Networked LQG control over unreliable channels

In this article, the linear quadratic Gaussian (LQG) optimal control problem for networked control systems when data is transmitted through a transmission control protocol (TCP)-like network and both measurement and control packets are subject to random packet dropouts, is addressed for two cases. In the first case, it is assumed that the control acknowledgment packets in TCP-like protocols are always available, that is, they always reach the filter-controller unit on time and without fail, and we propose how to design a linear optimal 'hold-input' control law for this case. In the second problem, we assume the acknowledgement packets may go missing with a known probability. This case is known to be difficult and the optimal control law would be nonlinear. Hence, we derive a suboptimal linear estimation-control law instead. Simulation results are presented to demonstrate the effectiveness of the proposed approaches. Copyright (C) 2011 John Wiley & Sons, Ltd.