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<p>Throughout recent years, legislations concerning emission levels for vehicles have become more restrictive and will be even more restrictive in the future. In the recent European environmental standards, EURO 4 (2006) and EURO 5 (2008), further requirements have been added on top of low emission demands. All heavy duty trucks have to be equipped with an OBD-system. Scania CV AB has today an existing OBD-system that consists of several tests. Typically, a test is designed to check if a signal is inside specified limits or thresholds. To improve the system, Scania CV AB and Vehicular Systems at Linköping University have developed a method to design diagnosis systems in an automatic way, implemented in a toolbox called DSAME.</p><p>In this thesis, an automatic designed OBD-system has been created with DSAME and the corresponding parts in a manually designed OBD-system have been identified. The two systems have been compared. The result shows that both systems are equally at detecting faults but the automatic designed OBD-system is a lot better to isolate the faults than the existing OBD-system.</p>

Diagnosis and Supervision of technical systems is used to detect  faults when they occur. To make a diagnosis, tests based on residuals can be used. Residuals are used to compare observations of  the system with a model of the system, to detect inconsistencies. There are often many different types of faults which affects the  state of the system. These states are modeled as fault modes. The  difference between fault modes are the presence of faults in the  model. For each fault mode a different set of model equations is  used to describe the behaviour of the real system. When doing fault  diagnosis in real time it is good, and sometimes vital, to be able to change fault mode of the model, when a fault suddenly occurs in the real system. If multiple faults can occur the number of  combinations of faults is often so big, even for relatively small  systems, that residuals for all fault modes can not be prepared. To  handle this problem, the residuals are to be generated when they are  needed. The main task in this thesis has been to investigate how residuals  can be automatically generated, given a fault mode with a  corresponding model. An algorithm has been developed and to verify  the algorithm a model of a satellite power system, called  ADAPT-Lite, has been used. The algorithm has been made in two versions. One is focusing on numerical calculations and the other is  allowing algebraical calculations. A numerical algorithm is preferred in an automatized process because  of generally shorter calculation times and the possibility to apply it to systems which can not be solved algebraically but the  algebraical algorithm gives slightly more accurate results in some  cases. / Diagnos och övervakning av tekniska system används för att upptäcka fel när de inträffar. För att ställa en diagnos kan tester baserade på residualer användas. Residualer används för att jämföra observationer av ett system med en model av system för att upptäcka inkonsistens. Det finns ofta många typer av fel som påverkar ett systems tillstånd.Dessa tillstånd modelleras med olika felmoder. För varje felmod används olika uppsättningar av modellekvationer för att beskriva systemets beteende. När diagnoser ska ställas i realtid är det ofta bra och ibland avgörande att kunna byta felmod när ett fel plötsligt inträffar i systemet. Om multipelfel kan inträffa blir antalet kombinationer av fel ofta så stort att residualekvationerna för alla felmoder inte kan förberedas. Detta gäller även för relativt små system. För att hantera problemet bör residualerna kunna genereras vid den tidpunkt då de behövs. Examensarbetets huvuduppgift handlar om att undersöka hur residualerna kan genereras automatiskt, givet en felmod och en modell. En algoritm har utvecklats och verifierats med en model av ett kraftsystem för en satellit, kallad ADAPT-Lite. Algoritmen har gjorts i två versioner. Den ena tillåts göra algebraiska beräkningar men den andra, i så storutsträckning som möjligt, tillåts endast göra numeriska beräkningar. En numerisk algoritm föredras i en automatiserad process p.g.a. generellt sett kortare beräkningstid och dess egenskap att kunna lösa vissa problem som inte kan lösas algebraiskt. Den algebraiska algoritmen har dock visats sig ge aningen noggrannare resultat i många fall.

