Study Of Rice Seed Sprouting Temperature Uniformity And PID Control In Cold Region

Temperature is the important factors that affect seed germination rate during seedbed seedlings ofgreenhouse after rice seed soaking and pregermination because crop growth period is short and anual activeaccumulated temperature is less in Heilongjiang province. When the temperature is too high the buds will beburned and too low the buds will be weak. Meanwhile, agricultural production cost will be both to increaseand affect the output of crops. Thus the uniform distribution of temperature field of rice has practicalsignificance in the process of rice seed soaking and pregermination. Now many farms in the heilongjiang landreclamation bureau used rice centralized seed soaking and pregermination method. That is, according to therequirements of rice cultivation measures and the growth characteristic of rice seed soaked, sprouting stage,using water as a heat conduction medium, the rice seeds realize these process such as heating, cooling,temperature control, heat preservation by water. Finally, achieving the object that the production process ofseed soaking, chest and pregermination in standardization and mechanization is finished one time. The finiteelement method is used to analyze the temperature field of rice seeds in pregermination process of rice seedsoaking and pregermination equipment in this thesis, acquire the temperature field distribution rule of seed boxin rice seed soaking process, and verify the correctness of the theoretical analysis through actually heatingprocess; based on the neural network to build mathematical model of seed soaking and sprouting process, therequirement of precision of model error and the mean square error curve is satisfied; seed soaking stage adoptsPID control on the basis of mathematical model built, while sprouting stage uses fuzzy-PID control, and thenthe3-d temperature field surface simulation verifies the feasibility of the temperature distribution. Finally,effectiveness of the control strategy in rice budding rate, burning seed rate and uniformity is validated by test.1. Establishing the mathematical physics model of seed box numerical simulation by ANSYS CFX14.0.Numerical simulation study on volume of seed soaking and pregermination box for27m3(6m x3m x1.5m)of is carried by CFD numerical calculation, and research the influence on seed soaking and pregerminationtemperature in stack with different horizontal spacing, stack height and inflow discharge. The results show thatthe water flow speed is greater, and then the temperature field is better uniform, the highest temperature in thebox is basically constant. Porosity is smaller, and then the temperature field is better uniform. When theporosity is0.1, the highest temperature in the box is the lowest; the vertical spacing within a certain range issmaller, the highest temperature is lower, the uniformity is better.2. With temperature uniformity as test index, through single factor experiment, investigating andanalyzing the influence on the temperature uniformity with the different level spacing, height and the waterflow. Through quadratic regression orthogonal rotary tests with three factors five levels, the mathematicalmodel is established, using the binary function surface analyses the main factors affect the indexes, and theprocess parameters with constrained nonlinear optimization theory are optimized, and a set of optimalparameters is determined.3. With heating valve opening, the environment temperature, the water temperature and pipe watertemperature as the input of seed soaking process modeling, and48temperature points in temperature field of as the output, respectively, using BP and RBF neural network to model and compare, fitting curve shows thatthe precision of RBF neural network is higher.4. With heating valve opening, the environment temperature, the spray ball valve opening, spray watertemperature and water temperature in pipeline as the input in the pregermination process, and48temperaturepoints in temperature field of as the output, adopts genetic algorithm and particle swarm optimization (PSO)algorithm respectively optimize the parameters of RBF network on the basis of RBF neural network, thesimulation verify the RBF neural network model based on particle swarm optimization is better.5. Seed sprouting system adopts the most commonly used PID controller as the basic control strategy oftemperature control in the process of production; for sprouting process with more nonlinear factors fuzzycontrol is introduced, namely, the fuzzy-PID control. The3-d temperature field surface simulation of the wholeprocess verifies its feasibility.