Isabela R. Birs

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.

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.

Modelling and calibration of a conventional activated sludge wastewater treatment plant

Wastewater treatment plants (WWTPs) are key infrastructures for ensuring a proper protection of the environment. Mathematical modelling and simulation of activated sludge systems have gained increasing attention in control engineering within the last years. The most widely used models to describe the biochemical processes that take place in a WWTP are the Activated Sludge Models 1-3. Due to their increased complexity, these models are often unsuited for control systems design. The aim of this paper is to develop reduced order models which can adequately describe the biochemical processes for the purpose of on-line control design. The models developed contain a minimum number of variables and parameters that allow for model identification and validation based on available on-line measurements.

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.

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.

Experimental Validation of a Novel Auto-Tuning Method for a Fractional Order PI Controller on an UR10 Robot

Classical fractional order controller tuning techniques usually consider the frequency domain specifications (phase margin, gain crossover frequency, iso-damping) and are based on knowledge of a process model, as well as solving a system of nonlinear equations to determine the controller parameters. In this paper, a novel auto-tuning method is used to tune a fractional order PI controller. The advantages of the proposed auto-tuning method are two-fold: There is no need for a process model, neither to solve the system of nonlinear equations. The tuning is based on defining a forbidden region in the Nyquist plane using the phase margin requirement and determining the parameters of the fractional order controller such that the loop frequency response remains out of the forbidden region. Additionally, the final controller parameters are those that minimize the difference between the slope of the loop frequency response and the slope of the forbidden region border, to ensure the iso-damping property. To validate the proposed method, a case study has been used consisting of a pick and place movement of an UR10 robot. The experimental results, considering two different robot configurations, demonstrate that the designed fractional order PI controller is indeed robust.

An optimal fractional order controller for vibration attenuation

Unwanted vibrations may cause severe damage and may endanger the lives of passengers on board of an airplane. In the last years, there has been an increased focus on the study of active vibration techniques. A viable possibility to actively control the vibration of an airplane wing is by using piezoelectric actuators. The paper presents a novel tuning procedure of a fractional order Proportional Derivative controller based on three points of the magnitude Bode diagram. The eloquence of the controller is experimentally validated on an experimental setup consisting of an aluminum beam that replicates an airplane wing.

Fractional order modeling and control of a smart beam

Smart beams are one of the most frequently used means of studying vibrations in airplane wings. Their mathematical models have been so far solely based on classical approaches that ultimately involve integer order transfer functions. In this paper, a different approach towards modeling such smart beams is considered, an approach that is based on fractional calculus. In this way, a fractional order model of the smart beam is obtained, which is able to better capture the dynamics of the system. Based on this novel fractional order model, a fractional order PDμ controller is then tuned according to a set of three design constraints. This design leads to a closed loop system that exhibits a much smaller resonant peak compared to the uncompensated smart beam system. Experimental results are provided, considering both passive and active control responses of the smart beam, showing that a significant improvement of the closed loop behavior is obtained using the designed controller.