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Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Farmland information acquisition is the basis of precision agriculture. Multi-rotor unmanned aerial vehicle (UAV) can obtain farmland information quickly, efficiently and accurately. But as an under actuated system, the flight stability of multi-rotor UAV is susceptible to natural wind, electromagnetic interference and the near surface factors in farmland environment. The flight stability control method is important in multi-rotor UAV flight and affects qualified information acquisition. In this paper, multi-rotor UAV was adopted as research object and its body coordinate system and navigation coordinate system were established. Based on its motion analysis, changing 4 motors speed can realize multi-rotor UAV attitude regulation. The multi-rotor UAV platform consisted of brushless motors, electric speed controllers and composite-fiber fabric propellers. The flight control system was designed based on STM32F407 as master controller, MPU6050 as motion sensor integrated with 3-axis accelerometer and 3-axis gyroscope, AK8975 as 3-axis magnetometer. The attitude of multi-rotor UAV was measured and computed by the sensors above. The timers in the controller were used for capturing the input signals from remote control and generating PWM output signals for motors control. Multiple tasks including attitude measurement remote control input process, attitude stabilization management and motors control output were scheduled by task scheduling method in the control system. The mathematical model of multi-rotor UAV attitude control was established. Through matrix calculation, the multi-rotor UAV attitude angle and throttle control inputs were mapped to each motors speed control. Then the control principle applied in this study was explained. The double closed-loop proportional integral differential (PID) control strategy with angular velocity as the inner feedback loop and angle as the outer feedback loop was proposed. A multi-rotor UAV experimental platform was built to gain the proper PID control parameters of inner and outer control loops through engineer debugging method. The double closed loop PID control method was further improved by expert control strategy. The expert control rules included throttle input ratio definition, angle and angular velocity integration limitation, angle differential control parameter variation, input and output control limitation. By introducing the expert rules, the control parameters were diverse to be adapted to the multi-rotor UAV attitude change. Anti-interference tests and step response tests were taken to testify the designed control system on the experimental platform. In the traditional PID control, when interference angle increased, the rise time and the adjustment time of the system increased. But under the effect of variable derivative, when the interference angle became large, the rise time did not increase. The rise time of the system was less than 0.27 s. When the system was subjected to 30° interference angle, the adjustment times for roll angle, pitch angle and yaw angle restored to balance were less than 3.4 and 4 s respectively. In the step response tests, rise time, maximum overshoot, adjustment time and oscillation frequency of the system were recorded. According to the statistics, the maximum adjustment times for roll angle, pitch angle and yaw angle were less than 2.2 s and 3.4 s respectively. It proved that the double closed-loop PID expert control strategy adopted in this paper made the multi-rotor UAV have quick response, small fluctuation and stable control performance. Rice breeding base was chosen as outdoor farmland circumstance to test the multi-rotor UAV attitude control performance. Because the multi-rotor UAV flight cannot avoid wind interference in outdoor, higher inner loop proportion value, outer loop proportion and differential value in roll and pitch control made the multi-rotor UAV more agile, responsive to control input and stronger resistance to wind disturbance. I [ABSTRACT FROM AUTHOR]

In order to overcome the problems of low and non-adjustable resolution existing in wireless images sensor nodes applied in agricultural images acquisition at present, a wireless image sensor node with real-time adjustable resolution was designed and realized in this paper. The node was composed of an image acquisition module, a processor module, a wireless communication module and a power module. The node needed to not only capture, compress, and transmit image data, but also perform multiple task schedules and network protocols, so a powerful ARM (advanced RISC machines) processor S3C6410 was chosen as the processor module of the node. Considering the cost and power consumption, a CMOS (complementary metal oxide semiconductor) type image sensor chip was chosen to design the image acquisition module of the node. The design of image acquisition module included image sensor PCB (printed circuit board) design, chip pin interface design, appropriate lens selection, and development of the sensor chip driver. In order to monitor a larger area of the crop and remotely transmit crop images, the node