Networked Predictive Control Over the Internet Using Round-Trip Delay Measurement

With the rapid development of network technology, the potential use of networked real-time control and automation is enormous and appealing. However, closed-loop control systems via the Internet are very difficult to implement practically due to their stochastic nature. The large and random time delay and data dropout caused by data transmission impact the performance of the control system and even result in system instability. To address this problem, this paper proposes a methodology to modify and enhance the conventional system so that it can be used over the Internet. This paper describes a model-based networked predictive control scheme based on round-trip time delay measurement rather than separate consideration of the feedback channel delay (between the sensor and controller) and the forward channel delay (between the controller and actuator), which successfully avoids the requirement of synchronization. It is required by many schemes but is actually hard to achieve over the Internet. Stability for both fixed and random network transmission delays is also investigated in this paper. To illustrate the control performance improvement of the proposed control scheme, the results of off-line simulations and real-time experiments via the Internet are presented.