A practical implementation of distributed system control over an asynchronous Ethernet network using time stamped data

With the increasing use of Ethernet for real-time control of distributed dynamic systems, and inexpensive processing power at the sensor and actuator nodes, there is a growing interest in the process control community to move towards “model based” distributed control. Prior work shows that the lack of precise time synchronization is a critical hindrance to reliable model generation or estimation in networked distributed systems. This paper explores the use of IEEE 1588 Precision Time Protocol (PTP) to improve the fidelity of model estimates and the reliability of control messaging. The implemented controller is tested on a control system testbed augmented with PTP based time stamping and shows substantially improved tracking performance when compared to a similar controller without precise time knowledge. This improvement was achieved by building a propagated estimation of the master system to provide a reference tracking signal for the slave system, a technique that would not be feasible without time synchronization.