CN105690165B - A 2R1T Three-DOF Space Parallel Mechanism with Large Attitude Angle - Google Patents

Abstract

The invention belongs to the field of three-degree-of-freedom parallel mechanisms and particularly relates to a large-altitude-angle 2R1T three-degree-of-freedom spatial parallel mechanism. The defect that the rotating angle range of the existing 2R1T three-degree-of-freedom parallel mechanism is small is overcome. The large-altitude-angle 2R1T three-degree-of-freedom spatial parallel mechanism comprises a fixed platform on which an actuator is mounted, a moving platform, a first branch chain and a second branch chain, wherein the moving platform performs two-dimensional rotation and one-dimensional movement through the first branch chain and the second branch chain; the first branch chain comprises two active-driving movement pairs; the second branch chain comprises an active-driving movement pair; and the first and second branch chains are separately connected with the fixed platform and the moving platform so as to form a spatial parallel closed loop mechanism. The large-altitude-angle 2R1T three-degree-of-freedom spatial parallel mechanism is better in rotating flexibility, higher in precision and rigidity and easier in modularization.

Description

A 2R1T Three-DOF Space Parallel Mechanism with Large Attitude Angle

technical field

The invention belongs to the field of three-degree-of-freedom parallel mechanisms, and in particular relates to a three-degree-of-freedom space parallel mechanism with a large attitude angle 2R1T, which is a modular mechanism applied in the field of numerical control control device manufacturing.

Background technique

The parallel mechanism is a closed-loop mechanism composed of multiple branch chains. Compared with the traditional series mechanism, it has the following advantages: simple and compact structure, high rigidity, large bearing capacity per unit weight, no error accumulation, small mass of moving parts, and easy to achieve high-speed movement Etc. These advantages make up for the shortcomings of traditional numerical control devices to a certain extent. However, the parallel mechanism also has its inherent defects, especially the six-degree-of-freedom parallel mechanism, which has strong kinematic coupling, small work space, complex kinematics forward solution, irregular work space, and complex NC programming, etc. These shortcomings increase the complexity of the control and subsequent calibration work, which limits the popularization and application of parallel mechanisms to a greater extent.

In recent years, parallel mechanisms with less degrees of freedom (parallel mechanisms with less than six degrees of freedom) have attracted more and more attention and favor from researchers. Some parallel devices with few degrees of freedom have been successfully applied, such as the Sprint Z3 three-degree-of-freedom parallel spindle head developed by DS-Technology in Germany, which has achieved great success in CNC machining. As a module of the CNC machining center, the spindle head realizes one movement and two rotation degrees of freedom. The characteristics of this type of mechanism are: it is easy to realize modularization of processing, simple kinematics, and has the characteristics of decoupling or partial decoupling. The mechanism of motion decoupling is easy to control and can achieve higher motion accuracy, and decoupling motion has certain significance for motion control and trajectory planning.

In the major scientific and technological project of "high-end CNC machine tools and basic manufacturing equipment" implemented in early 2009, the functional accessories of the three-degree-of-freedom parallel mechanism and the five-axis linkage machining center equipped with such functional components were taken as one of the subjects. It can be seen that the parallel module is the key to the development of this type of equipment. From the perspective of processing flexibility and processing efficiency, the parallel module should have a high degree of rotation flexibility, and the rotation ability of the moving platform can reach 90° is the best (in order to achieve vertical and horizontal conversion, five-sided processing), and this is exactly the traditional The limitation of the parallel mechanism lies in that the rotation capability of the most influential Sprint Z3 parallel spindle head is only 40° (it cannot realize five-sided machining in the strict sense). It can be seen that breaking through the limitation of the swing angle of the traditional parallel mechanism under the premise of ensuring high stiffness is a bottleneck problem that needs to be overcome urgently in the research and development process of this type of equipment. The mechanism proposed by the invention also belongs to the three-degree-of-freedom parallel mechanism in the parallel mechanism with few degrees of freedom, and can realize two-dimensional rotation and one-dimensional movement. But it can achieve a larger rotation angle, especially one of the rotation range is larger.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the existing two-dimensional rotation and one-dimensional movement three-degree-of-freedom parallel mechanism with a small range of rotation angles. While the mechanism has the advantages of a general three-degree-of-freedom parallel mechanism, its rotation angle range is significantly improved. improve.

