Based on CAN bus traffic lights dynamic adjustment system design (1)

Domestic traffic lights traffic control system traffic light switch time widely used fixed or segmented change interval, or the traffic control centres in accordance with the traffic situation adjustment interval, not according to actual traffic conditions be dynamically switched, nor be able according to road conditions prior intervention to prevent the deterioration of the traffic.

In extreme cases, there may be a red light in the direction of the car, no cars stop in the direction of the prevailing situation. green light This inefficient, heavily dependent on traffic control sector efficiency, and generally only in traffic deterioration after may intervene, cannot advance prevention. This article presents an approach based on can bus traffic lights dynamic adjustment system, which according to actual traffic conditions in real time to adjust the traffic light, you can reduce the chance that security road congestion, traffic flow.

1 overall design scheme

The overall design of the programme as shown in Figure 1.

Figure 1 (a) for each intersection traffic light controller, loop and traffic lights between the dotted line represents both the linkage relationship of ask. Figure 1 (b) to the system diagram. Each intersection traffic light controller via CAN bus connection to the control center. In General, four loop vehicle detectors are installed at the crossroads of four direction, when the vehicle after the loop detector, produces high level signal, the signal is fed to the controller. Controller for this information to count, and real-time control traffic lights over time, the road to the best prevailing conditions; at the same time controller via CAN bus calculated related data transmitted to the control center and related sectors. Control Center is available depending on the situation made public, but also can send instructions to a controller, remote manual intervention. The system has real-time high, objective and accurate benefits, but also can reduce the labor intensity of traffic control sector.

2 can bus traffic dynamically adjust system hardware design

System hardware consists of a loop detector, controller and CAN transceiver modules.

Which ring coil detector can be used at present, some sections have been laying the product, this can reduce capital investment.

2.1 controller design

Controller adopts ST STR710 company as the central processing unit.

STR710 with 14 external interrupt input, 256 KB FLASH memory, 64 KB internal RAM, 5 timer, more appropriate to deal with multiple external interrupt sources need to be addressed. Controller circuit diagram shown in Figure 3. P2.5 through the optical coupling is connected to the DI-MAX485 to control the conversion of traffic lights; P2.4 through optical coupling attached to the end of DE MAX485 to MAX485 to send function.

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