| 1. |
- Fransson, Åsa, 1971, et al.
(författare)
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Characterization of fractured crystalline rock: two Swedish in situ field experiments
- 2014
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Ingår i: 1st International Discrete Fracture Network Engineering Conference, 20-22 oct 2014, Vancouver, Canada.
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Konferensbidrag (refereegranskat)abstract
- Construction of a nuclear waste repository requires information and an understanding of the fractured rock. The Swedish concept for nuclear waste deposition that is currently being developed by the Swedish Nuclear Fuel and Waste Management Co (SKB) includes a natural barrier in the form of crystalline rock, and engineered barriers in the form of bentonite and a copper canister. This paper aims to present two in situ field experiments: the first is the Large fractures experiment and the second is BRIE, the Bentonite Rock Interaction Experiment. Important issues include possible deformation (shearing) of fractures and deformation zones influencing the localization of canisters, and fluid flow, resulting in hydration of the bentonite. The aim of Large fractures is to further develop strategies and integrated investigation and modelling methodology for the identification and characterization of geological structures to ensure that (size) determination of large fractures or minor deformation zones to a greater extent can be based on real properties and to a lesser degree on a criterion related to the existence of a full perimeter fracture – tunnel intersection. BRIE is a field experiment which addresses the hydraulic interaction between the system components of compacted bentonite and the near-field host rock composed of hard and fractured bedrock. The above experiments are presented in terms of investigations performed to obtain discrete fracture descriptions. Grouting of fractures intersecting the investigation borehole of the Large fractures experiment was designed based on field data and a decrease in flow from above 200 liters/min to below 1 liter/min was achieved. The magnitude of the transmissivity of the fracture/deformation zone that was grouted indicates a large fracture size. This is also indicated by the ongoing integrated interpretation (geology, hydrogeology and geophysics). Results from BRIE show that hydration is uneven and is controlled by the main conductive fracture, highlighting the need for a relevant fracture description.
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| 2. |
- Bertilsson, Filip, et al.
(författare)
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Centralized versus Distributed Nonlinear Model Predictive Control for Online Robot Fleet Trajectory Planning
- 2022
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. ; 2022-August, s. 701-706
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Konferensbidrag (refereegranskat)abstract
- In this paper, we formulate and evaluate a centralized vs. a distributed approach for online trajectory generation for a fleet of mobile robots in the presence of static and dynamic obstacles. Due to dynamic obstacles, the trajectories need to be updated online and this is formulated as a nonlinear model predictive control problem. We show that both centralized and distributed MPC solvers manage to generate smooth collision-free trajectories. The distributed approach is shown to scale to many robots very well. In contrast, the computational cost of the centralized approach increases with the number of robots. However, the trajectories generated by the distributed control approach have larger deviations than those generated by the centralized approach. The experiments suggest that the centralized method should be chosen with sufficient computation resource while the distributed approach is a viable alternative when the number of robots is considerable.
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| 3. |
- Claessen, Koen, 1975, et al.
(författare)
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Applying valued booleans in testing of cyber-physical systems
- 2018
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Ingår i: Proceedings - 2018 3rd Workshop on Monitoring and Testing of Cyber-Physical Systems, MT-CPS 2018. ; , s. 8-9
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Konferensbidrag (refereegranskat)abstract
- In software testing, as in cyber-physical systems testing, test suites are traditionally developed by hand. In this work we consider one framework for putting the computer in charge of the testing instead: constrained random test case generation as supported by the tool QuickCheck. This is implemented by the use of Valued Booleans (VBools). VBools naturally allow for an extension of QuickCheck into cyber-physical systems, which is useful particularly since QuickCheck can perform shrinking of test cases. Shrinking is a technique to make test cases simpler while preserving failure.
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| 4. |
- Eddeland, Johan, 1991, et al.
(författare)
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Automated Mode Coverage Analysis for Cyber-Physical Systems using Hybrid Automata
- 2017
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 50:1, s. 9260-9265
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Konferensbidrag (refereegranskat)abstract
- Testing of cyber-physical systems (CPSs) is a complex task, mainly due to the presence of continuous dynamics. In industry, CPSs are typically safety-critical and their complexity is rapidly increasing. Thus, it is important to know how well the tests perform. One common approach to ensuring test quality is to use coverage criteria, for example the well-known MC/DC. However, most of the used coverage criteria in industry depend on code structure to find errors in the system and may fail to capture the complete dynamical behaviour. Two coverage definitions are presented that can be used to ensure that all the continuous dynamics in the system have been explored. It is shown that the MC/DC criterion is not always rigorous enough to test all the system behaviour. Finally, the proposed coverage criteria are applied to automatically assess the test quality for a plant model used at Volvo Car Corporation.
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| 5. |
- Eddeland, Johan, 1991, et al.
