Concept of Smart Signal Heads
We are doing a project in our laboratory which called “Smart Signal Head” in road traffic signal control. The base of the idea is that we place a PLC (but it could be whatever computer unit) into the signal head which can switch the signal lamps bulbs and keep in touch with the remote control for further leading functions. The biggest advantage of the concept is that the huge quantity of the long, multi-wired cables can be replaced with one single UTP cable. Since the logical module is situated within the signal head, the cable connection between the signal head and the module means centimeters. This system results significant cost savings.
Universal traffic control
Traffic control with Smart Signal Heads
Another benefit of the smart signal head system is the simple applicability for special cases like traffic signalization during road construction. Moreover, the installation is easier and faster. We set up our smart system with Siemens LOGO! 12/24 RCE PLCs, Actros VTC 3000 traffic control unit and Siemens/Elba LED signal heads. The communication works through TCP/IP protocol. There are UTP cables between the modules.
The safety critical functions of the system:
- recognition of prohibited (conflicting) signals - in that case the flashing yellow mode is activated,
- in case of inside errors it switches to fail-safe position state (depending on the error it will be flashing yellow light or dark mode,
- checking the right green light combination, i.e. prohibited greens cannot be on at the same time (check the existence of the intermediate times),
- checking the brake of the signal lamps
As the PLC program contains itself the flashing yellow function, false signals cannot occur (in case of error the system switch immediately to the flashing yellow light mode).
The specialty of this technology is represented by the method of the safety critical functions. The continuous checking of the signal heads must be ensured by data transmission.
- replace the PLCs with microcontoller
- change the TCP/IP protocol to UDP or serial communication
- increase the intelligence of the signal heads to a higher level where they can work without any main traffic control unit.