A method for simultaneous design of robot mechanism topology and scale

Abstract

The present invention discloses a method for synchronous design of robot mechanism topology and scale, including the following steps: based on continuous motion, establish a robot mechanism topology model; on the basis of the topology model, introduce scale parameters to obtain a motion model; construct a performance model of the mechanism; determine the topology and scale variables to be optimized; establish a robot mechanism topology and scale synchronous design model; perform solution set search on the robot mechanism topology and scale synchronous design model; obtain the optimal topology of the mechanism and its scale parameters. The design method proposed in the present invention establishes an algebraic connection between the mechanism topology and performance, and realizes performance-oriented quantitative evaluation and selection of topology; the design method proposed in the present invention comprehensively considers the coupling influence of topology and scale on performance, proposes a topology and scale synchronous optimization design process, and solves the problem of the separation of topology design and scale design.

Description

Technical Field

[0001] The present invention belongs to the technical field of robot mechanism design, and in particular relates to a method for synchronously designing robot mechanism topology and scale. Background Art

[0002] The mechanism is the skeleton and actuator of the robot, and it is also the "gene" that determines its function, that is, the number and type of output motions, and its performance, that is, the motion and force transmission characteristics. The topological design and scale design of the mechanism taking into account the service environment requirements have always been difficult issues in the study of robots and mechanisms, which are specifically reflected in the following aspects:

[0003] First, it is difficult to quantify and optimize the topology of the organization.

[0004] Topology refers to the logical connection relationship, component loops and layout of mechanism components. It is the main basis for judging the degree of freedom and motion properties, and determines the application function of the mechanism. Mechanism topology involves many factors such as the number and type of component branches, the arrangement order of motion joints, and the orientation of axes, thus showing great diversity and complexity. Topological design aims to obtain all mechanism topologies that meet functional requirements and select the optimal topology from them.

[0005] However, due to the lack of quantitative evaluation of the topological characteristics of the mechanism, existing methods usually carry out topological optimization based on engineering experience, resulting in uneven optimization quality. How to carry out topological optimization guided by quantitative evaluation indicators has become a bottleneck problem that needs to be solved in the original innovation of parallel robot mechanisms;

[0006] Second, topological design and scale design are separated from each other

[0007] Topology reflects the essential motion law of the mechanism, which not only determines the function of the mechanism, but also determines the performance of the parallel mechanism together with the scale. However, existing design methods usually only carry out topological design based on functional requirements and carry out scale design based on performance requirements.

[0008] Chinese patents ZL202110521438.4 and ZL201710948880.9 respectively provide "An efficient method for multi-objective optimization design of parallel robots" and "A multi-objective optimization design method for parallel mechanisms considering parameter uncertainty", which provide effective methods for scale design of parallel robot mechanisms. However, the optimization results obtained are only the performance of a specific topology at the optimal scale, and the impact of topology on performance cannot be measured.

[0009] Therefore, for original innovation in robot mechanisms, designers often need to repeatedly perform scale design on the specific topology obtained by topological design and compare the optimization results until the optimal mechanism is obtained, which greatly restricts the efficiency and quality of independent research and development of high-performance robot mechanisms.

[0010] The topological design and scale design issues of parallel mechanisms have been a long-standing challenge in the robotics and mechanism community. Conducting such research has important theoretical significance and application value for achieving original innovative designs of parallel robot mechanisms that meet functional and performance requirements.

[0011] In response to the above-mentioned difficult problems, the present invention provides a method for synchronously designing the topology and scale of a robot mechanism guided by functional and performance requirements. Summary of the invention

[0012] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a method for synchronously designing the topology and scale of a robot mechanism.

