Output-feedback Design Method Research Articles

Nonovershooting Cooperative Output Regulation of Linear Multiagent Systems by Dynamic Output Feedback

We consider the problem of cooperative output regulation for linear multiagent systems. A distributed dynamic output feedback design method is presented that solves the cooperative output regulation problem and also ensures that all agents track the desired reference signal without overshoot in their transient response.

Static output feedback fault tolerant control using control allocation scheme

SummaryThis paper describes two novel schemes for fault tolerant control using robust suboptimal static output feedback design methods. These schemes can also be employed as actuator redundancy management for overactuated uncertain linear systems. In contrast to many existing methods in the literature that assume the control input matrix (i) is not of full‐rank such that it can be factorized into two matrices and (ii) it does not involve uncertainty, these schemes can be applied to systems whose control input matrix cannot be factorized and/or involve uncertainty. The so‐called virtual control, in these schemes, is calculated using suboptimal ‐based static output feedback design schemes constructed to be robust against uncertainties emanating from inherent input matrix uncertainty and visibility of the control allocator to the controller. Then, using two proposed control allocation schemes (fixed and on‐line), the obtained virtual control signal is redistributed among remaining (redundant or nonfaulty) set of actuators. As the proposed schemes are modular‐based, they can be employed as real‐time fault tolerant control schemes with no need to reconfigure the controller in the case of actuator faults or failures. The effectiveness of the proposed schemes is discussed and compared with numerical examples.

Auxiliary‐function‐based double integral inequality approach to stability analysis of load frequency control systems with interval time‐varying delay

A new approach is presented for the stability problem of one-area and multi-area load frequency control (LFC) scheme with time delays in this study. Novel stability criteria with delay dependency in terms of linear matrix inequalities for LFC systems are derived by an augmented Lyapunov–Krasovski functional with triple integral terms. The LFC design takes the interval time-varying communication delays into account and the load disturbance is mathematically modelled as a norm-bounded non-linear function. This study suggests a new class of inequality for double integral of quadratic functions via intermediate auxiliary functions, which produce more tighter bounds than what Wirtinger's double integral inequality produces. Case studies are carried out to illustrate the validity of the proposed delay-dependent proportional–integral-based output feedback design method.

H∞ Optimal Performance Design of an Unstable Plant under Bode Integral Constraint

This paper proposed the H∞ state feedback and H∞ output feedback design methods for unstable plants, which improved the original H∞ state feedback and H∞ output feedback. For the H∞ state feedback design of unstable plants, it presents the complete robustness constraint which is based on solving Riccati equation and Bode integral. For the H∞ output feedback design of unstable plants, the medium‐frequency band should be considered in particular. Besides, this paper presents the method to select weight function or coefficients in the H∞ design, which employs Bode integral to optimize the H∞ design. It takes a magnetic levitation system as an example. The simulation results demonstrate that the optimal performance of perturbation suppression is obtained with the design of robustness constraint. The presented method is of benefit to the general H∞ design.

Semi-global stabilization by an output feedback law from a hybrid state controller

This article suggests a design method of a hybrid output feedback for SISO continuous systems. We focus on continuous systems for which there exists a hybrid state feedback law. A local hybrid stabilizability and a (global) complete uniform observability are assumed to achieve the stabilization of an equilibrium with a hybrid output feedback law. This is an existence result. Moreover, assuming the existence of a robust Lyapunov function instead of a stabilizability assumption allows to design explicitly this hybrid output feedback law. This last result is illustrated for linear systems with reset saturated controls.

Optimization and static output-feedback control for half-car active suspensions with constrained information

In this paper, the static output-feedback control problem of active suspension systems with information structure constraints is investigated. In order to simultaneously improve the ride comfort and stability, a half car model is used. Other constraints such as suspension deflection, actuator saturation, and controller constrained information are also considered. A novel static output-feedback design method based on the variable substitution is employed in the controller design. A single-step linear matrix inequality (LMI) optimization problem is solved to derive the initial feasible solution with a sparsity constraint. The initial infeasibility issue of the static output-feedback is resolved by using state-feedback information. Specifically, an optimization algorithm is proposed to search for less conservative results based on the feasible controller gain matrix. Finally, the validity of the designed controller for different road profiles is illustrated through numerical examples. The simulation results indicate that the optimized static output-feedback controller can achieve better suspension performances when compared with the feasible static output-feedback controller.

