| Flow measurement is the necessary method to improve irrigation water utilization efficiency.The flow measurement method based on the relationship of velocity-area is widely used in irrigation channels,in which the information of water level and velocity of channel is particularly important.Based on the study of the measurement technology of water level and velocity in irrigation canal,this paper explores the measurement system of water level and velocity in irrigation canal which combines embedded technology and machine vision technology.The main research contents and achievements are as follows:(1)Research on water level measurement technology of laser water-level gauge(LWLG).According to the actual application demand of water level measurement in irrigation area,the LWLG is designed with a laser rangefinder with the accuracy of 1 mm,a head shell,a measuring cylinder and a laser reflecting plate,etc..A control circuit board is designed,which mainly controls the LWLG to collect the data of water level and save it in a SD card,and communicates with the video capture module.In order to reduce the power consumption,solar charging plate is used to supply power for the system.Besides,the power management module is designed by ATtiny25 and MAX1658 switching regulators.The module reduces the power consumption of the system by timing power supply.The water level measurement test was carried out in a trapezoidal channel.The LWLG is calibrated with a water level probe(an accuracy of 0.1 mm).Compared with the measured data of water level probe,the maximum measurement error of LWLG is less than 5 mm,and the mean error is 1.4mm.The results show that the LWLG can measure the water level with high precision.The coefficient R~2 is 0.9994,and the fitting slope is 0.9992.It shows that the measurement results obtained by these two methods have high consistency.(2)Research on flow velocity measurement technology based on machine vision technology.A Raspberry-pi and a high definition camera are used to collect water flow video.The camera is calibrated and the velocity conversion model is built.The Farnberck optical flow method is used to calculate the moving distance of water flow ripple of each frame.Through the analysis of velocity components,it is found that the velocity along the flow direction has the greatest influence on the velocity.The flow velocities along the main flow direction are extracted and superposed to obtain the average flow velocity on the flow surface.A velocity meter with an accuracy of 0.001m/s is used to measure the velocities of three typical region of water flow surface.The maximum average relative error between the measured results and the adopted algorithm is 6.5%,and R~2 is not less than 0.8.The results show that the method can be used to measure water surface velocity with high accuracy.(3)Design of website of channel water level and velocity measurement system.In order to facilitate the staff’s remote viewing of information and data download,taking into account the low computing power and large power consumption of Raspberry-pi.The algorithm of flow rate calculation is transplanted to the cloud server,and the cloud server website is built to realize cloud computing and website publishing.The main function of velocity calculation algorithm is to extract and calculate the velocity distribution through the water level and flow video uploaded by Raspberry-pi.At the same time,we use the existing research results to preliminarily calculate the flow information,and insert the water level,flow rate and flow information into the My SQL database of the website.Build Nginx server in ECS,and upload the data of calculated water level,flow rate and flow to My SQL database.HTML+PHP is used to develop the web page to display the information of water level,flow rate and flow which can be viewed and downloaded by customers remotely.In this paper,the laser water level meter and the channel surface velocity measurement system have preliminarily achieved the function and goal of water measurement in irrigation area.However,due to the tight time,heavy workload and the impact of epidemic situation,there are still many aspects to be further improved in this system.(1)The control circuit of the laser water level instrument and video acquisition module are designed in the system.In the next stage,the two parts need to be combined to simplify the circuit and further reduce the cost.(2)Because the relationship between the surface velocity and the average velocity of the cross section is very complex,the research in this paper is not enough in-depth.Therefore,the next step is to analyze the relationship between surface velocity and cross-section velocity through hydraulic knowledge and to model the calculation of flow.We also need to carry out the corresponding water level and velocity measurement experiments,and further debug and improve the system. |
