WO2019046898A1

WO2019046898A1 - Translational parallel manipulator

Info

Publication number: WO2019046898A1
Application number: PCT/AU2018/050968
Authority: WO
Inventors: Chao Chen; Keenan Granland
Original assignee: Monash University
Priority date: 2017-09-08
Filing date: 2018-09-07
Publication date: 2019-03-14

Abstract

A translational parallel manipulator (1) including: a base (3); a work platform (7); three scissors mechanisms (5) respectively interconnecting the base to the work platform, each scissors mechanism having a plurality of pairs of pivotally connected crossed link members (15), the link members providing a pair of free end portions (21) thereof at each end of the scissors mechanism; the base including three linear base guides (9) located on a common plane, each linear base guide respectively supporting a slide mount (11) for sliding linear movement thereon, each slide mount being respectively connected to a said end of one of said scissors mechanisms, the pair of link member free end portions at said end being respectively connected to the slide mount by first and second connections (23,25), the first connection being fixedly located on the slide mount, the second connection being displaceable relative to the first connection, said first and second connections being rotatable about a rotational axis parallel to a vector (27) between said first and second connections, each said slide mount further supporting a linear actuator for controlling the displacement of the second connection relative to the first connection, and thereby the extension and contraction of the scissors mechanism; the work platform including three linear platform guides (29), each linear platform guide being respectively connected to the opposing end of a said scissors mechanism, the pair of link member free end portions at an opposing said end thereof being respectively connected by third and fourth connections (31,33) to a said linear platform guide, the third connection being fixedly located on the linear platform guides, the fourth connection being displaceable relative to the third connection, the third and fourth connections being rotatable about a rotational axis parallel to a vector (30) between the third and fourth connections, said first, second, third and fourth connections being universal connections allowing rotation around two pivotal axes; wherein the work platform is constrained for movement generally parallel to the common plane of the base.

Description

TRANSLATIONAL PARALLEL MANIPULATOR

FIELD OF THE INVENTION

[0001] The present invention is generally directed to mechanical assemblies for controlling the position of an object within a workspace, and is in particular directed to a translational parallel manipulator that provides translational motion for an object such as a work platform.

BACKGROUND TO THE INVENTION

[0002] There has been an increasing use of automation in areas including manufacturing, materials handling, and medical applications. In order to allow for increased automation, mechanical assemblies have been developed to allow for the position of objects to be mechanically controlled.

[0003] Mechanical assemblies have therefore been developed that allow for either or both translational and rotation motion of a supported object to be controlled.

[0004] International Publication Number WO2010/128849 (Technische Universiteit Delft et al.) describes a Delta robot mechanism which utilises a parallelogram arm structure to control the motion of a platform. Such mechanisms however only operate within a small spherical workspace, and are limited in the extent of movement in any one direction.

[0005] US Patent US6729202 (Universite Laval) describes a Cartesian parallel manipulator utilising at least three support legs, and joint members pivotally supported on the support members to support and control the translational motion of a support platform. The mechanism is also limited in the extent of movement of the platform in any one direction.

[0006] In 'D.J. Gonzalez and H.H. Asada "Design and Analysis of 6-DOF Triple Scissor Extender Robots with Applications in Aircraft Assembly", I EE Robotics and Automation Letters, Vol. 2, No. 3, July 2017, p1420 to 1427', there is described a parallel robot mechanism using three separate scissor assemblies to allow for 6 Degree-of-Freedom (DOF) motion of the supported object. While allowing for large movement in a vertical direction, the robot mechanism is relatively complicated in design requiring six linear actuators positioned in a star pattern to enable the mechanism to operate and allow for 6 DOF movement. [0007] The above discussion of background art is included to explain the context of the present invention. It is not to be taken as an admission that the background art was known or part of the common general knowledge at the priority date of any one of the claims of the specification.

[0008] It would be advantageous to be able to provide a mechanical assembly that can provide translational motion for a supported object with 3 DOF while also allowing for relatively large movement of that object in a specific direction.

