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<p>When flying a fighter aircraft such as the JAS 39 Gripen, the pilot is exposed to high g-loads. In order to prevent the draining of blood from the brain during this stress an anti-g protection system is used. The system consists of a pair of trousers, called the anti-g trousers, with inflatable bladders. The bladders are filled with air, pressing tightly on to the legs in order to prevent the blood from leaving the upper part of the body.</p><p>The purpose of this thesis is to detect if the pressure of the anti-g trousers is deviating from the desired value. This is done by developing a detection algorithm which gives two kinds of alarm. One is given during minor deviations using a CUSUM test, and one is given at grave deviations, based on different conditions including residual, derivative and time. The thresholds, in which between the pressure should lie in a faultless system, are calculated from the g-load value. The thresholds are based upon given static guidelines for the pressure tolerance area and are modified in order to adapt to the estimated dynamics of the system.</p><p>The values of the input signals, pressure and g-load, were taken from real flight sessions. The validation has been performed using both faultless and faulty flight sequences, with low false alarm rate and no missed detections. All together the detection system is considered to work well.</p>

The largest and most important fluid system in an aircraft is the fuel system. Obviously, future aircraft projects involve the design of fuel system to some degree. In this project design methodologies for aircraft fuel systems are studied, with the aim to shortening the system development time. This is done by means of illustrative examples of how optimization and the use of matrix methods, such as the morphological matrix, house of quality and the design structure matrix, have been developed and implemented at Saab Aerospace in the conceptual design of aircraft fuel systems. The methods introduce automation early in the development process and increase understanding of how top requirements regarding the aircraft level impact low-level engineering parameters such as pipe diameter, pump size, etc. The morphological matrix and the house of quality matrix are quantified, which opens up for use of design optimization and probabilistic design. The thesis also discusses a systematic approach when building a large simulation model of a fluid system where the objective is to minimize the development time by applying a strategy that enables parallel development and collaborative engineering, and also by building the model to the correct level of detail. By correct level of detail is meant the level that yields a simulation outcome that meets the stakeholders’ expectations. The experienced gained at Saab in building a simulation model, mainly from the Gripen fuel system, but also the accumulated experience from other system models, is condensed and fitted into an overall process.

In this final thesis two simulation models have been integrated. The simulation models are models of JAS 39 Gripen’s fuel system, software and hardware. The time consuming and costly work to develop software has made the department of fuel system to build two models in Xmath/Systembuild. The software model also simplifies the comprehension of how the software in the control computer of the fuel system works. Before the final thesis was done the software and hardware models were used separately and for different purposes. The software model wasused for verification and validation, and the hardware model for the system simulator. Because of the complex software it was a requirement to be able to simulate the software and hardware when they were connected, which would make it possible to study the different control signals generated by the software. To do that an interface between the user and the simulation model was created because it takes too much time to set all the inputs to the simulations model. The final thesis was assumed to deal only with an upgrading of the software model. The models have been connected and a user’s interface has been created with help of the program language Mathscript, which is a part of Xmath. A user’s guide is written so the user can simulate without experience of Xmath/Systembuild. With the connected models the user can now efficiently simulate and the result can be saved for later usage. The user can also simulate predefined missions from Saabs system simulator.

<p>In this final thesis two simulation models have been integrated. The simulation models are models of JAS 39 Gripen’s fuel system, software and hardware. The time consuming and costly work to develop software has made the department of fuel system to build two models in Xmath/Systembuild. The software model also simplifies the comprehension of how the software in the control computer of the fuel system works. Before the final thesis was done the software and hardware models were used separately and for different purposes. The software model wasused for verification and validation, and the hardware model for the system simulator. Because of the complex software it was a requirement to be able to simulate the software and hardware when they were connected, which would make it possible to study the different control signals generated by the software. To do that an interface between the user and the simulation model was created because it takes too much time to set all the inputs to the simulations model. The final thesis was assumed to deal only with an upgrading of the software model. The models have been connected and a user’s interface has been created with help of the program language Mathscript, which is a part of Xmath. A user’s guide is written so the user can simulate without experience of Xmath/Systembuild. With the connected models the user can now efficiently simulate and the result can be saved for later usage. The user can also simulate predefined missions from Saabs system simulator.</p>

