Six-degree-of-freedom weakly coupled parallel mechanism and construction method thereof

Abstract

The application relates to a six-degree-of-freedom weakly-coupled parallel mechanism and a comprehensive method thereof, which comprises a moving platform, a fixed platform and a plurality of branch chains, the moving platform and the fixed platform are provided with the plurality of branch chains, a first PPPS branch chain and a second PPPS branch chain are respectively arranged at two acute-angle vertexes in the moving platform and the fixed platform, a first CPS branch chain and a second CPS branch chain are respectively arranged on two right-angle sides in the moving platform and the fixed platform, and a PPRPU branch chain is arranged at a right-angle vertex in the moving platform and the fixed platform. The application provides a 2PPPS-2CPS-PPRPU six-degree-of-freedom weakly-coupled parallel mechanism, which has the characteristics of bearing capacity and decoupling characteristics, is more compact in structure, has higher output precision and the like, and based on the screw theory, adopts a mode of splitting the whole mechanism into plane sub-mechanisms and space sub-mechanisms for separate design, and provides a comprehensive method of the multi-degree-of-freedom weakly-coupled parallel mechanism, so that the comprehensive design method and process of the weakly-coupled parallel mechanism are simplified.

Description

Technical Field

[0001] The present invention belongs to the technical field of parallel mechanisms, and in particular relates to a six-degree-of-freedom weak-coupling parallel mechanism and a construction method thereof. Background Art

[0002] Six-degree-of-freedom parallel mechanisms are widely used in automobiles, ships, aircraft, aerospace equipment, and other fields. However, these mechanisms exhibit strong coupling, which increases the complexity of their control systems and reduces the mechanism's motion precision, thus restricting their application. Compared to strongly coupled mechanisms, weakly coupled mechanisms offer advantages such as higher motion precision, easier dynamic modeling, and simpler control. They hold great promise for application in high-precision robotics.

[0003] In most cases, the load-bearing and stiffness characteristics in the direction of gravity have a great influence on the working performance of the mechanism. By decoupling the degrees of freedom in the direction of gravity, the output accuracy of the mechanism in the direction of gravity can be improved. However, the traditional weakly coupled parallel mechanism branches contain closed-loop units, which have a complex structure, and the stiffness and load-bearing capacity in the direction of decoupling degrees of freedom are poor. There is still a lack of six-degree-of-freedom decoupling parallel mechanisms that can be used in large-load situations. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a six-degree-of-freedom weakly coupled parallel mechanism and a construction method thereof, and synthesizes a 2PPPS-2CPS-PPRPU six-degree-of-freedom weakly coupled parallel mechanism, which can combine load-bearing capacity and decoupling characteristics, and has the characteristics of more compact structure and higher output accuracy. Based on the spiral theory, the overall mechanism is split into planar sub-mechanisms and spatial sub-mechanisms for separate design, and a new method for synthesizing multi-degree-of-freedom weakly coupled parallel mechanisms is proposed, which simplifies the mechanism synthesis design method and process.

