21th semcon 19th of december, 21th semcon · kartheepan balachandran, martin andersen, rasmus...

21TH SEMCON 19TH OF DECEMBER, 2008

SCIENTIFIC METHODS AND COMMUNICATION (SMAC)

PROGRAMME AT GLANCE:

During Poster Viewing sessions at least one author should be present at the poster, to explain and discuss the idea and results of the project with other participants.

Time Room B3‐104 Room B2‐104 Room B2‐109 Room A4‐108 Room A4‐106

08.00‐08.15 Poster Mounting Poster Mounting Poster Mounting

Poster Mounting

08.15‐08.20 Conference opening

08.20‐09.30 Oral Session

09.30‐09.40 Break Break Break Break Break




12.00‐12.30 Lunch Lunch Lunch Lunch Lunch



13.10‐14.30 Poster Session Poster Session Poster Session Poster Session

14.30 Conference closing

Department of Electronic Systems, Department of Health Science and Technology &

Aalborg University Esbjerg Aalborg University Fredrik Bajers Vej 7

Aalborg Ø Denmark

21TH SEMCON SCIENTIFIC METHODS AND COMMUNICATION (SMAC)

DECEMBER 19th, 2008

AALBORG UNIVERSITY FREDERIK BAJERS VEJ 7

AALBORG Ø DENMARK

FINAL PROGRAMME AND ABSTRACTS

SMAC FINAL PROGRAMME 2008/2009

List of Abstracts

Network and Distributed Processes (NDP)

NDP‐720 Design and Verification of a Satellite using HOOD and UPPAAL

Claus Trier Bang Pedersen*, Dennis Hilmar Kristensen** NDP‐721 Reliable Transport Protocol for Uninhabited Aerial Vehicles

in a Mobile Ad‐Hoc Network Anders Friis*, Anders Jochumsen, Johannes Friis, Bjarke Freund‐Hansen**, Jakob Sloth Nielsen

NDP‐722 In‐Car Network Implemented with Switched Ethernet

Henrik Dalsager Christensen**, Casper Lyngesen Mogensen, Rasmus Pedersen*, Mads Jensen, Jeppe Juel Petersen

NDP‐723 A Generic Software Framework for Distributed Coordination

and Control in Multiagent Systems Kim Mørk, Alexander Larsen, Ebbe Nielsen, Sigurd Villumsen*, Thorbjørn Borup**

NDP‐724 Software Framework for Reconfigurable Distributed System

on AAUSAT3 Jesper Bønding**, Kasper Vinther, Kasper J. Fuglsang, Morten Tychsen*, Marc Pessans‐Goyheneix

NDP‐725 Energy Minimization using Distributed α‐β‐swap Algorithm

Kartheepan Balachandran, Martin Andersen, Rasmus Skovgaard Andersen**, Christian Lindequist Larsen*

21th SEMCON December 19th, 2008 Aalborg University


NDP‐726 Collaboration Layer for Robots in Mobile Ad‐hoc Networks Jacob Honoré Broberg*, Simon Bjerg Mikkelsen, Christian Bräuner Sørensen**, Jesper Ellgaard Pedersen, Søren Thorhauge Hede

IRS Aalborg University Esbjerg (IRS)

IRS7‐H215 Swing‐up and Stabilization of an Inverted Pendulum using a Reaction Wheel

Frank Jepsen, Anders Roland Pedersen*, Anders Søborg**

Signal Processing and Communication (SAC) SAC‐740 Replacing Bodymounted Microphones with Distant

Microphone Arrays using Wiener Filtering Erik B. Poulsen**, Alex Aa. Birklykke*, Casper Fynsk, Kasper L.

Jakobsen SAC‐741 Improvement of noise robustness of a small vocabulary

speech recognition system Brian Melgaard Christensen, Palle Tofteng Andreasen, Troels

Torkil Østeraa**, Andreas Corneliussen*, Helge Glinvad Grøn

SAC‐742 Piano Transcription using Wavelet Decomposition and

Neural Networks Louise Baldus Vestergaard**, Johnni Thomsen Pedersen*,

Esben Madsen SAC‐743 Using Ultra Wide Band in Tactical Communications to Avoid

Enemy Detection Karl D. Hansen**, T. Nikolai Beier*



Biomedical Engineering and Informatics (Sundhedsteknologi, ST) ST‐705a System for locating a 3‐D position of a generated sound in

the human bowel, using time delay of arrival Lars Christian Fjeldborg, Kasper Lundhus, Michael Vognsen

Nielsen*, Kasper Juhl Græsbøll Ottesen** ST‐705b Unsupervised method to classify motor unit action

potentials online Suzan de Goede**, Lars Johannesen*, Jens Stampe Sørensen ST‐705c Correlational study between the severity of carotid stenosis

and bio‐acoustic features Markus Muehlbacher‐Karrer**, Majken Munch, Michael

Svorkmo*, Chiara Trentin ST‐705d Automated detection of brugada syndrome Ulrik Silvanus Lerkevang Grove**, Lisbeth Lundager Gylstorff,

Thomas Worbech, Tine Maria Hansen, Ask Schou Jensen* ST‐705e Identification of patients suffering from central sensitization

by principal component analysis of nociceptive reflex receptive fields

Michael Brun Jensen ST‐706a Brain atrophy in subjects with mild cognitive impairment

and Alzheimer’s disease compared to normal cognitive subjects

Kenneth Andersen, Anders Holch Heebøll‐Holm*, Morten Schøler Kristensen**, Yang Li



ST‐706b Global and Regional White Matter Atrophy in Alzheimer’s Disease

Vibeke Hvarregaard Andersen**, Natasja Spring Ehlers*, Anja Olesen

ST‐706c Semi‐Automatic Registration of CT and MR Images using a

New Fiducial Marker Rasmus Holland*, Ditte Haargaard Kopp, Kate Zeberg

Olesen** ST‐706d Blood vessel segmentation for image‐guided radiotherapy

in cervical cancer Ann Merete Duedal Jensen, Merete Martlev Jensen**, Anne

Sofie Korsager*, Rikke Kristensen, Mick Lykkegaard Schmidt ST‐706e Use of features extracted from MR images to classify

subjects with respect to the classes: control, mild cognitive impairment and alzheimer’s disease

Mette Jensen, Rikke Beck Nielsen*, Heidi Klitgaard Pedersen, Sinna Pilgaard Ulrichsen**

Wireless Communication (TK) TK‐710 Reliable identification of RFID tags using multiple

independent reader sessions Karsten F. Nielsen* og Rasmus M. Jacobsen**



Oral Session 8 minutes for presentation and 2 minutes for discussion

Room B3‐104

Conference Opening and Welcome Conference Chair: Ole K. Andersen Co‐chairs: Thomas Graven‐Nielsen, Mads Græsbøll Christensen and

Mikael Svenstrup **Oral presentation *Poster presentation 08.15 – 08.20 Conference Opening 08.20 – 08.30 NDP‐720: Design and Verification of a Satellite using HOOD

and UPPAAL Claus Trier Bang Pedersen*, Dennis Hilmar Kristensen** 08.30 – 08.40 NDP‐721: Reliable Transport Protocol for Uninhabited Aerial

Vehicles in a Mobile Ad‐Hoc Network Anders Friis*, Anders Jochumsen, Johannes Friis, Bjarke Freund‐Hansen**, Jakob Sloth Nielsen

08.40 – 08.50 NDP‐722: In‐Car Network Implemented with Switched

Ethernet Henrik Dalsager Christensen**, Casper Lyngesen Mogensen, Rasmus Pedersen*, Mads Jensen, Jeppe Juel Petersen

08.50 – 09.00 NDP‐723: A Generic Software Framework for Distributed

Coordination and Control in Multiagent Systems Kim Mørk, Alexander Larsen, Ebbe Nielsen, Sigurd Villumsen*, Thorbjørn Borup**



09.00 – 09.10 NDP‐724: Software Framework for Reconfigurable Distributed System on AAUSAT3 Jesper Bønding**, Kasper Vinther, Kasper J. Fuglsang, Morten Tychsen*, Marc Pessans‐Goyheneix

09.10 – 09.20 NDP‐725: Energy Minimization using Distributed α‐β‐swap

Algorithm Kartheepan Balachandran, Martin Andersen, Rasmus Skovgaard Andersen**, Christian Lindequist Larsen*

09.20 – 09.30 NDP‐726: Collaboration Layer for Robots in Mobile Ad‐hoc Networks Jacob Honoré Broberg*, Simon Bjerg Mikkelsen, Christian Bräuner Sørensen**, Jesper Ellgaard Pedersen, Søren Thorhauge Hede

09.30 – 09.40 BREAK 09.40 – 09.50 IRS7‐H215: Swing‐up and Stabilization of an Inverted

Pendulum using a Reaction Wheel


09.50 – 10.00 SAC‐740: Replacing Bodymounted Microphones with

Distant Microphone Arrays using Wiener Filtering Erik B. Poulsen**, Alex Aa. Birklykke*, Casper Fynsk, Kasper L.

