Climate control of a bulk storage room for foodstuffs

A storage room contains a bulk of agricultural products, such as potatoes, onions, fruits, etcetera. The products produce heat due to respiration, see for example [?, ?]. A ventilator blows cooled air around to keep the products at a steady temperature and prevent spoilage. The aim is to design a control law such that the product temperature is kept at a constant, desired level. The system contains nonlinear coupled partial differential equations (pde’s). The assumptions that the input switches between discrete values, and that the system states have either very slow or very fast dynamics, simplify the equations. Transfer functions of the linear subsystems give us an idea of the time scales of the states, and with their approximations we can convert linear pde’s into ordinary differential equations (ode’s). The control problem for the simplified system consists of the determination of the switching moment, and is relatively easily solved.