Configuration method of heavy-load force-motion coupling parallel mechanism

Abstract

The present invention relates to a configuration method for a heavy-load force-motion coupling parallel mechanism, comprising the following steps: S1, based on the screw theory and the force balance condition of the parallel mechanism, determining the optimal load-bearing criterion of the branch of the parallel mechanism: the driving force provided by the branch is consistent with the direction of the externally applied load; S2, based on the force-increasing effect at the extreme position of the connecting rod mechanism, determining the minimum drive load criterion of the parallel mechanism: the driving force provided by the driving joint is orthogonal to the direction of the driving force provided by the branch; S3, combining the optimal load-bearing criterion of the branch with the minimum drive load criterion, determining the optimal force-bearing criterion of the parallel mechanism; S4, coupling the optimal force-bearing criterion of the parallel mechanism with the motion constraint screw, and deriving and proposing a heavy-load force-motion coupling synthesis process; S5, performing branch synthesis and structural synthesis on the parallel mechanism containing spatial rotational motion. The present invention provides a new method for the synthesis of heavy-load parallel mechanisms, which further improves the application prospects of parallel mechanisms under heavy-load conditions.

Description

Technical Field

[0001] The present invention relates to the field of parallel mechanism configuration synthesis, and more particularly to a configuration method of a heavy-load force-motion coupling parallel mechanism. Background Art

[0002] The multi-chain closed-loop structure of parallel mechanisms offers advantages such as strong load-bearing capacity, high rigidity, and high precision, making them widely used in handling, packaging, and forming. The configurational synthesis of parallel mechanisms, which includes type synthesis and scale synthesis, is the foundation for the research and development of parallel mechanisms to meet motion requirements, achieve performance needs, and enhance dynamic performance. Currently, a variety of configurational synthesis methods have been proposed by scholars: in terms of type synthesis, these mainly include methods based on spinor theory, displacement group theory, virtual loop method, and POC set method; in terms of scale synthesis, they mainly include performance maps and parameter optimization methods based on objective functions. However, the current design of parallel mechanisms generally begins with type synthesis based on motion patterns, followed by parameter optimization based on performance requirements. In other words, the type synthesis and scale synthesis of parallel mechanisms are performed separately. This separation makes it difficult to determine the parallel mechanism's performance, such as its load-bearing capacity, during the type synthesis stage, making it difficult to achieve simultaneous optimization of the mechanism's configuration and scale, thus limiting the performance improvement of existing parallel mechanisms. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a configuration method of a heavy-load force-motion coupling parallel mechanism, which can improve the performance of the parallel mechanism.

[0004] The technical solution adopted by the present invention to solve the technical problem is: constructing a heavy-load force-motion coupling parallel mechanism configuration method, including the following steps:

[0005] S1. Based on the screw theory and the force balance condition of the parallel mechanism, the optimal load-bearing criterion of the branch chain of the parallel mechanism is determined: the driving force provided by the branch chain is consistent with the direction of the externally applied load;

[0006] S2. Based on the force-increasing effect of the linkage at its extreme position, the minimum driving load criterion for the parallel mechanism is determined: the driving force provided by the driving joint is orthogonal to the driving force provided by the branch chain;

[0007] S3. Determine the optimal force bearing criterion of the parallel mechanism by combining the optimal bearing criterion of the branch chain and the minimum driving load criterion;

[0008] S4, coupled with the optimal force bearing criterion and motion constraint screw of the parallel mechanism, a heavy load force-motion coupling synthesis process is derived and proposed;

[0009] S5. Branch synthesis and structural synthesis were performed on the parallel mechanism involving spatial rotational motion.

[0010] In the above scheme, in step S1, the motion / force of the parallel mechanism dynamic platform is represented as the intersection of the motions of each branch.