Jakobsen 10.00 – 10.10 SAC‐741: Improvement of noise robustness of a small

vocabulary speech recognition system Brian Melgaard Christensen, Palle Tofteng Andreasen, Troels




10.10 – 10.20 SAC‐742: Piano Transcription using Wavelet Decomposition and Neural Networks

Louise Baldus Vestergaard**, Johnni Thomsen Pedersen*, Esben Madsen

10.20 – 10.30 SAC‐743: Using Ultra Wide Band in Tactical Communications

to Avoid Enemy Detection Karl D. Hansen**, T. Nikolai Beier* 10.30 – 10.40 ST‐705a: System for locating a 3‐D position of a generated

sound in the human bowel, using time delay of arrival Lars Christian Fjeldborg, Kasper Lundhus, Michael Vognsen

Nielsen*, Kasper Juhl Græsbøll Ottesen** 10.40 – 10.50 ST‐705b: Unsupervised method to classify motor unit action

potentials online Suzan de Goede**, Lars Johannesen*, Jens Stampe Sørensen 10.50 – 11.00 BREAK 11.00 – 11.10 ST‐705c: Correlational study between the severity of carotid

stenosis and bio‐acoustic features Markus Muehlbacher‐Karrer**, Majken Munch, Michael

Svorkmo*, Chiara Trentin 11.10 – 11.20 ST‐705d: Automated detection of brugada syndrome Ulrik Silvanus Lerkevang Grove**, Lisbeth Lundager Gylstorff,

Thomas Worbech, Tine Maria Hansen, Ask Schou Jensen* 11.20 – 11.30 ST‐705e: Identification of patients suffering from central

sensitization by principal component analysis of nociceptive reflex receptive fields

Michael Brun Jensen



11.30 – 11.40 ST‐706a: Brain atrophy in subjects with mild cognitive impairment and Alzheimer’s disease compared to normal cognitive subjects


11.40 – 11.50 ST‐706b: Global and Regional White Matter Atrophy in

Alzheimer’s Disease Vibeke Hvarregaard Andersen**, Natasja Spring Ehlers*, Anja

Olesen 11.50 – 12.00 ST‐706c: Semi‐Automatic Registration of CT and MR Images

using a New Fiducial Marker Rasmus Holland*, Ditte Haargaard Kopp, Kate Zeberg

Olesen** 12.00 – 12.30 LUNCH 12.30 – 12.40 ST‐706d: Blood vessel segmentation for image‐guided

radiotherapy in cervical cancer Ann Merete Duedal Jensen, Merete Martlev Jensen**, Anne

Sofie Korsager*, Rikke Kristensen, Mick Lykkegaard Schmidt 12.40 – 12.50 ST‐706e: Use of features extracted from MR images to

classify subjects with respect to the classes: control, mild cognitive impairment and alzheimer’s disease


12.50 – 13.00 TK‐710: Reliable identification of RFID tags using multiple




Poster Session 5 minutes for presentation and 5 minutes for discussion

Room B2‐104

Chairman: Thomas Graven‐Nielsen 13.10 – 13.20 ST‐705a: System for locating a 3‐D position of a generated

sound in the human bowel, using time delay of arrival Lars Christian Fjeldborg, Kasper Lundhus, Michael Vognsen

Nielsen*, Kasper Juhl Græsbøll Ottesen** 13.20 – 13.30 ST‐705b: Unsupervised method to classify motot unit action

potentials online Suzan de Goede**, Lars Johannesen*, Jens Stampe Sørensen 13.30 – 13.40 ST‐705c: Correlational study between the severity of carotid

stenosis and bio‐acoustic features Markus Muehlbacher‐Karrer**, Majken Munch, Michael

Svorkmo*, Chiara Trentin 13.40 – 13.50 ST‐705d: Automated detection of brugada syndrome Ulrik Silvanus Lerkevang Grove**, Lisbeth Lundager Gylstorff,

Thomas Worbech, Tine Maria Hansen, Ask Schou Jensen* 13.50 – 14.00 ST‐705e: Identification of patients suffering from central

sensitization by principal component analysis of nociceptive reflex receptive fields

Michael Brun Jensen 14.30 – Conference Closure



Poster Session 5 minutes for presentation and 5 minutes for discussion

Room B2‐109

Chairman: Ole K. Andersen 13.10 – 13.20 ST‐706a: Brain atrophy in subjects with mild cognitive

impairment and Alzheimer’s disease compared to normal cognitive subjects


13.20 – 13.30 ST‐706b: Global and Regional White Matter Atrophy in

Alzheimer’s Disease Vibeke Hvarregaard Andersen**, Natasja Spring Ehlers*, Anja

Olesen 13.30 – 13.40 ST‐706c: Semi‐Automatic Registration of CT and MR Images

using a New Fiducial Marker Rasmus Holland*, Ditte Haargaard Kopp, Kate Zeberg

Olesen** 13.40 – 13.50 ST‐706d: Blood vessel segmentation for image‐guided

radiotherapy in cervical cancer Ann Merete Duedal Jensen, Merete Martlev Jensen**, Anne

Sofie Korsager*, Rikke Kristensen, Mick Lykkegaard Schmidt 13.50 – 14.00 ST‐706e: Use of features extracted from MR images to

classify subjects with respect to the classes: control, mild cognitive impairment and alzheimer’s disease


14.30 – Conference Closure



Poster Session

5 minutes for presentation and 5 minutes for discussion

Room A4‐108 Chairman: Mads Græsbøll Christensen

13.10 – 13.20 SAC‐740: Replacing Bodymounted Microphones with

Distant Microphone Arrays using Wiener Filtering Erik B. Poulsen**, Alex Aa. Birklykke*, Casper Fynsk, Kasper L.

Jakobsen 13.20 – 13.30 SAC‐741: Improvement of noise robustness of a small

vocabulary speech recognition system Brian Melgaard Christensen, Palle Tofteng Andreasen, Troels


13.30 – 13.40 SAC‐742: Piano Transcription using Wavelet Decomposition

and Neural Networks Louise Baldus Vestergaard**, Johnni Thomsen Pedersen*,

Esben Madsen 13.40 – 13.50 SAC‐743: Using Ultra Wide Band in Tactical Communications

to Avoid Enemy Detection Karl D. Hansen**, T. Nikolai Beier* 13.50 – 14.00 TK‐710: Reliable identification of RFID tags using multiple


14.30 – Conference Closure



Poster Session

5 minutes for presentation and 5 minutes for discussion

Room A4‐106 Chairman: Mikael Svenstrup

13.10 – 13.20 NDP‐720: Design and Verification of a Satellite using HOOD

and UPPAAL Claus Trier Bang Pedersen*, Dennis Hilmar Kristensen** 13.20 – 13.30 NDP‐721: Reliable Transport Protocol for Uninhabited Aerial

Vehicles in a Mobile Ad‐Hoc Network Anders Friis*, Anders Jochumsen, Johannes Friis, Bjarke Freund‐Hansen**, Jakob Sloth Nielsen

13.30 – 13.40 NDP‐722: Intern Car Ethernet

Henrik Dalsager, Casper Lyngesen Mogensen, Rasmus Pedersen, Mads Jensen, Jeppe Juel Petersen

13.40 – 13.50 NDP‐723: A Generic Software Framework for Distributed

Coordination and Control in Multiagent Systems Kim Mørk, Alexander Larsen, Ebbe Nielsen, Sigurd Villumsen*, Thorbjørn Borup**

13.50 – 14.00 NDP‐724: Software Framework for Reconfigurable

Distributed System on AAUSAT3 Jesper Bønding**, Kasper Vinther, Kasper J. Fuglsang, Morten Tychsen*, Marc Pessans‐Goyheneix

14.00 – 14.10 NDP‐725: Energy Minimization using Distributed α‐β‐swap

Algorithm Kartheepan Balachandran, Martin Andersen, Rasmus Skovgaard Andersen**, Christian Lindequist Larsen*



14.10 – 14.20 NDP‐726: Collaboration Layer for Robots in Mobile Ad‐hoc

Networks Jacob Honoré Broberg*, Simon Bjerg Mikkelsen, Christian Bräuner Sørensen**, Jesper Ellgaard Pedersen, Søren Thorhauge Hede

14.20 – 14.30 IRS7‐H215: Swing‐up and Stabilization of an Inverted Pendulum using a Reaction Wheel



Design and Verification of a Satellite using HOOD

and UPPAAL

Dennis Hilmar Kristensen** and Claus Trier Bang Pedersen*Group NDS-720

December 12, 2008

Introduction Before launching a satellite it is desired to test that the individual subsystems are workingaccording to the specification. The basic system is composed of a platform and communication subsystemconnected through a bus. These subsystems are designed according to their internal interfaces andbehavior.

