O fenômeno de detonação que ocorre em motores de combustão interna é uma restrição de desempenho para baixas emissões de poluentes, altas solicitações de torque (as quais resultariam em mais potência entregue pelo motor), economia de combustível e também é uma fonte de ruídos desagradáveis ao condutor do veículo. No Brasil, tal fenômeno pode ter ainda uma utilidade benéfica se identificado de forma leal, tendo em vista que a detonação é mais fácil de ocorrer com gasolina do que com álcool. Assim, a ocorrência de detonação pode ser um auxílio no gerenciamento otimizado da injeção, ignição, bem como pode possibilitar a identificação do tipo de combustível. Para isso, técnicas de processamento de sinais podem ser utilizadas para caracterizar tal fenômeno. Este trabalho tem como foco a identificação (ocorrência) e caracterização (intensidade e duração) do sinal de detonação utilizando filtragem adaptativa e estimadores de potência, onde o desempenho individual e combinado destes algoritmos é avaliado. Inicialmente, um modelo do sinal de detonação é proposto e amostras do sinal real são obtidas e com isso, mostra-se que as técnicas propostas rendem eficientes caracterizadores do fenômeno. / The knock phenomenon that happens in internal combustion engines is a constraint against performance in terms of low pollution rates, higher torque requests (which would imply higher delivered power by the engine), mileage as well as it is an annoying source of noise to the user. In Brazil, such phenomenon may be useful if identified accurately, due to the fact that knock has a higher likelihood to happen with gasoline than ethanol. Thus, the occurrence of knock may be a support in an optimized management of fuel injection and sparking time, as well as it may provide means to identify the fuel being used. In order to achieve such goal, signal processing techniques may be used for characterization of such phenomenon. This work has the focus of identifying (occurrence) and characterize (intensity and duration) of knock signal using adaptive filtering and power estimators, where the individual and combined performance are assessed. To begin with, a knock signal model is proposed as well as samples of the real signal are taken, with that, it is shown that the proposed techniques offer efficient detectors of the phenomenon.

Este trabalho apresenta um estudo para a qualificação do sensor de detonação como elemento de realimentação para o sistema de controle eletrônico de motores de combustão interna. A metodologia proposta consiste no uso do sensor de detonação, previamente instalado pelo fabricante do motor com a finalidade de eliminar o indesejável efeito da combustão espontânea, para amostrar as vibrações mecânicas produzidas pelo motor em funcionamento. Tal vibração, resultado de massas em movimento e da oscilação natural do sistema excitado pela combustão, produz uma figura espectral na faixa de freqüências do som audível. O método proposto contempla ainda as variações espectrais das vibrações de um mesmo motor operando com diferentes misturas combustíveis. / This dissertation analyses the suitability of using the knock sensor as a feedback element for the electronic control of internal combustion engines. The proposed approach consists of using the knock sensor, originally installed by the engine maker in order to eliminate the spontaneous combustion effect, to sample the mechanical vibration produced by the engine. This vibration, which results from the moving parts and the natural oscillation of the system in combustion, produces an output in the range of audible sound. This research contemplates using the spectral variation of that sound to estimate information about an engine operating with different fuel blends.

Este trabalho apresenta um estudo para a qualificação do sensor de detonação como elemento de realimentação para o sistema de controle eletrônico de motores de combustão interna. A metodologia proposta consiste no uso do sensor de detonação, previamente instalado pelo fabricante do motor com a finalidade de eliminar o indesejável efeito da combustão espontânea, para amostrar as vibrações mecânicas produzidas pelo motor em funcionamento. Tal vibração, resultado de massas em movimento e da oscilação natural do sistema excitado pela combustão, produz uma figura espectral na faixa de freqüências do som audível. O método proposto contempla ainda as variações espectrais das vibrações de um mesmo motor operando com diferentes misturas combustíveis. / This dissertation analyses the suitability of using the knock sensor as a feedback element for the electronic control of internal combustion engines. The proposed approach consists of using the knock sensor, originally installed by the engine maker in order to eliminate the spontaneous combustion effect, to sample the mechanical vibration produced by the engine. This vibration, which results from the moving parts and the natural oscillation of the system in combustion, produces an output in the range of audible sound. This research contemplates using the spectral variation of that sound to estimate information about an engine operating with different fuel blends.