[0013] The technical solution of the present invention is: a method for synchronously designing the topology and scale of a robot mechanism, comprising the following steps:

[0014] ⅰ. Define topological parameters and establish the robot mechanism topological model based on continuous motion;

[0015] ⅱ. Based on the topological model, the scale parameter is introduced to obtain the motion model;

[0016] ⅲ. Construct the performance model of the organization;

[0017] iv. Determine the topological and scale variables to be optimized;

[0018] ⅴ. Establish a synchronous design model of robot mechanism topology and scale;

[0019] ⅵ. Search for solutions to the robot mechanism topology and scale synchronization design model;

[0020] ⅶ. Obtain the optimal topology and scale parameters of the mechanism.

[0021] Furthermore, in step i, a topological model of the robot mechanism is established based on continuous motion. The specific process is as follows:

[0022] First, determine the modeling type and choose either forward modeling or reverse modeling;

[0023] Then, forward modeling for several specific topologies is adopted;

[0024] Or use inverse modeling to build the mechanism topology for known desired motion;

[0025] Finally, the topological feature parameters are constructed.

[0026] Furthermore, the topological characteristic parameters include the number of branches, the type of branch motion joints, the order of branch motion joints, the assembly characteristics of the motion joints, and the driving scheme.

[0027] Furthermore, step ii introduces a scale parameter based on the topological model. The specific process is as follows:

[0028] First, the robot mechanism topology model is obtained;

[0029] Then, the scale parameter is introduced, and the robot mechanism topology model is considered to move from the initial state to any state;

[0030] Finally, the displacement model is obtained.

[0031] Furthermore, step ii also includes obtaining a velocity model and an acceleration model, and the specific process is as follows:

[0032] First, the first-order derivative of the displacement model is solved to obtain the velocity model, and the topological and scale parameters are transferred to the velocity model respectively;

[0033] Then, the second-order derivative of the displacement model is solved to obtain the acceleration model, and the topological and scale parameters are transferred to the acceleration model respectively.

[0034] Furthermore, step iii builds the performance model of the organization, and the specific process is as follows:

[0035] Firstly, the displacement model, velocity model and acceleration model containing topological parameters and scale parameters are obtained;

[0036] Then, a performance model containing topological parameters and scale parameters is constructed based on the displacement model, velocity model and acceleration model.

[0037] Furthermore, the performance model includes a kinematic model, a stiffness model and a dynamic model.

[0038] Furthermore, step iv determines the topological and scale variables to be optimized, and the specific process is as follows:

[0039] First, the obtained displacement model contains topological parameters and scale parameters;

[0040] Then, based on the topological characteristic parameters, the topological and scale variables to be optimized can be determined.

[0041] Furthermore, step V establishes a synchronous design model of robot mechanism topology and scale. The specific process is as follows:

[0042] First, construct corresponding performance optimization indicators according to application requirements;

[0043] Then, the topological parameters and scale parameters to be optimized are defined as design variables to determine the feasible domain range;

[0044] Then, define the constraints of the optimization design, which include performance constraints and geometric constraints;

[0045] Finally, a synchronous design model of robot mechanism topology and scale is obtained.

[0046] Furthermore, step VI searches for a solution set of the robot mechanism topology and scale synchronization design model. The specific process is as follows:

[0047] Firstly, a multi-objective intelligent optimization algorithm is used to search for the solution set of the robot mechanism topology and scale synchronization design model;

[0048] Then, the optimal solution of the Pareto solution set is determined based on game theory and comprehensive decision-making methods;

[0049] Finally, the optimal topology of the mechanism and its scale parameters are obtained.