Stable controller design of MIMO systems in real Grassmann space

A new design method of a stable dynamic output feedback (DOF) controller in linear MIMO systems is presented on the frame of real Grassmann spaces. For the analysis, the DOF systems are decomposed into augmented static output feedback (SOF) systems using signal flow graph analysis of all DOF loops. For synthesis and design, the characteristic polynomial of the augmented SOF system for the system’s stable poles and the sub-characteristic polynomial of the sub-SOF system for the controller’s stable poles are parametrized within their Grassmann invariants in real Grassmann spaces, whose coordinates are defined in the real coefficient function spaces of their augmented SOF variables. The numerical parametrization and computation algorithm for a stable controller design is illustrated over a MIMO plant of a practical aircraft carrier model.

ROBUST NETWORKED OUTPUT FEEDBACK PREDICTIVE CONTROLLER DESIGN

Paper studies the problem of robust networked static output feedback model predictive controller design that stabilizes uncertain system with guaranteed cost. The upper bound on the time-delay is assumed to be bigger than sampling time. Control design is based on sufficient robust stability condition formulated as a solution of bilinear matrix inequality BMI. The example illustrates the viability of the proposed output feedback design method.

ROBUST MODEL PREDICTIVE CONTROL DESIGN OF SWITCHED SYSTEMS

The paper addresses the problem of designing a robust output/state model predictive control for linear polytopic switched systems. We propose the new method for calculation of control algorithm parameters for predictive and robust control of linear switched polytopic system. Lyapunov function approach guarantees the parameter-dependent quadratic stability and guaranteed cost for closed-loop system. In the proposed control scheme the required on-line computation load is significantly less than in MPC literature, which opens possibility to use these control design scheme not only for plants with slow dynamics but also for faster ones. Sufficient robust stability conditions are given in the form of BMI. The example shows the effectiveness of the proposed output feedback design methods.

入力飽和を有するサーボ系に対する出力フィードバック補償器の設計方法

This paper considers linear time-invariant continuous-time servosystems with control input saturation nonlinearities, and proposes a design method of output feedback controllers satisfying a regional integral quadratic performance for the systems based on the generalized sector approach. The method assumes the output of the nonlinearities to be available for the control, and then it is an integrated design of dynamic output feedback and anti-windup compensators with a given servocompensator based on an error system regarding a steady state as a new origin. In this case, this paper clarifies that the design problem using the method can be recast as a convex optimization problem based on linear matrix inequalities (LMIs), and a problem setting initial states of the compensators can be recast as a problem solving linear matrix equations (LMEs), respectively. Finally, this paper points out that the proposed design method is helpful through a numerical example designing the servosystem with anti-windup structure via the derived LMIs and LMEs.

TAKING ADVANTAGE OF HOMOGENEITY: A UNIFIED FRAMEWORK FOR OUTPUT FEEDBACK CONTROL OF NONLINEAR SYSTEMS

A unified framework is presented for global output feedback stabilization of a family of uncertain systems with low- and high-order nonlinearities. By taking advantage of homogeneity, together with a domination-based observer/controller design, this framework not only incorporates a number of results proposed recently in the literature, but also yields new results for more general classes of non-uniformly observable and non-smoothly stabilizable systems, whose global stabilization problem cannot be addressed by existing output feedback control schemes. The novelty of this paper lies in the development of a reduced order observer-based output feedback design method, making it possible to compensate simultaneously low-order nonlinearities that dominate near the origin, and high-order nonlinearities that dominate far away from the origin.

Universal adaptive control of nonlinear systems with unknown growth rate by output feedback

This paper investigates the problem of global stabilization by output feedback, for a family of uncertain nonlinear systems without zero dynamics. These nonlinear systems are dominated by a triangular system satisfying linear growth condition. In contrast to the previous work in the literature, the growth rate here is a positive constant but not known a priori, and therefore the problem becomes more involved and difficult. Using the idea of universal control combined with the output feedback design method developed in Qian and Lin (2002, 2003), we explicitly construct a universal-type adaptive output feedback controller which globally regulates all the states of the uncertain systems without knowing the growth rate.

