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| 2. |
- Andreasson, Henrik, 1977-, et al.
(författare)
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Autonomous transport vehicles : where we are and what is missing
- 2015
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Ingår i: IEEE robotics & automation magazine. - 1070-9932 .- 1558-223X. ; 22:1, s. 64-75
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we address the problem of realizing a complete efficient system for automated management of fleets of autonomous ground vehicles in industrial sites. We elicit from current industrial practice and the scientific state of the art the key challenges related to autonomous transport vehicles in industrial environments and relate them to enabling techniques in perception, task allocation, motion planning, coordination, collision prediction, and control. We propose a modular approach based on least commitment, which integrates all modules through a uniform constraint-based paradigm. We describe an instantiation of this system and present a summary of the results, showing evidence of increased flexibility at the control level to adapt to contingencies.
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| 3. |
- Bergsten, Pontus, 1971-, et al.
(författare)
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Fuzzy Observers
- 2001
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Ingår i: The 10th IEEE International Conference on Fuzzy Systems (Volym:3). - New York, USA : IEEE conference proceedings. - 078037293X ; , s. 700-703
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Konferensbidrag (refereegranskat)abstract
- We consider the analysis and design of three different types of nonlinear observers for dynamic Takagi-Sugeno fuzzy systems. Our approach is based on extending existing nonlinear observer schemes, namely Thau-Luenberger and sliding mode observers, to the case of interpolated multiple local affine linear models. Then linear matrix inequality based techniques are used for observer analysis and design.
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| 4. |
- Bergsten, Pontus
(författare)
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Observers and controllers for Takagi-Sugeno fuzzy systems
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis studies analysis and design issues for observers anc controllers for Takagi-Sugeno (TS) fuzzy systems. Many physical systems are nonlinear in nature and using the well known linear techniques for such systems may result in bad performance, and even instability. On the other hand, analysis and design of observers and controllers for general nonlinear systems tend to be a quite involved procedure. It turns out, however, that a TS fuzzy system is able to represent or approximate a large class of nonlinear systems. Developing methods for observation and control for TS systems should therefore be worthwile. The TS fuzzy systems considered in this thesis are allowed to have an affine term. This can be an advantage, because affine TS fuzzy systems may be able to approximate nonlinear functions to high accuracy with fewer rules than the TS fuzzy system with linear consequents only. It is shown that observer design is more difficult when the weights in the TS fuzzy systems depend on the estimated state, and an explicit design procedure is devised for that case. A reduced order observer is also proposed. To deal with modeling errors a fuzzy sliding mode approach is taken. The controller design is focused on affine TS fuzzy systems. Analysis and design of observer-based error state feedback controllers are proposed. Furthermore, it is also shown how recent results on classical gain scheduling may be used for control of affine TS fuzzy systems. Analysis and design for both observers and controllers are based on quadratic stability analysis, and in some cases, on robust quadratic stability analysis. Although this approach may be conservative, it often results in automatic design procedures based on optimization subject to linear matrix inequalities.
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| 5. |
- Bergsten, Pontus, 1971-, et al.
