Projects / June 17, 2020
WE ARE PROUD TO ANNOUNCE THAT SPACE INVENTOR IS INVOLVED IN TWO PAPERS THAT ARE ACCEPTED FOR ESA’S CONFERENCE ON GUIDANCE, NAVIGATION AND CONTROL SYSTEMS 2021 (GNC 2021).
ATTITUDE CONTROLLER GUARANTEES NOT POINTING SENSITIVE OPTICAL INSTRUMENTS TOWARDS THE SUN
In collaboration with Aalborg University, our control engineer, Lasse Bromose, and CEO, Karl Kaas, have written a paper regarding a constrained nonlinear model predictive control for CubeSat attitude control.
The paper proposes an attitude controller that uses best-effort pointing and with a guarantee of compliance with constraints. This is useful for missions that carry instruments which should not be pointed directly at the Sun.
The above video shows an example of a sun-avoidance maneuver. The output of a simulation done with the synthesized controller was fed into VTS to produce this visualization.
THE PROCESS: FROM RESEARCH TO PRACTICE
In the fall of 2019, Lasse Bromose began researching different strategies for guaranteeing that a star-tracker would never point towards the sun. After researching the current studies, he started formulating a model predictive control law which could be extended with constraints. It was challenging to reach a mathematical formulation that was compatible with the current solvers. The great breakthrough happened after AAU proposed Bromose to use a specific solver which is relatively new and functions better than other solvers in regard to working with nonlinearity. By the end of December 2019, the attitude controller was successfully tested on a Raspberry Pi.
The next step is to test the controller on a Space Inventor OBC, and in 2021, Lasse will attend the GNC 2021 to present the findings. These will be presented in the session concerning “Advances in Controls”.
This animation is based on the same simulation as the video shown earlier. It shows how the attitude of the satellite changes in order to avoid the sun. The gray cone denotes the “keep out” area, and it can be seen that the controller keeps the sun at the edge of the cone.
Lasse Bromose has previously worked with the co-authors from AAU, Joakim B. Petersen and Jens F. D. Nielsen. Petersen and Bromose worked together as student programmers where Peterson affected Bromose into taking a master’s degree in Control Engineering. Nielsen introduced Bromose to the satellite projects at AAU where Bromose worked on two satellite projects, AAUSAT4 and AAUSAT5.
CO-AUTHOR ON STAR-TRACKER PAPER
SpSpace Inventor is the co-author on a paper that presents a novel, high-performance star-tracker for small satellites. These findings will be presented by our partners from Terma in the session concerning “Advances in Sensors and Actuators”.