| 1. |
- Hagenblad, Anna, 1971-, et al.
(författare)
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A Comparison of Two Methods for Stochastic Fault Detection : the Parity Space Approach and Principal Component Analysis
- 2004
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Ingår i: Proceedings of Reglermöte 2004. - Linköping : Linköping University Electronic Press.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper compares two methods for fault detection and isolation in a stochastic setting. We assume additive faults on input and output signals, and stochastic unmeasurable disturbances. The first method is the parity space approach, analyzed in a stochastic setting. The stochastic parity space approach is similar to a Kalman filter, but uses an FIR fiter, while the Kalman filter is IIR. This enables faster response to changes. The second method is to use PCA, principal component analysis. In this case no model is needed, but fault isolation will be more difficult. The methods are illustrated on a simulation model of an F-16 aircraft. The fault detection probabilities can be calculated explicitly for the parity space approach, and are verified by simulations. The simulations of the PCA method suggest that the residuals have similar fault detection and isolation capabilities as for the stochastic parity space approach.
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| 2. |
- Klein, Inger, et al.
(författare)
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Automatic Creation of Sequential Control Schemes in Polynomial Time
- 1993
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Ingår i: Proceedings of the 32nd Conference on Decision and Control. - Linköping : Linköping University. - 0780312988 ; , s. 211-216 vol.1
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Konferensbidrag (refereegranskat)abstract
- Of all hard- and software developed for industrial control purposes, the majority is devoted to sequential, or binary valued, control and only a minor part to classical linear control. The sequential parts of the controller are typically invoked during startup or shut-down phases to bring the system either into its normal operating region or into some safe standby region. Despite its importance, fairly little theoretical research has been devoted to this area, and sequential control programs are still created manually without much support for a systematic approach. We propose a method to create sequential control programs automatically and online upon request, for example when a plant fault has occurred. The main idea is to spend some effort off-line on modeling the process, and from this model generate the control strategy, i.e. the plan. Here we present a planning tool implemented in a real-time expert system called G2. The planning system contains algorithms for creating plans in form of minimal GRAFCET charts that show maximal parallelism. The algorithms can handle a restricted class of problems and for this class the complexity only increases polynomially with the number of state variables.
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| 3. |
- Klein, Inger, et al.
(författare)
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Automatic Synthesis of Control Programs for an Assembly Line
- 1995
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Ingår i: Proceedings of Robotikdagarna 1995. - Linköping : Linköping University. - 9178715660 ; , s. 119-128
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The industry wants provably correct and fast formal methods for handling combinatorial dynamical systems. One example of such problems is error recovery in industrial processes. We have used a provably correct, polynomial-time planning algorithm to plan for a miniature assembly line, which assembles toy cars. Although somewhat limited, this process has many similarities with real industrial processes. By exploring the structure of this assembly line we have extended a previously presented algorithm, thus extending the class of problems that can be handled in polynomial time.
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| 4. |
- Klein, Inger, et al.
(författare)
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Automatic Synthesis of Control Programs in Polynomial Time for an Assembly Line
- 1996
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Ingår i: Proceedings of the 35th Conference on Decision and Control. - Linköping : Linköping University Electronic Press. - 0780335902 ; , s. 1749-1754 vol.2
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The industry wants provably correct and fast formal methods for handling combinatorial dynamical systems. One example of such problems is error recovery in industrial processes. We have used a provably correct, polynomial-time planning algorithm to plan for a miniature assembly line, which assembles toy cars. Although somewhat limited, this process has many similarities with real industrial processes. By exploring the structure of this assembly line we have extended a previously presented algorithm, thus extending the class of problems that can be handled in polynomial time. The planning tool presented here contains general-purpose algorithms that generate plans in the form of GRAFCET charts that are automatically translated into PLC code using a commercial PLC compiler.
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| 5. |
- Klein, Inger, et al.
(författare)
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Efficient Planning for a Miniature Assembly Line
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a provably correct and efficient, polynomial time, planning tool and its application to a miniature assembly line for toy cars. Although somewhat limited, this process has many similarities with real industrial processes. One of our previous polynomial-time planning algorithms has been extended and adapted to work for a larger class of planning problems, including this particular process. The plans produced by the planner are then translated into GRAFCET charts, which are compiled into code for a programmable logic controller. Although capable of producing ordinary assembly plans, the system is mainly intended for producing plans in error recovery situations.
