Discrete-time Output Feedback Control Research Articles

An Output Feedback Discrete-Time Controller for the DC-DC Buck Converter

This paper presents a discrete-time output feedback controller to regulate the output voltage of a DC-DC buck converter. The proposal’s main feature is the application of a discrete-time equivalent of the robust exact filtering differentiator. First, the document exposes a theoretical analysis of the closed-loop system, where it is considered the problem of implementing a real-time differentiator with a good relationship between exactness and noise filtration performance. Hence, secondly, the controller in a laboratory setup is presented. The first experimental results suggest that the proposed controller exhibits good robustness against noise and maintains the asymptotic accuracy, even with saturated control inputs, as in the case of the DC-DC buck converter. Consequently, aiming to verify the features of the proposed method, the controller is validated through multiple experiments, showing satisfactory voltage tracking accuracy, good suppression of instantaneous load and supply voltage disturbances, and robustness against bounded measurement noise.

Estimate-Based Dynamic Event-Triggered Output Feedback Control of Networked Nonlinear Uncertain Systems

This paper develops a new estimate-based dynamic event-triggered output feedback controller for networked control systems subject to nonlinear uncertainties. Specifically, based on the sampled-data, a discrete-time output feedback controller and a discrete-time dynamic event-triggering condition are proposed by the virtue of feedback domination technique. The proposed event-triggered control method is easy to implement in digital computers due to the form of discrete time. Under the proposed dynamic event-triggered control method, the selection regions of the sampling period and the scaling gain are explicitly given to guarantee the global practical/asymptotic stability of the closed-loop system. Finally, two examples are employed to verify the efficiency of the proposed dynamic event-triggered control approach.

Periodic event-triggered robust output feedback control for nonlinear uncertain systems with time-varying disturbance

This paper investigates the periodic event-triggered robust output feedback control problem for a class of nonlinear uncertain systems subject to time-varying disturbance. By means of the feedback domination approach and disturbance compensation technique, a new framework of periodic event-triggered robust control strategy is developed in the form of output feedback, which encompasses a discrete-time event-triggering transmission scheme that is only intermittently monitored at sampling instants and a discrete-time output feedback controller consisting of a set of linear difference equations. The proposed robust method may reduce the communication resource utilization as compared to the non-event triggering schemes while maintaining a desirable closed-loop system performance even in the presence of a general class of time-varying disturbance and nonlinear uncertainties. The closed-loop system under the proposed control scheme is actually modeled as a hybrid system, and it is shown that the global practical stability of the closed-loop hybrid system is guaranteed by selecting a sufficiently large scaling gain and a sufficiently small sampling period. Finally, the experimental results on a DC–DC buck power converter are presented to illustrate the effectiveness of the proposed control approaches.

Output Feedback H-infinity Control Design for Synchronizing of the Main Drives of the Pipe-Rolling Mill

We formulate the discrete-time output feedback controller design problem where the desired accuracy of controlled variables in the mean-square sense is guaranteed in the presence of bounded polyharmonic disturbances with a priori unknown number of harmonics, amplitudes, and frequencies. The amplitudes of the harmonics must satisfy a condition that results in the boundedness of the power of each polyharmonic component. The solution is based on the discrete-time H∞-optimization procedure by properly choosing the corresponding weighting matrices of the minimax cost criterion. Numerical solution in state-space is based on the method of linear matrix inequalities, using the LMI Control Toolbox (MATLAB application). We give the numerical example for the main drives pipe-rolling mill where the digital controller is synthesized using the LMI Control Toolbox package.

Decentralised two-time-scale motions control based on generalised sampling

A design method for the decentralised time-varying discrete-time output-feedback control of linear time-invariant plants with unstable unstructured decentralised fixed modes (UDFM) is introduced. The design method uses generalised sampled-data hold functions to eliminate the UDFMs and to decouple the discrete-time equivalent model of the plant into independent input–output channels. Through this structural change, the plant becomes suitable for a stabilising high-sampling-rate controller that induces two-time-scale motions (TTSM) in the closed-loop system. As a result, the discrete-time controller is likewise decoupled into distinct local agents and the TTSM closed-loop system is decentralised.

Numerical Computation of the Minimal $\mathbfH_\infty$ Norm of the Discrete-Time Output Feedback Control Problem

Numerical computation of the minimal ${\bf H}_\infty$ norm for the discrete-time output feedback control problem is considered. First of all, a lower bound is established in terms of the ${\bf H}_\infty$ norm of certain stable transfer functions. Since the computational work in the evaluation of the ${\bf H}_\infty$ norm of a stable transfer function involves the determination of unimodular eigenvalues of the associated parameterized symplectic pencil of matrices, we discuss in detail how to get a numerically reliable solution when the pencil becomes singular as the parameter varies. Next, by exploiting the stable deflating subspaces of the two parameterized symplectic pencils derived by Iglesias and Glover in 1991, we characterize the critical points such that the corresponding two discrete-time Riccati equations (with parameter r) have stabilizing positive semidefinite solutions and satisfy certain inertia conditions. This characterization makes some kind of secant method applicable for finding these critical points. Finally, using the maximum of the two critical points as the starting point, we then devise an algorithm for computing the optimal (minimal) ${\bf H}_\infty$ norm by considering a secant method applied to the spectral radius (function of r) of the product of the corresponding two Riccati solutions. Numerical aspects are addressed throughout. In addition, some algebraic verifiable examples are given.

Optimal discrete-time structural control using direct output feedback

An optimal direct discrete-time output feedback control algorithm is developed. According to the proposed algorithm, optimal discrete-time output feedback gain is derived through a variational process such that a certain prescribed quadratic performance index is minimized. It is verified that the classical optimal discrete-time state feedback control algorithm is just a particular case of the proposed control algorithm. With the introduction of special matrix operations, optimal output feedback gain is obtained systematically by solving simultaneously linear algebraic equations iteratively. Control forces are then generated directly from output measurements multiplied by the pre-calculated shift-invariant output feedback gain. A small number of sensors and controllers, and simple on-line calculation make the proposed algorithm favorable to real-time control implementation. Numerical verification is illustrated by the control of a single degree-of-freedom (DOF) and a three degree-of-freedom structure subjected to real earthquake excitations. Differences between discrete-time and continuous-time output feedback control are discussed.

最適レギュレータ技法を用いた多入力多出力離散時間値出力フィードバック制御系構成法

最適レギュレータ技法を用いた多入力多出力離散時間値出力フィードバック制御系構成法