From TIME-DRIVEN to EVENT-DRIVEN systems
In the day-to-day life of our “man-made” and increasingly computer-dependent world, we notice:
- First, that many of the quantities we deal with are discrete, typically involving counting integers (how many parts in an inventory, how many planes in a runway, how many packets in a buffer).
- Second, that what drives many of the processes we use and depend on are instantaneous events such as the pushing of a button, hitting a keyboard key, or a traffic light turning green.
In fact, much of the technology we have invented and rely on (especially where digital computers are involved) is event-driven: communication networks, manufacturing systems, or the execution of a computer program are common examples. Not only must these systems act as “event coordinators”, but they are also expected to swiftly react to unpredictable events, rapidly adapt to changing conditions, and guarantee their users satisfactory – if not optimal – performance.
In short, all activity in these systems is due to asynchronous occurrences of discrete events, some controlled (like hitting a keyboard key) and some not (like a spontaneous equipment failure). This feature lends itself to the term Discrete Event System (DES). When systems combine both time-driven and event-driven behavior, we then deal with Hybrid Systems.
The time-driven paradigm for the modeling and analysis of dynamic systems is founded on the centuries-old theoretical framework provided by differential (or difference) equations. In this paradigm, time is an independent variable and, as it evolves, so does the state of the system. Conceptually, there is an underlying “clock” and with every “clock tick” a state update is performed, including the case where no change in the state occurs. Methodologies for sampling, estimation, communication, control, and optimization are also founded on the same time-driven principle. The digital technological advances of the 1970s and beyond have facilitated the implementation of this paradigm with digital clocks embedded in hardware and used to drive the collection of data or the actuation of devices employed to control various processes.
In a world increasingly networked, wireless, and involving large-scale distributed systems, the universal value of this point of view has understandably come to question. The event-driven paradigm offers an alternative, complementary look at control, communication, and optimization. The key idea is that a clock should not be assumed to dictate actions simply because a time step is taken; rather, an action should be triggered by an “event” specified as a well-defined condition on the system state or as a random state transition. Naturally, defining the proper “events” requires more sophisticated techniques compared to simply reacting to time steps.
RESEARCH IN DISCRETE EVENT AND HYBRID SYSTEMS
- Physical and operational complexity (combinatorial explosion in many cases)
- Stochastic complexity: unpredictability, uncertainty
- High-performance technological requirements
CODES Lab activities cover a wide spectrum, from basic research to the development of software tools. These activities include:
- Design and real-time control of network systems (sensor networks, transportation systems, cooperative robotic teams)
- Event-driven control and optimization
- Decision support systems with rapid-learning features
- Intelligent simulation tools
- Distributed optimization algorithms for multi-agent systems and networks
- Control and optimization of energy-aware systems (wireless sensor networks, Electric Vehicles)
- Developing a on open cloud platform for Smart Cities
- Control and optimization of Connected Autonomous Vehicles
- Transitioning from selfish (user-centric) to social (system-centric) optimal resource management
For more information, visit Research Projects, Journal Publications, and various interactive demos and video clips of CODES Lab experiments involving wireless sensor networks, multi-agent robotic systems, and Smart City projects at the CODES Lab home page.
CODES Lab members are also part of the BU Robotics Lab, a new facility with state of the art equipment for interdisciplinary research.
INFORMATION FOR PhD PROGRAM APPLICANTS:
Graduate students who join the CODES Laboratory have strong analytical skills and a background that includes systems and/or control theory or operations research.
All students admitted to the PhD program and joining the CODES Laboratory are awarded full financial support in the form of a Fellowship.
If you are interested in applying for admission to our graduate program and joining the CODES Lab, Center for Information and Systems Engineering (CISE), or the Division of Systems Engineering, please visit Graduate Admission Information.