SUMMARY OF THE INVENTION

[0009] With this in mind, the present invention provides a translational parallel manipulator including:

a base;

a work platform;

three scissors mechanisms respectively interconnecting the base to the work platform, each scissors mechanism having a plurality of pairs of pivotally connected crossed link members, the link members providing a pair of free end portions thereof at each end of the scissors mechanism;

the base including three linear base guides located on a common plane, each linear base guide respectively supporting a slide mount for sliding linear movement thereon, each slide mount being respectively connected to a said end of one of said scissors mechanisms, the pair of link member free end portions at said end being respectively connected to the slide mount by first and second connections, the first connection being fixedly located on the slide mount, the second connection being displaceable relative to the first connection, said first and second connections being rotatable about a rotational axis parallel to a vector between said first and second connections, each said slide mount further supporting a linear actuator for controlling the displacement of the second connection relative to the first connection, and thereby the extension and contraction of the scissors mechanism;

the work platform including three linear platform guides, each linear platform guide being respectively connected to the opposing end of a said scissors mechanism, the pair of link member free end portions at an opposing said end thereof being respectively connected by third and fourth connections to a said linear platform guide, the third connection being fixedly located on the linear platform guides, the fourth connection being displaceable relative to the third connection, the third and fourth connections being rotatable about a rotational axis parallel to a vector between the third and fourth connections, said first, second, third and fourth connections being universal connections allowing rotation around two pivotal axes; wherein the work platform is constrained for movement generally parallel to the common plane of the base.

[0010] The vector between the third and fourth connections are preferably maintained parallel to the vector between the first and second connections.

[0011] Each said linear base guide may be in the form of a guide channel for slidably accommodating a said slide mount. Alternatively, each said linear base guide may be in the form of an elongate bar, and each slide mount including a pair of bush assemblies may be respectively connected to the first and second connections. Each said linear platform guide may be in the form of an elongate bar, and the third and fourth connections may be respectively connected to the linear base guide by a bush assembly.

[0012] According to one preferred embodiment, the linear base guides are of substantially equal length, and are positioned in the shape of an equilateral triangle. Furthermore, the linear platform guides are of substantially equal length, and are positioned in the shape of an equilateral triangle.

[0013] According to another preferred embodiment, the linear base guides are positioned in the shape of three sides of a square or rectangle, with an angle substantially 90 degrees between immediately adjacent linear base guides. Furthermore, the linear platform guides are positioned in the shape of three sides of a square or rectangle, with an angle

substantially 90 degrees between immediately adjacent linear platform guides.

[0014] According to a further preferred embodiment, the linear base guides are positioned in an obtuse configuration, with an angle greater than 90 degrees between immediately adjacent linear base guides. Furthermore, the linear platform guides are positioned in an obtuse configuration, with an angle greater than 90 degrees between immediately adjacent linear platform guides.

[0015] The work platform preferably includes a substantially flat work surface held substantially parallel to the common plane of the base during movement thereof.

[0016] The crossed link members of the scissors mechanism are preferably pivotally joined about an intermediate portion of each link member, the end portions of each link member being pivotally connected to an adjacent link member end portion, or to said first, second, third or fourth universal connections.

[0017] The first and second universal connections respectively may include a U-Shaped link extending from each said link member free end portion, and connected via a universal joint member to a parallel link pair supported by the slide mount. The third and fourth universal connections respectively may include a U-Shaped link extending from each said link member free end portion, and connected via a universal joint member to a bush assembly connected to the linear platform guide.

[0018] The translational parallel manipulator according to the present invention can provide translational motion to an object such as a work platform with 3 DOF, while also allowing for large movement of that object in a specific direction. Furthermore, the present invention can achieve this using a relatively simple construction using only three linear actuators. The translational parallel manipulator can be mounted on a horizontal or inclined floor or roof surface, or a vertical or inclined wall surface. The platform may be adapted to support different devices including 3D printing elements, or manipulation devices for picking and placing different elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] It will be convenient to further describe the invention with respect to the

accompanying drawings which illustrate preferred embodiments of the translational parallel manipulator according to the present invention. Other embodiments of the invention are possible, and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

[0020] In the drawings:

[0021] Figure 1 is a perspective view of a first preferred embodiment of a translational parallel manipulator (TPM) according to the present invention;

[0022] Figure 2 is a perspective view of a base of the TPM of Figure 1 ;

[0023] Figure 3 is a detailed view of a slide mount and scissors mechanism of the TPM of Figure 1 ;

[0024] Figure 4 is a detailed view of a work platform of the TPM of Figure 1 ;

[0025] Figure 5 is a partial view of the TPM of Figure 1 showing the passive and active components thereof;

[0026] Figure 6 is a second preferred embodiment of a translational parallel manipulator according to the present invention; [0027] Figure 7 is a third preferred embodiment of a translational parallel manipulator according to the present invention; and

[0028] Figure 8 is a fourth preferred embodiment of a translational parallel manipulator according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0029] Referring initially to Figures 1 to 5, there is shown a first preferred embodiment of a translational parallel manipulator (TPM) 1 according to the present invention. As shown in Figure 1 , the TPM 1 includes a base 3, three scissors mechanisms 5, and a work platform 7.

