A single-step identification strategy for the coupled TITO process using fractional calculus

The reliable performance of a complete control system depends on accurate model information being used to represent each subsystem. The identification and modelling of multivariable systems are complex and challenging due to cross-coupling. Such a system may require multiple steps and decentralized testing to obtain full system models effectively. In this paper, a direct identification strategy is proposed for the coupled two-input two-output (TITO) system with measurable input–output signals. A well-known closed-loop relay test is utilized to generate a set of inputs–outputs data from a single run. Based on the collected data, four individual fractional-order transfer functions, two for main paths and two for cross-paths, are estimated from single-run test signals. The orthogonal series-based algebraic approach is adopted, namely the Haar wavelet operational matrix, to handle the fractional derivatives of the signal in a simple manner. A single-step strategy yields faster identification with accurate estimation. The simulation and experimental studies depict the efficiency and applicability of the proposed identification technique. The demonstrated results on the twin rotor multiple-input multiple- output (MIMO) system (TRMS) clearly reveal that the presented idea works well with the highly coupled system even in the presence of measurement noise

A robust control design approach for altitude control and trajectory tracking of a quadrotor

Introduction. Unmanned aerial vehicles as quadcopters, twin rotors, fixed-wing crafts, and helicopters are being used in many applications these days. Control approaches applied on the quadrotor after decoupling the model or separate altitude control and trajectory tracking have been reported in the literature. A robust linear H∞ controller has been designed for both altitude control and circular trajectory tracking at the desired altitude. Problem. The ability of the quadrotor system to hover at a certain height and track any desired trajectory makes their use in many industrial applications in both military and civil applications. Once a controller has been designed, it may not be able to maintain the desired performance in practical scenarios, i.e. in presence of wind gusts. Originality. This work presents the control strategy to ensure both altitude control and trajectory tracking using a single controller. Purpose. However, there is a need for a single controller that ensures both altitude control and trajectory tracking. Novelty. This paper presents a robust H∞ control for altitude control and trajectory tracking for a six degree of freedom of unmanned aerial vehicles quadrotor. Methodology. Multi input multi output robust H∞ controller has been proposed for the quadrotor for altitude control and tracking the desired reference. For the controller validation, a simulation environment is developed in which a 3D trajectory is tracked by the proposed control methodology. Results. Simulation results depict that the controller is efficient enough to achieve the desired objective at minimal control efforts. Practical value. To verify that the proposed approach is able to ensure stability, altitude control, and trajectory tracking under practical situations, the performance of the proposed control is tested in presence of wind gusts. The ability of the controller to cater to the disturbances within fractions of seconds and maintaining both transient and steady-state performance proves the effectiveness of the controller.Вступ. Безпілотні літальні апарати, такі як квадрокоптери, двороторні апарати, апарати з нерухомими крилами та гелікоптери сьогодні використовуються у багатьох сферах застосування. У літературі повідомляється про підходи до керування, застосовані на квадрокоптері після від’єднання моделі або окремого контролю висоти та відстеження траєкторії. Надійний лінійний регулятор H∞ був розроблений як для контролю висоти, так і для відстеження кругової траєкторії на потрібній висоті. Проблема. Здатність квадрокоптерної системи зависати на певній висоті та відстежувати будь-яку бажану траєкторію робить їх застосування можливим у багатьох сферах як у військових, так і в цивільних цілях. Розроблений контролер може не підтримувати бажані характеристики у реальних умовах, тобто за наявності поривів вітру. Оригінальність. У цій роботі представлена стратегія керування, яка забезпечує як контроль висоти, так і відстеження траєкторії за допомогою одного контролера. Мета. Однак існує потреба в єдиному контролері, який забезпечує як контроль висоти, так і відстеження траєкторії. Новизна. У цій статті представлено надійний регулятор H∞ для контролю висоти та відстеження траєкторії для шести ступенів свободи безпілотних літальних апаратів. Методологія. Для квадрокоптера запропоновано багатовхідний багатовихідний надійний контролер H∞ для контролю висоти та відстеження бажаного курсу. Для перевірки контролера розробляється середовище моделювання, в якому тривимірна траєкторія відстежується за запропонованою методологією керування. Результати. Результати моделювання показують, що контролер є досить ефективним для досягнення бажаної мети при мінімальних зусиллях контролю. Практична цінність. Щоб переконатися, що запропонований підхід здатний забезпечити стабільність, контроль висоти та відстеження траєкторії в реальних ситуаціях, параметри запропонованого контролю перевіряються за наявності поривів вітру. Здатність контролера усувати порушення протягом кількох секунд і підтримувати як перехідні, так і стабільні показники доводить ефективність контролера

