Study On Key Technologies Of Laser-Controlled Paddy Field Levelling-Beater

Paddy field tillage is a major process of rice production.The precise tillage of paddy fields increases the utilization rate of manure and water,improves the uniformity of irrigation,reduces the number of weeds and pests,and relieves environmental pollution.Paddy field laser leveler can well realize precise levelling,Soil beating needs to be carried out prior to paddy field levelling,usually using manual-controlled implements such as a rotary tiller or beater.Very often,such manual-controlled implements cannot guarantee a consistent operating depth;an overly large operating depth may result in a tractor overloaded and shut down.In addition,such manual-controlled implements may fail to achieve the desired level of quality,damage the original underlying hard layer of the paddy fields（thereby resulting in an uneven hard layer）,and compromise the service life of the tractor and implements.Moreover,beating and levelling are usually carried out separately in paddy field,with levelling carried out after a certain period of sedimentation of the beaten soil.This results in a complex paddy field beating-levelling process and a long time interval between the beating and levelling operations.The separation of soil beating and levelling operations also contributes to larger investments in machinery and higher labour costs.Furthermore,additional operations of a tractor on a paddy field incur more damage to the underlying hard layer of the field.Therefore,it is of great significance to study precise levelling and beating technology,realize the precision levelling and beating of paddy field in one entry,shorten the time interval between flat ground and beating,improve operation efficiency and quality,and provide good field conditions for rice planting,so as to ensure stable and high yield of rice in China.This paper presents the design of a laser-controlled paddy field levelling-beater,This paper studies the levelling and beating technology,with the levelling mechanism mounted in front of the beating mechanism,designs a laser-controlled paddy field levelling-beater,studies the interaction rule between the levelling scraper and paddy field soil,studies the rapid acquisition method of the flatness of paddy field surface,and carries on the field experiment.The main research work is as follows:（1）The laser controlled paddy field levelling-beater designIn this paper,the principles of existed beating and leveling machines in the market were analyzed.The levelling-beating technology for paddy field was proposed,with the levelling mechanism mounted in front of the beating mechanism.The laser controlled paddy field levelling-beater was designed,and a grade adjustment mechanism,an automatic tilt adjustment mechanism,a levelling and beating mechanism,an automatic control system and a hydraulic system were designed.The front end of the grade adjustment mechanism is coupled with the three-point suspension mechanism of the tractor,and the rear end is coupled with the tilt adjustment mechanism.The grade adjustment mechanism and leveling mechanism could realize synchronous and independent adjustment of height and tilt of levelling beater.The levelling mechanism was installed in front of the beating mechanism.The levelling scraper would transfer the paddy soil from the higher part of the field to the lower part.The levelled soil would be beaten by the beating mechanism to meet the requirements of rice planting.The levelling mechanism is mounted in front of the beating mechanism through four tracks,and the levelling scraper relative to the beating mechanism can be lowered and raised through the stretching of the levelling shovel oil cylinder,so as to adjust the beating depth.The automatic control system could realize the automatic control of grade and tilt of the levelling beater.The hydraulic control system consists of three independent hydraulic circuits,which were used to control the height,tilt and set the beating depth of the levelling beater.（2）Establish and parameters calibration of discrete element model for paddy fieldThe discrete element model of paddy field soil was established.The slump height and expansion of paddy field soil were measured as test indexes.Nine parameters of paddy field soil were calibrated through simulation test.Plackett-Burman test was used to screen 9 parameters,and test results show that the soil-steel static friction coefficient（X₈）,soil surface energy（X₂）and soil-soil rolling friction coefficient（X₆）are of great influence on the test indexes.The optimal value interval of the above three parameters was determined by the steepest climbing test,and the second-order regression model of between the test indexes and each significant parameters were established according to the results of the quadratic general rotary combined design test.The optimal combination of significant parameters was obtained as follows:JKR surface energy0.808J/m²,soil-soil rolling friction coefficient 0.11,and soil-steel rolling friction coefficient 0.6.The optimized results were verified.The simulation test between particle size and test error was carried out.In paddy field,the soil particle radius was larger than 3mm,and the simulation test error was larger.It was shew that the soil particle radius in the subsequent simulation test should not be larger than 3mm.（3）Study on the interaction between paddy soil and levelling scraperDiscrete element simulation tests were taken to study the effects of the scraper height,the angle and the length of side plate on the performance indexes（resistance,vertical force and soil load）of levelling scraper.The results shew that the height of the scraper had no effect on the force and the amount of soil transported of the levelling scraper,while the Angle and the length of the side plate of the levelling scraper had significant and particularly significant effects on the force and the amount of soil transported the levelling scraper respectively.The reasons of its influence were analyzed.Through the weighted synthesis method,the optimal combination of parameters was obtained.In the test range,the length of side plate was 400mm,and the soil Angle was 60degrees,the comprehensive index was optimal.The optimal design tests of the levelling scraper were carried out according to the optimal parameter combination,and the optimal designed levelling scraper in the simulation test was verified by soil bin test.（4）Paddy field surface and beating bottom surface reconstruction and levelling-beating quality evaluationThe methods of paddy field surface flatness and beating bottom surface information collection were analyzed,Three methods of paddy field flatness information acquisition and its principle were analyzed,and paddy field flatness evaluation methods were studied.The data processing methods were studied.A flatness data acquisition test was carried out in the same paddy field using level,Z+F and Scanlook,the advantages and disadvantages of three methods of paddy field flatness were compared and analyzed.The results show that the scanlook acquisition method has the highest efficiency and precision,is a rapid precise surface flatness information acquisition methods.the methods of measuring the beating depth and evaluating the quality of the levelling beating quality were studied.An precise and efficient method for the levelling beater working quality evaluation was proved.（5）Experiment studyAuto leveling system experiment was taken in ridge vegetable lands.Experimental results show that the auto leveling close-cycle control system can keep rotary tiller working in a desired angle（0°）.the surface flatness by the auto leveling rotary tiller is improved significantly comparing to the non-leveling rotary tiller,the maximum height difference of the auto leveling rotary tiller in lateral direction is 1.9 cm,while the non-leveling rotary tiller is 9.8 cm;The tillage depth of auto leveling rotary tiller in lateral direction is more stable,the maximum height difference in lateral direction of the tillage depth is 1.8 cm,while the non-leveling rotary tiller is 9.7cm.The grade test results of the laser-controlled paddy field levelling-beater demonstrate that the operational quality of the levelling-beater is more stable when operating in automatic control mode than when operating in manual control mode.More specifically,the elevation of the levelling-beater varied±4 cm around the mean elevation when operating in automatic control mode.However,when operating in manual control mode,the elevation was greater than±11 cm.And the operation quality and elevation stability of the ground beating mechanism were improved significantly remarkably.The test results also demonstrate that the levelling-beating operation improved the flatness of the field by transferring soil in areas of higher elevations to areas of lower elevations under the action of the automatic grade control system.The test results show that the laser-controlled levelling beater remains within±0.5°chang.Paddy field flatness was improved significantly,the maximum variation of elevation was reduced from 25 cm before the levelling and beating operation to 10 cm after the operation.In addition,the standard deviation of the elevation was reduced from 4.1 cm to 2.1 cm after the operation.The total number of flatness sampling points with the absolute difference of the desired elevation less than or equal to 3cm was increased from 53.24%to 85.8%.The effective beating depth was14.13cm,compared with the set beating depth of 15cm,and the standard deviation of the beating depth was 3.27 cm.Scanlook method can collect the flatness of paddy field flatnessand beating depth measure efficiently and precisely.