Syftet med detta examensarbete är att utveckla en datorlaboration baserat på aktiv ljudreglering för kursen reglerteknik allmän kurs för maskin och farkostteknik vid Kungliga Tekniska Högskolan KTH. Arbetet ska innefatta en utveckling av en matematisk modell av rörsystemet som ska regleras med en lead-lag regulator. Rörsystemet vid Marcus Wallenberg Laboratoriet ska användas som modellsystem, och den matematiska modellen ska baseras på mätningar insamlade på detta system. Den matematiska modellen skapades med hjälp av ett s.k. identifieringsexperiment och identifieringen baserades på en viktad minsta kvadratanpassning av insamlade frekvensdata. Modellen anpassades till en överföringsfunktion som visade sig ha ett nollställe i komplexa högra halvplanet, vilket motsvarar en svår bandbreddsbegränsning för den aktiva ljuddämpningen. Orsaken till nollstället i högra halvplanet orsakas sannolikt av ljudreflektioner i rörsystemet. Begränsningen i bandbredden innebär att störningsundertryckning endast kan sker upp till en specifik frekvens. För rörsystemet vid MWL innebar en sådan begränsning att effekten av undertryckningen inte kommer att vara hörbar. Till denna anledning gjordes en modifiering i modellen i syfte att göra systemet användbart för en laborationsuppgift för reglering med en lead-lag regulator. Regleringen av den modifierade modellen gav ett hörbart resultat.

The Homogeneous Charge Compression Ignition (HCCI) is an engine which combines some of the characteristics of the Diesel and Otto engines. As a result an engine with a high efficiency and low emissions is constructed. Unfortunately, there is not a direct way to control its start of combustion (SOC). One way to phase the SOC is using valve timings. There are two main methods, the Overlap, which consists in trapping more or less residual gas, and the IVC method, which acts affecting the effective compression ratio. Iterative Feedback Tuning (IFT) is a control method that appeared in 1994, which has presented good performances in the tuning of PID and more complex controllers. The tuning is done by using data of closed loop experiments with the controller that is being tuned in the loop. Therefore, knowledge of the system and disturbances is not required. That is one of the principal advantages of this method. At the department of Machine Design at the Royal Institute of Technology (KTH) there is a single cylinder HCCI engine. It is based on a SCANIA truck engine and it includes an Active Valve Train System. In this equipment a control system based on non-linear compensation is used. Furthermore, a model of the real engine is available. In this project a procedure which allows the application of IFT in the HCCI has been developed. The method was tested, first, on a model and, secondly, in the test bed of the HCCI engine explained above. Controllers were tuned for three different operating points of the engine. The overlap method was used in two of them and the IVC method in the third one. However, more experience is required to determine how much improvement can be gained with the method. It was also noted that speed transients were very difficult to control due to long time delays.

An Homogenous Charge Compression Ignition engine is a hybrid between a Diesel and an Otto Engine. It has good fuel efficiency, close to a Diesel engine and also very low emissions of NOX and nearly no particulate soot. Other emissions are higher but can be after treated by a catalyst. The engine has not yet been fully developed so far and lacks among others a good automatic control of the combustion angle which should be held in a small window to achieve the best performance. The objective in this thesis is to achieve fast control that can hold the combustion angle window for changes in inlet pressure, loads and engine speeds. The challenges are that the system has a delay which limits the bandwidth, the dynamics change with different working conditions and a relatively large noise amplitude. Using combustion angle as reference, valve timings as control signal and other variables as engine speed, inlet pressure and load changes as disturbances, a closed loop control system can be defined. Two control methods using different kinds of variable valve timings and three controllers for each method were designed to cover most of the working conditions. These were connected by a hybrid automaton which handles all transitions and choice of controller. The result was a fast control with a 6-8 engine cycles risetime for reference changes and it can suppress inlet pressure and load disturbances well inside the combustion window. The noise showed to be white, that is using all frequencies. To achieve both a fast control and not magnify the noise a non-linear compensation link was designed that uses less gain and bandwidth for small errors. A problem with this kind of dynamic solution is engine speed ramps which needs fast reaction times which was impossible due to the delay. A proposed solution is to use mappings from non-delayed variables to do necessary adjustments of the control signal fast enough.