The present invention adopts the following technical solution to realize: a large attitude angle 2R1T three-degree-of-freedom space parallel mechanism, including a fixed platform and a moving platform on which actuators are installed, and a first branch chain and a first branch chain that can realize two-dimensional rotation and one-dimensional movement of the moving platform. The second branch chain; the first branch chain contains two actively driven kinematic pairs; the second branch chain contains one actively driven kinematic pair; the first and second branch chains are respectively connected with the fixed platform and the moving platform to form a space Parallel closed-loop mechanism.

The first branch chain is a (2-RPR & RP)+R type mixed motion branch chain, which includes a planar parallel closed-loop mechanism 2-RPR & RP and a planar parallel closed-loop mechanism connected to the rotating pair R of the moving platform. The closed-loop mechanism consists of two RPR branch chains with the same structure and one RP branch chain. The moving pairs P of the two RPR branch chains are actively driven. The axes of all the rotating pairs R of the planar parallel closed-loop mechanism are parallel to each other and parallel to the plane. The axes of the revolving pair R of the closed-loop mechanism connecting the moving platform are perpendicular to each other.

The second branch chain is a UPR type motion branch chain, the moving pair P of the branch chain is actively driven, and a rotating shaft of the U pair connected to the fixed platform is connected with the middle plane of the first branch chain. The axes of the rotating pairs R that are parallel to each other and are connected to the moving platform with the branch chain are perpendicular to each other.

The first RPR branch chain of the first branch chain is composed of the rotary block I connected to the fixed platform, the connecting rod I and the revolving pair R connecting the connecting rod I and the connecting rod II, and the second RPR branch chain is composed of the fixed platform. The platform is composed of the rotary block III of the connecting rod III, the connecting rod III and the revolving pair R connecting the connecting rod III and the connecting rod II, and the RP branch chain in the middle is composed of the rotary block II and the connecting rod II connecting the fixed platform and the connecting rod II , the moving pair P between the turning block I and the connecting rod I and the moving pair P between the turning block III and the connecting rod III are two active inputs.

The second branch chain is composed of a square frame connecting the fixed platform and the rotating block IV, a rotating block IV connecting the square frame and the connecting rod IV, and a revolving pair R connecting the connecting rod IV and the moving platform, and the rotating block IV and the connecting rod The moving pair P between IV is an active input. The rotating shaft of the moving pair connected to the square frame and the fixed platform is parallel to the plane parallel closed-loop mechanism of the first branch chain. The R axes of the revolving pairs of the platform are perpendicular to each other.

The connecting rod II includes a rod and a block connected to the rod at the bottom of the rod. There are two hinge ears at the bottom of the block. There is a rotating pair between one end of the block and the connecting rod III. There is a revolving joint between one end and the connecting rod I, and a revolving joint between the bottom of the block and the moving platform.

On the basis of the planar parallel closed-loop mechanism that can realize one-dimensional rotation and one-dimensional movement, the present invention enables the movable platform to realize another-dimensional rotation by adding an R pair connected with the movable platform and adding another branch chain, and the rotation range Larger, so that the new 2R1T parallel mechanism can achieve a larger rotation range, which is a prominent advantage of this mechanism, and overcomes the shortcomings of the limited rotation capacity of the previous parallel mechanism.

Compared with the prior art, the present invention has the following beneficial effects: (1) simple and compact structure; (2) high rigidity; (3) large working space, especially the rotating working space, which can reach 100° in one dimension (-50°~50° °), the other dimension can rotate up to 160° (-80°~80°). These advantages make the mechanism more flexible, higher processing precision, easier to realize modularization, and cooperate with other devices to realize multi-axis linkage CNC machining of complex degrees of freedom curved surface parts.