H∞BASEDOBSERVER FOR DISTURBANCE COMPENSATION IN DECOUPLED TRMS USING LMI OPTIMIZATION

Twin Rotor MIMO System is a laboratory model of helicopter. In this paper, the problem of disturbance rejection in TRMS is dealt with. Using disturbance observers, without any additional sensors is an attractive method to attenuate the effects of disturbances as they are highly cost effective. This method uses a simple form of DOBs, which does not need to solve the plant model inverse, and uses H∞control method using LMIs to design the Q-filter in the DOB. The estimation capability of DOB is verified using simulation results in frequency domain as well as in time domain

Hybrid active force control for fixed based rotorcraft

Disturbances are considered major challenges faced in the deployment of rotorcraft unmanned aerial vehicle (UAV) systems. Among different types of rotorcraft systems, the twin-rotor helicopter and quadrotor models are considered the most versatile flying machines nowadays due to their range of applications in the civilian and military sectors. However, these systems are multivariate and highly non-linear, making them difficult to be accurately controlled. Their performance could be further compromised when they are operated in the presence of disturbances or uncertainties. This dissertation presents an innovative hybrid control scheme for rotorcraft systems to improve disturbance rejection capability while maintaining system stability, based on a technique called active force control (AFC) via simulation and experimental works. A detailed dynamic model of each aerial system was derived based on the Euler–Lagrange and Newton-Euler methods, taking into account various assumptions and conditions. As a result of the derived models, a proportional-integral-derivative (PID) controller was designed to achieve the required altitude and attitude motions. Due to the PID's inability to reject applied disturbances, the AFC strategy was incorporated with the designed PID controller, to be known as the PID-AFC scheme. To estimate control parameters automatically, a number of artificial intelligence algorithms were employed in this study, namely the iterative learning algorithm and fuzzy logic. Intelligent rules of these AI algorithms were designed and embedded into the AFC loop, identified as intelligent active force control (IAFC)-based methods. This involved, PID-iterative learning active force control (PID-ILAFC) and PID-fuzzy logic active force control (PID-FLAFC) schemes. To test the performance and robustness of these proposed hybrid control systems, several disturbance models were introduced, namely the sinusoidal wave, pulsating, and Dryden wind gust model disturbances. Integral square error was selected as the index performance to compare between the proposed control schemes. In this study, the effectiveness of the PID-ILAFC strategy in connection with the body jerk performance was investigated in the presence of applied disturbance. In terms of experimental work, hardware-in-the-loop (HIL) experimental tests were conducted for a fixed-base rotorcraft UAV system to investigate how effective are the proposed hybrid PID-ILAFC schemes in disturbance rejection. Simulated results, in time domains, reveal the efficacy of the proposed hybrid IAFC-based control methods in the cancellation of different applied disturbances, while preserving the stability of the rotorcraft system, as compared to the conventional PID controller. In most of the cases, the simulated results show a reduction of more than 55% in settling time. In terms of body jerk performance, it was improved by around 65%, for twin-rotor helicopter system, and by a 45%, for quadrotor system. To achieve the best possible performance, results recommend using the full output signal produced by the AFC strategy according to the sensitivity analysis. The HIL experimental tests results demonstrate that the PID-ILAFC method can improve the disturbance rejection capability when compared to other control systems and show good agreement with the simulated counterpart. However, the selection of the appropriate learning parameters and initial conditions is viewed as a crucial step toward this improved performance

Fractional transformation-based decentralized robust control of a coupled-tank system for industrial applications

Petrochemical and dairy industries, waste management, and paper manufacturing fall under the category of process industries where flow and liquid control are essential. Even when liquids are mixed or chemically treated in interconnected tanks, the fluid and flow should constantly be observed and controlled, especially when dealing with nonlinearity and imperfect plant models. In this study, we propose a nonlinear dynamic multiple-input multiple-output (MIMO) plant model. This model is then transformed through linearization, a technique frequently utilized in the analysis and modeling of fractional processes, and decoupling for decentralized fixed-structure H-infinity robust control design. Simulation tests based on MATLAB and SIMULINK are subsequently executed. Numerous assessments are conducted to evaluate tracking performance, external disturbance re jection, and plant parameter fluctuations to gauge the effectiveness of the proposed model. The objective of this work is to provide a framework that anticipates potential outcomes, paving the way for implementing a reliable controller synthesis for MIMO-connected tanks in real-world scenarios.This research was partially funded by FONDECYT grant number 1200525 (V.L.) from the National Agency for Research and Development (ANID) of the Chilean government under the Ministry of Science, Technology, Knowledge, and Innovation; and by Portuguese funds through the CMAT—Research Centre of Mathematics of University of Minho—within projects UIDB/00013/2020 and UIDP/00013/2020 (C.C.)