Hypothesis:”It is possible to create a satellite design that can be validatedprior to launch, according to its behavioral requirements.”

Methods All subsystems on the satellite are specified by a requirement specification used for thedesign. The design is done using the HOOD method[1], which is specified and used by the EuropeanSpace Agency.

The HOOD behavioral models are developed by defining statecharts directly in UPPAAL makingit possible to verify the behavioral properties of the design. The behavioral properties are defined bythe requirement specification and transformed to queries in UPPAALs specification language. However,most requirements are not directly verifiable in the specification language, but are verified using variousannotation techniques. Running these queries verifies all properties of the model.

These are the steps taken during each design iteration:

1. Model HOOD Object based on the requirements

2. Model Behavior in UPPAAL and check for deadlocks

3. Run queries based on the requirements

Results By introducing UPPAAL in the HOOD design process the transformation process betweenHOOD and UPPAAL is eliminated. The internal communication system and bus has been modeledwith automatons, restricting the bus to a signle subsystem at any given time. In each subsystem anumber of threads are running, which was also modeled and verified without deadlocks. All the Platformrequirements have been transformed into UPPAAL queries and verified, making the platform behave asintended.

Discussion Several studies have shown UPPAAL very useful for finding bugs and errors in designspecifications[3] as well as already implemented systems[2]. We have shown a way to design a system usingUPPAAL and continuously verify the specifications and design. Directly converting the requirements intoexpressions that are validated keeps the system and its documentations consistent. The model can alsobe used to validate flight plans, even after the satellite has been launched.

References

[1] H. U. Group. HOOD User Manual. ftp://ftp.estec.esa.nl/pub/wm/wme/Web/HUM.ps.gz, 1994.[2] K. Havelund, K. G. Larsen, and A. Skou. Formal Verification of a Power Controller Using the RealTime Model Checker UPPAAL., 1999.[3] D. Priddin. Method Integration for Real-Time System Design and Verification. PhD thesis, Universityof York, 1999.

1

RELIABLE TRANSPORT PROTOCOL FOR

UNINHABITED AERIAL VEHICLES IN A MOBILE AD-HOC NETWORK

Bjarke Freund-Hansen**, Anders Friis*, Johannes Friis, Anders Jochumsen, and Jakob Sloth Nielsen

Group 08gr721

Introduction: At Aalborg University, the Autonomous Vehicles Group is currently working on a project with an autonomously flying helicopter. Currently the communication between a helicopter and a ground station consists of a TCP connection over a IEEE 802.11g wireless connection. In the future, the group plans to expand the research to use multiple helicopters simultaneously, which will need intercommunication as well as communication with one or more ground stations. One research subject is on autonomous flying helicopters in an urban environment, where varying levels of packet loss is expected. Under these conditions the current communication setup is unfit for use.

This paper documents the design, implementation, and evaluation of a communication protocol, denoted UAV Transport Protocol (UTP). UTP is designed for use in an IEEE 802.11 wireless ad-hoc network [1], supporting reliable and unreliable datagram delivery to one or multiple destinations. Reliable in this context means; all transmitted messages shall be retransmitted until acknowledged.

Methods: UTP uses UDP as the underlying protocol, utilising the techniques for multicast and broadcast provided by UDP. The functionality for reliable datagram delivery is implemented using acknowledgements and retransmissions. A method for fragmenting datagrams is implemented to support datagrams larger than the maximum IP packet size (~65kB).

The protocol is implemented in the C++ programming language with focus on providing a high level object oriented API for the client application, and a simple implementation using the abstract data structures provided by the C++ Standard Template Library.

Results: Tests are performed on laptops, each with 1.66GHz dual core CPU, interconnected with 100 Mbit/s Ethernet through the HIDENETS Topology Emulator [2], which is used to emulate network topologies with specified packet loss probabilities between nodes in the network.

The results shows that UTP, with 95% confidence, has a higher goodput than TCP, at a packet loss equal to 5%, when transmitting between two nodes. In average the goodput is approximately 2.5 times higher at 5% packet loss, and increasing as the packet loss increase. The CPU usage of UTP, on the laptops used for the test is; approximately 70% for the receiver, and approximately 30% for the sender.

Discussion: Based on the goodput measurements, the conclusion is that UTP is a good fit for use in ad-hoc networks where you expect varying levels of packet loss and occasionally full outages for shorter periods of time. This means that UTP is a more suitable protocol than TCP for the Autonomous Vehicles Group for future research in urban and multiple helicopter scenarios.

References[1] IEEE Inc. IEEE Std 802.11-2007. Standard. 2007.[2] Jensen, MN, Nickelsen, A. Evaluation of Routing Dependability in MANETs using a Topology Emulator. Masters thesis. 2007.

21st 7SEMCON, December 19, 2008

IN-CAR NETWORK IMPLEMENTED WITHSWITCHED ETHERNET

Henrik Dalsager Christensen**, Mads Jensen, Casper Lyngesen Mogensen, Rasmus Pedersen*,Jeppe Juel Petersen

Group NDP722

Introduction Unicorn G4 [1] is the fourth generation race car built by students at Aalborg University with the purpose ofcompeting in the Formula SAE (Society of Automotive Engineers) [2] series. In the current development phase, the teamwishes to extend the data acquisition and develop a hydraulic system to handle the clutch and gear. To accommodate thesefeatures it was proposed to replace the existing system witha network-based system. To allow the pit-crew to have easyaccess to the car data, it was proposed to use switched Ethernet as this allows compatibility with any PC. The most timecritical part of the system is the gear shift. The goal is to prove that the in-car network will never cause the total time fora gear shift to be higher than the gear shift time of 180 ms withthe current system.

Methods A network consisting of 4 nodes, was set up to emulate the proposed in-car network. To avoid as much softwarecaused variance in the delivery time measurements as possible, two micro controller based network nodes were imple-mented, operating in half duplex mode at 10 Mbit/s, making itpossible to measure delivery times on hardware level. TwoPC’s were set up to create background network traffic.

The delivery times were measured with different network loads and the data was analysed to find the maximum deliverytime.

Results The delivery times were measured in three different tests, one with no network load and two with network load,one with high packet rate and one with high data rate, the delivery time in all three tests was roughly 520µs with a standarddeviation of 7µs. More than 12000 delivery times were sampled for each test.Some variance in the delivery times wasexpected, because the network nodes polled for incoming data with a period of 20µs. A worst case scenario where thetransmitting node was receiving packets, causing collisions on the network, was also measured. This measurement showeda maximum delivery time of 1.72 ms.

Discussion The tests showed a delivery time which in the worst case addedless than a 2 ms delay to the gear shiftsequence. Because the proposed hydraulic actuation time was estimated to roughly 80 ms, the in-car network will nevercause the gear shift time to exceed the 180 ms limit.

References

[1] Unicorn Race Engineering. Official home page.http://unicorn.aau.dk.

[2] Society of Automotive Engineers. Official home page.http://students.sae.org/competitions/formulaseries/.

http://unicorn.aau.dk

http://students.sae.org/competitions/formulaseries/

A GENERIC SOFTWARE FRAMEWORK FOR DISTRIBUTED COORDINATION AND CONTROL

IN MULTIAGENT SYSTEMS Thorbjørn Borup**, Alexander Larsen, Kim Mørk, Ebbe Nielsen, Sigurd Villumsen*

Group NDP-723

Introduction: The world wide demographic trend shows that the average life expectancy is increasing. This entails that the amount of individuals that need care is increasing. To reduce the resulting increased workload an automation of trivial cleaning tasks is purposed. To establish a foundation for this automation, a generic software framework for distributed coordination and control in multiagent systems is designed. Since execution of cleaning tasks in multiagent systems demand communication between numerous and potential diverse peripheral units, these should be supported by the framework. A cleaning application incorporating two peripheral units is designed and key aspects are implemented using the software framework.

Methods and Materials: The software framework is divided into three layers which contain sublayers in compliance with the OSI model. The first layer contains the hardware specific (wireless) topology for data transmission. The second layer contains the communication protocol which ensures reliable data transmission between agents. The third layer contains the application. The software framework is generic due to the fact that all layers and their separate parts are exchangeable, as long as the designed interfaces are obeyed. The implemented aspects of the application concern task assignment and communication with peripheral units. A hierarchical iterative conflict resolution method has been used to solve the distributed task assignment problem [1]. This ensures that the most important task is assigned to an agent first. The framework has been implemented on a localisation system from Ubisense and an automated door from Besam since these unit types are relevant for multiagent cleaning applications.

Results: The developed software framework has been tested trough implementation of parts of the designed application. The conducted tests showed that the designed application is successfully able to make multiple agents assign tasks by means of the designed protocol. Conducted tests regarding the peripheral units showed that these were successfully integrated into the framework. The cooperative completion of tasks, which is based on a master/slave structure has been verified using UPPAAL. The results showed that all states are reachable and that no deadlocks occurred.

