Development of virtual assembly system for the hot

Abstract: This paper discusses the characteristics of product assembly model, discusses the principle and feasibility of introducing virtual reality technology into the electrical field to simulate the product assembly process, analyzes the main problems and solutions faced in the development of solid relay virtual assembly system, and realizes the system based on AutoCAD 2000 graphics platform and ARX development tools

descriptors: product assembly model, solid state relay, virtual reality AutoCAD

The Development of Virtual Assembly System of Solid State Relay

Chen Tang Gong Meng Qing Long

Hebei University of Technology 300130

Abstract: In this paper it discussed the characteristic of product assembly model and the theory and feasibility for the simulation of product assembly process with the aid of virtual reality (VR) technology introduced into electrical fields. The key problem and its methods for developing solid state relay virtual assembly system was analyzed. This system was realized based on AutoCAD 2000 and ARX technology.

key words: product assembly model solid state relay virtual reality AutoCAD

I. overview

with the continuous development of modern manufacturing technology, various new ideas and technologies continue to emerge, such as computer integrated manufacturing (CIM), concurrent engineering (CE), agile manufacturing (am) Design for manufacturing (DFM) and design for assembly (DFA), etc. new manufacturing and design concepts put forward more comprehensive requirements for modern CAD technology at a higher level. Integration, intelligence and visualization have become the inevitable trend of the development of modern CAD technology. How to deal with this inevitable development trend in the research and development of CAD system in the field of electrical appliances has become an urgent and arduous task

solid state relay (SSR) is a kind of contactless electronic switch. It adopts discrete electronic components, integrated circuits and Hybrid Microelectronics Technology to realize the electrical isolation and signal coupling between the control circuit and the load circuit. The solid devices realize the on-off switching function of the load, and there are no mechanical moving parts inside. It is a new type in recent ten years. Due to its wide application, wide variety and excellent performance, the corresponding CAD system has been paid more and more attention. The development of virtual assembly system of solid state relay is the reflection of the above trend

II. Research on assembly model

the research on assembly model (AM) began in the late 1970s and has a history of more than 20 years. The earliest attempt was Autopass, a geometric modeling system developed by Liberman and Wesley. At present, most of the research on assembly modeling starts from meeting the needs of a specific application background, such as assembly process planning. Although China is still in its infancy, relevant research is becoming increasingly active

assembly model is a product information model that can completely and correctly transfer the design parameters, assembly levels and assembly information of different assemblies. The purpose of establishing assembly model is to establish a complete expression of product assembly information, which includes: management information, including the names, materials, technical specifications, technical requirements, designers and design versions of each component of the product; Geometric information, that is, information about the geometry, size, final position and attitude of the assembly; Topological information, including the hierarchical structure relationship of product assembly and the geometric fit constraint relationship between product assemblies; Engineering semantic information, that is, information related to product engineering applications; Assembly process information refers to the information related to the product assembly and disassembly process and its specific operations; Assembly resource information refers to the sum of assembly resources related to the specific implementation of product assembly process, mainly referring to the composition and control parameters of assembly system equipment. Moreover, the assembly model should not only deal with the input information of the design system, but also deal with the intermediate information and result information of the design process. Therefore, the assembly model information should be enriched and improved with the progress of the design process

The assembly model should have the following features: it can completely express the product assembly information, not only describe the information of parts and components themselves, but also describe the assembly relationship and topology between parts and components; Supporting concurrent design not only expresses the product information completely, but also describes the inheritance relationship of product design parameters and its change constraint mechanism to ensure the consistency of design parameters, so as to support the concurrent design of products; Meet the rapidly changing market demand, that is, when the product demand changes, the product design can be easily modified through the assembly model to meet the new product demand; It has a certain degree of independence

