Magnetic desaturation of a momentum bias system

Abstract

A simple observer and controller has been formulated for a low bandwidth yaw attitude control loop on a synchronous orbit momentum bias spacecraft. Operation of the system is entirely autonomous, with the only external reference required being a measurement of the spacecraft roll attitude. Low-level torque actuation is provided by a single magnetic coil that is mounted in the spacecraft body at an arbitrary orientation in the roll/yaw plane. This control system design provides much better pointing accuracy and rate stability for a given bias momentum than previous techniques. Simulated performance during a magnetic storm is presented for a Vee-Wheel momentum bias configuration. The properties of the geomagnetic field at synchronous altitude that are pertinent to spacecraft attitude control system design are described in the Appendix.

Comparative stability analysis and performance of magnetic controllers for bias momentum satellites

“…(13), and the following characteristic equation then ensues: s 4 + a\s 3 + a 2 s 2 + a 3 s + a^ = 0 (14) with s as the Laplace variable corresponding to the orbit angle tu 0 f • The explicit expressions of the polynomial coefficients can be derived from the general a presented later [Eqs. (21)], but for now we note that, in view of the relationship (7) between k n and k p , the stability analysis leads to the condition k n > 0 for h s < 0, and to the following more predominant condition:…”

“…Moreover, ordinarily, the roll/yaw inertial angular rate components o)\ and &> 3 of the spacecraft are related to the Euler angles and rates in the following but when nutation damping is predominant, the inertial angular rates are essentially the Euler rates (that is, CD\ & MI and a) 3 where s is the Laplace variable associated with time r, not a) 0 t as before in Eq. (14). Let the uncontrolled (k n = 0) root of Eq.…”

Pole-Placement Technique for Magnetic Momentum Removal of Earth-Pointing Spacecraft

“…(27a) and (27c) together. To specify ® x and ® z , we impose the condition 16 With ® x D ® z , the closed-loop poles of the roll/yaw momentum removal dynamics are found at ¡® x § j ! 0 (see Fig.…”

“…Even the exception, Ref. 16, is limited to only one electromagnet in the geosynchronousorbit (roll/yaw) plane.…”

“…The use of linear quadratic regulator theory to relate weighting matrices with the closed-loop poles, as in Refs. 3-6, is not required, for a straightforward determination of closed-loop eigenvalues, and their relationship with steady-state momentum amplitudes about each of the three axes, after Lebsock, 16 seems adequate and elegant at once. The special cases of low-and high-inclination orbits are considered.…”