Search results for "control theory"

An Extended Kalman Filter-Based Technique for On-Line Identification of Unmanned Aerial System Parameters

2015

ABSTRACT: The present article deals with the identification, at the same time, of aircraft stability and control parameters taking into account dynamic damping derivatives. Such derivatives, due to the rate of change of the angle of attack, are usually neglected. So the damping characteristics of aircraft dynamics are attributed only on pitch rate derivatives. To cope with the dynamic effects of these derivatives, authors developed devoted procedures to estimate them. In the present paper, a complete model of aerodynamic coefficients has been tuned-up to identify simultaneously the whole set of derivatives. Besides, in spite of the employed reduced order model and/or decoupled dynamics, a s…

Computational Analysis of the Active Control of Incompressible Airfoil Flutter Vibration Using a Piezoelectric V-Stack Actuator

2021

The flutter phenomenon is a potentially destructive aeroelastic vibration studied for the design of aircraft structures as it limits the flight envelope of the aircraft. The aim of this work is to propose a heuristic design of a piezoelectric actuator-based controller for flutter vibration suppression in order to extend the allowable speed range of the structure. Based on the numerical model of a three degrees of freedom (3DOF) airfoil and taking into account the FEM model of a V-stack piezoelectric actuator, a filtered PID controller is tuned using the population decline swarm optimizer PDSO algorithm, and gain scheduling (GS) of the controller parameters is used to make the control adapti…

Erratum to “Orbit sizes, character degrees and Sylow subgroups” [Adv. Math. 184 (2004) 18–36]

2004

Large orbits ofp-groups on characters and applications to character degrees

2005

We prove that if ap-groupA acts on a solvablep′-groupG then there is a “large” orbit on the ordinary complex irreducible characters ofG. As a consequence of this theorem we obtain results that relate ordinary and Brauer character degrees.

POSITIVE DEFINITE FUNCTIONS OF DIAGONAL LIMITS OF FINITE ALTERNATING GROUPS

2004

The normalized positive definite class functions are determined for all those direct limits of finite alternating groups for which the embeddings are natural in the sense that every non-trivial -orbit in is natural.

Orbit sizes, character degrees and Sylow subgroups

2004

Algebraic real-time algorithm for B-Spline sinusoidal pulse width modulation in three phase voltage source inverters.

2008

In this paper a novel algebraic real-time algorithm for implementation of sinusoidal pulse width modulation (SPWM) based on B-spline carriers is introduced and discussed. B-spline functions are used as carrier signals with the aim to to reduce harmonic content of the three phase inverter output voltage. This algorithm eliminates the problem of B-spline recursive evaluation with convolution integrals or convolution sums in digital counterpart. The pulse pattern synthesis is made with the help pre-calculated duty cycle expressions. In this way the carrier signals have not to be really synthesized, hence the hardware and the whole inverter control system becomes cheaper, more reliable and affo…

Architecture of a digital PFM controller for IC implementation

2006

This paper presents a digital controller architecture oriented to IC implementation. The classical digital pulse width modulator (D-PWM), using digital analog converter (DAC), is replaced with a Sigma-Delta (/spl Sigma//spl Delta/) modulator based on pulse frequency modulator (PFM) technique. Results of an investigation from a prototype for DC-DC converter, in terms of simulated and experimental performances, are reported, together with harmonic frequency investigation. The control function design is implemented on a field programmable gate array (FPGA). As a consequence of good agreement between simulated and experimental results, the proposed architecture realizes a digital control loop w…

Stochastic linearization of MDOF systems under parametric excitations

1992

Abstract The stochastic linearization approach is examined for non-linear systems subjected to parametric type excitations. It is shown that, for these systems too, stochastic linearization and Gaussian closure are two equivalent approaches if the former is applied to the coefficients of the Ito differential rule. A critical review of other stochastic linearization approaches is also presented and discussed by means of simple examples.

Non-linear oscillators under parametric and external poisson pulses

1994

The extended Ito calculus for non-normal excitations is applied in order to study the response behaviour of some non-linear oscillators subjected to Poisson pulses. The results obtained show that the non-normality of the input can strongly affect the response, so that, in general, it can not be neglected.