Movable part cross-scale mechanical product design method and device, medium and product

Abstract

The invention discloses a movable part cross-scale mechanical product design method and device, a medium and a product, and relates to the field of mechanical manufacturing, and the method comprises the steps: obtaining a three-dimensional model of each part of a to-be-designed mechanical product; carrying out stress simulation on the three-dimensional model of each part by utilizing finite element analysis software, determining a machining drawing and a movable part assembly drawing of each part according to a simulation result and preset yield strength to obtain a movable part, and carrying out a semi-physical simulation test on the movable part to obtain a semi-physical simulation test result; the method comprises the following steps: obtaining physical parameters, a normal contact force model and a friction force model at a contact interface of a movable part, establishing a kinetic equation of the movable part by using a Newton-Euler method, solving the kinetic equation to obtain output parameters of the movable part, and obtaining a corresponding mechanical product in combination with expected precision of the output parameters. According to the method, the cross-scale relation between the micro-nano scale interface physical process and the macroscopic mechanical motion is established, and the precision of mechanical product design is improved.

Description

Technical Field

[0001] The present application relates to the field of mechanical manufacturing, and in particular to a design method, equipment, medium and product for a cross-scale mechanical product with movable parts. Background Art

[0002] Manufacturing is an important foundation for national economic and national defense construction, and design is the foundation for the development of manufacturing. Without a strong manufacturing industry, there will be no sustainable development of the national economy, and without advanced design support, there will be no advanced manufacturing industry.

[0003] A piece of equipment is assembled from many parts, and there is mutual contact between two adjacent parts. The contact area is called the contact interface. The contact interface has a decisive influence on the dynamic performance of mechanical equipment. The reason is that the contact interface is the weakest area of ​​mechanical equipment, and more than 75% of the causes of mechanical failures occur at the contact interface. In addition, more than 50% of the stiffness of mechanical equipment and more than 70% of the damping also come from the contact interface. It can be seen that the contact interface characteristics are one of the bottlenecks restricting the independent research and development of high-end mechanical equipment.

[0004] Since the contact interface is at the microscopic and mesoscopic scales, while the motion output of mechanical equipment is generally at the macroscopic scale, how to establish a connection between the two is an issue that needs to be urgently addressed. Summary of the invention

[0005] The purpose of this application is to provide a method, equipment, medium and product for designing cross-scale mechanical products with movable parts, so as to improve the accuracy of mechanical product design.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a method for designing a cross-scale mechanical product with movable parts, comprising:

[0008] Obtaining three-dimensional models of various parts of the mechanical product to be designed;

[0009] Using finite element analysis software, a force simulation is performed on the three-dimensional model of each of the parts to obtain a simulation result;

[0010] Determine the processing drawings and the assembly drawings of the movable parts of each of the parts according to the simulation results and the preset yield strength;

[0011] A semi-physical simulation test is performed on the movable component to obtain physical parameters, a normal contact force model and a friction force model at the contact interface of the movable component; the movable component is obtained by assembling a part sample based on the movable component assembly drawing; the part sample is obtained by processing the part based on the processing drawing;

[0012] According to the physical parameters, normal contact force model and friction force model at the contact interface of the movable component, the dynamic equation of the movable component is established and solved by using the Newton-Euler method to obtain the output parameters of the movable component; the output parameters include the position and posture of the output end of the movable component;

[0013] Based on the output parameters of the active component and the expected accuracy of the output parameters, a corresponding mechanical product is obtained.

[0014] Optionally, obtaining a three-dimensional model of each part of the mechanical product to be designed specifically includes:

[0015] Selecting materials for various parts of the mechanical product to be designed according to the set load, and determining initial structural parameters of each part;

[0016] According to the initial structural parameters of each of the parts, a three-dimensional model of each of the parts is established using three-dimensional modeling software.

[0017] Optionally, according to the simulation results and the preset yield strength, determining the processing drawings and the movable parts assembly drawings of the parts specifically includes:

[0018] Determining whether the simulation result meets the preset yield strength;

[0019] If so, determine the processing drawings and moving parts assembly drawings of each of the said parts;

[0020] If not, the initial structural parameters of each of the parts are updated, and the three-dimensional models of each of the parts are re-established.

