Absolute Attitude Determination System for a Spherical Air Bearing Testbed

Paper number

IAC-15,C1,6,1,x28747

Author

Dr. David Bamber, Surrey Space Centre, University of Surrey, United Kingdom

Coauthor

Dr. Jason Forshaw, Surrey Space Centre, University of Surrey, United Kingdom

Coauthor

Dr. Thomas Frame, Surrey Space Centre, University of Surrey, United Kingdom

Coauthor

Prof.Dr. Guglielmo Aglietti, Surrey Space Centre, University of Surrey, United Kingdom

Coauthor

Mr. Ramin Geshnizjani, Institute of Flight Mechanics and Control, University of Stuttgart, Germany

Coauthor

Mr. Simon Goerries, Airbus Defence and Space (DS), Germany

Coauthor

Dr. Andrei Kornienko, Airbus Defence and Space (DS), Germany

Coauthor

Mr. Jens Levenhagen, Airbus Defence and Space (DS), Germany

Coauthor

Prof. Yang Gao, Surrey Space Centre, University of Surrey, United Kingdom

Coauthor

Mr. Abadi Chanik, Surrey Space Centre, University of Surrey, United Kingdom

Year

2015

Abstract

Three degree of freedom (3-DOF) ACS satellite testbed systems are essential hardware-in-loop testing facilities for the construction of a wide range of intelligent AOCS algorithms.  Intrepid is a 3-DOF spherical air-bearing satellite testbed custom designed at the Surrey Space Centre, UK, and installed on-site at Airbus DS in Friedrichshafen, Germany for the AOCS & GNC Group.  The testbed consists of a table-top for the mounting of satellite hardware, 4 control moment gyroscopes (CMGs) mounted in a pyramid configuration and a sensor suite including an IMU.  Under normal operation the CMGs can be used to command the table to required angles thus testing the AOCS alogrithms using only the IMU as an attitude sensor.

Satellites require long-term stable and short-term high resolution attitude measurements, which are fused on-board to estimate the attitude.  The IMU provides high resolution attitude information, but has the drawback of not knowing the initial attitude and also drifting over time.  This paper concerns the development of an absolute attitude determination system (AADS) that utilises an infra-red camera, a series of LEDs positioned across the table-top, and intelligent software to independently determine the absolute attitude of the table-top.  The system thus provides long-term stable attitude measurements and overcomes the shortcomings of the IMU.

The newly installed AADS software contains vision processing and triangulation algorithms that provide real-time absolute attitude information to the host computer.  The vanilla system can achieve attitude determination accuracy within 1 degree in yaw and 2 degrees in pitch and roll.  The software can calibrate itself compensating for intrinsic and extrinsic offsets including incorrectly placed LEDs and a misaligned camera system.  A sub-pixel feature detection technique is utilised to enhance the accuracy of the system. It is shown that by modifying the position of the LEDs or modifying the placement of the camera, more optimal attitude accuracies along different axes can be obtained. This paper will detail the main operation of the system from both a hardware and software perspective and provide experimental results during operation.

Abstract document

IAC-15,C1,6,1,x28747.brief.pdf

Manuscript document

IAC-15,C1,6,1,x28747.pdf (🔒 authorized access only).

To get the manuscript, please contact IAF Secretariat.