[0005] The technical solution adopted by the present invention is a six-degree-of-freedom weak-coupling parallel mechanism, which includes a moving platform, a fixed platform, and two PPPS branches, two CPS branches and one PPRPU branch arranged between the moving platform and the fixed platform. The moving platform and the fixed platform are both in the shape of a right-angled triangle. A first PPPS branch, a first CPS branch, a PPRPU branch, a second CPS branch and a second PPPS branch are arranged between the moving platform and the fixed platform; the first PPPS branch and the second PPPS branch are respectively arranged at the vertices of two acute angles in the moving platform and the fixed platform, and the first PPPS branch and the first CPS branch are respectively arranged at the vertices of two acute angles in the moving platform and the fixed platform, and the first PPPS branch and the first CPS branch are respectively arranged at the vertices of two acute angles in the moving platform and the fixed platform. The two PPPS branches have the same structure. The first PPPS branch and the second PPPS branch both include a first slide rail, a second slider, a second slide rail, a second slider, a first moving pair and a first ball pair. The first slide rail is fixedly arranged on the fixed platform, and the first end of the second slider is connected to the first slide rail moving pair. The second end of the second slider is provided with the second slide rail, and the first end of the second slider is connected to the second slide rail moving pair. The second end of the second slider is connected to the first end of the first moving pair, and the second end of the first moving pair is connected to the moving platform through the first ball pair. The first CPS The branch chain and the second CPS branch chain are respectively arranged on two right-angled sides of the moving platform and the fixed platform, and the first CPS branch chain and the second CPS branch chain have the same structure. The first CPS branch chain and the second CPS branch chain both include a third slide rail, a third slider, a first rotation pair, a second moving pair and a second ball pair. The third slide rail is fixed on the fixed platform. The first end and the second end of the third slider are respectively connected to the third slide rail and the fixed part of the first rotation pair, and together form a cylindrical pair on the third slide rail. The rotating part of the first rotation pair is connected to the first end of the second moving pair, and the first end of the second moving pair is connected to the first end of the second moving pair. The two ends are connected to the moving platform through the second ball pair; the PPRPU branch chain is arranged at the right-angle vertex between the moving platform and the fixed platform, and the PPRPU branch chain includes a fourth slide rail, a fourth slider, a fifth slide rail, a rotating platform, a third moving pair and a Hooke's hinge. The fourth slide rail is fixed on the fixed platform, and the first end of the fourth slider is connected to the fourth slide rail moving pair, the second end of the fourth slider is connected to the fifth slide rail moving pair, and the first end of the third moving pair is connected to the fifth slide rail through the rotating platform, and the second end of the third moving pair is connected to the moving platform through the Hooke's hinge.

[0006] Further, the first drive of the six-degree-of-freedom weakly-coupled parallel mechanism is arranged at the first moving pair in the first PPPS branch, the second drive is arranged at the second moving pair in the first CPS branch, the third drive is arranged at the rotating platform in the PPRPU branch, the fourth drive is arranged at the third moving pair in the PPRPU branch, the fifth drive is arranged at the first moving pair in the second PPPS branch, and the sixth drive is arranged at the second moving pair in the second CPS branch.

[0007] Preferably, the first slide rails in the first and second PPPS branches are perpendicular to the second slide rails in the corresponding branches, and the first slide rails in the first and second PPPS branches are parallel to the legs of the fixed platform 7, and the axes of the first moving pairs in the first and second PPPS branches are perpendicular to the first and second slide rails in the corresponding branches.

[0008] Preferably, the second moving pairs in the first and second CPS branches are perpendicular to the third slide rails in the corresponding branches, and the third slide rails in the first and second CPS branches are parallel to the legs of the fixed platform.

[0009] Preferably, the fourth and fifth slide rails in the PPRPU branch are perpendicular to each other, and the rotating direction of the rotating platform is perpendicular to the fourth and fifth slide rails, the axis of the third moving pair is in the same direction as the rotating direction of the rotating platform, the first rotating axis of the hook joint is parallel to the fourth slide rail, and the second rotating axis of the hook joint is parallel to the fifth slide rail.

[0010] In another aspect of the present application, a construction method of a six-degree-of-freedom weakly-coupled parallel mechanism is provided, which comprises the following steps:

[0011] S1, determining the desired motion degrees of freedom of the parallel mechanism;

[0012] S2, according to the desired motion degrees of freedom of the parallel mechanism, dividing the desired motion degrees of freedom into planar degrees of freedom and spatial degrees of freedom according to the nature of the degrees of freedom, and dividing the overall parallel structure into a planar sub-parallel mechanism and a spatial sub-parallel mechanism;

[0013] S3, based on the screw theory, the reciprocal product of the force screw and the motion screw is the instantaneous power generated by the force screw on the motion screw, and according to the degrees of freedom and weak coupling requirements of the planar sub-parallel mechanism and the spatial sub-parallel mechanism, the reciprocal product of the transmission force screw matrix and the output motion screw matrix of the planar sub-parallel mechanism and the spatial sub-parallel mechanism branch is obtained. The condition that the reciprocal product is a triangular matrix, and the transmission force screw form of the motion branch of the planar sub-parallel mechanism and the spatial sub-parallel mechanism is solved.

