Giulio Avanzini

The paper addresses the study and design of the autorotation maneuver for a remotely operated helicopter model, developing guidance and control algorithms to automatically track the designed maneuver in case of engine failure. The steady descent phase is investigated first, during which the rotor angular rate and helicopter velocity components are kept at constant values. During the final flare, rotor kinetic energy is exploited to decrease helicopter speed and sink rate before touchdown. If simple polynomial functions are adopted for velocity components during the flare as a function of altitude, the whole maneuver is identified on the basis of a reduced number of parameters, namely, the velocity components during the steady descent and the threshold altitude for starting the flare. An optimization algorithm allows for the selection of the set of maneuver design parameters that result in a minimum residual forward speed at touchdown. Guidance and control logic for the two phases are developed and tested in a number of simulations, proving that the controllers adequately track the designed trajectory, bringing the helicopter to the ground with minimum residual velocity. Robustness with respect to model errors and initial conditions is also demonstrated.

A tool for risk assessment after a catastrophic event during suborbital flight operations Giulio Avanzini, Giovanni Curiazio, Lorenzo Vampo [button link="ht

Due to the increase in short-range air mobility, tiltrotors are expected to get a market share in civil operations. Concomitantly, the need to reduce pollutants and noise emissions requires adopting innovative propulsion, but full-electric tiltrotors are not a feasible solution yet. A series-hybrid retrofit of the XV-15 is thus proposed. An emergency landing procedure is suggested for the critical case of engine failure when batteries are fully discharged. Aircraft rotors act as wind turbines, extracting power during the glide, and recharging the batteries for electrically powered conversion and landing. The propulsive retrofit of the XV-15 shows that current battery technology is not mature to make it a viable solution, and a complete vehicle re-design would be required, exploiting other side-effects of hybrid propulsion on aerodynamic performance. However, the improvement in the performance of the accumulators in the next decade can significantly modify this scenario. The proposed emergency landing procedure consists of a constant-speed descent after and before a constant altitude deceleration. The analysis shows that the optimal descent speed is between 55 and 60 m/s. The limited variation of rotor collective pitch and glide path angle should make performing the emergency sequence relatively easy for the pilot.

Electrical engines are becoming more common than thermal ones. Therefore, there is an increasing interest in the characterization of batteries and in measuring their state of charge, as an overestimation would cause the vehicle to run out of energy and an underestimation means that the vehicle is running in suboptimal conditions. This is of paramount importance for flying vehicles, as their endurance decreases with the increase in weight. This work aims at finding a novel empirical model for the discharge curve of an arbitrary number of battery pack cells, that uses as few tunable parameters as possible and hence is easy to adapt for every single battery pack needed by the operator. A suitable measurement setup for battery tests, which includes voltage and current sensors, has been developed and described. Tests are performed on both constant and variable power loads to investigate different real-world scenarios that are easy to reproduce. The main achievement of this novel model is indeed the ability to predict discharges at variable power based on a preliminary characterization performed at constant power. This leads to the possibility of rapidly tuning the model for each battery with promising accuracy. The results will show that the predicted discharged capacities of the model have a normalized error below 0.7%.

Active debris removal missions require an accurate planning for maximizing mission payout, by reaching the maximum number of potential orbiting targets in a given region of space. Such a problem is known to be computationally demanding and the present paper provides a technique for preliminary mission planning based on a novel evolutionary optimization algorithm, which identifies the best sequence of debris to be captured and/or deorbited. An original archipelago structure is adopted for improving algorithm capabilities to explore the search space. Several crossover and mutation operators and migration schemes are also tested in order to identify the best set of algorithm parameters for the considered class of optimization problems. The algorithm is numerically tested for a fictitious cloud of debris in the neighbourhood of Sun-synchronous orbit, including cases with multiple chasers.

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.

SUMMARY: This paper describes a modeling approach to compute the lumped parameter hydrodynamic derivative matrices of an underwater multi-hull vehicle. The vehicle, modeled as a multi-body underwater system and denoted as cluster, can be composed by heterogeneous bodies with known dynamic parameters, rigidly connected. The nonlinear dynamic equations of the cluster and its parameters are derived by means of a modular approach, based on the composition of single basic elements. The ultimate objective is to derive a mathematical description of the multi-hull system that captures its most significant dynamics allowing to design model-based motion controllers and navigation filters. The modular nature of the resulting model can be exploited, by example, when control reconfiguration is to be dealt with in the presence of (possibly multiple) failures. The numerical simulation of a hypothetical cluster is presented and discussed.