Marco Lovera

• Professor
• Politecnico di Milano

This paper presents the design of an active balancing system for rotating orbital devices, motivated by recent space applications for spacecraft endowed with rotating payloads. The main motivation behind this work is the Copernicus Imaging Microwave Radiometry mission, which will feature a large rotating microwave radiometer to provide observations...

According to the literature, Unmanned Aerial Vehicles (UAVs) promise to improve logistics processes, as they are environmentally friendly, provide an economic advantage and improve delivery services simultaneously. However, existing research has primarily focused on the operational aspects of UAVs technology, neglecting a comprehensive understandin...

The potential of In-Orbit Servicing (IOS) to extend the operational life of satellites and the need to implement Active Debris Removal (ADR) to effectively tackle the space debris problem are well known among the space community. Research on technical solutions to enable this class of missions is thriving, also pushed by the development of new cont...

In this paper, the Politecnico di Milano solutions proposed for the Leonardo Drone Contest (LDC) are presented. The Leonardo Drone Contest is an annual autonomous drone competition among universities, which has already seen the conclusion of its second edition. In each edition, the participating teams were asked to design and build an autonomous mu...

In the last decade, the space sector has seen rapid growth with new players entering the business, bringing with them a wave of innovation in spacecraft design and development solutions. This innovation includes the attempt to simplify processes to aid reduction of development cost and time through the use of existing solutions in other sectors and...

This article addresses the problem of air-to-air autonomous landing of a small underactuated unmanned aerial vehicle (UAV) on a larger one (carrier) in a noncooperative manner using vision-based state estimation. A Kalman filter-based state estimator reconstructs the state of the carrier relying on a camera mounted on the small UAV (follower). Then...

In this paper an approach to the design of robust global attitude tracking controllers for fully actuated rigid bodies is proposed. The challenge of simultaneously dealing with topological obstructions to global attitude tracking and with disturbances affecting the attitude dynamics is tackled by means of a hybrid hierarchical design that exploits...

Over the last 20 years, the demand for transport services has grown thanks to increasing globalization and e-commerce exponentially. This led to the rise in externalities (e.g., air pollution, climate change, noise pollution, traffic congestion), an issue that is particularly relevant in urban contexts. The improvement of last-mile delivery process...

The objective of this paper is to summarize the relevant published research studies on the extraction of linear time-periodic (LTP) systems and their higher order linear time-invariant (LTI) reformulations from rotorcraft physics-based models and on the identification of LTP systems from rotorcraft experimental data. The paper begins with an introd...

We present FAST-Hex, a micro aerial hexarotor platform that allows to seamlessly transit from an under-actuated to a fully-actuated configuration with only one additional control input, a motor that synchronously tilts all propellers. The FAST-Hex adapts its configuration between the more efficient but underactuated, collinear multi-rotors, and the...

This paper describes a library for flexible multibody spacecraft dynamics developed by Politecnico di Milano under a European Space Agency (ESA) contract. The objectives of the activity were to design and implement an easy-to-use Simscape library for spaceflight systems able to model several spacecraft configurations considering all the components...

The problem of model identification for the local dynamics of a flapping wing MAV is considered. Following a discussion of the underlying modelling challenges, an approach to model identification is proposed and two subspace model identification methods for LTP and LPV systems are applied and compared, with the aim of obtaining a high fidelity mode...

The role of laboratory activities in engineering education is fundamental to enhance the students engagement and learning. In this paper we discuss the use of a laboratory test-bed for education and research developed to replicate the dynamic behavior and the control design challenges of an underactuated multirotor Unmanned Aerial Vehicle (UAV), wh...

In this paper we present the one-semester course “Adaptive and Autonomous aerospace Systems” to be taught to master students in aerospace engineering at Politecnico di Milano starting fall 2021. The paper discusses the course motivation and objectives, how it fits within the current study program in aerospace engineering, the course syllabus and or...

In this paper we present the design of a laboratory test-bed for education and research which is intended to replicate the dynamic behavior and the control design challenges of an underactuated multirotor Unmanned Aerial Vehicle (UAV). The proposed setup is designed to study the longitudinal and pitch dynamics of a multirotor UAV by running experim...

In this brief, we present and validate an antiwindup (AW) control design suitable to deal with saturated discrete-time linear plants. Following the modern approach to AW design, the proposed synthesis procedure is based on the compensator paradigm in which the AW controller acts on top of a baseline one, tuned to achieve desirable performance in th...

