Feedback Control Goes Wireless: Guaranteed Stability over Low-power Multi-hop Networks

TL;DR

This paper demonstrates that stable feedback control over low-power wireless multi-hop networks with update intervals of 20-50 milliseconds is feasible, enabling fast and reliable control in cyber-physical systems.

Contribution

It introduces a wireless embedded system and control design that guarantees stability over multi-hop networks at much faster update rates than previously achieved.

Findings

Achieved stable feedback control at 20-50 ms intervals

Validated system on a testbed with 20 wireless nodes

Demonstrated control of multiple cart-pole systems

Abstract

Closing feedback loops fast and over long distances is key to emerging applications; for example, robot motion control and swarm coordination require update intervals of tens of milliseconds. Low-power wireless technology is preferred for its low cost, small form factor, and flexibility, especially if the devices support multi-hop communication. So far, however, feedback control over wireless multi-hop networks has only been shown for update intervals on the order of seconds. This paper presents a wireless embedded system that tames imperfections impairing control performance (e.g., jitter and message loss), and a control design that exploits the essential properties of this system to provably guarantee closed-loop stability for physical processes with linear time-invariant dynamics. Using experiments on a cyber-physical testbed with 20 wireless nodes and multiple cart-pole systems, we are the first to demonstrate and evaluate feedback control and coordination over wireless multi-hop networks for update intervals of 20 to 50 milliseconds.