A discrete robust adaptive control of a tilt-rotor UAV for an enlarged flight envelope
2017 IEEE 56th Annual Conference on Decision and Control (CDC), 2017
This work presents the modeling and control of a tilt-rotor UAV with tail controlled surfaces for... more This work presents the modeling and control of a tilt-rotor UAV with tail controlled surfaces for path tracking with improved forward flight performance. A nonlinear dynamic model is obtained through Euler-Lagrange formulation and linearized around a reference trajectory in order to obtain a linear parameter-varying model. The forward velocity is treated as an uncertain parameter, and the linearized system is represented as a set of polytopes with nonempty intersection regarding the forward velocity. Feedback gains are computed for each of the vertices of the polytopes using a discrete mixed control approach with pole placement constraints strategy. The resultant feedback gain, which is able to control the system inside a given polytope, is obtained using an adaptive law through an optimal convex combination of the vertices' gains. Finally, an adaptive mixing scheme is used to smoothly schedule the feedback gains between the polytopes.
Nonlinear $\mathcal{H}_{2}$ and $\mathcal{H}_{\infty}$ control formulated in the Weighted Sobolev space for underactuated mechanical systems with input coupling
2018 IEEE Conference on Decision and Control (CDC), 2018
Two important paradigms in control theory are the nonlinear $\mathcal{H}_{2}$ and $\mathcal{H}_{\... more Two important paradigms in control theory are the nonlinear $\mathcal{H}_{2}$ and $\mathcal{H}_{\infty}$ control approaches. Despite many advantages, such approaches present limitations in the sense to control the transient closed-loop response. An interesting approach to address these issues is the formulation of both controllers in the Sobolev space $\mathcal{W}_{m, p}$. However, the latter also presents drawbacks, now in sense of weighting the cost variable and its time derivatives component-wise. Therefore, aiming to deal with underactuated mechanical systems with input coupling, this work presents a new formulation of the nonlinear $\mathcal{H}_{2}$ and $\mathcal{H}_{\infty}$ control approaches in the Weighted Sobolev space $\mathcal{W}_{m, p,\sigma}$. It is also shown that for the particular systems treated in this work the $\mathcal{W}_{2}$ and $\mathcal{W}_{\infty}$ optimal controllers are equivalent. In addition, a particular solution is proposed to the HJB and HJBI equatio...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This paper presents a singular perturbation control strategy for regulating both the longitudinal... more This paper presents a singular perturbation control strategy for regulating both the longitudinal and the lateral-directional flight dynamics of an Unmanned Aerial Vehicle (UAV). The proposed control strategy is based on a double four-timescale (4TS) decomposition of the longitudinal and lateral-directional dynamics. The longitudinal dynamics include the altitude, velocity, pitch, and flight path angle dynamics, with the control signals being the elevator deflection and the throttle position, while the lateral-directional dynamics include the side-slip angle, bank angle, yaw rate and roll rate dynamics, with the control signals being the aileron and rudder deflection. The nonlinear control strategy drives the system to follow references in the aerodynamic velocity, the flight path angle and the load factor, which in return provides references in bank angle, side-slip angle and yaw rate. In addition, the control strategy allows to select the desired dynamics for all the singularly perturbed subsystems. Numerical results are included for a realistic nonlinear UAV model, including control saturation and presenting control robustness capabilities under unmodelled dynamics.
Two important paradigms in control theory are the classic nonlinear H 2 and H ∞ control approache... more Two important paradigms in control theory are the classic nonlinear H 2 and H ∞ control approaches. Their background theory are well developed, and several applications have demonstrated their efficiency. Despite many advantages, they suffer from deficiencies such as minimum settling-time and minimum overshoot. An interesting approach to solve these limitations is the formulation of both controllers in the Sobolev space. Thanks to the nature of the W − norm, the cost variable and its time derivatives are taken into account in the cost functional, leading to controllers with improved transient and steady-state performance. Thus, aiming to deal with mechanical systems this work reformulates the H 2 and H ∞ controllers in the Sobolev space. It is shown that, for particular systems, the W 2 and W ∞ optimal controllers are equivalent. An optimal solution for the class of fully actuated mechanical systems is proposed. The controller is corroborated by numerical experiments conducted with a quadrotor UAV.
In this study an adaptive critic based neural network controller is developed to obtain near opti... more In this study an adaptive critic based neural network controller is developed to obtain near optimal control laws for a nonlinear automatic flight control system. The adaptive critic approach consists of two neural networks. The first network, called the critic, captures the mapping between the states of a dynamical system and the co-states that arise in an optimal control problem. The second network, called the action network, maps the states of a system to the control. This study uses nonlinear aircraft models in the stall regions from a paper (Garrad and Jordan^ to develop optimal neural controllers for an aircraft; we then compare the results with singular perturbation based nonlinear controllers developed in the literature. The results show that with the neural controllers the aircraft can operate in a broader region of angles of attack beyond stall as compared to other linear and nonlinear controllers. Introduction Neural networks have gained a lot of attention in the field of...
