Ultrasonic Doppler Speed Sensor for Agricultural Vehicles: Effects of Pitch Angle and Measurements of Velocity Vector Components

High-precision ground speed sensors could be used as a component of navigation or control systems for agricultural vehicles. This paper describes the characteristics of the speed sensor developed by the authors, focusing on the effects of pitch angle. For this purpose, experiments were carried out at various sensor depression angles. The results showed that the output was almost the same as the theoretical value for depression angles of 40 to 50 degrees, although the measurement error was relatively large in the case of artificial turf with short pile. Measurement tests at various angles between the traveling direction and the sensor direction in the horizontal plane were also carried out to determine the possibility of velocity vector measurement including sideslip. It was estimated that the measurement error would be within 3% of the absolute velocity in any direction. The results suggested that it is possible to measure the velocity vector without the effects of pitch angle by using multiple sensors facing in different directions

Vibration analysis during grass harvesting according to ISO vibration standards

This research evaluated the working efficiency and comfort of operation by measuring vibration acceleration of tractors during grass harvesting. A real-time kinematic global positioning system and an inertial measurement unit installed in a tractor normally used by farmers during grass harvesting were used to acquire tractor vibration acceleration data. Analysis of the position and vibration acceleration data of tractors by a Fourier transformation yielded a power spectrum of vibration acceleration at each frequency (1-10 Hz) and position. The root mean square of vibration acceleration at each frequency (1-10 Hz) was calculated with the center frequency of the 1/3 octave bands (1.0,1.25,1.6,2.0,2.5,3.15,4,5,6.3,8,and 10 Hz) based on ISO standards. To evaluate the working efficiency in the grassland, geographical information system maps were generated using the power spectrum of vibration acceleration and the limit on working time for each frequency that negatively affected the tractor driver. The vibration acceleration in the longitudinal (ax) and lateral (ay) directions at the center frequency of the 1/3 octave band below 2.0 Hz exceeded the fatigue-decreased proficiency and reduced the comfort boundaries stipulated in ISO 2631 (1974). In the area where working characteristics are severe, the vibration acceleration in the vertical direction (az) is high. The vibration acceleration in the az direction at the center frequency of the 1/3 octave band (5-10 Hz) clearly indicates discomfort during grass harvesting and a decrease in the work efficiency beyond one hour. The total vibration acceleration (av) at the center frequency of 5.0 Hz of the 1/3 octave band served to evaluate comfort in the whole field during grass harvesting - the av value is higher than that at other frequencies. The area with severe working characteristics showed a higher av value at the center frequency of 8.0 Hz than that at other frequencies

Development of unmanned airboat for water-quality mapping

We have developed an unmanned airboat for mapping the water quality of shallow (<1 m) mire pools where aquatic weeds flourish. A differential global positioning system receiver and a global positioning system compass were used as navigation sensors. The airboat was designed for automatic operation. Using the boat, we measured parameters such as temperature, pH, dissolved oxygen, electrical conductivity, turbidity and chlorophyll-a of the water in a 26-ha mire pool in Hokkaido, Japan. To determine the appropriate sampling-grid size, the water was sampled along lines spaced 10 m apart, and the spatial variability of the mire pool characteristics was determined using a semivariogram. Results from the spherical model fit to the empirical semivariogram revealed spatial fluctuations in the water-quality parameters on the scale of 100 to 140 m. Because the size of the grid must be smaller than this scale, a second survey of water samples in the pool was carried out using a grid size of 40 m × 40 m. At each target point, a water-quality sensor unit was lowered from the boat. The survey of the entire grid area took approximately 231 min, during which time 130 points were sampled. The precision of the sampling points was within 2.6 m. The maximum speed and yaw rate of the airboat were 1.2 m s^[-1] and 48 deg s^[-1], respectively. The resulting maps showed the fine-scale distribution of water quality

Improving the Energy Balance of Hydrocarbon Production Using an Inclined Solid–Liquid Separator with a Wedge-Wire Screen and Easy Hydrocarbon Recovery from Botryococcus braunii

The green colonial microalga Botryococcus braunii produces large amounts of hydrocarbons and has attracted attention as a potential source of biofuel. When this freshwater microalga is cultured in a brackish medium, the hydrocarbon recovery rate increases; furthermore, the colony size becomes large. In this study, the effects of such changes on the energy balance of harvesting and hydrocarbon recovery were studied via filtrate experiments on an inclined separator and extraction from a concentrated slurry. The inclined separator was effective for harvesting large-colony-forming algae. The water content on the wire screen of slit sizes larger than 150 &micro;m was &lt;80% and a separation rate of &gt;85% could be achieved. The input energy of the harvesting using the brackish medium with this separator was &asymp;44% of that using the freshwater medium with vacuum filtration, while the input energy of the hydrocarbon recovery using the brackish medium was &asymp;88% of that using the freshwater medium with pre-heating before n-hexane extraction. Furthermore, the energy profit ratio of the process in the brackish medium was 2.92, which was &asymp;1.2 times higher than that in the freshwater medium. This study demonstrated that filtration techniques and hydrocarbon recovery from B. braunii with a low energy input through culture in a brackish medium are viable

Thinning of Botryococcus braunii Colony Sheath by Pretreatment Enhances Solvent-Based Hydrocarbon Recovery

Botryococcus braunii is a green microalga that is attracting attention as an alternative aviation fuel owing to its hydrocarbon production. In this study, we investigated two approaches to reducing the energy required by pretreatment for hydrocarbon recovery by solvent extraction. Saltwater culture has been reported previously only for the B race of Botryococcus braunii; it improved hydrocarbon recovery from the A race too. We developed a hot water rinsing method that reduced the temperature requirement from the 85 &deg;C which was previously reported for the B race. As the salt concentration in the medium increased, the colony sheath that covered the entire colony surface of the Yamanaka strain (race A) became thinner and the hydrocarbon recovery increased. Saltwater culture can be applied to race A without any energy input. Hydrocarbon recovery from the Showa strain (race B) exceeded 90% after nine rinses with 70 &deg;C hot water while maintaining this temperature. Thus, both pretreatments lowered the treatment temperature by at least 15 &deg;C compared to previously reported methods. Both treatments improved hydrocarbon recovery by thinning the colony sheaths