[0011]

[0012] Where, ξ ij represents the instantaneous velocity amplitude of the j-th kinematic joint on the i-th limb, m S ij represents the instantaneous motion spin of the j-th kinematic pair on the i-th limb, express m S ij The unit spinor of f S ri is the instantaneous force screw of the i-th branch, is the instantaneous reciprocal rotation of the kth joint of the i-th branch acting on the mobile platform, and They are f S ri and The unit spinor, f i Force screw f S ri The amplitude, f ik is the instantaneous reciprocal spinor The amplitude of the moving platform is expressed as the reciprocal product of its kinetic spin and force spin:

[0013]

[0014] In the formula, the force torque f S ri Provided by the branch actuator, it is directly used to offset the resistance / resistance torque that hinders the motion of the parallel mechanism, which is solved according to the following formula;

[0015]

[0016] Force torque is the constraint reaction force generated by the branch's geometric constraints, the force twister The power provided to the motion platform is zero; Equation (3) can be rewritten as,

[0017]

[0018] The optimal load-bearing criterion for determining the branch chain of the parallel mechanism is:

[0019]

[0020] In the above solution, in step S2, when the branch driven by the rotary joint is at the extreme position, the force rotation f S riThe kinematic rotation of the driven joint m S i1 Coplanar in space; when the branch driven by the mobile joint is in the extreme position, the force torque f S ri The kinematic rotation of the driven joint m S i1 Coplanar and orthogonal, the extreme positions of the branches are defined as:

[0021]

[0022] In the above solution, in step S3, the optimal load-bearing condition of the branch under heavy load conditions satisfies the following formula:

[0023]

[0024] In the above scheme, in step S4, the generalized motion subspace of the parallel mechanism is n S is expressed by the moving platform motion screw system:

[0025]

[0026] Where, (S1, S2, ..., S n ) represents a set of linearly independent unit spinors, n S represents an n-order spinor system, which is related to a set of linearly independent spinors (S1, S2, ..., S n ) is the set of all the spinors that are linearly related to each other. The superscript “n” represents the degree of freedom of the parallel mechanism motion platform. The constrained spinor system of the motion platform is expressed as:

[0027]

[0028] Based on the set union operation satisfied by the parallel mechanism branch constraint screw system and the moving platform constraint screw system: The branched constrained spinor system is expressed as:

[0029]

[0030] Substituting the optimal load-bearing condition into the branch's constrained screw system, the branch's constrained screw system that satisfies the optimal load-bearing condition can be rewritten as:

[0031]

[0032]

[0033] The branched kinematic screw system is solved according to the following equation:

[0034]

[0035] On this basis, various types of parallel mechanism branches with optimal load-bearing conditions are generated through the linear combination of branch motion rotation quantities, and a parallel mechanism that meets the motion requirements and has excellent load-bearing performance is obtained.

[0036] In the above solution, in step S5, it is assumed that the generalized force applied to the moving platform is expressed as: f S p =(s w ; r w ×s w ),r w =(l1 m1 n1) T , then the force screw is expressed as:

[0037]

[0038] According to formula (19), the corresponding branch motion spinor system is expressed as:

[0039]

[0040] Where a i 、b i and c i represents the proportionality coefficient, satisfying |a i |+|b i |≠0, and c i ≠0, ⊥ s w Indicates orthogonality to s w vector; further, according to formula (21), the specific branch motion spinor system corresponding to the specific external force spinor is derived, assuming that, f S ri =(z; r e ×z),r e =[l e m e n e ] T ;

[0041]

[0042] The branches that meet the motion requirements can be obtained by linearly combining the branch motion spinors in equation (22).

[0043] The above solution also includes step S6, which uses a scale synthesis method based on the task space to solve the problem of the integrated parallel mechanism being located at a singular position.

[0044] In the above scheme, in step S6, the parallel mechanism is scaled to avoid singularities and establish the relationship between the motion space and the load-bearing capacity near singularities; the relationship between input and output is obtained using the vector closure method. Therefore, it is reasonable to assume that the input-output relationship of the parallel mechanism is:

[0045]

[0046] Where, Indicates the input speed of each branch driving joint, Indicates the output speed of the dynamic platform; under heavy load conditions, the rotation m S ij，j≠1 and spinor f S ri If it is an intersection relationship, the branch structure parameters satisfy the following constraints:

[0047]

[0048] Where, represents the end point of branch i, a ij Represents the position vector of the jth joint in branch i; combined with the structural parameter constraints, input-output relationship and workspace, some initial parameters of the branch are calculated.

