Single-power-source heavy-duty multi-degree-of-freedom forming device configuration design method

Abstract

This invention relates to a configuration design method for a single-power-source heavy-duty multi-degree-of-freedom forming device, comprising the following steps: S1, deriving the design constraints of the single-power-source heavy-duty multi-degree-of-freedom forming device; S2, establishing the branch constraint screw system and motion screw system of the single-power-source heavy-duty multi-degree-of-freedom forming device; S3, synthesizing the motion branches that satisfy the design constraints and motion requirements of the single-power-source heavy-duty multi-degree-of-freedom forming device; S4, synthesizing all fully symmetrical configurations of the single-power-source heavy-duty multi-degree-of-freedom forming device; S5, establishing a global velocity Jacobian matrix, and optimizing variable structural parameters based on minimizing global motion errors; S6, finally obtaining the configuration and parameters of the single-power-source heavy-duty multi-degree-of-freedom forming device that satisfy a specific motion trajectory. This invention can realize the configuration synthesis and dimensional synthesis of the single-power-source heavy-duty multi-degree-of-freedom forming device, ensuring low control, low cost, and high speed of the device while achieving specific motion requirements.

Description

Technical Field

[0001] This invention relates to the field of heavy-duty multi-degree-of-freedom forming device configuration design, and more specifically, to a method for designing a single-power-source heavy-duty multi-degree-of-freedom forming device configuration. Background Technology

[0002] Compared to serial mechanisms, parallel mechanisms, with their multi-chain closed-loop structure, offer advantages such as high load-bearing capacity, high stiffness, and high precision, making them particularly suitable for the execution systems of heavy-duty forming devices. The primary task in developing heavy-duty forming devices is designing configurations that meet the requirements of motion degrees of freedom / trajectory, i.e., parallel mechanism configuration synthesis. Currently, various synthesis methods have been proposed by scholars, mainly including those based on spinor theory, displacement group theory, virtual loop method, and POC set method. Parallel mechanisms synthesized using these methods typically employ multiple actuators to achieve precise and arbitrary spatial motion, leading to complex mechanical and control systems and high costs. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a configuration design method for a single-power-source heavy-duty multi-degree-of-freedom forming device. This method can realize the configuration integration and dimensional integration of the single-power-source heavy-duty multi-degree-of-freedom forming device, and ensure low control, low cost and high speed of the device while realizing specific motion requirements.

[0004] The technical solution adopted by this invention to solve its technical problem is: to construct a configuration design method for a single-power-source heavy-duty multi-degree-of-freedom forming device, including the following steps:

[0005] S1. Based on the specific spatial motion trajectory, determine the motion degree of freedom requirements of the motion platform of the single power source heavy-duty multi-degree-of-freedom forming device, construct a generalized mapping model between the motion platform and the actuator, and derive the design constraints of the single power source heavy-duty multi-degree-of-freedom forming device.

[0006] S2. Based on the reciprocal relationship between the degree of freedom requirements and screw system of the moving platform of the single-power-source heavy-duty multi-degree-of-freedom forming device, establish the mechanism motion screw system and constraint screw system. On this basis, establish the branch constraint screw system and motion screw system of the single-power-source heavy-duty multi-degree-of-freedom forming device.

[0007] S3. Combining the design constraints of the single-power-source heavy-duty multi-degree-of-freedom forming device and the branch motion screw system, linearly combine the motion screws in the motion screw system to synthesize the motion branch that meets the design constraints and motion requirements of the single-power-source heavy-duty multi-degree-of-freedom forming device.

[0008] S4, arbitrarily select branches of equal number of degrees of freedom to assemble, and synthesize the configuration of a fully symmetrical single-power-source heavy-duty multi-degree-of-freedom forming device.

[0009] S5. Establish the global velocity Jacobian matrix of a single-power-source heavy-load multi-degree-of-freedom forming device under a specific configuration, and optimize the variable structural parameters based on minimizing the global motion error.

[0010] S6. Finally, the configuration and parameters of the single-power-source heavy-duty multi-degree-of-freedom forming device that satisfies a specific motion trajectory are obtained.

