Online fault detection and avoidance framework for distributed factory control systems
AssigneeSiemens Aktiengesellschaft
InventorsPeng Zhao, Yan Lu
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Abstract
An on-line fault detection and avoidance method is provided for industrial control systems that include multiple interacting process controllers. The method addresses the problem that not all faults can be determined and removed at the time of system design and testing. When a fault translates into a time-out condition in one or more controllers, symptoms are identified, persistence is measured, other involved controllers are identified, the fault condition is identified and control laws are reconfigured to avoid the fault condition in the future.
Claims24
A method for detecting and avoiding faults in a distributed factory control system having a plurality of industrial controllers, each said controller controlling at least one underlying process, the method comprising:
- in a first controller, identifying a symptom of a fault condition by identifying a deviation of a state of an underlying process controlled by the first controller from a corresponding state kept by the controller;
- in the first controller, measuring a persistence of the symptom, and ignoring the symptom if the measured persistence is below a threshold value;
- finding other controllers involved in the fault condition by generating in at least the first controller a search tree having leaf nodes that are monitored conditions;
- identifying the fault condition including identifying states of the other controllers involved in the fault condition;
- and
- reconfiguring control rules controlling states of the involved controllers to avoid the fault condition in the future;
- wherein finding other controllers involved in the fault condition further comprises:
- starting the search tree at a state where place p1 of a time Petri net is marked for an amount of time φ≧THTmax(p1) where THTmax(p1) is a maximum token holding time of place p1;
- if none of the leaf nodes of the search tree in the first controller exceeds its maximum token holding time, then generating a search tree in a second controller starting at a place q of a time Petri net that is an output of a transition t1 to which p1 is an input;
- and
- creating a chain of controllers by repeating the generating a search tree step in additional controllers until one of the following conditions is met:
- a. maximum token holding time condition is not exceeded in any leaf node in a search tree;
- b. none of the places in a controller where the maximum token holding time has been exceeded lies in any path with places or transitions connected to other controllers;
- and
- c. a search tree within a controller contains only null-cycles.
A method for detecting and avoiding faults in a distributed factory control system having a plurality of industrial controllers, each said controller controlling at least one underlying process, the method comprising:
- in a first controller, identifying a symptom of a fault condition by identifying a deviation of a state of an underlying process controlled by the first controller from a corresponding state kept by the controller;
- in the first controller, measuring a persistence of the symptom, and ignoring the symptom if the measured persistence is below a threshold value;
- finding other controllers involved in the fault condition by generating in at least the first controller a search tree having leaf nodes that are monitored conditions;
- identifying the fault condition including identifying states of the other controllers involved in the fault condition;
- and
- reconfiguring control rules controlling states of the involved controllers to avoid the fault condition in the future, including:
- transmitting from the first controller to at least one active controller associated with the fault condition a list of “to avoid” states.
A computer program product comprising a computer readable recording medium having recorded thereon a computer program comprising code means for, when executed on an industrial controller, instructing said controller to control steps in a method for detecting and avoiding faults in a distributed factory control system having a plurality of industrial controllers, each said controller controlling at least one underlying process, the method comprising:
- in a first controller, identifying a symptom of a fault condition by identifying a deviation of a state of an underlying process controlled by the first controller from a corresponding state kept by the controller;
- in the first controller, measuring a persistence of the symptom, and ignoring the symptom if the measured persistence is below a threshold value;
- finding other controllers involved in the fault condition by generating in at least the first controller a search tree having leaf nodes that are monitored conditions;
- identifying the fault condition including identifying states of the other controllers involved in the fault condition;
- and
- reconfiguring control rules controlling states of the involved controllers to avoid the fault condition in the future;
- wherein finding other controllers involved in the fault condition further comprises:
- starting the search tree at a state where place p1 of a time Petri net is marked for an amount of time φ≧THTmax(p1) where THTmax(p1) is a maximum token holding time of place p1;
- if none of the leaf nodes of the search tree in the first controller exceeds its maximum token holding time, then generating a search tree in a second controller starting at a place q of a time Petri net that is an output of a transition t1 to which p1 is an input;
- and
- creating a chain of controllers by repeating the generating a search tree step in additional controllers until one of the following conditions is met:
- a. maximum token holding time condition is not exceeded in any leaf node in a search tree;
- b. none of the places in a controller where the maximum token holding time has been exceeded lies in any path with places or transitions connected to other controllers;
- and
- c. a search tree within a controller contains only null-cycles.
A computer program product comprising a computer readable recording medium having recorded thereon a computer program comprising code means for, when executed on an industrial controller, instructing said controller to control steps in a method for detecting and avoiding faults in a distributed factory control system having a plurality of industrial controllers, each said controller controlling at least one underlying process, the method comprising:
- in a first controller, identifying a symptom of a fault condition by identifying a deviation of a state of an underlying process controlled by the first controller from a corresponding state kept by the controller;
- in the first controller, measuring a persistence of the symptom, and ignoring the symptom if the measured persistence is below a threshold value;
- finding other controllers involved in the fault condition by generating in at least the first controller a search tree having leaf nodes that are monitored conditions;
- identifying the fault condition including identifying states of the other controllers involved in the fault condition;
- and
- reconfiguring control rules controlling states of the involved controllers to avoid the fault condition in the future;
- including:
- transmitting from the first controller to at least one active controller associated with the fault condition a list of “to avoid” states.
Dependencies are inferred from the claim text.