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Networked Control Systems (NCSs) use a wireless network for communication between sensors and controllers, and require a Medium Access Controller (MAC) to arbitrate access to the shared medium. Traditionally, a MAC for control systems is chosen primarily based on the delay it introduces in the closed loop. This thesis focuses on the design of a contention-based MAC, in a time-varying, resource-constrained network for closed loop systems. In this thesis, we advocate the use of a state-aware MAC, as opposed to an agnostic MAC, for NCSs. A state-aware MAC uses the state of the plant to influence access to the network. The state-aware policy is realized using two different approaches in the MAC: a regulatory formulation and an adaptive prioritization. Our first approach is a regulatory MAC, which serves to reduce the traffic in the network. We use a local state-based scheduler to select a few critical data packets to send to the MAC. We analyze the impact of such a scheduler on the closed loop system, and show that there is a dual effect for the control signal, which makes determining the optimal controller difficult. We also identify restrictions on the scheduling criterion that result in a separation of the scheduler, observer and controller designs. Our second approach is a prioritized MAC that uses state-based priorities called Attentions, to determine access to the network. We use a dominance protocol called tournaments, to evaluate priorities in a contention-based setting, and analyze the resulting performance of the MAC. We also consider a NCS that uses a wireless multihop mesh network for communication between the controller and actuator. We design an optimal controller, which uses packet delivery predictions from a recursive Bayesian network estimator. / QC 20110216

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This thesis focuses on the understanding and computation of the dispersion properties of periodic structures possessing higher symmetries with the multimodal transfer matrix method (MMTMM). Periodic structures with higher symmetries are invariant after additional symmetry operations over the translation operation. To demonstrate the potential of the MMTMM, three structures with spatial higher symmetries are proposed and their operation explained based on the constituent modes.  In this thesis, I propose, analyze and explain the operation of two structures possessing glide symmetry and one with twist symmetry. Glide-symmetric structures remain invariant after a mirroring and a translation whereas twist-symmetric structures remain invariant after n rotations and translations. These structures inherently have low dispersion due to the interactions of the fundamental mode with higher order modes. The MMTMM has been implemented in order to efficiently compute the complex propagation constant of these structures. This is a hybrid method that models a unit cell as a multiport network. Each port accounts for one mode, so the coupling between modes is considered. Commercial software is used to compute the ABCD-matrix, then post-processing is used to get both the phase and attenuation constant due to material losses, electromagnetic bandgaps and/or radiation. This method permits the study of complex structures while enabling a fundamental understanding of the modes that contribute to the dispersion properties, as well as their interactions.  The first periodic structure analyzed in this thesis is a dielectric-filled corrugated waveguide. It allows the propagation of a backward mode in a wide frequency band. A discussion on the convergence of the method concludes that it is needed families of TE/TM modes with the same number of variations in the x direction.  The second structure is a glide-symmetric dielectric unit cell placed in a parallel plate waveguide. This unit cell can be used to produce planar lens antennas that can be cost-effectively manufactured with dielectric 3D-printers. The attenuation constant due to material losses in two different directions is computed using the MMTMM. Finally, a 3-fold twist-symmetric dielectric open waveguide is analyzed. Its interest lies in its inherent circular polarization selectivity. Here, the MMTMM is used to compute the attenuation constant from material losses and the stopband, as well as to understand the interaction between linear and circularly polarized modes. / <p>QC 20220926</p>

The primary challenge in expanding the wireless power transfer range for miniaturized self-powered micro devices is the limited RF energy harvesting due to the small effective area and low gain of the mm-sized antennas used in these devices. This thesis introduces a method for extending the distance between an external energy source antenna (TX) and a micro-device antenna (RX) to more than 10 cm. This method employs various TX antennas, such as a conventional loop antenna, multiple patch antennas, and a rectangular cavity antenna, in conjunction with a 2-turn double-sided square loop RX antenna, sized 1.2mm x 1.2mm on an FR4 substrate, which can be mounted on a CMOS SoC. The wireless power transfer link's performance is assessed and contrasted under various conditions. In the 434 MHz ISM band, the highest peak power transfer efficiency of $-$20 dB and the highest harvested DC voltage of 4 V through an 8-stage Dickson RF-DC converter are achieved within a 49.6cm x 49.6cm x 30.4cm rectangular hollow cavity, serving as the TX, with an input TX power of 20 dBm. Moreover, the multiple patch antennas exhibit a power transfer efficiency of -39 dB and a harvested DC voltage of 2.5 V at a 10 cm distance with an input TX power of 37 dBm. The specific absorption rate for both scenarios remains under the limits set by IEEE. The feasibility of incorporating a rectangular cavity in backscatter communication is demonstrated in this study, although the cavity's filtering characteristics present certain challenges.

