Optimization of working parameters of soybean combine harvester

Abstract: At present, there are few soybean harvesters dedicated to soybean harvesting in China, soybean harvesting mainly uses rice-wheat combine harvester by adjusting parameters and replacing working parts, and it is difficult to improve the efficiency and working quality of the soybean harvesting because of adjusting working parameters irrelevantly. To solve the problems, this experiment used a series of field trials to explore the influence of various key working parameters on the quality of soybean harvesting operations, and tried to figure out the optimal combination of parameters systematically. According to three indexes-- loss rate, crushing rate and impurity rate, nine factors of forward speed, rotate speed of roller, threshing gap in threshing section, threshing gap in separation section, angle of deflector, rotate speed of fan, angle of wind plate, front opening of upper sieve and posterior opening of upper sieve were chosen. By adopting the box-behnken central composite response surfaces analysis, we conducted the response surfaces experiments with nine factors and three levels. Then we used design-expert to analyze the response surfaces and built three mathematical models about loss rate, crushing rate and impurity rate. The research showed that rotate speed of fan, threshing gap in threshing section, forward speed and rotate speed of roller were the four most indispensable factors that affected the loss rate. Moreover, the four main factors influencing the crushing rate were rotate speed of roller, threshing gap in threshing section, forward speed and angle of deflector. Angle of deflector, rotate speed of fan, angle of wind plate and posterior opening of upper sieve played a decisive role in impurity rate. The response surfaces method was utilized to analyze the effects of factor's interaction on loss rate, crushing rate and impurity rate, and the multi-objective optimization were conducted for the regression models to obtain the working parameters of best evaluation index. The working parameter combination of the soybean combine harvester with the lowest loss rate, crushing rate and impurity rate as constrains was thought to be optimal. In this model, the forward speed was 6.03 km/h, the rotate speed of roller was 452.02 r/min, threshing gap in threshing section was 24.93 mm, threshing gap in separation section was 20 mm, angle of deflector was 26°, rotate speed of fan was 1 261.63 r/min, angle of wind plate was 11.49°, front opening of upper sieve was 19 mm and posterior opening of upper sieve was 11.03 mm. Under this condition, the average values of loss rate, crushing rate and impurity rate were 0.24%, 0.86% and 0.13%. The results of verification experiment showed that the loss rate was 0.24%, crushing rate was 0.90% and impurity rate was 0.14% when the optimum parameters were adjusted to that the forward speed was 6 km/h, the rotate speed of roller was 450 r/min, threshing gap in threshing section was 25 mm, threshing gap in separation section was 20 mm, angle of deflector was 26°, rotate speed of fan was 1 260 r/min, angle of wind plate was 11.5°, front opening of upper sieve was 19 mm and posterior opening of upper sieve was 11 mm. The experimental value is in good agreement with the optimized value and the relative errors were 0, 4.7% and 7.7%. The research results can provide reference for structure improvement and operation parameter control of soybean combine harvester.