| Installation agriculture is characterized by high humidity,high multiple cropping index,and serious occurrence of diseases and insect pests,which often requires high frequency application of pesticide.Traditional artificial spraying is easy to cause drug poisoning,pesticide residue,environmental pollution and a series of problems.Mechanization,intelligence and precision have become the main development direction of modern facility plant protection.In order to achieve the goal of"reducing the amount and increasing the efficiency"of plant protection,in this paper,a flexible mobile self-propelled electrostatic sprayer is designed and developed based on 4WID/4WIS chassis structure for the narrow operating environment in the facility,and developed the hardware and software system of autonomous walking and coordinated control of electrostatic sprayer.On the one hand,it can penetrate into the crop rows to achieve close distance and ultra-low amount of precise target application;on the other hand,it can realize field change between different greenhouses to save farmers’purchase costs.The main research work includes the following five aspects:（1）According to the requirements of spray operation in facility environment,the main technical parameters and design scheme of sprayer are determined.Complete the design of4WID/4WIS chassis structure and electrostatic spray system,determine the mechanical structure size of each part of the sprayer,design the damping structure,reducing the impact force transmitted to the fuselage due to vibration,and reduce vibration.The static analysis of chassis structure is carried out to ensure sufficient strength and stiffness.The key components of the sprayer were selected through theoretical calculation and the spray bracket was designed according to the parameters of the spray component.（2）In order to realize the autonomous walking and spraying operation of the sprayer in the greenhouse,the control system of the sprayer is divided into two parts;the chassis self-propelled control subsystem and the spray control subsystem.The master-slave control scheme is used to realize the control of the mobile chassis and the spray system.According to the functions and requirements of the sprayer,the hardware system of self-propelled spray control is designed and built.The interface circuit between the control unit and each driver is designed.The subsystems are integrated into the whole control system through standardized interfaces.（3）By analyzing the kinematic constraints of a single wheel,the overall kinematic model of the sprayer is established and analyzed.The 4WID/4WIS driving mode of the sprayer is analyzed,and the relationship between the deflection angle and the speed of each wheel is derived.The control scheme of the sprayer is analyzed,which provides a theoretical basis for the later motion control.According to the PID algorithm,the speed is closed-loop controlled to realize the real-time and stable control of wheel speed.Finally,according to the obtained path information and combined with the sprayer control scheme,the self-propelled controller converts the path information into the instruction to control the sprayer to complete the walking control of the whole path.（4）According to the specific functional requirements of the sprayer,the software design of the control system is completed based on the built hardware system.Design of wheel hub motor driver,and the communication between the self-propelled controller and the in-wheel motor driver was realized by transplanting CAN open official source code CAN Festival.Step motor driver design,send a fixed number of pulses to achieve step sprayer steering control;design the spray program,control the output PWM duty cycle to achieve spray flow regulation;acquisition of ultrasonic sensor signal,complete obstacle avoidance program design.（5）According to the above research content,the functional test of the sprayer was carried out in the laboratory environment to verify the reliability of the control system.The experimental results show that the motion control accuracy of the chassis is high,and the lateral error is between±0.5 cm,which meets the moving requirements.The average droplet deposition on the leaf surface was maintained in the range of 0.950–1.250μL/cm~2,and the change of droplet deposition at the detected points was small and the droplet distribution was uniform.The four-wheel independent drive/steering electrostatic sprayer developed in this paper integrates self-propelled function and electrostatic spray function,and realizes close and accurate target low-volume spray through in-depth crop rows.The turning radius of the whole machine is small,which is suitable for carrying out independent spray operation in a narrow greenhouse environment,reducing the use of pesticides and improving the utilization rate of pesticides.At the same time,because there is no need to lay track,truss and other infrastructure,it saves the purchase cost of farmers,and has good social,economic and ecological significance. |
