On line optimization of an arbitrary process by a personal microcomputer system: Application in algae ponds

Application of conventional optimal control algorithms requires an a priori knowledge of the mathematical model of the system. However, real systems are seldom simple enough to permit accurate modelling. The purpose of the present study was to investigate possible strategies for on-line optimization of processes which are non linear, time dependent and have no known mathematical model to accurately describe them. It was believed that the dramatic price decrease of microcomputing power can make such an approach feasible in practical applications such as biotechnological production of biomass. The proposed approach is based on on-line search for optimum operating conditions by a microcomputer system using a modified Simplex algorithm to which several features were added to permit operation in real time. They include boundary limits for variables, noise smoothing and stepwise variations of variables. The on-line Simplex algorithm is simply the upper level of a three level hierarchical program which also includes on-off and PID control (lower level) and an intermediate level of parameter estimation. Experiments were carried out using a microcomputer system which is based on a low cost personal microcomputer, a novel interface for sensors and control devices and battery backup to ensure uninterrupted operation. The method was applied for on-line optimization of biomass production in an algal pond (Spirulina Platensis). The preliminary results seem to support the conjecture that the proposed approach could be useful in optimizing various industrial processes.