O fenômeno de detonação que ocorre em motores de combustão interna é uma restrição de desempenho para baixas emissões de poluentes, altas solicitações de torque (as quais resultariam em mais potência entregue pelo motor), economia de combustível e também é uma fonte de ruídos desagradáveis ao condutor do veículo. No Brasil, tal fenômeno pode ter ainda uma utilidade benéfica se identificado de forma leal, tendo em vista que a detonação é mais fácil de ocorrer com gasolina do que com álcool. Assim, a ocorrência de detonação pode ser um auxílio no gerenciamento otimizado da injeção, ignição, bem como pode possibilitar a identificação do tipo de combustível. Para isso, técnicas de processamento de sinais podem ser utilizadas para caracterizar tal fenômeno. Este trabalho tem como foco a identificação (ocorrência) e caracterização (intensidade e duração) do sinal de detonação utilizando filtragem adaptativa e estimadores de potência, onde o desempenho individual e combinado destes algoritmos é avaliado. Inicialmente, um modelo do sinal de detonação é proposto e amostras do sinal real são obtidas e com isso, mostra-se que as técnicas propostas rendem eficientes caracterizadores do fenômeno. / The knock phenomenon that happens in internal combustion engines is a constraint against performance in terms of low pollution rates, higher torque requests (which would imply higher delivered power by the engine), mileage as well as it is an annoying source of noise to the user. In Brazil, such phenomenon may be useful if identified accurately, due to the fact that knock has a higher likelihood to happen with gasoline than ethanol. Thus, the occurrence of knock may be a support in an optimized management of fuel injection and sparking time, as well as it may provide means to identify the fuel being used. In order to achieve such goal, signal processing techniques may be used for characterization of such phenomenon. This work has the focus of identifying (occurrence) and characterize (intensity and duration) of knock signal using adaptive filtering and power estimators, where the individual and combined performance are assessed. To begin with, a knock signal model is proposed as well as samples of the real signal are taken, with that, it is shown that the proposed techniques offer efficient detectors of the phenomenon.

In this thesis the possibility of using knock sensors for misfire detection in heavy duty diesel engines is investigated. This is of great interest due to many emission legislations getting stricter, especially in the US where robust misfire detection is mandatory for these types of engines. In order to capture the relevant vibra- tions on the engine a pre-study is made where the resonance frequencies in the cylinders are calculated which can be used for bandpass filtering the knock sen- sor signal. These bandpass filters are used to run tests where the engine is run with normal combustion and misfire on individual cylinders. The tests are made using a straight six cylinder diesel engine with a displacement of 12.7 litres. The test data is used to create threshold maps that can be used for misfire detection and for sensitivity analysis. Thereafter a detection algorithm is developed in MATLAB which involves integrating the knock sensor signal between two prede- fined crank angle degrees and then comparing it with a threshold value that can be interpolated from the threshold map. The test results show that this type of detection algorithm with these types of sensors is possible. There are also some areas of improvements presented that can make the misfire detection even more robust. / I denna rapport undersöks möjligheten att använda knackgivare för misständ- ningsdetektion i dieselmotorer för kommersiellt bruk. Bakgrunden är allt sträng- are lagstiftning i framförallt USA där det ställs krav på robust detektion av miss- tändningar i motorer för kommersiellt bruk. För att fånga de relevanta frekven- serna i cylindrarna som kan användas för detektion av misständning görs en för- studie där resonansfrekvenser beräknas och sedan används för att skapa band- passfilter. Filterna kan i sin tur användas för att filtrera knackgivarsignalerna. De framtagna bandpassfilterna används sedan för omfattande testning av miss- tändning i testcell. Motorn som används i testningen är en rak sexcylindrig die- selmotor med 12.7 liters slagvolym. Med den insamlade datan görs en känslig- hetsanalys samt gränsvärdesmappar som kan användas för misständsdetektion. Därefter utvecklas en detektionsalgoritm i MATLAB som går ut på att integrera knackgivarsignalen mellan två vevaxelvinklar och sedan jämföra med ett gräns- värde som kan interpoleras fram från gränsvärdesmappen. Testdatan visar att detektion med denna typ av system och med denna typ av algoritm är möjlig. I rapporten föreslås också ett antal områden som skulle kunna göra systemet ännu mer robust.

For diesel engines, valve timing is important and is related to power efficiency and exhaust gas after-treatment. During operation, the temperature of engine components can change and thus influencing the actual valve timing. With collected data from a Scania experimental engine, a method for valve closing time detection based on knock sensors is proposed in this project using a signal processing method. For algorithm design and result evaluation purposes, two references are used in this project. One is nominal valve timing, and the other is a valve timing reference based on rocker arm force signals. The developed method is tested through 4 evaluations: (1) 30% engine load with different engine speeds (600 to 2000rpm), (2) 1200rpm engine speed with different engine loads (0 to 100%), (3) 40% load 1200rpm at different oil temperature (around 50 to 80°C), and (4) 40% load dropped to motored condition. By comparing evaluation results and previously reported data, the following conclusions can be drawn: (a) The developed method has the ability to catch the changing of valve closing time in most test cases; (b) The developed method has a maximum combined error (between detected valve closing and rocker arm unloaded time) of - 4.7CAD on the intake side and -12.6CAD on the exhaust side among all cylinders; (c) Due to interference from vibration caused by valve events of other cylinders, the developed method has worse accuracy with larger than 50% load. Further work can focus on the detection of valve opening time and the improvement of accuracy by finding better sensor positions. / För dieselmotorer är ventiltidpunkten viktig och relaterad till energieffektivitet och avgasefterbehandling. Under drift kan temperaturen på motorkomponenterna förändras och därmed påverka ventilernas faktiska timing. Med insamlade data från en Scania experimentell motor föreslås i detta projekt en metod för detektering av ventilstängningstid baserad på knackgivare med hjälp av en signalbehandlingsmetod. För algoritmdesign och resultatutvärdering används två referenser i detta projekt. Den ena är nominell ventiltidpunkt och den andra är en ventiltidsreferens baserad på vipparmskraftssignaler. Den utvecklade metoden testas genom 4 utvärderingar: (1) 30% motorbelastning med olika motorvarvtal (600 till 2000r/min), (2) 1200r/min motorvarvtal vid olika motorbelastningar (0 till 100%), (3) 40% belastning 1200r/min vid olika oljetemperatur (runt 50 till 80 °C), och (4) 40% belastning till motordrivet tillstånd. Genom att jämföra utvärderingsresultat och tidigare rapporterade data kan följande slutsatser dras: (a) Den utvecklade metoden har förmågan att fånga ändring av ventilstängningstiden i de flesta testfall; (b) Den utvecklade metoden har ett maximalt kombinerat fel (mellan detekterad ventilstängning och vipparmslasttid) på -4,7CAD på inloppssidan och -12,6CAD på avgassidan bland alla cylindrar. (c) På grund av vibrationsstörningar orsakade av ventilhändelser hos andra cylindrar har den utvecklade metoden sämre noggrannhet med större än 50% last. Det fortsatta arbetet kan fokusera på detektering av ventilernas öppningstid, förbättring av noggrannheten genom att hitta bättre givarpositioner.