[0014] S4, according to the decoupling branch only driving screw pair output motion work, namely the transmission force screw and driving screw reciprocity product is not zero, determine the form of driving screw in the branch of planar sub-parallel mechanism and spatial sub-parallel mechanism;

[0015] S5, according to the decoupling branch non-driving screw pair output motion does not work, namely the transmission force screw and non-driving screw reciprocity product is zero, determine the form of non-driving screw in the branch of planar sub-parallel mechanism and spatial sub-parallel mechanism;

[0016] S6, the driving screw and non-driving screw obtained in step S4 and step S5 are arranged and combined, so that each branch of the planar sub-parallel mechanism and the spatial sub-parallel mechanism with specific degrees of freedom and decoupling characteristics is obtained;

[0017] S7, the degrees of freedom of each branch in the planar sub-parallel mechanism and the spatial sub-parallel mechanism are supplemented to meet the overall mechanism motion degrees of freedom;

[0018] S8, the designed planar sub-parallel mechanism and spatial sub-parallel mechanism are combined, and the positions of the branch chains are arranged, so that the desired multi-degree-of-freedom weakly coupled parallel mechanism is obtained;

[0019] S9, the degrees of freedom and decoupling characteristics of the designed parallel mechanism are calculated and verified, and the parallel mechanism construction work with weak coupling characteristics is completed.

[0020] The characteristics and advantages of the present application are:

[0021] 1, the six-degree-of-freedom weakly coupled parallel mechanism and the construction method thereof provided by the present application, based on screw theory, propose a new method for synthesizing multi-degree-of-freedom weakly coupled parallel mechanism, according to the motion characteristics of the degrees of freedom, the overall parallel mechanism is divided into multiple sub-parallel mechanisms for design, and taking six degrees of freedom as an example, the synthesis process of the complex six-degree-of-freedom weakly coupled parallel mechanism is converted into the synthesis of three-degree-of-freedom weakly coupled parallel mechanism, which is relatively easy, and the overall parallel mechanism is formed by combining two sub-parallel mechanisms.

[0022] 2, the six-degree-of-freedom weakly coupled parallel mechanism and the construction method thereof provided by the present application, a 2PPPS-2CPS-PPRPU six-degree-of-freedom weakly coupled parallel mechanism is synthesized, which can have bearing capacity and decoupling characteristics, has the characteristics of more compact structure, higher output precision and wider applicability. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the overall structure schematic diagram of the present application;

[0024] Figure 2 is the PPRS branch chain structure schematic diagram of the parallel mechanism of the present application;

[0025] Figure 3 is a schematic view of the CPS branch structure of the parallel mechanism of the present application;

[0026] Figure 4 is a schematic view of the PPRPU branch structure of the parallel mechanism of the present application;

[0027] Figure 5 is a schematic view of the construction method flow of the parallel mechanism of the present application.

[0028] Main reference signs:

[0029] moving platform 1; first PPPS branch 2; first slide rail 21; second slide block 22; second slide rail 23; second slide block 24; first moving pair 25; first spherical pair 26; first CPS branch 3; third slide rail 31; third slide block 32; first rotating pair 33; second moving pair 34; second spherical pair 35; PPRPU branch 4; fourth slide rail 41; fourth slide block 42; fifth slide rail 43; rotating platform 44; third moving pair 45; hook hinge 46; second CPS branch 5; second PPPS branch 6; fixed platform 7. DETAILED DESCRIPTION

[0030] To make the technical content, structural features, purposes achieved and effects of the present application clear, the following will be described in detail in combination with the drawings of the specification.