[0030] Referring now to Figure 2, the embodiment of the TPM 1 shown in Figure 1 includes three linear base guides 9 that are of equal length and positioned in the shape of an equilateral triangle, and supported on a common plane. Each linear base guide 9 slidably supports therein a slide mount 1 1.

[0031] Referring now to Figure 3, each scissors mechanism 5 includes a plurality of crossed link members 15. Each link member 15 is pivotally connected about an intermediate portion 17 thereof to an immediately adjacent link member 15. Each link member 15 has opposing end portions 19 pivotally connected to the end portion of an adjacent link member 15. In the assembled scissors mechanism 5, the link members 15 provide a pair of free end portions 21 at each end of the scissors mechanism 5. A U-shaped link 22 is provided at the end of each free end portion 21 , each U-shaped link 22 forming part of a universal connection that will now be described.

[0032] The free end portions 21 at one end of the scissors mechanism 5 are respectively connected to a slide mount 11 via universal connections formed by the U-Shaped link 22, a cooperating parallel link pair 28 mounted on the slide mount 1 1 , and a universal joint member 36 that pivotally connects the U-shaped link 22 for pivotal motion about a first axis, and is pivotally connected to the parallel link pair 28 about a second axis extending 90 degree relative to the first axis. Therefore, each universal connection allows pivotal motion in two axes. One free end portion 21 is therefore connected by a first universal connection 23 to the slide mount 1 1. The second free end portion 21 is therefore connected by a second universal connection 25 to the slide mount 1 1. The first universal connection 23 is however fixedly located on the slide mount 11 , while the second universal connection 25 is displaceable along the slide mount 11 towards or away from the first universal connection 23 in the direction shown by line 26. The first and second universal connections 23, 25 can be rotated about a vector 27 extending between said universal connections 23, 25 in a direction shown by direction line 24. [0033] Referring now to Figure 4, the free end portions 21 at the opposing end of the scissors mechanism 5 is connected to the work platform 7 by a linear platform guide 29 in the form of an elongate bar. The free end portions 21 are respectively connected by a third universal connection 31 and fourth universal connection 33 to the linear platform guide 29 via bush mechanisms 35 and 37, respectively. The third and fourth universal connections 31 , 33 are respectively formed by the U-shaped link 22 connected via a universal joint member 38 to the bush assemblies 35, 37 supported on the linear platform guide 29. The third and fourth universal connections 31 ,33 allow for pivotal movement about two axes, while the bush assemblies 35, 37 allowing for rotation of the third and fourth universal connections 31 , 33 about a vector 30 extending between the said universal connections 31 , 33 in a direction as shown by direction arrow 32. The third universal connection 31 is however fixedly located on the linear platform guide 29, while the fourth universal connection 33 is displaceable towards or away from the third universal connection 31. The fourth universal connection 33 is therefore moveable in the direction shown by direction arrow 34.

[0034] Linear actuators (not shown) are mounted on each slide mount 11 , and control the relative displacement of the second universal connection 25 to the first universal connection 23. This controls the extension or retraction of the associated scissors mechanism 5 (see Hi(di) in Figure 5).

[0035] In each of the scissors mechanisms 5, the vector 27 between the first and second universal connections 23, 25 is held parallel with the associated vector 30 extending between the third and fourth universal connections 31 , 33. This ensures that the orientation of the work platform 7 is held parallel to the common plane occupied by the three linear base guides 9.

[0036] Figure 5 shows in more detail the various passive and active components of the motion of the different integers of the TPM 1. The passive components include Di, the sliding displacement of the slide mount 11 along the linear base guide 9, and ai, the angle of rotation of the second universal connection 25. The active components include di, the distance between the first and second universal connections 23, 25 and Hi(di), the extension or retraction of the scissors mechanism 5. Hi(di) is a function of di and can also be altered by varying the length and number of crossed link members 15 used in the scissors mechanism 5.

[0037] Figure 6 shows a second preferred embodiment of the TPM 1 a according to the present invention. This embodiment is similar to the embodiment shown in Figures 1 to 5 in utilising a base in the shape of an equilateral triangle. The principle difference is that the linear base guide 9a is provided by an elongate bar upon which are provided a pair of bush assemblies 41 , 42 providing the slide mount for the TPM 1a. The operation is however identical to the TPM 1 shown in Figures 1 to 5.