The overall objective with this thesis is to evaluate a method for designing nonlinear controllers in aircrafts with concern in robustness against modelling insecurities and also to minimize the design effort. The later objective is of great importance since there exists, in the industry, an ambition to automatize the design for as far extend as possible. The nonlinear method, State Dependent Riccati Equation (SDRE), used in this thesis is a nonlinear version of classic LQ design and both are evaluated and compared for a few flying conditions. Also another nonlinear control method, Two Timescale Separation (TSS), is tested. LQ and SDRE shows equal performance during both looping and more complicated maneuvers, such as high angle of attack wind-vector roll. Further it is possible to automatize the LQ design as well as it is possible for SDRE. Still SDRE is preferable since it will always be somewhat more accurate than LQ. A comparison with the nonlinear method Two Timescale Separation shows results in favor of LQ/SDRE mostly due to relatively slow dynamics and bad accuracy of TSS. A Monte Carlo simulation is made on LQ and SDRE showing that the model is robust against relatively large modelling error of 40%.

Målet med detta examensarbete var att erhålla kunskap om teknik och möjligheter hos trådlösa sensornät. Speciellt undersöktes hur temperaturförändringar kan detekteras med hjälp av ett trådlöst sensornät. Ett sådant nät sattes upp inomhus med enheter som kallas Tmote Sky och som tillverkas av Moteiv Corporation från USA. Enheterna har flera givare och kan kommunicera med varandra via radio. Härefter kommer de trådlösa sensorerna att kallas ”smolk” efter direktöversättning från engelskans ”mote”. Först undersöktes tre algoritmer som kunde lämpa sig för att upptäcka temperaturförändringar med hjälp av ett smolk utan att kommunicera med andra smolk: CUSUM-test, modellbaserad detektion och differensbildning. Differensbildningen föreföll lämpa sig bäst eftersom den visade minst fördröjning för att upptäcka temperaturförändringar. Därpå undersöktes tre utvidgningar till flera samverkande smolk: gemensamt medelvärde, gemensam median och omröstning. Omröstningen föreföll lämpa sig bäst då denna visade minst fördröjning för att upptäcka temperaturförändringar och för att den erfordrade mindre kommunikation mellan smolken. För att utvärdera algoritmerna i praktiken implementerades omröstningsalgoritmen på ett sensornätverk bestående av Tmote Sky smolk under operativsystemet TinyOS. Sensornätet kunde inte detektera temperaturförändringarna med de krav som ställdes. Orsaken till detta antas vara att smolken tvingades att samarbeta utan att veta storleken på de faktiska temperaturförändringarna. Slutsatsen är att trådlösa sensornät kan användas för temperaturövervakning, men detaljerad kännedom om det fysikaliska förloppet som ska detekteras är nödvändig.

The Transmission Control Protocol (TCP) is the dominating end-to-end protocol on the Internet today, carrying approximately 90% of the total traffic. TCP appear in numerous clones (e.g. Reno, Vegas, Sack etc.) all with different features and advantages but with maximal throughput as main objective (obeying fairness constraints). The performance of a protocol for varying network conditions and settings can effectively be evaluated using simulations. The free discrete network simulator NS-2 provides a dynamic simulation environment including several common TCP implementations. The software NS-2 is the result of an on-going effort of research and development and is hence not a finished product. The task in this masters’ thesis is to coordinate the (in NS-2) existing TCP implementations and develop, implement and thoroughly document a generic TCP protocol collecting existing protocols and where crucial algorithms easily can be manipulated for future experimental validation. The new implementation will be used for evaluating performance of existing and new TCP-versions.

Look ahead cruise control is a relatively new concept. It deals with the possibility of making use of recorded road slope data in combination with GPS, inorder to improve vehicle cruise control. This thesis explores the possibility ofestimating road slope as well as investigating the sensitivity of two look aheadcontrollers, with respect to errors in estimation of mass, wheel radius and roadslope. A filter using GPS and standard vehicle sensors is used for estimation ofroad slope. The filter is robust to losses in data since redundant information isavailable. Possible errors in estimation caused by the filter are identified. Two previously published look ahead controllers using different strategies tocontrol a heavy vehicle are investigated. A description of controller behaviourin perfect conditions is presented. Sensitivity analysis is performed identifyingerroneous control behaviour inflicted by errors in the used vehicle model androad slope. Further, effects on controllers caused by errors in road slope estimation estimation are detected. Conclusions about the two look ahead strategiesare drawn.