In this thesis, a different method for creating acoustic pulses that can be used in the ultrasonic spectrum is proposed. The aim is to develop a robust and reliable system that uses ultrasonic techniques, such as transit time or sing-around, to measure gas flows in extreme environments. Extreme environments involve high temperatures, contaminating dust and sometimes high moisture content. The investigated method in this work utilizes electric spark discharges to generate acoustic pulses. Studies of the gap discharge acoustic emitter were performed in two parts: environmental tests and studies of the transmitted sound. Environmental tests were performed at industrial sites to test the gap discharge emitter when exposed to heavy surface contamination and moderate temperatures. Studies of the transmitted sound were performedwith a primary focus on the time stability of the emitted sound. Due to the nature of the spark discharge phenomena, there are inconsistencies in the transmitted acoustic pulse. When pulses are transmitted and received consecutively, their measured travel times will contain a time jitter relative to each other. This jitter is investigated and put into the perspective of a gas flow measurement situation. Acoustic pulses from the gas discharge emitter are shown to be strong enough to be used in large geometries of several meters. Additionally tests were performed in the industrial environments to determine if the acoustic pulses can be sent through large gas flow ducts and detected at the oppositeside.The tests show that the gap discharge transducer at the prototype stage performs well in a real industrial environment. The emitter continues to work when subjected to heavy contamination. The emitted sound is loud enough to be detected using standard piezo ceramic ultrasonic transducers when sent through large gas flows (air). If used in measurement situations that involve acoustic travel paths longer than around 1.5 meters and gas flows in the range of a few m/s or larger, this emitter can deliver sufficient accuracy.

A way of describing photoacoustic measurement techniques is listening to light. Another way is as sensor techniques for characterisation of materials by means of light and sound interacting with the material under investigation. Photoacoustic measurements are emerging techniques and examples and suggestions of applications can be found foremost in diagnostics for medical purposes but also for industrial materials.The photoacoustic measurement techniques used in present thesis is based on the thermoelastic effect. A short light pulse is sent into a material, and energy from the light being absorbed leads to a localised heating. If the duration of the heating is short enough, a local pressure wave is built up, that propagates through the material as an ultrasonic pulse which can be detected by an ultrasound transducer and subsequently analysed.In photoacoustic measurement techniques, the advantage of high spatial resolution from measuring with ultrasound is combined with the advantage of high contrast from measuring with light. Ultrasound propagating in for example human tissue scatters less than what light does, enabling more precise positioning of the origin of the information in the measured signal. High spatial resolution is thereby achieved from measuring with ultrasound. High contrast can be reached from dierent responses to light in materials with diverse light absorption coecients. However, a disadvantage of the technique is that in biological tissue, light scattering is limiting the practically usable penetration depth.Besides for photoacoustic measurements, the thermoelastic effect can be utilised to generate laser-induced ultrasound for measurement applications. The present thesis' contribution is studies of laser-induced ultrasound in a thin semitransparent light-absorbing layer, experimentally and theoretically. To draw conclusions from measurements, one wish to know more about what happens in the absorbing layer, knowledge that could also be applied on corresponding processes in a material under study. An analytical model could thereto constitute a base for ultrasound pulse shaping, for adjusted measurements for specific applications.Through experiments on dyed polymer film, frequency spectra of laser-induced ultrasound were studied, varying thickness and light absorption coecient of the film layer structure. In the outcome of the experiments, decreased thickness was related to increased centre frequency as well as increased bandwidth of the generated ultrasound, and increased absorption together with decreased thickness was related to increased ultrasound amplitude.A one-dimensional analytical photoacoustic wave model of generation and propagation of heat-induced ultrasonic pressure wave in three material layers has been developed. From an existing model of three layers, this is an expansion enabling the two materials surrounding the light absorbing layer to be dierent. The analytical solution to the photoacoustic wave equation problem was based on a Laplace transform approach. Pressures resulting from the analytical model corresponds well to results from simulations. Analytical pressures were compared to ultrasound transducer experimental voltages, through system identication of the transducer system conversion between pressure and voltage. The system identication was however unstable. For ultrasound reception, experiments were performed on piezoelectric film with electrically conductive coatings as a transducer.