[0031] A six-degree-of-freedom weakly coupled parallel mechanism of the present application, as shown in the figure, comprises a moving platform 1, a fixed platform 7 and two PPPS branches, two CPS branches and a PPRPU branch arranged between the moving platform 1 and the fixed platform 7. Figure 1 The moving platform 1 and the fixed platform 7 are both in the shape of a right-angled triangle, and the first PPPS branch 2, the first CPS branch 3, the PPRPU branch 4, the second CPS branch 5 and the second PPPS branch 6 are arranged between the moving platform 1 and the fixed platform 7.

[0032] As shown in the figures, Figure 1 and Figure 2 the first PPPS branch 2 and the second PPPS branch 6 are respectively arranged at the two acute-angle vertices of the moving platform 1 and the fixed platform 7, and the first PPPS branch 2 and the second PPPS branch 6 are structurally identical, both comprising a first slide rail 21, a second slide block 22, a second slide rail 23, a second slide block 24, a first moving pair 25 and a first spherical pair 26. The first slide rail 21 is fixedly arranged on the fixed platform 7, the first end of the second slide block 22 is movably connected with the first slide rail 21, the second slide rail 23 is arranged at the second end of the second slide block 22, the first end of the second slide block 24 is movably connected with the second slide rail 23, the second end of the second slide block 24 is connected with the first end of the first moving pair 25, and the second end of the first moving pair 25 is connected with the moving platform 1 through the first spherical pair 26.

[0033] As shown in Figure 2 , the first slide 21 in the first and second PPPS branch 2 and 6 is perpendicular to the second slide 23 in the corresponding branch respectively, and the first slide 21 in the first and second PPPS branch 2 and 6 is parallel to the straight side of the fixed platform 7 respectively, and the axis of the first moving pair 25 in the first and second PPPS branch 2 and 6 is perpendicular to the first and second slide 21 and 23 in the corresponding branch respectively.

[0034] As shown in Figure 1 and Figure 3 , the first and second CPS branch 3 and 5 are arranged on two straight sides in the moving platform 1 and the fixed platform 7 respectively, and the first and second CPS branch 3 and 5 are the same structure, and the first and second CPS branch 3 and 5 both include the third slide 31, the third slide block 32, the first rotating pair 33, the second moving pair 34 and the second spherical pair 35, the third slide 31 is fixedly arranged on the fixed platform 7, the first and second ends of the third slide block 32 are connected with the third slide 31 and the fixed part of the first rotating pair 33 respectively, and the third slide 31 and the third slide block 32 jointly constitute a cylindrical pair, the rotating part of the first rotating pair 33 is connected with the first end of the second moving pair 34, and the second end of the second moving pair 34 is connected with the moving platform 1 through the second spherical pair 35.

[0035] As shown in Figure 3 , the second moving pair 34 in the first and second CPS branch 3 and 5 is perpendicular to the third slide 31 in the corresponding branch respectively, and the third slide 31 in the first and second CPS branch 3 and 5 is parallel to the straight side of the fixed platform 7 respectively.

[0036] As shown in Figure 1 and Figure 4 , the PPRPU branch 4 is arranged at the right angle vertex in the moving platform 1 and the fixed platform 7, and the PPRPU branch 4 includes the fourth slide 41, the fourth slide block 42, the fifth slide 43, the rotating platform 44, the third moving pair 45 and the hooke joint 46, the fourth slide 41 is fixedly arranged on the fixed platform 7, and the first end of the fourth slide block 42 is connected with the fourth slide 41 moving pair, the second end of the fourth slide block 42 is connected with the fifth slide 43 moving pair, and the first end of the third moving pair 45 is connected with the fifth slide 43 through the rotating platform 44, and the second end of the third moving pair 45 is connected with the moving platform 1 through the hooke joint 46.

