Design of networked control system using RTT measurement over WSN

We design a networked control system (NCS) where the communication between sensors and controllers takes place over a wireless sensor network (WSN). In order to measure time delays between sensors and controllers in real time, we design an algorithm to measure round trip time (RTT) between WSN nodes, and implement it into TinyOS of WSN. By using the measured time delays, we construct the Smith predictor to compensate the time delays between sensors and controllers in real-time. For the real time experiment, we simulate the dynamic plant model, controller, and WSN interface using Real-Time Windows Target provided in MATLAB. The WSN interface in the Simulink model consists of serial ports, which connect the plant output and controller with WSN nodes. The experiment results show that the time delays between sensors and controllers are precisely measured in real time; the Smith predictor appropriately compensates the time delays; and the stability of the designed NCS is achieved.