Showing papers by "Isabela Roxana Birs published in 2018"

A novel fractional-order model and controller for vibration suppression in flexible smart beam

Abstract: Vibration suppression represents an important research topic due to the occurrence of this phenomenon in multiple domains of life. In airplane wings, vibration can cause discomfort and can even lead to system failure. One of the most frequently used means of studying vibrations in airplane wings is through the use of dedicated flexible beams, equipped with sensing and actuating mechanisms powered by suitable control algorithms. In order to optimally reject these vibrations by means of closed-loop control strategies, the availability of a model is required. So far, the modeling of these smart flexible beams has been limited to deliver integer order transfer functions models. This paper, however, describes the mathematical framework used to derive a fractional-order impedance lumped model for capturing frequency response of a flexible beam system exposed to a multisine excitation. The theoretical foundation stems from fractional calculus applied in combination with transmission line theory and wave equations. The simplified model reduces to a minimal number of parameters when converging to a limit value. It is shown that the fractional-order model outperforms an integer order model of the smart beam. Based on this novel fractional-order model, a fractional-order $$\hbox {PD}^\mu $$ controller is then tuned. The controller design is based on shaping the frequency response of the closed-loop system such that the resonant peak is reduced in comparison to the uncompensated smart beam system and disturbances are rejected. Experimental results, considering a custom-built smart beam system, are provided, considering both passive and active control situations, showing that a significant improvement in the closed-loop behavior is obtained using the proposed controller. Comparisons with a fractional-order $$\hbox {PD}^\mu $$ controller, tuned according to classical open-loop frequency domain design specifications, are provided. The experimental results show that the proposed tuning technique leads to similar results as the classical approach. Thus, the proposed method is a viable alternative, being based on closed-loop specifications, which is more intuitive for practitioners.

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

Abstract: 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.

Analytical modeling and preliminary fractional order velocity control of a small scale submersible

Abstract: This paper presents the modeling and control of a small scale submersible equipped with one propeller. The modeling process takes into consideration physical elements such as fluid statics, viscous damping and propulsive thrust. A first order transfer function with time delay is developed to make the connection between the voltage applied to the motor actuating the propeller and the velocity of the submersible. The velocity control is realized with a Fractional Order Proportional Integral (FOPI) controller that ensures zero steady state error. The controller is designed based on frequency domain specifications such as gain crossover frequency, phase margin and robustness to gain variations. The obtained fractional controller is validated through simulation in terms of steady state error and disturbance rejection performance.

Experimental results of fractional order PI controller designed for second order plus dead time (SOPDT) processes

Abstract: The present paper presentes the tuning of a Fractional Order Proportional Integral (FOPI) controller for second-order-plus-time-delay (SOPDT) plants. The tuning procedure is based on imposing frequency domain constraints for the open loop system with the FOPI controller and the SOPDT plant. The gain crossover frequency, phase margin and the iso-damping property that guarantees a certain degree of robustness to gain variations are imposed in order to obtain the parameters of the fractional order controller. The proposed method is validated by real life implementation on a process whose dynamics are approximated to a SOPDT model. The settling time, steady state error, robustness and disturbance rejection capabilities are analyzed using experimental test cases.

Fractional order based velocity control system for a nanorobot in non-Newtonian fluids

Abstract: Customized patient drug delivery overcomes classic medicine setbacks such as side effects, improper drug absorption or slow action. Nanorobots can be successfully used for targeted patient-specific drug administration, but they must be reliable in the entire circulatory system environment. This paper analyzes the possibility of fractional order control applied to the nanomedicine field. The parameters of a fractional order proportional integral controller are determined with the purpose of controlling the velocity of the nanorobot in non-Newtonian fluids envisioning the blood flow in the circulatory system.

Fractional Order Modeling and Control of a Carrier Prototype for Targeted Drug Delivery

Abstract: This paper tackles the field of applied control engineering in the nanomedical field, both in terms of modeling and control of the dynamics of a scalable robot transiting a vascular environment. An experimental fractional order model is obtained that describes the dynamics of the robot inside a secluded part of the circulatory system in terms of velocity profile and position. The submersible has concentration sensing capabilities and when a difference is detected in the liquid's concentration, a Fractional Order Proportional Integrative (FOPI) controller is used to control the robot's velocity and position inside the vascular homology. The work is based on experimental data acquired from a dedicated platform designed and built to echo environmental traits of the circulatory system for analysis and control purposes.

Different fractional order models for an experimental smart beam system

Abstract: The applicability of fractional calculus in system engineering outperforms classic identification techniques due to its ability to depict physical phenomena with increased accuracy. The present study explores the increased accuracy and flexibility of a fractional order model applied to an experimental smart beam depicting an airplane wing. The paper details the fractional order system identification of the beam and explores the possibility of realization of the model.