Design Of Plant Factory High Level Harvest AGV Chassis And Control System

Plant factories represent an advanced stage of facility agriculture development.In recent years,they have experienced rapid growth due to their high spatial utilization in growing crops in three-dimensional spaces and their efficiency in year-round planned production.However,plant factories face challenges such as high labor intensity in manual harvesting,low operational efficiency due to the high planting density and multiple cultivation layers,and increased risks of plant infection from frequent human access.To address these issues,this study focuses on dynamic modeling,control method research,and structural optimization design to develop a chassis for a high-level harvesting AGV in plant factories(referred to as the harvesting AGV).This chassis enables stable walking,trajectory tracking,and automatic positioning,thereby enhancing the automation level of transportation equipment in plant factories.The main research work is as follows:(1)Research on the dynamics model of the harvesting AGV.The dynamics model of the harvesting AGV was studied under two conditions: one neglecting the influence of the omnidirectional wheels and the other considering their influence.The double-wheel inverted pendulum model was employed to describe the kinematic and dynamic laws of the chassis attitude motion for the harvesting AGV with a differential wheel system,assuming the influence of the omnidirectional wheels is ignored.When considering the influence of the omnidirectional wheels,a multibody kinematic model of the harvesting AGV was established based on the structural diagram of the multibody system.The dynamics equations were derived using the general equations of motion.The model parameters were determined,and a virtual prototype of the harvesting AGV was created to simulate and validate both the double-wheel inverted pendulum model and the multibody dynamics model.The validation results indicate that the multibody dynamics model provides higher accuracy in predicting the attitude of the harvesting AGV compared to the double-wheel inverted pendulum model.(2)Research on the driving control method of the harvesting AGV chassis.Based on model predictive control theory and sliding mode control theory,a control algorithm combining trajectory tracking and driving stability was designed.The influence of three different driving speeds,specifically 0.5 m/s,1.0 m/s,and 1.5 m/s,on straight-line trajectory tracking was compared.Simulation experiments were conducted on the driving control method of the harvesting AGV chassis,and the results showed that the lateral deviation of the chassis control method had an average value of 0.02 m,the yaw angle deviation had an average value of 0.06°,and it took 10 seconds to reach a steady state for the pitch angle with an overshoot of 0.15°.A model of the harvesting AGV drive wheel motor using the FOC(Field-Oriented Control)vector control algorithm was constructed,and the PI parameters of the FOC control algorithm’s current loop and speed loop were optimized.The torque output of the drive motor remained stable under step load and ramp load conditions.The experimental results showed that the variance of the drive motor current was reduced by 60.9% compared to before optimization,which was beneficial for reducing the vibration of the drive motor’s torque output.(3)Harvesting AGV chassis(including lifting)mechanical and control system design.The overall design of the harvesting AGV chassis mechanical system has been determined.A comparison was made between different drive wheel configurations,such as single-wheel steering,dual-wheel steering,differential wheel,and mecanum wheel,to assess their advantages and disadvantages.The drive system and wheel layout for the differential wheel configuration were chosen.The damping mechanism and chassis frame were designed,and the rationality of the selection of drive wheels and suspension springs was validated through virtual prototype dynamics and statics simulations,resulting in the optimization of the chassis frame structure.Based on a comparison of the advantages and disadvantages between the synchronous belt lifting system and the screw lifting system,the synchronous belt lifting mechanism and linear guide guiding mechanism were selected.The statics analysis of the vehicle frame and critical connection components was conducted to determine the lifting device solution.The maximum required driving wheel torque for the harvesting AGV was determined to be 9.12 Nm,which is lower than the maximum driving wheel torque of 17.19 Nm.The spring compression rate was6.9%,below the critical compression rate of 32%.The selection of mechanical components was reasonable,and the design and optimization results met the practical requirements of the harvesting AGV.The hardware design of the harvesting AGV chassis control system was developed.Data acquisition and processing methods for magnetic navigation sensors,drive motor encoders,and lifting motor encoders were determined based on the requirements of trajectory tracking control,stop positioning control,and lifting positioning control.The operational flow of the chassis control system and the lifting control system was established.(4)Prototype manufacturing and performance testing of the harvesting AGV chassis.A prototype of the harvesting AGV chassis(including the drive system)was manufactured,and performance tests were conducted to evaluate its stability during operation,trajectory tracking ability,stop positioning accuracy,and load capacity.The performance test results indicate that under different conditions,such as acceleration of 0.029m/s2,deceleration of 0.0314m/s2,and constant speed of 0.785m/s,the pitching angle of the harvesting AGV was less than 2.44°,and the rolling angle was less than 1.77°.During trajectory tracking,the lateral deviation was less than 1.35 mm,and the heading angle error was less than 0.336°.The maximum control error in terms of travel distance was 0.013 m.In the lifting speed range of 200mm/s,500mm/s,and1000mm/s,the maximum vibration displacement was 2.0mm,which meets the operational requirements.Based on the above research,the following is proposed as a driving control method for the high-level harvesting AGV chassis in a plant factory,which can meet the control requirements for trajectory tracking and vehicle stability of the high-level harvesting AGV in a plant factory.This method holds significant practical significance for improving the production economic efficiency of plant factories and promoting industry development.