Throughout recent years, legislations concerning emission levels for vehicles have become more restrictive and will be even more restrictive in the future. In the recent European environmental standards, EURO 4 (2006) and EURO 5 (2008), further requirements have been added on top of low emission demands. All heavy duty trucks have to be equipped with an OBD-system. Scania CV AB has today an existing OBD-system that consists of several tests. Typically, a test is designed to check if a signal is inside specified limits or thresholds. To improve the system, Scania CV AB and Vehicular Systems at Linköping University have developed a method to design diagnosis systems in an automatic way, implemented in a toolbox called DSAME. In this thesis, an automatic designed OBD-system has been created with DSAME and the corresponding parts in a manually designed OBD-system have been identified. The two systems have been compared. The result shows that both systems are equally at detecting faults but the automatic designed OBD-system is a lot better to isolate the faults than the existing OBD-system.

<p>Stronger environmental awareness as well as actual and future legislations increase</p><p>the demands on diagnosis and supervision of any vehicle with a combustion engine.</p><p>Particularly this concerns heavy duty trucks, where it is common with long driving</p><p>distances and large engines. Model based diagnosis is an often used method in</p><p>these applications, since it does not require any hardware redundancy.</p><p>Undesired changes in the intake manifold pressure can cause increased emissions.</p><p>In this thesis a diagnosis system for supervision of the intake manifold</p><p>pressure is constructed and evaluated. The diagnosis system is based on a Mean</p><p>Value Engine Model (MVEM) of the intake manifold pressure in a diesel engine</p><p>with Exhaust Gas Recirculation (EGR) and Variable Geometry Turbine (VGT).</p><p>The observer-based residual generator is a comparison between the measured intake</p><p>manifold pressure and the observer based estimation of this pressure. The</p><p>generated residual is then post treated in the CUSUM algorithm based diagnosis</p><p>test.</p><p>When constructing the diagnosis system, robustness is an important aspect. To</p><p>achieve a robust system design, four different observer approaches are evaluated.</p><p>The four approaches are extended Kalman filter, high-gain, sliding mode and an</p><p>adaption of the open model. The conclusion of this evaluation is that a sliding</p><p>mode approach is the best alternative to get a robust diagnosis system in this</p><p>application. The CUSUM algorithm in the diagnosis test improves the properties</p><p>of the diagnosis system further.</p>

<p>Technical systems of today are often complex and integrated. If a fault occurs, the consequences can be disastrous both for the system itself and its surroundings. To maintain the operation and the security it is necessary to have a surveillance system which can detect a fault in an early stage.</p><p>In this thesis two structural methods for fault isolation analysis are discussed. The result from the studied algorithms shows what fault isolation properties a diagnostic model is expected to have. If the isolability is not good enough, it also gives information on where further modelling needs to be done. </p><p>To base a comparison of the two structural analysis algorithms on, four criteria are defined concerning for example realizability of residuals and time complexity. One interesting part of the methods is how dynamic models are handled. It is shown how differential constraints can end up in differential cycles which implies calculatory problems and what effects structural differentiation has on a system. </p><p>The algorithms have been tested on an application from the research training network DAMADICS. The result shows how different types of input models in this case give the same result.</p>

<p>New emission legislations introduced in the European Union and the U.S. have made truck manufacturers face stricter requirements for low emissions and on-board diagnostic systems. The on-board diagnostic system typically consists of several tests that are run when the truck is driving. One way to construct such tests is to use so called consistency relations. A consistency relation is a relation with known variables that in the fault free case always holds. Calculation of a consistency relation typically involves eliminating unknown variables from a set of equations.</p><p>To eliminate variables from a differential polynomial system, methods from differential algebra can be used. In this thesis, the purely algebraic Gröbner basis algorithm and the differential Rosenfeld-Gröbner algorithm implemented in the Maple package Diffalg have been compared and evaluated. The conclusion drawn is that there are no significant differences between the methods. However, since using Gröbner basis requires differentiations to be made in advance, the recommendation is to use the Rosenfeld-Gröbner algorithm.</p><p>Further, attempts to calculate consistency relations using the Rosenfeld-Gröbner algorithm have been made to a real application, a model of a Scania diesel engine. These attempts did not yield any successful results. It was only possible to calculate one consistency relation. This can be explained by the high complexity of the model.</p>

