Variable-diameter Drum For The Rice Combine Harvester And Adaptive Control Method For Threshing Device

Rice is an important food crop in our country.The combine harvester for mechanized harvest has become the main operation mode of rice harvest in China.As one of an important components of the combine harvester,the performance of thresher device determines the operation performance,efficiency and adaptability of the whole machine.For a traditional thresher device,the diameter of threshing drum and concave grid were fixed mostly.When different varieties of rice are harvested by the combine harvester,the actual feed rate fluctuates greatly during harvesting because the growth density of rice per unit area is not uniform,thus decreasing the performance of the combine harvester in terms of threshing and separation.The traditional thresher device cannot adapt to the optimal threshing conditions for different varieties of rice.In addition,the working parameters of the traditional thresher device are mostly fixed,and a real time adjustment based on the changes of the objects and environment is unavailable.Therefore,both the harvest efficiency and adaptability are poor.In order to develop a highly adaptive thresher device that can adjust the working parameters of the thresher device in real time according to different working objects and environmental changes,with the support of the National Natural Science Foundation of China,a study on variable-diameter drum thresher device for the rice combine harvester and its adaptive control method was carried out.The details were as follows:1.In terms of the adjustment principles and adjustment effects(concentric / nonconcentric threshing gap)for the threshing gap adjustment types available for existing thresher device(threshing drum adjustment type,concave adjustment type),the adjustment effect of threshing gap by drum adjustment type was better than by concave adjustment type based on the theoretically calculated threshing gap cross-sectional areas for the two adjustment types.Based on the theory of particle discrete element and linear viscoelastic mechanics,a stalk model of flexible rice was established according to the biomechanical characteristics of rice plant.A simulation analysis on the thresher device of concentric/non-concentric threshing gap was carried out in terms of velocity and displacement of materials,and the distribution of separated mixture as well,so as to reveal the mechanism of rapid transportation,threshing,impact,separation,and screening of materials in the thresher device,as well as the influence of working parameters under different feeding densities and the variation of threshing space(concentric/non-concentric threshing gap)on the performance of the thresher device.2.Through analyzing the structure characteristics and working parameters of the existing thresher device,a variable-diameter drum thresher device that can adjust the drum diameter as a whole quickly and infinitely in the working process was developed,so as to ensure the uniformity of the threshing gap.A new high strength threshing gear lever was developed,and a drum diameter adjustment device was designed based on the Archimedes spiral principle,so as to perform a force analysis on the diameter adjustment device for the variable-diameter drum,ensure that the design dimensions of the constant speed spiral disc and claw in the diameter adjustment device meet the self-locking conditions,and ensure the reliability of the diameter adjustment device effectively.The feasibility of variable-diameter drum was verified by field test,and the effects of two adjustment types on grain-entrainment loss rate,damage rate,threshing rate,and threshing power consumption were compared and analyzed.It breaks through the bottleneck problems in the traditional thresher device,e.g.,the threshing gap cannot be adjusted through changing the drum diameter when the rice combine harvester is in operation,the threshing gap has to be adjusted through changing the position of concave grid,which may result in unevenness of threshing gap of the thresher device and further impact the fluidity of materials in the thresher device,as well as the operation performance of thresher device.3.The test data under different working parameters of combine harvester and operation performance parameters of thresher device were obtained through a field test,and the correlation between operation parameters and operation performance parameters of thresher device was analyzed,the main factors influencing operation performance of thresher device were determined,and the mathematical model of variable-diameter drum thresher device was established.Through analyzing the advantages and disadvantages of the original cuckoo search algorithm in the search optimization field,an adaptive strategy that can dynamically adjust the search step size was added to the original cuckoo search algorithm.Furthermore,an adaptive cuckoo search algorithm was proposed based on the fuzzy control system of dynamic adjustment of discovery probability Pa.In addition,the test results of the original cuckoo search algorithm and the adaptive cuckoo search algorithm on the mathematical model of the variable-diameter drum thresher device were compared and analyzed.The adaptive control model of the variable diameter drum thresher device was established according to the adaptive cuckoo search algorithm,and the relevant simulation test was carried out.4,A variable-diameter drum thresher device and relevant adaptive control system were installed on the self-made combine harvester,real time controls of working parameters(speed,threshing gap and drum revolving speed)based on the changes in actual threshing performance(grain-entrainment loss rate,damage rate)fed back by sensors during operation of combine harvester were carried out using adaptive cuckoo search algorithm,and the operation parameters and performance indexes of the variable-diameter drum thresher device with and without adaptive control system were compared analyzed.The test results show that the adaptive control system for the variable-diameter drum thresher device effectively reduced the harvesting loss of thresher device for the combine harvester and improved the harvest adaptability.