Emanuele L. de Angelis

Acquisition of a Desired Pure-Spin Condition for a Magnetically Actuated Spacecraft

b = geomagnetic-field vector expressed in FB e1, e2, e3 = spacecraft principal axes of inertia FB = body-fixed frame FI = inertially fixed frame FO = local–vertical/local–horizontal orbit frame h = angular momentum vector i = orbit inclination I3 = 3 × 3 identity matrix J diag J1; J2; J3 = spacecraft inertia matrix kh = control gain M = external torque acting on the spacecraft m = magnetic dipole moment vector rc = orbit radius Torb = orbit period TBI = coordinate transformation matrix between FI and FB TBO = coordinate transformation matrix between FO and FB tF = convergence time to the desired spinning motion α = angle between ei and b Γ = plane containing ei and b δ = elevation of e with respect to Γ e = e1; e2; e3 T , error between desired and actual angular momentum vectors χ = angle between the projection of e on Γ and ei Ω = orbit rate ω = ω1;ω2;ω3 T , absolute angular velocity vector Subscripts

Spacecraft Attitude Control Using Magnetic and Mechanical Actuation

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.