Object-Oriented Twin Model Construction Method

Abstract

The present invention relates to an object-oriented twin model construction method, and the method comprises the following steps: (1) an encapsulation mechanism for twin model construction, (2) an inheritance and derivation mechanism for twin model construction, and (3) a polymorphism mechanism for twin model construction. This solution defines the modeling methods of digital twins in different application scenarios, standardizes the modeling process of digital twin models, and reduces the efficiency loss caused by unclear application scenarios and unclear modeling methods. It lists the mechanisms of this modeling method. This strategy defines the modeling methods of digital twins in different application scenarios, standardizes the modeling process of digital twin models, and reduces the efficiency loss caused by unclear application scenarios and unclear modeling methods.

Description

Technical Field

[0001] The present invention relates to a method for constructing an object - oriented twin model, belonging to the technical field of digital twin modeling. Background Art

[0002] Digital twin was first proposed by American scholar Grieves as a new term to describe the physical product, virtual product and the connection between them, and was first used for the health maintenance and guarantee of aerospace aircraft. In recent years, it has received extensive attention from domestic and foreign scholars and has been widely applied in many industrial fields. In 2012, NASA gave a conceptual description of digital twin: Digital twin refers to making full use of data such as physical models, sensors, and operation history, integrating multi - disciplinary and multi - scale simulation processes. As a mirror image of the physical entity product in the virtual space, it reflects the whole - life cycle process of the corresponding physical entity product. The digital twin model is an important part of digital twin and an important prerequisite for realizing the functions of digital twin. Currently, the research or application of digital twin modeling mainly focuses on the construction of geometric models, but there is less research on modeling at the physical, behavioral, and rule levels. Under the guidance of object - oriented modeling thinking, by means of encapsulation mechanism, inheritance and derivation mechanism, and polymorphism, a multi - dimensional digital twin model can be established, so that the digital twin model can be characterized as a unified whole, generating and collecting effective multi - scale fusion data during operation, and realizing global decision - making and optimization based on the fusion model and fusion data.

[0003] Currently, in the face of different production activities and production processes, digital twin modeling lacks a systematic digital twin modeling method. Summary of the Invention

[0004] The present invention precisely aims at the problems existing in the prior art and provides a method for constructing an object - oriented twin model. This method includes multiple digital twin modeling dimensions. This strategy defines the modeling methods of digital twin models under different business logics, standardizes the digital twin modeling process, and greatly improves the digital twin modeling efficiency.

[0005] In order to achieve the above - mentioned purpose, the technical solution of the present invention is as follows: A method for constructing an object - oriented twin model, the method includes the following steps:

[0006] (1) Construct the encapsulation mechanism of the digital twin model,

[0007] (2) Construct the inheritance and derivation mechanism of the digital twin model,

[0008] (3) Construct the polymorphism mechanism of the digital twin model.

[0009] Among them, the encapsulation mechanism is as follows:

[0010] 11) The encapsulation mechanism encapsulates the attributes and methods of production factors into the models at this layer, hides the implementation details, and provides access interfaces to the outside;

[0011] 12) The encapsulation mechanism sets the access permissions of attributes and methods, controls the access of other model layers to the model data at this layer and the invocation of methods, prevents the leakage of model data, and protects the integrity and security maintenance of the internal data structure of the model;

[0012] Among them, the inheritance and derivation mechanism is as follows:

[0013] 21) In the inheritance and derivation mechanism, the subclass model inherits from the superclass model. The subclass model has the same attributes and methods as the superclass model, and at the same time, it can add the attributes and methods unique to the subclass model;

[0014] 22) The inheritance and derivation mechanism realizes the reusability of the model, improves the modeling efficiency, and can control the data access and interaction between the model layers of this class and between the model layers of other classes;

[0015] 23) The inheritance and derivation mechanism can establish a group of object models with common key features. The derived submodels inherit the model data of the base model. At the same time, it is also necessary to specify the access permissions of the derived submodels and the models outside the model group for this model data. This inheritance method provides an external interface for the model, which is conducive to data interaction between different types of models;

[0016] Among them, the polymorphism mechanism is as follows:

