IEEE Robotics and Automation Society, Technical Committee on Discrete Event Dynamic Systems (DEDS TC)

The IEEE Robotics and Automation Society DEDS Technical Committee is chaired by Professor Tarek Sobh, Department of Computer Science and Engineering, University of Bridgeport; and Professor Beno Benhabib of the Department of Mechanical Engineering, University of Toronto.

Recent committee activities include:

Discrete Event and Hybrid Systems in Robotics and Automation

Hybrid systems, in which digital and analogue devices and sensors interact over time, is attracting the attention of researchers. Representation of states and the physical system condition includes continuous and discrete numerics, in addition to symbols and logical parameters. Most of the current robotics, automation, and intelligent systems problems, as well as problems in other domains, fall within the description of hybrid systems. There are many issues that need to be resolved, among them, definitions for observability, stability and stabilizability, controllability in general, uncertainty of state transitions and identification of the system.

The underlying mathematical representation of complex computer-controlled systems is still insufficient to create a set of models which accurately captures the dynamics of the systems over the entire range of system operation. We remain in a situation where we must tradeoff the accuracy of our models with the manageability of the models. Closed-form solutions of mathematical models are almost exclusively limited to linear system models. Computer simulation of nonlinear and discrete-event models provide a means for off-line design of control systems. Guarantees of system performance are limited to those regions where the robustness conditions apply. These conditions may not apply during startup and shutdown or during periods of anomalous operation.

Recently, attempts have been made to model low and high-level system changes in automated and semi-automatic systems as discrete event dynamic systems (DEDS). Several attempts to improve the modeling capabilities are focused on mapping the continuous world into a discrete one. However, repeated results are available which indicate that large interactive systems evolve into states where minor events can lead to a catastrophe. Discrete event and hybrid system formulations have been used in many domains to model and control system state changes within a process. Some of the domains include: Manufacturing, Robotics, Autonomous Agent Modeling, Control Theory, Assembly and Planning, Concurrency Control, Distributed Systems, Hierarchical Control, Highway Traffic Control, Autonomous Observation Under Uncertainty, Operating Systems, Communication Protocols, Real-Time Systems, Scheduling, and Simulation.

A number of tools and modeling techniques are being used to model and control discrete event systems in the above domains. Some of the modeling strategies include: Timed, untimed and stochastic Petri Nets and State Automata, Markovian, Stochastic, and Perturbation models, State Machines, Hierarchical State Machines, Hybrid Systems Modeling, Probabilistic Modeling (Uncertainty Recovery and Representation), Queuing Theory, and Recursive Functions.

The IEEE R&A DEDS TC attempts to serve the robotics and automation community by organizing and focusing DEDS-related activities and making different resources available for the DES-related projects within the R&A domain.

Selected Committee-Related Publications:

Journal Papers

T. M. Sobh, J. C. Owen, K. P. Valavanis, and D. Gracanin, ``A Subject-Indexed Bibliography of Discrete Event Dynamic Systems.'' In IEEE Magazine on Robotics and Automation, Vol. 1, No. 2, June 1994.

T. M. Sobh, J. C. Owen, and M. Dekhil, ``A Dynamic Recursive Approach for Autonomous Inspection and Reverse Engineering.'' In Journal of Robotics and Autonomous Systems, Special Issue on Discrete Event Systems in Robotics and Automation, October 1994.

Conference Papers

T. M. Sobh, P. Sloan, and M. Dekhil, ``A Graphical Environment and Applications for Discrete Event and Hybrid Systems in Robotics and Automation''. Submitted to the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 95), Special Session on Discrete Event and Hybrid Systems, Pittsburgh, August 1995.

Snap shots of the graphical DES environment