| Powered by the rapid advance of computer, network, and sensor/actuator technologies, distributed real-time systems that continually and autonomously control and react to the environment have been widely used. The combination of temporal requirements, concurrent environmental entities, and high reliability requirements, together with distributed processing make the software to control these systems extremely hard to design and difficult to verify.; In this work, we developed a simulation-based software development methodology to manage the complexity of distributed real-time software. This methodology, based on discrete event system specification (DEVS), overcomes the "incoherence problem" between different design stages by emphasizing "model continuity" through the development process. Specifically, techniques have been developed so that the same control models that are designed can be tested and analyzed by simulation methods and then easily deployed to the distributed target system for execution. To improve the traditional software testing process where real-time embedded software needs to be hooked up with real sensor/actuators and placed in a physical environment for meaningful test and analysis, we developed a virtual test environment that allows software to be effectively tested and analyzed in a virtual environment, using virtual sensor/actuators. Within this environment, stepwise simulation methods have been developed so that different aspects, such as logic and temporal behaviors, of a real-time system can be tested and analyzed incrementally.; Based on this methodology, a simulation and testing environment for distributed autonomous robotic systems is developed. This environment has successfully supported the development and investigation of several distributed autonomous robotic systems. One of them is a "dynamic team formation" system in which mobile robots search for each other, and then form a team dynamically through self-organization. Another system is a scalable robot convoy system in which robots convoy and maintain a line formation in a coordinated way. |