[0011] According to the above scheme, in step S1, arbitrary spatial motion is characterized by a kinetic spinor, as shown in the following formula:

[0012]

[0013] In the formula, S mp S represents a system of kinetic spinors for specific spatial motion. mpi The screw represents the spinor of spatial motion; the rank of the screw system for a specific spatial motion is the degree of freedom of the required device; based on the mapping relationship between the mechanism's motion platform and the driving joints, the motion constraints of the single-power-source heavy-duty multi-degree-of-freedom forming device are determined; based on screw theory, the motion relationship between the mechanism's motion platform and the branch joints is expressed as:

[0014]

[0015] In the formula, S p This represents the kinetic spinor of the motion platform. ξ represents the unit rotational spin of the j-th joint in the i-th branch. ij This represents the instantaneous velocity amplitude of the j-th joint in the i-th branch;

[0016] The relationship between the motion of the motion platform and the velocity of the driving joint is as follows:

[0017]

[0018] In the formula, Represents the spindle force of the i-th branch of the mechanism;

[0019] The relationship between the output speed of the motion platform of a single-power-source heavy-duty multi-degree-of-freedom forming device and the input speed of the actuator is defined as follows:

[0020]

[0021] According to formula (4), the design constraints of the single power source heavy-duty multi-degree-of-freedom forming device are determined.

[0022] According to the above scheme, the design constraints of the single-power-source heavy-duty multi-degree-of-freedom forming device include:

[0023] (1) The branches of a single-power-source heavy-duty multi-degree-of-freedom forming device must be coupled;

[0024] (2) The driving joint of the single power source heavy-duty multi-degree-of-freedom forming device is a driving moving joint, a driving rocker joint, or a driving crank joint; when the output motion is a periodic cyclic motion, the driving joint is a crank.

[0025] (3) The number of active branches is equal to the degrees of freedom of the output motion.

[0026] According to the above scheme, in step S2, the configuration process of the single-power-source heavy-load multi-degree-of-freedom forming device is carried out, and the rotational motion of the spherical surface is expressed as:

[0027]

[0028] Based on the screw reciprocity relation, the constraint screw system of the mechanism's motion platform is expressed as:

[0029]

[0030] The constraint screw system of the mechanism's motion platform and the constraint screw system of the branches satisfy the following relationship:

[0031]

[0032] In the formula, Let represent the constraint spinor system of the i-th branch;

[0033] Combining formulas (6) and (7), the branched constraint spinor system of the spherical mechanism is expressed as:

[0034]

[0035] The spinor system of the branch is represented as:

[0036]

[0037] By linearly combining the motion screws in equations (11), (12) and (13), a limb that meets the motion requirements can be obtained.

[0038] According to the above scheme, in step S4, the single power source heavy-duty multi-degree-of-freedom forming device is composed of the following two methods: (1) any three branches with degrees of freedom of 3 / 4 / 5 are selected to form a branch; (2) any three branches with degrees of freedom of 6 are selected as active branches and then a branch with degrees of freedom of 3 is selected as a passive branch.

[0039] According to the above scheme, in step S5, based on the condition that the rod length remains constant, the geometric constraint condition is expressed as follows:

[0040]

[0041] In the formula, b represents the position vector of the upper ball joint in the RSS branch.i Indicates the position vector of the lower ball joint;

[0042] The mechanism velocity Jacobian matrix is ​​constructed as follows:

[0043]

[0044] According to the above scheme, based on kinematic analysis, there are a total of 16 structural parameters affecting motion accuracy, including the distribution radius r of the revolute joint. a and angle α i The distribution radius r of the upper and lower ball joints b r c and angle β i γ i Rod length l i And the height h of the moving platform; the simplified parameter set is expressed as follows:

[0045] P set ={r a r b r c l}

[0046]

[0047] The overall goal of optimization design is to accurately achieve the intended motion.

[0048] min F=max(|g(r a ,r b ,r c ,l)-f| β∈[0,2π] )

[0049]

[0050] According to the above scheme, in step S6, the fixed-point motion is represented as:

[0051]

[0052] The spinor of fixed-point motion is characterized as follows:

[0053]

[0054] The single-power-source heavy-duty multi-degree-of-freedom forming device configuration design method of the present invention has the following beneficial effects:

[0055] This invention proposes a design method for a single-power-source heavy-duty multi-degree-of-freedom forming device, synthesizing a forming mechanism that can achieve specific motion trajectories driven by a single motor. First, the basic degrees of freedom requirements of the mechanism to be synthesized are determined based on specific motion requirements. Then, by establishing a generalized kinematic model of the mechanism, the constraint conditions of the single-power-source heavy-duty multi-degree-of-freedom forming device are derived. Finally, based on spinor theory and the constraint conditions, the mechanism branches that meet the requirements are synthesized and assembled into a single-power-source heavy-duty multi-degree-of-freedom forming device. The synthesized mechanism requires only a single motor input to achieve the specific motion requirements. The single-power-source heavy-duty multi-degree-of-freedom forming device features fewer transmission chains, simple structure, high transmission efficiency, high-speed specific motion, and simple control. Attached Figure Description

