Attitude Determination and Control - cubesat-project/CubeSat GitHub Wiki
Attitude Determination and Control
Brief Descriptions of Attitude Determination and Control System (ADCS)
The CubeSat does not have strict pointing requirements. For this reason, a passive magnetic attitude control (PMAC) system will be used. By design, the z-axis of the satellite will align with the Earth's Magnetic Field, providing approximate Nadir pointing in Low Earth Orbit. The purpose of this system is to ensure the CubeSat is stable enough to communicate with the ground station and to collect data.
Requirements
| Requirement ID | Requirement Description |
|---|---|
| ADCS-01 | The CubeSat shall have pointing accuracy of 15 degrees |
| ADCS-03 | The ADCS system shall read data from the gyroscope, solar panels, and magnetic compass |
| ADCS-05 | The spacecraft ADCS system shall detumble the spacecraft |
| ADCS-10 | In ADCS Payload Operation Mode, the ADCS shall detumble to a spin rate less than 63 degrees per second in order for it to capture data. |
Selected Components
Bar Magnet
- Quantity: 1
- Material: NdFeB, Grade N42
- Plating/Coating: Ni-Cu-Ni (Nickel)
- Dimensions: 3.175 mm dia. x 50.8 mm length
- Mass: 3.02 g
- Selected Magnet: https://www.kjmagnetics.com/proddetail.asp?prod=D2Y0
Hysteresis Rods
- Quantity: 4 (2 in x-direction, 2 in y-direction)
- Material: Hy-Mu 80
- Dimensions: 1 mm dia. x 50 mm length
- Mass: 0.3435 g
- Supplier: MU shield https://www.mushield.com/material-sales/hymu-80-magnetic-shielding-alloy-astm-a753-alloy-4/
Three-Axis Digital Compass
- Two-three axis digital compasses are included on the OBC as peripherals. The two compasses are placed on opposite sides of the OBC
- Measure direction and magnitude of Earth’s magnetic field.
Gyroscope: Silicon Sensing Three-axis PinPoint® gyro evaluation board (CRM100 & 2x CRM200)
- Default measurement range of ±75º/s
- Part Number: 400046-0300
- https://www.siliconsensing.com/media/1158/crm100-00-0100-132_rev_10.pdf
Simulation Results
The following figures show the results from the detumbling simulation with the selected components for the PMAC system. The simulation results verify that the CubeSat will detumble within 8 days with the selected components. The simulation was designed by the McMaster NEUDOSE Satellite Team and modified for the Western Ukpik-1 Mission ADCS requirements.
Fig. 1: Satellite angular velocities
Fig. 2: Error between z-axis and magnetic field
Fig. 3: Magnitude of external torques
Fig. 4: External torques about the satellite z-axis
