An attitude simulator to support space missions

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...

Journal of Aerospace Engineering, Sciences and Applications, 2008

Placing a satellite or any other spacecraft in orbit is a risky and expensive process; years of research and a lot of money are transformed into equipments that will be beyond any possibility of maintenance in case something goes wrong. Therefore, space projects must be carried on as carefully as possible in order to guarantee that satellite equipments perform its mission properly. In that context, experimental validation of new equipment and/or control techniques through prototypes is the way to increase system confidence. The Space Mechanics and Control Division (DMC) of INPE is constructing a 1D simulator, with rotation around the vertical axis and a 3D simulator, with rotation in three axes, to implement and test satellite Attitude Control System (ACS). However, to perform experimental test it is necessary to estimate the platform inertia parameters in order to balance the platform accurately, so it behaves similar to space torque free conditions. This paper presents the equations of motion and control law design for a 3 D attitude control system simulator. This 3 D model is simplified to 1D simulator from which the inertia moment is estimated by a recursive least squares that uses experimental data. The platform data are obtained in a simple experiment where a reaction wheel is used to apply torques and a gyroscope is used to measure the platform angular velocity. The inertia moment estimated by this approach is very close to the platform inertia moment value obtained by other method.

2004

Virginia Tech has developed a testbed comprised of two independent spherical air-bearing platforms for formation flying attitude control simulation, the Distributed Spacecraft Attitude Control System Simulator (DSACSS). The DSACSS provides the flexibility to experimentally implement many types of control techniques. Novel individual platform control options include nonlinear compensation of an under-actuated system and coupled attitude control and energy storage techniques. Formation control schemes could consider integrated orbit and attitude control. Multi-actuator attitude control algorithms are being developed and tested on DSACSS, combining momentum/reaction wheel, control moment gyro, and thruster hardware. We are testing the effects of a moving baseplate on the performance of a magnetic bearing. The appropriateness of person-in-the-loop controllability is being investigated by linking DSACSS with Virginia Tech's Cave Automatic Virtual Environment (CAVE). Further, the CAVE can be used to unify two testbeds-DSACSS and the Formation Flying Testbed at NASA-Goddard Space Flight Center-for complete formation flying experimentation. This paper provides details on projects using DSACSS.

Progress in Canadian Mechanical Engineering. Volume 4, 2021

In this paper, the flight software development and design of the attitude determination and control system for the ESSENCE CubeSat mission is documented and discussed. The majority of the software is reused from the DESCENT mission, which was previously written by the RACS team, with strong inspiration from NGC Aerospace's work on the PROBA satellite program. The paper highlights the benefits of reusable software modules and methodologies between projects. Finally, it is encouraged that similar processes be considered by other CCP teams developing ADCS systems for future missions.

AIAA/AAS Astrodynamics Specialist Conference and Exhibit, 2004

This paper presents the attitude determination method for the Bifocal Relay Mirror Spacecraft Simulator. The simulator simulates three-axis motion of a spacecraft and has an optical system emulating a bifocal space telescope. The simulator consists of three control moment gyroscopes, rate gyros, two-axis analog sun sensor, and two inclinometers. The five-foot diameter platform is supported on a spherical air bearing to offer a low-torque environment. This paper demonstrates two attitude determination methods employing the measurements from a two-axis analog IR sensor, two inclinometers, and a triaxial gyroscope. The first method implements the conventional Kalman filter algorithm. The second method uses a nonlinear observer derived from the Lyapunov's direct method. Analytical and experimental results are presented to validate the proposed algorithm.

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.

This paper presents the attitude control system embedded in a FPGA device that serves as a testing platform for different attitude control schemes of small satellites. The ACS hardware is integrated in the SATEDU educational satellite, which was developed in the Engineering Institute of UNAM for satellite technology evaluation, research and teaching activities. The performance of the ACS hardware is evaluated and tested on an air bearing table where non-friction conditions in space are simulated. A key feature of the system is the remote FPGA reconfiguration that allows SATEDU to have a flexible tool to evaluate several schemes of orientation and control once the satellite is being tested on the air bearing. The paper presents the development and validation processes and constrains of the system using the on-board components.

Journal of Applied Research and Technology, 2014

This paper describes the integration and implementation of a satellite flight simulator based on an air bearing system, which was designed and instrumented in our laboratory to evaluate and to perform research in the field of Attitude Determination and Control Systems for satellites, using the hardware-in-the-loop technique. The satellite flight simulator considers two main blocks: an instrumented mobile platform and an external computer executing costume-made Matlab® software. The first block is an air bearing system containing an FPGA based on-board computer with capabilities to integrate digital architectures for data acquisition from inertial navigation sensors, control of actuators and communications data handling. The second block is an external personal computer, which runs in parallel Matlab® based algorithms for attitude determination and control. Both blocks are linked by means of radio modems. The paper also presents the analysis of the satellite flight simulator dynamics in order to obtain its movement equation which allows a better understanding of the satellite flight simulator behavior. In addition, the paper shows experimental results about the automated tracking of the satellite flight simulator based a virtual reality model developed in Matlab®. It also depicts two different versions of FPGA based on-board computers developed in-house to integrate embedded and polymorphic digital architectures for spacecrafts applications. Finally, the paper shows successful experimental results for an attitude control test using the satellite flight simulator based on a linear control law.

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.

2011 IEEE International Conference on Mechatronics, 2011

The present attitude control testbed is intended to provide an experimental facility that, in certain senses, emulates the dynamics of in-orbit conditions and permits to evaluate path planning and feedback control algorithms for precise satellite manoeuvres in laboratory situ. This paper shows the feasibility of the approach and demonstrates how attitude control rules become compatible for both realms. Equations of motion for this internally and externally constrained nonholonomic system are studied in the modern setting of geometric mechanics.