The Partial Element Equivalent Circuit (PEEC) method is an integral equation based full-wave approach to solve combined circuit and electromagnetic problems in the time and frequency domain. Using PEEC, an electromagnetic problem is transferred to the circuit domain and then solved using circuit theory which gives PEEC a high flexibility to be used in combined electromagnetic and circuit modeling problems. Thus, the method can be applied to different classes of problems, for example power electronics systems and antenna simulation to ensure the functionality of the system and also comply with electromagnetic compatibility (EMC) regulations. Other methods, like Finite Element Method or Finite Difference Time Domain Methods, are also used for electromagnetic analysis and an optimal computer implementation is needed to be able to handle such problems within a reasonable time and at certain accuracy.This work presents the development and optimization of a PEEC-based software on different computing platforms. The aim of the acceleration is to be able to solve problems using the PEEC method as fast as possible with optimum memory usage on a regular computer system. The PEEC-based solver has been developed for desktop machines using the GMM++ linear algebra package. This implementation was optimized by improving the code, to use more efficient libraries and adapt the program to run on powerful machines. Another part of this optimization process was to implement smart algorithms like non-uniform meshing and on-the-fly calculations for the partial elements. Though, the code has been recently enhanced to take advantage of the multicore hardware by replacing old library with Intel Math Kernel Library (MKL) in order to take advantage of several processors which exist on typical computer system.To be able to solve very large problems which for example needs several hundred gigabytes of memory, the code was also ported into parallel computer systems. The parallel PEEC solver is compatible with the distributed memory architecture and thus, is scalable by using a set of computing units which collaborate to solve a problem. Hence, by allocating enough number of processors and amount of memory, the load of the solution will be distributed over different elements. Consequently, one of the challenging parts of these kinds of distributed computations is to distribute data, using a balanced manner to minimize data movement between nodes which will slow down the running process. The balanced distribution of data was ensured, by using Basic Linear Algebra Subprograms (BLAS) and Scalable Linear Algebra Package (ScaLAPACK) libraries to handle linear algebraic calculations in the parallel solver. Using these tools, the matrix elements are dispensed according to the block-cyclic decomposition scheme which guarantees that data is uniformly assigned to each computing node. Several test cases have been run, in order to benchmark the computer implementation. On account of the applied optimization techniques, the sequential solver needs less memory and performs the solution remarkably faster than before. As an example, high frequency simulations can now be run now with the optimized code, within shorter time and with less memory usage, by having very light mesh, using non-uniform meshing. According to the benchmarking results of the parallel solver, the results of these tests did agree very well with the physical measurements and also showed an acceptable speed-up factor as number of processors as well as size of the problems grew in the parallel version of the solver. The robustness of the parallel solver was verified by stressing the code with the largest test case which was a problem with more than 250 000 unknowns. Further steps of the acceleration would be focusing on the smarter algorithms as well as numerical methods like Fast Multipole Method (FMM), using iterative solvers instead of direct solvers and QR Decomposition. An important issue which needs to be considered is the approximations which will appear in the results as a consequence of usage of such techniques like numerical instabilities and loss of accuracy. / Kretsbaserad lösare för elektromagnetisk analys av kraftelektroniksystem- Applikation mot IGBTmoduler

