Zhang Wenzhao

A liquid DP flow sensor on straight pipe

To detect water and pesticide flow rate for variable-rate spray, a new type liquid Differential Pressure (DP) flow sensor was introduced in this paper. The main problem that we attempt to solve was on-line flow measurement, to know the flow each moment and adjust pesticide to a desirable flow in the spray system. This new DP flow sensor is composed of a straight pipe with two branch pipes (an upstream branch pipe and a downstream branch pipe) in two ends and a DP sensor. A pressure difference between the upstream branch pipe and the downstream pipe is detected and converted into a voltage signal by the DP sensor. This voltage signal is transmitted to a microprocessor to determine liquid flow rate. Using water as working fluid, the liquid DP flow sensor at a certain dimension has been tested at the temperature of 22.0°C.The experimental results have shown that the presented device is satisfactory to variable sprayer with the measurement errors less than 1%. This liquid DP flow sensors advantage is simple in structure.

Design of flow control system on sprayer

This paper presents an on-line flow control system for variable rate spray based on LabVIEW. To solve the control problem of micro-flow or low flow on pesticide in the course of variable rate spraying, a variable rate control system was developed with a NI DAQ, a flowmeter, an electronic control injector of vehicle, etc. The characteristics of the flow control system, such as development platform, fuzzy control, PID algorithm, PWM, temperature property, response speed and so on verify that it is much better than that of traditional architecture exploitured by single chip, and it is good linearity between flow of the injector and PWM dutyfactor, the flow rate will automatically change with the variation of dutyfactor at the fix frequency. Experimental results show that this flow controls system has an advantage over other control system.

Fuzzy Control Implement of Micro-flow Control System

In the real-time mixing pesticide of the Variable Rate Spay (VRS), In order to detect and control micro-flow of pesticide, a micro-flow control system and fuzzy control arithmetic were designed with Differential Pressure (DP) flow meter, Electrical Control Injector (ECI) and microprocessor. Using water as work fluid, at 20¿, the control system was tested. The testing results show that static errors is ±5% at the range of 0 ~ 0.9 mL/s, the response time is 0.25s, the steady errors is ±2% at dynamic response test when initial value is 0.1mL/s and final value is 0.5 mL/s.

Structure and dimension optimizing on DP micro-flowmeter

In order to acquire higher sensitivity and stability for the Differential Pressure (DP) flowmeter, the structure and size were optimized on the DP flowmeter. Throat throttle, straight pipe and Venturi tube, the three types of DP flowmeter were contrasted and analyzed. The Venturi tube type is the most sensitive. The relation between inner diagram and flow rate was analyzed and calculated for micro-flowmeter, an optimum range of flow rate for a certain inner diagram pipe is ascertained while fluid flowing stably.

Precision Man-made Fruiter Modeling and Application

Man-made fruiters provides a fixed and standard object in the ground-based leaf area index(LAI) and biomass measurement for avoiding time and space effect on the real fruiter in the real environment. Firstly, the coordinates of the real guavas leaves and branches were gained by 3D digitalizer named Fastrak. Secondly, a man-made guava was made with a kind of special simulating techniques which has been applied for Chinese patent. By means of digital pictures, coordinates of leaves and braches and virtual guava, the man-made tree has been adjusted many times over 3 months to reach the simulating effect. Finishing the work, the man-made tree was compared and analyzed with the real one in parts such as coordinates, height, area, shadow area and so forth. As a result of analysis by SPSS, for the man-made guava the R square between tree height and accumulative leaf area is 0.9892, and the R square between shadow area and accumulative leaf area is 0.9973. Additionally, for error analysis between the real one and the man-made one, the profile is basically the same by comparing digital pictures in different visions and the profile size error is less than 3%; the coordinates of leaves obey the normal school after analyzing 3014 leaf points and 9042 coordinate points; the accumulative leaf area error is less than 5% and shadow area error is less than 20% from 0 to 65 cm of the tree height.

Method of indirect measurement of fruiter biomass

Fruiter biomass is one of the crucial parameters for precision spraying. This paper is to research measurement method for ground-based fruiter biomass by integrating direct and virtual plant technology based on real guava. Firstly, a real guava fruiter with 274 leaves and 228 branch segments was selected and its leaves and branch segments were encoded. Secondly, the coordinates of the guavas leaves and branches were gained by 3D digitalizer named Fastrak produced by Phohelmes and then a virtual guava model with a virtual direct beam environment was built by VC++ with OpenGL. Meanwhile, the guavas leaf parameters such as length, area, wet weight, and dry weight and branch segment parameters such as length, diameter, wet weight, and dry weight were measured by direct methods. Hereinto, a kind of useful leaf area process method was outlined for dealing area detection with different sides and holes .Using a kind of shadowing method, virtual guava could be shadowed in different horizontal height or in different vertical width and its shaded area, total biomass and so forth in different layers were calculated by integrating real guavas parameters. After regression analysis using SPSS, for the real guava the R2 between total leaf area and leaf dry weight is beyond 0.988 with the near regression formula between direct method and virtual plant method, the R2 between total leaf dry weight and branch dry weight is 0.89, the R2 between branch diameter and leaf dry weight is 0.80, the R2 between branch D2H(diameters square multiply height) and leaf dry weight is 0.97. And in the virtual fruiter, the R2 between leaf area and leaf dry weight is beyond 0.95, which proved the relation in the real tree. Additionally, more detail relations like height and leaf area, leaf shadowed area and leaf area were analyzed in the virtual fruiter data which provided important information to build a LAI and biomass calculation model.