[0050] The beneficial effects of the present invention are as follows:

[0051] The design method proposed in the present invention establishes an algebraic connection between the topology and performance of the mechanism, and realizes performance-oriented quantitative evaluation and selection of topology; the design method proposed in the present invention comprehensively considers the coupling influence of topology and scale on performance, and proposes a topology and scale simultaneous optimization design process, which solves the problem of separation between topology design and scale design. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a flow chart of the simultaneous optimization design of the robot mechanism topology and scale in the present invention;

[0053] Figure 2 It is the optimal solution set of the Pareto solution set of the multi-objective topology and scale synchronous optimization design in the present invention;

[0054] Figure 3 is the Pareto solution set for the topology and scale synchronization optimization of the symmetric [PP]S type parallel robot mechanism in the present invention;

[0055] Figure 4 It is the Pareto solution set of topology optimization of fully symmetric [PP]S type parallel mechanism under given two sets of scale parameters in the present invention;

[0056] Figure 5 It is the Pareto solution set for scale optimization of the two types of [PP]S parallel robot mechanisms, RRS-2RPRU and 3RPPU in the present invention. DETAILED DESCRIPTION

[0057] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and embodiments:

[0058] like Figures 1 to 5 As shown, a method for synchronous design of robot mechanism topology and scale includes the following steps:

[0059] ⅰ. Define topological parameters and establish the robot mechanism topological model based on continuous motion;

[0060] ⅱ. Based on the topological model, the scale parameter is introduced to obtain the motion model;

[0061] ⅲ. Construct the performance model of the organization;

[0062] iv. Determine the topological and scale variables to be optimized;

[0063] ⅴ. Establish a synchronous design model of robot mechanism topology and scale;

[0064] ⅵ. Search for solutions to the robot mechanism topology and scale synchronization design model;

[0065] ⅶ. Obtain the optimal topology and scale parameters of the mechanism.

[0066] Step i: Based on continuous motion, establish the topological model of the robot mechanism. The specific process is as follows:

[0067] First, determine the modeling type and choose either forward modeling or reverse modeling;

[0068] Then, forward modeling for several specific topologies is adopted;

[0069] Or use inverse modeling to build the mechanism topology for known desired motion;

[0070] Finally, the topological feature parameters are constructed.

[0071] The topological characteristic parameters include the number of branches, the type of branch motion joints, the order of branch motion joints, the assembly characteristics of the motion joints, and the driving scheme.

[0072] Step ii introduces scale parameters based on the topological model. The specific process is as follows:

[0073] First, the robot mechanism topology model is obtained;

[0074] Then, the scale parameter is introduced, and the robot mechanism topology model is considered to move from the initial state to any state;

[0075] Finally, the displacement model is obtained.

[0076] Step II also includes obtaining a velocity model and an acceleration model, and the specific process is as follows:

[0077] First, the first-order derivative of the displacement model is solved to obtain the velocity model, and the topological and scale parameters are transferred to the velocity model respectively;

[0078] Then, the second-order derivative of the displacement model is solved to obtain the acceleration model, and the topological and scale parameters are transferred to the acceleration model respectively.

[0079] Step iii: Construct the performance model of the organization. The specific process is as follows:

[0080] Firstly, the displacement model, velocity model and acceleration model containing topological parameters and scale parameters are obtained;

[0081] Then, a performance model containing topological parameters and scale parameters is constructed based on the displacement model, velocity model and acceleration model.

[0082] The performance model includes a kinematic model, a stiffness model and a dynamic model.

[0083] Step ⅳ determines the topology and scale variables to be optimized. The specific process is as follows:

[0084] First, the obtained displacement model contains topological parameters and scale parameters;

[0085] Then, based on the topological characteristic parameters, the topological and scale variables to be optimized can be determined.

[0086] Step V: Establish a synchronous design model of robot mechanism topology and scale. The specific process is as follows:

[0087] First, construct corresponding performance optimization indicators according to application requirements;

[0088] Then, the topological parameters and scale parameters to be optimized are defined as design variables to determine the feasible domain range;

[0089] Then, define the constraints of the optimization design, which include performance constraints and geometric constraints;

[0090] Finally, a synchronous design model of robot mechanism topology and scale is obtained.