[0021] Optionally, the physical parameters at the contact interface include interface friction, interface lubrication, interface gap and interface morphology.

[0022] Optionally, based on the output parameter of the movable component and the expected accuracy of the output parameter, a corresponding mechanical product is obtained, specifically including:

[0023] Determining whether the output parameter of the active component reaches the expected accuracy of the output parameter;

[0024] If yes, assembling the movable parts that achieve the expected accuracy of the output parameters to obtain the corresponding mechanical product;

[0025] If not, the processing drawings and the assembly drawings of the moving parts of the parts that do not reach the expected accuracy of the output parameters are updated.

[0026] Optionally, after obtaining a corresponding mechanical product based on the output parameter of the movable component and the expected accuracy of the output parameter, the method further includes:

[0027] Conducting a test experiment on the mechanical product to obtain performance characterization parameters of the mechanical product; the performance characterization parameters include displacement and posture of the output end of the mechanical product;

[0028] Determining whether the performance characterization parameter reaches the set performance characterization parameter;

[0029] If so, mass production of mechanical products will be carried out;

[0030] If not, update the active parts assembly drawing.

[0031] Optionally, the performance characterization parameter is obtained through a displacement sensor and an inertial sensor.

[0032] In a second aspect, the present application provides a computer device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement any of the above-described methods for designing cross-scale mechanical products with movable parts.

[0033] In a third aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any of the above-described methods for designing cross-scale mechanical products with movable parts.

[0034] In a fourth aspect, the present application provides a computer program product, including a computer program, which, when executed by a processor, implements any of the above-mentioned methods for designing cross-scale mechanical products with movable parts.

[0035] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0036] The present application provides a method, device, medium and product for designing cross-scale mechanical products with movable parts, obtains the three-dimensional model of each part of the mechanical product to be designed; uses finite element analysis software to simulate the force on the three-dimensional model of each part to obtain the simulation result; according to the simulation result and the preset yield strength, determines the processing drawing of each part and the assembly drawing of the movable parts; performs a semi-physical simulation test on the movable parts to obtain the physical parameters, normal contact force model and friction force model at the contact interface of the movable parts; the movable parts are assembled from the part samples based on the assembly drawing of the movable parts; the part samples are processed from the parts based on the processing drawings; according to the physical parameters, normal contact force model and friction force model at the contact interface of the movable parts, the dynamic equation of the movable parts is established and solved using the Newton-Euler method to obtain the output parameters of the movable parts; based on the output parameters of the movable parts and the expected accuracy of the output parameters, the corresponding mechanical products are obtained. The present application expresses the microscopic and mesoscopic physical change process at the contact interface in mechanical design with design language, establishes a cross-scale connection between the micro-nanoscale interface physical process and the macroscopic mechanical motion, and improves the accuracy of mechanical product design. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 A schematic diagram of a flow chart of a method for designing a cross-scale mechanical product with movable parts provided in one embodiment of the present application;

[0039] Figure 2 A schematic diagram of the structure of a computer device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0041] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0042] This application proposes a cross-scale mechanical product design method for movable parts, which expresses the microscopic and mesoscopic physical change processes at the contact interface in mechanical design using design language, establishes a cross-scale connection between micro-nanoscale interface physical processes and macroscopic mechanical motion, and solves the obstacles and barriers at the intersection of mechanics and interface science in mechanical design.

[0043] The present application provides a method for designing a cross-scale mechanical product with movable parts, which includes three steps: part design-processing-assembly-analysis step, semi-physical simulation analysis step, and component assembly-analysis step.

[0044] In an exemplary embodiment, Figure 1 As shown, a method for designing a cross-scale mechanical product with a moving part is provided, comprising the following steps:

[0045] S1: Obtain the three-dimensional model of each part of the mechanical product to be designed.

[0046] As an optional implementation, S1 specifically includes:

[0047] The materials of the parts of the mechanical product to be designed are selected according to the set load, and the initial structural parameters of the parts are determined.

[0048] According to the initial structural parameters of each of the parts, a three-dimensional model of each of the parts is established using three-dimensional modeling software.

