CN110861071A - Two-rotation parallel mechanism with virtual rotation center - Google Patents
Two-rotation parallel mechanism with virtual rotation center Download PDFInfo
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- CN110861071A CN110861071A CN201911043517.8A CN201911043517A CN110861071A CN 110861071 A CN110861071 A CN 110861071A CN 201911043517 A CN201911043517 A CN 201911043517A CN 110861071 A CN110861071 A CN 110861071A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/003—Programme-controlled manipulators having parallel kinematics
- B25J9/0054—Programme-controlled manipulators having parallel kinematics with kinematics chains having a spherical joint at the base
- B25J9/0057—Programme-controlled manipulators having parallel kinematics with kinematics chains having a spherical joint at the base with kinematics chains of the type spherical-prismatic-spherical
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Abstract
The invention relates to the field of parallel robots, in particular to a two-rotation parallel mechanism with a virtual rotation center. The mechanism is provided with three branched chains, namely a UU branched chain, a first U branched chain and a second U branched chain, wherein the three branched chains are connected between a fixed platform and a movable platform; when the arrangement mode of the branched chains meets the arrangement rule provided by the invention, the movable platform has a motion mode of rotating around a basically fixed virtual rotation center with two degrees of freedom.
Description
Technical Field
The invention relates to the field of parallel robots, in particular to a two-rotation parallel mechanism with a virtual rotation center.
Background
Two-rotation parallel mechanisms with virtual rotation centers are widely used in the fields of rehabilitation medical appliances, robots and the like. At present, most of pure rotation parallel mechanisms have 3 rotational degrees of freedom, and have extremely high assembly requirements on arrangement modes of kinematic pairs inside branched chains of the parallel mechanisms, and certain geometrical spatial relationship is often required to be met. In many applications, the rotational degree of freedom is often not needed, so 2 rotational degrees of freedom are sufficient to achieve the task, and the number of drives and the cost are reduced. However, the current two-rotation parallel mechanism still has high requirements on the geometrical relationship of kinematic pairs inside or between the branched chains, and the expected movement is often difficult to realize due to the relationship of assembly errors in the actual use process.
Disclosure of Invention
The invention aims to solve the problem of designing a two-rotation parallel mechanism with a virtual rotation center, which has three branched chains and meets any one of two proposed arrangement modes, so that two-degree-of-freedom rotation of a movable platform relative to a fixed platform can be realized.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a two-rotation parallel mechanism with a virtual rotation center is provided with three branched chains, namely a UU branched chain, a first U branched chain and a second U branched chain, wherein the three branched chains are connected between a fixed platform and a movable platform; the first hook joint, the second hook joint and the third hook joint are arranged on the fixed platform, and the fourth hook joint, the first spherical pair and the second spherical pair are arranged on the movable platform; wherein U refers to a hook joint, and S refers to a ball pair; UU branched chain and US branched chain define the arrangement mode of the kinematic pairs in the branched chain, and the arrangement mode of the first and second US branched chains comprises the arrangement sequence of US and SU kinematic pairs.
The three branched chains are spatially arranged in two modes, and the fixed platform has the motion property of two-degree-of-freedom rotation relative to the movable platform in the two modes; one of the arrangement modes is: under the initial position that the movable platform is parallel to the fixed platform and is coaxial, the joint center connecting lines of the three branched chains are intersected at one point in the space, and kinematic pairs in the branched chains form alignment distribution relative to the point, namely the connecting line of the center of the first hook joint and the center of the first spherical pair, the connecting line of the center of the second hook joint and the center of the second spherical pair, and the connecting line of the center of the third hook joint and the center of the fourth hook joint are intersected at one point in the space, and two kinematic pairs in the same branched chain are aligned in a view perpendicular to the fixed platform.
The second arrangement mode is: under the initial position that the movable platform is parallel to the fixed platform and is coaxial, the joint center connecting lines of the three branched chains are different in space, namely are not intersected with each other, in the view perpendicular to the fixed platform, the projection of any two connecting lines in the view plane can generate an intersection point, and the total three intersection points jointly form a triangle.
The geometries of the slender rod in the middle of the double-headed fork rod forming the UU branched chain and the single-headed fork rod forming the first U-shaped branched chain and the second U-shaped branched chain are not limited to a straight line and can be any curve. However, the connection line between the centers of the joints inside the lower links in the initial position needs to satisfy one of two arrangement modes.
