Naufal, Muhammad Adam Daffa Naufal (2026) Perancangan Sistem Kendali Dynamic Positioning Pada Semisubmersible Offshore Platform Menggunakan Metode Sliding Mode Control. Other thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Operasi lepas pantai memerlukan sistem station keeping yang mampu mempertahankan posisi dan heading platform terhadap gangguan lingkungan. Penelitian ini bertujuan merancang sistem kendali Dynamic Positioning pada semi-submersible offshore platform menggunakan metode Sliding Mode Control serta menganalisis respons gerakan platform terhadap gangguan arus laut. Platform dimodelkan dalam tiga derajat kebebasan, yaitu surge, sway, dan yaw, dengan mengintegrasikan model dinamika, model kinematika, thruster allocation, dan empat azimuth thruster. Kesalahan posisi X, posisi Y, dan heading diolah oleh pengendali untuk menghasilkan gaya surge, gaya sway, dan momen yaw. Ketiga gaya dan momen umum tersebut selanjutnya dialokasikan menjadi delapan perintah aktuator berupa empat persentase RPM dan empat sudut azimuth. Pengujian dilakukan menggunakan MATLAB/Simulink pada kondisi open-loop, closed-loop tanpa gangguan, serta closed-loop dengan gangguan arus laut dari arah 0°, 45°, dan 90°, baik ketika platform berada maupun tidak berada pada titik referensi. Hasil pengujian menunjukkan bahwa sistem open-loop tidak mampu mempertahankan posisi karena platform terus mengalami perpindahan. Pada kondisi closed-loop tanpa gangguan, platform dari posisi awal X=5 m, Y=4 m, dan psi=0° dapat diarahkan menuju titik referensi dengan respons osilasi teredam dan mulai mencapai kondisi tunak pada rentang 350-500 detik. Ketika platform berada pada titik referensi, gangguan arah 0° menghasilkan penyimpangan maksimum posisi X sekitar 0,75 m, gangguan arah 45° menghasilkan penyimpangan posisi X dan Y masing-masing sekitar 0,85 m dan 0,90 m, sedangkan gangguan arah 90° menghasilkan penyimpangan posisi Y sekitar 1,60 m. Penyimpangan heading pada seluruh skenario relatif kecil dan kembali mendekati 0°. Ketika gangguan diberikan dari kondisi awal di luar titik referensi, sistem mampu mengarahkan platform kembali mendekati set point dengan kondisi tunak umumnya mulai tercapai pada kisaran 330-350 detik. Dengan demikian, sistem Sliding Mode Control yang dirancang mampu menjalankan fungsi station keeping dan menjaga kestabilan platform terhadap variasi arah arus laut, meskipun respons transien dan koordinasi alokasi gaya thruster masih dapat dioptimalkan. Penelitian ini mendukung Sustainable Development Goals, khususnya SDG 9 melalui pengembangan inovasi sistem kendali untuk infrastruktur lepas pantai, SDG 8 melalui peningkatan keandalan, keselamatan kerja, dan kontinuitas operasi industri offshore, serta SDG 14 melalui pengurangan potensi risiko operasional yang dapat berdampak terhadap lingkungan laut.
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Offshore operations require a station-keeping system capable of maintaining a platform’s position and heading under environmental disturbances. This study designs a Dynamic Positioning control system for a semi-submersible offshore platform using Sliding Mode Control and analyzes its motion response to ocean-current disturbances. The platform is modeled in three degrees of freedom surge, sway, and yaw by integrating dynamic and kinematic models, thruster allocation, and four azimuth thrusters. Errors in the X-position, Y-position, and heading are processed by the controller to generate the required surge force, sway force, and yaw moment. These generalized commands are then allocated into eight actuator commands comprising four RPM percentages and four azimuth angles. The system is evaluated in MATLAB/Simulink under open-loop, disturbance-free closed-loop, and disturbed closed-loop conditions with ocean currents from 0°, 45°, and 90°, both when the platform is initially at and away from the reference point. The open-loop results show that the platform cannot maintain its position and continues to drift. Under disturbance-free closed-loop control, the platform moves from X = 5 m, Y = 4 m, and ψ = 0° toward the reference point with a damped oscillatory response and reaches steady state within approximately 350–500 s. When initially at the reference point, currents from 0°, 45°, and 90° produce maximum deviations of approximately 0.75 m in X, 0.85 m in X and 0.90 m in Y, and 1.60 m in Y, respectively. Heading deviations remain relatively small and return close to 0° in all scenarios. When disturbances are applied away from the reference point, the controller drives the platform back toward the set point, with steady state generally beginning at approximately 330–350 s. The designed controller therefore performs the station-keeping function and maintains platform stability under different current directions, although its transient response and thruster-allocation coordination can be further optimized. This study supports SDG 9 through control-system innovation for offshore infrastructure, SDG 8 through improved operational reliability, occupational safety, and continuity, and SDG 14 through reduced operational risks to the marine environment.
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