[0049] The configuration method of the heavy-load force-motion coupling parallel mechanism of the present invention has the following beneficial effects:

[0050] 1. This invention proposes a new heavy-load force-motion coupling synthesis method by coupling the optimal force-bearing criterion and motion constraints of a parallel mechanism. The resulting parallel mechanism has excellent load-bearing performance.

[0051] 2. The 6-PHSS parallel mechanism designed by the present invention achieves a high payload output-input ratio exceeding 25. Compared with the Stewart platform (6-UPS parallel mechanism) designed using traditional methods, the maximum forces of the actuator and connecting rod are significantly reduced, by 80% and 10%, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0053] Figure 1 It is a schematic diagram of the branch configuration of the 3R3T parallel mechanism with the optimal load-bearing criterion;

[0054] Figure 2 It is a schematic diagram of the branch configuration of the 3R parallel mechanism with the optimal load-bearing criterion;

[0055] Figure 3It is a schematic diagram of the branch configuration of the 3R1T parallel mechanism with the optimal load-bearing criterion;

[0056] Figure 4 It is a schematic diagram of the branch configuration of the 3R2T parallel mechanism with the optimal load-bearing criterion;

[0057] Figure 5 It is a basic structural diagram of the 6-PHSS parallel mechanism;

[0058] Figure 6 It is the force diagram of the connecting rod of the 6-PHSS parallel mechanism;

[0059] Figure 7 This is the force diagram of the 6-PH SS parallel mechanism actuator;

[0060] Figure 8 This is a schematic diagram of the connecting rod forces of the 6-UPS parallel mechanism. DETAILED DESCRIPTION

[0061] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0062] like Figure 1 As shown, the configuration method of the heavy-load force-motion coupling parallel mechanism of the present invention includes:

[0063] S1. Based on the screw theory and the force balance condition of the parallel mechanism, the optimal load-bearing criterion of the branch chain of the parallel mechanism is derived and defined: the driving force provided by the branch chain is consistent with the direction of the external load. The motion / force of the parallel mechanism dynamic platform can be expressed as the intersection of the motion of each branch chain.

[0064]

[0065] Where, ξ ij represents the instantaneous velocity amplitude of the j-th kinematic joint on the i-th limb, m S ij represents the instantaneous motion spin of the j-th kinematic pair on the i-th limb, express m S ij The unit spinor of f S ri is the instantaneous force screw of the i-th branch, is the instantaneous reciprocal rotation of the kth joint of the i-th branch acting on the mobile platform, and They are f S ri and The unit spinor, f i Force screw f S riThe amplitude, f ik is the instantaneous reciprocal spinor The instantaneous power of the moving platform can be expressed by the reciprocal product of its kinetic spin and force spin,

[0066]

[0067] In the formula, the force torque f S ri Provided by the branch actuator, it is directly used to offset the resistance / resistance torque that hinders the motion of the parallel mechanism. It can be solved according to the following formula (assuming that the first joint is the driving joint of the limb),

[0068]

[0069] Force torque It is the constraint reaction force generated by the geometric constraint of the branch, which flows through the joints and links in the branch to the base without hindering the movement of the mechanism. The power provided to the motion platform is zero. Equation (3) can be rewritten as,

[0070]

[0071] From formula (5), we can see that under the same structure and size, the torque f S ri The closer the direction is to the direction of the external force, the greater the load-bearing capacity of the parallel mechanism. This condition is defined as the optimal load-bearing criterion of the branch chain of the parallel mechanism and can be expressed as follows:

[0072]

[0073] S2. Based on the force-amplifying effect at the extreme position of the connecting rod mechanism, the minimum load criterion for driving the parallel mechanism is derived and defined: the driving force provided by the driving joint is orthogonal to the driving force provided by the branch chain. Similar to the geometric characteristics of the connecting rod mechanism, the extreme position of the parallel mechanism can also be determined by a similar force-amplifying effect. The limbs of the parallel mechanism are usually driven by a rotary joint (representing full-circle rotation) or a mobile joint (representing alternating motion). Within one rotation cycle of the actuator joint, the branch driven by the rotary joint has two extreme positions, while the branch driven by the mobile joint has one extreme position. This feature is independent of the direction of the branch and the position of the driving joint on the branch. When the branch driven by the rotary joint is in the extreme position, the force rotation f S ri The kinematic rotation of the driven joint m S i1 Coplanar in space; when the branch driven by the mobile joint is in the extreme position, the force torque f S ri The kinematic rotation of the driven jointm S i1 are coplanar and orthogonal. Therefore, the extreme positions of the branches can be defined as,