[0017] 31) The polymorphism mechanism is based on the production behavior inside the model. After being inherited by the submodel, the submodel can endow different semantics according to the actual scenario, so that the same production behavior shows different action behaviors and behavioral logics in different submodels to meet the requirements of the diversity of production factors in the digital twin workshop. It includes the principle of behavior redefinition and the behavior interface mechanism;

[0018] 32) The principle of behavior redefinition mainly means that the submodel inherits the base model and has the production behavior of the base model. The submodel can redefine the production behavior according to the actual production needs. In essence, it is to redefine the model data, which will overwrite the data inherited from the base model, while the model data of the base model remains unchanged;

[0019] 33) The behavior interface mechanism only abstractly describes the function of this behavior, while ignoring the specific implementation method and operation content of this behavior, and requires each derived model to give its own definition according to actual needs.

[0020] Among them, the object-oriented twin model construction method means classifying and refining the production factors in the production process more reasonably. After the refinement, the production factors are hierarchically abstracted, and based on this, this type of production factor is described. Among them, the abstracted factor model is called the sub-model, and the model abstracted from the attributes and behaviors of the sub-model is called the parent model; the production factors are hierarchically abstracted and are successively divided into five layers according to the degree of abstraction: the meta-model layer (Meta Model Layer, MEML), the abstract model layer (Abstract Model Layer, ABML), the logical model layer (Logical Model Layer, LOML), the pseudo-physical model layer (Pseudophysical Model Layer, PPML), and the instance model layer (Instance Model Layer, INML).

[0021] The object-oriented twin model construction method is applicable to the modeling method that provides reusable models, simplifies the modeling process, improves the modeling efficiency, and at the same time helps to avoid errors in repeated modeling and focuses on the overall strategy of modeling. Its characteristics are: abstracting the production factors with the same physical characteristics and production behaviors in the production process into a category, that is, the template of the modeling object, and then encapsulating the physical attributes and behavior methods of the production factors into this category, and realizing the requirements of multi-dimensional modeling.

[0022] The access interfaces that need to be provided in the encapsulation mechanism and the permissions of the interfaces are set, which mainly include three parts:

[0023] Public permission access interface: For any model, through this interface, the state attributes of the public permissions inside the model can be accessed and the production behaviors can be called, but the model data of the exclusive permissions and group permissions cannot be accessed. This interface provides a channel for information and behavior interaction between different types of models.

[0024] Group permission access interface: For the sub-models of this type of model, through this interface, the state attributes of the group permissions inside the model can be accessed and the production behaviors can be called, but the model data of the exclusive permissions and public permissions cannot be accessed. This interface provides a channel for information and behavior interaction between the same type of models.

[0025] Exclusive permission access interface: The state attributes and production behaviors of the model exclusive permissions can only be modified inside the model. However, in the face of the complexity of the production workshop and ensuring the normal operation of each production factor in the workshop, the manager needs to monitor and correct the production data of each production factor in real time. The exclusive permission channel provides the manager with a special permission to access the hidden data inside the model, that is, the state attributes and production behaviors of the exclusive permissions inside the model can be accessed. Through the exclusive permission channel, the manager with the highest authority realizes the function of real-time management of the hidden data inside the model.

[0026] In the inheritance and derivation mechanism, the sub-model inherits the model data of the base model. At the same time, it is also necessary to stipulate the access rights of the derived sub-model and the models outside the model group to this model data, resulting in three inheritance methods, namely: public inheritance, closed inheritance, and semi-closed inheritance:

[0027] extends

[0028] a→A = {a<>A|a<:A|a<::A}

[0029] extends

[0030] In the formula, a→A means that a inherits A. The sub-model a has the same state attributes and production behaviors as the base model A;

[0031] a<>A: It means that a closed-inherits A. The state attributes and production behaviors with public rights and group rights in the base model are inherited into the sub-model with exclusive rights and can be directly accessed by the sub-model. However, the state attributes and production behaviors with exclusive rights in the base model cannot be modified by the sub-model or the models outside the model group. This inheritance method can shield the state attributes and production behaviors with public rights or group rights in the base model and terminate the continued derivation of the state characteristics and functional characteristics of the base model;

