Design Of The Distributed Test Bus System Based On Clock Synchronization

Along with the development of network and test technology, the technology combining Ethernet and fieldbus is widely used in flight test of aircraft and ships test. It becomes the development trend in the test field as a result of its flexible framework and its reliability and controllability for the real-time data communication.The realization of distributed bus architecture and real-time communications are the most important part of the realization of such distributed test bus system.However, the technology of such distributed test bus system is non-disclosed, so the research of the test-bus system in the paper is more theoretical and practical.First of all, the paper based on study of the existing test-bus system achieves the realization of the distributed bus system by using the quite advanced distributed bus architecture. This advanced architecture designed in the paper uses fieldbus to realize the inside bus and Ethernet to realize the outside bus which is used to control and integrate the inside bus network.The distributed bus architecture greatly enhances the system's expansibility.Secondly, the communication protocol and clock synchronization technology are the basic guarantees for the real-time communication of the system, so it is necessary to solve these two problems.The paper uses the most reliable real-time communication protocol currently: Ethernet Powerlink protocol. And the paper implements the protocol by using the embedded processors of the FPGA. This design greatly increases the reliability and stability of communications of the systemThe paper proposes a relative-clock synchronization algorithm by deep studying IEEE1588 clock synchronous protocol.The system has achieved theμs-level clock synchronization by using this algorithm which guarantees the system's determinism and correspondence timeliness.Thirdly, in the process of system's realization, the paper implements the reasonable tasks-division which based on the I/O principles and tasks'inner-structure.And the paper carries out the multitask scheduling based on the tasts'priority for the guarantee of system's highly real-time requirements and each tast's prompt response.Finally, the paper carries out the test of the distributed test bus system.The test verified that: The system's architecture, proposed in the paper is nimble and reasonable; The communication protocol is stable and reliable; The precision of clock synchronization algorithm satisfies the system timeliness request; The task scheduling technology used in the system is simple, real-time and effective. Now the system already has been used in application of the airplane flight test successfully and has achieved nice performance.