Discussion: The conducted research have resulted in a generic software framework for multiagent systems. This framework may provide a foundation for further development of automated household cleaning. The framework is generic so it is also possible to use it for other multiagent applications.

References[1] Nicholas V. Findler & Gregory D. Elder, Multiagent coordination and cooperation in a distributed dynamic environment with limited resources, Department of Computer Science and Artificial Intelligence Laboratory, Arizona State University, 1995.

21th 7SEMCON, December 19, 2008

SOFTWARE FRAMEWORK FOR RECONFIGURABLEDISTRIBUTED SYSTEM ON AAUSAT3

Jesper Bønding**, Kasper F. Jensen, Marc Pessans-Goyheneix,Morten B. Tychsen* and Kasper Vinther

Group NDP-724

Introduction: A distributed system has been proposed for the student satellite AAUSAT3, in order toimprove redundancy, reliability [1] and to ease application development. A suitable software frameworkis needed for the processing units, to ensure cooperation between applications, and to set the ground forreconfiguration of software in space. The focus has been put on robustness, reconfigurability, testabilityand ease of application development.

Methods and Material: The software framework development involved selection and test of kernel,protocol stack modification and introduction of software update possibilities. FreeRTOS [2] has beenchosen as kernel to ensure cooperation between applications. There has already gone work into a protocolstack, with the development of the connection oriented CAN Space Protocol (CSP) and the interruptbased CAN driver [3]. CSP has been modified to meet the needs for the software framework and aservice layer has been added. A new software update strategy has been proposed and implementationof bootloader and software image server system is currently in progress. Performance tests have beenperformed to evaluate the developed software.

Results: The chosen processing unit for AAUSAT3 is on the boundary of what is needed. A smalltest program used 83 % of the available SRAM. There are still some robustness issues in the protocolthat needs to be addressed, but an acceptable goodput has been achieved, and flexibility and ease ofapplication development has improved. Estimates indicate that software update times can be considerablereduced, compared to AAUSAT-II.

Discussion: A software framework now exists, with a reusable software platform which eases the appli-cation development. The framework can potentially be extended/modified to other distributed systems.The dynamic allocation of receive buffers in the protocol should be avoided to make the system moredeterministic and robust. The SRAM usage problem also has to be solved, either by adding extra SRAMor by reducing the amount needed, which can be problematic without compromising flexibility and mod-ularity.

References

[1] Wiley J. Larson, James R. Wertz. Space Misson Analysis and Design. Space Technology Library.3rd edition. 1999; 651-654, 659.

[2] Richard Barry. FreeRTOS. Internet. Oct 2008. http://www.freertos.org/.

[3] Michael Rimestad, Rene Jespersen, Johan de Claville Christiansen, Rasmus Foldager Andersen.Communication infrastructure and project management for AAUSAT3. 7th semester - Aalborg Univer-sity. 2007.

http://www.freertos.org/

Energy Minimization using Distributed α-β-swap Algorithm

Martin Andersen, Rasmus Skovgaard Andersen**,

Kartheepan Balachandran, and Christian Lindequist Larsen*

Group NDP-725

Introduction Many problems in computer vision can be solved using energyminimization. This includes finding depth in stereo images in the form of dispar-ity maps. Disparity maps are the focus of this project but the method developedapply to other energy minimization problems as well. A disparity map is a la-beling indicating the depth of each pixel in a set of stereo images. The bestsolution is found by minimizing an energy function. Graph cut is a state of theart method within computer vision for finding the best solution, but the heavycomputing for minimizing the energy function tends to make the algorithm slow.

Method The computation time is decreased by distributing the work load toseveral servers using a client-server model. The well-known method α-β-swap[1] is used to create graph networks, as it is very suited for distribution. Theclient distributes the source images to each server and makes an initial disparitymap that is to be optimized. The servers receive the disparity map and a task,which is a part of the computation that can be run in parallel. The tasks arecarried out in parallel and the disparity map on the client is updated on thefly. A large amount of data is exchanged on the network, and to reduce theload the disparity map is compressed using RLE compression before it is sentbetween the client and a server. The algorithm is repeated until the energy ofthe disparity map cannot be further minimized.

Results The time for computing a disparity map has for a test set of stereoimages (cones of size 450x375 with disparities between 15 and 60) been reducedby 41% from 58s on one computer to 34s on a distributed system with one clientand three servers with two kernels each.

Discussion The distributed method reduces the overall time of computing adisparity map using α-β-swap and graph cuts. The time reduction depends onthe number of servers and their configuration as well as the properties of thesource images. Task queues has been proven theoretically as well as in tests toreduce computation time. The distribution does not affect the quality of theresulting image.

References [1] Y. Boykov, O. Veksler, and R. Zabih, “Fast Approximate En-ergy Minimization via Graph Cuts,” Proc. IEEE Trans. Pattern Analysis and

Machine Intelligence, vol. 23, no. 11, pp. 1222-1239, Nov. 2001.

Collaboration Layer for Robots in Mobile Ad-hocNetworks

Jacob Honore Broberg*, Søren Thorhauge Hede, Simon Bjerg Mikkelsen, Jesper EllgaardPedersen, Christian Brauner Sørensen**

Group NDP-726

Introduction In many applications multiple robots in Mobile Ad-hoc Networks are requiredto collaborate in order to solve a task. It is shown by proof of concept that a CollaborationLayer can be modelled and designed to handle much of the collaboration communication. TheCollaboration Layer will remove the overhead from the task solving applications and thus increasefunctionality reuse and reduce the complexity in designing and implementing such applicationson robots.

Methods In this proposal the Collaboration Layer has been modelled to handle service andposition discovery, group management, and synchronisation among robots, but can be extendedwith more modules. The Collaboration Layer has been designed as a part of a classical layerednetwork model using the model-before-requirements method and the terminology of Tanenbaum[1]. The method ensures that the layer is not optimized for a specific application, nor does thelayer depend on a specific implementation of the Virtual Machine. Based on this model of theCollaboration Layer, generic services are provided to the application running on the robot. Theservices are generic because they can be used by many different applications, independent of thetask to be solved. Likewise, specific services are requested from the underlying Virtual Machine,such as broadcast, multicast, and reliable unicast. The Collaboration Layer can handle bothdistributed and centralized solving of tasks.

Results To illustrate the usage of the Collaboration Layer, an evaluation scenario has beencarried out. A prototype version of the Collaboration Layer has been implemented to run onstationary PCs simulating moving robots. The Virtual Machine has been implemented basedon TCP/IP on Ethernet and a wireless link simulator creates a virtual wireless network. In theevaluation scenario five robots solve the task of vacuum cleaning and entrance guarding, whichinvolves the ability to discover potential co-workers, form groups, and shift from one group toanother. A test has been carried out with this evaluation scenario, which came out successful.

Discussion The application in the scenario primarily consisted of the algorithm to move thedifferent robots. Most of the collaboration communication between the robots was handled bythe Collaboration Layer. By proof of concept, this shows that it may be possible to handlecollaboration in a generic way. Future work will be to implement the entire Collaboration Layeron real robots and test it in a real environment.

References

[1] Andrew S. Tanenbaum. Computer Networks 4th edition. Pearson Education, Inc, 2003.

1

Swing-up and Stabilization of an Inverted Pendulum using a Reaction Wheel


Group IRS7-H215 Introduction: An inverted pendulum can be controlled by a reaction wheel [1]. The reaction wheel is a flying wheel used to convert torque from a motor to torque acting on the pendulum; the wheel is attached directly to the motor’s shaft and mounted at the end of the pendulum. The pendulum has a fixed point of rotation and is controlled by applying force at the end of the pendulum. In this project the objective was to model the reaction wheel pendulum, design swing-up and stabilization controllers, and to implement it on an experimental set-up that was designed from scratch. Methods and Material: The modelling was based on the physical principles of conservation of angular momentum and the standard model of a DC motor. Based on this we designed an experimental set-up. While the set-up was built by the smith at AAUE, we designed and implemented the software and electronic hardware to drive the motor and retrieve measurements. The differential equations describing the dynamics of the reaction wheel pendulum was converted into a state space model with four states. Our stabilizing controller was made using the pole placement method and the swing-up control consists of a two-stage energy based controller. Furthermore, a full state estimator was designed and implemented, as only three states can be measured using the set-up. Results: The model was validated and used to design a stabilizing controller which was implemented with success. The swing-up controller was also successfully implemented; although, some tuning was needed to overcome the problem of switching between the controllers.