The arrangement mode of each branched chain of the parallel mechanism at the initial position needs to meet the above conditions, but as the movable platform rotates relative to the fixed platform, the connecting line of the centers of the internal joints of the branched chains can not meet the constraint conditions given by the two arrangement modes after the mechanism leaves the initial position; the movable platform can generate two-degree-of-freedom rotary motion of forward pulling, backward moving, left swinging and right swinging relative to the fixed platform, but the rotary center of the movable platform is not fixed and unchanged and can generate tiny movement within a certain range; in a first arrangement mode, the two rotary motions are decoupled and do not influence each other; however, in the second mode of arrangement, there is a certain coupling between the two rotational movements, which have an influence on each other.
Compared with the prior art, the invention has the following beneficial effects: the two arrangement modes provided by the invention are not strict geometrical constraints in space, compared with other two-degree-of-freedom parallel mechanisms, the constraint conditions of mechanical assembly are greatly relaxed, and the two-degree-of-freedom parallel mechanism is more reliable and practical in the practical application process.
Drawings
FIG. 1 is a schematic view of a two-turn parallel mechanism having a virtual center of rotation; (ii) a
FIG. 2 is a schematic view of two arrangement modes;
FIG. 3 is a schematic diagram of a first U.S. branch chain;
FIG. 4 illustrates a schematic view of a UU branched chain;
FIG. 5 is a schematic view of a single-headed yoke;
FIG. 6 is a schematic view of a dual head yoke;
FIG. 7 is a schematic view of a two degree-of-freedom rotational motion pattern;
in the figure: a head UU branched chain (1), a first U branched chain (2-1, 2-2), a second U branched chain (2-1, 2-2), a fixed platform (3), a movable platform (4), a first U pair, a second U pair, a third U pair, a fourth U pair (5-1, 5-2, 5-3, 5-4), a first spherical hinge S pair, a second spherical hinge S pair (6-1, 6-2), a single-head fork rod (7), a double-head fork rod (8)
Detailed Description
The invention is further explained with reference to the drawings.
The invention aims to solve the problem of designing a two-rotation parallel mechanism with a virtual rotation center, which has three branched chains and meets any one of two proposed arrangement modes, so that two-degree-of-freedom rotation of a movable platform relative to a fixed platform can be realized.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a two-turn parallel mechanism with a virtual center of rotation is shown in fig. 1, and is characterized in that: the mechanism is provided with three branched chains, namely a UU branched chain (1), a first U branched chain (2-1) and a second U branched chain (2-2), wherein the three branched chains are connected between a fixed platform (3) and a movable platform (4); the first hook joint, the second hook joint and the third hook joint (5-1, 5-2 and 5-3) are arranged on the fixed platform (3), and the fourth hook joint (5-4) and the first ball pair and the second ball pair (6-1 and 6-2) are arranged on the movable platform; wherein U refers to a hook joint, and S refers to a ball pair; the UU branched chain and the US branched chain define the arrangement mode of the kinematic pairs in the branched chain, and the arrangement modes of the first and second US branched chains (2-1 and 2-2) both comprise the arrangement sequence of the US kinematic pairs and the SU kinematic pairs, as shown in figure 3.