[0032] a<:A: It means that a semi-closed-inherits A. The state attributes and productions with public rights and group rights in the base model are inherited into the sub-model with group rights and can be directly accessed by the sub-model. However, the state attributes and production behaviors with exclusive rights in the base model cannot be modified by the sub-model or the models outside the model group. This inheritance method can be used to shield the access and modification of the state attributes and production behaviors with public rights in the base model by the models outside the model group and only allow access and modification within the model group;

[0033] a<::A: a publicly inherits A. The state attributes and production behaviors with public rights and group rights in the base model are inherited into the sub-model with their access attributes unchanged and can be directly accessed by the sub-model or the models outside the model group. However, the state attributes and production behaviors with private rights in the base model cannot be modified by the sub-model or the models outside the model group. This inheritance method provides an external interface for the model and is conducive to data interaction between different types of models.

[0034] In the polymorphic mechanism, the virtual model stipulates that production factor object models cannot be directly created using the virtual model. It is only for sub-models to inherit. Sub-models need to specifically implement the behavior interfaces according to actual production requirements, thereby showing different behavioral characteristics. The virtual model is a special model that establishes a common interface for a group of models, facilitating the polymorphic use of production behaviors therein. If a sub-model derived from the virtual model provides definitions for all the behavior interfaces of the virtual model, this sub-model can directly create production factor object models. Conversely, if a sub-model derived from the virtual model does not provide definitions for all the behavior interfaces of the virtual model, this sub-model remains a virtual model and still cannot create production factor object models.

[0035] Compared with the prior art, the present invention has the following advantages. This technical solution explores a method for constructing twin models based on object-oriented thinking, meets the requirements for digital twin modeling in the workshop, and can provide guiding suggestions for the digital twin transformation of the production workshop. At the same time, this method defines the modeling mechanism of digital twins under different conditions, clarifies the modeling elements of digital twins in different application scenarios, standardizes the digital twin modeling process, and reduces efficiency losses caused by unclear application scenarios and unclear assembly methods. Brief Description of the Drawings

[0036] Figure 1 It is a schematic diagram of the object-oriented modeling idea of the present invention;

[0037] Figure 2 It is a schematic diagram of the encapsulation mechanism of the present invention;

[0038] Figure 3 It is a schematic diagram of the inheritance and derivation mechanism of the present invention;

[0039] Figure 4 It is a schematic diagram of the polymorphic mechanism of the present invention;

[0040] Figure 5 It is a schematic diagram of the modeling idea of the digital twin workshop of the present invention;

[0041] Figure 6 It is a schematic diagram of the modeling process of the Fanuc M-20iA industrial robot model of the present invention. Detailed Description of the Preferred Embodiment

[0042] To deepen the understanding of the present invention, the following detailed description is given in conjunction with the accompanying drawings for this embodiment.

[0043] Embodiment 1:

[0044] Figure 1 As shown, for the object-oriented twin model construction method, the modeling steps are as follows:

[0045] (1) Encapsulation mechanism for digital twin model construction:

[0046] (2) Inheritance and derivation mechanism for digital twin model construction.

[0047] (3) Polymorphism mechanism for digital twin model construction.

[0048] Among them, the object-oriented twin model construction method means classifying and refining the production factors in the production process more reasonably. After refinement, the production factors are hierarchically abstracted, and based on this, this type of production factor is described. The abstracted factor model is called a sub-model, and the model abstracted from the attributes and behaviors of the sub-model is called a parent model; the production factors are hierarchically abstracted and different types are divided according to the degree of abstraction;

[0049] The object-oriented twin model construction method is applicable to building reusable models. The encapsulation mechanism is as follows. For specific reference, Figure 2 :

[0050] 11) The encapsulation mechanism encapsulates the attributes and methods of the production factors into the model at this layer, hides its implementation details, and provides an access interface to the outside;

[0051] 12) The encapsulation mechanism sets the access permissions of the attributes and methods, controls the access of other model layers to the model data at this layer and the invocation of methods, prevents the leakage of model data, and protects the integrity and security maintenance of the internal data structure of the model;

[0052] The object-oriented twin model construction method is applicable to models with common characteristics. The inheritance and derivation mechanism is as follows. For specific reference, Figure 3 :

[0053] 21) In the inheritance and derivation mechanism, the subclass model inherits from the parent class model. This subclass model has the same attributes and methods as the parent class model, and at the same time can add the attributes and methods unique to the subclass model;

