| Airfield lighting is an important safe facility for the airport. Recently the increasing of airport’s capacity and carrying ability gave great pressure on the maintenance and management of the navigation lamps, and the traditional manual inspection methods cannot meet the requirements now, so it’s necessary to design a single lamp control and monitoring system and realize it.First, the environment for the single lamp control and monitoring system was introduced, and the overall design of the system was finished with the detailed study in the functional requirements. Based on the features of the communication by power line, the whole system was divided into three levels, including the single lamp unit (SLU), the series circuit modem (SCM) and the control unit(CU). Then a failure detection method used in the SLU was detailed descript which is realized by measuring the RMS voltage value of the lamp, and then the functional design of the SCM was obtained.Second, a pulse communication technique was proposed based on the features of the series lighting circuit itself. This technique executed data transferring and receiving only at a specific time slice of the half period with the frequency of50Hz. By communicating intermittently, it’s avoided to transfer and receive data at the time slice with heavy interference, and thus solved the technical difficulty in communicating by power line of series lighting circuit which had inherent serious noise. Then a synchronization method was designed based on the series circuit current. The SLU and the SCM were used in different occasions, so the upstream and downstream carrier signals were modulated in different ways. The demodulation of the signal was achieved by measuring the frequency of the carrier signal with the frequency deduction method, which has the advantages in less computation, less resources consumption and good real-time performance. Communication in the pulse communication technique was achieved with the main circuit cable, so no re-laying communication lines is needed which means the system is cost-effective.Third, a method was described to accomplish communication between each level. The pulse communication technique was adopted in the communication between the SLU and the SCM. According to the functional requirements of the system, a communication protocol was designed. In order to ensure the reliability of the transmission, different error control methods were used in the upstream and downstream communication by their own data characteristics. The RS485interface bus combined with the Modbus protocol was used to accomplish the communication between the CU and the SCMs, and the lamp status inspection, lamp control and feedback status receiving were also detailed described. In addition, the time for the SCM to finish controlling and inspecting the SLUs was estimated which took the most of system’s response time. And our results was well agreed with the actual requirements.Finally, the simulation of the series circuit pulse communication was accomplished with Matlab/Simulink, and the operation test of the single lamp control and monitoring system was obtained in both the laboratory and the real airfield. The simulation results showed that the pulse communication technique can complete signal synchronization quickly and accurately when proper parameter was selected, and the communication had a low BER when the additional noise is limited, which greatly meet the requirements of system. The operation test results showed that the single lamp control and monitoring system can also run accurately and stably in both the laboratory and in the airfield. |
