A spatial truss assembly sequence planning method based on assembly influence comprehensive index

Abstract

The embodiment of the present application provides a kind of space truss assembly sequence planning method based on assembly influence comprehensive index, comprising: according to the geometric characteristics of space truss and its component parts, build space truss assembly task characterization model;According to the space truss assembly task characterization model, build space truss assembly constraint condition;According to space truss structure and robot assembly execution energy consumption, build assembly influence comprehensive index;According to space truss assembly task characterization model, space truss assembly constraint condition and assembly influence comprehensive index, using A* algorithm obtains space truss assembly sequence.According to the technical scheme provided by the embodiment of the present application, the space truss assembly sequence with more optimal comprehensive index such as assembly stability and robot energy consumption can be obtained, so that the robot can better realize space truss assembly.

Description

[Technical Field]

[0001] This invention relates to a spatial truss assembly sequence planning method based on a comprehensive index of assembly impact, belonging to the field of spatial truss assembly technology. [Background Technology]

[0002] With the development of aerospace technology and the deepening of space exploration, the demand for the construction of important facilities based on space trusses, such as space stations, solar arrays, and large-aperture telescopes, is becoming increasingly urgent. Due to limitations such as structural weight, engine specific impulse, and fuel capacity, launch vehicles need to transport large or massive space facilities to the orbital environment in batches and assemble them in orbit. Currently, most space trusses are assembled manually by astronauts outside the cabin, but this method is highly dangerous and inefficient. Therefore, the future development direction of space truss assembly technology is to use robots for autonomous assembly, and assembly sequence planning is key to achieving autonomous and automated assembly. The significance of assembly sequence planning lies in finding the optimal assembly sequence while considering various assembly process constraints. Based on this sequence, robots can be controlled to grasp and insert truss components, thereby improving assembly efficiency and reducing assembly costs.

[0003] Traditional spatial truss assembly sequence planning methods typically focus more on motion paths and energy consumption when constructing evaluation indicators, giving less consideration to the stability of spatial truss assembly. However, in actual assembly processes, the stability of spatial truss assembly also largely determines the success rate of assembly. Therefore, how to incorporate the impact of assembly stability into the considerations of assembly sequence planning is of great research significance for controlling robots to reliably assemble spatial trusses. [Summary of the Invention]

[0004] In view of this, the present invention provides a spatial truss assembly sequence planning method based on a comprehensive assembly impact index. By constructing a spatial truss assembly task representation model and spatial truss assembly constraints, designing a comprehensive assembly impact index, and then using the A* algorithm, the assembly sequence of the spatial truss is obtained, thereby driving the robot to achieve autonomous assembly of the spatial truss.

[0005] This invention provides a spatial truss assembly sequence planning method based on a comprehensive assembly impact index, comprising:

[0006] Based on the geometric characteristics of the space truss and its components, a space truss assembly task representation model is constructed.

[0007] Based on the spatial truss assembly task representation model, construct the spatial truss assembly constraints.

[0008] Based on the spatial truss structure and the energy consumption of robot assembly execution, a comprehensive index of assembly impact is constructed;

[0009] Based on the spatial truss assembly task characterization model, spatial truss assembly constraints, and comprehensive assembly impact index, the A* algorithm is used to obtain the spatial truss assembly sequence.

[0010] In the above method, the step of constructing a spatial truss assembly task representation model based on the geometric characteristics of the spatial truss and its constituent components includes:

[0011] Based on the geometric properties of the space truss and its components, for a space truss composed of r space truss components (hereinafter referred to as components, each containing m connectors and h trusses, each connector having a interfaces and each truss having b interfaces, and a > b ≥ 2), a space truss assembly task representation model of the following form is defined:

[0012] r = m + h

[0013] Q = [q1, q2, ..., q m ,q m+1 ,q m+2 ,...,q r ]

[0014]

[0015]

[0016]

[0017] W i =(w i1 ,w i2 ,...,w ia )

[0018] S = [p1, p2, ..., p r ]

[0019] Where Q represents the collection of components of the space truss, q1~q m Indicates connector, q m+1 ~q r c(i,j) represents the truss; c(i,j) represents component q. i With q j The connection relationship between them, c(i,j)=1 indicates that component q i q j Adjacent components; C represents the connection matrix of the space truss components, c ij =c(i,j) represents the element in the i-th row and j-th column of matrix C; p i Indicates component q i Assembly status; Wi Indicates component q i The assembly state of adjacent components, w i1 ~w ia Indicates component q i The assembly status of a adjacent component is given, where 0 represents the absence of the adjacent component, 1 represents the unassembled adjacent component, and 2 represents the assembled adjacent component (since the truss only has b interfaces, when i > m, w). ib+1 ~w ia =0); S represents the overall state of the spatial truss assembly task at a specified time.

