Architecture of software bus for testing environment of aerospace measurement and control virtual instrument

Aerospace measurement and control virtual instrument test environment software bus architecture Yu Gongjing Ma Haodong (Beijing Aerospace Measurement and Control Technology Development Company, Beijing, 100041)

Testing technology is the only engineering technology that runs through each stage of the product's entire life cycle. The core technology of testing is software, which is the key to achieving commercial off-the-shelf (COTS) products. Automatic test equipment (Automatic Test Equipment) software platform should be based on the "interconnection, interoperability, interoperability" principle as the basic requirement to achieve the integration and sharing of test and diagnostic information.
The virtual instrument test environment (VITE) is an open general test software platform product that supports the IEEE 1226 wide area test environment (A Broad –Based Environment for Test) standard. It uses a soft bus (object bus) structure. Use the principle of object model driving to establish a transparent communication channel between each object model component, and between the user and provider of the component. Its purpose is to realize the independence of the test program set (Test Program Set) development of the automatic test system and the hardware platform, and to reflect the convenience, flexibility, safety and advanced nature of the system design. In the design of the software information model, emphasis is placed on system reconstruction or reorganization, which can be dynamically reorganized according to the tested object or the test process, reducing the cost of system reorganization.
1. VITE standard architecture analysis Virtual instrument test environment VITE adopts an open object model drive structure (Model Driven Architecture), which fully supports various software interface standards in the field of product testing to achieve portability and reusability of software components , Interchangeability, interoperability. The standard system is shown in Figure 1.

Figure 1 Standard framework of virtual instrument test environment

In the entire standard system, according to the characteristics of product testing, it is divided into two levels of frames, namely the information frame and the system frame. All relevant component standards are hung on the frame soft bus in the form of plug-and-play functional modules.
Various information processing in the product testing process revolves around the information framework, including test demand modeling data, test program documentation, in-machine test data, diagnosis and maintenance data, instrument resource data and data exchange format data. The key is the core test information model (Core Test Information Model) defined in the IEEE 1226 standard, which fully describes the test, test description, test requirements and other information entities in the field of wide-area testing. Each component standard is based on CTIM, and completes the expansion of CTIM according to its own characteristics, so as to customize it to different application fields.
The specific test implementation revolves around the system framework, including various resource management services, runtime services, instrument drivers, and diagnostic processing services.
The system framework is responsible for providing information sources to the information framework and is the provider of the information. The information framework sends information collection commands to the system framework according to product testing requirements, and receives and processes information.
The so-called framework is essentially a software environment designed to simplify application development and system management in special application areas. Looking at this standard framework from another perspective, the framework is a kind of middleware at the software level, which is located above the operating system and under the specific test application. Figure 2 shows the comprehensive set of standards in the ABBET Test Foundation Framework.

Figure 2 ABBET test basic standard framework

The standardized framework allows test applications and tools to be supported on heterogeneous platforms implemented on top of ABBET framework services. These standards are organized around three axes representing test subjects, test resources, and test environments.
The test subject standard represented by the horizontal axis in the figure supports the acquisition and reuse of test subject information. The test subject information captures the description of the test subject design and test requirements. These descriptions can avoid secondary development during the initial development, maintenance, and test application relocation process. The test subject information also includes diagnostic knowledge, which can be accessed during the test.
The test resource standard represented by the vertical axis applies to test resources and information. Test resource control standards support access to system services such as instrument configuration and data acquisition. The test resource information standard supports the specification of test application resource requirements and test instrument capabilities. These standards support the adjustment of test applications to adapt to the modification of test equipment configurations.
The environment-related standards indicated by the oblique axis support the interchange and relocation of test applications between heterogeneous test environments. Test information is exchanged in a neutral, implementation-independent format, which is suitable for data import and export services.
2. The architecture of the open virtual instrument test environment implemented by VITE contains a variety of standard open software interface relationships. Software function modules realize information exchange through these interfaces, and these function modules with standard interfaces constitute the basic testing framework.
The realization of VITE is based on object-oriented components. According to the principles of information framework and system framework, several functional components are designed and implemented. The specific structure is shown in Figure 3.