Discussion: Other projects on the reaction wheel pendulum often use a purchasable experimental kit, but we proved it was possible to construct a reasonable set-up within a limited time frame [1,2]. This makes it hard to compare results; however, there may be room for improvement of the swing-up control by using the techniques described in [2]. References [1] Geoffrey Chauveau, Damien Chazal, Daisuke Nakayama, Erik Olsen, Staffan Palm. Controlling the Reaction Wheel Pendulum. Royal Institute of Technology in Stockholm. 2005; 4,27-28. [2] Srinivas, K. N. and Behera, Laxmidhar. Swing-up control strategies for a reaction wheel pendulum. International Journal of Systems Science. 2008; 39:12,1165-1177;

Replacing Bodymounted Microphones with

Distant Microphone Arrays using Wiener

Filtering

Alex Aa. Birklykke∗, Casper Fynsk, Kasper L. Jakobsen and Erik B. Poulsen∗∗

Group 740

Introduction Actors and lecturers wear microphones to be hearable to theaudience, which often inhibit their freedom to move either due to wires con-nected to the microphone, or due to a transmitter box. It is well known that amicrophone array can be used to capture sound from one direction. The pur-pose of the study was to investigate whether microphone arrays combined withWiener �ltering could be used to remove microphones from actors or speakers.Methods A linear, equidistant microphone array was constructed. The signalsfrom the microphones were time-aligned using a time domain Wiener �lter basedon the Wiener-Hopf equation.The time-aligned signal was �ltered for stationarynoise using a second Wiener �lter, which was implemented in the frequencydomain using spectral subtraction of speech and noise spectrum estimates. Avoice activity detector (VAD) was implemented to identify non-speech periodsfor the noise estimation by feature extraction of formant frequencies.Results The Wiener �lter microphone array was able to accentuate coherent,as well as attenuate incoherent, sources. Simulation of signals corrupted withAWGN noise showed that the proposed method was able to time-align the mi-crophone signals even in poor SNR conditions. However, in a coherent noiseenvironment the performance of the method was severely degraded even at highSNR. The post-�ltering was able to reduce stationary noise in non-speech pe-riodes. In speech periodes the output SNR generally remained unchanged. Inlow SNR conditions the noise reduction resulted in aubible speech distortionreducing the intelligibility. With lower SNR even the speech was attenuated.Discussion The study showed that it is possible to use Wiener �ltering fortime-aligning signals recorded by a microphone array. The method is signi�-cantly a�ected by low frequency noise because it correlates highly between themicrophones. The system is able to reduce noise in environments with highSNR, when the VAD correctly separates speech and noise. The system sup-presses noise but decreases intelligibility in environments with low SNR. Thework showed that the concept is plausible.

1

Improvement of noise robustness of a small vocabulary speech recognition system

Palle Tofteng Andreasen, Brian Melgaard Christensen, Andreas Corneliussen*,Helge Glinvad Grøn, Troels Torkil Østeraa**

Group SAC-741

Introduction The use of speech recognition systems (SRS) has expanded and now in-cludes a plethora of handheld devices, facilitating a way for users to interact with thedevices. A scenario where manual interaction is cumbersome, is during bike rides, whereusers cannot control their portable music device (PMD). Instead, if the PMD can be con-trolled by voice, it will become less inconvenient to use.Most modern SRSs include large vocabularies and incorporate noise reduction as a sep-arate process[1]. New approaches to feature extraction have been proposed which incor-porate noise robustness, exploiting that only a limited vocabulary is needed.

Methods A limited vocabulary, consisting of nine words, is considered adequate for con-trolling a PMD. For comparison purposes, a reference, template-based, SRS has beendeveloped. This system utilizes a parametric (Linear Predictive Coding) and a non-parametric (cepstrum) method of feature extraction. Two methods have been developedto replace these methods, both relying on the same nine all-pole filters, estimated fromenergy intensive parts of reference pronunciations. Method 1 relies on differences insummed spectra before and after filters. Method 2 detects the presence of 9 differentphonemes by computing the distance to reference phonemes.

Results A test has been carried out using 10 pronunciations of each word at 81 differ-ent SNRs. The results show that the non-parametric reference SRS correctly recognizesall pronunciations at SNRs above 19 dB. The parametric SRS does not recognize all wordscorrectly at any SNR level and reaches an error rate of 12.8% at 19 dB SNR. The devel-oped methods reach error rates of 26.9% and 36.2% respectively, at 19 dB SNR. The errorrate for the Method 1 never becomes lower than 26.7%, however, below -3 dB SNR, itperforms better than the reference systems. Method 2 never reaches error rates below29.3% but performs better than all other methods at 0 dB SNR and below.

Discussion The results show that a SRS based solely on the proposed methods does notperform better than the reference SRSs. However, the proposed methods perform better atlower SNR levels, which suggests that a system based on a combination of the traditionaland the proposed methods could decrease error rates for SRSs.

References [1] J. S. Lim, Speech Enhancement. Prentice-Hall Signal Processing Series,1. ed., 1983.

1

Piano Transcription using Wavelet Decomposition and Neural Networks

Esben Madsen, Johnni Thomsen Pedersen* and Louise Baldus Vestergaard**SAC-Group 742

Introduction

Various solutions have been proposed for creating an automatic transcription system for music composersand musicians in general[2]. As there are many different genres of music and instruments, most of theprevious transcription systems have focused on either classifying instruments, detection of notes or rhythmplayed or a combined version of these. In these transcription systems, neural networks have been used withvarious preprocessing blocks; many rather complex. As a full transcription system is out of scope for thisresearch, the aim has been limited to transcription of one specific piano, with focus on feature extraction.

Methods

The system desired consists of an efficient feature extraction followed by detection of the notes from theextracted features, using a pattern recognition tool.Feature extraction was done by discrete wavelet transform, using Daubechies D4 algorithm[3]. A raw wavefile containing piano music was decomposed into different wavelet contributions. These were used as featureextraction for 88 different neural networks, each network charged with the task of recognizing a specific pianonote. Specific sequences of the wavelet decomposition was used as input for the corresponding neuralnetworks. Training and test data were available, hence supervised learning was possible. The supervisedmulti layer feed forward network structure was chosen[1].

Results

It was possible to extract significant features from the piano signal using a wavelet transform, and shownthat a neural network could be trained to recognize the different notes by use of these features. In mostcases a substantial amount of false misses were detected, but almost no false hits.

Discussion

The results are most of all “proof of concept”, as there are countless possibilities for optimization by im-provement of the already used methods. The variation in the training data was not large enough to detectwhether a specific note was present, though it seemed there was almost no wrongs when the the note wasnot present. In postprocessing there are development possibilities, e.g. a statistically reliable decision couldbe achieved using a Bayesian framework. The test showed that feature extraction by wavelet decompositionis possible, but whether it is an optimal solution is left for further research.

References

[1] Simon Haykin. Neural Networks – A Comprehensive Foundation. 1999.

[2] Anssi Klapuri and Manuel Davy, editors. Signal Processing Methods for Music Transcription. 2006.

[3] Stephane Mallat. A Wavelet Tour of Signal Processing. 1999.

USING ULTRA WIDE BAND IN TACTICAL COMMUNICATIONS

TO AVOID ENEMY DETECTIONKarl D. Hansen**, T. Nikolai Beier*

Group EE 743

Introduction

Ultra Wide Band (UWB) is often used for short range, high bandwidth, low power designs like Wireless USB. The signals are so weak and noise-like, that it does not interfere with other radio systems, because power is spread over a large bandwidth.

Impulse Radio (IR) UWB has no carrier, but instead sends a series of pulses over the air.

The hypothesis:

“Using UWB technology in tactical military radio communications will avert the enemy from detecting the transmissions.”

means that the system must work with very poor SNR, low bandwidth demand <10 kiB/s for speech and a goal of at least 3 km range like common narrow band radios. The signal should look like random noise, unless a secret, predefined code is known.

Prototype UWB-based “walkie-talkies” achieved a range of several km [1], but did not focus on “enemy detection”.

Methods

System limits and performance was determined by Matlab simulations. Modulator, additive white Gaussian noise channel and demodulator for Pulse Position Modulation (PPM) was implemented.

The design procedure was: First decide on bit rate, pulse width and duty cycle (depends on hardware and wanted spectrum), then the number of chips and slots in chips can be decided. Then the spectrum and performance is found through simulations.

Results

The range is several km with 1 W average transmitter power, but it is detectable within 400 m.

BER for PPM simulation indicates that the BER goes from ~0% to 1.1% between -55 dB and -60 dB SNR (in reasonable sized simulation), with perfect synchronization between radios.

The correlation receiver is very sensitive to timing drift and jitter, which should be <10 ps.

The transmitted impulses can be a statistically insignificant addition to the frequency spectrum and amplitude/pdf plots, while getting the wanted data through.

Discussion

It is possible to achieve a low risk of detection, and at the same time pick up the signal when the time hopping code is known.

The biggest hindering for long range IR-UWB is the timing constraints.

Using source coding could further improve the system performance.