[0091] Step VI searches for the solution set of the robot mechanism topology and scale synchronization design model. The specific process is as follows:

[0092] Firstly, a multi-objective intelligent optimization algorithm is used to search for the solution set of the robot mechanism topology and scale synchronization design model;

[0093] Then, the optimal solution of the Pareto solution set is determined based on game theory and comprehensive decision-making methods;

[0094] Finally, the optimal topology of the mechanism and its scale parameters are obtained.

[0095] Specifically, the performance constraint is a performance restriction condition that enables the mechanism to meet application requirements, such as a value range of the target performance.

[0096] The geometric constraints are geometric condition constraints that the mechanism components must satisfy during the prototype processing, such as the feasible domain of the scale parameter.

[0097] Specifically, for the forward modeling of several known topologies, the specific process is as follows:

[0098] First, the continuous motion of the mechanism is described using an algebraic format. This step requires that the continuous motion description mathematical tool used has a differentiable property.

[0099] Secondly, the topological parameters are defined based on the geometric features of the known topology. This step requires that the defined topological parameters have motion invariance, including but not limited to loop structure, joint type, order, etc.

[0100] Finally, the topological parameters are combined with the mechanism motion model to establish a topological model containing topological parameters.

[0101] Specifically, the reverse modeling of the mechanism topology is constructed for known desired motion. The specific process is as follows:

[0102] First, set the topology parameters and specify the parameter value range.

[0103] Secondly, a one-to-one mapping relationship between topological parameters and topological models is constructed.

[0104] Specifically, step i establishes a topological model of the robot mechanism based on continuous motion, and also includes establishing search conditions for topological parameters to determine whether the topological model corresponding to the topological parameters matches the expected motion. If so, the set of topological parameters is retained, otherwise it is discarded.

[0105] Specifically, step iii builds the performance model of the mechanism. The specific process is as follows:

[0106] Firstly, the reciprocal relationship between motion and force is used to construct the mechanism driving force and constraint force model.

[0107] Secondly, construct the Jacobian matrix and Hessian matrix of the mechanism. Since the velocity model and acceleration model in step ii contain topological parameters, the Jacobian matrix and Hessian matrix contain both topological parameters and scale parameters.

[0108] Finally, the static and dynamic models of the mechanism are established.

[0109] More preferably, for the statics model, the linear elastic deformation caused by the force on the mechanism is regarded as a small motion, and the mapping relationship between the force and deformation of the mechanism is established by Hooke's law.

[0110] Better yet, for the dynamic model, the velocities of all components in the mechanism are calculated, and the Hessian matrix is ​​obtained by differential operation of the velocity model to the acceleration model, and then the acceleration of all components is obtained. Combined with the force mapping models such as the inertia force and gravity of each component, dynamic modeling is performed using the principle of virtual work.

[0111] Yet another embodiment

[0112] Step 1: Topology Modeling

[0113] Topological modeling constructs a topological model of the robot mechanism based on continuous motion, including forward modeling for several specific topologies and inverse modeling of the mechanism topology with known expected motion.

[0114] Based on the modeling, the topological characteristic parameters of the mechanism are refined and the mechanism topological model M T The parameterization is described as

[0115]

[0116] The topological characteristic parameters T include but are not limited to the number of branches N, the type of branch motion joints, and the order of branch motion joints T. H , assembly features of motion joints T W And the drive scheme of the mechanism T A wait.

[0117] in, Characterizing topological characteristic parameters T and mechanism topological model M T There is a one-to-one mapping relationship.

[0118] Step 2: Motion Mapping

[0119] Introducing the scale parameter D L , the robot mechanism topology model involved in step one is regarded as a displacement model moving from an initial state to an arbitrary state.

[0120] Then, through the differential mapping relationship between displacement, velocity and acceleration, the first-order and second-order derivatives of the displacement model are solved respectively, and the topological and scale parameters are transferred to the velocity model respectively. Acceleration model In

[0121]

[0122] Step 3: Performance Modeling

[0123] The performance model of the mechanism is constructed using various levels of motion models containing both topological parameters and scale parameters. The performance model includes but is not limited to a kinematic model, a stiffness model and a dynamic model.

