Guidance and control for defense systems against ballistic threats

A defense system against ballistic threat is a very complex system from the engineering point of view. It involves different kinds of subsystems and, at the same time, it presents very strict requirements. Technology evolution drives the need of constantly upgrading system’s capabilities. The guidance and control fields are two of the areas with the best progress possibilities. This thesis deals with the guidance and control problems involved in a defense system against ballistic threats. This study was undertaken by analyzing the mission of an intercontinental ballistic missile. Trajectory reconstruction from radar and satellite measurements was carried out with an estimation algorithm for nonlinear systems. Knowing the trajectory is a prerequisite for intercepting the ballistic missile. Interception takes place thanks to a dedicated tactical missile. The guidance and control of this missile were also studied in this work. Particular attention was paid on the estimation of engagement’s variables inside the homing loop. Interceptor missiles are usually equipped with a seeker that provides the angle under which the interceptor sees its target. This single measurement does not guarantee the observability of the variables required by advanced guidance laws such as APN, OGL, or differential games-based laws. A new guidance strategy was proposed, that solves the bad observability problems and returns satisfactory engagement performances. The thesis is concluded by a study of the interceptor most suitable aerodynamic configuration in order to implement the proposed strategy, and by the relative autopilot design. The autopilot implements the lateral acceleration commands from the guidance system. The design was carried out with linear control techniques, considering requirements on the rising time, actuators maximum effort, and response to a bang-bang guidance command. The analysis of the proposed solutions was carried on by means of numerical simulations, developed for each single case-study

Switching multiple model filter for boost-phase missile tracking

This paper introduces a filter for tracking a ballistic missile during its boost phase. This filter includes a new switching algorithm and a modified interacting multiple model unscented filter (IMMUF), where the Markov transition matrix is time variable. Position, velocity, and all unknown parameters of a medium-range ballistic missile model are reconstructed. Simulations demonstrate that the new filter is able to consistently estimate a missile's trajectory and all unknown parameters and to outperform the previous forms of the IMMUF

A Stochastic Characterization of the Capture Zone in Pursuit-Evasion Games

Pursuit-evasion games are used to define guidance strategies for multi-agent planning problems. Although optimal strategies exist for deterministic scenarios, in the case when information about the opponent players is imperfect, it is important to evaluate the effect of uncertainties on the estimated variables. This paper proposes a method to characterize the game space of a pursuit-evasion game under a stochastic perspective. The Mahalanobis distance is used as a metric to determine the levels of confidence in the estimation of the Zero Effort Miss across the capture zone. This information can be used to gain an insight into the guidance strategy. A simulation is carried out to provide numerical results

Peter Dvorský. Sottotitolaggio in italiano dallo slovacco

Su proposta del Professore Ivan Šuša ho preso parte al progetto di sottotitolazione del documentario “Peter Dvorský”. Al progetto hanno partecipato anche la Professoressa di slovacco presso l’Università “La Sapienza” di Roma, Zuzana Nemčíková, e il suo studente Murillo Misacci Borges, i quali si sono occupati principalmente dei sottotitoli della seconda metà del film e con cui abbiamo svolto un lavoro comune di revisione del prodotto finale. Il film con i sottotitoli italiani è stato infine presentato a Roma il 22.06.2023 presso l’Ambasciata della Repubblica Slovacca a Roma. L’obiettivo di questa tesi, divisa in tre capitoli, è quello di affrontare il tema della traduzione audiovisiva con un approccio sintetico-analitico, sintetizzando i punti salienti della storia e dello sviluppo della AVT, soprattutto in Italia e Slovacchia, riassumendo alcune delle strategie e degli strumenti usati nella creazione dei sottotitoli e infine analizzando la proposta di traduzione proposta

Results of the attitude reconstruction for the UniSat-6 microsatellite using in-orbit data

UniSat-6 is a civilian microsatellite that was launched in orbit on the 19th of June, 2014. Its main mission consisted in the in-orbit release of a number of on-board carried Cubesats and in the transmission to the UniSat-6 ground station of telemetry data and images from an on-board mounted camera. The spacecraft is equipped with a passive magnetic attitude control system. Gyros and magnetometers provide the information about the attitude of the spacecraft. The importance of reconstructing the attitude motion of UniSat-6 lies in the dual possibility, for future missions, of:controlling the direction of ejection of the on-board carried satelliteshaving an accurate pointing for remote sensing operation.The reconstruction of the attitude motion of UniSat-6 is based on the data of the on-board Commercial Off The Shelf (COTS) gyros and magnetometers, downloaded at the passages over the ground station in Roma, Italy. At ground, these data have been processed with the UnScented QUaternion Estimator (USQUE) algorithm. This estimator is an adaptation of the Unscented Filter to the problem of spacecraft attitude estimation. The USQUE is based on a dual attitude representation, which involves both quaternions and Generalized Rodrigues Parameters. In this work, the propagation phase of the algorithm contains only a kinematic model of the motion of the spacecraft. This paper presents the results of the reconstruction of the UniSat-6 attitude using on-board measurements. The results show that the spacecraft effectively stabilized its attitude motion thanks to the on-board magnetic devices

