Fabio Curti

Lyapunov-Based Thrusters' Selection for Spacecraft Control: Analysis and Experimentation

This paper introduces a method for spacecraft rotation and translation control by on-off thrusters with guaranteed Lyapunov-stable tracking of linear dynamic models. In particular, the proposed control method switches on, at each time step, only those thrusters needed to maintain stability. Furthermore, the strategy allocates the configuration so that the minimum number of actuators is used. One of the benefits of the proposed method is that it substitutes both the thruster mapping and the pulse modulation algorithms typically used for real-time allocation of the firing thrusters and for determining the duration of the firing. The proposed approach reduces the computational burden of the onboard computer versus the use of classical thruster mapping algorithms, which typically involve iterative matrix operations. The paper presents analytical demonstrations, numerical simulations on a six-degree-of-freedom spacecraft, and experimental tests on a hardware-in-the-loop three-degree-of-freedom spacecraft simulator floating over air pads on a flat floor. The method proves to be effective and easy to implement in real time.

Particle Swarm Optimization for Time-Optimal Spacecraft Reorientation with Keep-Out Cones

This paper deals with the problem of spacecraft time-optimal reorientation maneuvers under boundaries and path constraints. The minimum time solution with keep-out constraints is proposed using the particle swarm optimization technique. A novel method based on the evolution of the kinematics and the successive obtainment of the control law is presented and named as inverse dynamics particle swarm optimization. It is established that the computation of the minimum time maneuver with the proposed technique leads to near-optimal solutions, which fully satisfy all the boundaries and path constraints.

Spacecraft Rendezvous by Differential Drag Under Uncertainties

At low Earth orbits, differentials in the drag forces between spacecraft can be used for controlling their relative motion in the orbital plane. Current methods for determining the drag force may result in errors due to inaccuracies in the density models and drag coefficients. In this work, a methodology for relative maneuvering of spacecraft based on differential drag, accounting for uncertainties in the drag model, is proposed. A dynamical model composed of the mean semimajor axis and the argument of latitude is used for describing long-range maneuvers. For this model, a linear quadratic regulator is implemented, accounting for the uncertainties in the drag force. The actuation is the pitch angle of the satellites, considering saturation. The control scheme guarantees asymptotic stability of the system up to a certain magnitude of the state vector, which is determined by the uncertainties. Numerical simulations show that the method exhibits consistent robustness to accomplish the maneuvers, even in the ...

Guidance Navigation and Control for Autonomous Multiple Spacecraft Assembly: Analysis and Experimentation

This work introduces theoretical developments and experimental verification for Guidance, Navigation, and Control of autonomous multiple spacecraft assembly. We here address the in-plane orbital assembly case, where two translational and one rotational degrees of freedom are considered. Each spacecraft involved in the assembly is both chaser and target at the same time. The guidance and control strategies are LQR-based, designed to take into account the evolving shape and mass properties of the assembling spacecraft. Each spacecraft runs symmetric algorithms. The relative navigation is based on augmenting the targets state vector by introducing, as extra state components, the targets control inputs. By using the proposed navigation method, a chaser spacecraft can estimate the relative position, the attitude and the control inputs of a target spacecraft, flying in its proximity. The proposed approaches are successfully validated via hardware-in-the-loop experimentation, using four autonomous three-degree-of-freedom robotic spacecraft simulators, floating on a flat floor.

Minimum-Time Reconfiguration Maneuvers of Satellite Formations Using Perturbation Forces

A novel approach for minimum-time reconfiguration of satellite formations is proposed considering the perturbation forces as control variables. Planning appropriate attitude maneuvers for each satellite, the atmospheric drag and of the solar radiation pressure are properly controlled, and the formation is given the appropriate inputs to achieve the imposed reconfiguration. Limits and advantages of the presented maneuvers are examined considering low Earth orbits, medium Earth orbits, and geostationary orbits. The recent inverse dynamics particle swarm optimization is involved; the integration of the attitude dynamics is avoided, thus reducing the computational effort, and satisfied attitude constraints at the initial and final time instants are guaranteed. B-spline curves approximate the attitude kinematics, variable time mesh points are introduced, and adaptive decreasing tolerances are considered for the imposed constraints. The evolution of the configuration is simulated with a high-fidelity orbital si...

ADAHELI+: exploring the fast, dynamic Sun in the x-ray, optical, and near-infrared

Abstract. Advanced Astronomy for Heliophysics Plus (ADAHELI+) is a project concept for a small solar and space weather mission with a budget compatible with an European Space Agency (ESA) S-class mission, including launch, and a fast development cycle. ADAHELI+ was submitted to the European Space Agency by a European-wide consortium of solar physics research institutes in response to the “Call for a small mission opportunity for a launch in 2017,” of March 9, 2012. The ADAHELI+ project builds on the heritage of the former ADAHELI mission, which had successfully completed its phase-A study under the Italian Space Agency 2007 Small Mission Programme, thus proving the soundness and feasibility of its innovative low-budget design. ADAHELI+ is a solar space mission with two main instruments: ISODY+: an imager, based on Fabry–Pérot interferometers, whose design is optimized to the acquisition of highest cadence, long-duration, multiline spectropolarimetric images in the visible/near-infrared region of the solar spectrum. XSPO: an x-ray polarimeter for solar flares in x-rays with energies in the 15 to 35 keV range. ADAHELI+ is capable of performing observations that cannot be addressed by other currently planned solar space missions, due to their limited telemetry, or by ground-based facilities, due to the problematic effect of the terrestrial atmosphere.

Spacecraft Proximity Navigation and Autonomous Assembly based on Augmented State Estimation: Analysis and Experiments

AIAA Guidance, Navigation, and Control Conference 2 - 5 August 2010, Toronto, Ontario Canada

Optimal Continuous Maneuvers for Satellite Formation Reconfiguration in J2-perturbed Orbits

This paper focuses on the fuel-minimum in-plane spacecraft reconfiguration maneuver in J2 perturbed near-circular orbits. The reconfiguration problem is posed as a nonlinear optimal control problem and it is solved by two techniques, namely the Mixed-integer Linear Programming and the Particle Swarm Optimization. The control is assumed to be a piecewise constant function and a linear dynamics model based on relative orbit element parameterization is used to derive the fueloptimal solution. Simulation results demonstrate the efficiency of both proposed methods, pointing out the performance in terms of computing time and accuracy.