[0049] S2: Using finite element analysis software, perform force simulation on the three-dimensional model of each of the parts to obtain simulation results.

[0050] S3: Determine the processing drawings and movable component assembly drawings of each of the parts according to the simulation results and the preset yield strength.

[0051] As an optional implementation, S3 specifically includes:

[0052] Determine whether the simulation result meets the preset yield strength.

[0053] If so, determine the processing drawings and movable parts assembly drawings of each of the parts.

[0054] If not, the initial structural parameters of each of the parts are updated, and the three-dimensional models of each of the parts are re-established.

[0055] In practical applications, S1-S3 refers to the parts design-processing-assembly-analysis process, which includes the following:

[0056] Select materials for parts according to the load requirements (set load) they bear, and initialize and define their structural parameters; use 3D modeling software to draw 3D models of each part; import the 3D model of the part into finite element analysis software to simulate the force on it; compare the simulation results with the yield strength index of the part (preset yield strength). If the bearing capacity of the part cannot meet the yield strength index, the structural parameters of the part need to be redefined; if the bearing capacity of the part can meet the yield strength index, an engineering drawing can be made, which includes the processing drawing of the part and the assembly drawing of the active parts; process the parts according to the processing drawing requirements; assemble the parts to obtain the active parts according to the assembly drawing requirements.

[0057] S4: Perform a semi-physical simulation test on the moving part to obtain the physical parameters, normal contact force model and friction force model at the contact interface of the moving part; the moving part is obtained by assembling the part sample based on the moving part assembly drawing; the part sample is obtained by processing the part based on the processing drawing. The physical parameters at the contact interface include interface friction, interface lubrication, interface gap and interface morphology.

[0058] S5: According to the physical parameters, normal contact force model and friction force model at the contact interface of the movable component, the dynamic equation of the movable component is established and solved using the Newton-Euler method to obtain the output parameters of the movable component; the output parameters include the position and posture of the output end of the movable component.

[0059] S6: Based on the output parameters of the movable component and the expected accuracy of the output parameters, a corresponding mechanical product is obtained.

[0060] As an optional implementation, S6 specifically includes:

[0061] It is determined whether the output parameter of the active component reaches the expected accuracy of the output parameter.

[0062] If so, the movable parts that achieve the expected accuracy of the output parameters are assembled to obtain the corresponding mechanical products.

[0063] If not, the processing drawings and the assembly drawings of the moving parts of the parts that do not reach the expected accuracy of the output parameters are updated.

[0064] In practical applications, S4-S6 is the semi-physical simulation analysis link, which includes the following contents: select the installation position of the detection device and the simulation loading device according to the action type of the movable component assembly, and complete the construction of the semi-physical prototype; carry out semi-physical simulation tests according to the dynamic characteristics requirements of the whole machine, obtain the variation law of the physical parameters at the contact interface of the movable component, and convert the variation law of the physical parameters at the contact interface into a digital model through data fitting and model identification. The digital model includes the normal contact force model and the friction force model at the moving contact interface; substitute the normal contact force model and the friction force model into the dynamic equation of the movable component; write a dynamic equation solving program through MATLAB software, and assign the conditional variables in the equation according to the calculation conditions; further, obtain the output parameters of the movable component through numerical calculation. The output parameters include the position and posture of the output end (end effector).

[0065] The output parameter variation law of the moving parts is compared with the ideal dynamic law of the output parameters (the ideal variation law of the output parameters of the moving parts can be obtained by the Newton-Euler method when the gap and friction at the contact interface are not considered) to determine whether it is qualified, that is, whether the output parameters of the moving parts can achieve the expected accuracy. If it is unqualified, it is necessary to change the engineering drawings and assembly process requirements (moving parts assembly drawings); if it is qualified, enter the component assembly-analysis stage.

[0066] The friction force model and normal contact force model are obtained in the semi-physical simulation analysis phase, and are classified and stored in the database according to the motion types of the active parts.

[0067] Furthermore, when the friction force model and the normal contact force model can be found through the database, there is no need to make a semi-physical prototype and conduct a semi-physical simulation test. The friction force model and the normal contact force model stored in the database can be directly called for use in the dynamic modeling of other components.