[0074]

[0075] S3. Combining the branch chain's optimal load-bearing criterion with the minimum drive load criterion, the optimal force load-bearing criterion for the parallel mechanism is proposed. Combining formulas (5) and (7), the optimal load-bearing condition of the branch under heavy load conditions satisfies the following formula:

[0076]

[0077] Therefore, when the motion mode and external force of the parallel mechanism are known, the limb motion screw system can be reconstructed according to the optimal load-bearing condition of formula (8).

[0078] S4. The optimal force bearing criterion and motion constraint screw of the coupled parallel mechanism are derived and proposed. The generalized motion subspace of the parallel mechanism n S can be expressed by a moving platform motion screw system,

[0079]

[0080] Where, (S1, S2, ..., S n ) represents a set of linearly independent unit spinors, n S represents an n-order spinor system, which is related to a set of linearly independent spinors (S1, S2, ..., S n ) is the set of all spinors linearly related to each other, and the superscript “n” represents the degree of freedom of the parallel mechanism motion platform. Therefore, the constrained spinor system of the motion platform can be expressed as,

[0081]

[0082] Based on the set union operation satisfied by the parallel mechanism branch constraint screw system and the moving platform constraint screw system: The branched constrained spinor system can be expressed as,

[0083]

[0084] Furthermore, by substituting the optimal load-bearing condition (Equation (8)) into the branch's constrained spinor system, the branch's constrained spinor system that satisfies the optimal load-bearing condition can be rewritten as:

[0085]

[0086] The branched kinematic spinor system can be solved according to the following formula:

[0087]

[0088] On this basis, various parallel mechanism branches with optimal load-bearing conditions can be generated through the linear combination of branch motion rotations. Through reasonable assembly and transmission design, a parallel mechanism that meets motion requirements and has excellent load-bearing performance can be obtained.

[0089] S5. Based on the proposed method, branch synthesis and structural synthesis are performed on the parallel mechanism involving spatial rotation motion, including 3R, 3R1T, 3R2T and 3R3T motion modes. According to step S4, it is assumed that the generalized force applied to the moving platform is expressed as: f S p =(s w ; r w ×s w ),r w =(l1 m1 n1) T , then the force torque can be expressed as:

[0090]

[0091] According to formula (19), the corresponding branch motion spinor system can be expressed as,

[0092]

[0093] Where a i 、b i and c i represents the proportionality coefficient, satisfying |a i |+|b i |≠0, and c i ≠0, ⊥ s w Indicates orthogonality to s w Furthermore, according to formula (21), the specific branch motion spinor system corresponding to the specific external force spinor can be derived, assuming that f S ri =(z; r e ×z),r e =[l e m e n e ] T ,

[0094]

[0095] The branches that meet the motion requirements can be obtained by linearly combining the branch motion spinors in Equation (22). Table 1 summarizes all the branches of the 3R3T parallel mechanism without considering the order of arrangement. Tables 2, 3, and 4 are the branches of 3R, 3R1T, and 3R2T respectively.

[0096] The subscript "O" in the table indicates that the joint axes intersect at a certain point, the subscript "E" indicates that the joint axes are in the same plane, the subscript "H" indicates that the direction of the moving joint is parallel to the fixed platform, the subscript "U" indicates that two consecutive R joints intersect at a certain point, and these two joints can be replaced by U joints, and the subscript "S" indicates that the axes of three R joints intersect at the same point, and these three joints can be replaced by S joints.

