Software-in-the-loop Simulation Research Articles

Investigation on the exit phase controls for emergency vehicle preemption

Many traffic signal control systems used in the U.S. have Emergency Vehicle Preemption (EVP) systems that change traffic signals to clear an intersection for emergency vehicles. However, one of the challenges of implementing EVP under coordinated-actuated signal systems is selecting the best recovery method at the end of preemption such that disruptions to normal traffic signal operations may be minimized. To this end, there have been lots of research efforts which have compared the performances of various transition methods after EVP operations using microscopic traffic simulation models, Hardware-in-the-loop Simulations (HILS) or softwarein-the-loop simulations (SILS). However, few attempted to implement exit phase controls during the EVP operations, which is available in recent advanced traffic controllers such as the ASC/3-2100 traffic controller. This paper was intended to report the evaluation results of two types of exit phase control — (i) fixed exit phase control and (ii) dynamic exit phase control during EVP operations. The evaluation was conducted using a HILS on an urban corridor including four coordinated-actuated signals along Lee Jackson Memorial Highway in Chantilly, Virginia. The evaluation results indicated that (i) the use of fixed exit phase control should be considered in the development of EVP strategies as it is able to minimize disruptions due to the EVP operation, and (ii) the dynamic exit phase control is capable to give an additional benefit during EVP operations. In the evaluation, the fixed and dynamic exit phase control reduced network-wide average delay time in seconds per vehicle to 2.8% and 4.5% over no exit phase control case, respectively.

Hardware-in-the-Loop Simulation Evaluation of Adaptive Signal Control

Increasingly, adaptive signal control and other nontraditional solutions are being implemented in an attempt to improve signal system efficiencies, reduce congestion, enhance signal control responsiveness to incidents, and reduce signal-retiming costs. However, neither field nor simulation studies alone have proven sufficient to evaluate such systems. To overcome the limitations of field data or simulation-only studies, hardware-in-the-loop simulation (HILS) or software-in-the-loop simulation (SILS) may be used. HILS and SILS provide a means for realistic testing, under controlled and repeatable conditions, of signal strategies not directly emulated in a simulation model. This paper presents the initial findings of a HILS evaluation of ACTRA [i.e., semiactuated, coordinated, time-of-day (TOD)] and adaptive signal control on an 11-intersection arterial section. The HILS test bed generally provides a reasonable representation of both TOD and adaptive signal control performance. However, the adaptive a.m. HILS results contain some unexpected behaviors not observed in the field. The initial findings of the signal control comparison indicate that during peak conditions both control strategies provide similar performance; however, during the hours bordering the peaks, adaptive control is likely able to provide control more tailored to the current conditions.

Real Time Software-in-the-Loop Simulation for Control Performance Validation

This paper illustrates an effective real-time software-in-the-loop (SIL) simulation technique for control design performance validation through two case studies in automotive systems: electric power steering (EPS) control and drive control for a switch reluctance motor (SRM) powered by a fuel cell. This technique, if implemented appropriately, will be able to shorten the prototyping time for control system research and development in both academic and industrial areas. The two cases presented involve complicated dynamics: road/tire steering dynamics and chemical/electrical dynamics in a fuel cell, for which software packages are available to simulate. Therefore, for the purpose of steering and SRM drive control performance validation, successful real-time simulation is desired through interfacing with these software, i.e. making software package in the loop. The case studies presented in this paper demonstrate the effectiveness of this concept. The presented real-time SIL simulation is conducted on a two-node computer platform engineered by RT-Lab, operating in fixed-step real time. Comparison between real-time and off-line simulation is also presented.

Development of SILS and RCP for OSEK-OS based ECU

This paper presents the Matlab/Simulink-based Software-in-the-Loop Simulation (SILS) tool for OSEK-OS based ECU. The SILS tool has the capability for temporal and functional simulations of control systems. The temporal behavior of a control system is mainly dependent on the implemented software and hardware such as the real-time operating system (OSEK-OS), the target CPU, and the communication protocol. The SILS components with temporal attributes are specified as tasks, task executions, real-time schedulers (OSEK-OS scheduler), and real-time networks. Methods to realize these components in graphical block representations are investigated with Matlab/Simulink. Furthermore, in order to achieve a seamless development process from SILS to Rapid Control Prototyping (RCP), the SILS block set is designed to support automatic code generation in C codes without tool changes and block modifications.

Parallel and Sequential Job Scheduling in Heterogeneous Clusters: A Simulation Study Using Software in the Loop

The task of designing and optimizing job scheduling algorithms for heterogeneous computing environments requires the ability to predict scheduling performance. The complexity of heterogeneous scheduling issues re quires that the experiments devised to test a scheduling paradigm to be both flexible and extensive. Experimen tally determined models for the prediction of job execu tion times on both sequential and parallel computing resources are combined with the implementation of a novel scheduling algorithm and a software-in-the-loop (SWIL) simulation. The result is a potent design and analysis approach for job scheduling algorithms and implementations intended for heterogeneous environ ments. This paper develops the concepts, mechanisms, and results of a SWIL design and analysis approach. The merits of this approach are shown in four case stud ies, which determine overhead, scheduling performance, and the impact of preemption and priority policies. These case studies illustrate the contributions of this research in the form of a new parallel job scheduling algorithm for heterogeneous computing and in the novel application of SWIL simulation to the analysis of job scheduling systems.