Session 3: DES Control

Session chair: Klaus Schmidt 

16:30 - 18:00 Wednesday 4th September 2013
16:30 Fault-Hiding Control Reconfiguration for a Class of Discrete Event Systems
Authors: Thomas Wittmann, Jan Richter, Thomas Moor
Abstract: Fault-hiding control reconfiguration aims at hiding a fault from the nominal controller, so that the closed-loop system subject to faults complies as well as possible with the nominal design requirements. This is achieved by suitably influencing the signals between nominal controller and faulty plant using a reconfiguration block. In discrete event systems, the reconfiguration block needs to convert plant events to controller events, and vice versa, such that the self-reconfiguring closed-loop system is non-conflicting, complete, controllable and conforms with the design specifications. In this paper, we discuss the resulting control architecture, state our reconfiguration problem and address the synthesis of discrete event dynamic reconfiguration blocks. To illustrate our results, we provide a running example.
17:00 Synthesizing bounded-delay communication protocols for decentralized discrete-event systems
Authors: John Daniel Maguire, Laurie Ricker
Abstract: A strategy for synthesizing communication protocols for a given upper-bounded delay d is proposed. Although the strategy is illustrated for the decentralized control domain, it is straightforward to adapt this strategy to decentralized diagnosis and prognosis. Previous work in the control domain has examined circumstances when all observations are communicated, under conditions of bounded delay, as well as determining whether or not a synchronous communication protocol is robust w.r.t. a given bounded delay. We are interested, without resorting to fully timed models, in the direct synthesis of communication protocols for a given upper-bounded delay [0,d]. 
17:30 Algebraic Synthesis for Online Adaptation of Dependable Discrete Control Systems
Authors: Christian Hillmann, Olaf Stursberg
Abstract: Common practice in industrial design of discrete controllers as well as in most synthesis procedures advocated for discrete control in academia is to create the control logic and to transfer it into a PLC language before start-up. Changes in the operational constraints of the controlled process (e.g. of available resources, nominal set-points, occurrences of failures) have to be accounted for by dedicated alternative routines, i.e. dependability is restricted to variations which are envisaged during design. In contrast, the approach proposed in this paper operates online on an uncontrolled model process model to compute a control strategy that is adapted to the current set of constraints. By using algebraic computations largely resembling techniques for discrete-time continuous-valued controllers, a perceived process variation (including newly defined control-goals) are first assessed with respect to the existence of a feasible successful control strategy, before such a dependable strategy is computed.