[0054] 22) The inheritance and derivation mechanism realizes the reusability of the model, improves the modeling efficiency, and can control the data access and interaction between this type of model layers and other type of model layers;

[0055] 23) The inheritance and derivation mechanism can establish an object model group with common key characteristics. The derived sub-model inherits the model data of the base model. At the same time, it is also necessary to stipulate the access permissions of the derived sub-model and the models outside the model group to this model data. This inheritance method provides an external interface for the model, which is conducive to data interaction between different types of models;

[0056] The object-oriented twin model construction method is applicable to models with diverse production behaviors. The polymorphism mechanism is as follows. For specific reference, Figure 4 :

[0057] 31) The polymorphic mechanism bases on the production behavior inside the model. After being inherited by the sub-model, the sub-model can endow different semantics according to the actual scenario, enabling the same production behavior to exhibit different action behaviors and behavioral logics in different sub-models to meet the requirements of the diversity of production elements in the digital twin workshop. It includes the principle of behavior redefinition and the behavior interface mechanism;

[0058] 32) The principle of behavior redefinition mainly means that the sub-model inherits the base model and has the production behavior of the base model. The sub-model can redefine the production behavior according to the actual production needs. Essentially, redefining the model data will overwrite the data inherited from the base model, while the model data of the base model remains unchanged;

[0059] 33) The behavior interface mechanism only makes an abstract description of the function of this behavior, while ignoring the specific implementation method and operation content of this behavior, and requires each derived model to give its own definition according to actual needs;

[0060] The object-oriented twin model construction method is applicable to the modeling method that provides reusable models, simplifies the modeling process, improves the modeling efficiency, and at the same time helps to avoid errors in repeated modeling and focus on the overall strategy of modeling. Its characteristics are: abstracting the production elements with the same physical characteristics and production behaviors in the production process into a class, that is, the template of the modeling object, and then encapsulating the physical attributes and behavioral methods of the production elements into this class and realizing the requirements of multi-dimensional modeling.

[0061] The object-oriented twin model construction method is applicable to the production modeling of intelligent workshops. Its characteristics are that through the encapsulation mechanism and inheritance and derivation mechanism, the instance model inherits the basic attributes of the meta-model and the geometric attributes, physical attributes, behavioral methods, and rule attributes of the abstract model and class model in turn, as specifically Figure 5 shown. The instance model adds specific attributes and methods to meet the needs of actual production activities.

[0062] Example 2:

[0063] The Fanuc M20iA industrial robot is widely used in various production scenarios such as machining, stamping, forging, workpiece handling, picking, loading and unloading, etc. In this article, the Fanuc M20iA industrial robot is applied to the medicine bottle packaging production line of a pharmaceutical enterprise, and it is responsible for palletizing medicine boxes.

[0064] (1) Figure 2 As shown, taking the Fanuc M-20iA industrial robot as an example, based on the digital twin workshop

[0065] MEML-ABML-LOML-PPML-INML five-layer modeling framework, introduce the modeling mechanism and the content of each layer of the model, and elaborate on its modeling process:

[0066] The creation process of the twin model of the Fanuc M-20iA industrial robot. For the specific process, refer to Figure 6 , which is actually a process in which the instance model Fanuc M-20iA invokes its creation behavior to instantiate the production factor object model Fanuc M-20iA-01. The specific process is as follows:

[0067] 11) Abstractly divide it according to production functions. The model is abstractly divided into a meta-model, an equipment model, a transportation and handling equipment model, a handling robot model, and a Fanuc M20iA signal robot model in sequence.

[0068] 12) Meta-model (MEM), which internally defines the general attributes and behaviors of equipment classes, such as power, position, power-on startup, fault stop, etc.;.

[0069] 13) Logic model layer (LOML), which is a high-level abstraction of the equipment for moving, storing, controlling, etc. materials throughout the workshop production process. It internally defines the attributes and behaviors related to transportation and handling, such as the starting position of transportation, the ending position, the handling speed, the transportation or handling behavior, etc.;

[0070] 14) Physical-like model layer (PPML), which is a special transportation and handling equipment that replaces manual handling. It internally defines the attributes and behaviors related to robots with handling functions, such as repeat positioning accuracy, the number of control axes, etc.;

[0071] 15) Instance model layer (INML), which is directly abstracted from the physical workshop production factor Fanuc M20iA. It internally defines the specific attributes and behaviors related to the actual production scenario, such as the specific geometric dimensions of the Fanuc M20iA robot, or the real-time rotation angles of each joint when handling workpieces, for the motion control of the equipment Fanuc M20iA, etc.