Figure 3 VITE composition structure

A component is a well-defined independent reusable binary code, which can be some functional modules, encapsulated object classes, software framework, software system model, etc. The "component" in the current object-based component software architecture refers to the binary form of code and data that can be easily inserted into languages, tools, operating systems, and network software systems.
The soft bus is also called the object bus or ORB (Object Request Broker), and its purpose is to provide a transparent communication channel between components or between component users and component providers. The application execution, diagnostic display, test system and other components in the figure are "software integrated circuits (ICs)" connected to the soft bus.
The soft bus is the core of connecting application programs, various objects, services, and object tool sets. It can separate the various component object elements in an orderly manner to achieve distributed software integration and plug-and-play applications. It includes two relations at two levels: 1). The relationship between the "definition" of object methods and services and their "implementation". Through the interface definition language OMG IDL, we can obtain standardized, general object methods and service definitions. With the help of a soft bus, these definitions can be truly implemented in any programming language or code module. This division is helpful for specific software code interchange, programming language interchange, and version interchange. 2). The relationship between the request "client" and the response "server". Client requests for other object methods and services are not directly passed to the requested server, but are transferred to the soft bus. The bus monitors the location and status of the server and determines the service binding method. This relationship helps to distribute Objects are logically integrated across platforms and protocols.
These two relationships can ensure that components communicate through the bus and solve interoperability problems between components. Each component is connected to the bus through a component communication unit (also called an adapter). The adapter component solves the problem of interoperability and data exchange between components that do not know each other. The data component object sent from the adapter to the bus can be automatically recognized by any other adapter, and during the installation of the data component object, the installer can make appropriate adjustments to change the function and structure of the service component to adapt to the new requirements. User interface components provide presentation services, and service components provide functional services.
Combined with the division of the VITE standard architecture described in Section 2 and the relationship between the test subject, test resources, and test environment, the implementation of the entire VITE is divided into five conceptual layers.
The first layer is the test information layer, which mainly describes the product to be tested to obtain information about product design and maintenance testing, as well as the special needs of its testing. The model editing component in Figure 3 mainly completes this layer of functions.
The second layer is the test requirements and strategy layer, which provides standard information entities for UUT (under test) test requirements, test modes, and diagnostic knowledge. Its purpose is to generate efficient test procedures and reliable data. The application execution components, diagnostic engine components, database engine components, etc. in FIG. 3 mainly complete the functions of this layer.
The third layer is the user application layer, which is mainly used to help develop TPS programs and defines the operation interface corresponding to test execution. Test execution includes test selection, test sequence selection, diagnostic interaction, access to user interface components, and access to data logs and files operating. The application execution component and diagnostic display component in Fig. 3 mainly complete the functions of this layer.
The fourth layer is the test resource management layer, which provides the basic interface for comprehensive management of test system resources and supports the ability to perform independent ATE tests under a specific ATE condition. Its purpose is to allow instruments and different types made by different manufacturers The instrument can be used in the same test procedure to complete their respective functions. The COTS test language component in Figure 3 mainly completes this layer of functions.
The fifth layer is the instrument drive (control) layer. This layer mainly provides various bus standards and instrument interfaces that ATE can use, such as IEEE488, SCPI, VISA, IVI and so on. The COTS instrument driver component in Figure 3 mainly completes this layer of functions.
3. VITE core information model structure The basic information model of the VITE information framework is based on the core information model structure CTIM. Its goal is to describe the testing of one or more products and provide a way to exchange test information between different systems. The description can be independent of the tester, which can support test reuse between different platforms and environments.
The core test information model is an information model that describes test behavior. It must have the following functional characteristics:
a) Describe the expected product behavior characteristics

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