Robust Formation Flying Tracking Control Using Active Disturbance Rejection Controller
by
Zhang Chenguang
Department of Precision Instruments and Mechanology, Tsinghua University, Beijing, China
Coauthors: Chen Darong

Formation tracking control drives formation flying spacecrafts to follow desired relative trajectories within an acceptable level of accuracy under model uncertainty and external disturbances. In this paper, a novel control strategy, the active disturbance rejection control (ADRC), is applied to design robust formation tracking control law. The full nonlinear dynamics describing the relative motion of spacecraft formation flying are used.

The basic idea of ADRC is to use an extended states observer (ESO) to estimate the “total disturbance” of the exact dynamics of the relative motion. The “total disturbance” lumps the “internal disturbance” and the “external disturbance”. The former is composed of nonlinear nature of the dynamics, the channel coupling effects, the dynamic uncertainties. while the latter includes the unknown disturbances from environment, such as effects of earth oblateness, atmospheric drag, and solar radiation. Unlike traditional observers (such as Luenberger Observer or High-gain Observers), ESO does not depend on the knowledge of the plant dynamics. Only measurable output and input of the plant are needed as the input to the ESO. By treating the “total disturbance” as an extended state and selecting suitable construction and parameters, ESO can be constructed to ensure the tracking errors to be zero.

After compensating in real time the actual total disturbance in each channel, dynamic feedback linearization and decoupling control is realized and the whole system is reduced to three double integrator, which in turn are controlled by nonlinear states feedback.

Simulation results are included to demonstrate the control law performance.

Date received: March 28, 2008