Identification methods for multiple cell systems.

A tracer gas technique for determining volumes and air flow rates in multi-cell systems with a single tracer gas is considered. Tracer gas is injected in all cells simultaneously according to a cetain pattern and the resulting tracer gas concentrations are recorded. We show how the volumes and flow rates can be identified from the measurements using the quadratic programming method. A characteristic of this method is that the unknown model parameters, i.e. the volumes and flows, can be determined subjected to given constraints. Accordingly we can utilize all known information about the flow system and make sure that a found solution is physically compatible with a flow system. Different formulations of the mass balance relations are discussed and a new method to overcome the difficulties to calculate the derivatives of the tracer gas concentrations is proposed. The properties of the different formulations such as the sensitivity to noise and the significance of the sample period are exemplified by identifications on a simulated three cell system.