Design And Test Of Orchard Multifunctional Opreating Platform With Four-wheel Independent Drive

The agricultural production in hilly areas of southern China is mainly focused on economic crops such as fruits.However,large-scale agricultural machinery were not suitable for the production operation in areas with non-standardized orchards layout.Generally,the miniaturized agricultural operating platform can realize different agricultural production by carrying different operating equipment,and it is widely used in hillside orchards due to its powerful versatility.However,currently traditional work platforms still have drawbacks such as complex structure and insufficient steering ability.To address these issues,in this paper,a multifunctional operating platform with four-wheel independent drive was proposed,and the operation performance of operating platform was analyzed by tests.The main research contents are as follows:(1)The design of whole machine structure of the operating platform.Compared with traditional external motor and reducer connection,four hub motors were used as drive components,simplifying the mechanical structure of the operating platform,and improving the overall drive capability.Four steering motors were used as steering components,enabling the platform to have a smaller steering radius and more driving modes through four-wheel independent steering.The finite element models of the key components were established by ANSYS and the static analysis was completed.The results showed that the design of mechanical structure was reasonable,and the stress and strain were both in the safe range.(2)The design of walking system of operating platform.STM32 single chip microcomputer was used as the main control module to realize the motion control of the operating platform.Four frequently-used steering strategies were used to adapt to motion requirements in different working scenarios,including all-wheel steering,in-place steering,Ackermann steering and four-wheel active steering.The maximum steering angle of the designed Ackmann steering was 30°,and the maximum steering angle of the four-wheel active steering was 25°.The motion models under each steering strategy were established and the corresponding control strategies were designed.The design of the remote-control system of the operating platform was completed.The function of remote control and the switching of the movement mode of the operating platform were realized.(3)The design of autonomous leveling system and following system.Aiming at the operation scene with strict horizontal requirements,the automatic leveling design of the operation platform was realized through the cooperation of the angle sensors and the electric push rods.The leveling angle ranged from 0° to 10°,which basically met the orchard application scene.In order to improve the agricultural production efficiency and reduce labor costs,the autonomous following function of the operating platform was designed.The three-dimensional positioning algorithm based on the ultrasonic module was used to capture the following target position,and the linear following,turning following and emergency obstacle avoidance strategies were designed to realize the fixed distance following function of the operating platform.The linear following speed of the operating platform was set to 0.63 m/s,the steering following angle was set to 10°,and the safety distance was set to 1 m.When the following distance was less than 1 m,the emergency obstacle avoidance function was activated to ensure the safety of the following mode.(4)The trial production of prototype and the design of related performance tests.The load performance,ramp performance,steering performance and braking performance of the operating platform were designed.The results showed that the operating platform could run normally under the predetermined load of 50 kg.Within the normal driving speed range,the operating platform can run on the 10° ramp.The minimum steering radius of the operating platform was 1.53 m in Ackerman steering mode and 0.95 m in four-wheel active steering mode,which met the requirements of the orchard working environment.In order to check the response time and distance,the remote-control system was tested.The results showed that the response distance of the remote-control ranged from 0 m to 50 m,and the response time was less than 0.2 s at the remote-control distance of 20 m,which met the actual demand.For the following system,the following logic was tested by ultrasonic three-dimensional positioning accuracy tests.The results showed that the accuracy of ultrasonic localization algorithm was 0.03 m,which met the following conditions.