Estimator-Based Encoder-Decoder for Reducing Communications Demands in Event-Triggered Networked Control Systems

Abstract

Wireless networks are vital for implementing flexible Networked Controlled Systems (NCS) in distributed applications, yet they introduce sampling errors, delays, and packet losses that can compromise control performance. While emerging communication services such as Ultra-Reliable Low Latency Communications (URLLC) can mitigate these issues, they consume more shared network resources and may not be efficient if the NCS does not manage its transmissions. Event Triggered Control (ETC) addresses this challenge by determining when an update is needed, thereby specifying a Minimum Inter-Event Time (MIET) and Maximum Allowable Delay (MAD) to ensure a prescribed $\mathcal {L}_{2}$ norm condition or robust stability criterion. This letter proposes an Encoder-Decoder (E/D) architecture for NCS that requires that a control signal is transmitted over a wireless link. Instead of sending the original control signal whenever a trigger occurs, this method transmits an error signal produced by the comparison between the original control signal and a locally estimated signal. This estimated signal is assumed to be locally available at the transmitter and receiver to be used as the encoder and decoder, respectively. Assuming that the estimated signal is correlated to the original control signal, the transmitted error has a lower magnitude than the original transmitted signal. As a result, the NCS can guarantee its robust stability criterion while increasing the achievable MIET, thus reducing network resource usage. This approach is validated in a Cooperative Adaptive Cruise Control (CACC) setup, demonstrating an at least 20% improvement in MIET compared to conventional ETC, while maintaining $\mathcal {L}_{2}$ (string) stability and robust performance with fewer transmissions