Drag-Free Control of the GOCE Satellite: Noise and Observer Design

Abstract

This brief concerns model and noise design relevant to drag-free and attitude control of the European satellite gravity field and steady-state ocean circulation explorer (GOCE) under different control modes. As the model must include accurate dynamics of disturbance and measurement drifts to be rejected/estimated, noise design aims to select, and to mark with the Boolean variables of the control modes, the necessary and sufficient feedback channels (noise estimator) connecting model error to noise, which are the paths through which model state variables can be updated in real-time. Noise design is applied to a generic model encompassing position and attitude control, fed by position, rate, attitude, and acceleration sensors. The resulting closed-loop becomes a state predictor, providing controllable and disturbance states to drag-free and attitude control law, switching smoothly from mode to mode. Noise estimator gains are tuned to robust performance and stability by properly assigning closed-loop eigenvalues. Tuning details and simulated results illustrating the different modes are provided.

Embedded Model Control: Design separation under uncertainty

“…According to [11] and [12], the model q e is associated to the former set and g e to the latter one. In this way the uncertainty estimator is decoupled, and may exploit different sampling rates.…”

“…The key fact is that y only depends on the control law design, whereas ˆy e only depends on the embedded model and on the noise estimator. Noise layout [11] and estimator must be designed uncertainty-based.…”

On all-propulsion design of integrated orbit and attitude control for inner-formation gravity field measurement satellite

“…3) The Earth's magnetic field which couples with the satellite magnetic dipole moment, yielding the magnetic torque [18,19]. Atmospheric drag and aerodynamic torque are the most significant among them.…”

“…[12,17,18]. The orbit drag compensation thruster (OTA) is arranged in the opposite direction of b x -axis of the body frame and thus only produces thrust aligned with b x -axis.…”

The four-tank control problem: Comparison of two disturbance rejection control solutions

“…Since the filter feedback is static, closedloop stability demands all the state variables, also the noise-free ones, to be excited by a feedback component. EMC follows a different way: noise layout must be designed as in [30] and [31] according to the desired uncertainty class; embedded model should not be corrupted by parasitic noise. Since noise plays the role of the uncertainty input, this way offers flexibility and efficiency in the real-time uncertainty estimation and discrimination.…”