[0020] In the above method, the step of constructing truss assembly constraints based on the space truss assembly task representation model includes:

[0021] Define component q i Spatial truss component connection constraint function K i for:

[0022] K i =(1-p i )h i

[0023]

[0024] Among them, h i Indicates component q i The number of adjacent components already assembled, w i1 ~w ia Consistent with the above; (1-p i ) = 0 indicates that component q i Already assembled, (1-p i ) = 1 indicates component q i Not assembled; K i ≠0 indicates component q i The number of assembled adjacent parts is not zero, but the assembly is not complete;

[0025] Based on the above-mentioned space truss component connection constraint function K i The connection constraints for the space truss components are as follows:

[0026] K i ≠0

[0027] Define assembly truss q i The spatial truss component assembly sequence constraint function L when (i>m) i for:

[0028] L i =(w i1 -1)(w i2 -1)...(w ib-1), (i>m)

[0029] Among them, w i1 ~w ib Consistent with the above; L i =1 indicates that the truss q i Both adjacent components have been assembled, L i ≠1 indicates that the truss q i At least one of the two adjacent components is not assembled;

[0030] Based on the above-mentioned space truss component assembly sequence constraint function L i The assembly sequence constraint for the space truss components is as follows:

[0031] L i ≠1;

[0032] In the above method, the construction of a comprehensive assembly impact index based on the space truss structure and the energy consumption of robot assembly execution includes:

[0033] Based on the structure of the space truss to be assembled, the change in the position of the space truss's center of mass, F, is defined as:

[0034]

[0035] Among them, (x i ,y i ,z i ) indicates that in the assembly of component q i The coordinates of the centroid of the spacetime truss;

[0036] Define the number of unconnected interfaces E of the space truss as:

[0037]

[0038] Where, p i Consistent with that described in claim 2, u i Indicates component q i The number of included interfaces is defined as follows:

[0039]

[0040] The interference degree G of the assembled component on the component to be assembled is defined as:

[0041]

[0042] Among them, v i Indicates component q i Installation sequence number, d i This indicates that the robot's end effector starts from its initial position P. e0 Move to component q iPlacement location Grab it and move it to the assembly position. The length of the motion path used for assembly;

[0043] Based on the change in the centroid position of the space truss (F), the number of unconnected interfaces of the space truss (E), and the interference degree (G) of the assembled components on the components to be assembled, the comprehensive assembly impact index is designed as follows:

[0044] f indicator =α1F + α2E + α3G

[0045] Wherein, α1 represents the weight of the change in the position of the centroid of the space truss F, α2 represents the weight of the number of unconnected interfaces of the space truss E, and α3 represents the weight of the interference degree G between the assembled components and the components to be assembled. The values ​​of these three weights can be given by human experience.

[0046] In the above method, the step of obtaining the space truss assembly sequence using the A* algorithm based on the space truss assembly task representation model, space truss assembly constraints, and comprehensive assembly impact index includes:

[0047] Based on the A* algorithm, the spatial truss assembly sequence is solved according to the following procedure:

[0048] Step 1: Let the current time be the initial time t = 0, and specify the initial component q. i and its assembly position robot end effector initial position P e0 The initial state of the space truss assembly task is S0, and the target state of the space truss assembly task is S... end ;

[0049] Step 2: Calculate the overall state S of the space truss assembly task at the current moment, the connection matrix C of the space truss components, and filter those that satisfy the connection constraints K of the space truss components. i The next state S′ that is not 0 is obtained, and the set of expandable states A at the current time is obtained, which represents the set of all possible installation states of space truss components after installing a component at the current time.

