Multi-rate model predictive control for energy efficiency in wireless networked control systems

Abstract

Wireless communication technology has become a fundamental part of the process industries, where the use of wireless transmitters for monitoring and control is a reality. The architecture of Wireless Networked Control Systems (WNCSs) has advantages over point-to-point and wired networks architectures. However, the evolution of this technology has introduced new challenges to the implementation of the closed-loop control with a wireless instrument. A critical factor related to implementation of WNCSs is the energy source of these transmitters, which have limited lifetime dependent on the amount of access and data transmitted. This chapter presents the study and development of a multi-rate model predictive control (MPC) as an alternative to improve energy efficiency in industrial applications of WNCSs. The proposed strategy uses less process variables data as it does not requires frequently updates of the process variables transmitted by the wireless instruments. The MPC uses the internal submodel of the process variables to estimate the process signals when they are not transmitted. Thus, a decrease in the frequency of data transmission on the wireless network can be obtained and consequently a reduction of energy consumption of wireless devices. Simulation results of a multivariable WNCS of coupled tanks proves that the multi-rate MPC provides energy economy as it is effective in saving the energy expenditure of the wireless transmitter's battery. An energy efficiency analysis of the WNCS is presented by studying the operating limits of the multi-rate MPC considering the compromise relationship between the sampling period of the wireless devices and the control performance of the WNCS.