| 11. |
- Broxvall, Mathias
(författare)
-
A middleware for ecologies of robotic devices
- 2007
-
Ingår i: Proceedings of the 1st international conference on Robot communication and coordination, RoboComm '07. - Piscataway : IEEE press. - 9789639799080 ; , s. Art no 30-
-
Konferensbidrag (refereegranskat)abstract
- The fields of autonomous robotics and ambient intelligence are converging toward the vision of smart robotic environments, or ubiquitous robotics, in which tasks are performed via the cooperation of many simple networked robotic devices. The concept of Ecology of Physically Embedded Intelligent Systems, or PEIS-Ecology, combines insights from these fields to provide a new solution to building intelligent robots in the service of people. To enable this vision, we need a common communication and cooperation model that allows dynamically assembled ad-hoc networks of robotic devices, a flexible introspection and configuration model allowing automatic (re)configuration and that can be shared between robotic devices at different scales, ranging from standard mobile robots to tiny networked embedded devices. In this paper we discuss the development of a middleware suitable for ubiquitous robotics in general and PEIS-Ecologies in specific. Our middleware is suitable for building truly ubiquitous robotics applications, in which devices of very different scales and capabilities can cooperate in a uniform way. We discuss the principles and implementation of our middleware, and also point to experimental results that show the viability of this concept.
|
|
| 12. |
- Broxvall, Mathias, 1976-
(författare)
-
A Study in the Computational Complexity of Temporal Reasoning
- 2002
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reasoning about temporal and spatial information is a common task in computer science, especially in the field of artificial intelligence. The topic of this thesis is the study of such reasoning from a computational perspective. We study a number of different qualitative point based formalisms for temporal reasoning and provide a complete classification of computational tractability for different time models. We also develop more general methods which can be used for proving tractability and intractability of other relational algebras. Even though most of the thesis pertains to qualitative reasoning the methods employed here can also be used for quantitative reasoning. For instance, we introduce a tractable and useful extension to the quantitative point based formalism STP. This extension gives the algebra an expressibility which subsumes the largest tractable fragment of the augmented interval algebra and has a faster and simpler algorithm for deciding consistency.The use of disjunctions in temporal formalisms is of great interest not only since disjunctions are a key element in different logics but also since the expressibility can be greatly enhanced in this way. If we allow arbitrary disjunctions, the problems under consideration typically become intractable and methods to identify tractable fragments of disjunctive formalisms are therefore useful. One such method is to use the independence property. We present an automatic method for deciding this property for many relational algebras. Furthermore, we show how this concept can not only be used for deciding tractability of sets of relations but also to demonstrate intractability of relations not having this property. Together with other methods for making total classifications of tractability this goes a long way towards easing the task of classifying and understanding relational algebras.The tractable fragments of relational algebras are sometimes not expressive enough to model real-world problems and a backtracking solver is needed. For these cases we identify another property among relations which can be used to aid general backtracking based solvers to finnd solutions faster.
|
|
| 13. |
- Broxvall, Mathias, et al.
(författare)
-
An ecological approach to odour recognition in intelligent environments
- 2006
-
Ingår i: 2006 IEEE International Conference on Robotics and automation, ICRA 2006. - 0780395050 ; , s. 2066-2071
-
Konferensbidrag (refereegranskat)abstract
- We present a new approach for odour detection and recognition based on a so-called PEIS-Ecology: a network of gas sensors and a mobile robot are integrated in an intelligent environment. The environment can provide information regarding the location of potential odour sources, which is then relayed to a mobile robot equipped with an electronic nose. The robot can then perform a more thorough analysis of the odour character. This is a novel approach which alleviates some the challenges in mobile olfaction techniques by single and embedded mobile robots. The environment also provides contextual information which can be used to constrain the learning of odours, which is shown to improve classification performance.
|
|
| 14. |
- Broxvall, Mathias, 1976-, et al.
(författare)
-
Developing Medical Image Processing Algorithms for GPU assisted parallel computation
- 2013
-
Ingår i: Computer Vision in Medical Imaging. - : World Scientific. - 9789814460934 - 9789814460958 ; , s. 245-270
-
Bokkapitel (refereegranskat)abstract
- GPU’s have recently emerged as a significantly more powerful computing plat-form, capable of several orders of magnitude faster computations compared toCPU based approaches. However, they require significant changes in the algorithmic design compared to traditional programming paradigms. In this chapter we specifically introduce the reader to an overview of GPGPU development tools and the potential algorithmic pitfalls and bottlenecks when developing medical imaging algorithms for the GPU. We present a few general methodologies and building blocks for implementing fast image processing on GPUs. More specifically they include: methods for performing fast image convolutions and filtering;line detection, and bandwidth and memory considerations when processing volumetric datasets. Finally we conclude with a discourse on numerical precision as well as on mixing single floating-point versus double floating-point code.
|
|
| 15. |
- Broxvall, Mathias, et al.
(författare)
-
Disjunctions, Independence, Refinements
- 2002
-
Ingår i: Artificial Intelligence. - 0004-3702. ; 140:1-2, s. 153-173
-
Tidskriftsartikel (refereegranskat)abstract
- An important question in constraint satisfaction is how to restrict the problem to ensure tractability (since the general problem is NP-hard). The use of disjunctions has proven to be a useful method for constructing tractable constraint classes from existing classes; the well-known ‘max-closed’ and ‘ORD-Horn’ constraints are examples of tractable classes that can be constructed this way. Three sufficient conditions (the guaranteed satisfaction property, 1-independence and 2-independence) that each ensure the tractability of constraints combined by disjunctions have been proposed in the literature. We show that these conditions are both necessary and sufficient for tractability in three different natural classes of disjunctive constraints. This suggests that deciding this kind of property is a very important task when dealing with disjunctive constraints. We provide a simple, automatic method for checking the 1-independence property—this method is applicable whenever the consistency of the constraints under consideration can be decided by path-consistency. Our method builds on a connection between independence and refinements (which is a way of reducing one constraint satisfaction problem to another.)
|
|
| 16. |
- Broxvall, Mathias, 1976-, et al.
