Optimal Sequence-Based Tracking Control over Unreliable Networks

Abstract

In networked control systems, sequence-based controllers are used to compensate for transmission delays and losses in unreliable data networks. For this purpose, the controller sends not only the current control input to the actuator but also a sequence of predicted control inputs. The additional inputs can be used when subsequent transmissions get delayed or lost. In this paper, the sequence-based method is applied to the problem of trajectory tracking over an unreliable network and an optimal sequenced-based tracking controller is derived. The main advantage of the presented approach is that future information on the reference trajectory can optimally be embedded in the predicted control sequences. Furthermore, the controller can be implemented offline. An interesting result is that the optimal controller can still be separated into a feedback part and a feedforward part (as in standard optimal tracking control) despite of both the unreliable network and the sequence-based method. The performance of the derived tracking controller is demonstrated by Monte Carlo simulations with an inverted pendulum.