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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.

This paper presents an analytical framework for addressing the hovering performance of a battery–powered multirotor. The estimation of power required for flight is investigated and an analytical model is proposed to describe the rotor figure of merit as a function of few relevant blade parameters, without the need for ad hoc experiments. The model is derived after a discussion about the aerodynamics of rotating blades. The formulation in terms of Reynolds number is supported by an experimental campaign, performed on a set of commercial–of–the–shelf propellers optimized for small–scale multirotor applications. By imposing the balance between required and available power, the hovering time is predicted by an integral formulation developed for a constant–power battery discharge process. The best endurance condition is obtained in terms of optimum battery capacity and flight time. The methodology, applicable to the design phase of novel multirotor configurations, is finally validated by flight tests.

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.

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.

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.

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.

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.

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.

T HE interest in electrically-driven propeller airplanes has been steadily increasing over the last 15 years with applications ranging from small electric remotely piloted vehicles [1] up to large high-altitude/long-endurance aircraft [2], passing through general aviation size airplanes powered by means of hydrogen fuel cells [3]. The art and science of preliminary sizing of conventional aircraft has been the subject of many textbooks over the years [4,5] and, in this framework, reasonably accurate range and endurance prediction against design performance requirements plays quite obviously a crucial role. Unfortunately, the extension of the results valid for conventional configurations to electrically powered aircraft is not always straightforward. In a recent paper, [6] the equations for the evaluation of range and endurance of battery operated electrical aircraft are derived, keeping into account the effects of Peukert’s law on the battery discharge process [7]. Wilhelm Peukert performed tests on lead–acid batteries and discharging them with a constant current. His analysis proved that the discharge time Δt and the discharge current i satisfy the law [7]

In this paper a different approach to formation flight control is presented. In the proposed strategy, each aircraft does not refer to the preceding one or to the formation-leader, but keeps its position with respect to an imaginary point in the formation whose dynamics depend on all the aircraft positions. The strategy is based on the apparent natural behavior of some migrational birds, that during a migrational flight 'wait' for those gone astray giving up the original geometry. The formation controller is constituted by two control systems: a trajectory controller which provides tracking of a prescribed path, and position controller which permits formation geometry keeping. These control laws are mixed by a function dependent on position error.

This paper addresses the problem of the management of unmanned air vehicles flying in formation, in the presence of failures in the communication system or aircraft loss. The problem is solved representing the formation as an oriented graph, and a procedure based on shortest path theory provides the optimal solution for the information flow within the formation. When a failure occurs, the procedure runs again providing a sub-optimal solution, and formation geometry is changed according to pre-set reconfiguration maps. Formal definitions, such as the novel definition of Virtual Leader, and simulation results validate the methodology.