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

Abstract

The invention relates to a configuration design method for a single-power-source heavy-load multi-degree-of-freedom forming device. The method comprises the following steps that S1, design constraint conditions of the single-power-source heavy-load multi-degree-of-freedom forming device are deduced; s2, a branched chain constraint spinor system and a motion spinor system of the single-power-source heavy-load multi-degree-of-freedom forming device are determined; s3, motion branch chains meeting design constraint conditions and motion requirements of the single-power-source heavy-load multi-degree-of-freedom forming device are synthesized; s4, the configuration of the full-symmetric single-power-source heavy-load multi-degree-of-freedom forming device is synthesized; s5, establishing a global speed Jacobian matrix, and optimizing variable structure parameters based on global motion error minimization; and S6, finally obtaining the configuration and parameters of the single-power-source heavy-load multi-degree-of-freedom forming device meeting the specific motion trail. According to the single-power-source heavy-load multi-degree-of-freedom forming device, configuration integration and scale integration of the single-power-source heavy-load multi-degree-of-freedom forming device can be achieved, and low control, low cost and high speed of the device are guaranteed while specific required movement is achieved.

Description

Technical Field

[0001] The invention relates to the field of configuration design of heavy-loaded multi-degree-of-freedom forming devices, and more specifically, to a configuration design method of a heavy-loaded multi-degree-of-freedom forming device with a single power source. Background Art

[0002] Compared with the serial mechanism, the multi-chain closed-loop structure of the parallel mechanism has the advantages of strong load-bearing capacity, high rigidity and high precision, and is particularly suitable for the execution system of heavy-load forming devices. The primary task in the research and development of heavy-load forming devices is to design a configuration that meets the requirements of motion freedom / motion trajectory, that is, the configuration synthesis of the parallel mechanism. At present, a variety of synthesis methods have been proposed by scholars, mainly including those based on screw theory, displacement group theory, virtual loop method and POC set method. The parallel mechanism synthesized by the above methods is usually equipped with multiple actuators to achieve precise and arbitrary spatial motion, which leads 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-load multi-degree-of-freedom forming device, which can realize the configuration integration and scale integration of the single-power source heavy-load multi-degree-of-freedom forming device, while realizing the movement required by specific requirements, ensuring the low control, low cost and high speed of the device.

[0004] The technical solution adopted by the present invention to solve the technical problem is: constructing a configuration design method for a single-power-source heavy-load multi-degree-of-freedom forming device, comprising the following steps:

[0005] S1. According to the specific spatial motion trajectory, determine the motion freedom requirements of the moving platform of the single-power source heavy-load multi-degree-of-freedom forming device, construct a generalized mapping model between the moving platform and the driver, and derive the design constraints of the single-power source heavy-load multi-degree-of-freedom forming device;

[0006] S2. Based on the reciprocal relationship between the degree of freedom requirements and the screw system of the dynamic platform of the single-power-source heavy-load multi-degree-of-freedom forming device, the mechanism motion screw system and the constraint screw system are established. On this basis, the branched constraint screw system and the motion screw system of the single-power-source heavy-load multi-degree-of-freedom forming device are established;

[0007] S3. Combining the design constraints of the single-power-source heavy-load multi-degree-of-freedom forming device and the branched chain motion screw system, linearly combining the motion screws in the motion screw system, and then synthesizing the motion branched chain that meets the design constraints and motion requirements of the single-power-source heavy-load multi-degree-of-freedom forming device;

[0008] S4, arbitrarily assemble branches with the same number of degrees of freedom to synthesize a fully symmetrical single-power-source heavy-load multi-degree-of-freedom forming device configuration;

[0009] S5. Establish the global velocity Jacobian matrix of the 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 a single-power-source heavy-load multi-degree-of-freedom forming device that meets a specific motion trajectory are obtained.

