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This article presents an analytical framework for investigating the cruise performance of conventional helicopter configurations. Starting from the analysis of power required in straight-and-level flight, endurance and range performance of turbine- and battery-powered rotorcraft are considered, for which it is assumed that fuel consumption and constant-power battery discharge models are, respectively, made available. The original contributions of the article are represented by (a) a closed-form formulation for expected endurance and range for both classes of vehicles, where electrical helicopters have not been dealt with in previous studies and (b) the analytical derivation of an accurate estimate for best endurance and best range airspeeds as a function of relevant system parameters. The approach is validated by analyzing two reference helicopters, showing good physical insight and better accuracy with respect to other techniques available in the literature, for the identification of an energy-efficient cruise flight strategy.

The paper describes an analytical and experimental framework which investigates performance of electrically-driven ground vehicles powered by battery packs, with the objective of providing simple indications for preliminary sizing of rovers designed for mission on the surface of extraterrestrial bodies. For this class of missions, power is at a premium, and energy-efficient locomotion is clearly a critical issue. An analytical model for the estimate of cruise distance is derived and mobility performance is thus analyzed as a function of cruise speed, relevant vehicle parameters, soil mechanical properties, and atmospheric data. Results are then validated by numerical simulations and an experimental campaign for an Earth-based rover.

Spacecraft attitude stabilization based on active magnetic actuators represents a challenging problem, since the available control torque is constrained on a plane orthogonal to the direction of the local geomagnetic field, making the system instantaneously underactuated. A novel magnetic controller is proposed, driving a satellite flying on a Low-Earth-Orbit to three-axis stabilization on a prescribed attitude in the Nadir-pointing orbit frame. A proof of stability is provided for an idealized configuration (axisymmetric spacecraft with no disturbances). Robustness of the control technique against environmental disturbances, parameter uncertainties, corrupted measurements, and other control implementation issues is then demonstrated by numerical simulations, where the effect of magnetic residual dipoles is mitigated by online estimation.

This paper presents a trajectory control strategy for a multirotor aircraft carrying a suspended load. The load is modeled as a pendulum connected by a rigid link to the center of gravity of the vehicle. Starting from the dynamic equations describing the motion of the coupled vehicle slung-load systems, a nonlinear controller is proposed that simultaneously performs trajectory tracking and payload swing damping. Controller gains are chosen so that the system exhibits a two-time-scale behavior, with fast dynamics for the pendulum and slow dynamics for the positioning task. Under these conditions, the basic results of singular perturbation theory are evoked for both the proof of stability and the preliminary design of control gains. Results of numerical simulations are provided in order to assess the stability and performance of the considered approach.

This paper presents an analytical and experimental framework for investigating the performance of fixed-wing electrically-driven propeller aircraft. After the experimental derivation of a novel constant power discharge model for lithium-polymer (Li-Po) batteries, closed-form expressions for flight endurance and range are derived by equating power required in steady level flight with power supplied by the battery pack. Best endurance and best range airspeed are obtained. A methodology is also described to optimally size the battery capacity for a given set of battery and aircraft characteristics. The proposed approach is validated by application to a test case relative to a small-size unmanned aerial vehicle.

This paper describes the aerosol measurement setup and results obtained during the BEXUS18 (Balloon-borne Experiments for University Students) stratospheric balloon within the A5-Unibo (Advanced Atmospheric Aerosol Acquisition and Analysis) experiment performed on 10 October 2014 in northern Sweden (Kiruna). The experimental setup was designed and developed by the University of Bologna with the aim of collecting and analyzing vertical profiles of atmospheric ions and particles together with atmospheric parameters (temperature, relative humidity, and pressure) all along the stratospheric ascent of the BEXUS18 stratospheric balloon. Particle size distributions were measured with the MeteoModem Light Optical Aerosol Counter (LOAC) and air ion density was measured with a set of two commercial and portable ion counters. Though the experimental setup was based upon relatively low-cost and light-weight sensors, vertical profiles of all the parameters up to an altitude of about 27 km were successfully collected. The results obtained are useful for elucidating the relationships between aerosols and charged particles between ground level and the stratosphere, with great potential in collecting and adding useful information in this field, also in the stratosphere where such measurements are rare. In particular, the equipment detected coherent vertical profiles for particles and ions, with a particularly strong correlation between negative ions and fine particles, possibly resulting from proposed associations between cosmic rays and ions as previously suggested. In addition, the detection of charged aerosols in the stratosphere is in agreement with the results obtained by a previous flight and with simulations conducted with a stratospheric ion–aerosol model. However, further measurements under stratospheric balloon flights equipped with a similar setup are needed to reach general conclusions about such important issues.

The purpose of this paper is the design and the performance analysis of a control technique that allows simultaneous attitude control and angular momentum management for a Low Earth Orbit satellite equipped with a set of three magnetic actuators and three reaction wheels. A Proof of global asymptotic stability is derived for a control law driving a rigid spacecraft towards a prescribed, yet generic attitude fixed in the orbit frame. An analytical technique allowing for control gain selection is also proposed, which provides optimal convergence performance for the proposed controller, as demonstrated by means of Monte Carlo simulations. Robustness to external disturbances is finally evaluated within a realistic implementation scenario.

This paper addresses a methodology for autonomous motion planning of multirotor aircraft in obstructed environments. The control strategy allows the vehicle to online generate quasi-optimal trajectories with limited computational load while performing collision avoidance tasks. The problem is formulated in a model-predictive control architecture in which motion planning and trajectory tracking processes are solved separately. The first process is based on a spline path planning approach to generate smooth and safe trajectories. The second process elaborates trajectory inputs in terms of commanded thrust magnitude and desired attitude rates in order to steer the vehicle during the mission task. Results of both numerical simulations and, for the first time, an experimental validation are provided in order to assess the performance of the approach in the presence of external disturbances and unmodeled dynamics, provided adequate time horizon and update frequency are selected for the numerical optimization algorithm.