When working with complex aircraft design it is necessary to be able test configurations easily. At Saab this is done in several ways. When looking at the weapons integration on the Gripen Aircraft, clearance analysis (called feasibility studies at Saab) are created to evaluate if new external stores can be mounted. This is done manually in CATIA by measuring and evaluating the result. To ease the work when performing these repetitive tasks, it is possible to take advantage of Knowledge Based Engineering, KBE. This thesis revolves around implementing KBE in the process. The approach is to create a configurator that can handle the different external stores and perform the required tasks. The end result is a configurator with a Graphical User Interface, GUI, in which the user gets help with the feasibility study and which requires light manual input from the user. The configurator performs the study and produces a Word report for the user to examine. The resulting time saving is around 75 to 80 percent from the original process. The conclusion is that the configurator can facilitate the feasibility studies at Saab by reducing the time and lower the threshold for the user. Even though the process is not fully automated, the configurator is judged to perform at a satisfying degree.

<p>Saab Aerosystems, a part of Saab AB, has the overall responsibility for the development of the fourth generation fighter aircraft JAS 39 Gripen. When planning a mission for one or more aircrafts, a computer program called Mission Support System is used. Some of the data from the planning is then transferred to the actual aircraft. Today there are some unwanted restrictions in the planning software. One of these restrictions is about the fact that a number of parameters that controls the output from a planned mission are not configurable runtime, i.e. a reinstallation at customers location is needed to change this. The main purpose of this thesis was to propose a new design and a new framework that solves the inflexibility described above. The design should also be validated by a test implementation. A number of different designs were proposed and four of these were selected to be candidates for being implemented. An important tool used when developing the designs was the theory of design patterns. To choose one of the four a ranking system, based on both measurable metrics and non-measurable experience, was used. One design was selected to be the best and after implementing of the design it was considered to be valid. Future work can consist of rewriting all modules in the software to use the new framework.</p>

<p>Abstract</p><p>SAAB has for a long time used user controlled pilot models in ARES. ARES is a simulation tool used in the desktop environment for simulations and calculations of the JAS 39 Gripen fighter and other aircraft. ARES stands for ”Aircraft Rigid body Engineering Simulation”. To work with these pilot models has been both time-consuming and inefficient. In this master thesis, new pilot models are developed, where parameters are automatically generated, this will result in that the user doesn’t have to put a lot of work into adjusting the gains for different manoeuvres. This is called gain scheduling.</p><p>To make this possible, simple models of the aircraft were created at different points in the envelope. These models were then used to calculate optimal controllers using LQ-control and pole placement techniques. These models and controllers were then implemented in Simulink. Simulink was then used to test the controllers before they were implemented in ARES.</p><p>Control in all modes except roll attitude and speed by throttle are based on LQ-control in pitch-, roll- and yaw-angular velocity. And through these angular velocities the other angles are controlled by simple controllers, who is generating a reference in angular velocity. The roll attitude controller is based on direct pole placement based upon desired damping and undamped natural frequency, and the speed controller is based upon a model of throttle positions in trimmed states.</p><p>The new pilot models are usable to control:</p><ul><li>Roll rate</li><li>Roll attitude</li><li>Pitch rate</li><li>Pitch attitude</li><li>Angle of attack</li><li>Load factor</li><li>Yaw attitude</li><li>Course angle</li><li>Climb angle</li><li>Mach number</li><li>Climb rate</li></ul><p>These controllers can be combined so that the aircraft can perform desired maneuvers.</p>

Traditional diagnosis has been performed with hardware redundancy and limit checking. The development of more powerful computers have made a new kind of diagnosis possible. Todays computing power allows models of the system to be run in real time and thus making model-based diagnosis possible. The objective with this thesis is to investigate the potential of model-based diagnosis, especially when combined with active diagnosis. The diagnosis system has been applied on a model of the JAS39 Gripen fuel pressurization system. With the sensors available today no satisfying diagnosis system can be built, however, by adding a couple of sensors and using active model-based diagnosis all faults can be detected and isolated into a group of at most three components. Since the diagnosis system in this thesis only had a model of the real system to be tested at, this thesis is not directly applicable on the real system. What can be used is the diagnosis approach and the residuals and decision structure developed here.