Ovidiu Prodan

A fractional order controller for seismic mitigation of structures equipped with viscoelastic mass dampers

In this paper a fractional order (FO) controller is proposed for solving the vibration suppression problem in civil structures. A laboratory scaled steel structure, with one floor, modeled as a single degree-of-freedom system is used as a case study. Two passive control solutions are proposed: a tuned mass damper (TMD) and a viscoelastic damper (VED), the latter being modeled using fractional derivatives. The simulation results show that the VED is able to further reduce the vibrations induced as forced oscillations or due to seismic excitation inputs, as compared to the passive TMD. The FO controller is then tuned using a new approach based on imposing a magnitude condition for the closed-loop system at the structural resonance frequency. The resulting FO active control strategy, together with the VED, ensures an increased seismic mitigation. Structural modeling errors are also considered, with the proposed active FO control strategy behaving robustly in terms of vibration suppression. The novelty of the paper resides in the tuning approach, as well as in the proposed active control strategy that is based upon combing VEDs, described using an FO model, and an FO controller.

Comparative analysis and exprimental results of advanced control strategies for vibration suppression in aircraft wings

The smart beam is widely used as a means of studying the dynamics and active vibration suppression possibilities in aircraft wings. The advantages obtained through this approach are numerous, among them being aircraft stability and manoeuvrability, turbulence immunity, passenger safety and reduced fatigue damage. The paper presents the tuning of two controllers: Linear Quadratic Regulator and Fractional Order Proportional Derivative controller. The active vibration control methods were tested on a smart beam, vibrations being mitigated through piezoelectric patches. The obtained experimental results are compared in terms of settling time and control effort, experimentally proving that both types of controllers can be successfully used to reduce oscillations. The analysis in this paper provides for a necessary premise regarding the tuning of a fractional order enhanced Linear Quadratic Regulator, by combining the advantages of both control strategies.

Vibration suppression in smart structures using fractional order PD controllers

Several important domains, such as the aerospace industry, are confronted with problems related to vibration. The solutions for reducing these vibrations are numerous, but are limited to a large number of passive methods, while the active solutions involve classical and intelligent control techniques. The present paper proposes a fractional order PD controller, for which the control parameters are computed in order to directly limit the vibrations at the resonance frequencies. The case study consists in a beam containing smart sensors and actuators using piezoelectric materials. The simulation results, considering both free and forced vibrations responses of the smart beam, show that the proposed method is simple and leads to an improvement of the closed loop behavior.

Experimental results of a fractional order PD λ controller for vibration suppresion

Vibration occurs in numerous important domains, such as the aerospace industry, and has negative effects since it can limit the life span of the devices, cause malfunctioning or even system instability. The necessity of research on vibration suppression in aeroplane wings is important from a scientific and technologic point of view: to provide better, more efficient, robust, cheaper solutions to eliminate vibrations effects, which triggers the socioeconomic aspect regarding the increase of flight safety and passenger comfort. Vibration suppression can be achieved using passive techniques, but they come along with certain disadvantages related to efficiency/costs. An alternative solution is to use active control. Several active control strategies have been proposed so far, with aeroplane wings/helicopter blades simulated as smart cantilever beams. The present paper proposes a fractional order Proportional Derivative controller, designed using frequency domain specifications. The case study consists in a smart beam equipped with dedicated sensors and actuators. The experimental results, considering both passive and active control responses of the smart beam, show that the proposed method leads to significant improvement of the closed loop behavior.

Design and experimental validation of an optimal fractional order controller for vibration suppression

In this paper, a fractional order optimal controller is designed, tested and validated experimentally for seismic mitigation in a one floor structure. The design is based on a two-step optimization procedure. The first step is concerned with the computation of the classical optimal controller gains. A second step follows that deals with the computation of an optimal fractional order parameter value that minimizes the attenuation level. The designed controller is implemented and tested experimentally on a laboratory scale civil structure. For comparison purposes, the passive seismic mitigation case is also considered, as well as the active case using the traditional optimal controller. The closed loop experimental results show that the designed fractional order optimal controller can ensure an improved attenuation level in the occurrence of a seismic event in comparison to the classical optimal controller.

Vibration suppression with fractional-order PIλDμ controller

Cantilever beams have an important role in day to day life in bridges, towers, buildings and aircraft wings, making active vibration suppression a highly researched field. The purpose of this paper is to detail the design of fractional order PID controllers for smart beams. A novel tuning procedure is proposed based on solving a set of nonlinear complex equations that directly aim at reducing the resonant peak. The control parameters are computed through optimization techniques, making sure that the best ones are chosen. The practical stand was realized using magnet-coil approach and not piezoelectric actuators. The experimentally obtained vibration results prove that fractional order PID controllers can be used in practice to significantly reduce the amplitude and settling time of the vibrating system.

Tuning Method of Fractional Order Controllers for Vibration Suppression in Smart Structures

Vibration suppression is a major problem in various domains, with applications ranging from medical devices to aerospace engineering. Several methods for suppressing vibrations have been proposed, but very few address this issue from the fractional calculus perspective. The emerging new fractional order controllers have the ability to meet more design specifications at the same time, behaving robustly against modeling uncertainties, external disturbances, etc. In this paper, a new tuning method for fractional order PDµ controller is proposed in which the design directly addresses the problem of suppressing resonance frequency vibrations. The case study consists in an unloaded smart beam. The simulation results, considering an additional situation of the loaded smart beam, show that the proposed method is simple and leads to a robust closed loop behavior.

An Autotuning Method for a Fractional Order PD Controller for Vibration Suppression

Fractional order controllers are receiving an ever-increasing interest from the research community due to their advantages. However, most of the tuning procedures for fractional order controllers assume a fully known mathematical model of the process. In this paper, an autotuning method for the design of a fractional order PD controller is presented and applied to the vibration suppression in airplane wings. To validate the designed controller, an experimental unit consisting of a smart beam that simulates the behaviour of an airplane wing is used. The experimental results demonstrate the efficiency of the designed controller in suppressing unwanted vibrations.