The overall fuel efficiency of district heating could clearly be improved by using new strategies for measurement and control. The potential for improvement is on the order of several percent. Keeping in mind that district heating makes up ~50% of the Swedish heating market (5 billion euro total turnover) which in turn is about 1% of the total world market, such improvements would be of global importance both from financial and environmental viewpoints.The energy transfer from the distribution network to space heating and tap water systems is done at a district heating substation. To maximize energy effciency in the district heating network and minimize primary fuel source usage, it is essential to have maximum utilization of produced heat. This means that a large temperature drop (Delta T) across the substation is of utmost importance. This is related to the fact that the same amount of heat energy can be transferred with a decreased flow, if the temperature difference (Delta T) between incoming and returning water is increased. This makes Delta T a very important factor in making district heating more effcient.Today, substation control systems focuses on indoor comfort and do not generally consider Delta T, since it is not measured by the control system, however, Delta T is measured by the energy meter used for billing.This thesis proposes an alternative way to control a district heating substation, wherein wireless sensor and actuator technology together with a service oriented architecture are used. This technology allows different devices, such as the energy meter, circulation pump, and control valve, to share information without restrictions and thus increase the control possibilities.To test the new control strategies, a complex thermodynamic computer model of a building with an included district heating substation was developed for simulation. The thermodynamic model was complemented with models of battery-powered wireless devices to predict the sensor lifetime. A field experiment was also carried out wherewireless platforms were retrofitted into commercially available components used in district heating substations. The complete setup is currently mounted in a villa for continued research.The results of my research so far have proved that there is great potential for increasingDelta T and for additional services if new sensor technology is applied. / Genom förbättrade mät- och reglerstrategier kan energieffektiviteten i fjärrvärmenät förbättras med flera procent. Då Sveriges värmemarknadsvärde idag uppgår till ca 5 miljarder euro, varav ca 50% utgörs av fjärrvärme, vilket vidare utgör ca 1% av den totala världsmarknaden för fjärrvärme, skulle sådana förbättringar utgöra substantiella vinster ur både finansiell och miljömässig synvinkel.Värmeöverföringen från fjärrvärmenätet till den slutliga användningen, så som rumsuppvärmning och varmvattenproduktion, görs i en så kallad fjärrvärmecentral. För att maximera energieffektiviteten i fjärrvärmenätet, och minska den primära bränsleanvänd-ningen, är det viktigt att utnyttja den levererade värmeenergin på bästa möjliga sätt i fjärrvärmecentralen. Detta betyder med andra ord att avkylningen, Delta T, över fjärrvärme-centralen skall eftersträvas att hållas så hög som möjligt. Detta hänger ihop med att samma mängd energi kan överföras med mindre volym vatten om Delta T ökas. Detta gör Delta T till en mycket viktig faktor i processen att energieffektivisera fjärrvärmenäten.Dagens fjärrvärmecentral-reglersystem fokuserar enbart på att upprätthålla en god inomhuskomfort, och tar ej hänsyn till att samtidigt maximera avkylningen. Reglersystemet har vanligtvis ej heller någon vetskap om temperaturer eller flöden på primärsidan (fjärrvärmenätets sida) av fjärrvärmecentralen, denna information finns dock tillgänglig i energimätaren, som används för debitering av energianvändning. I dagsläget finns normalt dock inte någon kommunikation mellan energimätare och reglersystem.I denna avhandling föreslås ett alternativt sätt att reglera fjärrvärmecentraler där trådlös sensorteknik i kombination med SOA (Service Oriented Architecture) används. Denna teknik tillåter olika enheter, t.ex. energimätare, cirkulationspump och reglerventil att kommunicera utan restriktioner, och på så sätt öka reglermöjligheterna.För att på ett smidigt sätt kunna testa nya reglerstrategier har en termodynamisk datormodell föreställande ett hus kopplat till ett fjärrvärmenät utvecklats och anpassats för verklighetstrogen simulering. Den termodynamiskamodellen har också kompletterats med modeller över strömförbrukning hos sensorplattformarna, vilket ger ett mycket bra verktyg för att prediktera batterilivslängden av sensorerna. Ett initialt fältförsök, där sensorplattformar har eftermonterats i befintliga fjärrvärmecentralsenheter (t.ex. energimätare och reglerventil) har också utförts. Denna specialutrustade fjärrvärmecentral har monterats i en villa för fortsatta tester.Resultaten av min forskning så här långt visar på att det finns en stor potential för ökat Delta T i fjärrvärmenäten. Möjligheterna till nya energitjänster visar sig också vara stor, speciellt när trådlös sensornätverksteknik kan förenkla och utgöra kostnadseffektiva lösningar.

Recent developments in sensor technology have resulted in the feasibility of deployingsensors on a human user in order to sense physiological properties such as body temperature,pulse and posture. This enables monitoring of a user’s health condition and stresslevels.Some professions, such as first responders, are often operating in dangerous situations,which causes increased stress levels. Since stress can lead to poor performance with injuryor even death as a result, it would be very beneficial to remotely monitor the personnelto find those with critical body status and evacuate them from the dangerous area. Thiswould increase work safety and also allow for more efficient training. Another categoryof potential users for remote monitoring of health conditions are patients and elderly,who could enjoy a higher quality of life with the increased safety of remote monitoring.As a result, it is highly motivated to find a technology which is applicable for monitoringboth a number of collaborative users, i.e., a team, and as well as a single user. Oneinteresting solution is to use a wireless sensor network (WSN). Another technology forremote monitoring is a personal area network (PAN). A PAN usually consists of consumerdevices, which enables it to communicate with existing infrastructure networks throughthe use of standardized protocols and technologies.This thesis investigates the feasibility of using a heterogeneous sensor network architecturefor the remote monitoring of a group of highly mobile users. The architecture is acombination of a WSN and PANs, which benefits from the mesh networking capabilitiesin WSN and the support for standardized protocols in PAN. The usage of the WSNincreases the network reliability and provides mobility and additional service (e.g. localization)to each user. The wearable PANs provide infrastructure network access pointsto sensor nodes, and hence support the mobility of the entire sensor network (by reusinguser’s mobile phone). Experimental results show that the proposed network architectureis a competitive solution for the targeted application, and I believe that this researchwork has the potential to drastically improve the life quality of a very large number ofusers, such as elderly and patients. / Nordic safety and security