| In the process of rapid development of modern agriculture,precision sowing technology is becoming more and more important.Precision sowing technology requires the seeder to accurately control the sowing depth,sowing amount and plant spacing,so as to ensure that crop seeds are reasonably distributed in the field soil.Among them,the uniformity of sowing depth affects the emergence rate of crop seeds.Sowing depth uniformity is also an important condition to evaluate the sowing quality of the seeder.Most of the traditional seeder adopts the spring as the control mechanism,which has gradually been unable to meet the sowing operation requirements under the high-speed operation of modern agriculture,so the active molding mechanism is needed to improve the stability of the seeding depth.At present,the developed sowing depth control system mainly has some problems,such as the lack of accurate data collection in the monitoring part,most of the measurement models adopt the measurement value of a single sensor,and the downpressure execution device is complex in structure,inaccurate in execution,and not timely.In order to solve these problems,A set of seeding depth control system has been designed.By establishing the seeding pressure measurement model as the theoretical basis for the control system,fuzzy algorithm is added to the system to control the seeding monomer to apply more accurate sowing pressure,Thus,the uniformity of seeding depth was increased.The concrete research contents are as follows:(1)Based on the comparison of the type of sensor,the principle of application,the merits and demerits,the inclination sensor is adopted as the shaft pin Control system sensor.Analysis of the mounting position of the sensor,and the final determination is that the tilt sensor is mounted on the deep limit arm,and the shaft pin sensor is installed at the place of the connection between the seeding depth adjusting mechanism and the sowing single frame.Through the analysis of the hydraulic device,pneumatic device and electric push rod,determine that the seeding pressure execution device of the control system adopts the electric push rod with simple structure,high accuracy and faster response speed;conduct the force analysis at the sowing unit limit arm and four links,and the range of the sensor and the electric push rod are determined.(2)Establish the sowing pressure measurement model through the static experiment,the theory foundation of the planting depth control system is provided.The model determining factor(R2)is 0.958 and the RMSE is 28.3 N.Finally,the precision of the model is validated through the static experiment.Experimental results indicate that the absolute value of the model error is25.3 N,and the largest is 2.8%.(3)In order to make the sowing depth control system to achieve more accurate control effect,In the control system,a fuzzy algorithm is added,so that the ground pressure can be accurately adjusted,to ensure a more stable consistency of Seeding depth.Through the simulation experiment,the performance of the control system has been verified.The test results show that the change pattern of the output response curve meets the regulation requirements of the sowing pressure,and the control system can timely adjust the sowing pressure with the change of the sowing depth.(4)In order to verify the effect of the control system on adjusting the sowing pressure,the indoor and field experiments were designed.The performance of the system was evaluated by processing and analyzing the test data.The system response test data show that by adjusting the sowing depth of 0~50 mm,the control system can be adjusted at 0~1005 ms,which can meet the control requirements of the control system.The field test data show that the qualified rate of seeding depth of active imitation mode is obviously better than that of passive imitation mode,In the active imitation method,the minimum qualified rate of sowing depth is 98.5% at the speed of12 km / h,and the qualified rate of sowing depth controlled by the control system meets the national standard and is 90%.At different operation speeds,the mean difference of the pass rate of sowing depth is not more than 1%,and the mean difference of the variation coefficient of sowing depth is not more than 0.2%.The minimum value of qualified rate of seeding depth of passive imitation mode is 89% at the speed of 12 km / h,which is 9.5% lower than that of the active imitation mode.Under different operation speeds,the mean difference of qualified rate of seeding depth is 8.84%,7.84% higher than that of the active imitation method;the mean difference of variation coefficient of seeding depth is 5.18%,4.98% higher than that of the active imitation method,and the coefficient of variation increases. |
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