The three branched chains are spatially arranged in two modes, and the fixed platform (3) has the motion property of two-degree-of-freedom rotation relative to the movable platform (4) in the two modes; one of the arrangement modes is shown in mode 1 of fig. 2: the movable platform (4) is parallel to the fixed platform (3) and is coaxially arranged at an initial position, joint center connecting lines of the three branched chains are intersected at one point in space, kinematic pairs in the branched chains form contraposition distribution relative to the point, namely a connecting line of the center of a first hook joint (5-1) and the center of a first spherical pair (6-1), a connecting line of the center of a second hook joint (5-2) and the center of a second spherical pair (6-2), and a connecting line of the center of a third hook joint (5-3) and the center of a fourth hook joint (5-4) are intersected at one point in space, and two kinematic pairs in the same branched chain are in contraposition in a view perpendicular to the fixed platform;
the second arrangement is shown in pattern 2 of fig. 2: the movable platform (4) is parallel to the fixed platform (3) and is coaxial at the initial position, joint center connecting lines of the three branched chains are different in space, namely are not intersected with each other, in a view perpendicular to the fixed platform, projection of any two connecting lines in a view plane can generate an intersection point, and the total three intersection points form a triangle together;
the geometries of the elongated rods in the middle of the double-headed fork rod (8) constituting the UU branched chain (1) and the single-headed fork rods (7) of the first US branched chain (2-1) and the second US branched chain (2-2) are not limited to the straight line shapes drawn in fig. 5 and 6, and may be any curved line. However, the connection line between the centers of the joints inside the lower links at the initial position needs to satisfy one of two arrangement modes;
the arrangement mode of each branched chain of the parallel mechanism at the initial position needs to meet the above conditions, but along with the rotation of the movable platform (4) relative to the fixed platform (3), after the mechanism leaves the initial position, the connecting line of the centers of the internal joints of the branched chains can not meet the above geometric conditions; the movable platform (4) can generate two-degree-of-freedom rotary motion of forward pulling, backward moving, left swinging and right swinging relative to the fixed platform (3), as shown in fig. 7, but the rotary center of the movable platform is not fixed and unchanged, and can generate tiny movement within a certain range, but the main motion of the movable platform (4) is still rotary and can still be regarded as a parallel mechanism with two rotary degrees of freedom; in a first arrangement mode, the two rotary motions are decoupled and do not influence each other; however, in the second mode of arrangement, there is a certain coupling between the two rotational movements, which have an influence on each other. Three branched chains of the parallel mechanism are not provided with a power source, so that the rotary motion is often controlled by matching with rope traction or other external driving modes.
Compared with the prior art, the invention has the following beneficial effects: the two arrangement modes provided by the invention are not strict geometrical constraints in space, compared with other two-degree-of-freedom parallel mechanisms, the constraint conditions of mechanical assembly are greatly relaxed, and the two-degree-of-freedom parallel mechanism is more reliable and practical in the practical application process. The rotation center of the device is not physically present in space, and therefore, a virtual rotation center is provided.
Claims (3)
1. A two rotate parallel mechanism with virtual center of rotation which characterized in that: the mechanism is provided with three branched chains, namely a UU branched chain (1), a first U branched chain (2-1) and a second U branched chain (2-2), wherein the three branched chains are connected between a fixed platform (3) and a movable platform (4); the first hook joint, the second hook joint and the third hook joint (5-1, 5-2 and 5-3) are arranged on the fixed platform (3), and the fourth hook joint (5-4) and the first ball pair and the second ball pair (6-1 and 6-2) are arranged on the movable platform; wherein U refers to a hook joint, and S refers to a ball pair; the UU branched chain and the US branched chain define the arrangement mode of the kinematic pairs in the branched chain, and the arrangement modes of the first and second US branched chains (2-1 and 2-2) both comprise the arrangement sequence of the US kinematic pairs and the SU kinematic pairs;
the three branched chains are spatially arranged in two modes, and the fixed platform (3) has the motion property of two-degree-of-freedom rotation relative to the movable platform (4) in the two modes; one of the arrangement modes is: the movable platform (4) is parallel to the fixed platform (3) and is coaxially arranged at an initial position, joint center connecting lines of the three branched chains are intersected at one point in space, kinematic pairs in the branched chains form contraposition distribution relative to the point, namely a connecting line of the center of a first hook joint (5-1) and the center of a first spherical pair (6-1), a connecting line of the center of a second hook joint (5-2) and the center of a second spherical pair (6-2), and a connecting line of the center of a third hook joint (5-3) and the center of a fourth hook joint (5-4) are intersected at one point in space, and two kinematic pairs in the same branched chain are in contraposition in a view perpendicular to the fixed platform;
the second arrangement mode is: the movable platform (4) is parallel to the fixed platform (3) and at the initial position of the same axis, the joint center connecting lines of the three branched chains are different in space, namely are not intersected with each other, in the view perpendicular to the fixed platform, the projection of any two connecting lines in the view plane can generate an intersection point, and the total three intersection points jointly form a triangle.
2. A two-turn parallel mechanism with virtual turning center according to claim 1, characterized in that the double-headed fork (8) of the UU branch chain (1) and the single-headed fork (7) of the first US branch chain (2-1) and the second US branch chain (2-2) are formed, and the geometry of the slender rod in the middle of the two branches is not limited to a straight line but can be any curved line, but as stated in claim 1, the connection line between the joint centers inside the lower chain in the initial position needs to satisfy one of the two arrangement modes.
