Control over Communications Networks

Dawn Tilbury
University of Michigan, Mechanical Engineering

Networked control systems are becoming increasingly popular in industrial applications.  The network hardware costs are going down and the available bandwidth is increasing at a rapid pace.  A networked control architecture allows for more complex control strategies, on-line adaptation, and sophisticated diagnostics than are possible with traditional point-to-point implementations. Reconfiguration of the system and addition of new sensing capabilities is also considerably easier with a networked control strategy, Although it was originally designed as a communication network, Ethernet is rapidly emerging as the control network of choice due to its low cost and high bandwidth.

In this talk, we will review some of our work on control over Ethernet.  We start with some basics of networked control systems, and give some results on the experimentally-observed delays in wired and wireless Ethernet networks.  Since the delays in an Ethernet network are most significant when the traffic load is highest, we have developed several control strategies that reduce the amount of communication required in a control system while maintaining closed-loop performance.  We will summarize these methods and present theoretical, simulation, and experimental results for the performance.  To conclude, we will describe the testbeds we have developed for networked control research and outline some future work in the area.