Wide band-gap (WBG) semiconductors technology represents a potential candidate to displace conven... more Wide band-gap (WBG) semiconductors technology represents a potential candidate to displace conventional silicon (Si) technology used in power electronics. Between Silicon Carbide (SiC) and Gallium Nitride (GaN) power semiconductors, the latter is the least mature of both technologies, with many open research problems, especially in the aerospace industry. In this paper, we address the design and implementation of a DC/DC converter for a hybrid small unmanned aerial vehicle (UAV) based on GaN technology. Both theoretical and simulation comparisons of Si, SiC and GaN transistors for the converter are presented. The conclusion is that GaN devices are the most appropriate to fulfill converter requirements for the size and weight limitations of the selected UAV. The paper presents a buck converter which handles an input voltage range of 32 V to 40 V and provides a 12 V regulated output and output power up to 60 W. The experimental results carried out on the prototype converter show how promising the GaN technology is for aerospace systems, not only regarding its volume and size, but also its efficiency. Besides, practical implementation details are reported to contribute to the design of small, light and reliable GaN power converters for aeronautics. INDEX TERMS Aerospace electronics, DC-DC power converters, Gallium Nitride (GaN) transistors, wide band-gap (WBG) semiconductors, unmanned aerial vehicle (UAV).
Emergency locator transmitters (ELTs) used to locate manned aircrafts are not well suited to find... more Emergency locator transmitters (ELTs) used to locate manned aircrafts are not well suited to find and recover small crashed unmanned aerial vehicles (UAVs). ELTs utilize an international satellite system for search and rescue (Cospas-Sarsat System), which should leverage its expensive resources to save lives as a priority. Besides, ELTs are too big and heavy to be used within small UAVs. Some of the existing solutions for this problem are based on receivers that detect signal strength, which may be a long and tedious process not suitable for user needs. Others do not have enough range or require radio license and expensive amateur radio receivers. This paper presents an emergency radio beacon specifically designed to locate small UAVs. It is triggered automatically in the event of a crash and allows finding and recovering a crashed UAV in a fast and simple way. It meets not only the required specifications of user-friendliness, size and weight of this kind of application, but also it is a high precision and low cost device. Besides, it has enough range and endurance. The experiments carried out show the operation of the proposed system. INDEX TERMS Aerospace electronics, emergency beacon, localization system, low cost, radio beacon, sensor systems, unmanned aerial vehicle.
A robust adaptive mixing control for improved forward flight of a tilt-rotor UAV
2016 IEEE 19th International Conference on Intelligent Transportation Systems (ITSC), 2016
This work presents the modeling and control of a tilt-rotor UAV, with tail controlled surfaces, f... more This work presents the modeling and control of a tilt-rotor UAV, with tail controlled surfaces, for path tracking with improved forward flight. The dynamic model is obtained using the Euler-Lagrange formulation considering the aerodynamic forces and torques exerted on the horizontal and vertical stabilizers, and fuselage. For control design purposes, the equations of motion are linearized around different operation points to cover a large range of forward velocity. Based on these linearized dynamic models, a mixed H2/H∞ robust controller is designed for each operation point. Therefore, an adaptive mixing scheme is used to perform an on-line smooth gain-scheduling between them. Simulation results show the control strategy efficiency when the UAV is designated to have a forward acceleration and perform a circular trajectory subject to a wind disturbance.
This article presents a college course experience taught in the final academic year of the Aerosp... more This article presents a college course experience taught in the final academic year of the Aerospace Engineering program at the University of Seville, in which students design an airplane taking the specification submitted by the instructor, following the Project Based Learnig (PBL) methodology. Students are organized into groups forming "companies" that have to defend their proposed design with the "client". The article presents the usual steps of the PBL methodology showing the feasibility of applying this methodology to large workgroups. The complete design of an aircraft is the result of a compromise between knowledge, experience and teamwork in a collaborative environment. The students need to understand that each of the different areas are necessary pieces of the larger puzzle of aircraft design, and they need to find the key that solves this puzzle. The main objective of this course it to provide instructions to complete that puzzle by introducing concurrent engineering and PBL methodologies.
Esta publicaci6n ha sido posible gracias a la ayuda para la divulgaci6n de proyectos de in ves ti... more Esta publicaci6n ha sido posible gracias a la ayuda para la divulgaci6n de proyectos de in ves ti gaci6n, innovacio n y
Development of propulsive models to be used in the Aircraft Design classes. The models include pa... more Development of propulsive models to be used in the Aircraft Design classes. The models include parametric equations to model turbo-fan, turbo prop and piston-prop variations.
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