integrated a WiFi (wireless fidelity) or 4G (the 4th generation) module. A solar power supply system was designed to make the node work stably in the field for a long time. To ensure the stability and reliability of the node, the powerful embedded Linux operating system was employed as the software development platform, and a modular designing method was adopted to program the software system of the node in C/C++ language based on this platform. In order to realize real-time adjustment of the resolution, an algorithm of resolution real-time adjustment based on driver layer and application layer collaboration and multi-thread concurrence was proposed, and all the functions of resolution real-time adjustment of image acquisition, image compression and image transmission were realized in the application layer of software system. In order to verify the performance of the node designed, a series of tests were conducted in Cencun experimental base of South China Agricultural University and Guangdong Dongsheng Farm (Panyu) from April to September in 2016. In the tests, 7 nodes were deployed in the farmland to form an acquisition and transmission network based on WiFi and 4G technologies. To ensure the nodes work stably in the field, where the climate was changeable and the infrastructure was absent, the nodes were encapsulated in a waterproof spherical shield, and a solar panel plus rechargeable batteries was used to supply power for them. The nodes were tested from the aspects of multi-resolution capability, real-time adjustment capability, image acquisition and transmission performance (transmission time and packet loss rate), and the availability of node energy. The test results indicated that the node had 7 different resolutions and its highest resolution was up to a pixel of 5 M, and more importantly, it could adjust its resolution in real time under the control of a remote user, then capture images with different resolution, and finally transmit them to the remote server. The time consumed to capture, compress and transmit 4 images with different resolution of 640×480, 1280×1024, 2048×1536, and 2592×1944 was 4.67, 8.77, 15.38 and 22.74 s respectively, and the average transmission packet loss ratio of 4 images was less than 1%. The tests validate the node designed in this work can capture crop images with different resolution in real time and transmit them remotely, and satisfy the requirement of different users for different crop image precision. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Physical Education / Tiyu Xuekan is the property of Journal of Physical Education Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

UAV (unmanned aerial vehicle) is widely used in modern agriculture because of its various advantages. But it is difficult to detect flight performance and the accuracy of human eye observation is poor. In order to monitor UAV flight status and assess performance of UAV automatically, this paper designed a UAV flight status real-time monitoring and performance evaluation system based on the LabVIEW. The system could be separated to airborne parts and ground parts; airborne parts included information collection module and wireless communication module, and ground parts included wireless communication module and monitoring software. The information collection module used AHRS IG-500N to obtain UAV flight status which consisted of triaxial attitude angle, triaxial acceleration, triaxial angular velocity, triaxial speed, GPS (global positioning system) latitude and longitude, GPS altitude, temperature and barometric pressure. After being preprocessed by MCU STM32F103ZE which converted hexadecimal data to ASCII, these data were sent to the ground computer through a pair of wireless transmission module GE MDS EL 805. The monitoring software based on the LabVIEW extracted these data through serial port for the maximum and minimum filtering. Then it displayed the real-time triaxial attitude angle and flight altitude, and used three-dimensional model created by Solidworks to simulate the real-time attitude of the UAV. In addition, it used Gauss-Kruger projection transformation to transform the latitude and longitude coordinates into the corresponding geodetic coordinates. By accumulating three-dimensional space between adjacent points of real-time trajectory of UAV, the software could calculate air miles. The distribution density of points on the whole original setting route was not uniform, and the software used a setting distance to process the route in order to get a uniformly distributed setting route. It could reduce the computation load and improve the accuracy of flight path deviation calculation. The software displayed the real-time route and the setting route of the UAV in one control at the same time, so the users could clearly see the difference between them from the system. The flight path deviation was the minimum distance between the real-time position and the corresponding position of setting route. By comparing the minimum distance and the offset distance between the real-time position and the corresponding position of the setting route, the system could also achieve and graphically display the flight path deviation