[0072] 16) Model encapsulation mechanism. Set the attribute information of the meta-model to public permissions. The models of the remaining model layers need to be specifically set according to the specific production scenario on-site. For example, set the access permissions of the attributes and behaviors used for interacting with other models to public permissions. For example: the equipment position of the equipment model, and set the attributes and behaviors that are only for inheritance and access within the model group to group-owned attributes, such as the number of control axes of the handling robot model. For the attributes and behaviors that are only modified and accessed within the model, set them to private permissions, such as the J1-J6 motion range of Fanuc M20iA.

[0073] 17) Through the inheritance mechanism, MEML-ABML-LOML-PPML-INML inherits from top to bottom in sequence. The Fanuc M20iA industrial robot has all the public and group-owned attributes and behaviors of the Equipment model, Handling Equipment model, and Handling Robot model, and its internal defines specific attributes and behaviors related to the actual scenario. For the attributes and behaviors jointly owned by the Fanuc M20iA industrial robot, they are defined in the base models of each layer. As a sub-model, only inheritance and use are required, without re-definition, which improves the efficiency of modeling and the reusability of the model.

[0074] In summary, under the five-layer modeling framework of MEML-ABML-LOML-PPML-INML, the digital twin modeling of the Fanuc M20iA industrial robot is completed by using the encapsulation mechanism, inheritance and derivation mechanism, and polymorphism mechanism.

[0075] It should be noted that the above embodiments are not used to limit the protection scope of the present invention. Equivalent transformations or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. Object - Oriented Twin Model Construction Method, characterized in that, the method comprises the following steps: (1) Encapsulation mechanism for twin model construction, (2) Inheritance and derivation mechanism for twin model construction, (3) Polymorphism mechanism for twin model construction; The object - oriented twin model construction method means classifying and refining production factors in the production process more reasonably. After refinement, the production factors are hierarchically abstracted, and based on this, this type of production factor is described. Among them, the abstracted element model is called the sub - model, and the model abstracted from the attributes and behaviors of the sub - model is called the parent model; the production factors are hierarchically abstracted and divided into five layers according to the degree of abstraction: the meta - model layer, the abstract model layer, the logical model layer, the quasi - physical model layer, and the instance model layer; The construction of the encapsulation mechanism in step (1) is as follows: 11) The encapsulation mechanism encapsulates the attributes and methods of production factors into the meta - model layer, the abstract model layer, the logical model layer, the quasi - physical model layer, and the instance model layer, hides its implementation details, and provides three corresponding access interfaces to the outside; 12) The encapsulation mechanism sets the access permissions of attributes and methods, controls the access of other model layers to the model data of the encapsulated layer and the invocation of methods, prevents the leakage of model data, and protects the integrity and security maintenance of the internal data structure of the model; Step (2) constructs the inheritance and derivation mechanism, which is as follows: 21) In the inheritance and derivation mechanism, the subclass model inherits from the parent class model. This subclass model has the same attributes and methods as the parent class model, and at the same time, it can add attributes and methods unique to the subclass model; 22) The inheritance and derivation mechanism realizes the reusability of the model, improves the modeling efficiency, and controls the data access and interaction between this type of model layers and between other types of model layers; 23) The inheritance and derivation mechanism establishes an object model group with common key features. The derived sub - model inherits the model data of the base model. At the same time, it is also necessary to stipulate the access permissions of the derived sub - model and models outside the model group to this model data. This inheritance method provides an external interface for the model, which is conducive to data interaction between different types of models; In step (3), the construction of the polymorphism mechanism is as follows: 31) For the production behavior inside the base model of the polymorphism mechanism, after being inherited by the sub - model, the sub - model can endow different semantics according to the actual scenario, so that the same production behavior shows different action and logic in different sub - models to meet the requirements of the diversity of production factors in the digital twin workshop. It includes the behavior re - definition principle and the behavior interface mechanism; 32) The behavior re - definition principle means that the sub - model inherits the base model and has the production behavior of the base model. The sub - model re - defines the production behavior according to the actual production needs. In essence, it re - defines the model data, which will overwrite the data inherited from the base model, while the model data of the base model remains unchanged; 33) The behavior interface mechanism only abstractly describes the function of this behavior, while ignoring the specific implementation method and operation content of this behavior. It requires each derived model to give its own definition according to actual needs. The model with a behavior interface is a virtual model.

