A thesis on the on-line calculation of optimal control strategies

Theoretical solutions to a time optimal problem for a charging process using two heat sources and a minimal system model have been obtained. These solutions have included different heat source ratios and have been applied to a system with simple external heat exchanger and also to a perfectly mixed system. The optimal solutions have been obtained by the application of Pontryagin's maximum principle. It is shown that in using minimal system models the charging policy may show time reductions of up to 10.2 per cent over the best constant charging rate policy. A dual computer controller/process-Simula tor system has been developed, enabling comprehensive simulation studies, under wide ranging system conditions, to be made. The controller was developed in such a manner as to enable it to be transferred to the rig without further modification. The controller used a 'search' and 'control' strategy in order to operate the process at a maximum Hamiltonian function value. However, because of the step-wise nature of the approximation to the charge rate, which was used to implement the 'control' and 'search' policy, the overall control must be regarded as sub-optimal. Results obtained from an experimental rig showed that although all implementations of the control strategy were an improvement over the best constant charge rate policy, the 'optimal' results were not reproducable owing to difficulties in achieving tight control over the performance of the long tubular external heat exchanger. Results from the simulations and practical implementations are discussed and comparisons with other work have been made. Suggestions for further studies are also given