[0038] Figure 7 shows a third preferred embodiment of a TPM 1 b according to the present invention which has a similar construction to the embodiment shown in Figure 6. The primary difference is that the linear base guides 9b are positioned in the shape of three sides of a square with an angle of substantially 90 degrees between each immediately adjacent linear base guides 9b. This arrangement allows for greater mobility in the x and y axis direction and also provides for a larger reachable workspace.

[0039] Figure 8 shows a fourth preferred embodiment of a TPM 1 c according to the present invention. While TPM 1c has a construction similar to the embodiments shown in Figures 6 and 7, the linear base guides 9c are positioned in an obtuse configuration, with an angle greater than 90 degrees between immediately adjacent linear base guides 9c. This arrangement also provides a good movement range in the x and y axis, but limits movement of the platform 9d away from the base of the TPM 1 c.

[0040] Other configurations for the TPM 1 are also possible as long as all three linear base guides 9 are not parallel to each other. The scissors mechanisms 5 should preferably have enough extension range to reach the furthest part of the base 3 perpendicular to its own axis to maximise the workspace. The extension of the scissors mechanisms 5 could alternatively be limited to shape the reachable workspace thereby reducing the potential workspace.

[0041] Modifications and variations as would be deemed obvious to the person skilled in the art are included within the ambit of the present invention as claimed in the appended claims.

Claims

1. A translational parallel manipulator including:

a base;

a work platform;

the work platform including three linear platform guides, each linear platform guide being respectively connected to the opposing end of a said scissors mechanism, the pair of link member free end portions at an opposing said end thereof being respectively connected by third and fourth connections to a said linear platform guide, the third connection being fixedly located on the linear platform guides, the fourth connection being displaceable relative to the third connection, the third and fourth connections being rotatable about a rotational axis parallel to a vector between the third and fourth connections, said first, second, third and fourth connections being universal connections allowing rotation around two pivotal axes;

wherein the work platform is constrained for movement generally parallel to the common plane of the base.

2. A translational parallel manipulator according to claim 1 , wherein the vector between the third and fourth connections is maintained parallel to the vector between the first and second connections.

3. A translational parallel manipulator according to claim 1 or 2, wherein each said linear base guide is in the form of a guide channel for slidably accommodating a said slide mount.

4. A translational parallel manipulator according to claim 1 or 2, wherein each said linear base guide is in the form of an elongate bar, and each slide mount including a pair of bush assemblies respectively connected to the first and second connections.

5. A translational parallel manipulator according to any one of the preceding claims, wherein each said linear platform guide is in the form of an elongate bar, and the third and fourth connections are respectively connected to the linear base guide by a bush assembly.

6. A translational parallel manipulator according to any one of the preceding claims, wherein the linear base guides are of substantially equal length, and are positioned in the shape of an equilateral triangle.

7. A translational parallel manipulator according to claim 6, wherein the linear platform guides are of substantially equal length, and are positioned in the shape of an equilateral triangle.

8. A translational parallel manipulator according to any one of claims 1 to 5, wherein the linear base guides are positioned in the shape of three sides of a square or rectangle, with an angle substantially 90 degrees between immediately adjacent linear base guides.

9. A translational parallel manipulator according to claim 8, wherein the linear platform guides are positioned in the shape of three sides of a square or rectangle, with an angle substantially 90 degrees between immediately adjacent linear platform guides.

10. A translational parallel manipulator according to any one of claims 1 to 5, wherein the linear base guides are positioned in an obtuse configuration, with an angle greater than 90 degrees between immediately adjacent linear base guides.

11. A translational parallel manipulator according to claim 10, wherein the linear platform guides are positioned in an obtuse configuration, with an angle greater than 90 degrees between immediately adjacent linear platform guides.

12. A translational parallel manipulator according to any one of the preceding claims, wherein the work platform includes a substantially flat work surface held substantially parallel to the common plane of the base during movement thereof.

13. A translational parallel manipulator according to any one of the preceding claims, wherein the crossed link members of the scissors mechanism are pivotally joined about an intermediate portion of each link member, the end portions of each link member being pivotally connected to an adjacent link member end portion, or to said first, second, third or fourth universal connections.

14. A translational parallel manipulator according to any one of the preceding claims, wherein the first and second universal connections respectively include a U-Shaped link extending from each said link member free end portion, and connected via a universal joint member to a parallel link pair supported by the slide mount.

15. A translational parallel manipulator according to any one of the preceding claims, wherein the third and fourth universal connections respectively include a U-Shaped link extending from each said link member free end portion, and connected via a universal joint member to a bush assembly connected to the linear platform guide.