[0056] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0057] Figure 1 Flowchart of the design method for a single-power-source heavy-duty multi-degree-of-freedom forming device of the present invention;

[0058] Figure 2 Specific motion diagram of this invention;

[0059] Figure 3 Schematic diagram of the single power source 3-RSS / S mechanism of this invention;

[0060] Figure 4 Motion error diagram of the present invention. Detailed Implementation

[0061] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0062] like Figure 1 As shown, the single-power-source heavy-duty multi-degree-of-freedom forming device configuration design method of the present invention includes:

[0063] S1. Based on a specific spatial motion trajectory, determine the motion degree of freedom requirements of the moving platform of the single-power-source heavy-duty multi-degree-of-freedom forming device, construct a generalized mapping model between the motion platform and the actuator, and derive the design constraints of the single-power-source heavy-duty multi-degree-of-freedom forming device. Arbitrary spatial motion can be characterized by motion screws:

[0064]

[0065] In the formula, S mp S represents a system of kinetic spinors for specific spatial motion. mpiLet the screw represent the spinor of spatial motion. Clearly, the rank of the screw system for a specific spatial motion is the degree of freedom of the desired device. Then, based on the mapping relationship between the mechanism's motion platform and the drive joints, the motion constraints of the single-power-source heavy-duty multi-degree-of-freedom forming device are determined. Based on screw theory, the motion relationship between the mechanism's motion platform and the branch joints can be expressed as:

[0066]

[0067] In the formula, S p This represents the kinetic spinor of the motion platform. ξ represents the unit rotational spin of the j-th joint in the i-th branch. ij This represents the instantaneous velocity amplitude of the j-th joint in the i-th branch.

[0068] Furthermore, the relationship between the motion of the motion platform and the velocity of the driving joints is derived as follows:

[0069]

[0070] In the formula, It represents the spindle force of the driving force of the i-th branch of the mechanism.

[0071] For a single-power-source heavy-duty multi-degree-of-freedom forming apparatus, it is desirable that the input speeds of the drive joints in the branch chain be equal. In this case, the drive joints can be driven by a driver via a set of cylindrical gears, rather than a complex real-time speed-changing and reversing device. Therefore, the relationship between the output speed of the motion platform of the single-power-source heavy-duty multi-degree-of-freedom forming apparatus and the input speed of the actuator can be defined as follows:

[0072]

[0073] According to formula (4), the three constraints of the single-power-source heavy-duty multi-degree-of-freedom forming device are as follows:

[0074] 1) The branches of a single-power-source heavy-duty multi-degree-of-freedom forming device must be coupled. The output speed of the motion platform in each direction constrains the input speed of each branch. In this case, a single-power-source heavy-duty multi-degree-of-freedom forming mechanism composed of decoupled branches cannot guarantee that the input speed of each branch is consistent. Therefore, the branches of a single-power-source heavy-duty multi-degree-of-freedom forming device should be coupled to ensure that the input speed remains unchanged when the output speed in a specific direction is zero.

[0075] 2) The type of drive joint is limited by the output speed, and it follows these principles:

[0076] The single-power-source heavy-duty multi-degree-of-freedom forming device has three possible drive joints, including drive translator joints, drive rocker joints, and drive crank joints. When the output motion is a periodic cyclic motion, the drive joint should be designed as a crank, because drive translator joints and drive rocker joints inevitably have a limit position where the velocity is zero, and cannot achieve unidirectional continuous motion. They can only be used when the output motion is a periodic reciprocating motion.

[0077] 3) The number of active branches equals the degrees of freedom of the output motion. The input motion of a single-power-source heavy-duty multi-degree-of-freedom forming device is a constrained one-dimensional space, the velocity transfer function is a finite-dimensional space (depending on the number of variable parameters of the single-power-source heavy-duty multi-degree-of-freedom forming device), while the output motion of the motion platform is an infinite-dimensional motion constraint. When the input dimension space is smaller than the output dimension space, the ideal motion can only be approximated by adjusting the variable parameters of the mechanism, but cannot be precisely achieved. Therefore, theoretically, a redundant drive system leads to over-constraint, indicating that the number of active branches equals the required degrees of freedom of the motion.