[0037] As shown in Figure 4As shown, the fourth slide rail 41 and the fifth slide rail 43 in the PPRPU branch chain 4 are perpendicular to each other, and the rotation direction of the rotating platform 44 is perpendicular to the fourth slide rail 41 and the fifth slide rail 43, the axis of the third moving pair 45 is in the same direction as the rotation direction of the rotating platform 44, and the first rotation axis in the Hooke's hinge 46 is parallel to the fourth slide rail 41, and the second rotation axis in the Hooke's hinge 46 is parallel to the fifth slide rail 43.

[0038] In a preferred embodiment, the first drive of the six-degree-of-freedom weakly coupled parallel mechanism is arranged at the first moving pair 25 in the first PPPS branch 2, the second drive is arranged at the second moving pair 34 in the first CPS branch 3, the third drive is arranged at the rotating platform 44 in the PPRPU branch 4, the fourth drive is arranged at the third moving pair 45 in the PPRPU branch 4, the fifth drive is arranged at the first moving pair 25 in the second PPPS branch 6, and the sixth drive is arranged at the second moving pair 34 in the second CPS branch 5.

[0039] The second aspect of the present invention provides a method for constructing a six-degree-of-freedom weakly coupled parallel mechanism, wherein the coupling of the parallel mechanism represents the degree of influence of a single input on the output motion of the moving platform. For a weakly coupled mechanism, a certain output degree of freedom of the moving platform is only related to part of the input. Figure 5 As shown, it includes the following steps:

[0040] S1. Determine the desired degrees of freedom of motion of the parallel mechanism.

[0041] S2. According to the expected motion degrees of freedom of the parallel mechanism, the expected motion degrees of freedom are divided according to the nature of the degrees of freedom, into planar degrees of freedom and spatial degrees of freedom, and the overall parallel structure is divided into planar sub-parallel mechanisms and spatial sub-parallel mechanisms.

[0042] S3. Based on the screw theory, the reciprocal product of the force spinor and the motion spinor is the instantaneous power generated by the force spinor on the motion spinor. According to the degrees of freedom and weak coupling requirements of the planar sub-parallel mechanism and the spatial sub-parallel mechanism, the conditions for the reciprocal product of the force transmission spiral matrix and the output motion spiral matrix of the planar sub-parallel mechanism and the spatial sub-parallel mechanism branch to be a triangular matrix are obtained. The force transmission spiral form of the motion branch of the planar sub-parallel mechanism and the spatial sub-parallel mechanism is obtained. The reciprocal product operation rule of the spiral matrix is ​​defined as: if A is an n×1 matrix and B is a 1×n matrix, then the n×n matrix C is called the reciprocal product of the matrices A and B, and its form can be expressed as follows:

[0043]

[0044] Where $ Tn represents the nth branch force transmission spiral, $ n Indicates the n-th branch output motion spiral.

[0045] S4, according to the decoupling branch only driving screw pair output motion work, namely the transmission force screw and driving screw reciprocity product is not zero, namely Ti · i1 ≠0, 0, determine the form of the driving screw in the branch of the planar sub-parallel mechanism and the spatial sub-parallel mechanism.

[0046] S5, according to the decoupling branch non-driving screw pair output motion does not work, namely the transmission force screw and non-driving screw reciprocity product is zero, namely Ti · in =0, determine the form of the non-driving screw in the branch of the planar sub-parallel mechanism and the spatial sub-parallel mechanism.

[0047] S6, the driving screw and non-driving screw obtained in step S4 and step S5 are arranged and combined to obtain each branch of the planar sub-parallel mechanism and the spatial sub-parallel mechanism with specific degrees of freedom and decoupling characteristics.

[0048] S7, the degrees of freedom of each branch in the planar sub-parallel mechanism and the spatial sub-parallel mechanism are supplemented to meet the overall mechanism motion degrees of freedom.

[0049] S8, the designed planar sub-parallel mechanism and the spatial sub-parallel mechanism are combined, and the position of the branch chain is arranged to obtain the desired multi-degree-of-freedom weakly coupled parallel mechanism.

[0050] S9, the degrees of freedom and decoupling characteristics of the designed parallel mechanism are calculated and verified, and the parallel mechanism construction work with weak coupling characteristics is completed.