[0124] At this time, the kinematic model includes the topological parameters T and motion scale parameters D transmitted from the topological model. L .

[0125] The static stiffness model includes topological parameters T and motion scale parameters D L , cross-sectional dimension parameter D A .

[0126] The dynamic model includes topological parameters T and motion scale parameters D L , cross-sectional dimension parameter D A And the inertia parameter D M .

[0127]

[0128]

[0129]

[0130] Where M K 、M S 、M D They are kinematic, static and dynamic models respectively.

[0131] Step 4: Topology and scale parameter screening

[0132] The robot mechanism has many parameters and the model is huge. In order to simplify the model and improve the solution speed, the topological parameters and scale parameters to be optimized must be determined.

[0133]

[0134]

[0135] Where V t and V d They are the topological parameter and scale parameter sets respectively.

[0136] V t Including but not limited to the number of branches N, the type and sequence of branch motion joints T H , assembly features of motion joints T W And the drive scheme of the mechanism T A wait.

[0137] V d Including but not limited to the motion scale parameter D L , cross-sectional dimension parameter D A And the inertia parameter D M .

[0138] Step 5: Topology and scale synchronization optimization model construction

[0139] Using equations (3)-(7) to establish a robot mechanism topology and scale synchronization design model

[0140]

[0141] Among them, V t and V dare the sets of all scale parameters and topological parameters to be optimized. U and v L are the upper and lower bounds of the scale parameter, respectively.

[0142] Since the feasible domains of scale and topological parameters are continuous and discrete respectively, scale parameters and topological parameters can be regarded as continuous and discrete variables in the optimization design problem. j (V) is the objective function. C f and C v are performance constraints and geometric constraints respectively.

[0143] Performance constraints are performance restrictions that enable an organization to meet application requirements, including but not limited to the value range of the target performance. j U and f j L are the upper and lower critical values ​​of the target performance, respectively.

[0144] Geometric constraints are geometric constraints that must be met by the mechanical components during the prototype processing, including but not limited to the feasible domain of scale parameters.

[0145] Step 6: Optimize design and make optimal solution decisions

[0146] A multi-objective optimization algorithm is used to search the solution set of the topology and scale simultaneous optimization design model to obtain the optimal solution.

[0147] For the multi-objective optimization design of multiple performance indicators, the present invention requires the construction of a Pareto optimal solution set {V opt},like Figure 2 . The optimal topology and scale parameters of the organization are selected using a multi-objective decision-making method.

[0148] Yet another embodiment

[0149] This embodiment uses finite-instantaneous screw (FIS) as a mathematical tool for simultaneous optimization of topology and scale. (For a detailed introduction to the expression and operation rules of finite-instantaneous screw, please refer to: Sun T, Yang SF, Lian BB. Finite and instantaneous screw theory in robotic mechanism, Springer, 2020)

[0150] One translation and two rotation (1T2R) parallel mechanisms have important applications in mechanical processing, collaborative equipment, medical rehabilitation, etc. This embodiment uses a type of symmetrical 1T2R parallel mechanism with instantaneous change of motion axis as the topological and dimensional synchronization design object. The characteristics of this type of mechanism are that the component branches contain planar translation ([PP]) and centering spatial rotation (S) motion, as shown in Table 1. This embodiment abbreviates this type of 1T2R parallel mechanism as a [PP]S type parallel mechanism.

[0151]

[0152] Table 1 [PP]S parallel mechanism branch chain table

[0153] Step 1: Topology Modeling

[0154] The topological model of the symmetric [PP]S parallel mechanism is established by using finite screws, and its mathematical expression is as follows:

[0155] S f,M =S f,L,N ∩…∩S f,L,2 ∩S f,L,1 (9)

[0156] In the formula, N is the number of branches, and in this case N = 3. f,M To characterize the finite spinor of the end motion of the symmetric [PP]S type parallel mechanism, '∩' is the intersection operation of the finite spinor.