Description of drawings

Fig. 1 is the structural representation of the embodiment of the present invention,

Fig. 2 is a structural schematic diagram of the first branch chain in the mechanism shown in Fig. 1,

Fig. 3 is the structural representation of the second branch chain in the mechanism shown in Fig. 1,

Figure 4 is a schematic diagram of the structure of the connecting rod II,

Figure 5 is an exploded view of Figure 4,

In the figure: 1-fixed platform, 2-connecting rod Ⅰ, 3-rotary block Ⅰ, 4-connecting rod Ⅱ, 5-rotating block Ⅱ, 6-connecting rod Ⅲ, 7-rotating block Ⅲ, 8-connecting rod Ⅳ, 9-square frame, 10-turning block IV, 11-moving platform.

detailed description

A 2R1T three-degree-of-freedom space parallel mechanism with a large attitude angle, including a moving platform and a fixed platform on which an actuator is installed, and a line between the moving platform and the fixed platform, which is composed of a planar parallel closed-loop mechanism connected in series with R pairs. The first branch chain for two-dimensional rotation and one-dimensional movement of the moving platform, and the second branch chain. The first branch chain and the second branch chain are respectively connected to the fixed platform and the moving platform to form a space parallel closed-loop mechanism. The space closed-loop mechanism is driven by three input motions to realize two-dimensional rotation and one-dimensional movement of the moving platform. The first branch chain is a (2-RPR & RP)+R type mixed kinematic branch chain. It includes a planar parallel closed-loop mechanism, and the planar parallel closed-loop mechanism is composed of two RPR branch chains and one RP branch chain with the same structure. The moving pair P of the RPR branch chain is actively driven, and the R axes of all the rotating pairs of the planar parallel closed-loop mechanism in the first branch chain are parallel to each other, and are perpendicular to the R axis of the rotating pair connected to the moving platform of the branch chain; the second branch chain It is a UPR type motion branch chain. The moving pair P of the branch chain is actively driven. A rotating shaft of the U pair connected to the fixed platform is parallel to the R axes of all the rotating pairs of the plane parallel closed-loop mechanism in the first branch chain, and is parallel to the branch chain. The R axes of the revolving pairs that link the movable platform are perpendicular to each other. The planar parallel closed-loop mechanism in the first branch chain connects itself and the two RPR branch chains through the protruding platform of the connecting rod of the RP branch chain, and connects with the fixed platform with three rotary blocks, and its three connecting rods It can pass through the turning block vertically and slide along its own axis. The connecting rod of the second branch chain also passes through the turning block and slides along its own axis, and its turning block is connected to the square frame through the R pair, and the square frame is connected to the fixed platform through the R pair.

The specific embodiment of the present invention will be further described in conjunction with the accompanying drawings.

Embodiment: As shown in Fig. 1, it includes a fixed platform 1 on which an actuator is installed, a moving platform 11, and a first branch chain and a second branch chain connecting the moving platform and the fixed platform. The first branch chain and the second branch chain are respectively connected to the fixed platform 1 and the moving platform 11 to form a space parallel closed-loop mechanism.

The first branch chain is a (2-RPR & RP)+R type mixed kinematic branch chain, as shown in Figure 2. It includes a planar parallel closed-loop mechanism 2-RPR & RP, 2-RPR & RP consists of two RPR branches with the same structure and one RP branch. The first RPR branch chain is composed of the rotary block I3 connecting the fixed platform 1, the connecting rod I2 and the revolving pair R connecting the connecting rod I2 and the connecting rod II4. The second RPR branch chain is composed of the rotary block III7 connecting the fixed platform 1 and the connecting rod III6, the connecting rod III6 and the revolving pair R connecting the connecting rod III6 and the connecting rod II4. The RP branch chain in the middle is composed of the rotary block II5 and the connecting rod II4 connecting the fixed platform 1 and the connecting rod II4. In the first branch chain, the moving pair P between the turning block I3 and the connecting rod I2 and the moving pair P between the turning block III7 and the connecting rod III6 are two active inputs. All the R axes of the rotating pairs of the 2-RPR & RP mechanism in the first branch chain are parallel to each other, and are perpendicular to the R axes of the rotating pairs connecting the moving platform 11 of the 2-RPR & RP mechanism. The connecting rod II4 includes a rod and a block connected to the rod at the bottom end of the rod. There is a rotating pair between one end of the block and the connecting rod III6, and a rotating pair between the other end of the block and the connecting rod I2. The bottom and the moving platform 11 have a revolving pair.

