|A Non-Uniform Predictor-Observer for a Networked Control System
Angel Cuenca, Pedro García, Pedro Albertos, and Julián Salt
International Journal of Control, Automation, and Systems, vol. 9, no. 6, pp.1194-1202, 2011
Abstract : This paper presents a Non-Uniform Predictor-Observer (NUPO) based control approach in order to deal with two of the main problems related to Networked Control Systems (NCS) or Sensor Networks (SN): time-varying delays and packet loss. In addition, if these delays are longer than the sampling period, the packet disordering phenomenon can appear. Due to these issues, a (scarce) non-uniform, delayed measurement signal could be received by the controller. But including the NUPO proposal in the control system, the delay will be compensated by the prediction stage, and the non-available data will be reconstructed by the observer stage. So, a delay-free, uniformly sampled controller design can be adopted. To ensure stability, the predictor must satisfy a feasibility problem based on a time-varying delay-dependent condition expressed in terms of Linear Matrix Inequalities (LMI). Some aspects like the relation between network delay and robustness/performance trade-off are empirically studied. A simulation example shows the benefits (robustness and control performance improvement) of the NU-PO approach by comparison to another similar proposal.
Keyword : LMI, network delay, networked control system, packet disorder, packet loss, predictor-observer-based control.