Robust Gain-scheduled Controller Research Articles

OBSERVER-BASED GAIN SCHEDULING H∞ CONTROLLER FOR A 3 MOTORS WEB TRANSPORT SYSTEM

This paper deals with the robust gain scheduled control problem of a web transport system with winder and unwinder for elastic material. Precisely, the objective consists to control accurately the tension along the web and its velocity in order to prevent the occurrence of web break or fold. Due to the wide-range variation of the radius and inertia of the rollers the system dynamics change considerably during the winding/unwinding process. A Linear Parameter Varying (LPV) control strategy is derived from the interpolation of the observer state- feedback gains of H∞ robust controllers. The resulting controllers are based on unbiased LPV observers and perform well during the whole winding/unwinding process.

Design of robust gain-scheduled PI controllers for nonlinear processes

Gain-scheduling has proven to be a successful design methodology in many engineering applications. However, in the absence of a sound theoretical analysis, these designs come with no guarantees of robust stability, performance or even nominal stability of the overall gain-scheduled deign. This paper presents such an analysis for one type of nonlinear gain-scheduled control system based on the process input for nonlinear chemical processes. A methodology is also proposed for the design and optimization of the robust gain-scheduled PI controller. Conditions which guarantee robust stability and performance are formulated as a finite set of linear matrix inequalities (LMIs) and hence, the resulting problem is numerically tractable. Issues of modeling error and input-saturation are explicitly incorporated into the analysis. A simulation study of a nonlinear continuous stirred tank reactor (CSTR) process indicates that this approach can produce efficient sub-optimal robust gain-scheduled controllers.

Active vibration suppression of flexible structures: robust gain scheduled approach

The paper deals with robust gain scheduled controller design applied for active vibration suppression of flexible structures. The experimental set-up is a three-storey flexible structure with an active mass driver placed on the last storey. First, system identification experiments are performed and the plant's uncertainty is deduced. Next, robust controller design with constraint on the control signal is presented. For a better trade-off between control performance and control constraint a gain scheduling approach is investigated. Finally, the control system is tested experimentally, when the input disturbance is a scaled historical earthquake record (1940 El Centro). The experimental results show that the proposed robust gain scheduling control approach offers higher performance levels and can handle effectively extreme control conditions, such as reconnection of the control system after power failure. All results presented in the paper are experimental results. Copyright © 2004 John Wiley & Sons, Ltd.

Reducing conservatism in the design of a robust gain-scheduled controller for non-linear chemical processes

A robust control approach has been used to design gain-scheduled controllers, which guarantee closed-loop stability and performance. The inherent conservatism of robust control results in smaller ranges of parameters that satisfy the design criteria and consequently in degraded performance. The main focus of this paper is to reduce the conservatism to enhance the efficiency of the robust design method. Two approaches, the use of parameter-dependent Lyapunov condition and calculation of saturation factor bounds, are proposed to reduce the conservatism of the controller design.

Robust gain-scheduled control for vibration suppression

Limited control authority is a key issue in the field of structural control and is a major research area since most of the practical control problems are dominated by constraints on the control signal. The paper presents a simple and practical gain-scheduled controller design procedure for active vibration suppression of a three-storey flexible structure. First, system identification experiments are performed and the plant’s uncertainty is derived. Next, robust controller design with constraint on the control signal is presented. For a better trade-off between control performance and control constraint a gain-scheduling approach is investigated. Stability analysis of the gain-scheduled controller is analysed using a parameter-independent Lyapunov function (quadratic stability) as well as a parameter-dependent Lyapunov function (biquadratic stability). Finally, the gain-scheduled controller is tested experimentally when the flexible structure is excited with a scaled historical earthquake record (1940 El Centro record). Successful experimental results show that the proposed robust gain-scheduled control approach offers good performance in the case of control authority limitation.

Robust Gain-Scheduling Control for Large Flexible Spacecraft with Linear Parameter Variation.

In this paper, we study a design method of precise attitude controller of a LSS having problems of elastic vibration and parameter variation. For the problems, H∞ robust control, μsynthesis or gainscheduling control are known to be efficient. In this study, we apply gainscheduling control to the problem. Although many types of gainscheduling controller have been studied, we adopt an approach based on spline-type parameter-dependent quadratic forms. At first we describe the algorithm of control system design with some extensions. Then we evaluate its performance by a numerical simulation for a typical LSS model.

