Loop‐Shaping Feedback and Feedforward Control for Networked Systems With Saturation and Delay

The paper proposes a new robust networked controller, for example suitable for packet data transfer control in wireless sensor networks with uncertain delays. The method adjusts a linear H 2 loop‐shaping design towards consistency with a long delay and a saturation in the feedback loop, where the saturation results because of the one‐directional packet flow. Feedforward from a measurable disturbance is integrated in the design. By formally extending recently derived sensitivity function constraints to include feedforward, a subset of the stability region is pre‐computed using the stability inequality of the Popov criterion. A robustly stable controller is then selected in the stability region. The new controller design method is applied to internet data flow control supporting 5G wireless connectivity. The results indicate a possible enhancement of the robustness against feedback delay uncertainty with a factor of 3‐4. Such robustness should be beneficial for example for packet data relying with variable routing over ad hoc wireless sensor networks.