| At present,there are few special machinery researched and put into production for buckwheat harvesting;the existing harvesting methods are mechanized,the degree of automation is low,and the work intensity of the operators is high.In the process of combine harvesting,the height of the header is not adjusted in time and the wheel speed ratio λ between the reel rotation speed and the forward speed is unreasonably selected,which often leads to problems such as large loss of the header and the header touches the ground.This article aims to design an automatic control system for the header of a buckwheat combine harvester to eliminate the manual operation of the header.It has certain reference value for the development of automation and intelligence of buckwheat combine harvester.The main contents include:(1)It is verified through experiments that the measurement accuracy of the M18 ultrasonic sensor meets the measurement needs,and the data calculation shows that the opening and expansion angle is15.2°.A telescopic drum anti-interference device is designed,an indirect measurement device for the height of the header combined with an ultrasonic sensor and a mechanical profiling mechanism.The length of the profiling mechanism is 560 mm,the range of up and down movement with the height of the header is 300 mm,and the corresponding ultrasonic measurement range is 90 mm.The telescopic imitating interference device has a diameter of 50mm;it effectively solves the problem of interference in the measurement of ultrasonic sensors.The height adjustment of the header is realized by installing an electromagnetic reversing valve on the existing header lifting hydraulic system.(2)Design of signal conditioning circuit and software system for height measurement and control of header.The power supply conversion circuit of the controller and the ultrasonic sensor,the electromagnetic reversing valve drive circuit and the signal conditioning circuit that linearly convert the analog quantity of the ultrasonic sensor from 0 ～ 5V to 0 ～ 3.3V are designed.A fuzzy PID controller for height adjustment of the header is designed.Under the step signal,the peak time of the system response is 0.75 s,the adjustment time is 2.5s,and the overshoot is 3.33%.Compared with the traditional PID algorithm control,the response speed is It has increased by 60% and overshoot has been reduced by 66.67%.It has better dynamic response characteristics and robustness,and is more suitable for controlling the height of the header in a field environment.(3)The work performance analysis of the reel mechanism and the design of the hydraulic execution system.Through the kinematic analysis of the reel mechanism,it is calculated that the wheel speed ratioλ=1.862 suitable for buckwheat harvesting is calculated.At this time,the range of the reel to the buckwheat support has no overlapping area,and the reel to the harvesting table in the horizontal direction.Maximum moving distance.The speed range of the reel is 110r/min and the torque is36N·m.The design of the reel hydraulic drive system and the selection of components have been completed through calculation.(4)Design of reel speed control system and software system.Use1024 incremental rotary encoder,quadruple frequency pulse counting technology and M/T method compatible with low speed and height measurement to measure forward speed and rotation speed.In the AMESim software,a hydraulic motor is simulated to drive the reel to rotate,and the system speed control function is simulated.The simulation results show that under the PID algorithm control,when the input is a step signal,the adjustment time of the system response is 1.5s,the peak time is 0.14 s,and the overshoot is 7.2%.The system has good robustness and fast response;input When the signal is a sinusoidal signal,the maximum error between the response and the input signal is 18r/min,and the followability of the system is good. |
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