Construction pruning for twice optimal control of pure integrating process with long time delay

Developing a control strategy with a strong robustness for system with long time delay is a hot problem, especially a fast settling during set point response and strong rejection for load disturbance. An optimal control method, namely, Twice Optimal Control(TOC) achieved strong robust control for this system through constructing an infinite-dimensional state observer and a proportion-integration(PI) controller. However, when system response is sped up, the transient process presented intense oscillation due to system´s insufficient damping in middle-low frequency. To solve this problem, this paper introduces a construction pruning factor to TOC system. Notice that system damping is increased, response speed will be slowed down. Then the contraction operator and the open-loop gain of TOC system are proposed to be readjusted to make sure desired response speed and disturbance rejection. In order to demonstrate the performance of proposed method, comparative simulations are carried out and analyzed through system with an integrator plus time delay(IPTD).