Timed Synthesis Control Approach for Tolerant-Fault Control of Discrete Event Systems (DES)

Abstract

This paper presents an approach of a safe control synthesis of Timed Discrete Event Systems, based on timed properties. This synthesis aims to realize a fault-tolerant control during the detection of sensor faults. To establish this synthesis, the proposed approach relies on the modularity of the manufacturing systems to avoid the combinatorial explosion recurrent to several approaches. An example of a manufacturing system illustrates our remarks.

Two Cases of Study for Control Reconfiguration of Discrete Event Systems (DES)

“…The method is based on defining two separate models of the system plant. The first one describes the normal behavior of the system and the second model describes its faulty behavior where a timed information replaces each faulty sensor through a time-based estimator (Tahiri et al 2019). This, in order to determine a centralized controller that manages the two system' behaviors as well as the switch between them (figure 2).…”

“…Therefore, determining the plant faulty behavior model (plant_F) is based on an extension of the practical model presented in (Alexandre Philippot 2006) where timed events are added. In a previous work (Tahiri et al 2019), we discussed a method to include time to DES, we talk about Timed Discrete Event Systems (TDES). A method where time is presented through a clock and considered as an event, which makes the modelling phase by Finite State Machines (FSM) a simple task.…”

“…In a previous work (Tahiri et al 2018), we proposed a new framework in order to achieve a control synthesis. The approach is based on an extension of the PE models.…”

“…For an implementation purpose, the distributed controllers and the reconfiguration specifications are interpreted under a grafcet language. A method of this interpretation is given in (Tahiri et al 2018) and (Qamsane, Tajer, and Philippot 2016). This system is built using 3D FACTORY I/O simulator (figure 6-a) (https://factoryio.com/).…”

“…The reconfiguration process here consists on leading the MS from its current state (CS) in the normal behavior controller where the fault is detected, thanks to the diagnosis, to a target state (TS) in a faulty behavior controller in order to maintain the MS functioning despite faults. The information lost about a faulty sensor is replaced by a so-called time-based estimator of its functioning (Tahiri et al 2019). The control reconfiguration loop (figure 1) is based on three elements: (1) The Supervisory Control Theory principle (SCT) initiated by Ramadge and Wonham (R&W) in (Ramadge and Wonham 1989).…”