[0050] Step 3: Based on the current set of expandable states A, select the state L that satisfies the assembly sequence constraint condition of the space truss components. i The next state S″ ≠ 1 is used to obtain the set of expandable and feasible states B that satisfy the assembly sequence constraints of the space truss components. This set represents the set of all space truss component installation states that may occur after installing a component at the current moment and satisfy the assembly sequence constraints of the space truss components.

[0051] Step 4: Traverse all states in the set of extensible feasible states B, and calculate the comprehensive assembly impact index f for each state.indicator Take the state corresponding to its minimum value as the optimal expandable state S at the current moment. b " est Let the current state S = S b " est and S b " est Add to the tail of the list of state changes;

[0052] Step 5: If the current state S = S end If yes, proceed to the next step; otherwise, set t = t + 1 and return to step 2.

[0053] Step 6: Subtract the states of any two adjacent moments in the state change list List to obtain the state change amount ΔS at that moment. Extract the position index of the non-zero value in each ΔS to obtain the spatial truss assembly sequence O. [Attached Image Description]

[0054] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0055] Figure 1 This is an operation flowchart provided in the embodiments of the present invention;

[0056] Figure 2 This is a schematic diagram of the space truss structure in an embodiment of the present invention;

[0057] Figure 3 This is a comparison chart of the index costs of the planning sequence and the comparison sequence obtained using the embodiments of the present invention.

Detailed Implementation Methods

[0058] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0059] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0060] This invention provides a spatial truss assembly sequence planning method based on a comprehensive assembly impact index. Please refer to [link / reference]. Figure 1 The method includes the following steps:

[0061] Step 101: Based on the geometric characteristics of the space truss and its components, construct a space truss assembly task representation model.

[0062] Based on the geometric properties of the space truss and its components, for a space truss composed of r space truss components (hereinafter referred to as components, each containing m connectors and h trusses, each connector having a interfaces and each truss having b interfaces, and a > b ≥ 2), the set of space truss components is defined as:

[0063] Q = [q1, q2, ..., q m ,q m+1 ,q m+2 ,...,q r ]

[0064] Where q1~q m Indicates connector, q m+1 ~q r Indicates a truss.

[0065] Based on the characteristics of space truss structures, the component q of a space truss is defined. i With q j The connection relationship between them is as follows:

[0066]

[0067] Define a component q that satisfies c(i,j)=1. i With q j They are adjacent components.

[0068] The connection matrix of the components of the space truss is as follows:

[0069]

[0070] In the formula, c ij =c(i,j) is the element in the i-th row and j-th column of matrix C.

[0071] Define the components q of the space truss i The assembly status is as follows:

[0072]

[0073] During the assembly process, to confirm the composition of the space truss unit q i Whether assembly conditions are met requires understanding the assembly status of its adjacent components and defining the spatial truss unit component q. i The assembly status of adjacent components is as follows:

[0074] W i =(w i1 ,w i2 ,...,wia )

[0075] In the formula, w i1 ~w ia Indicates component q i The assembly status of a adjacent component is given, where 0 represents the absence of the adjacent component, 1 represents the unassembled adjacent component, and 2 represents the assembled adjacent component (since the truss only has b interfaces, when i > m, w). ib+1 ~w ia =0).

[0076] To describe the assembly state of all spatial truss components during the assembly process, the spatial truss assembly task state at a specified moment is defined as follows:

[0077] S = [p1, p2, ..., p r ]

[0078] Specifically, the schematic diagram of the space truss structure in the embodiment of the present invention is as follows: Figure 2 As shown, the space truss is a cube structure with a side length of 0.2m, containing 8 connectors and 12 trusses. Each connector has 3 interfaces and each truss has 2 interfaces. Therefore, m = 8, h = 12, r = 20, a = 3, and b = 2.

[0079] Step 102: Based on the spatial truss assembly task representation model, construct the spatial truss assembly constraints.

