Application Of Linear Control Techniques Research Articles

Performance of the adaptive sliding mode control scheme for output voltage control of the DC/DC buck converter system

In this work, the DC output voltage of a step-down DC/DC buck converter system has been controlled using different schemes of sliding mode controllers (SMCs) such as classical sliding mode controller (CSMC), modified sliding mode controller (MSMC) and the adaptive sliding mode controller (ASMC). As the DC/DC buck converter is a nonlinear and time-variant system, the application of linear control techniques for controlling this type of converters is not always suitable. Therefore, the SMCs are used here due to their characteristic features of maintaining the overall system stability with acceptable performance in the absence or presence of the parameters uncertainty and external disturbance. The simulation results obtained using MATLAB/Simulink software show the advantages of using ASMC in terms of reducing the settling time, the chattering value in the control action and the steady state error but the hitting time is increased when compared with the CSMC. Besides, the simulation results show the advantages of using ASMC in terms of reducing the settling time and the chattering value, but the steady state error and the hitting time are increased when compared with the MSMC. Since the buck converter is a fast response system, the performance of the ASMC is better than that of the CSMC and MSMC in terms of reducing the settling time and the chattering value in the control action.

NARMAX Identification Based Closed-Loop Control of Flow Separation over NACA 0015 Airfoil

A closed-loop control algorithm for the reduction of turbulent flow separation over NACA 0015 airfoil equipped with leading-edge synthetic jet actuators (SJAs) is presented. A system identification approach based on Nonlinear Auto-Regressive Moving Average with eXogenous inputs (NARMAX) technique was used to predict nonlinear dynamics of the fluid flow and for the design of the controller system. Numerical simulations based on URANS equations are performed at Reynolds number of 106 for various airfoil incidences with and without closed-loop control. The NARMAX model for flow over an airfoil is based on the static pressure data, and the synthetic jet actuator is developed using an incompressible flow model. The corresponding NARMAX identification model developed for the pressure data is nonlinear; therefore, the describing function technique is used to linearize the system within its frequency range. Low-pass filtering is used to obtain quasi-linear state values, which assist in the application of linear control techniques. The reference signal signifies the condition of a fully re-attached flow, and it is determined based on the linearization of the original signal during open-loop control. The controller design follows the standard proportional-integral (PI) technique for the single-input single-output system. The resulting closed-loop response tracks the reference value and leads to significant improvements in the transient response over the open-loop system. The NARMAX controller enhances the lift coefficient from 0.787 for the uncontrolled case to 1.315 for the controlled case with an increase of 67.1%.

A New Sliding Mode Controller for DC/DC Converters in Photovoltaic Systems

DC/DC converters are widely used in many industrial and electrical systems. As DC/DC converters are nonlinear and time-variant systems, the application of linear control techniques for the control of these converters is not suitable. In this paper, a new sliding mode controller is proposed as the indirect control method and compared to a simple direct control method in order to control a buck converter in photovoltaic applications. The solar arrays are dependent power sources with nonlinear voltage-current characteristics under different environmental conditions (insolation and temperature). From this point of view, the DC/DC converter is particularly suitable for the application of the sliding mode control in photovoltaic application, because of its controllable states. Simulations are performed in Matlab/Simulink software. The simulation results are presented for a step change in reference voltage and input voltage as well as step load variations. The simulations results of proposed method are compared with the conventional PID controller. The results show the good performance of the proposed sliding mode controller. The proposed method can be used for the other DC/DC converter.

Takagi-Sugeno fuzzy modeling of a two-wheeled inverted pendulum robot

A two wheeled inverted pendulum TWIP mobile robot is an under-actuated mechanical system, which is inherently open-loop unstable with highly nonlinear dynamics. This property attracts the interest of researchers worldwide in recent years. This paper presents the development of a linearized model of the TWIP mobile robot based on its nonlinear dynamical model using Takagi-Sugeno T-S fuzzy modeling technique, which can allow the application of linear control techniques in analyzing and efficiently controlling such under-actuated nonlinear system. The complete nonlinear dynamical equations of motion of the TWIP mobile robot were first derived using Kane's Method. Based on the nonlinear dynamical equations of motion, a T-S fuzzy model of the TWIP robot was then developed using local approximation technique. To validate the proposed model, simulations study was carried out and the results show that the proposed model approximates the original nonlinear TWIP mobile robot in the pre-specified domains to certain degree of accuracy.

Call for Papers: International Journal of Robust and Nonlinear Control Performance of Nonlinear Control Systems

The International Journal of Robust and Nonlinear Control is inviting papers for a special issue on ‘Performance of Nonlinear Control Systems’ (for a description of the scope, see below). Authors are kindly requested to submit their papers by October 1st 2011 following the link Online Submission on the journals homepage: wileyonlinelibrary.com/journal/rnc. Authors must select Nathan van de Wouw or Marcel Heertjes as the Submitting Editor. Each submission must be clearly identified as a submission for this special issue by entering Performance of Nonlinear Control Systems in the Special Issue Title Field. The manuscripts should be prepared in accordance with the publication format described in ‘For Authors’ on the journal homepage. Scope: The topic of this special issue is the performance analysis and performance-oriented design of nonlinear control systems. Nonlinear control has received wide attention in the systems and control literature and examples of the practical application of nonlinear control in practice are widely available. Still, the majority of the (theoretical) advances made are related to the design of stabilizing nonlinear controllers for (nonlinear) plants, indeed no easy task in general, while not accounting for performancerelated issues. Moreover, in many industries, still the application of linear control techniques prevails. One of the main reasons is the fact that performance is key in practical applications, be it in the form of transient performance criteria, such as rise time and overshoot, or in the form of sensitivity to perturbations, such as measurement noise and external disturbances. On the one hand, linear control techniques have been so successful since a profound (frequencydomain) framework for performance analysis exists. On the other hand, linear control is subject to fundamental (performance) limitations, a famous example of which is the Bode sensitivity integral. Nonlinear control may overcome such limitations. To harvest the full potential of nonlinear control in practice, the further development of powerful performance analysis tools for nonlinear control systems and matching performance-based design techniques for nonlinear controllers are needed, hence this special issue. Resuming, topics of particular interest are, but not limited to: • Performance limitations in linear control systems and how nonlinear control may be employed to overcome such limitations. • Tools for performance analysis of nonlinear control systems. • Performance-based synthesis techniques of nonlinear controllers. • (Industrial) application of high-performance nonlinear controllers.

How significant are transfer function relations and invariant points for a quarter car suspension model?

The quarter car model has been used extensively to study the benefits of active, semi-active and passive suspensions. Despite the evident simplicity of the model, the insights obtained from this model have been found to have counterparts in half- and full-car suspension models. Among the most interesting results of the analysis of the quarter car are the relationships among certain transfer function and invariant points in the frequency response functions. These results are of great interest for the application of linear control techniques to the design of active suspensions and the optimisation of linearised passive suspensions. This paper attempts to show why some of the limitations implied by the model are less absolute than they at first seem.