Assisting dependent people at home through autonomous unmanned aerial vehicles

This work describes a proposal of autonomous unmanned aerial vehicles (AUAVs) for home assistance of dependent people. AUAVs will monitor and recognize human activities during flight to improve their quality of life. However, before bringing such AUAV assistance to real homes, several challenges must be faced to make them viable and practical. Some challenges are technical and some others are related to human factors. In particular, several technical aspects are described for AUAV assistance: (1) flight control, based on our active disturbance rejection control algorithm, (2) flight planning (navigation in obstacle environments), and, (3) processing signals, acquired both from flight-control and monitoring sensors. From the assisted person’s viewpoint, our research focuses on three cues: (1) the user’s perception about AUAV assistance, (2) the influence on human acceptance of AUAV appearance and behavior at home, and (3) the human-robot interaction between assistant AUAV and assisted person. Finally, virtual reality environments are proposed to carry out preliminary tests and user acceptance evaluations.This work has been partially supported by Spanish Ministerio de Ciencia, Innovación y Universidades, Agencia Estatal de Investigaci´on (AEI) / European Regional Development Fund (FEDER, UE) under DPI2016-80894-R grant, and by CIBERSAM of the Instituto de Salud Carlos III. Lidia M. Belmonte holds FPU014/05283 scholarship from Spanish Ministerio de Educaci´on y Formación Profesional

A QFT robust controller as a remedy for TRMS

Control of a Twin Rotor Multi-input Multi-output System (TRMS) is not a simple work. Because it has complex nonlinear dynamics, cross-coupling, uncertainties, and instability. This paper provides a practical method for control of a TRMS, named Quantitative Feedback Theory (QFT) as one of the robust approaches. Firstly, the TRMS set and modeling procedure are introduced. Secondly, the nonlinear and linear equations of electrical and mechanical parts in both vertical and horizontal planes are presented. Next, using the QFT method, a controller is designed for motion in each plane. Finally, the robustness of the control strategy is illustrated by simulations of vertical and horizontal motions, including controller and pre-filter in the presence of uncertainties. The results demonstrate that the proposed robust controller can guarantee the system stabilization, as well as pitch and yaw tracking of TRMS

Intelligent Control of an Aerodynamical System

The paper presents the designed prototype for a highly nonlinear, multi-input-multi-output aerodynamic system. The laboratory scale equipment is created to simulate the operations of unmanned aerial vehicles. The prototype is conceived to be cheap and easy to use, in order to be multiplied for laboratory works. It is also described the first tested control strategy, based on dynamic nonlinear model inversion using artificial neural networks. The experimental results prove the efficiency of the equipment, being able to test different real operation behaviors

Enhancing disturbance rejection capability and body jerk performance of a twin-rotor helicopter model using intelligent active force control

This paper presents a study on the effectiveness of utilizing an innovative control approach based on an intelligent active force control (IAFC) strategy to stabilize a twin-rotor helicopter model and improve its ability to effectively reject external disturbances via a simulation work. A detailed mathematical model of a two-degree-of-freedom (DOF) helicopter was derived using the Euler-Lagrange method taking into account the effects of coupling and disturbances. In this developed model, a Proportional–Integral–Derivative (PID) controller was designed and combined with the proposed IAFC strategy to yield an intelligent hybrid control architecture known as a PID-IAFC scheme that can improve system performance and reject various types of applied disturbances. The intelligent algorithms used in the schemes are based on iterative learning (IL) and fuzzy logic (FL). In this work, different types of external disturbances in the form of sinusoidal waves, pulsating, and random noise disturbances were applied to the helicopter system to verify the sensitivity and durability of the proposed control schemes and consequently, a comparative study was performed to analyze the system characteristics. Notably, the efficacy of the IAFC based control unit was investigated to improve the body jerk performance in the presence of external disturbances. The acquired results reveal the effectiveness and robustness of the IAFC based controller in stabilizing the dual-rotor helicopter, rejecting the applied disturbances, and improving the body jerk performance by at least 54% for pitching and 19% for yawing motions in the presence of the pulsating disturbance, and 60% and 54%, respectively, for the random noise disturbance

Systems Structure and Control

The title of the book System, Structure and Control encompasses broad field of theory and applications of many different control approaches applied on different classes of dynamic systems. Output and state feedback control include among others robust control, optimal control or intelligent control methods such as fuzzy or neural network approach, dynamic systems are e.g. linear or nonlinear with or without time delay, fixed or uncertain, onedimensional or multidimensional. The applications cover all branches of human activities including any kind of industry, economics, biology, social sciences etc