| Grain drying is a key part of the grains post-harvest processing.After harvesting,the moisture content of paddy rice is high.In order to prevent mildew and deterioration of paddy rice,it should be dried in time.Currently,mechanized hot-air drying is the main drying method to dry paddy rice timely.However,due to the lack of drying quality dynamic prediction and drying parameters optimization,most grain dryers use constant temperature drying mode.The paddy drying process is not optimized and controlled.As a result,the quality of paddy rice after drying is poor.It affects the economic benefits of the paddy rice production industries.Therefore,the research and development of a paddy rice drying process intelligent control strategy and system are of great significance.It will increase paddy rice production,increase farmers’income,improve rice quality,and promote the development of large-scale agricultural operations.The head rice yield is a key quality parameter for determining the grade and price of paddy rice after drying.In order to increase paddy rice head rice yield after drying,this paper carried out the research on the paddy rice drying process intelligent control technology which was based on the established paddy drying process evaluation model.The main research contents and results are shown as follows:（1）Research on prediction and evaluation model of paddy rice head rice yieldThe prediction and evaluation model of paddy rice head rice yield（HRY）is the basis for realizing the paddy rice drying process intelligent control.In order to explore the feasibility of establishing the paddy rice HRY prediction and evaluation model,this paper carried out an intermittent drying experiment on paddy rice samples of variety Nanjing 9108.The intermittent drying experiment adopted the paddy drying mode in which intermittent drying was inserted into constant temperature continuous drying.Intermittent drying is a drying mode of alternating drying and tempering.The influence of intermittent drying parameters on paddy rice HRY had been studied.After drying,the influence of intermittent drying parameters on the HRY was analyzed.AHRY prediction model,including partial intermittent drying parameters and their interaction terms,was established.The R~2of the established HRY prediction model 0.92.The HRY prediction model was shown to accurately predict the HRY in the intermittent drying experiments.In order to apply the established model to the actual intermittent drying process which includes multiple drying and tempering cycles,the HRY prediction model was revised based on the characteristics of intermittent drying.And then,the prediction and evaluation model of paddy rice HRY was established.In order to explore the effectiveness of the prediction and evaluation model of paddy rice HRY,the experiments of constant temperature intermittent drying and variable temperature intermittent drying were carried out on the padyy rice samples of Nanjing 9108.The experimental results showed that if the summary of predicted HRY changing value was bigger,then the measured HRY was bigger.It proved that adopting the paddy rice HRY prediction and evaluation model established in this paper to predict and evaluate paddy rice HRY was feasible.（2）Design of paddy rice drying process model predictive control strategyIn order to improve the paddy rice head rice yield after drying,the characteristics of the paddy rice drying process parameters rolling optimization were analyzed.Then,based on the prediction and evaluation model of paddy rice HRY established in this paper,the optimization objective function of paddy rice drying process model predictive control（MPC）strategy was constructed,and the rolling optimization process of MPC strategy was designed.Based on the maximum prediction time domain and the progress of paddy rice drying,three segmented optimal paddy rice MPC drying strategies were designed.These drying strategies were screened by simulation analysis.The maximum prediction time domain of optimal paddy drying process MPC strategy was the next three-step prediction.It was used to carry out the verification test of the paddy drying process MPC strategy.The performance of MPC strategy was compared with the constant temperature intermittent drying mode of50℃,55℃and 60℃.Experimental results showed that the designed paddy rice drying process MPC strategy could improve the HRY through rolling optimization of the paddy rice drying process parameters.The paddy rice intermittent drying processes under different application conditions have different drying requirements and restrictions.By modifying constraint part of the proposed MPC drying strategy,the ranges of drying parameters and the relationship during the drying parameters can be constrained to realize the real-time online optimization of these intermittent drying processes.（3）Design of grain dryer unloding auger controlling parameter optimizationstrategyIn order to apply the designed paddy rice drying process MPC strategy on the 15ton cross-flow batch type recirculating grain dryer,the parameter control principle of grain dryer paddy rice drying process was analyzed.The transformation relationship between the drying duration of the paddy rice drying process MPC strategy and the variable frequency control value of the grain dryer unloding auger was clarified.Based on the paddy rice deep-bed drying model,the design of grain dryer unloding auger controlling parameter optimization strategy was carried out.In the designing process of the grain dryer unloding auger controlling parameter optimization strategy,the deep-bed of the paddy rice in the drying zone of the grain dryer was divided into thin layers.And then,the drying time optimization process of converting the drying duration into the deep-bed drying time was designed.Variable frequency control value conversion process of converting the deep-bed drying time into unloding auger variable frequency control value was designed.Strategy feedback process of the strategy parameter feedback correction according to the moisture content error was designed.The grain dryer paddy rice drying experiment was carried out in Jiangsu Runguo Agricultural Development Co.,Ltd.The strategy feedback parameters were optimized based on the paddy rice drying experiment datas.The initial value of the strategy feedback correction parameter was finally determined to be 0.3409.（4）Field test of paddy rice drying intelligent control systemThe hardware and software of paddy rice drying intelligent control system are the basis for the application of the designed paddy rice model predictive control strategy in drying process optimization of the grain dryer.This paper takes the widely used 15ton batch type recirculating grain dryer as the research object.By analyzing the measurement and control requirements for online optimization of paddy rice drying process,the hardware and software of the paddy rice drying intelligent control system were designed.The hardware of the paddy rice drying intelligent control system is mainly composed of a host computer and a monitoring system.The host computer performs the real-time optimization of the paddy rice drying parameters.The monitoring system performs the drying process information collection and the actuators actions control.The software system of the paddy rice drying intelligent control system is mainly composed of an electrical system program and a host computer program.The software development adopts the modular development scheme.The functions of software mainly include the real-time monitoring of the drying process information,drying process parameters optimization and the real-time control of the actuators.The application effect of the paddy rice drying intelligent control system on the widely used 15 ton batch type recirculating grain dryer was tested in Jiangsu Runguo Agricultural Development Co.,Ltd.The test results proved that the drying effect of the paddy rice drying intelligent control system was better than the drying effect of constant temperature drying system,and the final average head rice yield was increased by 0.18%. |
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