UNIVERSAL OUTPUT FEEDBACK CONTROL OF NONLINEAR SYSTEMS WITH UNKNOWN GROWTH RATE

This paper investigates the problem of global stabilization by output feedback for a family of uncertain nonlinear systems dominated by a triangular system satisfying linear growth condition. In contrast to the previous work in the literature, the growth rate here is a positive constant but not known a priori, and therefore the problem cannot be addressed by the existing output feedback control schemes. Using the idea of universal control integrated with the recent output feedback design method that is not based on the separation principle, we construct a universal-type output feedback controller which globally regulates all the states of the uncertain systems without knowing the growth rate. We also discuss briefly how this result can be extended to a larger class of nonlinear systems with unknown parameters.

H ∞ control for sampled-data nonlinear systems described by Takagi–Sugeno fuzzy systems

In this paper we consider the design problem of output feedback H ∞ controllers for sampled-data fuzzy systems. We first transfer them into equivalent jump fuzzy systems. We establish the so-called Bounded Real Lemma for jump fuzzy systems and give a design method of γ-suboptimal output feedback H ∞ controllers in terms of two Riccati inequalities with jumps. We then apply the main results to the sampled-data fuzzy systems and obtain a design method of γ-suboptimal output feedback H ∞ controllers. We give a numerical example and construct a γ-suboptimal output feedback H ∞ controller.

Nonsmooth output feedback stabilization of a class of genuinely nonlinear systems in the plane

In this note, we address the problem of output feedback stabilization for a class of planar systems that are inherently nonlinear in the sense that the linearized system at the origin is neither controllable nor observable. Moreover, the uncontrollable modes contain eigenvalues on the right-half plane. By the well-known necessary condition, such planar systems cannot be stabilized, even locally by any smooth output feedback, and hence must be dealt with by nonsmooth output feedback. The main contribution of this work is the development of a non-Lipschitz continuous output feedback design method that leads to a solution to the problem. The proposed output feedback control scheme is not based on the separation principle but rather, relies on the design of a reduced-order nonlinear observer from an earlier paper with an appropriate twist, and the tool of adding a power integrator. A non-Lipschitz continuous output feedback controller is explicitly constructed, achieving global stabilization of the planar systems without imposing the high-order growth conditions required in a previous paper.

Observer-Based Quadratic Stabilization with Dominant Pole Placement

This paper proposes an observer-based output feedback design method which attains both quadratic stabilization and dominant pole placement. For a system whose state signal is unavailable and whose coefficient matrices have structured uncertainty, the method gives a controller which satisfies an H∞ norm condition for quadratic stability and the partial pole configuration, under a certain sufficient condition. This is achieved by means of the parameterization of partial pole placement which has already been known for the state feedback case. Degradation due to adopting state observers is then discussed. A numerical example is given to illustrate the proposed method.

Output-Feedback Control of a Hydraulic Drive using Balanced Model Reduction Design Method

Abstract An output feedback design method using balanced model reduction is discussed. Principal component analysis, the fundamental idea of balancing, is used to derive measures of controllability, reachability, constructibility and observability. Balanced model reduction, which is based on truncating the least reachable and observable state variables, is modified to get a stationary exact reduced model. Reducing the original to the order of the measurable variables leads to an output feedback control law which approximates a state feedback designed beforehand. The method is applied to the model of a hydraulic drive. The controlled variables are position and cumulative pressure of the cylinder chambers

Excitation controller design of synchronous machines with dynamic and proportional-plus-integral output feedback

Abstract Two output feedback methods are employed to place, in a desirable manner, the poles (eigenvalues) of a single-input single-output time-invariant linear model of a synchronous machine with AVR (supplying power to an infinite grid through a step-up transformer and a high-voltage transmission line). Thus, we design a suitable excitation controller and hence obtain a certain closed-loop system which enhances the dynamic stability characteristics of the machine. The proposed output feedback design methods are simple to apply. The results of the simulations considered in this work attest favourably to the fact that the controllers designed in this way are conducive to real implementation.

Dynamic output feedback control of a class of uncertain systems

A dynamic output feedback controller, which guarantees global uniform ultimate boundedness, is derived for a class of single-input, single-output systems with bounded uncertainty. The main feature of the approach is that the positive real condition, required by the static output feedback design method of [1], is not imposed on the class of systems considered here.