of UAV. It showed the rest of the information as real-time value and saved all the data during the test. The system was tested in a university in China on September 15, 2015. The size of the test field was about 50 m × 70 m, and the coordinates of the test field were 23°09′76″N and 113°20′37″E. The UAV used in this test was WSZ-1805 electric octocopter which was designed for plant protection. The flight operator should control the UAV taking off, flying along the setting route, flight altitude keeping, hovering at a special location, and landing at another special location through vision. Results of the visual control test showed that the system software could display all the information clearly, the distances between the flight operator and the UAV were between 25 and 40 meters, the flight path deviation reached 5.2 m, the average position deviation of hovering reached 6.4 m, the average altitude deviation of height keeping flight reached 0.9 m, the fluctuation ranges of roll angle and pitch angle were both within 8°, and the temperature of the sensor dropped by 2℃ during the whole test. Outputs of the monitoring software were the same as the results of data analysis. The system is stable and reliable. It can be used to monitor, display, evaluate and record the flight status of the UAV real-timely. It can improve the accuracy of UAV flight status monitoring, and provide reference for further scientific assessment of UAV flight performance and training UAV flight operator. [ABSTRACT FROM AUTHOR]

Analyzing the multispectral images of sensitive bands of crops obtained through multispectral image acquisition devices, has currently become an important means to assess the growth status of crops. However, the existing multispectral image acquisition devices have some shortcomings, such as expensive in price, huge in volume, low in resolution. Further, it is labor-intensive and timeconsumed to carry the device to reality environment. To this end, a low cost and high resolution multispectral image remote acquisition node is designed in this paper, and it is deployed in a field to capture multispectral images of crops in real time which are remotely transmitted to the server in order to achieve continuous monitoring for the growth status of crops. The designed node can simultaneously capture RGB images and spectral images in 3 different bands with the resolution of up to 5 mega pixels, and its filters are replaceable. Thus, the node can be deployed in different environments to capture images of different crops. The system control module of the node is constructed by integrating a lowcost highperformance S3C6410 chip produced by Samsung Electronics Co., Ltd, and a peripheral circuit designed by ourselves. The multispectral image acquisition module of the node is constructed by combining a CMOS image sensor OV5640 with a mechanical filters switching device designed by ourselves. To transmit the images remotely, a third generation (3G) module is integrated into the node, which communicates through 3G wireless networks widely used in China. S3C6410 is a low cost chip, OV5640 as a CMOS sensor is much cheaper than CCD sensors, and the mechanical filters switching method is much cheaper than others, so the cost of the node is inexpensive. To ensure the stability and reliability of the node, the powerful embedded Linux operating system is employed as the software development platform. And based on this platform, a modular designing method is adopted to program the software system of the node, realizing the drive control of the filter switching device, capturing images periodically, compressing images and transmitting images through 3G networks in C/C++ language. In order to verify the performance of the node, the node is deployed in a farmland for a series of experiments. To ensure the node works stably in the field, where the climate is changeable and the infrastructure is absent, the node is encapsulated in a waterproof spherical shield, and a solar panel plus rechargeable batteries are used to supply power for it. The experimental results indicate that the node can automatically capture RGB images and images of 3 different bands of 550,0 and 800 nm, and transmit them to the server through 3G wireless communication networks.The total time consumed to capture and transmit 4 images with a size of 133 kB is about 45.27 s.Aiming at the package loss problem arising in experiments, an image automatic retransmission mechanism is designed based on selective repeat ARQ (Automatic Repeat reQuest) protocol, which makes the package loss rate dropped to 0.54%, realizing the reliable transmission of images. The experiments validate the node designed in this work can capture multispectral images in real time and transmit them remotely, and satisfy the requirements of multispectral image acquisition in real agricultural field environments. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Modern Biomedicine is the property of Publishing House of Progress in Modern Biomedicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Progress in Modern Biomedicine is the property of Publishing House of Progress in Modern Biomedicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)