The problem of designing the longitudinal flight controller for a quad-tilt-wing unmanned aerial vehicle to achieve robust performance under constraints on the controller structure is considered. An approach based on μ-synthesis is proposed, in which a nonparametric inverse multiplicative uncertainty description is employed to account for the uncer...

In this paper, the problem of tuning the attitude control system of a multirotor unmanned aerial vehicle (UAV) is tackled and a data-driven approach is proposed. With respect to previous work, the data used to tune the controller gains is collected in flight during closed-loop experiments. Furthermore, the simultaneous tuning of roll and pitch atti...

In this paper we propose an anti-windup strategy to counteract directionality effects arising in saturated MIMO systems in which independent dynamical subsystems are coupled through a static mixing of the inputs. Since such systems are affected by undesired input cross-couplings when saturation occurs, we propose an anti-windup augmentation scheme...

In this article, recently proposed control methods, suitable for trajectory tracking in fully actuated unmanned aerial vehicles (UAVs), are reviewed and experimentally compared. We specifically focus on multirotor platforms with tiltable propellers, for which the thrust and torque delivered by each rotor can be oriented within the aircraft frame us...

Magnetic control has been used for decades for spacecraft detumbling, i.e., to bring a spacecraft to a final condition with a sufficiently small angular momentum after separation from the launcher. This task is typically achieved by controllers based on the so-called b-dot principle, which stands out thanks to its simplicity, reliability and ease o...

In this paper, the authors propose an UAV-based automatic inspection method for photovoltaic plants analyzing and testing a vision-based guidance method developed to this purpose. The maintenance of PV plants represents a key aspect for the profitability in energy production and autonomous inspection of such systems is a promising technology especi...

We address stabilization of vectored-thrust unmanned aerial vehicles (UAVs): a challenging task due to the peculiar nonlinear underactuated dynamics. According to a well-established approach based on the selection of suitable error variables, the error dynamics is described as a pseudo cascade connection where the attitude subsystem indirectly stab...

In this paper robust attitude tracking for fully actuated rigid bodies is addressed. By exploiting the cascade structure of the underlying mathematical model, a hierarchical framework including a large number of dynamic feedback controllers is proposed. The closed loop results in error dynamics comprising an inner loop associated with the angular v...

Aerospace control education can significantly benefit from actual hands-on experience. In most cases, however, such experience can only be provided to students in small-scale project activities. In this paper the experience gathered in integrating laboratory activities in aerospace control education in the UAV Lab and in the Advanced Aerospace Cont...

In this paper, the problem of developing a real-time correction technique for the flight path of a multirotor UAV for PV plants inspections using visual information is presented and discussed. More precisely, in the proposed approach, the information obtained from a monocular RGB camera, exploiting computer vision edge detection and feature extract...

In this paper we study active balancing systems tailored to space applications which involve rotating devices mounted on spacecraft. The behavior of these systems can be severely affected by the force and torque arising at the interface point from unpredictable inertial asymmetries of the rotating device. Therefore, a suitable mechanism to countera...

This paper addresses the trajectory tracking control problem for underactuated UAVs, with specific focus on vehicles with thrust-vectoring capabilities. According to the different actuation mechanisms, the most common UAV platforms can achieve only a partial decoupling of attitude and position tasks. Since position tracking is of utmost importance...

Nowadays, Unmanned Aerial Vehicles (UAVs) are continuing to enlarge their market share and the related research activities are growing exponentially. In particular, the interaction between two or more vehicles during flight (e.g., formation flight and refuelling) are getting more and more attention. When dealing with intelligence, surveillance, and...

We revisit attitude stabilization for inertial pointing spacecraft endowed with magnetic actuators. Under mild assumptions on the time-variability of the geomagnetic field, it was proven that a quaternion-based PD-like controller can guarantee global convergence to the desired attitude provided that the gains are sufficiently small, thus posing an...

This paper presents an attitude control design suitable to counteract the effects of actuators saturation on the stability and performance of multirotor UAVs. The proposed strategy is based on an anti-windup compensator scheme that allows augmenting a baseline cascaded attitude controller in which the inner loop controller is linear. The anti-windu...

Linear Parameter Varying (LPV) modelling has been studied in aeronautics for a long time as a means to formulate gain-scheduling problems in a systematic way, in terms of number of involved parameters and interpolation points. In this paper the development of a quasi-LPV (qLPV) or “stitched” model for helicopter dynamics is presented and discussed,...