(författare)
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Observers for Takagi-Sugeno fuzzy systems
- 2002
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Ingår i: IEEE transactions on systems, man and cybernetics. Part B. Cybernetics. - : IEEE Journals & Magazines. - 1083-4419 .- 1941-0492. ; 32:1, s. 114-121
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Tidskriftsartikel (refereegranskat)abstract
- We focus on the analysis and design of two different sliding mode observers for dynamic Takagi-Sugeno (TS) fuzzy systems. A nonlinear system of this class is composed of multiple affine local linear models that are smoothly interpolated by weighting functions resulting from a fuzzy partitioning of the state space of a given nonlinear system subject to observation. The Takagi-Sugeno fuzzy system is then an accurate approximation of the original nonlinear system. Our approach to the analysis and design of observers for Takagi-Sugeno fuzzy systems is based on extending sliding mode observer schemes to the case of interpolated multiple local affine linear models. Thus, our main contribution is nonlinear observer analysis and design methods that can effectively deal with model/plant mismatches. Furthermore, we consider the difficult case when the weighting functions in the Takagi-Sugeno fuzzy system depend on the estimated state
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| 6. |
- Brax, Christoffer
(författare)
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Anomaly detection in the surveillance domain
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the post September 11 era, the demand for security has increased in virtually all parts of the society. The need for increased security originates from the emergence of new threats which differ from the traditional ones in such a way that they cannot be easily defined and are sometimes unknown or hidden in the “noise” of daily life.When the threats are known and definable, methods based on situation recognition can be used find them. However, when the threats are hard or impossible to define, other approaches must be used. One such approach is data-driven anomaly detection, where a model of normalcy is built and used to find anomalies, that is, things that do not fit the normal model. Anomaly detection has been identified as one of many enabling technologies for increasing security in the society.In this thesis, the problem of how to detect anomalies in the surveillance domain is studied. This is done by a characterisation of the surveillance domain and a literature review that identifies a number of weaknesses in previous anomaly detection methods used in the surveillance domain. Examples of identified weaknesses include: the handling of contextual information, the inclusion of expert knowledge and the handling of joint attributes. Based on the findings from this study, a new anomaly detection method is proposed. The proposed method is evaluated with respect to detection performance and computational cost on a number datasets, recorded from real-world sensors, in different application areas of the surveillance domain. Additionally, the method is also compared to two other commonly used anomaly detection methods. Finally, the method is evaluated on a dataset with anomalies developed together with maritime subject matter experts. The conclusion of the thesis is that the proposed method has a number of strengths compared to previous methods and is suitable foruse in operative maritime command and control systems.
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| 7. |
- Coradeschi, Silvia, et al.
(författare)
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Fuzzy anchoring
- 2001
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Ingår i: The 10th IEEE international conference on fuzzy systems. - 078037293X ; , s. 111-114
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Konferensbidrag (refereegranskat)abstract
- An intelligent physical agent must incorporate motor and perceptual processes to interface with the physical world, and abstract cognitive processes to reason about the world and the options available. One crucial aspect of incorporating cognitive processes into a physically embedded reasoning system is the integration between the symbols used by the reasoning processes to denote physical objects, and the perceptual data corresponding to these objects. We treat this integration aspect by proposing a fuzzy computational theory of anchoring. Anchoring is the process of creating and maintaining the correspondence between symbols and percepts that refer to the same physical objects. Modeling this process using fuzzy set-theoretic notions enables dealing with perceptual data that can be affected by uncertainty/imprecision and imprecise/vague linguistic descriptions of objects
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| 8. |
- Doherty, Patrick, 1957-, et al.
(författare)
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A non-monotonic fuzzy logic.
- 1991
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Ingår i: International Fuzzy Systems Association, Fourth World Congress,1991.
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Konferensbidrag (refereegranskat)
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| 9. |
- Doherty, Patrick, 1957-, et al.
(författare)
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Fuzzy if-then-unless rules and their implementation.
- 1992
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Ingår i: International Conference on Information Processing and Management of Uncertainty in Knowledge-Based Systems, IPMU92,1992. - Linköping, Sweden : Springer.
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Konferensbidrag (refereegranskat)
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| 10. |
- Doherty, Patrick, 1957-, et al.
(författare)
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Fuzzy if-then-unless rules and their implementation
- 1993
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Ingår i: International Journal of Uncertainty Fuzziness and Knowledge-Based Systems. - : World Scientific. - 0218-4885. ; 1:2, s. 167-182
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Tidskriftsartikel (refereegranskat)abstract
- We consider the possibility of generalizing the notion of a fuzzy If-Then rule to take into account its context dependent nature. We interpret fuzzy rules as modeling a forward directed causal relationship between the antecedent and the conclusion, which applies in most contexts, but on occasion breaks down in exceptional contexts. The default nature of the rule is modeled by augmenting the original If-Then rule with an exception part. We then consider the proper semantic correlate to such an addition and propose a ternary relation which satisfies a number of intuitive constraints described in terms of a number of inference rules. In the rest of the paper, we consider implementational issues arising from the unless extension and propose the use of reason maintenance systems, in particular TMS's, where a fuzzy If-Then-Unless rule is encoded into a dependency net. We verify that the net satisfies the constraints stated in the inference schemes and conclude with a discussion concerning the integration of qualitative IN-OUT labelings of the TMS with quantitative degree of membership labelings for the variables in question.
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