Handling fault in ambient temperature measurements in a cooling system - A fault tolerant control approach

This paper proposes an active fault tolerant control (AFTC) scheme for detecting and correcting faulty measurements from the ambient temperature sensor that is utilized to calculate the optimal setpoints for a rooftop gas cooler unit operation. The faulty measurements are caused by improper placement of the ambient temperature sensor so that it is exposed to heat generated directly or indirectly by the sun. The AFTC is designed in a plug & play manner with no prior knowledge of the underlying system. The underlying system is identified by applying an online identification algorithm. To ensure the validity of the model several criteria is established. The resulting model is utilized in an observer based fault tolerant controller scheme including a bumpless implementation of the fault correction when a fault has been detected. The validity of the proposed AFTC scheme is investigated using both experimental data as well as simulation.