Tree Canopy Information Detection And Air-assisted Target Spraying Machine Development Based On Laser Sensor

The mechanization of agricultural plant protection started late in China,and the extensive plant protection machinery based on manual operation has been used in most farmlands and orchards.Such extensive plant protection machinery has bad pesticide application effects,low operation efficiency,and serious droplet drift,which waste plenty of pesticides and pollute the soil and the water.With the development of sensor technology and automatic control technology as well as the continuous increase of environmental protection requirements,the precise pesticide application technology and equipment have become an urgent need for agricultural plant protection.In this research,the two-dimensional laser sensor was used to real-time collect and process the canopy information of the fruit plants,and the air-assisted target sprayer was researched and developed to improve the utilization rate of pesticides and reduce the pollution to the environment.The main research contents and findings were as follows:(1)A novel canopy volume estimation method for the fruit tree based on the irregular triangular prism module was proposed in this work.Five spherical landscape trees with regular canopy and ten citrus trees with irregular canopy were scanned by the laser sensor at the speeds of 0.5 m/s,1.0 m/s,and 1.5 m/s,respectively.The canopy volume was estimated by two methods:cuboid module method(CMM)and irregular triangular prism module method(ITPMM),and the error analysis was conducted based on manual measurement.The distance range of the relative error of the two methods for measuring citrus trees is-0.28%-4.22%,and the average difference is 1.78%.The distance range of the relative error of the two methods for measuring citrus trees is 6.43%-26.20%,and the average difference is 13.04%.The research shows that the estimation error of the ITPMM is significantly smaller than the CMM.For the same target,when the speed is 0.5 m/s,both of the estimation accuracies for the two methods are the highest.As the scan speed increases,laser scanning points on the canopy decrease.So,the relative error of volume estimation increases with the increase of scan speed of the laser sensor.The processing time of a frame laser data by the CMM is 2.86 ms,and the processing time by the ITPMM is 4.73 ms,which is less than the scanning period of 20 ms of the laser sensor.The data processing time can match the acquirement of real-time collection and processing of laser data.(2)The mechanical structure and control system of the orchard air-assisted target variable sprayer was designed and developed.The key equipment,such as gasoline engine,fan,water pump,valve,crawler,etc.,were selected.The transmission device of the engine,fan,and pump,was designed.The spraying system was calibrated,and the adjustment schemes for the mounting height and angle of the spray nozzle were proposed.Designed a scheme for the control system of the orchard air-assisted target sprayer based on the variable sprayer,which is composed of the upper-computer program flow controller module,speed monitoring module,temperature and humidity monitoring module,sprayer status monitoring module,spraying path recording system,etc.The sprayer positioned the scanning points based on the speed monitoring module according to the canopy features of the fruit tree scanned by the laser sensor;the flow controller controlled the electromagnetic valve switch based on PWM technology to realize the canopy-based variable target spraying.The upper-computer controlled the electromagnetic valve switch based on the canopy information scanned by the two-dimensional laser sensor,and the pesticide was sent to the canopy of the fruit tree through the secondary atomization of the pressure valve,the electromagnetic valve,atomization nozzle,and the fan,to realize variable spraying.(3)Spraying performance of the air-assisted target sprayer was tested.The results showed that spraying performance tests were conducted at the speeds of 0.5m/s,0.8m/s,and 1.0m/s,with the increase of the sprayer speed,the deposit point densities of the droplet on both the right and reverse sides of the leaves of the fruit plant with a bigger canopy was decreased gradually.When the sprayer traveled at 1.0m/s,the deposit point densities on the right sides of the leaves of the three trees were 78.16 pcs/cm~2,115.52pcs/cm~2 and 129.41 pcs/cm~2 respectively.While the deposit point densities on the reverse sides of the leaves of the three trees were 38.77 pcs/cm~2,56.50 pcs/cm~2 and 68.38 pcs/cm~2respectively.The deposit densities of the droplet at each place were all bigger than 20pcs/cm~2,and the deposit effect of the droplet on the right side of leaves was more ideal;the average particle size of the droplet carried on both the right and reverse sides of leaves of the three trees were 30μm-150μm.The adhesion effect of the droplet on the leaves was good,which could meet the requirements of the general test methods for plant protection machinery in the industrial standards and effectively protect fruit plants from diseases and insect pests.While deposit point densities of the droplet on both the right and reverse sides of the leaves of the fruit plant with a smaller canopy remained stable at different speeds.At the speeds of 0.5m/s and 0.8m/s,the average particle size of the droplet on the right sides of the leaves was bigger.This was because the sprayer speed was reduced,the spraying time per unit distance was increased,the small droplets were covered and the border positions of the droplet with large size intersected with each other and formed big drops.