(författare)
-
Fast GPU based adaptive filtering of 4D echocardiography
- 2012
-
Ingår i: IEEE Transactions on Medical Imaging. - Piscataway, USA : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0062 .- 1558-254X. ; 31:6, s. 1165-1172
-
Tidskriftsartikel (refereegranskat)abstract
- Time resolved three-dimensional (3D) echocardiography generates four-dimensional (3D+time) data sets that bring new possibilities in clinical practice. Image quality of four-dimensional (4D) echocardiography is however regarded as poorer compared to conventional echocardiography where time-resolved 2D imaging is used. Advanced image processing filtering methods can be used to achieve image improvements but to the cost of heavy data processing. The recent development of graphics processing unit (GPUs) enables highly parallel general purpose computations, that considerably reduces the computational time of advanced image filtering methods. In this study multidimensional adaptive filtering of 4D echocardiography was performed using GPUs. Filtering was done using multiple kernels implemented in OpenCL (open computing language) working on multiple subsets of the data. Our results show a substantial speed increase of up to 74 times, resulting in a total filtering time less than 30 s on a common desktop. This implies that advanced adaptive image processing can be accomplished in conjunction with a clinical examination. Since the presented GPU processor method scales linearly with the number of processing elements, we expect it to continue scaling with the expected future increases in number of processing elements. This should be contrasted with the increases in data set sizes in the near future following the further improvements in ultrasound probes and measuring devices. It is concluded that GPUs facilitate the use of demanding adaptive image filtering techniques that in turn enhance 4D echocardiographic data sets. The presented general methodology of implementing parallelism using GPUs is also applicable for other medical modalities that generate multidimensional data.
|
|
| 17. |
- Broxvall, Mathias, et al.
(författare)
-
Have another look on failures and recovery planning in perceptual anchoring
- 2004
-
Konferensbidrag (refereegranskat)abstract
- An important requirement for autonomous systems is the ability to detect and recover from exceptional situations such as failures in observations. In this paper we demonstrate how techniques for planning with sensing under uncertainty can play a major role in solving the problem of recovering from such situations. In this first step we concentrate on failures in perceptual anchoring, that is how to connect a symbol representing an object to the percepts of that object. We provide a classification of failures and present planning-based methods for recovering from them. We illustrate our approach by showing tests run on a mobile robot equipped with a color camera.
|
|
| 18. |
- Broxvall, Mathias, et al.
(författare)
-
PEIS ecology : integrating robots into smart environments
- 2006
-
Ingår i: 2006 IEEE International Conference on Robotics and automation, ICRA 2006. - 0780395050 ; , s. 212-218
-
Konferensbidrag (refereegranskat)abstract
- We introduce the concept of Ecology of Physically Embedded Intelligent Systems, or PEIS-Ecology. This is a network of heterogeneous robotic devices (PEIS) pervasively embedded in the environment. A PEIS can be as simple as a toaster and as complex as a humanoid robot. PEIS can exchange information at different levels of abstraction, and share both physical and virtual functionalities to perform complex tasks. By putting together insights from the fields of autonomous robotics and of ambient intelligence, the PEIS-Ecology approach explores a new road to building assistive, personal, and service robots. In this paper, we discuss this concept, describe a first realization of it, and show an implemented use-case scenario.
|
|
| 19. |
- Broxvall, Mathias, et al.
(författare)
-
Point Algebras for Temporal Reasoning: Algorithms and Complexity
- 2003
-
Ingår i: Artificial Intelligence. - 0004-3702. ; 149:2, s. 179-220
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the computational complexity of temporal reasoning in different time models such as totally-ordered, partially-ordered and branching time. Our main result concerns the satisfiability problem for point algebras and point algebras extended with disjunctions—for these problems, we identify all tractable subclasses. We also provide a number of additional results; for instance, we present a new time model suitable for reasoning about systems with a bounded number of unsynchronized clocks, we investigate connections with spatial reasoning and we present improved algorithms for deciding satisfiability of the tractable point algebras.
|
|
| 20. |
- Broxvall, Mathias, et al.
(författare)
-
Recovery planning for ambiguous cases in perceptual anchoring
- 2005
-
Ingår i: Proceedings of the 20th national conference on Artificial intelligence, AAAI-05. - 9781577352365 ; , s. 1254-1260
-
Konferensbidrag (refereegranskat)abstract
- An autonomous robot using symbolic reasoning, sensing and acting in a real environment needs the ability to create and maintain the connection between symbols representing objects in the world and the corresponding perceptual representations given by its sensors. This connection has been named perceptual anchoring. In complex environments, anchoring is not always easy to establish: the situation may often be ambiguous as to which percept actually corresponds to a given symbol. In this paper, we extend perceptual anchoring to deal robustly with ambiguous situations by providing general methods for detecting them and recovering from them. We consider different kinds of ambiguous situations and present planning-based methods to recover from them. We illustrate our approach by showing experiments involving a mobile robot equipped with a color camera and an electronic nose.
|
|
