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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.

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.

The paper presents an analytical framework for addressing the hovering time prediction of rotary-wing aircraft, with a particular focus on multi-rotor platforms. By imposing the balance between required and available power, the endurance expression is derived as a function of airframe features, rotor parameters, and battery capacity. The best endurance condition is also obtained in terms of optimum capacity and hovering time, by means of two approximate closed-form solutions. The proposed methodology was validated by means of numerical simulation and flight testing. Results show the effectiveness of the proposed approach.

In underactuated conditions, satellite attitude actuators can deliver a control torque with two components only. The paper develops a general solution for the problem of attitude maneuver planning for underactuated spacecraft by means of a sequence of N admissible rotations, where a rotation is considered to be admissible if it takes place around an axis which lies on the plane where the actuator system can deliver a control torque. An exact solution for the sequence of two feasible rotations that provides a desired reorientation is derived, where the minimum angular- path sequence can also be identified analytically. The optimal sequence for a higher number of steps is obtained by means of a numerical optimization procedure. The features of the optimal sequences for increasing values of N are investigated in order to obtain a better understanding of their characteristics.

This paper shows an ambitious methodology of autonomous navigation for multirotor UAVs in obstructed environments. The following strategy was formulated to ensure to ultirotor vehicles the capability to produce autonomously quasi-optimal and safe trajectories, although generally they have at their disposal limited computational resources on board. The problem is formuled in a model predictive control (MPC) architecture in which motion planning and trajectory tracking processes are solved separately like they were stored in two different devices. The first one uses a spline-based motion planning approach to generate smooth and safe trajectories. At this step also a multicopter’s simplified dynamic model and environment information are taken in account. The second one uses trajectory inputs (total thrust and attitude angle rates) to steer the multicopter during the flight. Both adequate time horizon and update frequency are chosen in order to take in account disturbances and dynamics model mismatch. The following methodology will be validated with simulations and future work include experimental tests in outdoor environement. ispartof: pages:19-24 ispartof: Proceedings of the 4th International Workshop on Research, Education and Development on Unmanned Aerial Systems pages:19-24 ispartof: International Workshop on Research, Education and Development on Unmanned Aerial Systems location:Linköping, Sweden date:3 Oct - 5 Oct 2017 status: published

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.

Attitude regulation proves to be a challenging problem, when magnetic actuators alone are used as attitude effectors, since they do not provide three independent control torque components at each time instant. In this paper a rigorous proof of global exponential stability is derived for a magnetic control law that leads the satellite to a desired spin condition around a principal axis of inertia, pointing the spin axis toward a prescribed direction in the inertial frame. The technique is demonstrated by means of numerical simulation of a few example maneuvers. An extensive Monte Carlo simulation is performed for random initial conditions, in order to investigate the effect of changes in control law gains.

Unmanned platforms with a conventional fixed wing configuration can be designed according to well assessed aircraft sizing techniques. Conversely, the design of multi-rotor vehicles is still based mainly on scale-model enthusiastic experience. At present there has been a limited effort by the community in developing a systematic approach for sizing this unconventional class of flying vehicles. This paper proposes a revised version of a classical aircraft sizing methodology, based on statistical data available in the literature, with the objective of preliminary sizing an electric multi-rotor configuration, taking into account mission profile and a few performance requirements.

Multi-rotor autonomous aerial vehicles have been proposed for several missions where the capability of controlled flight in small areas is required. Unfortunately, small-size electrically powered rotary wings UAVs have usually very short endurance, because of inherent limitation in battery energy density and constraints on maximum weight of the battery pack. At the same time, maneuverability can be improved by a variation of rotor thrust orientation. This paper presents a novel quad—rotor configuration where the use of a combustion engine and variable pitch propeller will allow for increasing endurance performance, whereas tilting of rotor disks improves maneuverability. A preliminary design of simple control laws is also discussed for this particular configuration, tested on a few basic maneuvers.

An inverse simulation algorithm is applied to the determination of the control laws for tracking desired maneuvers by means of an unconventional quad-rotor configuration. This novel configuration features four rotors that are allowed to tilt around the axis of the support, thus changing the thrust vector direction in order to achieve unprecedented maneuvering capabilities. The novel configuration is compared with a conventional quad-rotor, where control moments are generated by variations of rotor rotation rates. A 90 deg roll maneuver in forward flight is also presented, to highlight the increased maneuvering capabilities of the new configuration.

This paper presents an analytical treatment of dynamic soaring, a behaviour that certain sea birds use to extract energy from wind gradient. Theoretical modeling and results of numerical simulations, based on a two-degrees-of-freedom point mass model, are presented.

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 Behavioral approaches are introduced. A comparative study is made using an unified approach through a suitable control law based on the dynamic inversion approach.

Two aspects of formation flight are addressed in this paper: dynamic modeling and formation control. In formation flight aircraft dynamics are coupled by aerodynamic effects due to the vortices leaving the lifting surfaces, such as changes in lift and drag forces and lateral/directional effects that do not appear in a steady-level ‘isolated’ flight. These aerodynamic effects are properly modeled with a three dimensional code based on a Distributed Horse-Shoe Technique. A formation controller allowing both trajectory tracking and formation geometry keeping is then designed. It is shown that the designed controller yields satisfactory performance in a two-aircraft formation.

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.