SUPERVISORY CONTROL AND FAILURE DIAGNOSIS OF DISCRETE EVENT SYSTEMS: A TEMPORAL LOGIC APPROACH

Discrete event systems (DESs) are systems which involve quantities that take a discrete set of values, called states, and which evolve according to the occurrence of certain discrete qualitative changes, called events. Examples of DESs include many man-made systems such as computer and communication networks, robotics and manufacturing systems, computer programs, and automated trac systems. Supervisory control and failure diagnosis are two important problems in the study of DESs. This dissertation presents a temporal logic approach to the control and failure diagnosis of DESs. For the control of DESs, full branching time temporal logic-CTL* is used to express control specifications. Control problem of DES in the temporal logic setting is formulated; and the controllability of DES is defined. By encoding the system with a CTL formula, the control problem of CTL* is reduced to the decision problem of CTL*. It is further shown that the control problem of CTL* (resp., CTL{computation tree logic) is complete for deterministic double (resp., single) exponential time. A sound and complete supervisor synthesis algorithm for the control of CTL* is provided. Special cases of the control of computation tree logic (CTL) and linear-time temporal logic (LTL) are also studied; and for which algorithms of better complexity are provided. For the failure diagnosis of DESs, LTL is used to express fault specifications. Failure diagnosis problem of DES in the temporal logic setting is formulated; and the diagnosability of DES is defined. The problem of testing the diagnosability is reduced to that of model checking. An algorithm for the test of diagnosability and the synthesis of a diagnoser is obtained. The algorithm has a polynomial complexity in the number of system states and the number of fault specifications. For the diagnosis of repeated failures in DESs, different notions of repeated failure diagnosability, K-diagnosability, [1,K]-diagnosability, and [1,1]-diagnosability, are introduced. Polynomial algorithms for checking these various notions of repeated failure diagnosability are given, and a procedure of polynomial complexity for the on-line diagnosis of repeated failures is also presented

GROUND FAULT DIAGNOSTICS FOR AUTOMOTIVE ELECTRONIC CONTROL UNITS

An electronic control unit (ECU) with a floating ground is not able to receive or transmit messages or participate in controller area network (CAN) communication. The absence of any ECU, either temporarily or permanently, negatively impacts vehicle functionalities. The offset ground, which by itself won’t affect bus functionalities if the grounding resistance is small, however, may evolve into a floating ground or behave similarly if the resistance is large. In this work, the correlation among ground faults, either offset or floating, and CAN bus voltage or messages are analyzed based on the equivalent circuit models and the bus protocol. A voltage-based solution to detect ground faults is proposed. With the help of bus messages, both faults can be isolated at the ECU level. Considering the inherent system delay between the message fetching and voltage measurement, a normalized voltage-message correlation approach with the bus load estimation is developed as well. All proposed approaches are implemented to an Arduino-based embedded system and validated on a vehicle frame

Modulation of Excited State Property Based on Benzo[a, c]phenazine Acceptor: Three Typical Excited States and Electroluminescence Performance

Throwing light upon the structure-property relationship of the excited state properties for next-generation fluorescent materials is crucial for the organic light emitting diode (OLED) field. Herein, we designed and synthesized three donor-acceptor (D-A) structure compounds based on a strong spin orbit coupling (SOC) acceptor benzo[a, c]phenazine (DPPZ) to research on the three typical types of excited states, namely, the locally-excited (LE) dominated excited state (CZP-DPPZ), the hybridized local and charge-transfer (HLCT) state (TPA-DPPZ), and the charge-transfer (CT) dominated state with TADF characteristics (PXZ-DPPZ). A theoretical combined experimental research was adopted for the excited state properties and their regulation methods of the three compounds. Benefiting from the HLCT character, TPA-DPPZ achieves the best non-doped device performance with maximum brightness of 61,951 cd m−2 and maximum external quantum efficiency of 3.42%, with both high photoluminescence quantum efficiency of 40.2% and high exciton utilization of 42.8%. Additionally, for the doped OLED, PXZ-DPPZ can achieve a max EQE of 9.35%, due to a suppressed triplet quenching and an enhanced SOC

GM R&D and Planning

Abstract — We study failure diagnosis of timed discreteevent systems modeled as dense timed-automata for which reachability is decidable [1], [6]. Failure diagnosis of such systems was first studied in [21], assuming that a diagnoser has partial observation of events but can measure (or “observe”) time perfectly. In this paper we relax the latter requirement since in practice time cannot be measured precisely. Thus in our setting we have partial observability of events as well as of “time”. We model the observability of time based on a digitalclock of finite precision and of finite drift, i.e., the clock that a diagnoser uses to measure time ticks every [ ∆ ± δ] units of time. We show that the “discrete-time behavior ” observed using such a clock is regular, i.e., can be represented using a finite (untimed) automaton. In our analysis we allow the non-failure behavior to be also represented as a separate dense timedautomaton that is deterministic (also decidable), which can be viewed as another extension. We show that the verification of diagnosability (ability to detect specification violation within a bounded delay) as well as the off-line synthesis of a diagnoser for a diagnosable system is decidable by reducing the problem to the untimed domain. The reduction to the untimed domain also suggests an effective method for an on-line diagnosis

Decentralized Control of Discrete Event Systems with Specializations to Local Control and Concurrent Systems

The decentralized supervisory control problem of discrete event systems under partial observation is studied in this paper. The main result of the paper is a necessary and sufficient condition for the existence of decentralized supervisors for ensuring that the controlled behavior of the system lies in a given range. The contribution of the paper in relation to prior work is as follows: (i) Our setting of decentralized control generalizes the prior ones; (ii) We present an alternative approach for solving the decentralized control problem, which leads to computational saving for concurrent systems and certain other systems; (iii) Our generalized formulation and its solution lets us extend several of the existing results reported in [1, 10, 6, 7, 11]. The results of our paper are illustrated by an example of a simple manufacturing system

Model Checking For Fault Explanation

Abstract — Model checking is very effective at finding out even subtle faults in system designs. A counterexample is usually generated by model checking algorithms when a system does not satisfy the given specification. However, a counterexample is not always helpful in explaining and isolating faults in a system when the counterexample is very long, which is usually the case for large scale systems. As such, there is a pressing need to develop fault explanation and isolation techniques. In this paper, we present a new approach for the fault explanation and isolation in discrete event systems with LTL (linear-time temporal logic) specifications. The notion of fault seed is introduced to characterize the cause of a fault. The identification of the fault seed is further reduced to a model checking problem. An algorithm is obtained for the fault seed identification. An example is provided to demonstrate the effectiveness of the approach developed. I