Satellite Attitude Control System Design Research Articles

Comparison of the Satellite Attitude Control System Design using the H∞ Method and H∞/MLI with Pole Allocation Considering the Parametric Uncertainty

This paper presents the comparison of the Attitude Control System (ACS) design for a rigid-flexible satellite with two vibrations mode, using the traditional H∞method and the H∞/LMI with pole allocation considering the parametric uncertainty. In the ACS design is important take into account the influence of thestructure’s flexibility, since they can interact with the satellite rigid motion, mainly, during translational and/or rotational manoeuvrer, damaging the ACS. Usually the mathematics model obtained from the linearization and/or reduction of the rigid flexible model loses information about the flexible dynamical behaviour and introduces some uncertainty. The satellite model is represented by a flexible beam connected to a central rigid hub considering a setof parametric uncertainties. Simulations results have shown that the control law designed by the H∞/LMI method has better performance and it is more robust than H∞method since the first was able to support the action of the uncertainty perturbation and to control the rigid flexible satellite attitude and suppressing vibrations.

H∞ Control Design for a Rigid-Flexible Spacecraft under a Fuel Slosh Influence

The spacecraft Attitude Control System (ACS) performance and robustness depend on the interactioneffects between the fuel slosh motion, the panel's flexible motion, and the spacecraft rigid motion, mainly duringtranslational and/or rotational maneuvers. In regards to satellite pointing accuracy flexibility and fuel, slosh is thetwo most important effects that should be considered in the satellite ACS design since their interactions can damage the ACS performance and robustness. Once, the lowest vibration frequencies, normally of the sloshing modeare about six times less than of the ACS bandwidth. Therefore, there is a strong possibility that this mode can destabilize the ACS pointing accuracy. This phenomenon is called spillover because the control effort spills over outside the control bandwidth. As a result, the designer needs to explore the limits between the conflicting requirements of performance, that is, increase of the bandwidth without introduction noise in the ACS keeping the systemrobustness to parameters variation. In this paper, one applies the H infinity control method which can deal withthese two design requirements (performance and robustness) considering the controller error pointing that may belimited by the minimum time necessary to suppress disturbances that affect the satellite attitude acquisition. Theequations of motions are obtained considering the Lagrange method for small flexible deformations and a mechanical model of liquid sloshing which allows modeling and investigating the longitudinal dynamic characteristics of apartially filled liquid tank during a pitch maneuver, satisfying performance and robustness requirements.

Modeling and Simulation of Satellite Attitude Dynamics and Control System using Modelica

The control of attitude of a satellite is difficult to verify since several subsystems of different disciplines, e.g., flexible multibody dynamics, machines, electronics and control, are involved and strongly coupled. A traditional method is to model each single discipline subsystem with a domain specific software, and combine them through interfaces. However, the problems are that lots of interfaces between software have to be developed, and manual decoupling of systems should be considered during modelling process. In this Paper, models of the dynamics and the control system are established in a unified modelling software, MWorks, which is an Integrated Development Environment of Modelica. The model can be used to verify the satellite control strategy, and also provide an effective means for satellite attitude control system design. Moreover, on this basis, the whole satellite was modelled to access state parameters changes under the coupling of the dynamic subsystem, the attitude control subsystem, the power supply subsystem, the propulsion subsystem and the integrated electronic subsystem can be synthetically considered.

Satellite Attitude Control System Design Taking into Account the Fuel Slosh and Flexible Dynamics

The design of the spacecraft Attitude Control System (ACS) becomes more complex when the spacecraft has different type of components like, flexible solar panels, antennas, mechanical manipulators and tanks with fuel. The interaction between the fuel slosh motion, the panel’s flexible motion and the satellite rigid motion during translational and/or rotational manoeuvre can change the spacecraft center of mass position damaging the ACS pointing accuracy. This type of problem can be considered as a Fluid-Structure Interaction (FSI) where some movable or deformable structure interacts with an internal fluid. This paper develops a mathematical model for a rigid-flexible satellite with tank with fuel. The slosh dynamics is modelled using a common pendulum model and it is considered to be unactuated. The control inputs are defined by a transverse body fixed force and a moment about the centre of mass. A comparative investigation designing the satellite ACS by the Linear Quadratic Regulator (LQR) and Linear Quadratic Gaussian (LQG) methods is done. One has obtained a significant improvement in the satellite ACS performance and robustness of what has been done previously, since it controls the rigid-flexible satellite and the fuel slosh motion, simultaneously.

Design of Attitude Control Systems for CubeSat-Class Nanosatellite

We present a satellite attitude control system design using low-cost hardware and software for a 1U CubeSat. The attitude control system architecture is a crucial subsystem for any satellite mission since precise pointing is often required to meet mission objectives. The accuracy and precision requirements are even more challenging for small satellites where limited volume, mass, and power are available for the attitude control system hardware. In this proposed embedded attitude control system design for a 1U CubeSat, pointing is obtained through a two-stage approach involving coarse and fine control modes. Fine control is achieved through the use of three reaction wheels or three magnetorquers and one reaction wheel along the pitch axis. Significant design work has been conducted to realize the proposed architecture. In this paper, we present an overview of the embedded attitude control system design; the verification results from numerical simulation studies to demonstrate the performance of a CubeSat-class nanosatellite; and a series of air-bearing verification tests on nanosatellite attitude control system hardware that compares the performance of the proposed nonlinear controller with a proportional-integral-derivative controller.

Comparison of the LQG and H-INFINITY techniques to design experimentally a flexible satellite attitude control system

Attitude Control System (ACS) for flexible space satellites demands great reliability, autonomy and robustness. These flexible structures face low stiffness due to minimal mass weight requirements. Satellite ACS design usually based on computer simulations without experimental verification can face instability and/or inefficient controller performance due to model uncertainties. In this paper one investigates the robustness and performance of the time domain approach LQG (Lineal Quadratic Gaussian) and the frequency domain H- Infinity approach. The satellite ACS design is performed initially in a computer simulation environment, following experimentally verification of the same control algorithm, using Quanser rotary flexible link module. This investigation has shown that the controller performance based on simulation model can be degraded when applied in an experimental set up. So this prototype verification is fundamental before satellite onboard computer algorithms implementation.

Novel Concept for Autonomous Controller Design System Utilizing Machine Learning Applied to Satellite Attitude Control System Design Problem

A novel concept of controller design system is proposed. In this concept, the computer autonomously design an appropriate controller for a user-given control object under the given requirements/constraints. Different from the conventional CAD systems, the computer also plays the role of decision maker in the design process, such as selection of compensator, tuning of compensator parameters, or relaxation of requirements/constraints in case all of them cannot be satisfied. Decisions are made based on knowledge or "Expertise" as to control system design. This expertise is obtained via "Learning by Experimentation" which is a well known technique in the field of machine learning. With this vast and deep expertise, the proposed system can far more flexibly design appropriate controllers than usual expert system type tools even in complicated control problems. Computer simulations have been carried out, and it is verified that the proposed system has the flexible design capability even for ΜΙΜΟ control objects such as satellite attitude control system.