[0068] Common dynamic modeling methods include: Newton-Euler method, Lagrange equations, and Kane equations. These methods can establish the dynamic equations of mechanical systems. Considering the solution of the forces at the contact interface, the modeling process of the Newton-Euler method is shown below:

[0069] For a multi-body rigid body system, assume that the center of mass acceleration of a link is a S , then the net external force acting on the connecting rod and the center of mass acceleration a S Satisfies Newton's second law F 合 =ma S , F 合 is the resultant external force acting on the connecting rod, and m is the mass of the connecting rod.

[0070] When the connecting rod rotates around the axis of the center of mass, the moment of inertia SJ, angular acceleration α, angular velocity ω and action torque τ satisfy the Euler equation τ = S Jα+ω×( S Jω).

[0071] When using the Newton-Euler method to establish a dynamic model of a multi-rigid body system, the following two steps are generally required: The first step is to recursively calculate the expressions of displacement, velocity, and acceleration of each connecting rod, and calculate the expressions of inertia force and inertia moment of each connecting rod and base according to Newton's second law and Euler equation. The second step is to recursively calculate the interaction force and moment expressions at the joints of each connecting rod and base.

[0072] Recursion outward:

[0073]

[0074]

[0075]

[0076] in, is the total acceleration at the center of mass of the i+1th connecting rod; i+1 a i+1 is the acceleration at the i+1th connecting rod axis; is the position vector of the mass center of the i+1th connecting rod relative to its own rigid body coordinate system; i+1 ω i+1 is the angular velocity of the i+1th link relative to its own rigid body coordinate system; is the resultant force at the mass center of the i+1th connecting rod; m i+1 is the mass of the i+1th connecting rod; is the resultant moment at the center of mass of the i+1th connecting rod; is the moment of inertia of the i+1th connecting rod relative to its own axis of rotation.

[0077] Recursion inwards:

[0078]

[0079]

[0080]

[0081] in, i F i is the resultant force at the i-th connecting rod axis; is the rotation transformation matrix of the rigid body coordinate system of the i+1th link relative to the rigid body coordinate system of the ith link; F i+1 is the force exerted by the i-th connecting rod on the i+1-th connecting rod; is the resultant force at the center of mass of the ith connecting rod;i τ i is the torque of the i-1th connecting rod on the i-th connecting rod; τ i+1 is the torque of the i-th connecting rod on the i+1-th connecting rod; is the resultant moment at the center of mass of the ith connecting rod; is the position vector at the center of mass of the i-th connecting rod; i p i+1 is the position vector of the rigid body coordinate system of the i+1th link relative to the rigid body coordinate system of the ith link; τ i is the torque of the i-th connecting rod in the direction of the axis of rotation; T is the transposition; i z i is the rotation axis direction vector of the i-th connecting rod.

[0082] By combining the above expressions, any unknown quantity can be solved.

[0083] In practical applications, after obtaining the corresponding mechanical product based on the output parameters and the expected accuracy of the output parameters of the active components, the component assembly-analysis link is also included. The specific steps are as follows:

[0084] A test machine experiment is carried out on the mechanical product to obtain performance characterization parameters of the mechanical product; the performance characterization parameters include the displacement and posture of the output end of the mechanical product.

[0085] Determine whether the performance characterization parameter reaches the set performance characterization parameter.

[0086] If yes, the mechanical product will be mass-produced.

[0087] If not, update the active parts assembly drawing.

[0088] In practical applications, the component assembly-analysis phase includes the following contents: assembling components that meet the performance requirements of semi-physical simulation analysis to obtain a physical prototype (mechanical product); conducting a test run on the physical prototype, and obtaining the change law of the performance characterization parameters (displacement and posture accuracy) of the physical prototype by adding sensors (i.e., displacement sensors and inertial sensors) to the end of the physical prototype, and comparing and analyzing them with the theoretical results (expected displacement and posture accuracy, i.e., set performance characterization parameters) to determine whether they are qualified; if not, the component assembly process requirements must be changed; if qualified, the equipment can be put into mass production.

[0089] This application achieves precise design of mechanical equipment by converting microscopic and mesoscopic parameters at the contact interface into mathematical models and applying them to mechanical design and optimization.