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| 6. |
- Klein, Inger, et al.
(författare)
-
Fault Isolation in Object Oriented Control Systems
- 2000
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Ingår i: Proceedings of the 4th IFAC Symposium on Fault Detection Supervision and Safety for Technical Processes. - Linköping : Linköping University Electronic Press. - 9780080432502 ; , s. 1098-1102
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Konferensbidrag (refereegranskat)abstract
- This article addresses the problem of fault propagation between software modules in a large-scale control system with object oriented architecture. There exists a conflict between object-oriented design goals such as encapsulation and modularity, and the possibility to suppress propagating error conditions. The propagation manifests itself as many irrelevant error messages, and hence causes problems for system operators and service personnel when attempting to isolate the real fault. We propose a fault isolation scheme aimed at achieving clear and concise fault information to the operator without violating encapsulation and modularity. The approach is implemented and tested on a commercial industrial robot control system from ABB Robotics and a patent application has been filed with the swedish patent office (PRV).
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| 7. |
- Klein, Inger, et al.
(författare)
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Fault Isolation using Process Algebra Models
- 2002
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Ingår i: Proceedings of the 2002 Workshop on ModelChecking and Artificial Intelligence. - Linköping : Linköping University Electronic Press.
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Konferensbidrag (refereegranskat)abstract
- We investigate the problem of doing post mortem fault isolation for concurrent systems using a behavioral model. The aim is to isolate the action that has caused the failure of the system, the root action. The naive approach would be to say that a certain action is the root action if it is a logical consequence of the model and observations that the action is the first "bad thing to happen". This, however, is a strong requirement and puts high demand on the model. In this paper we describe the concept of strong root candidate, a relaxation of the naive approach. The advantage of determining the strong root candidate directly from model and observations is that the set of traces consistent with model and observations need not be explicitly computed. The property of strong root candidate can instead be determined on-the-fly, thus only computing relevant parts of the reachable state space.
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| 8. |
- Klein, Inger, et al.
(författare)
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Model-Checking Based Fault Isolation in UML
- 2001
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Ingår i: Proceedings of the 12th International Workshop on Principles of Diagnosis. - Linköping : Linköping University Electronic Press. ; , s. 103-110
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Konferensbidrag (refereegranskat)abstract
- We describe an approach to model-based fault isolation in large object oriented control systems. Our method relies on models of structure and behavior expressed in a subset of the Unified Modeling Language (UML). We consider system failures where on-line analysisis problematic, e.g. in safety-critical applications, leading to propagating alarms which have to be analyzed off-line. In our previous work we have shown how to use structural models, in the form of UML class diagrams, to reason about causal dependencies between error messages. In this paper we argue that models of behavior, in the form of UML state charts, together with verification techniques based on model checking further improve the ability to isolate faults off-line even when both models and observations are incomplete.
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| 9. |
- Klein, Inger, et al.
(författare)
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Model Checking Based Fault Isolation Using Automatic Abstraction
- 2003
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Ingår i: Proceedings of the 14th International Workshop on Principles of Diagnosis. - Linköping : Linköping University Electronic Press. ; , s. 113-118
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Konferensbidrag (refereegranskat)abstract
- We propose a fault isolation scheme based on model checking in order to reason about temporal properties of loosely coupled systems of concurrent processes. To address the problem of state space explosion we advocate an automatic abstraction technique based on a notion of observational equivalence. We statically analyze a system and construct a total function from possible message logs to isolated faults. Thus, fault isolation reduces to table lookup. Tables can be used at design time to find non-diagnosable failures of the system as well as redundant error messages.
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| 10. |
- Klein, Inger, et al.
(författare)
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Teaching Control Theory Using Problem Based Learning
- 2001
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Ingår i: Proceedings of the 12th Annual Conference on Innovations in Education for Electrical and Information Engineering. - Linköping : Linköping University Electronic Press.
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Konferensbidrag (refereegranskat)abstract
- Problem Based Learning, PBL, has been used for several years, especially in the medical commmunity. At Linköping University, now also the program in Information Technology is taught using this method. We describe how PBL is used in a basic course in control theory, including linear algebra and Laplace transforms. The experience from the first three years of the course is promising. The students are in general more active and more motivated than students in traditional courses. The teachers spend roughly the same number of hours on the course, but the focus has shifted to more contact with the students.
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