[0097] Table 1 Branch types of 3R3T motion mode parallel mechanism

[0098]

[0099] Table 2 Branch types of 3R motion mode parallel mechanism

[0100]

[0101]

[0102] Table 3 Branch types of 3R1T motion mode parallel mechanism

[0103]

[0104] Table 4 Branch types of 3R2T motion mode parallel mechanism

[0105]

[0106] Table 5 Parallel mechanism types

[0107]

[0108] In addition, the branching configurations shown in Tables 1 to 4 are respectively Figures 1 to 4 The branch arrangement shown corresponds to the one shown in the figure. Although there are many limbs with optimal load-bearing conditions that can be used to form 3R, 3R1T, 3R2T and full-degree-of-freedom parallel mechanisms, limbs containing more than three joints will affect the stiffness and stability of the parallel mechanism. Based on the above design considerations and the branch configuration under the optimal load-bearing conditions shown in Tables 1 to 4, a parallel mechanism can be generated by taking n identical branches (where n is the degree of freedom of the motion platform). Among them, (RR) in the limb U and (RRR) S The U and S joints can be used to replace them respectively, and the limbs with undriven P joints are not considered. By selecting the effective actuator input, the comprehensive results of the corresponding parallel mechanism are shown in Table 5 ( R / P represents active joint).

[0109] S6. Aiming at the problem that the synthesized parallel mechanism is located in a singular position, a scale synthesis method based on the task space is proposed. In the type synthesis based on the motion mode, the Jacobian matrix of the branch must be full rank, and the type synthesis result based on the motion mode cannot be singular. Since the optimal load-bearing condition is attached in the type synthesis, the Jacobian matrix of the branch will not be full rank, so the type synthesis result of the parallel mechanism must be singular. To this end, the parallel mechanism is scaled to avoid singularities and establish the relationship between the motion space and the load-bearing capacity under near-singularities. Dimensional synthesis depends on the inverse solution of the parallel mechanism. Although the inverse solution operations of various parallel mechanisms are different, the relationship between the input and output can be obtained using the vector closure method. Therefore, it is reasonable to assume that the input-output relationship of the parallel mechanism is:

[0110]

[0111] Where, Indicates the input speed of each branch driving joint, Indicates the output speed of the dynamic platform. According to the optimal load-bearing conditions, since the non-driven mobile joints are usually not considered, the rotation m S ij，j≠1 The rotation of can be considered as zero. In this case, according to the reciprocal geometry of the screw, the spinor f S ri and m S ij，j≠1 In addition, the maximum stiffness direction of the structural members (passive joints and links) within a branch should be as close as possible to the axis of the branch. f S ri The direction of the twist is consistent. This usually means that the structural components are located in the same straight line, because the direction of maximum stiffness of the connecting rod is usually axial. Therefore, under heavy load conditions, the twist m S ij，j≠1 and spinor f S ri If it is an intersection relationship, the branch structure parameters satisfy the following constraints:

[0112]

[0113] Where, represents the end point of branch i, a ij Represents the position vector of the jth joint in branch i. Combining the structural parameter constraints (Formula (24)), the input-output relationship (Formula (23)) and the workspace, some initial parameters of the branch can be calculated. It should be noted that the branch with the above parameters is in a singular position (boundary singularity, structural singularity, or both). In order to avoid the boundary singularity of the parallel mechanism, it is necessary to expand the given workspace. In order to avoid the structural singularity of the parallel mechanism, the initial distribution angle of the joint can be designed.

[0114] According to the configuration steps of the above-mentioned heavy-load force-motion coupling parallel mechanism configuration method, a nearly singular 6-P H The SS parallel mechanism realizes the fixed-point swing motion and carries out parameter design and load-bearing performance evaluation. The fixed-point swing motion can be expressed as:

[0115]

[0116] In this embodiment, θ=1.5π / 180, φ=2πt, t represents time. The load during the fixed-point swing motion can be expressed as,

[0117]

[0118] 6-P H The design parameters of the SS parallel mechanism are shown in Table 6. The basic structure is as follows: Figure 5 shown.