2. The object - oriented twin model construction method according to claim 1, It is characterized in that The access interfaces to be provided in the encapsulation mechanism and the permissions of the interfaces are set, including three parts: Public permission access interface: For any model, through this interface, the state attributes of the public permissions inside this model can be accessed and the production behaviors can be invoked, but the model data of the exclusive permissions and group permissions cannot be accessed. This interface provides a channel for information and behavior interaction between different types of models. Group permission access interface: For the sub-models of this type of model, through this interface, the state attributes of the group permissions inside this model can be accessed and the production behaviors can be invoked, but the model data of the exclusive permissions and public permissions cannot be accessed. This interface provides a channel for information and behavior interaction between models of the same type. Exclusive permission access interface: The state attributes and production behaviors of the exclusive permissions of the model can only be modified inside the model. However, in the face of the complexity of the production workshop and to ensure the normal operation of all production elements in the workshop, managers need to monitor and correct the production data of each production element in real time. The exclusive permission channel provides managers with a special access privilege to the hidden data inside this model, that is, to access the state attributes and production behaviors of the exclusive permissions inside this model. Through the exclusive permission channel, the manager with the highest authority realizes the function of real-time management of the hidden data inside the model.

3. The object-oriented twin model construction method according to claim 2 It is characterized in that In the inheritance and derivation mechanism, the sub-model inherits the model data of the base model. At the same time, it is also necessary to stipulate the access permissions of the derived sub-models and models outside the model group for this model data, resulting in 3 inheritance methods, namely: public inheritance, closed inheritance, and semi-closed inheritance: In the formula indicates that a inherits A, and the sub-model a has the same state attributes and production behaviors as the base model A; a <> A: It means that a closed inherits A. The state attributes and production behaviors of the public permissions and group permissions in the base model are inherited as exclusive permissions into the sub-model and can be directly accessed by the sub-model, while the state attributes and production behaviors of the exclusive permissions of the base model cannot be modified by the sub-model or models outside the model group. This inheritance method can shield the state attributes and production behaviors of the public permissions or group permissions in the base model and terminate the continued derivation of the state characteristics and functional characteristics of the base model. a <: A: It means that a semi-closed inherits A. The state attributes and productions of the public permissions and group permissions in the base model are inherited as group permissions into the sub-model and can be directly accessed by the sub-model, while the state attributes and production behaviors of the exclusive permissions of the base model cannot be modified by the sub-model or models outside the model group. This inheritance method can be used to shield the access and modification of the state attributes and production behaviors of the public permissions of the base model by models outside the model group and only access and modify them within this model group. a <:: A: a publicly inherits A. The state attributes and production behaviors of the public permissions and group permissions in the base model are inherited into the sub-model with their access attributes unchanged and can be directly accessed by the sub-model or models outside the model group, while the state attributes and production behaviors of the private permissions of the base model cannot be modified by the sub-model or models outside the model group. This inheritance method provides an external interface for the model and is conducive to data interaction between different types of models.

4. The object-oriented twin model-based construction method according to claim 3, characterized in that, in the polymorphism mechanism, the virtual model stipulates that production factor object models cannot be directly created using the virtual model. It is only for inheritance by sub-models. Sub-models need to specifically implement the behavior interfaces according to actual production requirements, thereby showing different behavioral characteristics. The virtual model is a special model. Through it, a common interface is established for a group of models to facilitate polymorphic use of the production behaviors therein. If a sub-model derived from the virtual model provides definitions for all the behavior interfaces of the virtual model, this sub-model directly creates production factor object models. Conversely, if a sub-model derived from the virtual model does not provide definitions for all the behavior interfaces of the virtual model, this sub-model remains a virtual model and still cannot create production factor object models.

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