In this paper, the adaptive augmentation of the attitude control system for a multirotor unmanned aerial vehicle is considered. The proposed approach allows to combine a baseline controller with an adaptive one and to disable or enable the adaptive controller when needed, in order to take the advantages of both the controllers. To improve transient...

This paper addresses the trajectory tracking control problem for underactuated VTOL UAVs. According to the different actuation mechanisms, the most common UAV platforms can achieve only a partial decoupling of attitude and position tasks. Since position tracking is of utmost importance for applications involving aerial vehicles, we propose a contro...

In this paper a geometric approach to the trajectory tracking control of Unmanned Aerial Vehicles (UAVs) with thrust vectoring capabilities is proposed. The control problem is developed within the framework of geometric control theory, yielding a control law that is independent of any parametrization of the configuration space. The proposed design...

This work lays the foundations for a rotorcraft design tool that includes the study of handling qualities during the conceptual design stage. Results from NDARC, a conceptual design software developed by NASA, are used to build a flight mechanics model augmented with a simplified flight control system. Handling qualities are evaluated for the resul...

This note contains comments on the paper Zhou (2015a), with specific reference to: the fact that the result in Theorem 3 of the paper is not new but actually goes back to the early 60s; a few comments on the actual scope and applicability of the method proposed in the paper; some corrections to the literature review provided in the paper.

It is well known in the literature on multirotor UAVs that the flight control performance is affected when operating close to the ground surface. While ground effect has been studied extensively for full scale helicopters, its study for multirotors has so far received limited attention. In particular, following an experimental investigation of stat...

In this paper the adaptive augmentation of the attitude control system for a multirotor Unmanned Aerial Vehicle (UAV) is considered. The proposed approach allows to seamlessly combine a linear robust controller with an adaptive one and to disable or enable the adaptive controller when needed, in order to take the advantages of both the controllers....

in this paper a comparison of fixed-point position control performance for a quadrotor and a quad-tilt-arm is presented and discussed, in terms of the problem of accurate distance holding of the UAV from a vertical surface in the presence of wind, which is a critical task for automatic monitoring of large civil infrastructures.

Recently developed results for direct adaptive control design in the context of uncertain systems in descriptor form are discussed and applied to a satellite attitude control problem. Thanks to descriptor model handling the methodology allows to address with convexity arguments uncertainties on the inertia matrix. The design of the adaptive law is...

In this paper the modeling and control law design for a quadcopter tiltorotor UAV are considered. The problem is developed in a geometric setting to obtain an intrinsic control law which achieves local exponential stability for trajectory tracking on SE(3). Starting from a multi-body system, a simplified model for control design is derived, which a...

There is significant evidence that the performance of quadrotors degrades when operating close to the ground surface. While many studies on ground effect for conventional helicopters are available, its study for multirotor platforms has so far received limited attention. In view of this, in this paper the problem of characterising the operation of...

In this paper a geometric approach to the trajectory tracking control of Unmanned Aerial Vehicles with thrust vectoring capabilities is proposed. The control design is suitable for aerial systems that allow to effectively decouple position and orientation tracking tasks. The control problem is developed within the framework of geometric control the...

In this paper, a multi-objective optimization-based methodology for rotorcraft attitude control law design is applied to a tilt-rotor case; the framework allows to enforce requirements of stability, performance, control action moderation, and safety. The structured H∞ approach is taken into account, and the optimization problem is stated as a mixed...

In this paper, the problem of tuning a cascade attitude control system of a variable-pitch quadrotor UAV is tackled, comparing two non-iterative data-driven approaches. The first method is the Virtual Reference Feedback Tuning (VRFT) while the second one is the Correlation based Tuning (CbT), both modified in order to tune both the inner and the ou...

Attitude determination for small scale UAVs such as quadrotors is considered, a number of existing solutions are compared and reviewed, and their performance is evaluated and discussed using data collected in flight.

In this paper, the problem of tuning a cascade attitude control system of a variable-pitch quadrotor UAV is tackled, comparing two non-iterative data-driven approaches. The first method is the Virtual Reference Feedback Tuning (VRFT) while the second one is the Correlation based Tuning (CbT), both modified in order to tune both the inner and the ou...

We give a comprehensive illustration of a new approach to rotorcraft noise abatement carried out in the framework of the Clean Sky collaborative project MANOEUVRES. This approach is based on technologies and tools for real-time, in-flight monitoring of the emitted noise. By means of a new cockpit instrumentation, the Pilot Acoustic Indicator (PAI),...

