Design and implementation of networked predictive control systems based on round trip time delay measurement

There are two random network transmission delays in networked control systems: forward and backward channel delays, which degrade the control performance significantly and even make the system unstable. In this paper, a predictive control method is presented to compensate the random delays. By using Diophantine equation, future control sequences for every possible time delay are generated, which are transmitted to the plant side in a single packet. The prediction is not based on individual forward and backward delays which are difficult to measure separately in a practical system but the round trip time (RTT) delay which is the sum of forward and backward delays, and is easy to measure. An active plant side and an event-driven controller are also introduced to achieve the aim. To illustrate the control performance improvement of the proposed control scheme, the results of off-line and real-time simulations and experiments for a practical servo control system are presented.