[0080] Based on component q i The assembly state of adjacent components W i The component q can be obtained. i The number of adjacent components that have been assembled is expressed as:

[0081]

[0082] Considering that when planning the assembly sequence, any selectable component to be assembled must satisfy the following conditions: the component is not currently assembled, and it has at least one adjacent component that has been assembled, therefore component q is defined. i Spatial truss component connection constraint function K i for:

[0083] K i =(1-p i )h i

[0084] Among them, (1-p i ) = 0 indicates that component q i Already assembled, (1-p i ) = 1 indicates component q i Not assembled; K i ≠0 indicates component qi The number of assembled adjacent parts is not zero, but part q i It is not assembled itself; therefore, the connection constraints of the space truss components are taken as follows:

[0085] K i ≠0

[0086] Due to the interface characteristics between the connectors and the gantry, the robot's end effector cannot simultaneously perform assembly operations with the connectors already assembled at both ends of the gantry after grasping it; that is, it cannot perform assembly operations on the gantry q. i When (i>m), the stringer q is required. i At least one of two adjacent components is not assembled, therefore the assembly strut q is defined. i The spatial truss component assembly sequence constraint function L when (i>m) i for:

[0087] L i =(w i1 -1)(w i2 -1)...(w ib -1), (i>m)

[0088] Among them, L i =1 indicates that the truss q i Both adjacent components have been assembled, L i ≠1 indicates that the truss q i Since at least one of two adjacent components is not assembled, the assembly sequence constraint for the space truss components is as follows:

[0089] L i ≠1.

[0090] Step 103: Based on the spatial truss structure and the energy consumption of robot assembly execution, construct a comprehensive index of assembly impact.

[0091] Considering the stability of the space truss during assembly, and based on the structure of the space truss to be assembled, the change in the position of the space truss's center of mass, F, is defined as:

[0092]

[0093] Among them, (x i ,y i ,z i ) indicates that in the assembly of component q i The centroid coordinates of the space-time truss; this index assesses the stability of the assembly process by evaluating the change in the centroid position during the assembly of the space truss.

[0094] Secondly, considering that assembling components with more interfaces first, followed by components with fewer interfaces, is beneficial for maintaining the stability of the space truss, and that the number of connector interfaces is greater than the number of truss interfaces (i.e., a > b), the number of unconnected interfaces E of the space truss is defined as follows to encourage the robot to prioritize assembling connectors:

[0095]

[0096] Among them, u i Indicates component q i The number of included interfaces is defined as follows:

[0097]

[0098] Then, considering the impact of different assembly sequences of components on robot energy consumption, the interference degree G of the assembled components on the currently assembled components is defined as:

[0099]

[0100] Among them, v i Indicates component q i Installation sequence number, d i This indicates that the robot's end effector starts from its initial position P. e0 Move to component q i Placement location Grab it and move it to the assembly position. The length of the motion path used for assembly.

[0101] Based on the change in the centroid position of the space truss (F), the number of unconnected interfaces of the space truss (E), and the interference degree (G) of the assembled components on the components to be assembled, the comprehensive assembly impact index is designed as follows:

[0102] f indicator =α1F + α2E + α3G

[0103] Wherein, α1 represents the weight of the change in the centroid position F of the spatial truss, α2 represents the weight of the number of unconnected interfaces E of the spatial truss, and α3 represents the weight of the interference degree G of the assembled components to be assembled components. The values ​​of these three weights can be given by human experience. Specifically, in this embodiment, α1 = 1, α2 = 0.05, and α3 = 0.05.

[0104] Step 104: Based on the spatial truss assembly task representation model, spatial truss assembly constraints, and comprehensive assembly impact index, the A* algorithm is used to obtain the spatial truss assembly sequence.

[0105] Based on the A* algorithm, the spatial truss assembly sequence is solved according to the following procedure:

[0106] Step 1: Let the current time be the initial time t = 0, and specify the initial component q. i and its assembly position robot end effector initial position P e0 Initial state of the space truss assembly task (S0); Target state of the space truss assembly task (S) end ;

[0107] Step 2: Calculate the overall state S of the space truss assembly task at the current moment, the connection matrix C of the space truss components, and filter those that satisfy the connection constraints K of the space truss components. i The next state S′ that is not 0 is obtained, and the set of expandable states A at the current time is obtained, which represents the set of all possible installation states of space truss components after installing a component at the current time.

