Stability and Time Delay Tolerance Analysis Approach for Networked Control Systems

Abstract

Networked control system is a research area where the theory is behind practice. Closing the feedback loop through shared network induces time delay and some of the data could be lost. So the network induced time delay and data loss are inevitable in networked control Systems. The time delay may degrade the performance of control systems or even worse lead to system instability. Once the structure of a networked control system is confirmed, it is essential to identify the maximum time delay allowed for maintaining the system stability which, in turn, is also associated with the process of controller design. Some studies reported methods for estimating the maximum time delay allowed for maintaining system stability; however, most of the reported methods are normally overcomplicated for practical applications. A method based on the finite difference approximation is proposed in this paper for estimating the maximum time delay tolerance, which has a simple structure and is easy to apply.

Application of Internet of Things Hardware in Control Systems

“…The restrictions that arise from the nature of communication protocols related to the degree of determinism and allowable data rates supported by a particular protocol can also be added to communication constraints. The communication constraints affect the behavior of networked control systems by degrading their performances and disturbing their stability [31]. The development of communication technologies over the last fifteen years has greatly influenced the development of networked control systems, while the development of information technologies and the Internet has enabled these systems to collect and process large amounts of data (big data) and react to fluctuations in the behavior of plant from anywhere, anytime.…”

Networked and Cloud Control Systems - Modern Challenges in Control Engineering

“…A simple stability analysis method will be presented below, which allows determination of the maximum allowable delay bound in a continuous NCS derived using finite difference approximation of the delay term and Lyapunov system stability theorem. Derived theorem and corollaries given bellow are from [13] where they are explained in more detail and appropriate proofs can be found there as well.…”

“…Theorem [13]: Suppose that assumptions above hold. For system (7) with the feedback control (8), the closed-loop system is globally asymptotically stable if where  is the absolute value.…”

“…The main one is that, in the process of the mathematical formulation of the method, a certain number of approximations have been made and some higher order members have been neglected. These details can be found in [13]. In addition, by making the assumptions mentioned in II B., some aspects of data transfer that in real-time networks inevitably occur (e.g.…”

“…Communication constraints are mainly related to network induced delays (delays in transmitting sensor and control data), data consistency (some data packets may be missing during communication) and synchronization (different control components can work on different clocks). These limitations can significantly degrade the performance of the control system and make it unstable under certain conditions [13]- [16]. Maintaining the stability of a networked system is a basic task that needs to be fulfilled when NCS is designed.…”