Research And Design Of Six-Phase Traffic Signal Controller Based On Embedded System

At present, the majority of the urban intersections in China are controlled by two-phase and four-phase traffic signal controllers, which are mostly based on 8/16 bit processors. The low capability of those processors results in many drawbacks, such as insufficient functions, single control schemes. Besides, operating system is unable to be transplanted into those processors, and it is difficult to realize complicated multi-tasking. So they can no longer meet the demands of current traffic situation. Aiming at the deficiencies of those traffic signal controllers, this paper implements the whole design of a six-phase traffic signal controller based on LPC2478 ARM processor of NXP corporation andμC/OS-Ⅱoperating system. This traffic signal controller was developed on the basis of new requirements of actual road intersections, to be exact, the new requirements include six-phase control, complex control scheme, being able to take vehicle actuated control on the basis of real-time traffic situation.Firstly, through the analysis of traffic conflict points in a typical mixed-traffic road intersection, this paper introduced the six-phase traffic control solution and analyses several traffic control scheme. Then, the overall design of system was given and four control modes were designed for the traffic signal controller, or rather, vehicle actuated control, multiple intervals fix-time control, manual control and flashing yellow control.Secondly, according to the functional requirements, the design of hardware and driver layer were accomplished in detail, including the option of processor and memory, the drive and green conflict detection circuit and so on. In addition, the board support package was designed for the hardware.Thirdly, according to ARM's operating mode and instruction set,μC/OS-Ⅱoperating system was transplanted into the hardware platform. It not only enhanced the ability of multi-tasking to ensure real-timing, but also effectively improved software development efficiency and reduced the design difficulty.Finally, this paper analysed the assignment layer on the basis of modular software design, and the detailed process for software tasks was given. The finite state automata model was applied in researching control task algorithm, and a message-driven software architecture was built for the control tasks. In the end, the concrete realization of all application tasks was given.Unit testing for task software was conducted and the process and role of it was described in this paper. Additionally, the function testing of traffic signal controller was carried out in the hardware system test board. The results show that the signal controller designs functional properly and works steadily, which meets the current needs of the majority of the traffic intersection. This design not only has high practical value, but also made a successful exploration in the field of traffic control for the embedded platform of LPC2478 andμC/OS-Ⅱ, with some reference value.