Optimization Study Of Air Source Heat Pump Temperature Control System Based On Microcontroller

Drying agricultural products has become an increasingly important and widely used process in the agricultural product processing industry.Traditional drying equipment typically uses fuels such as firewood,coal,and natural gas to generate heat,which can lead to high energy consumption.As a result,the use of clean energy sources such as air energy and solar energy has become more popular in the drying process.This approach can help to reduce costs,minimize environmental pollution,and enhance the efficiency and quality of dried products.In the drying of high-value crops,temperature control is crucial.This often involves maintaining a constant temperature range throughout each drying stage,with different target temperatures set for each stage.Therefore,the drying equipment needs to have high temperature controllability to ensure that active ingredients are preserved and to facilitate a stable and efficient drying process.To meet these requirements in practice,this paper focuses on investigating the mechanism and practice of the temperature control system of heat pump drying equipment.The main research objectives of this paper are as follows.(1)This paper focuses on the structural research of heat pump drying devices.Firstly,the structure of the conventional heat pump drying device is analyzed and a suitable structure scheme is proposed.The advantages and disadvantages of the open,semi-open and closed structures of the heat pump drying system are comprehensively analyzed,and the closed structure is selected for its superiority.Subsequently,modifications are proposed to the general closed heat pump drying device based on the actual conditions.These modifications include the direct adoption of the closed cycle at the condenser end,the additional design of a moisture discharge bypass,and the incorporation of a solar auxiliary heating device in the heat generating circuit of the device.(2)The temperature control strategy of the heat pump drying system was studied.Firstly,the parameters to be controlled during the drying process were analyzed,with temperature being identified as the key parameter.Next,the two most commonly used control strategies,PID control and fuzzy control,were evaluated and fuzzy control was chosen as the basic control strategy due to its control characteristics.The design of the fuzzy controller was then conducted based on the actual temperature control characteristics of the heat pump drying device.The design was optimized according to the actual changes in the drying oven temperature during the drying process,resulting in a targeted and optimized basic heat pump drying controller.Additionally,a parallel fuzzy controller design scheme and specific parameters were provided to mainly optimize the fast temperature rise process.(3)This section outlines the implementation scheme of the designed temperature controller.It involves the selection of hardware components and the electrical connections for the controlled part of the temperature control system in the heat pump drying equipment.Additionally,the wiring of the temperature control modification part of the control board,the communication wiring with the upper touch screen,and the configuration design related to the touch screen are described.(4)The temperature control part of the controller of the modified heat pump drying device was modeled and simulated.Firstly,the transfer function between the drying oven temperature and compressor frequency was determined using experimental measurement methods for the heat pump drying platform used in this study.Then,the fuzzy controller before optimization and the optimized fuzzy controller were modeled in MATLAB software simulink,and the rapid temperature rise process was simulated and compared between the two controllers.Finally,a comparison between the two controllers in terms of overshoot and stabilization time was made.(5)Experimental comparisons between the general heat pump controller and the optimized controller were conducted on actual equipment,and the results demonstrate that the optimized controller outperforms the general heat pump controller in terms of overshoot and the speed of reaching steady state during the fast temperature rise process of drying in the actual heat pump drying device.Thus,it meets the expected requirements of the previous heat pump drying device modification.