Adaptive LQR controller for Networked Control Systems subjected to random communication delays

Control loops integrated with communication channels for information exchange among system components are called Networked Control Systems (NCSs). Introduction of communication channels induce time-varying communication delays and make the controller design complex. In this paper, an adaptive regulator (AR) that varies its gain depending on the delays in the channel is proposed. The construction of AR is based on the LQR approach. Computation of gains in AR is simplified using the first order approximation that reduces computation delays significantly thereby making the adaptation rule more suitable for higher order systems. The results are illustrated using studies conducted on Modbus over TCP/IP (Transmission Control Protocol/Internet Protocol) communication protocol and a simulation example.