SwissCube: The First Swiss Student Satellite Expected To Demonstrate An Ultra-light And Efficient Inertia Wheel
- Paper number
IAC-07-B4.5.07
- Author
Mr. Gavrilo Bozovic, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
- Coauthor
Mr. Omar Scaglione, Switzerland
- Coauthor
Mr. Christian Koechli, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
- Year
2007
- Abstract
The SwissCube is a CubeSat class pico-satellite (10x10x10 [cm3] cube weighting less than 1 [kg]) that will be launched in 2008. Its scientific mission is to take pictures of the night-glow phenomenon and characterize it. This data is expected to validate concept and technologies for a low-cost earth sensor. In order to have sufficient stability for the picture acquisition, the satellite relies on a number of actuators, among which a momentum wheel. The first task of this actuator is to stiffen one axis by a gyroscopic effect. This is obtained by maintaining a constant speed of the inertia. The second task is to compensate the disturbances, by accelerating or decelerating the wheel, and thus generating a torque on the satellite. For this wheel was designed a custom electric drive, complying with a number of specifications. Among which: - Speed range between 5000 and 11000 [rpm], in order to maintain sufficient gyroscopic effect and to be able to compensate the disturbances by accelerating the wheel during sufficient time - Acceleration of 3000 [rpm] per orbit, in order to be able to compensate the worst-case disturbances - Limit mass: 32 [g] (19 [g] for the inertia wheel, 13 [g] for the drive) - Maximal average power available: 100 [mW] (including the control electronics) - Dimensions: 80 [mm] diameter, 8 [mm] thickness. These geometric constraints are set to allow the mounting of the wheel in one side of the satellite, thus limiting the space loss for the payload. The purpose of this publication is to present the application of modern optimization to the design of the electric drive of the wheel. It includes: - A non-lineal multi-parameter optimization of an analytical mode of the drive - Validation of the design using finite elements - Key points for the design of an ad-hoc sensorless electronic, characterized by a very low power consumption and highly limited microcontroller usage. - Design of the prototype and measurements.
- Abstract document