CubeSat constellations for disaster management in remote areas

In recent years, CubeSats have considerably extended their range of possible applications, from a low cost means to train students and young researchers in space related activities up to possible complementary solutions to larger missions. Increasingly popular, whereas CubeSats are still not a solution for all types of missions, they offer the possibility of performing ambitious scientific experiments. Especially worth considering is the possibility of performing Distributed Space Missions, in which CubeSat systems can be used to increase observation sampling rates and resolutions, as well as to perform tasks that a single satellite is unable to handle. The cost of access to space for traditional Earth Observation (EO) missions is still quite high. Efficient architecture design would allow reducing mission costs by employing CubeSat systems, while maintaining a level of performance that, for some applications, could be close to that provided by larger platforms, and decreasing the time needed to design and deploy a fully functional constellation. For these reasons many countries, including developing nations, agencies and organizations are looking to CubeSat platforms to access space cheaply with, potentially, tens of remote sensing satellites. During disaster management, real-time, fast and continuous information broadcast is a fundamental requirement. In this sense, a constellation of small satellites can considerably decrease the revisit time (defined as the time elapsed between two consecutive observations of the same point on Earth by a satellite) over remote areas, by increasing the number of spacecraft properly distributed in orbit. This allows collecting as much data as possible for the use by Disaster Management Centers. This paper describes the characteristics of a constellation of CubeSats built to enable access over the most remote regions of Brazil, supporting an integrated system for mitigating environmental disasters in an attempt to prevent the catastrophic effects of natural events such as heavy rains that cause flooding. In particular, the paper defines the number of CubeSats and the orbital planes required to minimize the revisit time, depending on the application that is the mission objective. Each CubeSat is equipped with the suitable payloads and possesses the autonomy and pointing capabilities needed to meet the mission requirements. Thanks to the orbital features of the constellation, this service could be exploited by other tropical countries. Coverage of other areas of the Earth might be provided by adjusting the number and in-orbit distribution of the spacecraft

Modeling a Satellite Mockup’s Angular Motion on an Air Bearing with Uniaxial Magnetic Attitude Control

© 2020, Pleiades Publishing, Ltd. Abstract: The angular motion of a mockup of a satellite’s attitude control system on an air bearing is considered. The general purpose of the work is to verify the one-axis magnetic attitude control algorithm. This control is designed to maintain the satellite’s solar panels attitude towards the Sun. Specific mockup motion patterns are found. These patterns allow comparing the ground-based control performance results and its expected inflight operation. Asymptotically stable precession and near planar motion are outlined. Mathematical modelling is performed for these patterns. Their applicability for the laboratory experiments is shown

A Decision Support System for the safety evaluation of urban pedestrian crossings

This paper proposes an innovative methodology, based on a Decision Support Systems, for the safety evaluation of pedestrian crossings without traffic lights in urban neighborhood areas. It provides an on-site inspection performed using ad-hoc data check lists, and it allows to assign a safety rate to the pedestrian crossing, in order to define a priority list of interventions and to suggest which features need to be improved. This new approach can be useful and easy to use for public administration managers and local governances, when they need to allocate limited financial resources to several pedestrian crossings. It has been applied to 10 pedestrian crossings on two roads in the urban area of Bologna and the resulted ranking list has been used by the Municipality of Bologna in its Urban Road Safety Plan 2016-201

How Do University Student Cyclists Ride? The Case of University of Bologna

In a general urban planning context, in which sustainable active mobility progressively takes up increasing attention, studies of cyclists’ attitudes and behaviors represent a relevant step to help any enhancing measures for urban cycling. Among different categories, university student cyclists represent a still unidentified class, despite the relevant impacts in terms of mass and variability of attitudes in urban areas. The novelty of this paper is to propose an innovative overview on the specific category of university student cyclists. The integrated methodology, based on direct observation through GPS detection, GIS processing, and qualitative survey, permits the evaluation of some interesting issues related to students’ propensity to cycling and their mobility patterns. The approach finds relevance in speed, frequency of movements, routing, and related infrastructure preferences. The methodology has been applied to a sample of more than 300 students of the University of Bologna who were allowed an original university-designed bicycle from February 2021 to June 2021. The analysis was applied in the Bologna urban area and allowed the evaluation of students’ preferences of using existing cycle paths, when available, the limited relevance of speed factors, the main distribution of commuter journeys concentrated in the main avenues directed to city center, and other behaviors

Tabletop Testbed for Attitude Determination and Control of Nanosatellites

To simulate the conditions of the space environment at ground, the Laboratory of Application and Innovation in Aerospace Science (LAICA) of the University of Brasília (UnB) is developing a dedicated testbed to reproducing nanosatellite attitude motion. The testbed is composed of an air-bearing table and a Helmholtz cage. The air-bearing table is a spacecraft simulator that can simulate frictionless conditions with three rotational degrees of freedom. Balancing the simulator is essential in order to make the gravitational torque negligible. The testbed is also equipped with a Helmholtz cage to recreate the Earth's magnetic field conditions that spacecrafts encounter in orbit. This paper presents the design and realization of this low-cost testbed. A simple and efficient automated balancing algorithm based on the least-squares method (LSM) is proposed and validated by experiments. The performance of the proposed simulator is evaluated and compared with previous works