Design of Networked Control System with Discrete-Time State Predictor over WSN

Abstract

Abstract-We design a networked control system (NCS) with discrete-time state predictor where the communication between the controller output and the plant input takes place over a wireless sensor network (WSN). In order to measure time delays between the controller output and the plant input 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 discrete-time state predictor to compensate the time delays between the controller output and the plant input in real-time. For the real time experiment, we simulate the dynamic plant model, the 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 controller output and the plant input with WSN nodes. The experiment results show that the time delays between the controller output and the plant input are precisely measured in real time; the discrete-time state predictor appropriately compensates the time delays; and the stability is achieved in the closed-loop of the NCS.Index Terms-Delay, discrete-time state predictor, NCS, WSN. I. INTRODUCTIONNetwork control systems (NCSs) are spatially distributed systems in which sensors, actuators, and controllers exchange I/O information through a shared band-limited digital communication network. NCSs have been finding applications in a broad range of areas such as mobile sensor networks, remote surgery, haptics collaboration over the Internet, automated highway systems, and unmanned aerial vehicles [1], [2]. In particular, wireless networked control systems (WNCSs) are more promising because the deployment of wireless networks allows fully mobile operation, flexible installation and rapid deployment while reducing maintenance costs [3]. The key issue in NCSs is how to deal with the network delay and packet loss because it is well-known that even a small amount of time delay in the feedback loop of a control system can make the whole system oscillating or unstable [4].On the other hand, advances in pervasive computing, communication and sensing technologies are leading to the Manuscript received October 29, 2013; revised December 20, 2013 However,in [5], the time delay between sensors and controllers is not measured but just assumed to be a bounded value that is dependent on the sampling period of sensors.In this paper, we design an NCS with discrete-time state predictor where the communication between the controller output and the plant input takes place over WSNs. In order to measure time delays between the controller output and the plant input 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 as a parameter, we construct the discrete-time state predictor [6], [7] to compensate the time delays between the controller output and the plant input in real time. The discrete-time state predictor su...

Discrete-Time Sliding Mode Control for Uncertain Networked System Subject to Time Delay

“…Many control strategies that are robust with respect to parametric variations and nonlinearities of the plant exhibit great sensitivity when delays are present, losing all their features of robustness. Due to this and other problems and high control utilization, NCS has significantly attracted research communities with important results for numerous control methods such as fuzzy control, neural control, adaptive control, sliding mode control, optimal control techniques, and many more techniques [4][5][6][7][8][9][10][11].…”