[0078] Furthermore, for industrial applications, four general design considerations will be applied.

[0079] 1) The actuator should be fixed or close to the base, which is beneficial for kinematic design and control.

[0080] 2) Since designing the prismatic joint as a non-driven joint is costly, the number of prismatic joints in the branch should be minimized.

[0081] 3) Limit the number of branch joints as much as possible to improve load-bearing capacity and reduce joint gap error.

[0082] 4) In order to ensure the dynamic and static performance of the machinery and reduce manufacturing costs, the single power source heavy-duty multi-degree-of-freedom forming device should use the same limbs.

[0083] S2. Based on the reciprocal relationship between the degree of freedom requirements and the screw system of the moving platform of the single-power-source heavy-duty multi-degree-of-freedom forming device, establish the mechanism motion screw system and constraint screw system. On this basis, establish the branch constraint screw system and motion screw system of the single-power-source heavy-duty multi-degree-of-freedom forming device.

[0084] For ease of explanation, this example uses spherical rotational motion (e.g.) Figure 2 Taking the single-power-source heavy-duty multi-degree-of-freedom forming device (shown as 3R motion) as an example, the configuration process of the single-power-source heavy-duty multi-degree-of-freedom forming device is carried out. The rotational motion of the spherical surface can be expressed as:

[0085]

[0086] Therefore, based on the screw reciprocity relation, the constraint screw system of the mechanism's motion platform can be expressed as:

[0087]

[0088] The constraint screw system of the mechanism's motion platform and the constraint screw system of the branches satisfy the following relationship:

[0089]

[0090] In the formula, Let represent the constraint spinor system of the i-th branch.

[0091] Combining formulas (6) and (7), the branched constraint spinor system of the spherical mechanism can be expressed as:

[0092]

[0093] The spinor system of the branch can then be expressed as:

[0094]

[0095]

[0096] By linearly combining the motion screws in equations (11), (12) and (13), a limb that meets the motion requirements can be obtained.

[0097] S3. Combining the design constraints of the single-power-source heavy-duty multi-degree-of-freedom forming device and the branch motion screw system, the motion screws in the motion screw system are linearly combined to synthesize the motion branches that meet the design constraints and motion requirements of the single-power-source heavy-duty multi-degree-of-freedom forming device.

[0098] Without considering the sequential arrangement of the branch joints, all branches are summarized in Table 1. It should be noted that branches with six or more degrees of freedom are also synthesized. Mechanisms assembling these branches can achieve predetermined motions by introducing low-degree-of-freedom passive branches, such as 3-RSS / RRR, 3-PSS / S, etc. In Table 1, the subscript "O" indicates that the joints intersect at a point, the subscript "E" indicates that three consecutive joints form an equivalent planar joint, and the subscripts "U" and "S" indicate that the axes of two or three consecutive revolute joints intersect at a point, which can be replaced by U and S joints respectively. Spherical mechanisms can be generated using three or more identical branches as shown in Table 1. Furthermore, to meet the general design considerations of single-power-source heavy-duty multi-degree-of-freedom forming devices, the (RR) branches... U and (RRR) S Replace them with U and S joints respectively, without considering branches containing P joints.

[0099] Table 1. Branching synthesis results satisfying spherical motion

[0100]

[0101] S4, arbitrarily select branches of equal number of degrees of freedom to assemble, and synthesize a fully symmetrical single-power-source heavy-duty multi-degree-of-freedom forming device configuration.

[0102] Based on the comprehensive results of the branches in Table 1, and combined with the constraints of the single-power-source heavy-duty multi-degree-of-freedom forming device, the single-power-source heavy-duty multi-degree-of-freedom forming device can be constructed in the following two ways: ① Arbitrarily select 3 branches with degrees of freedom of 3 / 4 / 5, for example: 3-(RRR)o, (RRR)oP(RRR)o-(RR)o(RRR). E ② Select any 3 branches with 6 degrees of freedom as active branches, and then select one branch with 3 degrees of freedom as passive branches to form a chain, for example, 3-R (RRR). S1 (RRR) S2 / (RRR)o. Furthermore, considering the advantages of fully symmetrical mechanisms in design, motion, accuracy, and dynamics, the basic configurations of all fully symmetrical mechanisms that meet the requirements are given here, combined with the constraints of a single-power-source heavy-duty multi-degree-of-freedom forming device, as shown in Table 2.

