Selim Sivrioglu

Adaptive backstepping control of variable speed wind turbines

Variable speed wind turbines maximize the energy capture by operating the turbine at the peak of the power coefficient, however parametric uncertainties in mechanical and electrical dynamics of the system may limit the efficiency of the turbine. In this study, we present an adaptive backstepping approach for the variable speed control of wind turbines. Specifically, to overcome the undesirable effects of parametric uncertainties, a desired compensation adaptation law (DCAL) based controller has been proposed. The proposed method achieves global asymptotic rotor speed tracking, despite the parametric uncertainty on both mechanical and electrical subsystems. Extensive simulation studies are presented to illustrate the feasibility and efficiency of the method proposed.

LPV gain-scheduling controller design for a non-linear quarter-vehicle active suspension system

There always exists a conflict between ride comfort and suspension deflection performances during the vibration control of suspension systems. Active suspension control systems, which are designed by linear methods, can only serve as a trade-off between these conflicting performance criteria. Both performance objectives can only be accomplished at the same time by using a nonlinear controller. This paper addresses the non-linear induced L2 control of an active suspension system, which contains non-linear spring and damper elements. The design method is based on the linear parameter varying (LPV) model of the system. The proposed method utilizes the bilinear damping characteristic, stiffening spring characteristic when the suspension deflection approaches the structural limits, mass variations and parameter-dependent weighting filters. Simulation studies both in time and frequency domain demonstrate that the active suspension system controlled by the proposed method always guarantees an agreement between acceleration (comfort) and suspension deflection magnitudes together with a high ride performance.

Low Power Consumption Nonlinear Control with H∞ Compensator for a Zero-Bias Flywheel AMB System

A nonlinear control approach based on a control current switching rule is studied experimentally for an energy storage flywheel active magnetic bearing (AMB) system. In the proposed control, only one electromagnet in each axis of the AMB has a current flow at any given time, depending on the rotor displacement. This results in a power consumption that is lower than a linear control employing a bias current. The equation of motion for the rigid rotor-AMB system is transformed to have a decentralized structure for the control design. To compute nonlinear control currents, an H ∞ compensator is designed for each axis of the AMB. The proposed approach is experimentally verified using a high-speed digital signal processor.

Active vibration control using LMI-based mixed H/sub 2//H/sub /spl infin// state and output feedback control with nonlinearity

In this paper, the mixed H/sub 2//H/sub /spl infin// control is studied using linear matrix inequality approach (LMI). In many linear control problems, the design constraints can be reformulated in terms of LMI. In general, H/sub /spl infin// control maintains good frequency response performance but transient response of control system may not be guaranteed. Here we have formulated H/sub /spl infin// and H/sub 2/ control separately by means of LMI and also combined both objectives as a mixed control problem. We applied mixed H/sub 2//H/sub /spl infin// control to an active vibration control problem and obtained the reasonable results in frequency and time domain. The design approach described here is based on numerical optimization technique which requires efficient convex optimization software.

Variable Speed Control of Wind Turbines: A Robust Backstepping Approach

Abstract Variable speed wind turbines maximize the energy capture by operating the turbine at the peak of the power coefficient, however parametric uncertainties and disturbances may limit the efficiency of a variable speed turbine. In this study, we present a robust backstepping approach for the variable speed control of wind turbines. Specifically, to overcome the undesirable effects of parametric uncertainties and disturbance effects a nonlinear robust controller have been proposed. The proposed method achieves globally uniformly ultimately bounded rotor speed tracking, despite the parametric uncertainty on both mechanical and electrical subsystems. Extensive simulation studies are presented to illustrate the feasibility and efficiency of the method proposed

Levitation analysis of a ring shaped permanent magnet–high temperature superconductor vertical bearing system

This paper presents a model of the interaction between a ring shaped high temperature superconductor (HTS) and a permanent magnet (PM), using the frozen image approach. The levitation configuration of a ring permanent magnet inside a ring HTS resembles the radial type bearings found in many machine systems. The dynamical behaviour of the PM–HTS bearing mostly depends on the stiffness of the levitation. For the proposed PM–HTS configuration, the stiffness is computed on the basis of a magnetic potential obtained with a frozen image concept. The variation of the stiffness is analysed for angular and translational movements.

LPV Model Based Gain-scheduling Controller for a Full Vehicle Active Suspension System

This article addresses the design of a gain-scheduling type nonlinear controller for a full-vehicle active suspension system. The proposed method is based on a Linear Parameter Varying (LPV) model of the system. In this model, the variations in suspension deflection and mass are chosen as the scheduling parameters. During the simulations, the full-vehicle system that is controlled by the proposed method is tested with different road profiles, having high and low bumps, hollows and combinations of the two. The simulation results demonstrate that the proposed method successfully maximizes the ride comfort when suspension deflection is far away from the structural limits and minimizes the suspension deflection by changing its behavior when the suspension limits are reached.

A Dynamical Stiffness Evaluation Model for a Ring-Shaped Superconductor Magnetic Bearing System

In this paper, a rotor-permanent magnet inside a ring-shaped superconductor magnetic bearing system is modeled and simulated using a dynamic stiffness approach. Analytical expressions of the stiffness effects are defined on the basis of a magnetic potential obtained with a frozen-image concept. For engineering applications, the rotor dynamics must be considered with the effective stiffness of the ring-shaped superconducting magnetic bearing. In the proposed model, the variation of the stiffness and the dynamics of the rotor are analyzed for some initial angular and translational movements.

H Control for Suppressing Acoustic Modes of a Distributed Structure Using Cluster Sensing and Actuation

This research work presents an H ∞ control design based on cluster sensing and actuation to suppress acoustic modes of a distributed panel structure which is subjected to excitation with varying frequency. A state—space model of the planar structure is obtained based on cluster sensing and cluster actuation. Uncertainty sources are considered for robustness of the control system. The eigenvalues of the structure’s acoustic power modes are assumed to vary with the excitation frequency in order to consider sound radiation from the vibrating panel structure. The proposed controller design covers the uncertainties caused by varying disturbance frequencies and inhomogeneities of the structure.

Adaptive output backstepping control of a flywheel zero-bias AMB system with parameter uncertainty

In this study, a nonlinear control approach based on the control current switching of the electromagnets is realized experimentally for a flywheel AMB system. The adaptive output backstepping is used to compute nonlinear control currents by accepting that the rotor and AMB parameters are unknown. One of the improvements obtained in this study is the lower energy consumption of the AMB system due to decreased control currents. Simulation and experimental results showed promising improvements for practical implementations.