References

[1] Fontana R. J. Recent System Applications of Short-Pulse Ultra-Wideband (UWB) Technology. IEEE Microwave Theory and Tech., Vol. 52, No. 9, September 2004

[2] De Benedetto M.G., Giancola G. Book title: Understanding Ultra Wide Band, Prentice Hall 2004

System for locating a 3‐D position of a generated sound in

the human bowel, using time delay of arrival Kasper Lundhus, Kasper Juhl Græsbøll Ottesen **, Michael Vognsen Nielsen * and

Lars Christian Fjeldborg Group 705a

Introduction: 3-D localization of bowel sounds using Time Delay of Arrival (TDoA) is an unexplored working field. In the literature, 2-D localization of abdominal sounds is described as a useful mapping method [1]. It is desired to investigate if this can be applied to 3-D space. Based on the literature, it is assumed that intestinal gasses affects the speed of the abdominal sound propagation, and thereby the precision of the TDoA. The purpose of this study is to investigate the effect of that factor. Methods and Material: A model for sound source localization, using the TDoA and Least Squares Principle (LSP) is designed. Using delays found by cross correlations, TDoA is assumed to detect the origin of an abdominal sound. This is a technique used in other research areas [2]. LSP is implemented to minimize domain and system related measurement errors. In order to determine errors related to the abdominal environment, two experiments are made:

1. Sound waves are propagated through free air. 2. Sounds, created by a probe in the duodenum are propagated through the abdomen.

The sounds are recorded by eight Thinklabs ds32a stethoscopes positioned at known locations. Results: The sample standard deviations are calculated for the single delays in order to identify variance. In general a high sample standard deviation was found, but a distinctly higher was found in the abdominal experiment. It is concluded that the system is affected by imprecise measurement equipment. The main imprecision however, is assumed to be related to the influence of abdominal gasses. Discussion: In order to use TDoA for obtaining 3-D location of abdominal sounds, it is required to build a useful model describing abdominal velocity changes. This is assumed to be a difficult task. There also exist other practical problems, like displacements of the stethoscopes associated with breathing, which must be addressed in order to create a functional system. References: [1] Craine BL, Silpa ML, O'Toole CJ. Two-dimensional positional mapping of gastrointestinal sounds in control and functional bowel syndrom patients. Dig Dis Sci. 2002; 47: 1290–1296. [2] Valin JM et al. Robust sound source localization using a microphone array on a mobile robot. Proceedings IEEE/RSJ IROS 2003. 2003; 2: 1228-1233.

UNSUPERVISED METHOD TO CLASSIFY MOTOR UNIT ACTION POTENTIALS ONLINE

Suzan de Goede**, Lars Johannesen*, Jens Stampe Sørensen Group 705b

Introduction: Spike-triggered stimulation has been used to characterise spinal reflex pathways. To perform spike-triggered stimulation, a method for online detection and classification of motor unit action potentials (MUAPs) from intramuscular electromyography (EMG) is required. At present, different supervised alternatives for performing spike triggered stimulation are available. In this paper an unsupervised method to detect and classify MUAPs based on simple features is proposed.

Method: The proposed method uses five features: root mean square, distance to maximum, number of turns, minimum slope and mean frequency. An unsupervised modified k-windows algorithm [1] is applied to the 5-dimensional feature space to identify clusters, which represent different MUAP shapes. When the clusters and their boundaries are found, a cluster can be selected and used for online triggering. The method was implemented as a DLL using C/C++ and used in a program created with LabVIEWTM 8.5 for recording and visualisation of the classification. To examine the program’s performance with respect to the specificity, sensitivity and false alarm rate, it has been tested offline using signals of different complexity. Signals were recorded on the tibialis anterior muscle of 2 healthy male subjects (ages 22 and 23).

Results: Detection specificities of 97%, 99%, 99% and 99% were found in signals with 2, 3, 4 and 6 active firing motor units (MUs), respectively. The corresponding sensitivities of detection were 37%, 27%, 19% and 18%. The maximum false alarm rate was 16 % in signals with 6 active firing MUs, while the minimum false alarm rate was 6% in signals with 1 active MU.

Discussion: The results indicate that the method is able to correctly detect and classify MUAPs online. Signals containing between 1 and 4 active MUs have an acceptable false alarm rate. The detection threshold can be improved, which could result in lower false alarm rates.

References: [1] D. Tasoulis, D. Zeimpekis, E. Gallopoulos, and M. Vrahatis, “Oriented k-windows: A PCA driven clustering method,” University of Patras, Tech. Rep., feb 2006.

CORRELATIONAL STUDY BETWEEN THE SEVERITY OF CAROTID STENOSIS AND BIO-ACOUSTIC FEATURES

Markus Mühlbacher-Karrer**, Majken Munch, Michael Svorkmo* and Chiara TrentinGroup ST-705c

Introduction: Carotid artery stenosis (CAS) raises the risk of stroke as it can rupture and cause thrombo-embolic events. Symptoms for CAS are rare apart from the actual stroke. Because of this, easy available diagnosis techniques are needed by the general practitioner to give an early assessment of the patients' risk of stroke. A possible diagnosis technique is the analysis of bio-acoustic recordings from an electronic stethoscope. This is based on the theory that stenosis causes turbulent flow which makes the vessel wall vibrate generating characteristic bruits that are recordable at the skin surface [1].

Method: 21 recordings from patients with known stenosis degree, have been analysed with 5 different approaches, to find useful bio-acoustic features[2]. This resulted in the following possible features: a) break frequency b) mean frequency c) kurtosis and skewness d) angles and amplitude of poles from the AR model e) pseudo-frequency of the zero crossing. Tests with closeness and ANOVA were performed on the single features bruits and on their average per recording, to find good candidates. Tests with multiple linear regression models were applied on the averaged features.

Results: RMS evaluation on the MLR test reduced it to a single LR-model on the mean frequency. The Correlation Coefficient on that model was -0.0773 with a p-value = 0.8319. ANOVA test showed a rejection of the null hypothesis in 60% of the cases for the single bruit features and none for the averaged features. The closeness test indicated that 60% of the features can differentiate between stenosis degree 20-49% and 80-99% and that 40% can differentiate between stenosis degree 20-49% and 50-79% for the single features bruits. None of the features showed capability to differentiate between 50-79% and 80-99% degree.

Discussion: The quality of the chosen bio-acoustic features did not support classification by degree. The recording quality of the available data made it impossible to extract bruit signals for every stenosis degree, which affected the results of the later analyses negatively.

References[1] Ask P., et al. Bio-acoustic signals from stenotic tube flow: state of the art and perspectives for future methodological development. Med & Biol. Eng & Comput., 1995.

[2] Rangaraj M. Rangayyan. Biomedical Signal Analysis. IEEE Press, 2002.

AUTOMATED DETECTION OF BRUGADA SYNDROME

Ulrik Silvanus Lerkevang Grove**, Lisbeth Lundager Gylstorff, Tine Maria Hansen, Ask Schou Jensen* and

Thomas Worbech

Group 705d

Introduction: The Brugada Syndrome is a hereditary disease caused by myocardial sodium ion channel

defect and it is associated with syncopal episodes and high risk of sudden cardiac death. The syndrome is

characterized by a particular morphology of the electrocardiogram (ECG) [1], but systems for the automatic

detection of Brugada Syndrome do not exist in clinical practice. The aim of this study was to develop such a

classification system by applying pattern recognition techniques to ECG recordings.

Methods: Training data: 4 subjects (28 ECG recordings) with Brugada Syndrome, Type 1, (3M, 1F) and 200

healthy subjects (183M, 27F). Blinded test data: 4 subjects (38 ECG recordings) with Brugada Syndrome,

Type 1, (3M, 1F) and 200 healthy subjects (167M, 33F). 135 features were extracted from the ECG

recordings based on six categories: Duration, area, amplitude, slope, variance and symmetry of various

points and segments. By quantitative and qualitative analysis of feature effectiveness, two features were

selected. One feature described the asymmetry of the ST-segment. The other feature described the J-point

elevation by the area under the ECG curve. A classification system was implemented through linear

discriminant analysis.

Results: For the training data complete separation was achieved. A blinded test of the system resulted in a

sensitivity of 0.75 and specificity of 0.99, a positive predictive value of 0.778 and a negative predictive value

of 0.998. A t-test showed statistically significant differences between healthy subjects and subjects with

Brugada Syndrome for: Asymmetry: 1.03 [95% CI, two sided: 0.87 to 1.20] p < 0.001, J-point area: 3.27 [95%

CI, two sided: 2.84 to 3.70] p < 0.001 and discriminant score: 6.39 [95% CI, two sided: 5.65 to 7.13] p <

0.001.

Conclusion: The asymmetry of the ST-segment and the J-point area are promising features for the

automatic detection of Brugada Syndrome, Type 1. Further work and more data is necessary in the

development of a classification system.

References: [1] Wilde et al. Consensus report - proposed diagnostic criteria for the Brugada Syndrome.

European Heart Journal 2002; 23: 1648-1654.