[0011] According to the above scheme, in step S1, any spatial motion is characterized by a motion spinor, and the formula is as follows:

[0012]

[0013] In the formula, S mp A system of kinematic spinors representing a specific spatial motion, S mpi The screw represents the spatial motion; the rank of the screw system of a specific spatial motion is the degree of freedom of the required device; according to the mapping relationship between the mechanism motion platform and the driving joint, the motion constraint conditions of the single-power-source heavy-load multi-degree-of-freedom forming device are determined; based on the screw theory, the motion relationship between the mechanism motion platform and the branch chain joint is expressed as:

[0014]

[0015] In the formula, S p represents the motion rotation of the motion platform, represents the unit motion rotation of the jth joint in the i-th branch, ξ ij represents the instantaneous velocity amplitude of the jth joint in the i-th branch;

[0016] The relationship between the motion platform movement and the speed of the driving joint is:

[0017]

[0018] In the formula, represents the driving force screw of the i-th branch of the mechanism;

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

[0020]

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

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

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

[0024] (2) The driving joint of the single-power-source heavy-load 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 kinematic rotation of the spherical rotational motion is expressed as:

[0027]

[0028] Based on the reciprocal relationship of the screw, the constrained screw system of the mechanism motion platform is expressed as:

[0029]

[0030] The constraint screw system of the mechanism motion platform and the constraint screw system of the branch chain satisfy the following relationship:

[0031]

[0032] In the formula, represents the constrained spinor system of the i-th branch;

[0033] Combining formulas (6) and (7), the branch-chain constraint screw system for the spherical mechanism is expressed as:

[0034]

[0035] The kinematic spin system of the branched chain is expressed as:

[0036]

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

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

[0039] According to the above scheme, in step S5, according to the condition that the rod length remains unchanged, the geometric constraint condition is expressed as:

[0040]

[0041] In the formula, represents the position vector of the upper spherical joint in the RSS branch chain, bi represents the position vector of the lower spherical joint;

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

[0043]

[0044] According to the above scheme, based on kinematic analysis, the total number of structural parameters that affect motion accuracy is 16, including the distribution radius r of the rotation pair R. a and angle α i , the upper and lower spherical joint distribution radius r b 、r c and angle β i , γ i , rod length l i And the height of the moving platform h; the simplified parameter group is expressed as follows:

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

[0046]

[0047] Accurately achieving the intended motion is the overall goal of optimal design;

[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 expressed as:

[0051]

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

[0053]

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

[0055] The present invention proposes a configuration design method for a single-power source heavy-load multi-degree-of-freedom forming device, and synthesizes a type of forming mechanism that can achieve a specific required motion trajectory through a single motor drive. First, the basic degree of freedom requirements of the mechanism to be synthesized are determined based on the specific motion requirements. Then, by establishing a generalized kinematic model of the mechanism, the constraints of the single-power source heavy-load multi-degree-of-freedom forming device mechanism are derived. Then, based on the screw theory and the constraints, the mechanism branches that meet the requirements are synthesized and assembled into a single-power source heavy-load multi-degree-of-freedom forming device. The comprehensively designed mechanism only requires a single motor input to achieve specific motion requirements. The single-power source heavy-load multi-degree-of-freedom forming device has the characteristics of few transmission chains, simple structure, high transmission efficiency, etc. It can achieve high-speed specific motion and is simple to control. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0057] Figure 1 Flow chart of the design method of the single power source heavy-load multi-degree-of-freedom forming device of the present invention;

[0058] Figure 2 Schematic diagram of specific movements of the present invention;

[0059] Figure 3 A schematic diagram of the single power source 3-RSS / S mechanism of the present invention;

[0060] Figure 4 Motion error diagram of the present invention. 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 design method of the single-power-source heavy-load multi-degree-of-freedom forming device of the present invention includes:

[0063] S1. According to the specific spatial motion trajectory, determine the motion freedom requirements of the moving platform of the single-power source heavy-load multi-degree-of-freedom forming device, build a generalized mapping model between the motion platform and the driver, and derive the design constraints of the single-power source heavy-load multi-degree-of-freedom forming device. Arbitrary spatial motion can be characterized by motion spinor:

[0064]

[0065] In the formula, S mp A system of kinematic spinors representing a specific spatial motion, S mpiRepresents the screw of spatial motion. Obviously, the rank of the screw system of a specific spatial motion is the degree of freedom of the required device. Then, according to the mapping relationship between the mechanism motion platform and the driving joint, the motion constraint conditions of the single-power source heavy-load multi-degree-of-freedom forming device are determined. Based on the screw theory, the motion relationship between the mechanism motion platform and the branch chain joint can be expressed as:

[0066]

[0067] In the formula, S p represents the motion rotation of the motion platform, represents the unit motion rotation of the jth joint in the i-th branch, ξ ij Represents the instantaneous velocity amplitude of the jth joint in the i-th branch.

