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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 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 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.

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

A strategy for attitude path planning that performs single-axis pointing in the presence of obstacles along the angular path and constraints on admissible rotation axes is presented. The proposed kinematic solution is based on the identification of the crossing condition for a baseline single-step maneuver with an undesired set of pointing, seen as a conical obstacle along the attitude path. If crossing with the forbidden region occurs, an alternative two-step maneuver is selected, where both rotation axes are admissible and the cones spanned by the sensor boresight are tangent to the prohibited cone. Given the small number of admissible two-step maneuvers (eight at most), it is possible to select the shortest overall angular path with limited computational effort. The test case discussed demonstrates the effectiveness of the approach and provides further insight into the geometry of the cones.

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.

Extreme environments like active volcanoes exhibit many difficulties in being studied by in situ techniques. For example, during eruptions, summit areas are very hard to be accessed because of logistics problems and/or volcanic hazards. The use of remote sensing techniques in the last 20 years by satellite or airborne platforms has proven their capabilities in mapping and monitoring the evolution of volcanic activity. This approach has become increasingly important, as much interest is actually focused on understanding precursory signals to volcanic eruptions. In this work we verify the use of cutting-edge technology like unmanned flying system thermally equipped for volcanic applications. We present the results of a flight test performed by INGV in collaboration with the University of Bologna (Aerospace Division) by using a multi-rotor aircraft in a hexacopter configuration. The experiment was realized in radio controlled mode to overcome many regulation problems which, especially in Italy, limit the use of this system in autonomous mode. The overall goal was not only qualitative but also quantitative oriented. The system flew above an Italian mud volcano, named Le Salinelle, located on the lower South West flank of Mt. Etna volcano, which was chosen as representative site, providing not only a discrimination between hot and cold areas, but also the corresponding temperature values. The in-flight measurements have been cross-validated with contemporaneous in-situ acquisition of thermal data and from independent measurements of mud/water temperature.

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.

DOI: 10.2514/1.53074 In this paper, a control law that detumbles a spacecraft with magnetic actuators only is developed. A rigorous mathematical proof of global asymptotic convergence from arbitrary initial tumbling conditions to zero angular velocity in a time-varying magnetic field is derived. Furthermore, a simple criterion for determining a reasonable value of the control gain is developed. The selected gain results in a quasi-minimum time detumbling for different initialconditions,inthepresenceofmagneticcoilsaturation.Performanceoftheproposeddetumblingcontrollawis demonstrated by numerical simulations on a large set of test cases using a Monte Carlo approach.

A tuning algorithm is presented allowing the optimal estimation of an unknown deterministic state vector observed through noisy measurements. The estimation technique named the fading Gaussian deterministic filter is based on a KF-like set of recursive equations and is considered to be optimal because the gain matrix is an algebraic consequence of a formal minimization of a cost function, with no other assumption. This fading behavior allows the algorithm to work despite other unknowns in the problem that are not measurement noise. A numerical example was provided where angular rate estimation is performed from magnetometer readings of a tumbling satellite. Results were obtained by searching offline for the best configuration over a filter bank, sharing the same structure and simulated measurements, but using different fading factors. The tuning procedure proved to work satisfactorily under large. modeling errors, with remarkable performance in the estimation of the angular rates from noisy readings. In fact, in the tuned condition only, the algorithm was able to estimate both the actual covariance of the measurement noise and the true error covariance related to the state vector estimate with satisfactory accuracy.

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.