An observer based approach for achieving fault diagnosis and fault tolerant control of systems modeled as hybrid Petri nets.

In this paper, we propose an approach for achieving detection and identification of faults, and provide fault tolerant control for systems that are modeled using timed hybrid Petri nets. For this purpose, an observer based technique is adopted which is useful in detection of faults, such as sensor faults, actuator faults, signal conditioning faults, etc. The concepts of estimation, reachability and diagnosability have been considered for analyzing faulty behaviors, and based on the detected faults, different schemes are proposed for achieving fault tolerant control using optimization techniques. These concepts are applied to a typical three tank system and numerical results are obtained.

Observer based on-line fault diagnosis of continuous systems modeled as Petri nets.

This paper describes a technique for achieving on-line fault diagnosis in continuous systems that are modeled using Petri nets. The effect of place markings and transition markings are considered and based on the computed error between the initial marking and subsequent markings evolved in time, the faults are categorized assuming that the markings are both observable and unobservable. An algorithm has been suitably proposed for achieving detection of faults for a typical continuous three tank system along with suitable results.

The role of backbone conformation in deltorphin II binding: a QSAR study of new analogues modified in the 5-, 6-positions of the address domain.

The delta selectivity of the opioid heptapeptides deltorphin I and II has been attributed to the C-terminal 'address' domain, the hydrophobic Val(5)-Val(6) residues apparently playing a topographical role. We now report the synthesis, opioid binding affinities, and a QSAR study of a series of peptides in which one of the valine side chains was altered. QSAR analyses included previously published models for a binding pocket interaction and an optimum size (Schullery, S.; Mohammedshah, T.; Makhlouf, H.; Marks, E.; Wilenkin, B.; Escobar, S.; Mousigian, C.; Heyl, D. Bioorg. Med. Chem. 1997, 5, 2221), and a new approach for backbone conformational effects using Langevin dynamics simulation (PM3 semi-empirical force field) of an isolated peptide fragment containing the side chain and flanking peptide bonds. No evidence is found of binding pocket interactions or optimum size for either the position-5 or -6 side chain. Rather, delta binding is generally disfavored while mu binding is either unaffected (position-5) or favored (position-6) by larger side chains. The dynamics results provide evidence of similar 'local' conformation roles for the positions 5 and 6 side chains. Specifically, delta binding is favored by side chains that maximize the extension of the backbone, measured as the through-space distance between peptide fragment ends, the angle between lines connecting the alpha-carbon with fragment ends, or the difference between the psi and phi peptide angles.