28 research outputs found
Optimized state feedback regulation of 3DOF helicopter system via extremum seeking
Get PDFIn this paper, an optimized state feedback regulation of a 3 degree of freedom (DOF) helicopter is designed via extremum seeking (ES) technique. Multi-parameter ES is applied to optimize the tracking performance via tuning State Vector Feedback with Integration of the Control Error (SVFBICE).
Discrete multivariable version of ES is developed to minimize a cost function that measures the performance of the controller. The cost function is a function of the error between the actual and desired axis positions. The controller parameters are updated online as the optimization takes place. This method significantly decreases the time in obtaining optimal controller parameters. Simulations were conducted for the online optimization under both fixed and varying operating conditions. The results demonstrate the usefulness of using ES for preserving the maximum attainable performance
Fault-tolerant Control Design to Enhance Damping of Inter-area Oscillations in Power Grids
Get PDFSUMMARY In this paper passive and active approaches for the design of fault-tolerant controllers (FTCs) are presented. The FTCs are used to improve the damping of inter-area oscillations in a power grid. The effectiveness of using a combination of local and remote (wide-area) feedback signals is first demonstrated. The challenge is then to guarantee a minimum level of dynamic performance following a loss of remote signals. The designs are based on regional pole-placement using Linear Matrix Inequalities (LMIs). First, a passive FTC is proposed. It is shown that the computation of the controller reduces to the solution of bilinear matrix inequalities. An iterative procedure is then used to design the controller. Next, as an alternative to active, time varying controllers, one for each fault scenario, we propose an approach for the design of a 'minimal switching' FTC in which only one controller is designed, but where a simple switch is incorporated into the controller structure. A case study in a linear and nonlinear Nordic equivalent system is presented to show that the closed-loop response using a conventional control (CC) design could deteriorate the performance or even destabilize the system if the remote signals are lost and to demonstrate the effectiveness of the proposed FTC designs. KEY WORDS: Fault-tolerant control, regional pole-placement, simultaneous design, power oscillation damping, local and remote feedback
Fault-tolerant wide-area control of power systems
No full textIn this thesis, the stability and performance of closed-loop systems
following the loss of sensors or feedback signals (sensor faults) are
studied. The objective is to guarantee stability in the face of sensor
faults while optimising performance under nominal (no sensor fault)
condition. One of the main contributions of this work is to deal effectively
with the combinatorial binary nature of the problem when
the number of sensors is large. Several fault-tolerant controller and
observer architectures that are suitable for different applications are
proposed and their effectiveness demonstrated. The problems are formulated
in terms of the existence of feasible solutions to linear matrix
inequalities. The formulations presented in this work are described
in a general form and can be applied to a large class of systems. In
particular, the use of fault-tolerant architectures for damping inter-area
oscillations in power systems using wide-area signals has been
demonstrated. As an extension of the proposed formulations, regional
pole placement to enhance the damping of inter-area modes has been
incorporated. The objective is to achieve specified damping ratios
for the inter-area modes and maximise the closed-loop performance
under nominal condition while guaranteeing stability for all possible
combinations of sensors faults. The performances of the proposed
fault-tolerant architectures are validated through extensive nonlinear
simulations using a simplified equivalent model of the Nordic power
system.Open Acces
On-line estimation approaches to fault-tolerant control of uncertain systems
Get PDFThis thesis is concerned with fault estimation in Fault-Tolerant Control (FTC) and as such involves the joint problem of on-line estimation within an adaptive control system. The faults that are considered are significant uncertainties affecting the control variables of the process and their estimates are used in an adaptive control compensation mechanism. The approach taken involves the active FTC, as the faults can be considered as uncertainties affecting the control system. The engineering (application domain) challenges that are addressed are:
(1) On-line model-based fault estimation and compensation as an FTC problem, for systems with large but bounded fault magnitudes and for which the faults can be considered as a special form of dynamic uncertainty.
(2) Fault-tolerance in the distributed control of uncertain inter-connected systems
The thesis also describes how challenge (1) can be used in the distributed control problem of challenge (2). The basic principle adopted throughout the work is that the controller has two components, one involving the nominal control action and the second acting as an adaptive compensation for significant uncertainties and fault effects. The fault effects are a form of uncertainty which is considered too large for the application of passive FTC methods. The thesis considers several approaches to robust control and estimation: augmented state observer (ASO); sliding mode control (SMC); sliding mode fault estimation via Sliding Mode Observer (SMO); linear parameter-varying (LPV) control; two-level distributed control with learning coordination
