Fadly, Muhammad (2016) Attitude Determination And Control For Stabilization And Pointing Accuracy For 3u Class Nano-Satellite. PhD thesis, Universiti Sains Malaysia.
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Abstract
Penyelidikan dan pembangunan 3U nano-satelit semakin meningkat sekarang ini dan telah membawa pelbagai misi ke angkasa lepas. InnoSAT adalah satelit 3U yang dibangunkan oleh Astronautics Technology Sdn.Bhd. (ATSB) dan lima universiti di Malaysia. Satelit itu dibangunkan dengan berat, kuasa, ruang dan bajet terhad. Misi satelit adalah untuk menangkap imej wilayah Malaysia daripada angkasa. Sistem yang sedia ada di dalam satelit menghasilkan dinamik tidak stabil dan berat tidak seimbang. Tiga paksi tork magnit, penderia matahari dan medan magnet dipasang pada paksi badan satelit. Tork kawalan satelit boleh dihasilkan oleh medan magnet daripada tork magnet yang serenjang dengan vektor medan magnet bumi yang berbezabeza di setiap posisi di orbit. Tiga paksi giroskopik berjenis Sistem Mikro Elektro Mekanikal (MEMS) dipasang sebagai penentuan utama sikap dan gabungan optimum penderia matahari dan medan magnet sebagai menengah. Sikap yang tepat, kedudukan dan kestabilan satelit di dalam orbit diperlukan ketika menangkap imej. Tesis ini membincangkan tentang bentuk pengiraan tepat dan cepat untuk penentuan sikap menengah dan juga penstabilan sikap, ketepatan menunjuk, dan kawalan gangguan untuk semua kedudukan satelit di orbit dengan menggunakan konfigurasi satelit sedia ada. Sikap ini telah dipilih menggunakan lima kaedah; TRIAD, The Quaternion Estimator (QUEST), kaedah-q, Fast Optimal Attitude Matrix (FOAM), Estimator Of The Optimal Quaternion-1 (ESOQ1) dan rekursi EKF. Kaedah yang dipilih dengan mempertimbangkan kerumitan dan kemungkinan untuk dapat diimplementasikan di dalam pengawal-mikro InnoSAT. Kaedah asas titik mampu menghasilkan keluaran yang tepat dan cepat apabila satelit itu berada jauh daripada gerhana tetapi kaedah EKF mampu melaksanakannya pada semua kedudukan. Kaedah-q menunjukkan hasil paling cepat dan tepat dalam menentukan sikap berbanding kaedah lain dengan kesilapan kurang daripada 5 %. Satelit ini dikawal dengan memasukkan mod terjerumus ke dalam model satelit untuk membentuk pengawal berdasarkan persamaan linear Riccati; LQR, H2, H¥, sintesi-m dan LPV berdasarkan Ketidaksaam Matriks Linear (LMI). Gelung tertutup dianalisis terhadap perubahan fungsi pemberat, ketidaktentuan, dan jumlah maklum balas di mana-mana kedudukan di orbit. Penggunaan kuasa pengawal amat dianggap melihat kemungkinan untuk dapat diimplementasikan di dalam sistem yang sedia ada. Pengawal ini mampu mengekalkan kestabilan hanya dalam bulatan kecil kedudukan satelit daripada titik kiraan pengawal tetapi jika satelit berada di luar bulatan maka pengawal baru mesti dikira semula. Kestabilan berterusan boleh dicapai dengan pengawal LPV, tetapi pengawal tidak dapat mengekalkan ketepatan menunjuk, dan penolakan gangguan pada masa yang sama. Sikap satelit disimulasi menggunakan 2-dimensi (2D) dan 3-dimensi (3D) Simulink MatlabTM. ________________________________________________________________________________________________________________________ Research and development of 3U nano-satellite is increasing nowdays and have been carrying various mission to space. InnoSAT is a 3U satellite developed by ATSB and five universities in Malaysia. The satellite is developed with limited weight, power, space and budget. The satellite mission is to capture images of Malaysia’s territory from space. Existing system in the satellite produces unstable dynamic and unbalance of weight. Three axis magnetorquers, sun and magnetic field sensor are installed on satellite body axes. The satellite control torque is produced by perpendicular magnetic field from magnetorquer and Earth’s magnetic field vector which varies periodically in orbit. Three axis Micro-Electro Mechanical Systems (MEMS) gyro is installed as a primary attitude determination and optimal combination of sun and magnetic field sensor as a secondary. Accurate attitude, position and stability of the satellite in orbit while capturing the image is required. This thesis discuss about designing of accurate and fast computation of secondary attitude determination and also attitude stabilization, pointing accuracy, and disturbance rejection control for all satellite position in orbit with existing satellite configuration. The attitude is determined using five methods; TRIAD, QUEST, q-method, FOAM, ESOQ1 and a recursive EKF. The methods are chosen by considering the complexity and possibility to be able to implement in onboard micro-controller of InnoSAT. The point base methods are able to produce accurate and fast output when the satellite out of eclipse but the EKF is able to perform at all position. The q-method shows the fastest and accurate attitude determination compare with other six methods with less than 5% error. The satellite is controlled by inserting sliding mode into satellite model to design controller based on linear Riccati equation; LQR, H2, H¥, m-synthesis and LPV based on Linear Matrix Inequality (LMI). The closed loop is analyzed due to variation of weighting functions, uncertainties, and number of feedback at any position in orbit. The controller power consumption is highly considered to see the possibility to implement in existing system. The controller is able to maintain the stability only in small radius position from its design point but if the satellite go beyond the radius the new controller must be recalculated. The continuous stability can be achieved by LPV controller, but the controller unable to maintain stability, pointing accuracy, and disturbance rejection simultaneously at the same time. The attitude is represented in Two Dimensions (2D) and Three Dimensions (3D) simulation using Simulink MatlabTM.
| Item Type: | Thesis (PhD) |
|---|---|
| Additional Information: | Full text is available at http://irplus.eng.usm.my:8080/ir_plus/institutionalPublicationPublicView.action?institutionalItemId=2787 |
| Subjects: | T Technology T Technology > TK Electrical Engineering. Electronics. Nuclear Engineering > TK7800-8360 Electronics |
| Divisions: | Kampus Kejuruteraan (Engineering Campus) > Pusat Pengajian Kejuruteraaan Elektrik & Elektronik (School of Electrical & Electronic Engineering) > Thesis |
| Depositing User: | Mr Mohd Jasnizam Mohd Salleh |
| Date Deposited: | 12 Jul 2018 06:48 |
| Last Modified: | 14 Aug 2018 08:30 |
| URI: | http://eprints.usm.my/id/eprint/41003 |
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