[0103] Table 2. Overall Results of Spherical Kinematic Mechanism

[0104]

[0105] S5. Taking a specific single-power-source heavy-duty multi-degree-of-freedom forming device configuration as an example, establish the global velocity Jacobian matrix of the single-power-source heavy-duty multi-degree-of-freedom forming device under the specific configuration, and optimize the variable structural parameters based on minimizing the global motion error.

[0106] The 3-RSS / S configuration result (simplified structural diagram as shown) Figure 3 Taking the example shown, based on the condition that the rod length remains constant, the geometric constraint condition of 3-RSS / S can be expressed as:

[0107]

[0108] In the formula, b represents the position vector of the upper ball joint in the RSS branch. i This represents the position vector of the lower ball joint.

[0109] Furthermore, the mechanism velocity Jacobian matrix is ​​constructed as follows:

[0110]

[0111] According to the kinematic model of the single-power-source heavy-duty multi-degree-of-freedom forming device established by formula (15), it can be seen that under the single actuator driving strategy, the motion trajectory of the motion platform depends entirely on the structural dimensions, and the selected combination of structural parameters will directly affect the ability of the motion platform to achieve the defined motion. Therefore, it is necessary to find a set of optimal structural parameters to minimize the motion error of the motion platform driven by a single actuator. According to kinematic analysis, there are a total of 16 structural parameters that affect the motion accuracy, including the distribution radius r of the revolute joint. a and angle α i The distribution radius r of the upper and lower ball joints b r c and angle β i γ i Rod length l i And the height h of the moving platform. Too many parameters to solve would lead to high optimization costs; therefore, a simplified set of parameters was selected for the active branches with symmetrical structures. The simplified parameter set is expressed as follows:

[0112] P set ={r a r b r c l}

[0113]

[0114] The overall goal of optimization design is to accurately achieve the intended motion.

[0115] min F=max(|g(r a ,r b ,r c ,l)-f| β∈[0,2π] )

[0116]

[0117] S6. Finally, the configuration and parameters of the single-power-source heavy-duty multi-degree-of-freedom forming device that satisfies a specific motion trajectory are obtained.

[0118] by Figure 2 Taking the fixed-point motion shown as an example, parameter optimization of a single-power-source heavy-load multi-degree-of-freedom forming device is performed. The fixed-point motion can be expressed as:

[0119]

[0120] The spinor of fixed-point motion is characterized as follows:

[0121]

[0122] Considering the design parameter conditions, the geometric parameters and the range of variable parameters that need to be optimized for the single power source heavy-duty multi-degree-of-freedom forming device 3-RSS / S were determined, as shown in Table 3. According to formula (16), the optimized parameter set of 3-RSS / S was obtained through dimensional synthesis, as shown in Table 4.

[0123] Table 3 Design parameters of 3-RSS / S single-power-source heavy-duty multi-degree-of-freedom forming device

[0124]

[0125] Table 4 Optimization parameters of 3-RSS / S single-power-source heavy-duty multi-degree-of-freedom forming device

[0126]

[0127] Under the above optimal configuration parameters, the motion angle curves of the single-power-source heavy-duty multi-degree-of-freedom forming device are obtained, as follows: Figure 4 As shown, from Figure 4 It can be seen that the single-power-source heavy-duty multi-degree-of-freedom forming device configuration design method of the present invention can achieve a specific spatial motion trajectory with very small, negligible error. The above results demonstrate that the single-power-source heavy-duty multi-degree-of-freedom forming device configuration design method of the present invention is feasible.