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

[0069]

[0070] In the formula, Represents the driving force screw of the i-th branch of the mechanism.

[0071] For a single-power-source heavy-duty multi-degree-of-freedom forming device, it is expected that the input speeds between the drive joints of the branch chain are equal. In this case, the drive joints can be driven by the driver through a cylindrical gear set instead of a complex real-time speed change 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 device and the input speed of the actuator can be defined as:

[0072]

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

[0074] 1) The branches of the single-power source heavy-load 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, it is difficult for the single-power source heavy-load multi-degree-of-freedom forming mechanism composed of decoupled branches to ensure that the input speed of each branch is consistent. Therefore, the branches of the single-power source heavy-load multi-degree-of-freedom forming device should be coupled to ensure that when the output speed in a specific direction is zero, the input speed remains unchanged;

[0075] 2) The type of driven joint is limited by the output speed, which follows the following principles:

[0076] There are three possible driving joints for the single-power-source heavy-load multi-degree-of-freedom forming device, including driving mobile joints, driving rocker joints, and driving crank joints. When the output motion is a periodic cyclic motion, the driving joint should be designed as a crank, because both the driving mobile joint and the actuating rocker joint inevitably have a limit position of zero speed 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 is equal to the degrees of freedom of the output motion. The input motion of the single-power source heavy-load multi-degree-of-freedom forming device is a restricted one-dimensional space, the speed transfer function is a finite-dimensional space (depending on the number of variable parameters of the single-power source heavy-load multi-degree-of-freedom forming device), and 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 achieved accurately. Therefore, theoretically speaking, the redundant drive system will lead to over-constraint, indicating that the number of active branches is equal to the degrees of freedom of the required motion.

[0078] Further, for the purpose of industrial application, four general design considerations will apply,

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

[0080] 2) Since the design cost of designing the moving joint as a non-driven joint is high, the number of moving joints in the branch chain should be minimized.

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

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

[0083] S2. Based on the reciprocal relationship between the degree of freedom requirements of the dynamic platform of the single-power source heavy-load multi-degree-of-freedom forming device and the screw system, the mechanism motion screw system and constraint screw system are established. On this basis, the branched constraint screw system and motion screw system of the single-power source heavy-load multi-degree-of-freedom forming device are established.

[0084] For the convenience of explanation, the spherical rotation motion (such as Figure 2 Taking the 3R motion shown in the figure as an example, the single-power-source heavy-load multi-degree-of-freedom forming device is configured to perform the single-power-source heavy-load multi-degree-of-freedom forming device. The motion rotation of the spherical rotation motion can be expressed as:

[0085]

[0086] Therefore, based on the reciprocal relationship of the screw, the constrained screw system of the mechanism motion platform can be expressed as:

[0087]

[0088] The constraint screw system of the mechanism motion platform and the constraint screw system of the branch chain satisfy the following relationship:

[0089]

[0090] In the formula, represents the constrained spinor system of the i-th branch.

[0091] Combining formulas (6) and (7), the branch-constrained screw system for the spherical mechanism can be expressed as:

[0092]

[0093] Then the motion spinor system of the branch chain can be expressed as:

[0094]

[0095]

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

[0097] S3. Combine the design constraints of the single-power-source heavy-load multi-degree-of-freedom forming device and the branched motion screw system, perform linear combinations of the motion screws in the motion screw system, and then synthesize a motion branch that meets the design constraints and motion requirements of the single-power-source heavy-load multi-degree-of-freedom forming device.

[0098] Without considering the order of branch joints, all branches are summarized as shown in Table 1. It should be pointed out that branches with 6 or more degrees of freedom are also synthesized, and the mechanism assembled with these branches can achieve the given motion 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 certain 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 2 or 3 consecutive revolute pairs intersect at a point, which can be replaced by U and S joints respectively. The spherical mechanism can be generated by three or more identical branches shown in Table 1, and in order to meet the general design considerations of single-power source heavy-load multi-degree-of-freedom forming devices, the (RR) in the branch. U and (RRR) S Use U and S joints to replace them respectively, and do not consider branches containing P joints.