The second branch chain is a UPR-type kinematic branch chain, which can also be regarded as an RRPR-type kinematic branch chain, as shown in FIG. 3 . This branch chain is made up of square frame 9 connecting fixed platform 1 and rotating block IV10, rotating block IV10 connecting square frame 9 and connecting rod IV8, and revolving pair R connecting connecting rod IV8 and moving platform 11. The mobile pair P between the branch chain turning block IV10 and the connecting rod IV8 is an active input. The rotating shaft of the kinematic pair connected between the square frame 9 and the fixed platform 1 is parallel to the R axis of all the rotating pairs of the 2-RPR & RP mechanism in the first branch chain, and is mutually parallel with the R axis of the rotating pair connecting the connecting rod IV8 and the moving platform 11. vertical.

The first branch chain and the second branch chain are respectively connected to the fixed platform 1 and the moving platform 11 to form a space parallel closed-loop mechanism. The spatial parallel closed-loop mechanism drives the moving platform 11 to realize two-dimensional rotation and one-dimensional mobile movement.

Claims (4)

1. A large attitude angle 2R1T three-degree-of-freedom space parallel mechanism, characterized in that it includes a fixed platform and a moving platform where actuators are installed, and the first branch chain and the second branch chain that can realize two-dimensional rotation and one-dimensional movement of the moving platform ; The first branch chain includes two actively driven kinematic pairs; the second branch chain includes an actively driven kinematic pair; the first and second branch chains are respectively connected with the fixed platform and the moving platform to form a space parallel closed-loop mechanism; The first branch chain is a (2-RPR & RP)+R type mixed motion branch chain, which includes a planar parallel closed-loop mechanism 2-RPR & RP and a planar parallel closed-loop mechanism connected to the rotating pair R of the moving platform. The closed-loop mechanism consists of two RPR branch chains with the same structure and one RP branch chain. The moving pairs P of the two RPR branch chains are actively driven. The axes of all the rotating pairs R of the planar parallel closed-loop mechanism are parallel to each other and parallel to the plane. The axes of the rotating pair R connected to the moving platform by the closed-loop mechanism are perpendicular to each other; The second branch chain is a UPR type motion branch chain, the moving pair P of the branch chain is actively driven, and a rotating shaft of the U pair connected to the fixed platform is connected with the middle plane of the first branch chain. The axes of the rotating pairs R that are parallel to each other and are connected to the moving platform with the branch chain are perpendicular to each other. 2. A large attitude angle 2R1T three-degree-of-freedom space parallel mechanism according to claim 1, characterized in that: the first RPR branch chain of the first branch chain is composed of a rotary block connected to the fixed platform (1) Ⅰ (3), connecting rod Ⅰ (2) and the revolving pair R connecting connecting rod Ⅰ (2) and connecting rod Ⅱ (4), the second RPR branch chain is composed of connecting fixed platform ( 1 ) and connecting rod Ⅲ ( 6) The rotary block III (7), the connecting rod III (6) and the rotating pair R connecting the connecting rod III (6) and the connecting rod II (4) are composed, and the middle RP branch chain is connected with the fixed platform (1) and The connecting rod II (4) consists of the rotary block II (5) and the connecting rod II (4), the moving pair P between the rotary block I (3) and the connecting rod I (2), the rotary block III (7) and the connecting rod The movement pair P between rod III (6) is the two active inputs. 3. A large attitude angle 2R1T three-degree-of-freedom space parallel mechanism according to claim 1 or 2, characterized in that: the second branch chain is composed of the fixed platform (1) and the turning block IV (10) The square frame (9), the rotating block IV (10) connecting the square frame (9) and the connecting rod IV (8) and the rotating pair R connecting the connecting rod IV (8) and the moving platform (11) are composed of the rotating block IV ( 10) The moving pair P between the connecting rod IV (8) is an active input, and the rotating shaft of the moving pair connected to the square frame (9) and the fixed platform (1) is parallel to all the rotating pairs R of the closed-loop mechanism in the middle plane of the first branch chain The axes are parallel to each other and perpendicular to the R axis of the rotating pair connecting the connecting rod IV (8) and the moving platform (11). 4. A large attitude angle 2R1T three-degree-of-freedom space parallel mechanism according to claim 3, characterized in that: the connecting rod II (4) includes a rod and the bottom end of the rod is connected to the rod as One block, two hinge ears at the bottom of the block, a rotating joint between one end of the block and the connecting rod III (6), a rotating joint between the other end of the block and the connecting rod I (2), and a rotating joint between the bottom of the block and the moving platform (11) There is a revolving pair.