SPECIFIC OPTIMAL-CONTROL OF AN ALUMINUM CASTING FURNACE

A general structure of the specific optimal control has been previousl y formulated and used to solve the fuel optimal problem of an aluminum casting furnace. Proportional, integral, and derivative (P, I, D) clo sed-loop control were applied to a 10-order nonlinear model of the fur nace. This paper analyzes the resulting control actions and the dynami c response to a step change in the target temperature of the liquid me tal. it is shown that P and PD schemes ave stable but bring about a st eady-state error; whereas PI and PID schemes cause no steady-state err or but involve considerable oscillations in the transient response and longer settling times. In view of the system's high thermal inertia a nd the need to impose limits on fuel flow rate, it is found that a PD scheme is the most appropriate due to the absence of over shoot and a short settling time. The method is also applied to another optimizatio n criteria, the minimization of temperature oscillations. This shows t he applicability of the scheme to practical industrial problems.