ATTITUDE'AND'ORBIT'CONTROL' SYSTEM'(AOCS

2004

13 Journal-The Institution of Engineers, Malaysia (Vol. 65, No. 1/2, March/June 2004) thermal management. Consequently, the power budget for these tasks could be suppressed. This article is organized in the following manner: First, the miniaturisation design principle is viewed ...

Transactions of the Japan Society for Aeronautical and Space Sciences, Space Technology Japan

2011

The ISS Reshetnev is the Russian leader in development, manufacture and operations of navigation, geodetic and communication spacecraft, as well as Russian State programme for satellite telecommunication systems development. The research results achieved by the ISS Reshetnev in attitude control of some communication spacecraft, are presented.

2019

Based on the three-dimensional dynamics of a rigid body and Newton's laws, the simplified dynamics of a spacecraft is studied and described through the systematical representation, mathematical modeling and also by a block diagram representation, to finally simulates the spacecraft dynamics in the Matlab programming environment called Simulink. It is paramount to be able to identify and recognize the attitude (often represented with the Euler angles) and position variables like the degrees of freedom (DOF) of the system and also the linear behavior. All this to conclude up about the non-linear behavior presented by the accelerations, velocities, positions and Euler angles (attitude) when those mentioned are plotted against time. In addition to this, the linearized system is found in order to facilitate the control analysis and stability analysis, at using linear analysis tools of Simulink and concepts like controllability and observability, reaching the point of determining under the previous concepts to proceed with the control design phase. Lastly, an uncertainty and sensitivity analysis is realized, by means the Monte-Carlo and the Linear regression method (in Simulink too), to find the torque like critical model input, since it has the greatest effect on the response variables in the system; and thus finally, to implement the Linear Quadratic Regulator (LQR) controller, at using the lqr Matlab function.

AIAA Guidance, Navigation, and Control Conference and Exhibit, 2003

This article presents the details of a newly constructed 3-dof experimental spacecraft simulator facility at the School of Aerospace Engineering at the Georgia Institute of Technology. The main component of the facility is a cylindrical platform located on a hemi-spherical air bearing that allows friction-free rotation about three axes. The facility includes a variety of actuators and sensors: gas thrusters, variable-speed controlled momentum gyros (which can operate solely in a reaction wheel (RW) or in a control momentum gyro (CMG) mode), a two-axial sun sensor, a high-precision three-axial rate gyro, a three-axial magnetometer, and a complementary inertial measurement unit. The facility offers a truly integrated attitude control system (IACS) for experimental testing of advanced attitude determination and control algorithms.

55th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law

This work presents a preliminary study of the Brazilian Equatorial Atmosphere Research Satellite (EQUARS) attitude control subsystem (ACS). The satellite ACS requirements are dictated by the scientific experiments and the power supply needs. The scientific experiments require a three-axis attitude control subsystem in order to accomplish their pointing goals. In this paper the attitude control studies are conducted on the basis of the Linear Quadratic Gaussian regulator approach (LQG) to evaluate the control performance and the control effort during the satellite normal operational mode. The results indicate that the necessary actuators (reaction wheels) are available commercially on the shelf. The MATLAB ® /Simulink has been used as a software tool to implement all the computer simulations and visual graphics generation.

Computational and Applied Mathematics, 2018

SERPENS mission involves research and development of nanosatellites and is inserted in a set of activities carried on by Brazilian universities in the scope of strategies coordinated by AEB (Brazilian Space agency). The first satellite of a series, SERPENS-1, was put into orbit in September 2015, retiring in March 2016. SERPENS-2 mission is currently being designed. The experiments to be carried out in SERPENS-2 are: X and Gamma rays detection; South Atlantic magnetic anomaly detection and testing of a pulsed plasma thruster. Each experiment is related to the attitude. This paper is concerned with the Attitude Determination and Control System (ADCS) design of a 3U CubeSat. A proposal of

1996

Planetary penetrator missions offer excellent opportunities for examining the planetary structure in great detail. The success of such missions largely depends on navigating the penetrator to impact the target with the right orientation so that the scientific instruments onboard are safe. This in turn requires a sophisticated autonomous attitude determination and control subsystem (ADCS) onboard the penetrator. The aim of this paper is to propose a suitable mission sequence for such hard landers along with identification of appropriate sensors and actuators, and to examine the attitude determination and control strategies, desired for the right impact. A detailed investigation on using horizon detectors and Sun sensors for attitude determination along with the use of gas jets for attitude control will be discussed. The penetrator is a spin-stabilized platform, and hence a forced precession of the spin axis using the Sun sensor as the reference for firing the thrust pulses results in the penetrator following a rhumb-line attitude trajectory relative to the Sun direction. Results of simulations for the penetrator attitude control targeting the Lunar and Martian surfaces are presented.

