Decentralized monitoring and diagnosis of manufacturing processes
S. Chand · 2002
A decentralized control method that augments Boolean logic control to provide greatly enhanced diagnostics and monitoring of systems with discrete-valued sensors and actuators is described. Unlike conventional Boolean logic, where logic is associated with the actuators, a behavior and timing model is described for both sensors and actuators, called control elements (CEs). The behavior model is defined by a sequence of events called the event signature, in a CE's neighborhood. The event signature encodes a subset of the process state into each CE. A method for the continuous evaluation of this signature is described and used to compute a measure of the likelihood of a CE to change state. This likelihood measure, called an expectation function, is used to check and enforce the correct behavior of a CE. Also, each CE learns a statistical temporal model in real time. The temporal model predicts delays in the states of the CE as a function of the previous delays and the current delays in the evaluation of its event signature. The distributed behavior model and the online estimated timing model are applied to a simulated bottle filling station.>