Multi-output Networked Control Systems Research Articles

Analysis of optimal performance of MIMO networked control systems with encoding and packet dropout constraints

In this study, optimal performance of the multi-input multi-output networked control systems (NCSs) is analysed. The systems are with a time-delay and channel noise constraints in the forward network channel, and encoding-decoding and quantisation constraints, and packet dropouts in the feedback network channel. By using the Youla parameterisation of a two-degree-of-freedom controller, a new and explicit expression of the optimal performance is derived. The optimal performance is obtained using the method of H 2 norm technique. The results show that the positions and directions of the non-minimum phase zeros and unstable poles of a given plant are related to the optimal tracking error. On the other hand, the optimal tracking error is dependent on channel noise, quantisation noise, encoding-decoding, time-delay, packet dropout probability and other correction factors. Finally, simulation results demonstrate the effectiveness of the proposed control scheme.

Time Decision for Multi-Input and Multi-Output Networked Control Systems

In a networked control system with multiple inputs and multiple outputs, the send time is the time instant at which a sensor sends the sampling signal to the controllers, and the perform time is the time instant at which an actuator starts performing the control commands. The relationship between the send time and perform time is nonlinear from the traditional perspective. This article formulates such a nonlinear timing relationship as a linear form based on a special algebraic structure. An algorithm is developed to find all legal send times that allow the control commands to be performed at the given time. It is pointed out that the problem for finding all legal send times is nondeterministic polynomial (NP)-hard. In addition, the method for finding the latest legal send time is presented, which has a polynomial complexity. This article also analyzes the robustness of networked control systems with perturbations, which decides the send time such that the actuators can perform the control commands at the specified time no matter how the time delays vary in bounded intervals. Numerical examples are used to illustrate the presented algorithm.

New Smith predictive fuzzy immune PID control algorithm for MIMO networked control systems

Aiming at the problem of network-induced delays for multi-input multi-output networked control systems (MIMO NCS), a new Smith predictive fuzzy immune PID algorithm is introduced to effectively reduce the adverse effect of network-induced delays about stability in MIMO NCS, firstly, by using the v-norm type to decouple the coupling plant. Based on the generalized plant after decoupling, the new Smith predictor is designed. Then, an modified fuzzy immune feedback control algorithm is used to tune PID controller parameters online. When there is a model mismatch or parameter perturbation, the set-point tracking performance and robustness of output response can be significantly optimized. The proposed algorithm does not contain the network delay prediction model and does not need to measure, estimate, or identify the network delay. It can be used in MIMO NCS where the network bandwidth is constrained and the network-induced delays are large. Numerical examples with Ethernet protocol are built to illustrate the correctness and effectiveness of this new algorithm.

Stability Analysis of Multi-input and Multi-output Networked Control Systems

The stability of multi-input and multi-output networked control systems (MIMO NCS) is considered in this paper. A less conservative delay dependent stability criterion for MIMO NCS is proposed in terms of linear matrix inequality. The new result is obtained by taking the relationship between the delay upper bounds into account in Lyapunov functional, estimating the upper bound of the derivative of Lyapunov functional without ignoring the additional useful terms and introducing the new free-weighting matrices. The resulting criterion is also extended to the stability analysis for MIMO NCS with time-varying structured uncertainties. Numerical example demonstrates that the proposed criteria are less conservative than the existing ones.