axial displacement of the link with respect to the ball nut.