Similar to many technological developments, wireless sensor networks have emerged from military needs and found its way into civil applications. Today, wireless sensor networks has become a key technology for different types of ”smart environments”, and an intense research effort is currently underway to enable the application of wireless sensor networks for a wide rangeof industrial problems. Wireless networks are of particular importance whena large number of sensor nodes have to be deployed, and/or in hazardous situations. Localization is important when there is an uncertainty of the exact location of some fixed or mobile devices. One example has been in the supervision of humidity and temperature in forests and/or fields, where thousands of sensors are deployed by a plane, giving the operator little or no possibility to influence the precise location of each node. An effective localization algorithm can then use all the available information from the wireless sensor nodes to infer the position of the individual devices. Another application is the positioning of a mobile robot based on received signal strength from a set of radio beacons placed at known locations on the factory floor. This thesis work is carried out on the wireless automation testbed at the S3. Focusing on localization processes, we will first give an overview of the state of the art in this area. From the various techniques, one idea was found to have significant bearing for the development of a new algorithm. We present analysis and simulations of the algorithms, demonstrating improved accuracy compared to other schemes although the accuracy is probably not good enough for some high-end applications. A third aspect of the work concerns the feasibility of approaches based on received signal strength indication (RSSI). Multiple measurement series have been collected in the lab with the MoteIV wireless sensor node platform. The measurement campaign indicates significant fluctuations in the RSSI values due to interference and limited repeatability of experiments, which may limit the reliability of many localization schemes, especially in an indoor environment.

Recent advances in wireless communications and electronics has enabled the development of low-cost sensor networks. Wireless sensor networks can be used for various application areas (e.g., military, home, environment). Each application poses its own particular technical issues. One key problem that arises in many applications is how to organize the computation and communication in a sensor network to enable accurate estimation of the state of a dynamic system. As a starting point in this thesis, we demonstrate that packet loss and delays have a strong influence on the performance of optimal estimators. Thus, when we want to use a sensor network platform to collect and forward measurements to a data collector for estimation, it is critical to understand the loss performance of current hardware platforms and, possibly, to design MAC schemes that eliminate losses and minimize data collection latency. We investigate on the problem of packet loss, with practical experiments on a real wireless sensor network built up with Telos platform. The experiments in this thesis are made with single hop and multi-hop protocols in a star and linear network topology. To solve the problem of data delay and to avoid the collisions that lead to packet losses, we propose an overlay TDMA over CSMA. The underlying idea is to have a distributed protocol which is able to schedule the transmission of the nodes in order to have a data flow that converges from the furthest nodes toward the fusion center. To show the benefits of our protocol we simulate the behavior of a network in which nodes are randomly scheduled by the fusion center. Our protocol permits to obtain, in a distributed way, the optimal solution of such a network giving a strong improvement over a casual schedule.

Sensor nodes within networks are often grouped to participate to a common processing task. Cooperative diversity is a technique that exploits groups of sensor node randomly placed to cooperatively relay a common received signal toward a destination with the goal to combat severe attenuation or disconnections of the signal strength. In recent years, cooperative diversity has received attention for cellular radio systems and ad-hoc wireless networks. Such systems, however, are usually equipped with high processing capability. On the contrary, the nodes of a WSNs have limited memory and power capabilities and are usually deployed in unfriendly environment, where recharging and maintenance is not possible. In this thesis, we investigate the problem of power control of nodes performing cooperative diversity. Specifically, we study the problem of minimizing the power consumption of the sensor nodes transmitters while guaranteeing a minimum quality of the signal at the data collector. After studying the most relevant algorithms existent in literature for had-hoc networks, we propose an sub-optimal algorithm suitable for nodes equipped with low computational capabilities. We implement a WSNs performing cooperative diversity with Omnet++, where the network simulator includes the sub-optimal solution. Numerical results show that for the set of parameters of practical interest, our solution exhibits good performance for low correlated channel links, while the increase of relaying nodes ensures a decreasing of total power consumption.