2011

Within the motto smaller, cheaper and better, several nations can have now easy access to space, both buying or developing their own satellites. In fact, the number of small companies and even universities that make business selling space platforms weighting less than 100 kg, including payload, increases each day. If in the past small satellites mean also low power, low pointing accuracy, low price and therefore low reliability, today it is no longer valid. Some low cost satellites have 3 axis attitude control systems with high degree of pointing accuracy, like FedSat, CHIPSat and MOST. The pointing requirements for MOST (Canada's space telescope) are 25 arc-seconds in the telescope focal plane. The once expensive 3 axis attitude control system, based on gyros, star tracker and reactions wheels is now affordable for micro-satellites, giving both reliability and pointing accuracy for scientific and technological satellites. The attitude and control subsystem (ACS) acts on the reaction wheels in response to attitude errors provided by star tracker and gyros. Reactions wheels are simple brushless DC motor, coupled to a high inertia wheel. They provide torques over wide magnitude range, from micro Newton-meter up to hundreds of mili-Newtonmeter. Normally they are operated in "speed control mode" in which an internal closed loop control adjusts the motor current in order to achieve a commanded angular rate. Although reaction wheels can also operate in "current mode", the non-linear bearing friction, mainly in low speed rates, causes attitude deviation whenever the wheel changes its rotation sense. By the other hand, speed control mode introduces some time lack due to the internal control loop. This work aims to model the non-linear friction of the wheel, and to compensate it in the attitude control loop based in current mode. The reaction wheel and gyro are assembled in a one-axis air-bearing table, which provides micro friction similar to those encountered in space. Furthermore, both control modes, speed and current, shall be compared. The results proved to be helpful in deciding which strategy shall be used in future micro-satellite missions.

The International Journal of Multiphysics, 2007

The hybrid subsystem design could be an attractive approach for future spacecraft to cope with their demands. The idea of combining the conventional Attitude Control System and the Electrical Power System is presented in this article. The Combined Energy and Attitude Control System (CEACS) consisting of a double counter rotating flywheel assembly is investigated for small satellites in this article. Another hybrid system incorporating the conventional Attitude Control System into the Thermal Control System forming the Combined Attitude and Thermal Control System (CATCS) consisting of a "fluid wheel" and permanent magnets is also investigated for small satellites herein. The governing equations describing both these novel hybrid subsystems are presented and their onboard architectures are numerically tested. Both the investigated novel hybrid spacecraft subsystems comply with the reference mission requirements.

1999

The Bristol GyroWheel is an innovative attitude control system device that provides both an angular momentum bias and control torques about three axes while at the same time measuring the spacecraft angular rates about two axes. The principles of operation of this device are explained and the flight model design is described that is targeted at small satellite applications which is currently under development. A fully functional prototype of the GyroWheel has been developed that has demonstrated the actuator and rate sensing capabilities and some of the test results are given. One of the key advantages of the GyroWheel is that, for earth pointing applications, it can be used with a single 2-axis earth sensor to provide fine pointing control in all three axes. This allows for reducing the mass, power above all cost of this class of ACS system. A GyroWheel based ACS design is developed for an example case consisting of a small earth pointing microsat mission. Performance simulations are given that show that the pointing control can be maintained within 0.1 degrees in all axes. The GyroWheel promises to fulfill the need for low cost, low mass, high reliability and high accuracy attitude control systems for applications such as communications, remote sensing, and space science.

A control law for an Integrated Power/Attitude Control System (IPACS) for a satellite is presented in this paper. Four non-coplanar momentum wheels in a special configuration, and a set of three thrusters are used to implement the torque inputs. The momentum wheels are used as attitude control actuators, as well as an energy storage mechanism, providing power to the spacecraft. In that respect, they can be used to replace the currently used heavy chemical batteries. The thrusters are used to implement large torques for large and fast (slew) maneuvers and provide for the momentum management strategies. The momentum wheels are used to provide the reference-tracking torques and the torques for speeding up or slowing down the wheels for storing and releasing kinetic energy. The attitude tracking controller published in a previous work is adopted here. Power tracking for charging and discharging the momentum wheels is added to complete the IPACS framework. The torques applied by the momentum wheels are decomposed into two spaces which are perpendicular to each other, with the attitude control torques and power tracking torques in each space. This control law can be easily incorporated in an IPACS system on-board a satellite. The possibility of occurrence of singularities, where no arbitrary energy profile can be tracked, is studied for the wheel cluster considered in the paper. A generic momentum management scheme is considered to null the total angular momentum of the wheels so as to minimize the gyroscopic effects and prevent the singularity from occurring. A numerical example for a low earth near polar orbital satellite is provided to test the proposed IPACS algorithm. The satellite's boresight axis is required to track a ground station. In addition, the satellite is required to rotate about its boresight axis so that the solar panel axis is perpendicular to the satellite-sun vector.

This paper presents the development of two different air bearing tables, which can simulate attitude control systems for satellites with hardware-in-the-loop dynamics and control. Both systems are based on gas-bearing platforms in which several sensors and actuators were fixed. The first platform has a MEMS inertial sensor, and the second platform has several sensors and actuators that are engineering models similar to those usually employed in satellites. A PC/104 computer commands the first platform, which is responsible for driving 8 cold gas thrusters. On the other hand, the second platform is based on a Renesas 32 bits processor, which is responsible for three different subsystems: power supply, data handling and attitude control. The actuators in this case are reaction wheels and magnetic torque coils. The most important process for the correct operation of the simulators is to ensure accurate balancing of both platforms, because a difference between the center of gravity of t...

AIAA/AAS Astrodynamics Specialist Conference and Exhibit, 2008

was significantly enhanced. The AGSS estimator suite includes a spinning spacecraft Kalman filter and three single-axis attitude estimators: the Fuzzycones method, the Magnetometer-Only Single-Axis Estimator/Calibrator (MOSAEC), as well as a standard differentialcorrector batch-method estimator. The calibration suite of tools includes utilities to estimate relative time offsets, magnetometer calibration parameters, and Sun sensor biases.