[0128] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A single power source heavy load multi-degree of freedom forming device configuration design method, characterized by, The method comprises the following steps: S1, determining the motion degree of freedom requirement of a single power source heavy load multi-degree of freedom forming device according to a specific spatial motion trajectory, constructing a generalized mapping model between a motion platform and a driver, and deducing a design constraint condition of the single power source heavy load multi-degree of freedom forming device; S2, based on the degree of freedom requirement of the single power source heavy load multi-degree of freedom forming device and the screw system reciprocal relationship, establishing a mechanism motion screw system and a constraint screw system, and establishing a branch constraint screw system and a motion screw system of the single power source heavy load multi-degree of freedom forming device on the basis of the same; S3, combining the design constraint condition and the branch motion screw system of the single power source heavy load multi-degree of freedom forming device, linearly combining the motion screws in the motion screw system, and then synthesizing a motion branch chain meeting the design constraint condition and the motion requirement of the single power source heavy load multi-degree of freedom forming device; S4, assembling a certain number of branch chains, and synthesizing all the symmetrical single power source heavy load multi-degree of freedom forming device configurations; S5, establishing a global velocity Jacobian matrix of the single power source heavy load multi-degree of freedom forming device under a specific configuration, and optimizing variable structure parameters based on global motion error minimization; S6, finally obtaining a single power source heavy load multi-degree of freedom forming device configuration and parameters meeting a specific motion trajectory; In the step S5, according to the constant length condition, the geometric constraint condition is expressed as: (14) wherein denotes the position vector of the upper spherical joint in the RSS branch, denotes the position vector of the lower spherical joint; The mechanism velocity Jacobian matrix is constructed as follows: (15)； According to kinematic analysis, the total number of structure parameters affecting the motion accuracy is 16, including the distribution radius of revolute pair R r a and angle α i , the distribution radius of upper and lower spherical hinge r b , r c and angle β i 、γ i , the length of rod l i and the height of moving platform h ; the simplified parameter group is expressed as follows: （16） Accurate realization of the intended motion is the overall goal of the optimization design; （17）； In the step S6, the fixed point motion is expressed as: (18) The screw representation of the fixed point motion is: （19）。 2. The single power source heavy load multi-degree of freedom forming device configuration design method according to claim 1, characterized by, In the step S1, the spatial arbitrary motion is represented by a motion screw, and the formula is as follows: (1) wherein represent the screw system of a specific spatial motion, represent the screw of a spatial motion; the rank of the screw system of a specific spatial motion is the degree of freedom of the required device; the motion constraint condition of the single power source heavy load multi-degree of freedom forming device is determined according to the mapping relationship between the mechanism motion platform and the driving joint; based on the screw theory, the motion relationship between the mechanism motion platform and the branch joint is represented as: (2) wherein represents the motion screw of the motion platform, represents the unit motion screw of the joint, i represents the unit motion screw of the joint in the branch chain, j represents the unit motion screw of the joint, represents the unit motion screw of the joint in the branch chain, i represents the unit motion screw of the joint, j represents the instantaneous velocity amplitude of the joint in the branch chain, The velocity relationship between the motion platform motion and the driving joint is: (3) In the formula, representing the mechanism i branched driving force screw The relationship between the output velocity of the single power source heavy load multi-degree of freedom forming device motion platform and the input velocity of the actuator is defined as: (4) According to formula (4), the design constraint condition of the single power source heavy load multi-degree of freedom forming device is determined.

3. The single power source heavy load multi-degree of freedom forming device configuration design method according to claim 2, characterized by, The design constraint condition of the single power source heavy load multi-degree of freedom forming device includes: (1) The branch chain of the single power source heavy load multi-degree of freedom forming device must be coupled; (2) The driving joint of the single power source heavy load multi-degree of freedom forming device is a driving mobile joint, a driving rocker joint or a driving crank joint; when the output motion is a periodic cyclic motion, the driving joint is a crank; (3) The number of active branch chains is equal to the degree of freedom of the output motion.

4. The single power source heavy load multi-degree of freedom forming device configuration design method according to claim 1, characterized by, In the step S2, the configuration process of the single power source heavy load multi-degree of freedom forming device is performed, and the motion screw of the spherical surface rotation motion is expressed as: (5) Based on the screw reciprocal relationship, the constraint screw system of the mechanism motion platform is expressed as: (6) The constraint screw system of the mechanism motion platform and the constraint screw system of the branch chain satisfy the following relationship: (7) wherein represents the i branched constraint torque system; Combined with formula (6) and (7), the branch constraint screw system of the spherical surface mechanism is expressed as: (8) (9) (10) The motion screw system of the branch chain is expressed as: (11) (12) (13) Linearly combining the motion screws in formula (11), (12) and (13), the limb meeting the motion requirement is obtained.

5. The single power source heavy load multi-degree of freedom forming device configuration design method according to claim 1, characterized by, In the step S4, the single power source heavy load multi-degree of freedom forming device is composed of the following two ways: (1) any 3 branch chains with 3 / 4 / 5 degrees of freedom are selected to form a group; (2) any 3 branch chains with 6 degrees of freedom are selected as active branch chains, and then a branch chain with 3 degrees of freedom is selected as a passive branch chain to form a group.

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