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ABSTRAKPenelitian ini merupakan penelitian pengembangan traktor otomatis. Meskipun penelitian mengenai traktor otomatis telah banyak dilakukan, namun pengembangan masih terus dilakukan untuk mendapatkan presisi yang lebih tinggi dan metode yang optimal. Tujuan penelitian ini adalah mengembangkan sistem pengendali kemudi traktor agar dapat mengikuti jalur kerja lintasan lurus ketika melakukan kegiatan pengolahan tanah. Model yang dikembangkan harus mampu menghitung sudut setir koreksi dari posisi traktor agar traktor mampu berjalan pada lintasan lurus yang telah ditentukan. Arah pergerakan traktor diketahui dari perbandingan dua posisi traktor yang diperoleh dari RTK DGPS. Algoritma pengendalian terdiri dari susunan perintah-perintah untuk mengendalikan traktor bergerak mengikuti lintasan acuan. Simulasi dilakukan untuk mengetahui kemampuan algoritma yang telah dibuat untuk mengendalikan traktor agar dapat berjalan mengikuti lintasan acuan. Kemampuan algoritma tersebut kemudian diuji dalam kondisi riil dilapangan pada lintasan lurus sepanjang 30 m dengan kecepatan traktor 0.5 m/s. Hasil pengujian di lapangan diperoleh tingkat akurasi kinerja kontrol sebesar 97.13% dan besar simpangan rata-rata terhadap lintasan acuan sebesar 8.62 cm. Kata kunci: Traktor otomatis, sistem pengendali kemudi, pengolahan tanah ABSTRACTThis research is the development of autonomous tractor. Although research for automatic tractor have been carried out, but it is still developed to get more precision and optimal method. The purpose of this research is to develop a trajectory control system tractor to follow a straight-line when the working soil tillage. Model that was developed to be able calculate steering angle correction of the tractor position so that the tractor will run on a reference trajectory. Tractor position is determined from RTK DGPS. Tractor direction is calculated from two position of tractor. Control algorithm consists of the arrangement of commands to control the tractor move the reference trajectory. Simulations were performed to determine controlling algorithm ability the tractor to follow reference trajectory. The algorithm ability is tested in real conditions on a straight-line path along 30 m with a speed of tractor 0.5 m/s in a field. The test results obtained in the field of performance accuracy rate is 97.13% control and average deviation with reference trajectory is 8.62 cm.

Developing a control system for hydroponics is gaining high attention because of the possibility to increase resource efficiency in producing high quality vegetables. Applying such a control system for nutrient solution in hydroponics requires less labour and operational cost. Therefore, it is important to develop a control system for nutrient solution in hydroponics. This research was aimed to develop a control system for lettuce cultivation in floating raft hydroponics. The control system has been developed to control temperature, EC, pH, DO, and ORP of nutrient solution in the controlled floating raft hydroponics by using Arduino Mega 2560 microcontroller as a control unit and micro SD card as storage media. The control system was found to be able to maintain the temperature of nutrient solution in the range of 20 to 25°C, EC in the range of 1500 to 1700 μS/cm, pH in the range of 5.5 to 6.2, DO in the range of 4 to 8 ppm, and ORP in the range of 300 to 500 mV. The control system performed well in maintaining these parameters as showed by a better lettuce growth in the controlled floating raft hydroponics, as compared to that of without the control system.

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Various studies of diesel fuel optimization have been done, one of them by using a permanent magnet on the fuel line, the lack of magnetic field intensity decreases along with time increasing by using an electromagnetic field. The purpose of this study is to analyse the biodiesel fuel characteristics due to exposure of electromagnetic fields in terms of the viscosity and vibration of these fuel molecules. Electromagnetic field is generated from wire coil of 5000-9000 on galvanum pipe with diameter of 1.5 cm and length of 10 cm and connected to 12 V batteries. Here, biodiesel fuel is inserted in a galvanum tube, magnetized for 1200 s, and tested its viscosity of the falling ball system by viscometer. Fuel functional groups as well as vibrations between fuel molecules are tested with FTIR. The results show that the magnetized fuel changes. The viscosity of fuels from 2933 to 2478 and an increasing in the absorption of fuel molecules ranges from 13-58%. Therefore, the increasing of vibrating fuel molecules decreases its molecular attraction tug. These indicate that the magnetized fuel molecule causes a changing in the fuel molecule, cluster becomes de-clustered. It is a potential method to clarify the phenomenon of fuel magnetization due to its efficient combustion process.

The sustainability of hydrogen as an energy carrier depends on the production process and the source of raw materials. The choice of substrate in anaerobic digestion process plays an important role to maximize biohydrogen production because it depends on its availability and the composition of substrate. The purpose of this study is to design and construct a prototype reactor for biohydrogen production and to determine the potential of H2 gas production from anaerobic digestion process. This study uses an experimental research method with three operating temperature variations in the reactor, at the range of thermophilic temperatures, i.e. 55°C, 60°C, and 65°C. The substrate used was POME and cow dung, and the process was conducted in 24 hours which is assumed to be the stage of non-methanogenic within the anaerobic process. From this research, the prototype of continuous stirred tank reactor (CSTR) in batch system was made from acrylic, with a capacity of 6 liters biomass waste. Using the reactor, total biohydrogen gas produced during 24 hours process with cow manure as substrate was 0,0932 gram at 55°C; 0,0307 gram at 60°C and 0,0797 gram at 65°C. While, biohydrogen production using POME as substrate was 0,0645 gram at 55°C; 0,1708 gram at 60°C, and 0,0636 gram at 65°C. These results indicate the potentiality of POME and cow manure to produce biohydrogen gas during anaerobic digestion process.

This study aims to develop an autonomous combine harvester. A manual steering combine harvester was modified autonomously using navigation systems of an RTK-DGPS, a gyroscope, and crawler speed sensors. These sensors could determine the combine position and heading required to guide the path. The control system is processed for these navigation sensors' data to make the decision of combine movement. Moreover, it commands the actuator to move the steering lever mechanism. The steering control's desired heading angle was determined from lateral error, heading error, and the traveling speed. In this study, the combined harvester's average forward traveling speed was set at 0.17 m/s, adjusted to a navigation sensor's sampling rate of 5 Hz and the steering mechanism delay. The preliminary test showed the combine could turn by pivoting one of its tracks which turned the radius was into 0.4 m. Furthermore, a guidance control system of the combine harvester was developed based on this test result. The developed guidance control system was successfully guiding the combine to follow the harvesting path. The test results showed that the root mean square of the lateral error was less than 0.1 m.

This paper proposes an optimal method for measuring the crawler rotational speeds of an autonomous combine harvester by the inductive proximity sensor. It mounts an inductive sensor on each wheel so it can detect the metals and the holes on the crawler drive gear. Detection of metals and holes continuously forming a cycle with a particular frequency. The crawler speed is determined by counting the number of cycles at one second as a frequency. The crawler speeds are proportional to the frequency. However, there is another way of measuring crawler speed by counting the cycle period. This research compares measuring methods for the crawler speeds using frequency and period to determine the optimal method. The results of the experiment show that measuring crawler speeds by periods is more accurate than frequency.