This work addresses the problem of designing robust multivariable controllers for the attenuation of the structural response of a helicopter, with reference to the Agusta A109 helicopter. The considered configuration consists of a set of piezoelectric actuators and accelerometers located on the fuselage of the helicopter. The robust harmonic contro...

This work addresses the identification of a control-oriented multivariable model of the structural response of a helicopter, with reference to the Agusta A109 helicopter. The estimated model will be used to design an active vibration control system to reduce the vibrations transmitted to the cabin by the main gearbox. The considered system consists...

This paper proposes a parameter-varying approach for the vibration control problem in rotorcraft applications. The proposed algorithm can be considered as a variant of Harmonic Control (HC), and can be placed beside existing adaptive versions used in the context of active controls design. In particular the novel approach accounts for the variation...

Linear Parameter Varying systems have state space representations that depend on time-varying parameters. This class of systems allows representing several types of systems such as non-linear systems, switching systems, multi-models, etc. This workshop aims at presenting some results in the field of LPV systems and applications, more and more studi...

An approach to rotor state feedback attitude control aimed at nominal stability, closed-loop performance, uncertainty robustness and tolerance to rotor state feedback faults is proposed. Structured í µí°» ∞ control based on a reduced linearized FlightLab model, an uncertainty description (changes in mass, altitude, center of mass position, speed) a...

The first task a spacecraft attitude control system must perform after separation from the launcher is to detumble the spacecraft, i.e., to bring it to a final condition with a sufficiently small angular momentum. Magnetic control has been used for decades to fulfill this task, typically using the socalled b-dot control law (in all its variants dev...

System identification is now a well established approach for the development of control-oriented models in the rotorcraft field (see, e.g., the survey paper Hamel and Kaletka (1997), the recent books Tischler and Remple (2006), Jategaonkar (2006) and the references therein). Though the application to full scale rotorcraft is by now fairly mature, l...

The problem of determining spacecraft attitude and angular rates from vector measurements is analysed; a number of approaches to the problem are compared and their relative merits discussed with particular reference to the problem of attitude and rate determination from magnetic field vector measurements.

In this paper the problem of active control of vibrations in helicopters is faced in a very general way. Precisely, we consider the case when the aircraft moves according to a possibly varying forward velocity. The problem is then more complex that the one encountered in hover or in forward flight. We tackle the general problem by means of an LPV (...

In this paper, a novel framework to address the problem of parametric estimation for continuous-time linear time-invariant dynamic systems is dealt with. The proposed methodology entails the design of suitable kernels of non-anticipative linear integral operators thus obtaining estimators showing, in the ideal case, "non-asymptotic" (i.e., "finite-...

Helicopter flight control law design including rotor state feedback (RSF) is considered. A mathematical model suitable for analysis and design of RSF control systems is obtained and a structured H ∞ approach to the problem is proposed, capable of guaranteeing stability and performance robustness. The framework also encompasses fault tolerance with...

The process of developing control-oriented mathematical models of physical systems is a complex task, which in general implies a careful combination of prior knowledge about the physics of the system under study and information coming from experimental data. The aim of this book is to present state-of-the-art methods and tools available within the...

The problem of rotorcraft system identification is considered and a novel, two-step technique is proposed, which combines the advantages of time-domain and frequencydomain methods. In the first step, the identification of a black-box model using a subspace model identification method is carried out, using a technique which can deal with data genera...

Linear fractional representations (LFRs) are a widely used model description formalism in modern control and system identification theory. Deriving such models from physical first principles is a non-trivial and often tedious and error-prone process, if carried out manually. Tools already exist to transform symbolic transfer functions and symbolic...

The development process for spacecraft control systems relies heavily on modelling and simulation tools for spacecraft dynamics. For this reason, there is a strong need for adequate design tools in order to cope efficiently with tight budget and time constraints for space missions. In this chapter the main issues related to the modelling and simula...

This comprehensive book covers the state-of-the-art in control-oriented modelling and identification techniques. With contributions from leading researchers in the subject, Control-oriented Modelling and Identification: Theory and practice covers the main methods and tools available to develop advanced mathematical models suitable for control syste...

Helicopter flight control law design including rotor state feedback is considered and an approach based on structured H∞ control, capable of guaranteeing stability and performance robustness, is proposed. The framework also encompasses fault tolerance with respect to failures of the rotor state sensors. Simulation results comparing the proposed app...