[0157] The branch chain i of this type of mechanism is composed of 5 single-degree-of-freedom motion joints, which can be described by applying finite rotation:

[0158] S f,L,i =S f,5,i Δ…ΔS f,2,i ΔS f,1,i (10)

[0159] In the formula, S f,k,i is the finite rotation of the kth kinematic joint of branch chain i

[0160]

[0161] In the formula, θ k,i and t k,i are the rotation and translation variables of the kth single-degree-of-freedom joint of branch chain i, respectively. k ∈{0,1} is used to characterize the type of motion joint: when h k When h is 1, it indicates that the motion joint is a revolute joint; when h k When it is 0, it indicates that the motion joint is a mobile joint.

[0162] Since the [PP]S parallel mechanism in this embodiment has a symmetrical structure, at least two branches have the same structure, which are assumed to be branches 2 and 3. In addition, the last two motion joints of the [PP]S branch are R pairs with axes intersecting at one point, so only the topological parameters need to be set to

[0163]

[0164] Among them, h k,i is the type topological parameter of the kth kinematic joint of the ith branch, when h k,i When w = 1, it indicates that the joint is a rotational joint, otherwise it is a translational joint. i is the relative position relationship between its axis and the last two joints when the third kinematic joint of branch chain i is a revolute joint. i =0,

[0165] r 3,i =r 4,i =r 5,i

[0166] Characterizes that the last three rotational joint axes of branch chain i intersect at one point, otherwise they do not intersect. i Represents the order of the driving joints of the i-th branch chain. The driving joints must satisfy

[0167]

[0168] In the formula, Lock the motion of the drive joint for branch chain i.

[0169] Step 2: Motion Mapping

[0170] For the above-mentioned symmetrical [PP]S parallel robot mechanism, a global coordinate system O-xyz is established with the center point of the moving platform in the initial position as the coordinate origin O, where the x-axis points from point O to the connection point between branch chain 1 and the moving platform, the z-axis is perpendicular to the moving platform, and the y-axis is determined by the right-hand rule.

[0171] Taking any configuration as the initial configuration, a displacement model of the mechanism with topological and scale parameters is established.

[0172]

[0173] Take the first-order derivative of both sides of equation (18) with respect to time, and establish the velocity and acceleration mapping model of the dynamic platform and branch chain of the mechanism, as follows:

[0174]

[0175]

[0176] In the formula, S t,M and St,L,i is the instantaneous motion spiral of the end of the mechanism and branch i under any configuration

[0177]

[0178] In the formula, S t,k,i is the instantaneous motion spiral of the kth single-degree-of-freedom motion joint of branch chain i

[0179]

[0180] In the formula, and are the rotation and translation speeds of the kth single-degree-of-freedom joint of branch chain i, respectively. k,i The meaning of is the same as that of formula (13).

[0181] Step 3: Performance Modeling

[0182] Using the reciprocal relationship between motion helices and force helices, the constraint force screw of the [PP]S type parallel mechanism satisfies the following formula:

[0183]

[0184] Solving the constraint spiral S using the singular value decomposition method w,L,i Based on this, the kinematic, static and dynamic models of the mechanism are established.

[0185]

[0186]

[0187]

[0188] Step 4: Topology and scale parameter screening

[0189] In this embodiment, the joint type, sequence, drive scheme, length and cross-section of the rod are selected as design variables, see Table 2.

[0190]

[0191] Table 2 Design variables for topology and scale synchronization design of symmetric three-branch [PP]S parallel mechanism

[0192] Step 5: Topology and scale simultaneous optimization design

[0193] Constructing a synchronous optimization design model for topological and dimensional parameters of symmetric [PP]S parallel mechanisms

[0194]

[0195] In the formula, {S f,M}r is the working space of the mechanism.

