Flexible Time-Triggered Sampling in Smart Sensor-Based Wireless Control Systems

TL;DR

This paper introduces a flexible, feedback-controlled time-triggered sampling scheme for wireless control systems, enabling dynamic adjustment of sensor sampling rates to maintain quality of control amid unpredictable network traffic variations.

Contribution

It proposes a novel adaptive sampling method using smart sensors and feedback control to improve QoC in wireless control systems under variable network loads.

Findings

Enhanced QoC compared to fixed sampling methods.

Effective handling of dynamic network traffic loads.

Maintains desired deadline miss ratio across varying conditions.

Abstract

Wireless control systems (WCSs) often have to operate in dynamic environments where the network traffic load may vary unpredictably over time. The sampling in sensors is conventionally time triggered with fixed periods. In this context, only worse-than-possible quality of control (QoC) can be achieved when the network is underloaded, while overloaded conditions may significantly degrade the QoC, even causing system instability. This is particularly true when the bandwidth of the wireless network is limited and shared by multiple control loops. To address these problems, a flexible time-triggered sampling scheme is presented in this work. Smart sensors are used to facilitate dynamic adjustment of sampling periods, which enhances the flexibility and resource efficiency of the system based on time-triggered sampling. Feedback control technology is exploited for adapting sampling periods in a periodic manner. The deadline miss ratio in each control loop is maintained at/around a desired level, regardless of workload variations. Simulation results show that the proposed sampling scheme is able to deal with dynamic and unpredictable variations in network traffic load. Compared to conventional time-triggered sampling, it leads to much better QoC in WCSs operating in dynamic environments.