[0119] Table 6 6-P H SS PKM structural parameters

[0120] External force f (kN) 6000 External force application point [200cos(2πt),200sin(2πt),0] Theoretical swing angle of moving platform θ(deg) 1.5 <![CDATA[Moving platform design swing angle θ d (deg)]]> 1.5+0.05 <![CDATA[Moving platform height h m (mm)]]> 530 <![CDATA[Upper ball joint distribution angle β1 (deg)]]> [10,56,130,176,250,296] <![CDATA[Upper ball joint distribution radius r b (mm)]]> 470 Lower ball joint deflection angle Δβ (deg) 10 <![CDATA[Lower ball joint distribution angle α i (deg)]]> {0,66,120,186,240,306} <![CDATA[Link length l i (mm)]]> 450.30 <![CDATA[Lower ball joint distribution angle r a (mm)]]> 568.72

[0121] According to the design parameters, 6-P H The branch force and driver force of the SS parallel mechanism during movement are analyzed and calculated. Figure 6 As shown, the driver is subjected to the force Figure 7 As shown in Figure 6, the maximum forces of the connecting rod and the actuator are approximately 1610 kN and 220 kN, respectively, and the force input-output ratio exceeds 25. In addition, a traditional Stewart platform (6-UPS) with the same size as Table 6 was established to further verify the proposed force-motion coupling mechanism synthesis method. For the 6-UPS parallel mechanism, the force of the actuator in the branch is equal to the connecting rod force generated by the motion direction of the P joint passing through the center of the U pair and the S pair. The instantaneous force on the branch of the 6-UPS parallel mechanism designed with optimized parameters during motion is as follows: Figure 8 As shown, the maximum force of the branch and actuator is about 1810kN. In comparison, the 6-P H The SS has an 80% reduction in actuator force and a 10% reduction in maximum link force.

[0122] This paper proposes a configuration method for a heavy-load force-motion coupled parallel mechanism. It derives an optimal load-bearing criterion for the parallel mechanism. Based on the coupled load-bearing criterion and kinematic constraints, a new synthesis method for heavy-load force-motion coupled parallel mechanisms is proposed. Branch and structural synthesis are performed for parallel mechanisms involving spatial rotational motion, including 3R, 3R1T, 3R2T, and 3R3T motion modes. To address the problem of synthesized parallel mechanisms located in singular positions, a task-space-based scaling synthesis method is proposed. Performance is verified using a synthesized near-singular 6-PHSS parallel mechanism as an example. Compared with a Stewart platform (6-UPS parallel mechanism) designed using traditional methods, the maximum forces of the actuators and limbs are reduced by 80% and 10%, respectively, validating the effectiveness of the proposed synthesis method for heavy-load force-motion coupled parallel mechanisms. This paper provides a new approach for the synthesis of heavy-load parallel mechanisms, further enhancing the application prospects of parallel mechanisms under heavy-load conditions.

[0123] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A method for configuring a heavy-load force-motion coupling parallel mechanism, characterized in that: The following steps are involved: S1. Based on the screw theory and the force balance condition of the parallel mechanism, the optimal load-bearing criterion of the branch chain of the parallel mechanism is determined: the driving force provided by the branch chain is consistent with the direction of the externally applied load; S2. Based on the force-increasing effect of the linkage at its extreme position, the minimum driving load criterion for the parallel mechanism is determined: the driving force provided by the driving joint is orthogonal to the driving force provided by the branch chain; S3. Determine the optimal force bearing criterion of the parallel mechanism by combining the optimal bearing criterion of the branch chain and the minimum driving load criterion; S4. Couple the optimal force bearing criterion and motion constraint screw of the parallel mechanism, and derive and propose a comprehensive process of heavy-load force-motion coupling; S5. Perform branch synthesis and structural synthesis on the parallel mechanism involving spatial rotational motion.

