Adaptive Control for Systems with Randomly Missing Measurements in a Network Environment

Networked control systems (NCSs) are a type of distributed control systems, where the information of control system components (reference input, plant output, control input, etc.) is exchanged via communication networks. Due to the introduction of networks, NCSs have many attractive advantages, such as reduced system wiring, low weight and space, ease of system diagnosis and maintenance, and increased system agility, which motivated the research in NCSs. The study of NCSs has been an active research area in the past several years, see some recent survey articles (Chow & Tipsuwan, 2001; Hespanha & Naghshtabrizi, 2007; Yang, 2006) and the references therein. On the other hand, the introduction of networks also presents some challenges such as the limited feedback information caused by packet transmission delays and packet loss; both of them are due to the sharing and competition of the transmission medium, and bring difficulties for analysis and design for NCSs. The information transmission delay arises from by the limited capacity of the communication network used in a control system, whereas the packet loss is caused by the unavoidable data losses or transmission errors. Both the information transmission delay and packet loss may result in randomly missing output measurements at the controller node, as shown in Fig. 1. So far different approaches have been used to characterize the limited feedback information. For example, the information transmission delay and packet losses have been modeled as Markov chains (Zhang et al., 2006). The binary Bernoulli distribution is used to model the packet losses in (Sinopoli et al., 2004; Wang et al., 2005 a & 2005 b). The main challenge of NCS design is the limited feedback information (information transmission delays and packet losses), which can degrade the performance of systems or even cause instability. Various methodologies have been proposed for modeling, stability analysis, and controller design for NCSs in the presence of limited feedback information. A novel feedback stabilization solution of multiple coupled control systems with limited communication is proposed by bringing together communication and control theoretical issues in (Hristu & Morgansen, 1999). Further the control and communication codesign methodology is applied in (Hristu-Varsakelis, 2006; Zhang & Hristu-Varsakelis, 2006) – a method of stabilizing linear NCSs with medium access constraints and transmission delays by designing a delay-compensated feedback controller and an accompanying medium