3. A mechanism with two parallel rotating bodies and virtual rotation center according to claim 1, characterized in that, the arrangement mode between the branches in the initial position is required to satisfy the condition of claim 1, but as the rotation of the movable platform (4) relative to the fixed platform (3) occurs, the connecting line of the joint centers inside the branches of the mechanism after leaving the initial position may not satisfy the geometric condition of claim 1; the movable platform (4) can generate two-degree-of-freedom rotary motion of forward pulling, backward moving, left swinging and right swinging relative to the fixed platform (3), but the rotary center of the movable platform is not fixed and unchanged and can generate tiny movement in a certain range; in a first arrangement mode, the two rotary motions are decoupled and do not influence each other; however, in the second mode of arrangement, there is a certain coupling between the two rotational movements, which have an influence on each other.
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| CN201911043517.8A CN110861071B (en) | 2019-10-30 | 2019-10-30 | Two-rotation parallel mechanism with virtual rotation center |
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| CN201911043517.8A CN110861071B (en) | 2019-10-30 | 2019-10-30 | Two-rotation parallel mechanism with virtual rotation center |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112171638A (en) * | 2020-09-02 | 2021-01-05 | 北京交通大学 | Light hip joint assistance exoskeleton with virtual rotation center |
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| CN1417003A (en) * | 2002-12-04 | 2003-05-14 | 北方交通大学 | Parallel robot mechanism with three-freedom rotating platform |
| CN101140005A (en) * | 2007-10-10 | 2008-03-12 | 北京交通大学 | Zigzag rod space telescopic mechanism |
| CN102275161A (en) * | 2011-07-08 | 2011-12-14 | 常州大学 | Three-rotation spherical motion mechanism |
| CN102528817A (en) * | 2012-01-13 | 2012-07-04 | 燕山大学 | Three-degree-of-freedom parallel-connection mechanical wrist |
| WO2016188368A1 (en) * | 2015-05-26 | 2016-12-01 | 韩方元 | Multi-motion-platform parallel robot construction method and parallel robots for same |
| CN106426107A (en) * | 2016-11-15 | 2017-02-22 | 常州大学 | Tension overall vibration isolation mechanism |
| CN106903678A (en) * | 2017-04-25 | 2017-06-30 | 中国科学院深圳先进技术研究院 | A kind of 3-freedom parallel mechanism with arc prismatic pair |
| CN106985134A (en) * | 2017-05-11 | 2017-07-28 | 重庆邮电大学 | It is a kind of that there is the 3-freedom parallel mechanism for being hinged moving platform |
-
2019
- 2019-10-30 CN CN201911043517.8A patent/CN110861071B/en not_active Expired - Fee Related
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1417003A (en) * | 2002-12-04 | 2003-05-14 | 北方交通大学 | Parallel robot mechanism with three-freedom rotating platform |
| CN101140005A (en) * | 2007-10-10 | 2008-03-12 | 北京交通大学 | Zigzag rod space telescopic mechanism |
| CN102275161A (en) * | 2011-07-08 | 2011-12-14 | 常州大学 | Three-rotation spherical motion mechanism |
| CN102528817A (en) * | 2012-01-13 | 2012-07-04 | 燕山大学 | Three-degree-of-freedom parallel-connection mechanical wrist |
| WO2016188368A1 (en) * | 2015-05-26 | 2016-12-01 | 韩方元 | Multi-motion-platform parallel robot construction method and parallel robots for same |
| CN106426107A (en) * | 2016-11-15 | 2017-02-22 | 常州大学 | Tension overall vibration isolation mechanism |
| CN106903678A (en) * | 2017-04-25 | 2017-06-30 | 中国科学院深圳先进技术研究院 | A kind of 3-freedom parallel mechanism with arc prismatic pair |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112171638A (en) * | 2020-09-02 | 2021-01-05 | 北京交通大学 | Light hip joint assistance exoskeleton with virtual rotation center |
| CN112171638B (en) * | 2020-09-02 | 2022-01-28 | 北京交通大学 | Light hip joint assistance exoskeleton with virtual rotation center |
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