[0108] Step 3: Based on the current set of expandable states A, select the state L that satisfies the assembly sequence constraint condition of the space truss components. i The next state S″ ≠ 1 is used to obtain the set of expandable and feasible states B that satisfy the assembly sequence constraints of the space truss components. This set represents the set of all space truss component installation states that may occur after installing a component at the current moment and satisfy the assembly sequence constraints of the space truss components.

[0109] Step 4: Traverse all states in the set of extensible feasible states B, and calculate the comprehensive assembly impact index f for each state. indicator Take the state corresponding to its minimum value as the optimal expandable state S at the current moment. b " est Let the current state S = S b " est and S b " est Add to the tail of the list of state changes;

[0110] Step 5: If the current state S = S end If yes, proceed to the next step; otherwise, set t = t + 1 and return to step 2.

[0111] Step 6: Subtract the states of any two adjacent moments in the state change list List to obtain the state change amount ΔS at that moment. Extract the position index of the non-zero value in each ΔS to obtain the spatial truss assembly sequence O.

[0112] Specifically, in this embodiment, the initial component q is taken. i for Figure 2 Let the component numbered 1 (i.e., q1) be arranged in the following position: for:

[0113]

[0114] Let the initial position of the robot's end effector be P. e0 for:

[0115] P e0 =[0,-0.4,0.65]

[0116] Let the overall state S0 of the initial space truss assembly task be:

[0117] S0=[1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]

[0118] Let the target state of the space truss assembly task be S. end for:

[0119] S end =[1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1]

[0120] Based on the method provided in this embodiment, for Figure 2 An assembly sequence planning simulation experiment was conducted on the spatial truss shown, and the assembly sequence O of the spatial truss was obtained by solving the problem:

[0121] O=[0,11,3,15,7,19,12,4,18,6,14,10,2,17,9,16,5,13,8,1]

[0122] To illustrate the effectiveness of the planning results in this embodiment, the manual assembly sequence O′ is used as a comparison, and its value is:

[0123] O′=[0,11,3,10,2,15,7,14,18,6,9,17,5,13,19,16,8,1,12,4]

[0124] Plot a comparison graph showing the overall assembly impact index of the two assembly sequences as the number of assembled parts increases, as shown above. Figure 3 As shown, it can be seen that as the number of assembled parts increases, the comprehensive value of the assembly impact index of the planning sequence obtained by this embodiment is always lower than that of the manual assembly sequence. That is, it has significant advantages in comprehensive performance in terms of assembly stability and robot energy consumption, which verifies the effectiveness of the method provided in this embodiment.

[0125] The technical solutions of the embodiments of the present invention have the following beneficial effects:

[0126] Based on the geometric characteristics of the space truss and its components, a space truss assembly task representation model was constructed. On this basis, considering the executability of the assembly task, space truss assembly constraints were constructed. Considering the space truss structure and the energy consumption of robot assembly execution, a comprehensive assembly impact index was constructed. Then, based on the space truss assembly task representation model, space truss assembly constraints, and comprehensive assembly impact index, the A* algorithm was used to solve for the space truss assembly sequence. The obtained assembly sequence demonstrates superior overall performance in terms of assembly stability and robot energy consumption compared to the assembly sequence obtained without this method.

[0127] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0128] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A spatial truss assembly sequence planning method based on a comprehensive assembly impact index, characterized in that, The method includes: Based on the geometric characteristics of the space truss and its components, a space truss assembly task representation model is constructed. Based on the spatial truss assembly task representation model, construct the spatial truss assembly constraints. Based on the spatial truss structure and the energy consumption of robot assembly execution, a comprehensive index of assembly impact is constructed; Based on the spatial truss assembly task characterization model, spatial truss assembly constraints, and comprehensive assembly impact index, the A* algorithm is used to obtain the spatial truss assembly sequence. The comprehensive assembly impact index, constructed based on the space truss structure and robot assembly execution energy consumption, includes: Based on the structure of the space truss to be assembled, define the change in the position of the space truss's center of mass. for: in, Indicates the assembly of components The coordinates of the centroid of the spacetime truss; Define the number of unconnected interfaces of the space truss. for: in, Indicates components The assembly state, Indicates components The number of included interfaces is defined as follows: ； Define the degree of interference of the assembled component to the component to be assembled. for: in, Indicates components Installation sequence number, This indicates that the robot's end effector has started from its initial position. Move to component Placement location And then grab it and move it to the assembly position. The length of the motion path used for assembly; Based on the change in the position of the center of mass of the space truss Number of unconnected interfaces of space trusses The degree of interference of the assembled parts to the parts to be assembled. The comprehensive impact index of design assembly is as follows: in, Indicates the change in the position of the center of mass of the space truss The weight, Indicates the number of unconnected interfaces of the space truss. The weight, This indicates the degree of interference between the assembled component and the component to be assembled. The weights of these three weights can be determined through human experience.

