Design and validation of an MPC controller for CMG-based testbed

In the last years, Control Moment Gyros (CMGs) are widely used for high-speed attitude control, since they are able to generate larger torque compared to “classical” actuation systems, such as Reaction Wheels . This paper describes the attitude control problem of a spacecraft, using a Model Predictive Control method. The features of the considered linear MPC are: (i) a virtual reference, to guarantee input constraints satisfaction, and (ii) an integrator state as a servo compensator, to reduce the steady-state error. Moreover, the real-time implementability is investigated using an experimental testbed with four CMGs in pyramidal configuration, where the capability of attitude control and the optimization solver for embedded systems are focused on. The effectiveness and the performance of the control system are shown in both simulations and experiments

The Design and Testing of a Three-Degree-of-Freedom Small Satellite Simulator Using a Linear Controller with Feedback Linearization and Trajectory Generation

A small satellite simulator with attitude determination and control was designed and implemented in hardware. The simulator consists of inertial sensors for attitude determination and a pyramidal four-wheel momentum exchange system as the control actuators. A linearized PV controller with trajectory generation and feedback linearization was implemented, with the focus on controlling yaw. The simulator was tested on a spherical air bearing platform to allow three-degree-of-freedom operation. The simulator software was developed to read measurements from the sensors, apply the control algorithm, and send commands to the actuators. A data processing routine was developed. Electromechanical testing for the system as well as test results are presented

Three Axis Attitude Control System Design and Analysis Tool Development for the Cal Poly CubeSat Laboratory

The Cal Poly CubeSat Laboratory (CPCL) is currently facing unprecedented engineering challenges—both technically and programmatically—due to the increasing cost and complexity of CubeSat flight missions. In responding to recent RFPs, the CPCL has been forced to find commercially available solutions to entire mission critical spacecraft subsystems such as propulsion and attitude determination & control, because currently no in-house options exist for consideration. The commercially available solutions for these subsystems are often extremely expensive and sometimes provide excessively good performance with respect to mission requirements. Furthermore, use of entire commercial subsystems detracts from the hands-on learning objectives of the CPCL by removing engineering responsibility from students. Therefore, if these particular subsystems can be designed, tested, and integrated in-house at Cal Poly, the result would be twofold: 1) the space of missions supportable by the CPCL under tight budget constraints will grow, and 2) students will be provided with unique, hands-on guidance, navigation, and control learning opportunities. In this thesis, the CPCL’s attitude determination and control system design and analysis toolkit is significantly improved to support in-house ADCS development. The toolkit—including the improvements presented in this work—is then used to complete the existing, partially complete CPCL ADCS design. To fill in missing gaps, particular emphasis is placed on guidance and control algorithm design and selection of attitude actuators. Simulation results show that the completed design is competitive for use in a large class of small satellite missions for which pointing accuracy requirements are on the order of a few degrees

Study on orbital propagators: constellation analysis with NASA 42 and MATLAB/SIMULINK

Desde el comienzo de la era espacial, la filosofía de diseño de satélites estuvo dominada por diseños conservadores construidos con componentes altamente duraderos para soportar condiciones ambientales extremas. Durante las últimas dos décadas, la aparición de los CubeSats ha cambiado esta filosofía permitiendo todo un mundo de nuevas posibilidades. El despliegue de grandes constelaciones de CubeSats en órbita terrestre baja (LEO, en inglés) revolucionará el sector espacial al permitir ciclos de innovación más rápidos y económicos. Sin embargo, la confiabilidad de los CubeSats todavía se considera un obstáculo debido a las considerables tasas de fallo entre universidades y empresas, generalmente atribuidas a casos de pérdida completa de misión tras la eyección del desplegador orbital y al fallo de los subsistemas. Esta tesis se desarrolla en el marco del proyecto de investigación PLATHON, que pretende desarrollar una plataforma de emulación Hardware-in-the-loop para constelaciones de nanosatélites con comunicación óptica entre satélites y enlaces tierra-satélite. Un aspecto crucial de este proyecto es tener un propagador orbital suficientemente preciso con control de maniobras y representación gráfica en tiempo real. Los programas de propagadores disponibles se han analizado para seleccionar el sistema OpenSatKit de la NASA, una plataforma multifacética con un propagador incorporado conocido como 42. El propósito de esta disertación es analizar la viabilidad de implementación del programa para la creación de un banco de pruebas de constelaciones en comparación con un propagador previo desarrollado en MATLAB/Simulink. La documentación inicial es un enfoque de exploración para examinar las capacidades del 42 en distintos escenarios con objeto de adaptar el sistema PLATHON al funcionamiento interno y las limitaciones del programa. Las modificaciones y simulaciones del programa allanan el camino para el futuro desarrollo de la red interconectada PLATHON; específicamente, las comunicaciones entre procesos se han probado para imitar las entradas de los sistemas de control de actitud de las naves espaciales a través de interfaces de comunicación bidireccionales.Since the beginning of the space age, satellite design philosophy was dominated by conservative designs built with highly reliable components to endure extreme environmental conditions. During the last two decades, the dawn of the CubeSats has changed this philosophy enabling a whole world of new possibilities. The deployment of monumental CubeSat constellations in low Earth orbit is set to revolutionise the space sector by enabling faster and economical innovation cycles. However, CubeSat reliability is still considered an obstacle due to the sizeable fail rates among universities and companies, generally attributed to the dead-on-arrival cases and subsystem malfunctions. This thesis is developed in the framework of the PLATHON research project that intends to develop a Hardware-in-the-loop emulation platform for nanosatellite constellations with optical inter-satellite communication and ground-to-satellite links. A crucial aspect of this project is to have a sufficiently precise orbital propagator with real-time manoeuvring control and graphical representation. The available propagator programmes are analysed to select NASA’s OpenSatKit, a multi-facet platform with an inbuilt propagator known as 42. The purpose of this dissertation is to analyse the implementation feasibility of the programme for the creation of a constellation testing bench compared to previously selfdeveloped propagators based on MATLAB/Simulink. The initial documentation is a scouting approach to examine 42’s capabilities under distinct scenarios to adapt the PLATHON system to the programme’s inner workings and constraints. The programme modifications and simulations pave the way for the future development of the interconnected PLATHON network; specifically, the inter-process communication capabilities have been tested to imitate the inputs of spacecraft attitude control systems through bidirectional socket interfaces