This paper deals with the problem of robust control design for the attitude dynamics of a variable-pitch quadrotor. The proposed approach is based on structured H-infinity synthesis applied to a black-box model of the quadrotor identified in dedicated bench-test experiments. An integrated procedure aimed at a fast and reliable deployment of the veh...

In this paper a novel approach to the design of active controllers aimed at reducing vibrations in helicopter applications is proposed. In particular the role of variability in the vibratory response of the helicopter (such as due to, e.g., varying flight condition and actuator nonlinearities) is taken into account in the synthesis of a robust para...

System identifi�cation is an established approach for the derivation of control-oriented dynamic models in the rotorcraft �field. While the application to full scale rotorcraft is by now fairly mature, less experience has been gathered on small-scale vehicles, such as, e.g., quadrotor UAVs. In this paper the problem of characterizing the attitude d...

Accurate dynamic modeling of helicopter aeromechanics is becoming increasingly important, as progressively stringent requirements are being imposed on rotorcraft control systems. System identification plays an important role as an effective approach to the problem of deriving or fine tuning mathematical models for purposes such as handling qualitie...

Active control techniques aimed at reducing helicopter vibrations have been extensively studied in the last few decades. The most studied control law is the so-called T- matrix algorithm; its implementation requires knowledge of the frequency response relating the control input to the output measurements at the disturbance frequency, which is very...

Higher Harmonic Control (HHC) has been considered for many years a valid approach for the design and the implementation of active rotor control laws aiming at the attenuation of helicopter vibration and noise and at the improvement of rotor performance. Its implementation requires knowledge of the frequency response relating the control input to th...

The process of developing control-oriented mathematical models of physical systems is a complex task, which in general implies a careful combination of prior knowledge about the physics of the system under study with information coming from experimental data. In this article the role of mathematical models in control system design and the problem o...

In this paper, a new identification technique is introduced to estimate a linear fractional representation of a linear parameter-varying (LPV) system from local experiments by using a dedicated non-smooth optimization procedure. More precisely, the developed approach consists in estimating the parameters of an LPV state-space model from local fully...

This paper deals with the problem of model identification in continuous-time using subspace techniques. More precisely, a recently presented continuous-time predictor-based subspace identification algorithm which relies on a system transformation using the Laguerre basis is considered and a bootstrap-based approach to the problem of quantifying the...

Anaerobic digestion includes numerous biological and physical-chemical processes, whose complexity and potential instability is well known. The Anaerobic Digestion Model by IWA (ADM1) is the state of the art model to describe anaerobic digestion, nevertheless simpler models, such as the AMOCO, had been proposed which are easier to identify and more...

Magnetic torquers are frequently adopted as primary actuators for the attitude control of small satellites in low Earth orbit. Such actuators generate a magnetic dipole which, in turn, leads to control torques thanks to the interaction with the magnetic field of the Earth. The design of attitude control laws based on magnetic torquers is a challeng...

In this study, the authors present an overview of closed-loop subspace identification methods found in the recent literature. Since a significant number of algorithms has appeared over the last decade, the authors highlight some of the key algorithms that can be shown to have a common origin in autoregressive modelling. Many of the algorithms found...

The guidance, navigation, and control problems for autonomous planetary entry descent and landing pose a number of interesting challenges. In this paper, the guidance and control problems for the descent phase are considered, and an approach based on the flatness property of the descent equations is proposed. A flat reformulation of the 2-D descent...

This work deals with a novel theoretical framework, based on the algebra of Volterra linear integral operators, aimed at designing non-asymptotic state observers for continuous-time SISO linear systems. We show that the design of observers with finite-time convergence of the estimation error can be carried out by appropriately choosing the kernels...

The current state-of-the-art in the fields of control-oriented LPV modelling and LPV system identification is surveyed and the potential synergies between the two research areas are highlighted and discussed. Indeed, a number of methods and tools for the development of LPV models from nonlinear systems and for the identification of black-box LPV mo...

The problem of rotorcraft system identification is considered and a novel, two step technique is proposed, which combines the advantages of time domain and frequency domain methods. In the first step, the identification of a black-box model using a subspace model identification method is carried out, using a technique which can deal with data gener...

The dynamics of a spacecraft equipped with magnetic actuators operating under a static attitude and rate feedback control law designed using averaging theory is considered and the asymptotic behavior of the closed-loop system as a function of the averaging scaling parameter is analysed numerically through continuation. We show that the (almost) glo...