Co-Design of Real-Time Communication and Control in a Wireless Networked Control System

Abstract

Abstract : Networked control systems such as traffic control consist of multiple autonomously controlled objects (plant) interacting with each other. A controller in a networked control system receives real-time updates from the plant and the environment and sends controls to the plant. In designing a controller of such a system, there has been a separation of concerns between: (a) real-time communication protocol and the state of the plant and (b) the communication protocol and the control algorithm in the controller. In this work, we develop a cross-layer design of the real-time communication scheduling protocol on a shared wireless channel where the period of the updates change depending on the environment and a control algorithm that ensures safety. Specifically, we develop this design in the context of a traffic control testbed, where a set of cars travel autonomously along assigned paths as fast as possible with- out collision. We have developed a collision prediction algorithm based on bounding box estimates of neighbor position that can be used to change update periods of cars in collision range dynamically. Our real-time communication protocol is a modification of implicit-EDF that allows dynamic period changes while handling message losses. The controller implements a safety criterion that avoids collisions between cars.