[0090] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Figure 2 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. Among them, the processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a method for designing a cross-scale mechanical product of an active component is implemented.

[0091] Those skilled in the art will understand that Figure 2 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components. In an exemplary embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the above-mentioned method for designing a cross-scale mechanical product with an active component is implemented.

[0092] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, which, when executed by a processor, implements the above-mentioned method for designing a cross-scale mechanical product with movable parts.

[0093] In an exemplary embodiment, a computer program product is provided, comprising a computer program, which implements the above-mentioned method for designing a cross-scale mechanical product with movable parts when executed by a processor.

[0094] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0095] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0096] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0097] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for designing a cross-scale mechanical product with movable parts, characterized in that: include: Obtaining three-dimensional models of various parts of the mechanical product to be designed; Using finite element analysis software, a force simulation is performed on the three-dimensional model of each of the parts to obtain a simulation result; Determine the processing drawings and the assembly drawings of the movable parts of each of the parts according to the simulation results and the preset yield strength; A semi-physical simulation test is performed on the movable component to obtain physical parameters, a normal contact force model and a friction force model at the contact interface of the movable component; the movable component is obtained by assembling a part sample based on the movable component assembly drawing; the part sample is obtained by processing the part based on the processing drawing; According to the physical parameters, normal contact force model and friction force model at the contact interface of the movable component, the dynamic equation of the movable component is established and solved by using the Newton-Euler method to obtain the output parameters of the movable component; the output parameters include the position and posture of the output end of the movable component; Based on the output parameters of the active component and the expected accuracy of the output parameters, a corresponding mechanical product is obtained.

2. The method for designing a cross-scale mechanical product with movable parts according to claim 1, characterized in that: Obtain the 3D models of the parts of the mechanical product to be designed, including: Selecting materials for various parts of the mechanical product to be designed according to the set load, and determining initial structural parameters of each part; According to the initial structural parameters of each of the parts, a three-dimensional model of each of the parts is established using three-dimensional modeling software.

3. The method for designing a cross-scale mechanical product with movable parts according to claim 2, characterized in that: According to the simulation results and the preset yield strength, the processing drawings of the parts and the assembly drawings of the movable parts are determined, specifically including: Determining whether the simulation result meets the preset yield strength; If so, determine the processing drawings and moving parts assembly drawings of each of the said parts; If not, the initial structural parameters of each of the parts are updated, and the three-dimensional models of each of the parts are re-established.

4. The method for designing a cross-scale mechanical product with movable parts according to claim 1, characterized in that: The physical parameters at the contact interface include interface friction, interface lubrication, interface gap and interface morphology.

5. The method for designing a cross-scale mechanical product with movable parts according to claim 1, characterized in that: Based on the output parameters of the active component and the expected accuracy of the output parameters, a corresponding mechanical product is obtained, specifically including: Determining whether the output parameter of the active component reaches the expected accuracy of the output parameter; If yes, assembling the movable parts that achieve the expected accuracy of the output parameters to obtain the corresponding mechanical product; If not, the processing drawings and the assembly drawings of the moving parts of the parts that do not reach the expected accuracy of the output parameters are updated.

6. The method for designing a cross-scale mechanical product with movable parts according to claim 1, characterized in that: After obtaining the corresponding mechanical product based on the output parameter of the active component and the expected accuracy of the output parameter, the method further includes: Conducting a test experiment on the mechanical product to obtain performance characterization parameters of the mechanical product; the performance characterization parameters include displacement and posture of the output end of the mechanical product; Determining whether the performance characterization parameter reaches the set performance characterization parameter; If so, mass production of mechanical products will be carried out; If not, update the active parts assembly drawing.

7. The method for designing a cross-scale mechanical product with movable parts according to claim 6, characterized in that: The performance characterization parameters are obtained through displacement sensors and inertial sensors.

8. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method for designing a cross-scale mechanical product of a movable part according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for designing a cross-scale mechanical product with movable parts described in any one of claims 1 to 7 is implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the method for designing a cross-scale mechanical product with movable parts described in any one of claims 1 to 7 is implemented.

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