Abstract
The problems of autonomous digital control of the information satellites and space robots during their initial transition to a tracking mode, namely in the initial orientation modes, are considered. Autonomous angular guidance and modularly limited vector digital control using a vector of the modified Rodrigues parameters are applying to bring the spacecraft’s orientation from completely arbitrary to the required one. The developed methods, algorithms and simulation results for a mini-satellite in a sun-synchronous orbit are presented.
Highlights
After separating any spacecraft from a launch vehicle, the spacecraft (SC) begins to turn somersaults – to rotate with the angular velocity vector ω of arbitrary direction in its body reference frame (BRF) Oxyz
If the SC is modeled as a rigid body, indicated problems of its spatial angular motion are studied in theoretical mechanics [Aleksandrov and Tikhonov, 2018] and physics [Materassi and Morrison, 2018] as well as in mathematical control theory [Smirnov, 1981]
We study the SC nonlinear control problems in the following initial orientation modes (IOMs): (i) the SC calm down in the inertial reference frame (IRF) at the angular rate sensors (ARSs) cluster’s signals by the magnetic drive (MD) digital control while the angular velocity vector module ω ≡ | ω| > ω1∗ at the specified value ω1∗; (ii) initialization of reaction wheels (RWs) cluster, switching on it into the SC control loop and the SC bringing to the required orientation in the orbital reference frame (ORF) when the strapdown inertial navigation system (SINS) signals are used; (iii) the SC angular stabilization in the ORF by autonomous digital control of the RW cluster with its unloading from the accumulated angular momentum (AM) using MD [Somov et al, 2018]
Summary
After separating any spacecraft (an information satellite [Testoyedov et al, 2017], a space robot [Somov et al, 2019] etc.) from a launch vehicle, the spacecraft (SC) begins to turn somersaults – to rotate with the angular velocity vector ω of arbitrary direction in its body reference frame (BRF) Oxyz. The simplest task is the initial orientation modes (IOMs) of the SC attitude control system (ACS) when the SC orientation is bringed to a given position in the orbital reference frame (ORF) Oxoyozo. We study the SC nonlinear control problems in the following IOMs: (i) the SC calm down in the inertial reference frame (IRF) at the ARS cluster’s signals by the MD digital control while the angular velocity vector module ω ≡ | ω| > ω1∗ at the specified value ω1∗; (ii) initialization of RW cluster, switching on it into the SC control loop and the SC bringing to the required orientation in the ORF when the SINS signals are used; (iii) the SC angular stabilization in the ORF by autonomous digital control of the RW cluster with its unloading from the accumulated angular momentum (AM) using MD [Somov et al, 2018]. The problem of the SC autonomous angular guidance is solved while tracking the reference model for vector of the modified Rodrigues parameters (MRP) using a modularly limited digital control torque vector of the RW cluster at bringing the satellite orientation from arbitrary one to the required one in the ORF
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