IDENTIFICATION OF PATIENTS SUFFERING FROM CENTRAL SENSITIZATION BY PRINCIPAL COMPONENT ANALYSIS OF

NOCICEPTIVE REFLEX RECEPTIVE FIELDSMichael Brun Jensen

Group 705e

Introduction: Central sensitization describes underlying neuronal mechanisms behind exaggerated pain to noxious and tactile stimuli [1]. Recently Neziri et al. have developed a method for quantification of nociceptive reflex receptive fields (RRF) in humans [2]. This might be a robust non-invasive method for assessing central sensitisation in humans. Present study investigated whether it is possible to identify patients suffering from central sensitization by applying pattern recognition on descriptive features of the RRF.

Methods and Material: Present study was performed on data from 300 healthy subjects and 17 chronic pain patients [3]. Electromyography of tibialis anterior simultaneously to distributed electrical stimulation enabled calculation of an interpolated sensitivity map. Physiological derived features quantifying size and location of the RRF was calculated from the sensitivity map. Three supplementary feature sets were derived by applying principal components analysis (PCA) on the sensitivity map and the physiological derived features respectively and following merge the two resulting feature sets. Pattern recognition classifiers were designed as linear discriminant functions using a batch perceptron algorithm [4].

Results: The probability distribution of the RRF area was rather flat, however exhibiting a high frequency of RRFs constituting (almost) the entire sole of the foot. The probability distribution of the physiological derived features for pain subjects and control subjects was overlapping. PCA of the sensitivity map reduced the dimensionality of the feature set to 10 preserving 100.0% of the variation in data. None of the four classifiers resulted in less than 17 misclassifications.

Discussion: The suspicious probability distribution of the RRF area questions the validity of the method used for feature extraction. This calls for a revision of the applied threshold and suggests the need for a pragmatic definition of the RRF dissimilar to the physiological in order to achieve discriminative features. The very poor performance of the classifiers illuminating their inability to identify the chronic pain patients may be due to the great interpersonal variance and application of the procedure in a time-series experiment could be of great interest.

References:[1] Woolf CJ, Salter MW. Neuronal plasticity: increasing the gain in pain. Science. 2000; 288: 1765-9.[2] Neziri AY et al. J Neurosci. Meth. In press.[3] Neziri AY et al. Swiss Med. Weekly. 2008; 138 (Suppl. 166): S 3.[4] Duda et al. Pattern Classification. Wiley, 2006.

Brain atrophy in subjects with mild cognitive impairment and Alzheimer’s disease compared to normal cognitive subjects

Morten Schøler Krisensen**, Anders Holch Heebøll-Holm*, Yang Li, Kenneth Andersen

Group ST7 08gr706a

Introduction: Alzheimer's disease (AD) is one of the most common forms of dementia. It affects several areas of the brain causing neuro degeneration [1]. In practice, it is diagnosed through thorough neurophysiologic and neuropsychological examinations, a mini mental state examination (MMSE) and magnetic resonance imaging (MRI). MRI can be used to visualise the brain in sagittal, transverse, and coronal plane, thus the anatomical and physiological information can be provided [2, 3]. Methods and material: MRI data for 58 subjects was collected from the Alzheimer's disease neuroimaging initiative (ADNI) database. All subjects were scanned using a 1.5 Tesla MR scanner with the magnetisation prepared rapid gradient-echo (MP-RAGE) sequence. Classifying the subjects into normal cognitive (NC), mild cognitive impaired (MCI) and AD was done by ADNI. This study included 26 subjects with NC, 16 subjects with MCI and 16 subjects with AD. Utilising fuzzy c-means, cerebrospinal fluid (CSF), gray matter (GM) and white matter (WM) were extracted from skull stripped datasets. Volumes of CSF, GM and WM were calculated, and normalised by intra cranial volume (ICV). Comparison and analysis of normalised volumes were performed by using an unbalanced one-way ANOVA and two sample t-tests. Results: QQ-plotting indicates normal distribution. The unbalanced one-way ANOVA showed that there is no significant difference either in normalised CSF volume or in normalised WM volume among the three groups (p > 0.05), while it showed a significant difference in normalised GM among the three groups (p < 0.05). Furthermore, two sampled t-tests showed a significant difference between NC and MCI (p < 0.05), and a significant difference between NC and AD (p < 0.05). Discussion: The results showed a significant difference only in GM but not in CSF and in WM for AD and MCI compared to NC. The brain tissue that diminishes is replaced by CSF, so difference in CSF was expected. The possible reason of that there was no difference found could be the inadequate quality of the skull stripped datasets, or the use of the global volumes, since little change will be insignificant, thus suggesting examination of changes of local volume. References: [1] G. F. Busatto, G. E. Garrido, O. P. Almeida, C. C. Castro, C. H. Camargo, C. G. Cid, C. A.

Buchpiguel, S. Furuie, and C. M. Bottino, “A voxel-based morphometry study of temporal lobe gray matter reductions in Alzheimer’s disease” Neurobiology of Aging, vol. 24, pp. 221–231, 2003.

[2] A. Du, N. Schuff, D. Amend, M. Laakso, Y. Hsu, W. Jagust, K. Yaffe, J. Kramer, B. Reed, D. Norman, H. Chui, and M. Weiner, “Magnetic resonance imaging of the entorhinal cortex and hippocampus in mild cognitive impairment and Alzheimer’s disease” Journal of Neurology, Neurosurgery, and Psychiatry, vol. 71, pp. 441–447, 2001.

[3] G. Chetelat and J.-C. Baron, “Early diagnosis of Alzheimer’s disease: contribution of structural neuroimaging”, NeuroImage, vol. 18 pp. 525-541, 2003

Global and Regional White Matter Atrophy in

Alzheimer's Disease

Vibeke Hvarregaard Andersen**, Natasja Spring Ehlers*, Anja Olesen

Group ST‐706b

Introduction: The purpose of this study is to find to what extend atrophy occurs in white matter (WM) regions in the brain of patients with Alzheimer's disease (AD) and to find to what extend decline in WM volume develops over time and how it correlates with mini‐mental state examination (MMSE) score and age. There seems to be consensus that gray matter (GM) atrophy is more severe in AD patients compared with healthy controls (HC) [1]. It is uncertain whether WM is affected during AD [1,2]. Knowledge, on which WM areas are affected by AD, combined with knowledge on GM atrophy and cognitive symptoms may provide a better understanding of AD.

Methods and Materials: Nineteen AD subjects and 26 HC were included in a cross‐sectional study. All subjects were evaluated using MMSE score, and scanned with a MR scanner, T1 weighted. Nine AD subjects and 10 HC were included in a retrospective longitudinal study where the progression of global and regional atrophy was correlated with MMSE and age during one to two years. A semi‐automatic region growing algorithm with automatic seed point placing was developed to segment and calculate the volume of WM in MR images in selected regions of the brain.

Results: Significant difference in WM volume between the AD and the HC group was found in the limbic lobe in the cross‐sectional study. For the longitudinal study a decline in global WM volume was found in both the AD and the HC group from first to third scan, with the AD group showing greater atrophy. Furthermore correlation was found between global WM volume and MMSE in AD subjects.

Discussion: For the cross‐sectional study the results from the AD group compared with the HC group, supported the literature [3]. The results in the longitudinal study indicated that more significant results could be obtained if study design (length and sample size) and processing methods were improved.

References:

[1] Thompson et al. Dynamics of gray matter loss in Alzheimer's disease. The Journal of Neuroscience, 2003; 23; 994‐1005. [2] Roher et al. Increased aβ peptides and reduced cholesterol and myelin proteins characterize white matter degeneration in Alzheimer's disease. Biochemistry, 2002; 41; 11080‐11090. [3] Braak et al. Vulnerability of cortical neurons to Alzheimer's and Parkinson's diseases. Journal of Alzheimer's Disease, 2006; 9; 35‐44.

Semi-Automatic Registration of CT and MR Images using a New Fiducial

Marker

Ditte Haargaard Kopp, Rasmus Holland* and Kate Zeberg Olesen**

Group ST-706c

Introduction Prostate cancer is a common male cancer disease with an incidence of 95

new diagnosis per 100,000 in Europe in 2005 [1]. In order to improve the radiation treatment

a clinical target volume is de�ned from a registration of CT and MR images. The aim of

this study was to develop a semi-automatic registration of CT and MR images by using a

stent as a new �ducial marker. The stent was placed in the ureter of the prostate where it

remained during the whole treatment period.

Materials and Methods The stent is �exible and stable which makes it a good marker

[2]. Three patients with histologically veri�ed local or locally advanced prostate cancer was

participating in this study. T2-weighted MR (0.55×0.55×5 mm) and CT (1.27×1.27×2.5

mm) images were available in the axial plane. Active contour modelling deforms a straight

line drawn between two points found on the top and bottom of the stent, in order to extract

the skeleton of the stent. Iterative closest point (ICP) method was used for registration of

the skeleton stent in CT and MR images. The ICP �ts the MR stent skeleton to the CT

stent skeleton using only a rigid transformation, according to the criterion that the distance

between the two skeletons must be as small as possible [3]. To evaluate the transformation

of the stent a point in the top and bottom of the stent was transformed from MR to CT.