2. The method according to claim 1, characterized in that, The construction of a spatial truss assembly task representation model based on the geometric characteristics of the spatial truss and its components includes: Based on the geometric properties of the space truss and its components, let the space truss be composed of... It is composed of several spatial truss components, where the spatial truss components are referred to as components, and include... One connector and There are trusses, and each connector has _____. Each strut has an interface. One interface, and Define a spatial truss assembly task representation model in the following form: in, It represents the collection of components that make up a space truss. Indicates connector, Indicates a truss; Indicates components and The connection between them Indicates components , The components are adjacent to each other; This represents the connection matrix of the components of a space truss. For matrix No. Line number Column elements; Indicates components The assembly state; Indicates components The assembly status of adjacent components, Indicates components of The assembly status of adjacent components includes: 0 represents that the adjacent component does not exist, 1 represents that the adjacent component is not assembled, and 2 represents that the adjacent component is assembled. Since the truss only has... One interface, therefore when hour ; It indicates the overall state of the space truss assembly task at a specified moment.

3. The method according to claim 1, characterized in that, Based on the spatial truss assembly task representation model, the spatial truss assembly constraint conditions are constructed, including: Define components Spatial truss component connection constraint function for: in, Indicates components The number of adjacent components that have been assembled. Indicates components of The assembly status of adjacent components; Indicates components Already assembled. Indicates components Not assembled; Indicates components The number of assembled adjacent parts is not zero, but the assembly is not complete; Based on the above-mentioned space truss component connection constraint function The connection constraints for the space truss components are as follows: ； Define assembly truss ( Spatial truss component assembly sequence constraint function for: in, Indicates truss of The assembly status of adjacent components; Indicates truss Both adjacent components have been assembled. Indicates truss At least one of the two adjacent components is not assembled; Based on the above-mentioned space truss component assembly sequence constraint function The assembly sequence constraint for the space truss components is as follows: 。 4. The method according to claim 1, characterized in that, Based on the spatial truss assembly task representation model, spatial truss assembly constraints, and comprehensive assembly impact index, the A* algorithm is used to obtain the spatial truss assembly sequence, including: Based on the A* algorithm, the spatial truss assembly sequence is solved according to the following procedure: Step 1: Record the current time as the initial time. Specify initial components and its assembly position Initial position of robot end effector The overall state of the space truss assembly task at the initial moment Space truss assembly task target status ; Step 2: Calculate the overall state of the space truss assembly task at the current moment. Space truss component connection matrix Screening for components that meet the connection constraints of the space truss. The state of the next moment Obtain the set of expandable states at the current moment. It represents the set of all possible installation states of spatial truss components after a component is installed at the current moment; Step 3: Based on the current set of expandable states Screening for components that meet the assembly sequence constraints of the space truss components. The state of the next moment To obtain an extended set of feasible states that satisfy the assembly sequence constraints of the space truss components. It represents the set of all spatial truss component installation states that may occur after a component is installed at the current moment and that satisfy the spatial truss component assembly sequence constraints; Step 4: Traverse the set of expandable feasible states Calculate the comprehensive assembly impact index for each of the following states. Take the state corresponding to its minimum value as the optimal expandable state at the current moment. Let the current state be... and will Add to the tail of the list of state changes; Step 5: If the current state If yes, proceed to the next step; otherwise, let And return to step 2; Step 6: Subtract the states from each pair of adjacent time points in the state change list to obtain the state change amount at that time point. Extract each The non-zero value position index is used to obtain the spatial truss assembly sequence. .

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