Mitigating the Impact of Delay Uncertainty on the Performance of LQ Optimal Remote Control Systems

While ensuring efficient performance under nominal operating conditions, optimal controllers show sensitivity to perturbations and modeling inaccuracy. In networked control systems (NCSs) the situation aggravates owing to uncertain delay in the feedback loop and possibility of data loss. The paper investigates two methods of reducing the sensitivity to delay variations of linear-quadratic (LQ) optimal controllers in a networked environment. The first method employs a filtering mechanism to provide online updates of delay estimate in the optimal control structure. The second method uses additional information exchanged among the NCS components to increase the stability margin without downgrading the response speed. The methods are evaluated experimentally.