Digital Twins in Space Research: the Case of STASIS, EXTREMA's Attitude Simulation Platform
Creators: name: Di Domenico, Gianfranco
name: Schingaro, Marco
name: Topputo, Francesco
Publisher: name: Zenodo
Year: 2023
Subjects: Digital Twin
EXTREMA
CubeSat
Space Exploration

description: Digital twins are emerging development approaches that have the potential to revolutionize the way engineers and designers approach the design, development, and operation of complex systems. A digital twin is a digital replica of a physical system, process, or product that can be used to simulate, analyze, and optimize the performance of the system in a virtual environment. Digital twins can be used to optimize the design of a physical system, predict its behavior under different conditions, and monitor and control it in real-time. This technology is used in various industries such as manufacturing, aerospace, automotive, and construction to improve the performance, efficiency, and safety of physical systems. In this paper, we aim to provide an example of how the concept of the digital twin has the potential to have an impact also on space research. The case study will be represented by STASIS (SpacecrafT Attitude Simulation System), an attitude simulation platform in development at Politecnico di Milano. STASIS will be employed in the EXTREMA Simulation Hub, an integrated facility in which algorithms and systems to enable deep-space CubeSats with autonomous guidance, navigation, and control (GNC) capabilities will be tested. The requirements for the attitude simulation platform include conditions spanning different domains, such as structural, power management and generation, aerodynamics, electro-mechanical systems. In order to streamline the design and development phases of STASIS lifecycle, the approach of employing a digital twin is employed prior to prototyping to test and validate different design alternatives, reduce prototyping costs, and verify and validate algorithms and code. A first demonstration of the usefulness of the digital twin model is the design of STASIS’ power generation and management subsystem. As the platform will be utilized in simulations that extend over multiple days, it is not feasible to rely on battery power to sustain the subsystems hosted on it. For this reason, a wireless power generation system – consisting in a power beaming solution with a high-power LED lamp as emitter and a photovoltaic array as receiver – has been conceptualized. The three rotational degrees of freedom of the platform raised the issue of non-uniform illumination of the solar array. In this phase, the utilization of a digital model of the platform enabled us to investigate various configurations for the solar array electronics and conduct preliminary testing of maximum power point tracking algorithms for the power converter. Both physicsdriven and data-driven methodologies were utilized to develop this aspect of STASIS's digital twin. STASIS’ virtualized was also employed to test different balancing procedures. In order to minimize the impact of gravitational torques on the platform, it is crucial to attain an appropriate balance by relocating the center of mass (CoM) of the system towards the center of rotation (CoR) of the air-bearing spherical joint. A set of 8 movable masses, driven by stepper motors, are utilized to accomplish this. The implementation of the digital twin facilitated the testing and pre-selection of the optimal balancing algorithm by running them on virtual controllers before the implementation of the real-world actuators, resulting in a reduction in development time for the platform. Furthermore, as different balancing procedures necessitate the presence of different actuators and sensor configurations, the results obtained through the digital twin implementation indicated which ones to include in the final version of the platform and which not. Additionally, the digital twin was also leveraged to enhance the performance and accuracy of the platform. A significant source of disturbances for these types of systems is the presence of aerodynamic drag, which is highly dependent on the structural configuration. Through the utilization of CFD simulations, a dataset of anticipated aerodynamic torques acting on the platform was obtained and utilized as a reference to implement a real-time interpolator to compute the expected torque to be counteracted with the on-board actuators. In conclusion, the utilization of digital twin methodologies to optimize the design operations and perform simulations of various what-if scenarios has proven to be a valuable approach for the development of STASIS. Furthermore, additional benefits related to this specific application are anticipated once the EXTREMA Simulation Hub becomes operational. The connection of the digital twin to the sub-components of the platform will enable the provision of real-time information on the status of the platform, enable the monitoring of the interfaces and data exchanges with other facilities, and provide valuable visualization tools for a better understanding of the occurring events and their corresponding implications on the simulated spacecraft.
description: Poster to be presented at ESA GNC 2023 conference, poster panel #20