The core problem of the assembly model is how to express and store the relationship between the components of the assembly in the computer. At present, the data structure of assembly information can be divided into two categories: directly storing the mutual position information between the assembly parts; Store the fitting, connection and other assembly information between the assembly parts, and determine the homogeneous transformation matrix of the mutual position of the assembly parts, which is calculated according to these information. In Autopass developed by Liberman and Wesley, parts and assemblies are expressed as nodes in the graph structure. The branches in the graph represent the assembly relationship between components. At the same time, a spatial transformation matrix is stored on each branch to determine the relative position between components and other non geometric information; De Fazio and Whitney put forward a method called priority connection graph, which defines a set of priority rules and obtains the assembly sequence by sorting the graphs; Homem de Mello and Sanderson proposed and or diagrams to describe the assembly, in which each leaf node represents the lowest part of the assembly, and the root node represents the final product, which is somewhat similar to the CSG structure; Lee and gossard proposed a real hierarchical modeling method based on the and or diagram, which decomposes the assembly layer by layer into a tree structure composed of components. The components can be either parts or sub assemblies. The top of the tree is the assembly of the finished product, the end is an inseparable part, and the rest is the sub assembly determined by the conceptual design. Lee introduced the concept of virtual connection. The whole assembly tree is connected by virtual connection. Each virtual connection is a set of related information, so that the information of the assembly can be stored hierarchically. The above data structure or storage model has its own advantages and disadvantages, which can be selected according to the specific development requirements. The main development trend of this problem is to develop from the topological structure expressed by graph to the hierarchical structure expressed by tree

third, virtual reality technology

as a new interdisciplinary, virtual reality (VR) technology is one of the hotspots widely concerned by the modern computer industry. Virtual reality is a technology that uses computer system to generate a simulation environment (such as aircraft cockpit, assembly operation site, etc.) that is easier to meet people's needs through this kind of processing, and enables users to produce an immersive effect through various sensor devices, and realizes the direct and natural interaction between users and the environment. It is actually an advanced man-machine interface, which provides users with intuitive and natural means of real-time perception and interaction, so as to facilitate users' operation to the greatest extent, and present the simulation or simulation effect of a certain theme

a virtual reality system usually needs software and hardware support such as high-performance computers, visual display devices, head eye hand position tracking and positioning devices, three-dimensional spatial localization devices, tactile and force feedback devices, in order to produce immersion and direct natural real-time perceptual interaction. These devices often require a large amount of capital investment, which limits the application field of virtual reality technology to a certain extent. However, different applications in different fields have different requirements for software and hardware support. If the immersion requirements are moderately reduced, and real-time interaction is emphasized instead of nature, interaction means and display effects including conventional input and output devices can be considered, which is the development idea of desktop PC based VR system (dpcvrs), It is also our original intention to design the virtual assembly system of solid state relay

the graphics support platform represented by AutoCAD provides powerful 3D modeling functions and basically meets the display and simulation requirements required by the virtual environment. However, the assembly design of most systems is not perfect, there are few constraints, assembly management difficulties and other problems. Nevertheless, based on the full study of the assembly model, according to the different conditions of the assembly constraints in various fields, determine the relevant assembly tree, and use the high openness of the graphics platform, the three-dimensional modeling function provided, and powerful secondary development tools to create a realistic professional assembly simulation environment, such as translation, rotation, hiding, perspective, rendering, explosion, interference inspection, physical property calculation, parts list It is feasible to define the functions of assembly benchmark and assembly process management, and it is also feasible to use other similar specifications of oil with a kinematic viscosity of (100 ℃) 11 (1) 4 cm

IV. solid state relay assembly relationship model

assembly is an organic combination of multiple parts and sub assemblies. To get a correct assembly, we must establish the correct and complete relationship between its parts. The assembly structure tree shows the membership of components and reflects the hierarchical relationship of components. When two components have one or more connections, we call them constraint relations, and assembly relations are the basis for establishing constraint relations

the assembly relationship of general product parts is shown in Figure 1. The positioning relationship describes the spatial position relationship and matching relationship between parts, which is a direct correlation relationship; The connection relationship includes rigid connection and elastic connection. Rigid connection is divided into screw connection, key connection, pin connection, coupling, etc., while elastic connection mainly refers to spring connection. The connecting parts are generally standard parts; Motion relations are divided into transmission and relative motion. The former refers to gear transmission, belt transmission, etc., while the latter includes rotary motion, plane motion, cylindrical motion, etc. Due to its inherent characteristics, most of the assembly relationships related to solid-state relays are positioning relationships and connection relationships, and there are few motion relationships

product design is the basis of assembly. Assembly oriented design (DFA) is an important part of concurrent engineering. At present, two commonly used design processes are: bottom-up design and top-down design. It is a bottom-up design process to design parts of various shapes, input geometric constraints between parts, and then assemble the designed parts into products; It is a top-down design process to consider the constraints and positioning relationship between parts at the early stage of part design, and then realize the detailed design of a single part after completing the overall design of the product. The two designs have their own characteristics. The top-down design can reflect the real design process, save unnecessary repeated design, and improve design efficiency. The bottom-up design idea is simple, fast and convenient to operate, which is understood and accepted by most designers. Solid relay