Furthermore a transformation was done on a whole image set.

Results Transformation of the stent revealed a su�ciently accurate registration as the

stent was in the same position in both CT and MR images. Furthermore the soft tissue

nearest the stent, i.e. the prostate, was almost in an identical position in both data sets.

Discussion ICP is a rigid model-based registration technique used to �nd the transforma-

tion matrix. It rotates and translates the image sets. This is important as it is necessary to

retain the shape of the prostate. The prostate can rotate up to 20 degrees, which means that

the ICP method will use a counter rotation. This rotation can result in a bad registration

of the outer anatomy whereas the stent and prostate should be registered correctly.

References [1]Cancer Research UK, 2008, http://info.cancerresearchuk.org/cancerstats/types/prostate/.

[2] Carl et al., A new �ducial marker for Image-guided radiotherapy of prostate cancer:

Clinical experience, Acta Oncologica, 47: 1358-1366, 2008.

[3] Besl et al., A Method for Registration of 3-D Shapes, IEEE Xplore, 14: 239-256, 1992.

2

BLOOD VESSEL SEGMENTATION FOR IMAGE-GUIDED RADIOTHERAPY IN CERVICAL CANCER

Ann Merete Duedal Jensen, Merete Martlev Jensen**, Anne Sofie Korsager*,

Rikke Kristensen and Mick Lykkegaard Schmidt Group 706d

Introduction: One of the main focuses in radiotherapy of cervical cancer is to treat lymph nodes that lie adjacent to the iliac arteries. Today there is no validated method for segmenting blood vessels in the pelvis [1]. The aim was to segment the iliac arteries and the branches that supply the uterus and thereby locate the lymph nodes. Methods and Material: Four T2 weighted MR data sets from patients with cervical cancer were available. To intensify the blood vessels in 3D images a multiscale vessel enhancement filter, suggested by Frangi et al. [2], was used. A region growing method was used for the segmentation. To make use of most possible information, a combination of the filtered and the original data set was applied in the region growing. It was evaluated how well the region fitted the vessel wall and how much of the iliac and its branches that were possible to segment. The performance of the final segmentation was compared to the performance when segmenting a filtered data set. Results: It was observed that 739 more voxels were included in the region when using the filtered data set compared to when combining both the original and filtered data set. The region in the filtered data set had 2251 voxels that the combined data set did not, and the combined data set had 2990 voxels that the filtered data set did not. Variability was observed in how well the region fitted the lumen of the vessel. In the final segmentation the common iliac arteries and a part of the internal and external iliac arteries could be segmented. Discussion: It occurs that the performance is better when using a combination of filtered and original data sets, since this region fitted more to the vessel wall. The fact that the region growing does not segment the branches of the internal iliac, and that the fitting to the lumen of the vessel varies is problematic if the segmentation should be used in planning of radiotherapy. The small number of data sets and their quality proved to be a problem when segmenting the blood vessels. References: [1] Taylor et al. International journal of radiation oncology, biology, physics. 63:1604-612, 2005. [2] Frangi et al. MICCAI’98. 1496:130-137,1998.

RELIABLE IDENTIFICATION OF RFID TAGS USING MULTIPLE INDEPENDENT READER SESSIONS

Rasmus M. Jacobsen** and Karsten F. Nielsen*Group 08gr710

Introduction: The deployment of Radio Frequency Identification (RFID) systems is gaining a strong momentum in various applications of logistics, inventory, tracking, etc. A generic problem in such systems is to ensure that the RFID readers can reliably read a set of RFID tags in their proximity, i.e. ensure with some probability a tag is not missed. The reliability is challenged by the errorprone wireless communication link between a tag and a reader, such that there is a nonzero probability that a tag cannot be read, i.e. a missed tag, due to e.g. obstacles in the radio path towards the reader.

Methods and Material: The present paper leverages on the recent idea about cooperative readers [1], and extends this method and shows a technique where the use of several reader sessions can be used to reduce the probability of missing tags, by providing a running estimate of this probability. For this an estimate of the error probability for the wireless link and for the tag set cardinality is needed. These estimates rely on obtaining independent, uncorrelated tag sets in each reader session. There may be correlation between the tag sets, and simulations show how this causes the correctness of the estimates to decrease, which can lead to an incorrect guarantee of not missing a tag. Ideas to overcome this are presented which involves adding an estimation margin to the estimated probability of missing a tag.

Results: Two different techniques are proposed and evaluated for obtaining the error probability estimate and the tag set cardinality estimate. The first method is based on the statistical relationships that are valid when the reader sessions are assumed to be independent. The second method is obtained by modifying a known capturerecapture estimator for the tag set cardinality [2], to provide an estimate for the error probability.

Discussion: The proposed methods are useful in many applications requiring reliable estimation of RFID tags, such as in the industry for tracking and logistics of items in the supply chain.

References[1] P. Popovski, "Tree Protocols for RFID Tags with Generalized Arbitration Spaces," Spread Spectrum Techniques and Applications, pp. 1822, Aug. 2008.[2] Z. E. Schnabel, "The Estimation of Total Fish Population of a Lake," The American Mathematical Monthly, vol. 45, no. 6, pp. 348352, 1938.

USE OF FEATURES EXTRACTED FROM MR IMAGES TO CLASSIFY SUBJECTS WITH

RESPECT TO THE CLASSES; CONTROL, MILD COGNITIVE IMPAIRMENT AND

ALZHEIMER’S DISEASE

Mette Jensen, Rikke Beck Nielsen*, Heidi Klitgaard Pedersen og Sinna Pilgaard Ulrichsen**

Group 706e

Introduction: The aim of this study was to examine whether different structural changes in the brain, could

be a sign of Alzheimer’s disease, (AD). One of the structural changes considered in this study was the

volume of the ventricles, which increases with the progression of AD [1]. An earlier diagnosis based on

structural changes in the brain would induce earlier treatment and thereby a longer and more functional

life for the patients.

Methods: Data consisted of 3D, T1-weigthed MR images, from the ADNI database, of 57 subjects, divided

into 3 groups. An image segmentation algorithm using region growing and morphological operations was

used to isolate the lateral ventricles and calculate the volume.

Fisher’s linear discriminant function was used to classify the subjects into groups, sensitivity and specificity

was evaluated from the number of misclassified subjects. Besides the ventricle volume and other features

from a given dataset was used [2] [3].

Results: After the segmentation the ventricle volumes of the subjects were: AD (35945 ± 21485 mm3),

MCI(25366 ± 18293 mm3) and Controls(19520 ± 13452 mm3). Superimposing the found ventricle image on

the original MR image indicated that the ventricle segmentation size was correct.

Fisher's linear discriminant function classified 24 as controls where 4 were misclassified, 16 as MCI where 6

were misclassified and 16 with AD were 4 was misclassified.

Discussion: Based on the results it is possible to make a classifier that can detect MCI and AD, using

features extracted from MR images. In this connection, the structural changes in the brain are the changes

of the cortex thickness, the cortex volume, the ventricle volume and the mean of the 10% smallest

curvature measurements. The question of whether the classifier can be used to diagnose AD earlier than

the standard diagnose methods is still open and requires further research.

References:

[1] Tanabe et al. Tissue segmentation of the brain in Alzheimer’s Disease. AJNR . 1997. 18: 115-123.

[2 ] Simon Eskildsen and Lasse Østergaard. Active surface approach for extraction of the human cerebral

cortex from MRI. MICCAI : 9th International Conference, 2006, Copenhagen.

[3] Simon Eskildsen and Lasse Østergaard. Quantitative comparison of two cortical surface extraction

methods using MRI phantoms. In MICCAI : 10th International Conference, 2007, Brisbane, Australia.

Proceedings.


21TH SEMCON 19TH OF DECEMBER, 2008

SCIENTIFIC METHODS AND COMMUNICATION (SMAC)

PROGRAMME AT GLANCE: During Poster Viewing sessions at least one author should be present at the poster, to explain and discuss the idea and results of the project with other participants.

Time Room B3‐104 Room B2‐104 Room B2‐109 Room A4‐108 Room A4‐106

08.00‐08.15 Poster Mounting Poster Mounting Poster Mounting Poster Mounting

08.15‐08.20 Conference opening






12.00‐12.30 Lunch Lunch Lunch Lunch Lunch



13.10‐14.30 Poster Session Poster Session Poster Session Poster Session

14.30 Conference closing

Department of Electronic Systems, Department of Health Science and Technology &

Aalborg University Esbjerg Aalborg University Fredrik Bajers Vej 7

Aalborg Ø Denmark


21th semcon 19th of december, 21th semcon · kartheepan balachandran, martin andersen, rasmus...

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