Hardware-in-the-Loop Simulation (HILS)
Contracting Agency: FDOT
Principal Investigator: Prof. Kenneth G. Courage
Traffic simulation has become an increasinglypractical approach to estimation of performance measures for all typesof highway facilities. Simulation is used to some extent in mostdistricts to address unusual traffic control problems that are notamenable to more simplistic analytical treatments. The principallimitation of simulation models has, up to this point, been the rigidemulation of basic traffic control equipment and mechanisms,accomplished by internal routines within the simulation model itself.This limitation has placed severe constraints on the utility oftraffic simulation as a problem solving approach.
Recently a new class of devices has beendeveloped to allow actual traffic control equipment to replace thecontroller emulation built into a traffic simulation model. The“Controller Interface Device” (CID) opens new horizons for the use oftraffic simulation as a problem-solving tool.
Figure1 HILS system
A simplified overview of thehardware in the loop concept is shown here. The simulationmodel, running in real time, communicates with theController Interface Device(CID) using an industry standard interface. For each second ofoperation, the simulation model tells the CID what detectors areoccupied and asks for the state of each signal phase (red, yellow orgreen). The CID is connected to a standard traffic-actuatedsignal controller by the same cables that would normally connect thecontroller to the detectors and signal displays in the field.The CID passes the detector status from the simulation software to thecontroller hardware. It also passes the signal display statusfrom the controller hardware to the simulation software. By thismethod, the CID is able to connect the abstract process of simulationto the real-world process of traffic control.
Recognizing thepotential of this breakthrough in technology, the Florida Departmentof Transportation (FDOT) has initiated a project to identify andexplore potential areas of application that could support the FDOTmission. The University of Florida Transportation Research Centerperformed this work. The specific objectives were to facilitate theimplementation of hardware in the loop simulation in Florida, and todevelop guidelines for future deployment by FDOT.
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