[0099] Table 1 Comprehensive results of branches satisfying spherical motion

[0100]

[0101] S4. Assemble any branch chains with equal number of degrees of freedom to synthesize a fully symmetrical single-power source heavy-load multi-degree-of-freedom forming device configuration.

[0102] According to the comprehensive results of the branches in Table 1, combined with the constraints of the single-power source heavy-load multi-degree-of-freedom forming device, the single-power source heavy-load multi-degree-of-freedom forming device can be constructed in the following two ways: ① Take any three branches with 3 / 4 / 5 degrees of freedom, for example: 3-(RRR)o, (RRR)oP(RRR)o-(RR)o(RRR) E ; ② Choose any 3 branches with 6 degrees of freedom as active branches and then choose another branch with 3 degrees of freedom as passive branch, for example 3-R (RRR) S1 (RRR) S2 / (RRR)o. Further, considering the superiority of the fully symmetrical mechanism in design, motion, precision, and dynamics, the basic configuration of all fully symmetrical mechanisms that meet the requirements is given here in combination with the constraints of the single-power-source heavy-load multi-degree-of-freedom forming device, as shown in Table 2.

[0103] Table 2 Comprehensive results of spherical motion mechanism

[0104]

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

[0106] According to the configuration results, 3-RSS / S (structure diagram as shown in Figure 3 As shown in the figure, the geometric constraint of 3-RSS / S can be expressed as follows:

[0107]

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

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

[0110]

[0111] According to the kinematic model of the single-power-source heavy-load 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 is completely dependent on the structural size, and the selected combination of structural parameters will directly affect the ability of the motion platform to achieve 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 the kinematic analysis, the total number of structural parameters that affect the motion accuracy is 16, including the distribution radius r of the revolute pair R. a and angle α i , the upper and lower spherical joint distribution radius r 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 be solved will lead to high optimization cost, so a set of simplified parameters is selected for the active branch chain with symmetrical structure. The simplified parameter group is expressed as follows:

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

[0113]

[0114] Accurately achieving the desired motion is the overall goal of optimal design.

[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 a single-power-source heavy-load multi-degree-of-freedom forming device that meets a specific motion trajectory are obtained.

[0118] by Figure 2 Taking the fixed-point motion shown in the figure as an example, the parameters of the single-power-source heavy-load multi-degree-of-freedom forming device are optimized. The fixed-point motion can be expressed as:

[0119]

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

[0121]

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

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

[0124]

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

[0126]

[0127] Under the above optimal configuration parameters, the motion angle curve of the single-power-source heavy-load multi-degree-of-freedom forming device is obtained, as shown in Figure 4 As shown, from Figure 4 It can be seen that the configuration design method of the single-power source heavy-load multi-degree-of-freedom forming device of the present invention can realize a specific spatial motion trajectory, and the error is very small and can be ignored. The above results show that the configuration design method of the single-power source heavy-load multi-degree-of-freedom forming device of the present invention is feasible.

[0128] 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 modes, which are merely illustrative rather than 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 within the protection of the present invention.

Claims

1. A configuration design method for a single-power-source heavy-load multi-degree-of-freedom forming device, characterized in that: The following steps are involved: S1. According to the specific spatial motion trajectory, determine the motion freedom requirements of the moving platform of the single-power source heavy-load multi-degree-of-freedom forming device, construct a generalized mapping model between the moving platform and the driver, and derive the design constraints of the single-power source heavy-load multi-degree-of-freedom forming device; S2. Based on the reciprocal relationship between the degree of freedom requirements and the screw system of the dynamic platform of the single-power-source heavy-load multi-degree-of-freedom forming device, the mechanism motion screw system and the constraint screw system are established. On this basis, the branched constraint screw system and the motion screw system of the single-power-source heavy-load multi-degree-of-freedom forming device are established; S3. Combining the design constraints of the single-power-source heavy-load multi-degree-of-freedom forming device and the branched chain motion screw system, linearly combining the motion screws in the motion screw system, and then synthesizing the motion branched chain that meets the design constraints and motion requirements of the single-power-source heavy-load multi-degree-of-freedom forming device; S4, arbitrarily assemble branches with the same number of degrees of freedom to synthesize a fully symmetrical single-power-source heavy-load multi-degree-of-freedom forming device configuration; S5. Establish the global velocity Jacobian matrix of the 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; S6. Finally, the configuration and parameters of a single-power-source heavy-load multi-degree-of-freedom forming device that meets a specific motion trajectory are obtained.