The aim of this paper is the analysis of simultaneous attitude control and momentum-wheel management of a spacecraft by means of magnetic actuators only. A proof of almost global asymptotic stability is derived for control laws that drive a rigid satellite toward attitude stabilization in the orbit frame when the momentum wheel is aligned with one of the principal axes of inertia. Performance of the proposed control laws is demonstrated by numerical simulations under actuator saturation. Robustness to external disturbances and model uncertainties is also evaluated.

An analytical and experimental framework addressing formation control of multirotor aircraft with collision avoidance capability is developed and presented. The proposed strategy applies to a formation of cooperating vehicles under the assumption of a broadcast transmission of position data. Starting from the point-mass dynamic model of the single aircraft in the formation, a set of constraints on the vehicles position is introduced and a nonlinear controller based on potential field method is proposed to simultaneously perform trajectory tracking, formation geometry keeping, and collision avoidance. Stability of the closed-loop control system is then proven by means of the Lyapunov method. Results of both numerical simulations and an experimental validation are provided in order to assess the proposed approach in the presence of external disturbances and unmodeled dynamics.

A sizing tool for the definition of the configuration of electrically powered multirotor platforms is developed, which accounts for a realistic battery discharge model. The tool is developed to provide the community with the possibility of deriving the best configuration for performing a given task, while accounting for specific constraints and performance requirements. An evolutionary algorithm is used for searching the design space and to identify feasible designs with optimal performance in terms of maximum hovering time on the target and payload weight fraction.

The paper proposes a novel approach for single-axis pointing of an underactuated spacecraft using only two reaction wheels (RWs), which is based on a simple yet effective wheel rate command. The control law can be used for aiming the line of sight of a sensor, a nozzle, or an antenna toward a target direction, or solar panels toward the sun, after failure of one wheel for a nonredundant control system hardware or, in the case of multiple failures, for redundant systems. The proposed control methodology represents the practical, dynamic implementation of a kinematic planning scheme proposed by the same authors, developed under the assumptions of zero overall angular momentum and triaxial inertia tensor. Under the zero angular momentum hypothesis, the control law also provides three-axis stabilization at zero angular speed. Only rest-to-rest maneuvers are thus dealt with, as a steady residual rotation rate around an arbitrary body-fixed axis cannot be attained in general unless the axis is the principal of inertia and aligned with the spin axis of one of the two active reaction wheels. The limited computational demand of the control law also makes it a practical solution in the case of small-size satellites, where the computational budget is severely limited by the available CPU processing capabilities. The effects of a nonzero residual angular momentum and control axes not aligned with the principal axes of inertia is also investigated, highlighting limitations on pointing precision and convergence performance.

In a recent work by the authors the concept of Fading Gaussian Deterministic filter was investigated. The algorithm is based on a set of equations derived from the minimization of a cost function where earlier data are progressively de-weighted by a fading factor. In such a way, the estimation was proved to be less prone to problem unknowns. A tuning procedure was proposed that allows the resulting globally best estimator to evaluate the covariance of an effective measurement noise and the true estimation error, without any a-priori assumption. In the present paper, a general formulation is derived where the observed system is influenced by a control input. Also, a proof is derived for the proposed tuning criterion, which is shown to provide, under certain assumptions, the fading factor that best dampens the modeling errors with respect to measurement noise. The validity of the proposed approach is investigated by means of both numerical simulations and an experimental campaign, where height estimation is performed by fusing information from MEMS accelerometers and a barometric altimeter.

The paper investigates the dynamic behavior of a spacecraft when a single magnetic torque-rod is used for achieving a pure spin condition by means of the so-called Y-dot control law. Global asymptotic convergence to a pure spin condition is proven on analytical grounds when the dipole moment is proportional to the rate of variation of the component of the magnetic field along the desired spin axis. Convergence of the spin axis towards the orbit normal is then explained by estimating the average magnetic control torque over one orbit. The validity of the analytical results, based on some simplifying assumptions and approximations, is finally investigated by means of numerical simulation for a fully non-linear attitude dynamic model, featuring a tilted dipole model for Earth׳s magnetic field. The analysis aims to support, in the framework of a sound mathematical basis, the development of effective control laws in realistic mission scenarios. Results are presented and discussed for relevant test cases.

This paper introduces a novel concept of visual-haptic display for situational awareness improvement for crowded and low altitude airspace situations. The visual augmentation display that constitutes of Virtual Fences delimiting no-fly zones, and a specific tri-dimensional highlight graphics that enhances visibility of other remotely piloted or autonomous agents, as well as conventional manned aircraft operating in the area is presented first. Then the Shared Control paradigm and the Haptic Force generation mechanism, based on a Proportional-Derivative-like controller applied to repulsive forces generated by the Virtual Fences and other UAVs are introduced and discussed. Simulations with 26 pilots were performed in a photo-realistic synthetic environment showing that the combined use of Visual-haptic feedback outperforms the Visual Display only in helping the pilot keeping a safe distance from no-fly zones and other vehicles.

The problem of aircraft formation dynamics and control is investigated from the viewpoint of formation architecture. Three different formation structures, leader-wingman, virtual leader and behavioural approaches are introduced. A comparative study is made using a unified approach through a suitable control law. The formation systems are analyzed on a quantitative basis and objective results are made available for the designer. The trade-off between system performance and complexity is indicated. A complete nonlinear simulation involving a flight-path change and a heading change manoeuvre is discussed. Results show the superiority of a behavioural approach to maintain close formations of vehicles.