2. The configuration method of the heavy-load force-motion coupling parallel mechanism according to claim 1, characterized in that: In step S1, the motion / force of the parallel mechanism platform is represented as the intersection of the motions of each branch. (1) (2) Where, Indicates the i The first limb j The instantaneous velocity amplitude of each moving joint, Indicates the i The first limb j The instantaneous motion spin of the kinematic pair, express The unit spinor of For the i The instantaneous force spin of each branch, For the first i The first branch k The instantaneous reciprocal rotation of the joints, and They are and The unit spin of Force screw The amplitude of is the instantaneous reciprocal spinor The amplitude of the moving platform is expressed as the reciprocal product of its kinetic spin and force spin: (3) In the formula, the force torque Provided by the branch actuator, it is directly used to offset the resistance / resistance torque that hinders the motion of the parallel mechanism, which is solved according to the following formula; (4) Force torque is the constraint reaction force generated by the branch's geometric constraints, the force twister The power provided to the motion platform is zero; Equation (3) can be rewritten as, (5) The optimal load-bearing criterion for determining the branch chain of the parallel mechanism is: (6)。 3. The configuration method of the heavy-load force-motion coupling parallel mechanism according to claim 2, characterized in that: In step S2, when the branch driven by the revolute joint is at the limit position, the force rotation The kinematic rotation of the driven joint Coplanar in space; when the branch driven by the mobile joint is in the extreme position, the force torque The kinematic rotation of the driven joint Coplanar and orthogonal, the extreme positions of the branches are defined as: (7)。 4. The configuration method of the heavy-load force-motion coupling parallel mechanism according to claim 3, characterized in that: In step S3, the optimal load-bearing condition of the branch under heavy load conditions satisfies the following formula: (8)。 5. The configuration method of the heavy-load force-motion coupling parallel mechanism according to claim 4, characterized in that: In step S4, the generalized motion subspace of the parallel mechanism It can be expressed by the moving platform motion screw system: (9) Where, ( S 1, S 2,……, S n ) represents a set of linearly independent unit spinors, represents an n-order spinor system, which is related to a set of linearly independent spinors ( S 1, S 2,……, S n ) is the set of all the spinors that are linearly related to each other. The superscript "n" represents the degree of freedom of the parallel mechanism motion platform. The constrained spinor system of the motion platform is expressed as: (10) Based on the set union operation satisfied by the parallel mechanism branch constraint screw system and the moving platform constraint screw system: , the branched constrained spinor system is expressed as: (11) (12) (13) (14) Substituting the optimal load-bearing condition into the branch's constrained screw system, the branch's constrained screw system that satisfies the optimal load-bearing condition can be rewritten as: (15) (16) (17) (18) The branched kinematic screw system is solved according to the following equation: (19) On this basis, various types of parallel mechanism branches with optimal load-bearing conditions are generated through the linear combination of branch motion rotation quantities, and a parallel mechanism that meets the motion requirements and has excellent load-bearing performance is obtained.

6. The configuration method of the heavy-load force-motion coupling parallel mechanism according to claim 5, characterized in that: In step S5, it is assumed that the generalized force applied to the moving platform is expressed as: , then the force screw is expressed as: (20) According to formula (19), the corresponding branch motion spinor system is expressed as: (21) Where a i 、b i and c i represents the proportionality coefficient, satisfying |a i |+|b i |≠0, and c i ≠0, Indicates orthogonality to vector; further, according to formula (21), the specific branch motion spinor system corresponding to the specific external force spinor is derived, assuming that, ; (22) The branches that meet the motion requirements can be obtained by linearly combining the branch motion spinors in equation (22).

7. The method for configuring a heavy-load force-motion coupling parallel mechanism according to claim 6, characterized in that: The method further includes step S6, which uses a scale synthesis method based on the task space to solve the problem of the integrated parallel mechanism being located at a singular position.

8. The configuration method of the heavy-load force-motion coupling parallel mechanism according to claim 7, characterized in that: In step S6, the parallel mechanism is scaled to avoid singularities and establish the relationship between the motion space and the carrying capacity near singularities. The vector closure method is used to obtain the relationship between input and output. Therefore, it is reasonable to assume that the input-output relationship of the parallel mechanism is: (23) Where, Indicates the input speed of each branch driving joint, Indicates the output speed of the dynamic platform; under heavy load conditions, the rotation and spinor If it is an intersection relationship, the branch structure parameters satisfy the following constraints: (24) Where, Indicates branch i The end point, Indicates the first j The position vectors of the joints are calculated by combining the structural parameter constraints, input-output relationship and workspace to calculate some initial parameters of the branch.

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