(författare)
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Objective functions for falsification of signal temporal logic properties in cyber-physical systems
- 2017
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. - 9781509067817 ; 2017-August, s. 1326-1331
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Konferensbidrag (refereegranskat)abstract
- Cyber-physical systems, such as automation and automotive systems, are highly complex systems that are frequently also safety-critical. Thus, it is important that these systems behave as intended, as incorrectness can have serious consequences. Due to continuous dynamics that yield infinite state spaces, the systems cannot be exhaustively tested to guarantee correct behavior, but systematic testing can be used to systematically search for behavior that is inconsistent with the requirements. However, manual testing is a tedious and error-prone task, and thus it is desirable to automate as much of the testing process as possible to increase efficiency and eliminate manual errors. This paper considers falsification of requirements expressed as temporal logic formulae to find errors in the Model-in-the-Loop stage of model-based development. The falsification is an optimization procedure where the objective function is determined by the definition of a quantitative semantics for the temporal logic formalism, and the optimization is performed over an input parametrization. It is shown that in certain cases where the discreteness of the system under test manifests itself in the objective function, the robustness values for the temporal logic specifications need to be modified. This paper presents two alternative objective functions suitable for these cases, and illustrates their use with both a small example and a use case from Volvo Car Corporation.
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| 6. |
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| 7. |
- Li, Jason, 1993, et al.
(författare)
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Evaluation of Photogrammetry for Use in Industrial Production Systems
- 2018
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. ; 2018-August, s. 414-420
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Konferensbidrag (refereegranskat)abstract
- A digital twin of a production system consists of geometric, kinematic and logical models of the physical system. One of the key challenges is to keep the digital twin up-to-date with changes of the real one. Today, laser scanning is the de-facto standard used to keep the geometry of the digital model synchronized. In recent years, advancements in the performance of Graphic Processing Units (GPUs) and the availability of cheap high-resolution digital cameras have made photogrammetry a viable alternative to laser scanning for building digital 3D-models. In this study, we investigate how photogrammetry competes against laser-scanning by comparing their results in form of point-clouds.
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| 8. |
- Lidén Eddeland, Johan, 1991, et al.
(författare)
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Enhancing Temporal Logic Falsification with Specification Transformation and Valued Booleans
- 2020
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Ingår i: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems. - 1937-4151 .- 0278-0070. ; 39:12, s. 5247-5260
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Tidskriftsartikel (refereegranskat)abstract
- Cyber-Physical Systems (CPSs) are systems with both physical and software components, for example cars and industrial robots. Since these systems exhibit both discrete and continuous dynamics, they are complex and it is thus difficult to verify that they behave as expected. Falsification of temporal logic properties is an approach to find counterexamples to CPSs by means of simulation. In this paper, we propose two additions to enhance the capability of falsification and make it more viable in a large-scale industrial setting. The first addition is a framework for transforming specifications from a signal-based model into Signal Temporal Logic. The second addition is the use of Valued Booleans and an additive robust semantics in the falsification process. We evaluate the performance of the additive robust semantics on a set of benchmark models, and we can see that which semantics are preferable depend both on the model and on the specification.
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| 9. |
- Lidén Eddeland, Johan, 1991, et al.
(författare)
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Evaluating Optimization Solvers and Robust Semantics for Simulation-Based Falsification
- 2020
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Ingår i: EPiC Series in Computing. - : EasyChair. - 2398-7340. ; 74, s. 259-266
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Konferensbidrag (refereegranskat)abstract
- Temporal-logic based falsification of Cyber-Physical Systems is a testing technique used to verify certain behaviours in simulation models, however the problem statement typically requires some model-specific tuning of parameters to achieve optimal results. In this experience report, we investigate how different optimization solvers and objective functions affect the falsification outcome for a benchmark set of models and specifications. With data from the four different solvers and three different objective functions for the falsification problem, we see that choice of solver and objective function depends both on the model and the specification that are to be falsified. We also note that using a robust semantics of Signal Temporal Logic typically increases falsification performance compared to using Boolean semantics.
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| 10. |
- Lidén Eddeland, Johan, 1991, et al.
(författare)
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Industrial Temporal Logic Specifications for Falsification of Cyber-Physical Systems
- 2020
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Ingår i: EPiC Series in Computing. - : EasyChair. - 2398-7340. ; 74, s. 267-274
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Konferensbidrag (refereegranskat)abstract
- In this benchmark proposal, we present a set of large specifications stated in Signal Temporal Logic (STL) intended for use in falsification of Cyber-Physical Systems. The main purpose of the benchmark is for tools that monitor STL specifications to be able to test their performance on complex specifications that have structure similar to industrial specifications. The benchmark itself is a Git repository which will therefore be updated over time, and new specifications can be added. At the time of submission, the repository contains a total of seven Simulink requirement models, resulting in 17 generated STL specifications.
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