Application of velocity-based gain-scheduling to lateral auto-pilot design for an agile missile

In this paper a modern gain-scheduling methodology is proposed which exploits recently developed velocity-based techniques to resolve many of the deficiencies of classical gain-scheduling approaches (restriction to near equilibrium operation, to slow rate of variation). This is achieved while maintaining continuity with linear methods and providing an open design framework (any linear synthesis approach may be used) which supports divide and conquer design strategies. The application of velocity-based gain-scheduling techniques is demonstrated in application to a demanding, highly nonlinear, missile control design task. Scheduling on instantaneous incidence (a rapidly varying quantity) is well-known to lead to considerable difficulties with classical gain-scheduling methods. It is shown that the methods proposed here can, however, be used to successfully design an effective and robust gain-scheduled controller.

A robust gain-scheduling control based on VSC and fuzzy local controller network

Based on variable structure control (VSC) and fuzzy local controller network (FLCN), a new design method of robust gain-scheduling control is proposed in this paper. The proper sliding-modes and the tendency-rates for general operation-points are introduced such that the system gets into the sliding-modes’ motion as soon as possible and has the desired performance. Its good performance is due to the robustness of VSC. However, any local controller works well only in the local region of a specified operation-point. In this paper functions similar to the fuzzy-attributed function in fuzzy-systems are introduced to form FLCN. The simulation results showed that the presented method is feasible and acceptable.

A robust gain-scheduling control based on VSC and fuzzy local controller network

A robust gain-scheduling control based on VSC and fuzzy local controller network

Attitude Control of Spacecraft with Mobile Antenna by a Gain-Scheduled H.INF. Controller.

This paper studies the attitude control problem of a class of data relay satellite which has a large mobile antenna for tracking target spacecraft in low orbit. The movement of the antenna disturbs the satellite attitude motion through dynamic coupling of the motions of the antenna and the satellite main body. In the operation, control of the spacecraft attitude must be maintained even when the antenna rotates at a high angular velocity. In this paper, we apply robust gain-scheduled controller synthesis to this problem. The controller is designed as a robust stabilizing controller based on the H∞ controller synthesis of linear parameter varying system. The capability of the method is investigated by a numerical study.

A ROBUST GAIN-SCHEDULING CONTROL BASED ON VSC AND FUZZY LOCAL CONTROLLER NETWORK

Abst rac t : Based on variable structure control (VSC) and fuzzy local controller network (FLCN) , a new design methed of robust gain-scheduling control is proposed in this paper. l~e proper sliding-modes and the tendency-rates for general operation-points are intr~xtuced such that the system gets into the sliding-modes' motion as soon as possible and has the desired performance. Its good performance is due to the robustness of VSC. However, any local controller works well only in the local region of a specified operation-point. In this paper functions similar to the fuzzy-attributed function in fuzzy-systems are introduced to form FIX2N. The simulation results showed that the presented method is feasible and acceptable.

Robust control in uncertain nonlinear systems with exogenous signals

This paper proposes a robust gain scheduling control law in nonlinear systems with exogenous signals and structural uncertainties. A matching condition is presented to cancel the unmodelled dynam ics which appears in the linear term of the control input. Using the proposed control law, the closed-loop system which satisfies the given conditions provides the desired output error bound.

Sufficient conditions for robust performance of adaptive controllers with general uncertainty structure

Sufficient conditions are given under which an adaptive control system is robustly stable and achieves a guaranteed robust asymptotic performance level equal to that of the robust controller given perfect parameter information. The conditions are general in several respects. For example, structured non-parametric uncertainty (e.g. block diagonal) is allowed, as well as exogenous noise inputs. In addition, the structure of the parametric uncertainty is very general, and even allows for parameters which scale the uncertainty magnitudes. This allows one to identify the size of the non-parametric uncertainty and to schedule the controller based on this size. Finally, the robust gain scheduled controller is largely unrestricted. Identification mechanisms which are proven to satisfy the sufficient conditions are not given here and, for the general problem, have not yet been developed. However, an example of such a mechanism for a subclass of systems does exist and is referenced. For the general problem, this paper provides properties to be sought in the development of robust identification laws for robust adaptive control.