| Maize is one of the important food crops in China and can also be used as economic crops to provide raw materials for industry and animal husbandry.In recent years,precision seeding technology has been developed rapidly,which can achieve large-scale agricultural production,reduce seed waste,improve yield and land use efficiency.Precision planter is an important carrier to achieve high-quality seeding of maize.At present,most of the seeding drive methods of precision planters in China are mechanical ground wheel drive,and its shortcomings in operation efficiency and seeding quality stability are becoming increasingly prominent,which seriously restricts the further improvement of precision seeding efficiency.In order to improve the above problems,it is an effective scheme to achieve high efficiency and precision seeding under the premise of ensuring good seeding accuracy.In this paper,a single control system for maize precision electric drive metering is designed,which is suitable for high speed operation.The main research contents and conclusions are as follows:(1)A kind of electromechanical drive and seeding control system for high-speed precision sowing of maize was designed with STM32C8T6 as the controller,fuzzy PID as the core control algorithm of speed regulation,encoder as the feedback element and DC motor as the actuator.The overall hardware architecture is designed,and the hardware circuit schematic design of different modules is completed.The circuit simulation of the principle of the monitoring signal conditioning circuit is carried out.Finally,the PCB circuit board design is completed,the test shows that the signal transmission of each sub-controller module is stable and the functional integrity is good.(2)Through the simulation of DC motor speed control system,the results show that under the same step input conditions,the performance of fuzzy PID control system is better than that of conventional PID control.The control program of the control system is written,mainly including the detection of working speed and motor speed,fuzzy PID algorithm,CAN communication protocol program and human-computer interaction interface.After testing and optimization,each subroutine has good function and runs stably.(3)Through the static speed regulation test of the motor,it is determined that the PWM frequency is60 k Hz.Under this condition,the DC motor has high stability and linearity,and the three control parameters K_p,K_iand K_dare determined as 0.7,0.03 and 0.2,respectively.They are used as the initial values of the fuzzy-PID algorithm.When the target speed of the motor is 1500 r/min,the overshoot,rise time,adjustment time and steady-state error of the fuzzy-PID speed regulation system are 0.53%,0.29 s,1.02 s and 4.97%,respectively.The four performance indexes of PID speed regulation are 0.93%,0.42 s,1.51 s and 6.13%,respectively.It shows that the steady-state error and dynamic response characteristics of PID speed regulation are significantly better than PID algorithm due to the fuzzy reasoning link;through the dynamic speed control bench test,it is determined that when the feedback period of the belt speed is T=1.0 s,the control algorithm has high speed control accuracy and good robustness under this condition.(4)The test bench results of seeding performance showed that the seeding performance indexes of the two control methods had little difference when the operating speeds were 8 and 10 km/h.When the operation speed is 12 km/h,compared with the conventional PID control method,the qualified index of fuzzy PID control method is more than 93.04%,the reseeding index is less than 5.13%,and the missing sowing index is less than 1.83%;qualified index increased by 2.50 percentage points,reseeding index and missing sowing rate decreased by 0.85 percentage points and 0.88 percentage points,respectively.Each sowing performance index of fuzzy PID control mode is better than that of conventional PID control mode,which is suitable for high-speed sowing operation.The field experiment results show that the control system designed in this study has good function and stable operation,and the variability of seeding performance between monomers is small,which is suitable for high-speed precision seeding operation.This study can provide some reference for the improvement of efficiency and performance of high-speed precision maize planter. |