[0051] The application researches the multi-degree-of-freedom weakly coupled parallel mechanism construction method, proposes a new multi-degree-of-freedom weakly coupled parallel mechanism synthesis method, splits the overall parallel mechanism into multiple sub-parallel mechanisms according to the motion characteristics of the degrees of freedom, and takes six degrees of freedom as an example. The synthesis process of the complex six-degree-of-freedom weakly coupled parallel mechanism is converted into the synthesis of a three-degree-of-freedom weakly coupled parallel mechanism, which is synthesized by two sub-parallel mechanisms, and a 2PPPS-2CPS-PPRPU six-degree-of-freedom weakly coupled parallel mechanism is obtained. It has bearing capacity and decoupling characteristics, has the characteristics of more compact structure, higher output precision and wider applicability.

[0052] The above-described embodiments are only preferred embodiments of the application, and do not limit the scope of the application. Without departing from the design spirit of the application, various modifications and improvements of the technical solutions of the application made by those skilled in the art shall fall within the protection scope of the claims of the application.

Claims

1. A six-degree-of-freedom weakly coupled parallel mechanism, characterized in that: It includes a moving platform, a fixed platform, and two PPPS branches, two CPS branches and one PPRPU branch located between the moving platform and the fixed platform. The movable platform and the fixed platform are both in the shape of a right triangle structure, and a first PPPS branch chain, a first CPS branch chain, a PPRPU branch chain, a second CPS branch chain and a second PPPS branch chain are provided between the movable platform and the fixed platform; The first PPPS branch chain and the second PPPS branch chain are respectively arranged at the vertices of two acute angles in the moving platform and the fixed platform, and the first PPPS branch chain and the second PPPS branch chain have the same structure. The first PPPS branch chain and the second PPPS branch chain both include a first slide rail, a second slider, a second slide rail, a second slider, a first moving pair and a first ball pair. The first slide rail is fixedly arranged on the fixed platform, and the first end of the second slider is connected to the first slide rail moving pair. The second end of the second slider is provided with the second slide rail, and the first end of the second slider is connected to the second slide rail moving pair. The second end of the second slider is connected to the first end of the first moving pair, and the second end of the first moving pair is connected to the moving platform through the first ball pair. The first CPS branch chain and the second CPS branch chain are respectively arranged on two right-angled sides of the moving platform and the fixed platform, and the first CPS branch chain and the second CPS branch chain have the same structure. The first CPS branch chain and the second CPS branch chain each include a third slide rail, a third slider, a first rotational pair, a second movable pair, and a second ball pair. The third slide rail is fixedly arranged on the fixed platform. The first end and the second end of the third slider are respectively connected to the third slide rail and the fixed part of the first rotational pair, and together with the third slide rail, they form a cylindrical pair. The rotating part of the first rotational pair is connected to the first end of the second movable pair, and the second end of the second movable pair is connected to the moving platform via the second ball pair. The PPRPU branch chain is arranged at the right-angle vertex between the moving platform and the fixed platform, and the PPRPU branch chain includes a fourth slide rail, a fourth slider, a fifth slide rail, a rotating platform, a third moving pair and a Hooke's hinge. The fourth slide rail is fixed on the fixed platform, and the first end of the fourth slider is connected to the fourth slide rail moving pair, the second end of the fourth slider is connected to the fifth slide rail moving pair, and the first end of the third moving pair is connected to the fifth slide rail through the rotating platform, and the second end of the third moving pair is connected to the moving platform through the Hooke's hinge.

2. The six-degree-of-freedom weakly coupled parallel mechanism according to claim 1, characterized in that: The first drive of the six-degree-of-freedom weakly coupled parallel mechanism is arranged at the first moving pair in the first PPPS branch, the second drive is arranged at the second moving pair in the first CPS branch, the third drive is arranged at the rotating platform in the PPRPU branch, the fourth drive is arranged at the third moving pair in the PPRPU branch, the fifth drive is arranged at the first moving pair in the second PPPS branch, and the sixth drive is arranged at the second moving pair in the second CPS branch.

