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Diagnosis on a Principle Environmental Control System

Diagnosis on a Principle Environmental Control System Johan Nilsson LiTH-ISY-EX-3067 Linköping Institute of Technology Abstract This thesis is carried out at the business unit Gripen of Saab Aerospace within the section for Thermal Analysis and System Simulation of General Systems. The work deals with automatic fault detection with focus on the Environmental Control System (ECS). The ECS main tasks are pressurization of cabin and cooling of avionics. Automatic fault detection is traditionally performed mainly by using limit checking of meas-ured signals and setpoint errors. An approach with a number of drawbacks such as difficulty in handling system transients and no systematic way for isolation of faults. Increasing demands on safety, reliability and economy has caught a growing attention for new diagnosis approaches. Model based diagnosis is found to be an approach with potential to increase per-formance and adding desired functionality. A principle model of the ECS is developed for design and test of a model based diagnosis sys-tem. Not only the ECS is modeled but also relevant faults, some faults well known from long experience of the system and some hypothetical faults for the exemplification of diagnosis methods. The benefits of a model based diagnosis approach is compared to diagnosis methods implemented in the ECS today.

Johan Nilsson


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