The door lock - a key function in every modern home, as well as a product which is today undergoing drastic change. The digital revolution has not left the door lock untouched, and there is today a wide variety of digital door locks utilizing technologies ranging from touch displays to fingerprint readers. The premises of the project was to try a different approach to the digital door lock and implement it schoolyard-style using a secret knock sequence, set by the user. The secret sequence would consist of two elements, both a rhythmical and a positional pattern. To unlock the door, the user would therefore need to simultaneously knock the correct rhythm and knock at the correct positions. To record and analyze the knock vibrations, piezo electric sensors connected to an Arduino Uno were used. To unlock the door, a small servo motor, two gears and a timing belt were used to turn the lock turning knob . Despite a short time frame and hardships due to the limitations caused by the coronavirus outbreak, a fully functional prototype which fulfilled both reliability and consistency was achieved. It could with good consistency recognize the test sequence, which was the intro rhythm to ”We Will Rock You” knocked in a square pattern. But even with flawless functionality, the conclusion would have been the same. The security of the system may be exceptional from a technical perspective, but it falls flat when the human factor is taken into account. The ability for a potential burglar to simply watch as one executes the secret knock is too much of a security hazard for the system to ever be considered as a competitor to other alternatives. The usage of the system is therefore better suited for applications where the thrill of using the product is more important than the actual security of it. / Dörrlåset - en grundläggande funktion i varje modernt hem, och samtidigt en produkt som idag genomgår drastisk förändring. Som resultat av den digitala revolutionen finns det idag en uppsjö av olika digitala dörrlås som utnyttjar allt från touchskärmar till fingeravtrycksläsare. Syftet med projektet var att testa en annorlunda tappning på det digitala dörrlåset, och förverkliga något många hade drömt om i barndomen - ett dörrlås aktiverat genom ett eget hemligt knackningsmönster. Det hemliga knackningsmönstret skulle då bestå av både ett rytmiskt och ett positionellt mönster. Därmed skulle den som ville öppna dörren behöva knacka både rätt rytm, och på rätt ställen på dörren. För att spela in och analysera vibrationerna från knackningarna användes piezoelektriska sensorer kopplade till en Arduino Uno. Mekanismen som styrde själva upplåsningen bestod av en liten servomotor, två kugghjul och en kuggrem som kopplade samman det hela. Trots en begränsad tidsram och motgångar orsakade av coronaviruset lyckades en fullt fungerande prototyp med hög pålitlighet färdigställas. Den kunde med hög tillförlitlighet känns igen testsekvensen, som var introrytmen till ”We Will Rock You” knackat i mönstret av en kvadrat. Men även med felfri prestanda hade slutsatsen varit densamma. Säkerheten för systemet må vara exeptionell ur ett rent tekniskt perspektiv, men den faller platt när den mänskliga faktorn tas med i beräkningen. Risken att en potentiell inbrottstjuv helt enkelt tittar på när någon knackar det hemliga mönstret är för stor för att systemet någonsin skulle kunna betraktas som en seriös konkurrent till andra digitala dörrlås. Produkten är därmed bäst lämpad för användningsområden där nöjet av att använda den är av högre prioritet än själva säkerheten.

The main objective of the presented thesis is to contribute to the development of diagnostic methods for piezoelectric sensor testing. The thesis describes the methods for piezoelectric sensors microcracks identification and diagnostics. The core of the thesis presents the development of a knock sensor prototype, design of suitable methods for the knock sensors diagnosis and evaluation of developed methods with focus on detection of microcracks in the sensor piezoceramic. The last part of the thesis deals with the influence of cracks and splits on the measured data from the piezoelectric transducer. The presented methods are focusing on impedance measurements and sensors frequency response measurements. Known properties of used piezoelectric material as an information source for measurement and diagnosis are provided. The main result of the work is the evaluation of the methods developed for the piezoelectric sensors self-diagnosis.