3. The six-degree-of-freedom weakly coupled parallel mechanism according to claim 1, characterized in that: The first slide rails in the first PPPS branch and the second PPPS branch are respectively perpendicular to the second slide rails in the corresponding branch, and the first slide rails in the first PPPS branch and the second PPPS branch are respectively parallel to the right-angled sides of the fixed platform, and the axes of the first moving pairs in the first PPPS branch and the second PPPS branch are respectively perpendicular to the first slide rail and the second slide rail in the corresponding branch.

4. The six-degree-of-freedom weakly coupled parallel mechanism according to claim 3, characterized in that: The second moving pairs in the first and second CPS branches are respectively perpendicular to the third slide rails in the corresponding branches, and the third slide rails in the first and second CPS branches are respectively parallel to the right-angled sides of the fixed platform.

5. The six-degree-of-freedom weakly coupled parallel mechanism according to claim 4, characterized in that: The fourth slide rail and the fifth slide rail in the PPRPU branch chain are perpendicular to each other, and the rotation direction of the rotating platform is perpendicular to the fourth slide rail and the fifth slide rail. The axis of the third moving pair is in the same direction as the rotation direction of the rotating platform, and the first rotation axis in the Hooke's hinge is parallel to the fourth slide rail, and the second rotation axis in the Hooke's hinge is parallel to the fifth slide rail.

6. A method for constructing a six-degree-of-freedom weakly coupled parallel mechanism according to any one of claims 1 to 5, characterized in that: It includes the following steps: S1. Determine the desired degrees of freedom of motion of the parallel mechanism; S2. Based on the expected motion degrees of freedom of the parallel mechanism, the expected motion degrees of freedom are divided into planar degrees of freedom and spatial degrees of freedom according to their properties, and the overall parallel structure is divided into planar sub-parallel mechanisms and spatial sub-parallel mechanisms; S3. Based on the screw theory, the reciprocal product of the force spinor and the motion spinor is the instantaneous power generated by the force spinor on the motion spinor. According to the degrees of freedom and weak coupling requirements of the planar sub-parallel mechanism and the spatial sub-parallel mechanism, the conditions for the reciprocal product of the force transmission spiral matrix and the output motion spiral matrix of the planar sub-parallel mechanism and the spatial sub-parallel mechanism to be a triangular matrix are obtained. The transmission force spiral form of the motion branch of the planar sub-parallel mechanism and the spatial sub-parallel mechanism is calculated. S4. Based on the fact that only the driving screw in the decoupling branch does work on the output motion, i.e., the reciprocal product between the force transmission screw and the driving screw is not zero, determine the form of the driving screw in the planar sub-parallel mechanism and the spatial sub-parallel mechanism branches; S5. Based on the fact that the non-driven spiral in the decoupling branch does no work on the output motion, i.e., the reciprocal product between the force-transmitting spiral and the non-driven spiral is always zero, determine the form of the non-driven spiral in the planar sub-parallel mechanism and the spatial sub-parallel mechanism branches; S6. Arrange and combine the driving spirals and the non-driving spirals obtained in step S4 and step S5 to obtain branches of the planar sub-parallel mechanism and the spatial sub-parallel mechanism with specific degrees of freedom and decoupling characteristics; S7. Supplement the degrees of freedom of each branch in the planar sub-parallel mechanism and the spatial sub-parallel mechanism to satisfy the motion degrees of freedom of the overall mechanism; S8. Combine the designed planar sub-parallel mechanism with the spatial sub-parallel mechanism and arrange the positions of the branches to obtain the desired multi-degree-of-freedom weak-coupling parallel mechanism; S9. Calculate and verify the degrees of freedom and decoupling characteristics of the designed parallel mechanism, and complete the construction of the parallel mechanism with weak coupling characteristics.

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