Control system for distributed sensors and actuators
First Claim
1. A decentralized system for monitoring and controlling a dynamic process, comprising:
- a plurality of distributed control elements, each of said control elements having at least two states;
a communication link connecting at least selected ones of said control elements; and
a plurality of microprocessors corresponding to said plurality of control elements, each of said microprocessors dedicated to a corresponding one of said control elements for time-stamping state changes of said one control element;
communicating said time-stamped state changes to selected others of said control elements;
storing a sequence function associated with said one control element, said sequence function comprising a sequence of at least one other control element state change defining an event signature for said one control element to change state;
computing an expectation function for determining a likelihood of said one control element to change state, said expectation function computed from said sequence function; and
evaluating state changes to identify malfunctions of said one control element based on said state change likelihoods determined by said expectation function.
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Abstract
Conventional Boolean Logic Control is augmented to provide enhanced diagnostics, monitoring, and fail safe operation for dynamic systems having distributed discrete-valued sensors and actuators. A decentralized model of a controlled system defines behavior and timing models for both sensors and actuators, termed Control Elements (CEs). Each CE has a first model for transition from state 0 to 1, and a second model for transition from state 1 to 0. Each behavioral model is defined by an Event Signature comprising a sequence of state changes in neighboring CEs. A continuous evaluation of event signatures is performed to compute a probability that a given CE will change state. An Expectation Function is used to check and enforce the correct behavior of a CE. A statistical temporal model predicts delays in the states of a CE as a function of its previous and current delays. The distributed behavior and on-line timing models are used to detect and diagnose incorrect behavior and failures of decentralized sensors and actuators.
84 Citations
10 Claims
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1. A decentralized system for monitoring and controlling a dynamic process, comprising:
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a plurality of distributed control elements, each of said control elements having at least two states; a communication link connecting at least selected ones of said control elements; and a plurality of microprocessors corresponding to said plurality of control elements, each of said microprocessors dedicated to a corresponding one of said control elements for time-stamping state changes of said one control element;
communicating said time-stamped state changes to selected others of said control elements;
storing a sequence function associated with said one control element, said sequence function comprising a sequence of at least one other control element state change defining an event signature for said one control element to change state;
computing an expectation function for determining a likelihood of said one control element to change state, said expectation function computed from said sequence function; and
evaluating state changes to identify malfunctions of said one control element based on said state change likelihoods determined by said expectation function. - View Dependent Claims (2, 3)
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4. A method of monitoring and controlling a decentralized system having a plurality of distributed control elements, comprising the steps of:
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providing each of said control elements with a dedicated microprocessor, each of said control elements having at least two states; connecting selected ones of said dedicated microprocessors with a communication link; time-stamping state changes of each of said plurality of control elements; communicating said time-stamped state changes of each of said control elements to selected others of said dedicated microprocessors connected by said communication link; providing a plurality of sequence functions, each of said sequence functions associated with a corresponding one of said control elements and comprising a sequence of at least one other control element state change defining an event signature for said one of said control elements; generating a plurality of expectation functions for determining likelihoods for each of said control elements to change state, each of said expectation functions computed from a corresponding one of said sequence functions; and evaluating control element state changes to identify state change errors based on said state change likelihoods determined by said expectation functions. - View Dependent Claims (5, 6)
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7. A method of monitoring and controlling a decentralized system having a plurality of distributed control elements including sensors and actuators, comprising the steps of:
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providing a plurality of microprocessors, each of said microprocessors connected to at least one of said control elements, each of said control elements having at least two states; connecting at least selected ones of said microprocessors with a communication link; monitoring and time-stamping state changes of said plurality of control elements; communicating said time-stamped state changes of each of said control elements to selected ones of said microprocessors connected by said communication link; providing a behavioral model for each of said control elements, each of said behavioral models comprising a specified sequence of control element state changes forming an event signature for a specified one of said control elements to change state; providing a temporal model for each of said control elements, each of said temporal models comprising a time delay estimate for a specified change of state of one of said control elements; generating a plurality of expectation functions for determining likelihoods of said control elements to change state, each of said expectation functions derived from a corresponding one of said event signatures; and evaluating control element state changes and identifying state change errors based on said state change likelihoods determined by said expectation functions. - View Dependent Claims (8, 9, 10)
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Specification