2. The configuration design method of a single-power-source heavy-load multi-degree-of-freedom forming device according to claim 1 is characterized in that: In step S1, any spatial motion is characterized by a motion spinor, and the formula is as follows: In the formula, S mp A system of kinematic spinors representing a specific spatial motion, S mpi The screw represents the spatial motion; the rank of the screw system of a specific spatial motion is the degree of freedom of the required device; according to the mapping relationship between the mechanism motion platform and the driving joint, the motion constraint conditions of the single-power-source heavy-load multi-degree-of-freedom forming device are determined; based on the screw theory, the motion relationship between the mechanism motion platform and the branch chain joint is expressed as: In the formula, S p represents the motion rotation of the motion platform, represents the unit motion rotation of the jth joint in the i-th branch, ξ ij represents the instantaneous velocity amplitude of the jth joint in the i-th branch; The relationship between the motion platform movement and the speed of the driving joint is: In the formula, represents the driving force screw of the i-th branch of the mechanism; The relationship between the output speed of the motion platform of the single-power-source heavy-load multi-degree-of-freedom forming device and the input speed of the actuator is defined as: According to formula (4), the design constraints of the single-power-source heavy-load multi-degree-of-freedom forming device are determined.

3. The configuration design method of a single-power-source heavy-load multi-degree-of-freedom forming device according to claim 2 is characterized in that: The design constraints of the single-power-source heavy-load multi-degree-of-freedom forming device include: (1) The branches 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 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; (3) The number of active branches is equal to the degrees of freedom of the output motion.

4. The configuration design method of a single-power-source heavy-load multi-degree-of-freedom forming device according to claim 1 is characterized in that: In step S2, the configuration process of the single-power-source heavy-load multi-degree-of-freedom forming device is performed, and the kinematic rotation quantity of the spherical rotational motion is expressed as: Based on the reciprocal relationship of the screw, the constrained screw system of the mechanism motion platform is expressed as: The constraint screw system of the mechanism motion platform and the constraint screw system of the branch chain satisfy the following relationship: In the formula, represents the constrained spinor system of the i-th branch; Combining formulas (6) and (7), the branch-chain constraint screw system for the spherical mechanism is expressed as: The kinematic spin system of the branched chain is expressed as: By linearly combining the motion screws in equations (11), (12) and (13), we can obtain a limb that meets the motion requirements.

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

6. The configuration design method of a single-power-source heavy-load multi-degree-of-freedom forming device according to claim 1 is characterized in that: In step S5, according to the condition that the rod length remains unchanged, the geometric constraint condition is expressed as: In the formula, represents the position vector of the upper spherical joint in the RSS branch chain, b i represents the position vector of the lower spherical joint; The mechanism velocity Jacobian matrix is ​​constructed as follows:

7. The configuration design method of a single-power-source heavy-load multi-degree-of-freedom forming device according to claim 6 is characterized in that: According to kinematic analysis, the total number of structural parameters that affect motion accuracy is 16, including the distribution radius r of the revolute pair R. a and angle α i , the upper and lower spherical joint distribution radius r b 、r c and angle β i , γ i , rod length l i And the height of the moving platform h; the simplified parameter group is expressed as follows: Accurately achieving the intended motion is the overall goal of optimal design; min F=max(g(r a ,r b ,r c ,l)-f β∈ [ 0,2 p ] ) 8. The configuration design method of a single-power-source heavy-load multi-degree-of-freedom forming device according to claim 7 is characterized in that: In step S6, the fixed-point motion is expressed as: The spinor of fixed-point motion is characterized by:

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