Design of an aerodynamic attitude control system for a CubeSat

[摘要] ENGLISH ABSTRACT: The Cape Peninsula University of Technology, in collaboration with Stellenbosch University,is developing a 3-unit CubeSat for a low earth polar orbit. The two main payloadsare a camera and a radio frequency beacon. This beacon will be used to calibrate theradar antenna patterns of an antenna of the Hermanus Magnetic Observatory at theirbase in Antarctica. This thesis describes the development of an aerodynamic attitude determinationand control system needed to achieve three-axis stabilisation of the satelliteand to perform accurate pointing of the camera.The satellite structure is designed to utilise aerodynamic means of control. It includesfour feather antennae for passive pitch-yaw stabilisation and two active aerodynamic rollcontrol paddles. The sensors used are a three-axis magnetometer,ne sun sensor andnadir sensor. Three attitude determination methods are investigated, namely the Triad,Rate Kalman Filter and Extended Kalman Filter algorithm. Apart from the aerodynamiccontrol elements of the satellite, three magnetic torque rods and three nano-reactionwheels are also included in the design. Three control modes for the satellite are identi edand various control methods are investigated for these control modes.The various attitude determination and control methods are evaluated through simulationsand the results are compared to determine thenal methods to be used by thesatellite. The magnetic Rate Kalman Filter is chosen as attitude determination methodto be used when the satellite is tumbling and a combination of the sun Rate KalmanFilter and the Triad algorithm is to be used when the satellite experiences low angularrates. The B-dot and Y-spin controller is chosen for the detumbling control mode, theaerodynamic and cross-product control method for the three-axis stabilisation controlmode and the quaternion feedback control method for the pointing control mode of thesatellite. The combination of magnetic and aerodynamic control proved to be su cientfor the initial stabilisation of the satellite, but the three nano-reaction wheels are requiredfor the pointing control of the imaging process.

[发布机构] Stellenbosch University