Working Principles and Interface Standards The CAN bus supports message-based operation. Messages can be broadcast to any node at any time and sent to the network. Messages appear in the form of message packets and include four types: data message packets, RTR message packets, error message packets, and overload message packets.
The system design follows the following basic principles in the design of the structure and function of the system: (1) Modular integration: Each signal unit should be convenient for centralized detection and control, and independent of each other. Its physical structure is represented by modular integration, and it appears as a virtual instrument structure in the integration of the system.
(2) Project expansion: Due to the continuous enrichment of automotive instrument functions, test and inspection items and their requirements are constantly changing, which requires considering the scalability of the system and improving the cost-effectiveness of the system. The scalability of the system is reflected in the flexible connection of the system software and hardware and the simulated physical interface and semi-physical interface.
(3) Project programmable: Programmable principles are represented by program groupings such as test items, action sequences, signal types, amplitudes, and inspection accuracy. For various test purposes, the user can flexibly set and program according to the test content requirements.
(4) The test operation interface requires image, simplicity and convenience.
System work requirements (1) Durability: The system performance meets the requirements of durability test, continuous and reliable operation for 72 hours, with reliable anti-jamming capability and self-recovery capability. (2) Compatibility: The system is highly compatible and can be used in conjunction with other automotive test equipment to further conduct comprehensive experiments. (3) working environment: the system's ambient operating temperature is 0 ~ 70 °C, external operating voltage is AC 220V, operating current 5A.
The overall structure of the system is based on system requirements, and the overall structure of the system is as follows. System functions and configuration System configuration and development environment Hardware configuration: The system operation console is a PC (PII, monitor 20'); a camera monitoring system (interface card, camera); LAN system includes bus control device 82C200, 82C250 and other interface adapters and other devices. The overall structure of the system development environment: WINDOWS98 operating system, DELPHI5.0 and assembly tools.
Main function and interface design Through the analysis and summary of the automobile test, the following main functions of the system are determined: (1) The pulse speed, vehicle speed, and mileage are simulated to detect the oil pressure, oil volume, water temperature, voltage and indoor Outside temperature signal. Can simulate left and right steering, reverse, lights and more than 20 kinds of switching signals. (2) With program setting function, it can automatically control the magnitude and timing of various types of signals. (3) Perform data query and analysis on input signals to generate test reports.
According to the system function requirements, the design system interface, for example, the specific main functions are described as follows: system maintenance: password, system parameter settings, file management and so on. User management: test project registration, user, car registration. Test plan: The full set of plans, program combinations, and corresponding databases for this test project can be set arbitrarily, including test specifications and requirements. Test procedure: Test according to the test plan, can be automatically tested under the guidance of the guide. Including the principles and methods of automotive testing. The test procedure is automatic and flexible.
System Simulation: Simulate all test processes according to the test plan. Data query: The test data can be classified and queried. Analysis report: According to the test principle and method, the test data is analyzed through charts and other forms, and a test report is generated. Instrument monitoring: Real-time monitoring of the instrument's working condition through the camera on the instrument cluster. User assistance: Provides system overview, installation guides, and usage instructions.
Conclusion With the adoption of distributed control system design and the adoption of CAN bus technology, the automotive instrument cluster simulation simulation and performance experiment system achieves high reliability of automobile testing and low-cost system development. In addition, the high efficiency of the DELPHI development environment provides a solid foundation for system integration. Due to the better solution to the problems of distributed control systems, the system application level reaches a new level.
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