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Abstract:In China, it is difficult for manned aircraft to sow seeds in small and scattered plots, especially in areas including hills, swamps, telegraph poles, windbreaks, and residential areas; in such terrain, the sowing machinery cannot function properly. However, unmanned helicopters (UHs) are flexible enough to control and adapt to the complex environments that are not easily accessible by terrain sowing machinery and large agricultural aircraft, which have been widely used in agriculture. In this study, a centrifugal disc-type sowing device for an unmanned helicopter (CDTSDUH) was designed. The factors influencing the seed velocity when the seeds move away from the disc were explored by analyzing the forces of the seed acting on the sowing disc and the wind field of the UHs. The influential factors include the distance from the falling mouth to the center of the disc, the offset angle of the falling mouth, and the rotation speed of the disc. An orthogonal test was designed with the sowing width and the curvature of the sowing area as the indexes. The test results showed that the three factors mentioned above had a greater impact on the sowing width than the curvature of the seeding area. Moreover, the superior parameters of the disc were determined. It was also suggested that the above factor levels had little effect on the offset width of sowing. The results of the test conducted for studying the sowing uniformity of the CDTSDUH indicated that the maximum and minimum difference values among the number of particles of the sampling points in the forward direction was 11 and 8, and the coefficient of variation of the number of particles in each row was more than 20%, indicating less uniformity was achieved when sowing in the lateral (perpendicular to the forward direction) direction, as compared to that in the forward direction. This study determined the ideal values for the radius of particles position, the offsetting angle, and the disc speed of the sowing machinery designed. Furthermore, considering that there are so many factors that influence the manner in which a UH functions, more analysis results and test data of influencing factors need to be acquired by experiments. The uniformity of sowing needs to be further improved. The results provided some theoretical and experimental references for the technology research on the centrifugal disc-type sowing device for UHs.

Acoustic signals travels rapidly in water without attenuating fish telemetry. The digital sonar and passive acoustic has been used for fish monitoring and fish feeding. However, it is an urgent need to introduce new techniques in order to monitor the growth rate of fish during harvesting and without causing adverse effects to the harvested fish. Therefore, a novel technique was introduced to probe the acoustic signal frequency ratio in absence and presence of the fish in tanks, which basically uses an acoustic sensor (hydrophone), acoustic signal processing system (scope meter), and a signal monitoring system (fluke view). Acoustic signals were selected from 48-52 Hz frequency, measure of dispersion of frequency signal represented as a function of time via Xlstat software. Measure of dispersion displayed a significant effect of acoustic signal in the presence and absence of the fish in tanks. These optimised protocols of this study will help to control and prevent excessive wastage of feed and enhance proper utilization of feed that chiefly enhance fish growth in aquaculture

The endurance performance (EP) of electric multi-rotors spraying drones (EMSDs) is a key technical indicator that ensures the completion of tasks and improves their usefulness. To improve the EP of current EMSD, a test system was designed to determine the EP based on the EMSD test platform, and the performance evaluation method was studied. Firstly, a test model was established to determine the equivalent energy dissipation using the performance-testing platform of the EMSD. Secondly, a multisensory test system was constructed. An attitude sensor, high-power DC power supply, infrared thermal imager, and serial port server were selected. The mounting fixture was designed to meet the universal mounting requirements of drone. In addition, the software LabVIEW was employed to program the code for the controller and the host computer, where functions such as data collection, data processing, communication, and graphical user interface (GUI), were performed reliably in real time. Thirdly, the test method was explored by considering factors such as the power consumption, thermal efficiency ratio, and unit load power consumption rate. In particular, a comprehensive index method and expert consultation weight method were used to evaluate the EP of the EMSD with multiple indexes. Finally, a systematic real-machine test was carried out on the three types of drones that are currently widely used in the market. The results verified the effectiveness and feasibility of the proposed method, which was employed to test and evaluate the EP based on the EMSD performance testing platform. At the same time, it can provide a reference for the development of the EMSD.