In this paper, an observer-based adaptive threshold is developed as part of a fault diagnosis scheme to detect and isolate commonly occurring faults in a vehicle alternator system. Since the mathematical model of the alternator subsystem is quite involved and highly nonlinear; in order to simplify the diagnostic scheme, an equivalent linear time varying model based on the input-output behavior of the system is used for threshold equations derivation. A novel approach using Gaussian distribution to obtain the parameters of the system is investigated.

In the spirit of past contributions
to the formal characterization of diagnosis, this paper presents a formal characterization
of diagnosis of discrete dynamical systems, appealing to the situation
calculus. It then proceeds to establish a correspondence between
computing dynamical diagnoses and generating plans. It is this
correspondence that we feel may be of particular interest to
the DX community. Planning technology provides
tailored representations and fast, efficient algorithms for
automated plan generation. This paper shows how such technology can

If an autonomous mobile robot acts in a real non-deterministic environment it might faces situations where its internal belief of the world is in contradiction with the world itself. Such situations are caused by inaccurate acting and sensing or exogenous events. A reliable and dependable robot has to have the capabilities to actively cope with such situation.

This work is focused on analyzing diagnosability properties for a
given system model, from a structural point of view, taking into
account causal interpretations for differential constraints,
i.e. allowing their interpretation either in derivative or integral
causality. When both interpretations are allowed simultaneously for
a model, the system is said to be in mixed causality. A
characterization and algorithms, not based on the set of ARRs, for
computing those properties for the mixed causality form are
provided. The added power of mixed causality is demonstrated using a

Structural methods have previously been used to perform isolability
analysis and finding testable sub-models, so called Minimal
Structurally Overdetermined (MSO) sets or Analytical Redundancy
Relations (ARR). The number of MSO sets is exponential in the degree
of redundancy making the task of computing MSO sets intractable for
systems with high degree of redundancy. This paper describes an
efficient graph-theoretical algorithm for computing only the testable
sub-models where each model is influenced by different subsets of

This paper describes a solution to the Advance Diagnosis and
Prognostics testbed (ADAPT) diagnosis benchmark problem. One main
objective were to study and discuss how engineering students, with
no diagnosis research background, would solve a challenging
diagnosis problem. The study was performed within the framework of
a final year project course for students studying control
engineering. A main contribution of the work is the discussion on
the development process used by the students. Key steps process
include a local view, resulting in component-local residual

With the advent of the next generation of aerospace systems equipped with fly-by-wire controls, electro-mechanical actuators (EMA) are quickly becoming components critical to safety of aerospace vehicles. Being relatively new to the field, however, EMA lack the knowledge base compared to what is accumulated for the more traditional actuator types, especially when it comes to fault detection and prognosis.

The goal of testing is to discriminate between multiple hypotheses about a system -- for example, different fault diagnoses of an HVAC system -- by applying input patterns and verifying or falsifying the hypotheses from the observed outputs. Definitely discriminating tests (DDTs) are those input patterns that are guaranteed to discriminate between different hypotheses of non-deterministic systems. Finding DDTs is important in practice, but can be very expensive.

In this paper, effects preceding a latch-up fault in insulated gate bipolar transistors (IGBTs) are studied as they manifest within an electric motor drive system. Primary failure modes associated with IGBT latch-up faults are reviewed. Precursors to latch-up, primarily an increase in turn-off time and junction temperature, are examined for the IGBT. In addition, the relationship between junction temperature and turn-off time is explained by examining the semiconductor properties of an IGBT.

One of the most prominent technical challenges to effective deployment of health management systems is the vast difference in user objectives with respect to engineering development. In this paper, a detailed survey on the objectives of different users of health management systems is presented. These user objectives are then mapped to the metrics typically encountered in the development and testing of two main systems health management functions: diagnosis and prognosis.