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Author: Antonio Giustino Publisher: ISBN: 9781423556541 Category : Languages : en Pages : 126
Book Description
The near future will see a proliferation of small low cost communication and science satellites with modest (Æ0.1-0.5 deg) pointing requirements which will use attitude determination Systems (ADSs) of low power, weight, size and cost. This thesis is a study into the integration issues of such a system, that uses micro-mechanical inertial sensors and an interferometric GPS (IGPS) attitude determining receiver that are tightly coupled using "model based" estimation techniques. The integration issues analyzed include: the effect on performance of limited IGPS use, the effect on performance of various gyro qualities and model accuracies, the inherent robustness to failure of the system and a power consumption analysis for a minimum energy IGPS receiver. It was found that attitude performance varied less than 0.05 degrees (RSS) when the interval between GPS phase measurements was varied from once every second to once every 30 seconds. This justifies the development of a minimum energy receiver to take advantage of the power savings of less frequent GPS measurements. During times of low dynamic model accuracy, the IGPS/MM Gyro ADS was bound by the steady state attitude error of the IGPS which averages a 1 sigma RSS error of about 0.28 degrees within the GPS update range mentioned above. Attitude error also depends on the gyro quality, and various projected system accuracies are given using several gyro error models. Real micro-mechanical gyro data from a prototype gyro was successfully integrated with real GPS phase measurements using an Extended Kalman filter. Failure scenarios and power expenditures were also analyzed using steady state linear covariance analysis as well as a space simulation which uses orbital parameters of a telecommunication satellite constellation. Total power expenditure of 200 mWatts can be achieved for this system and still fulfill mission requirements.
Author: Antonio Giustino Publisher: ISBN: 9781423556541 Category : Languages : en Pages : 126
Book Description
The near future will see a proliferation of small low cost communication and science satellites with modest (Æ0.1-0.5 deg) pointing requirements which will use attitude determination Systems (ADSs) of low power, weight, size and cost. This thesis is a study into the integration issues of such a system, that uses micro-mechanical inertial sensors and an interferometric GPS (IGPS) attitude determining receiver that are tightly coupled using "model based" estimation techniques. The integration issues analyzed include: the effect on performance of limited IGPS use, the effect on performance of various gyro qualities and model accuracies, the inherent robustness to failure of the system and a power consumption analysis for a minimum energy IGPS receiver. It was found that attitude performance varied less than 0.05 degrees (RSS) when the interval between GPS phase measurements was varied from once every second to once every 30 seconds. This justifies the development of a minimum energy receiver to take advantage of the power savings of less frequent GPS measurements. During times of low dynamic model accuracy, the IGPS/MM Gyro ADS was bound by the steady state attitude error of the IGPS which averages a 1 sigma RSS error of about 0.28 degrees within the GPS update range mentioned above. Attitude error also depends on the gyro quality, and various projected system accuracies are given using several gyro error models. Real micro-mechanical gyro data from a prototype gyro was successfully integrated with real GPS phase measurements using an Extended Kalman filter. Failure scenarios and power expenditures were also analyzed using steady state linear covariance analysis as well as a space simulation which uses orbital parameters of a telecommunication satellite constellation. Total power expenditure of 200 mWatts can be achieved for this system and still fulfill mission requirements.
Author: Varun Puri Publisher: ISBN: 9781423581420 Category : Languages : en Pages : 201
Book Description
A Global Positioning System (GPS) based attitude determination system has never been used as the primary source of attitude information for a spacecraft application. The fundamental reason for this is that a spacecraft attitude determination system must achieve fast attitude acquisition and near perfect solution reliability. Existing GPS based attitude systems cannot meet these requirements, so GPS has only been used as a secondary sensor for spacecraft missions. In this thesis, an attitude determination system is developed which meets spacecraft performance requirements using GPS as the primary source of attitude information. System hardware includes a multiple antenna GPS receiver and a low cost three axis gyro assembly. The attitude determination software consists of an integer ambiguity solution algorithm, an Extended Kalman Filter and an integrity monitoring architecture to improve robustness of the design. The integer solution algorithm resolves GPS integer ambiguity with no a priori attitude knowledge or external aiding. Processing is streamlined by solving the two-dimensional yaw and pitch problem and the one- dimensional roll problem independently.
Author: Jeremy P. Stringer Publisher: ISBN: 9781423536017 Category : Languages : en Pages : 153
Book Description
With the invention of Micro Electro-Mechanical Systems (MEMS) it has become possible to fabricate micro-inertial sensors. These new sensors have application in creating autonomous guided weapons systems. New technologies like Micro Unmanned Aerial Vehicles (UAVs), which cannot use conventional inertial sensors, rely on technologies like micro-inertial sensors to operate. Also, such sensors have the capability to reduce both power and space consumption on conventional aircraft. This technology is not yet mature, and current micro- inertial sensors do not have the accuracy required for highly precise navigation. To try to increase the accuracy of micro-inertial sensors, researchers are turning toward micro-optical gyroscopes. Creating a working micro-optical gyroscope is a difficult proposition as their small size precludes micro-optical gyroscopes from having large enough path lengths to sense useful rotation rates. Techniques need to be developed to create micro-optical gyroscopes with path lengths long enough to sense navigation grade rotation rates. This research proposes a new type of MEMS optical gyroscope. The device, called the AFIT MiG is an open loop Sagnac interferometer on a MEMS die. Mirrors are placed on the die to spiral light inward from the outside to the center of the die thereby increasing the optical path length of the device. When the AFIT MiG was simulated using flight profiles generated in MATLAB, the optical path length of the device was long enough to measure rotation rates, which were greater in strength than the noise inherent in the measurement. This research also shows the ability to propagate light around an open loop MEMS interferometer with enough signal strength at the detector to measure.
Author: Antonio Giustino
Author: Antonio Giustino
Author: Bruce Carl Chesley
Author: John Christian Stoll
Author: 
Author: Varun Puri
Author: Alison Kay Brown
Author: Machiel de Jong
Author: Jeremy P. Stringer
Author: 
Author: 姜義德