Multi-input 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.

Performance Analysis of NCSs Under Channel Noise and Bandwidth Constraints

This paper investigates the performance limitation of multi-input multi-output (MIMO) networked control systems (NCSs). The communication channel is modeled as a power constrained channel with channel noise and the bandwidth constraints. The optimal performance index of the system is expressed by the covariance of the reference input signal and the system output error signal. Some new results about MIMO NCSs are obtained by co-prime factorization, inner-outer factorization and spectral decomposition techniques. The results demonstrate that the tracking performance depends on the non-minimum phase zeros, unstable poles and their directions. At the same time, the network communication parameters constraints, energy constraints and the essential feature of reference input signal also restrict the performance. Some illustrative examples are presented to demonstrate the feasibility of the proposed methods.

Tracking Performance Limitations of MIMO Networked Control Systems With Multiple Communication Constraints.

In this paper, the tracking performance limitation of networked control systems (NCSs) is studied. The NCSs are considered as continuous-time linear multi-input multioutput (MIMO) systems with random reference noises. The controlled plants include unstable poles and nonminimum phase (NMP) zeros. The output feedback path is affected by multiple communication constraints. We focus on some basic communication constraints, including additive white noise (AWN), quantization noise, bandwidth, as well as encoder-decoder. The system performance is evaluated with the tracking error energy, and used a two-degree-of-freedom (2DOF) controller. The explicit representation of the tracking performance is given in this paper. The results indicate the tracking performance limitations rely to internal characteristics of the plant (unstable poles and NMP zeros), reference noises [the reference noise power distribution (RNPD) and its directions], and the characteristics of communication constraints. The characteristics of communication constraints include communication noise power distribution (CNPD); quantization noise power distribution (QNPD), and their distribution directions; transform bandwidth allocation (TBA); transform encoder-decoder allocation (TEA), and their allocation directions; and NMP zeros and MP part of bandwidth. Moreover, the tracking performance limitations are also affected by the angles between the each transform NMP zero direction and RNPD direction, and these angles between each transform unstable poles direction and the direction of communication constraint distribution/allocation. In addition, for MIMO NCSs, bandwidth (there are not identical two channels) can always affect the direction of unstable poles, and the channel allocation of bandwidth and encode-decode may be used for a feasible method for the performance allocation of each channel. Finally, an instance is given for verifying the effectiveness of the theoretical outcomes.

Optimal modified performance of MIMO networked control systems with multi-parameter constraints

The optimal modified performance of the multi-input multi-output (MIMO) networked control systems (NCSs) with encoding–decoding, channel noise in the forward channel and packet dropouts, quantization in the feedback channel is investigated in this paper. A new and efficient tracking performance index for the NCSs is presented which prevents variations in the tracking error where there is no integrator in the plant. The optimal modified performance is obtained by the method of coprime factorization and partial fraction. The results demonstrate that the optimal modified performance is related to the locations of the non-minimum phase (NMP) zeros, unstable poles of the given plant as well as their directions. In addition, the modified factor, packet dropouts probability, channel noise and encoding–decoding are also closely related to optimal modified performance of the NCSs. Finally, we present some particular examples to illustrate the theoretical results.

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.

Optimal modified tracking performance for MIMO networked control systems with communication constraints

This paper investigates the optimal modified tracking performance of multi-input multi-output (MIMO) networked control systems (NCSs) with packet dropouts and bandwidth constraints. Some explicit expressions are obtained by using co-prime factorization and the spectral decomposition technique. The obtained results show that the optimal modified tracking performance is related to the intrinsic properties of a given plant such as non-minimum phase (NMP) zeros, unstable poles, and their directions. Furthermore, the modified factor, packet dropouts probability and bandwidth also impact the optimal modified tracking performance of the NCSs. The optimal modified tracking performance with channel input power constraint is obtained by searching through all stabilizing two-parameter compensator. Finally, some typical examples are given to illustrate the effectiveness of the theoretical results.

Modelling and stability analysis of MIMO networked control systems withmulti-channel random packet losses

Traditional networked control systems (NCSs) analysis and design have been based on the single closed-loop configuration. This paper studies the modelling and stability of multi-input multi-output (MIMO) networked control systems (NCSs) with multiple channels. Unlike the NCSs based on the single close-loop configuration, there exist data packet dropout, data packet out-of-order and network-induced delay in every channel, which make multi-channel MIMO NCSs more complex. In order to solve these network-related non-deterministic issues, a general switched system model with unknown switched sequence for multi-channel MIMO NCSs is first proposed, which can not only describe the MIMO NCSs where the controller communicates with sensors and actuators through distinct channels, but also can describe the NCSs based on the single closed-loop configuration. Based on Lyapunov stability theory combined with linear matrix inequalities (LMIs) techniques, a sufficient condition is then derived for multi-channel MIMO NCSs to be asymptotical stable in term of a set of bilinear matrix inequalities. Furthermore, the proposed results are easily extended to the uncertain MIMO NCSs. Finally, simulation results confirm the feasibility and effectiveness of the proposed method.