<p>As machines are increasingly used to fulfill even more needs of mankind, the dependence upon those machines increase. To prevent catastrophic failure and to facilitate maintenance a diagnostic system can be used. A diagnostic system supervises the system and can alarm the operator when a fault has occurred, and possibly determine what the cause may be. One architecture of a diagnostic system is a number of tests run by an on-board computer checking certain combinations of sensor values and control signals chosen in advance. To design these tests is a difficult task, which leads to the desire to automate the test construction. A part of this task can be performed using structural methods.</p><p>In this thesis model based diagnosis is considered. This means that a formal mathematical model is used. The models typically consist of a number of equations describing the behavior of the system. In structural methods it is only considered if a variable exists in an equation or not. The goal of this master thesis project has been to apply structural methods to RODON models. RODON is a software diagnostics tool brought to market by Sörman Information & Media, which can perform various diagnostic-related tasks based on a single model. This model is defined in an object oriented fashion using a Modelica-like language called Rodelica. A prototype implementation of a structural algorithm plug-in has been developed and integrated into RODON. An additional part of the project has been to investigate further possible uses of structural algorithms in RODON, apart from diagnostic test construction. This has been performed as a series of interviews with Sörman and university employees.</p><p>The work performed in this thesis has shown that it is possible to apply structural methods to RODON models. It has also shown that even a prototype implementation can handle quite large systems. Some problems have been found as well, most notably in extracting a structural model from a RODON model. A consequence is that the developed structural plug-in only works for a subset of RODON models. It might be possible to deal with these problems if more time would be spent on the task. Finally, the interview survey revealed other possible uses of structural methods in RODON, including optimal sensor placement analysis and isolability and detectability analysis.</p>

<p>Diagnosis is the task of finding faults or malfunctioning components in a technical system, e.g a car. When doing diagnosis on cars with combustion engines, a computer program can be used. The computer program, also called diagnosis system, needs information about the car. This information could be data sheets of all the electronic components in the car. It could also be a description of how the engine behaves in a nominal and a non-nominal case. This information is contained in a model of the engine. RODON, a diagnostic tool developed by Sörman Information and Media AB, uses models of systems for conflict detection diagnosis. RODON needs fault models of the components to do diagnosis. The diagnosis system is then used in workshops, factories, or other places where cars need to be surveyed.</p><p>In this thesis, a Simulink model of the nominal behaviour of a combustion engine is given. The problem is how to make use of the model as well as the diagnostic tool RODON for combustion engine diagnosis. To solve this, the Simulink model is translated into a RODON model. Translating a Simulink model into a RODON model requires a new library in RODON. The library developed in this thesis is called AdvancedBlocks library.</p><p>The Simulink model describes the nominal behaviour of a combustion engine but for diagnosis with RODON, fault models are needed as well. Several types of faults that can occur in an engine have been studied and fault models have been implemented in RODON. The conclusion is that diagnosis in RODON with a translated engine model is possible.</p>

In unmanned aerial systems an autopilot controls the vehicle without human interference. Modern autopilots use an inertial navigation system, GPS, magnetometers and barometers to estimate the orientation, position, and velocity of the aircraft. In order to make correct decisions the autopilot must rely on correct information from the sensors. Fault diagnosis can be used to detect possible faults in the technical system when they occur. One way to perform fault diagnosis is model based diagnosis, where observations of the system are compared with a mathematical model of the system. Model based diagnosis is a common technique in many technical applications since it does not require any additional hardware. Another way to perform fault diagnosis is hardware diagnosis, which can be performed if there exists hardware redundancy, i.e. a set of identical sensors measuring the same quantity in the system. The main contribution of this master thesis is a model based diagnosis system for a fixed wing UAV autopilot. The diagnosis system can detect faults in all sensors on the autopilot and isolate faults in vital sensors as the GPS, magnetometer, and barometers. This thesis also provides a hardware diagnosis system based on the redundancy obtained with three autopilots on a single airframe. The use of several autopilots introduces hardware redundancy in the system, since every autopilot has its own set of sensors. The hardware diagnosis system handles faults in the sensors and actuators on the autopilots with full isolability, but demands additional hardware in the UAV.