[0196]

[0197] θ x and θ y is the end attitude angle of the mechanism, and J is the Jacobian matrix of the mechanism. In this embodiment, f j (V) are the evaluation indicators of motion virtual power transfer efficiency, instantaneous deformation energy and dynamic stability.

[0198] Step 6: Optimal parameter decision

[0199] This embodiment uses a multi-objective particle swarm optimization algorithm to search for a solution set of the optimization model and obtain a Pareto solution set of the optimization model, such as Figure 3 shown.

[0200] In this embodiment, a total of 63 Pareto solutions are obtained, involving 17 different symmetric [PP]S parallel mechanism topologies. Sg (g=1,…,4) represents four different topologies and their matching scales, which can be used to construct corresponding organizations. The optimization target weights are solved by entropy weight method, see Table 3.

[0201]

[0202] Table 3 Index weight table

[0203] With the help of TOPSIS decision-making method, the overall solution set is evaluated with the closeness of positive and negative ideal solutions as the index, and the optimal solution is O S The topology, scale and performance information of the representation are shown in Table 4.

[0204]

[0205] Table 4 Optimal symmetric three-branched [PP]S parallel mechanism and its performance

[0206] In order to illustrate the beneficial technical effects of the design method of the present invention, this embodiment will respectively carry out the topological design and the scale design of the symmetrical [PP]S type parallel mechanism, and compare them with the synchronous design results. The two sets of scale parameters are given in Table 5.

[0207]

[0208] Table 5 Dimensional parameters of two sets of symmetrical three-branched [PP]S parallel mechanisms

[0209] Under these two sets of scale parameters, with the same performance index as the optimization target, the topological design results of the [PP]S type parallel mechanism are shown in Figure 4It can be seen that the optimal solution O under the Dim-1 scale T1 With O S1 Coincidence, optimal solution under Dim-2 scale O T2 Performance is worse than O S2 Similarly, given two symmetric [PP]S-type mechanism topologies RPS-2RPRU and 3RPPU, the topology parameters are shown in Table 6.

[0210]

[0211] Table 6 Topological parameters of two groups of symmetrical three-branched [PP]S parallel mechanisms

[0212] Taking the same performance index as the optimization target, the scale optimization design results of RPS-2RPRU and 3RPPU are shown in Figure 5 , Figure 5 The scale design results of (a) RRS-2RPRU and (b) 3RPPU mechanisms, where the optimal scale O of the RRS-2RPRU mechanism is D1 With O S3 Overlap, 3RPPU mechanism O D2 Inferior to O S4 Therefore, compared with independent topology design and scale design, the simultaneous optimization design of topology and scale of [PP]S-type parallel mechanisms can obtain the global optimal solution.

[0213] The design method proposed in the present invention establishes an algebraic connection between the topology and performance of the mechanism, and realizes performance-oriented quantitative evaluation and selection of topology; the design method proposed in the present invention comprehensively considers the coupling influence of topology and scale on performance, and proposes a topology and scale simultaneous optimization design process, which solves the problem of separation between topology design and scale design.

