Re-Optimal Design for Twice-optimal Control of an Unstable Second Order Process with Time Delay

Regarding the robustness and dynamic response issue of unstable second order process with time delay (USOPTD), a new re-optimized design strategy based on twice-optimal control (TOC) theory is proposed. First, on the basis of the TOC, the system infinite dimensional controller and state observer are constructed, which is verified to eliminate the impact of time delay on the system, so it has strong robustness. Second, a local feedback K
_F
value is increased to eliminate the oscillation during the transition process of TOC system. Then, in order to improve the rapidity of the system, a square-root amplifier (SRA) has been applied to the re-optimized designing system. Finally, simulation-based comparisons of this method and the other regular control approaches have been made. The results show that the new system has not only a fast and more smoothly tracking responses but also strong robustness to load disturbance and parameter perturbation. Moreover, the new method is simple, practical and easy to tune parameters, thus providing guidelines for industrial applications of similar systems.