Claims

1. A method for simultaneous design of robot mechanism topology and scale, Features: The following steps are involved: (i) define topological parameters and establish a topological model of the robot mechanism based on continuous motion; (ii) Based on the topological model, the scale parameter is introduced to obtain the motion model; It introduces the scale parameter, and the specific process is as follows: First, the robot mechanism topology model is obtained; Then, the scale parameter is introduced, and the robot mechanism topology model is considered to move from the initial state to any state; Finally, the displacement model is obtained; Topology Modeling The topological model of the symmetric [PP]S parallel mechanism is established by using finite screws, and its mathematical expression is as follows: S f,M =S f,L,N ∩…∩S f,L,2 ∩S f,L,1 (9) In the formula, N is the number of branches, in this case N = 3; S f,M To characterize the finite spinor of the end motion of the symmetric [PP]S type parallel mechanism, '∩' is the intersection operation of the finite spinor; The branch chain i of this type of mechanism is composed of 5 single-degree-of-freedom motion joints, which can be described by applying finite rotation: S f,L,i =S f,5,i …S f,2,i S f,1,i (10) In the formula, S f,k,i is the finite rotation of the kth kinematic joint of branch chain i In the formula, θ k,i and t k,i are the rotation and translation variables of the kth single-degree-of-freedom joint of branch chain i; h k ∈{0,1} is used to characterize the type of motion joint: when h k When h is 1, it indicates that the motion joint is a revolute joint; when h k When it is 0, it indicates that the motion joint is a mobile joint; (iii) constructing a performance model of the organization; (iv) determining the topological and scale variables to be optimized; (v) Establish a model for synchronous design of robot mechanism topology and scale; (vi) Searching for solutions to the simultaneous design model of robot mechanism topology and scale; (ⅶ) Obtain the optimal topology and scale parameters of the mechanism.

2. A method for synchronously designing robot mechanism topology and scale according to claim 1, Features: Step (i) Based on continuous motion, a topological model of the robot mechanism is established. The specific process is as follows: First, determine the modeling type and choose either forward modeling or reverse modeling; Then, forward modeling for several specific topologies is adopted; Or use inverse modeling to build the mechanism topology for known desired motion; Finally, the topological feature parameters are constructed.

3. A method for synchronously designing robot mechanism topology and scale according to claim 2, Features: The topological characteristic parameters include the number of branches, the type of branch motion joints, the order of branch motion joints, the assembly characteristics of the motion joints, and the driving scheme.

4. A method for synchronously designing robot mechanism topology and scale according to claim 1, Features: Step (ii) also includes obtaining a velocity model and an acceleration model, and the specific process is as follows: First, the first-order derivative of the displacement model is solved to obtain the velocity model, and the topological and scale parameters are transferred to the velocity model respectively; Then, the second-order derivative of the displacement model is solved to obtain the acceleration model, and the topological and scale parameters are transferred to the acceleration model respectively.

5. A method for synchronously designing robot mechanism topology and scale according to claim 4, Features: Step (iii) constructs the performance model of the mechanism. The specific process is as follows: Firstly, the displacement model, velocity model and acceleration model containing topological parameters and scale parameters are obtained; Then, a performance model containing topological parameters and scale parameters is constructed based on the displacement model, velocity model and acceleration model.

6. A method for synchronously designing robot mechanism topology and scale according to claim 5, Features: The performance model includes a kinematic model, a stiffness model and a dynamic model.

7. A method for synchronously designing robot mechanism topology and scale according to claim 1, Features: Step (iv) determines the topology and scale variables to be optimized. The specific process is as follows: First, the obtained displacement model contains topological parameters and scale parameters; Then, based on the topological characteristic parameters, the topological and scale variables to be optimized can be determined.

8. A method for synchronously designing robot mechanism topology and scale according to claim 1, Features: Step (v) establishes a robot mechanism topology and scale synchronous design model. The specific process is as follows: First, construct corresponding performance optimization indicators according to application requirements; Then, the topological parameters and scale parameters to be optimized are defined as design variables to determine the feasible domain range; Then, define the constraints of the optimization design, which include performance constraints and geometric constraints; Finally, a synchronous design model of robot mechanism topology and scale is obtained.

9. A method for synchronously designing robot mechanism topology and scale according to claim 1, Features: Step (vi) searches for a solution set of the robot mechanism topology and scale synchronization design model. The specific process is as follows: Firstly, a multi-objective intelligent optimization algorithm is used to search for the solution set of the robot mechanism topology and scale synchronization design model; Then, the optimal solution of the Pareto solution set is determined based on game theory and comprehensive decision-making methods; finally, the optimal topology of the organization and its scale parameters are obtained.

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