| Driven by the increasing demand of pork and pork products, large-scale and intensive pig production systems have been under rapid development in the world. In large-scale pig farming, whether un-confined or confined, animalliving environment plays a crucial role for pigs. A suitable growth environment is favorable for the health, growth, and reproduction of pigs. Therefore, pig living environment control has attracted wide attention. Pig living environment refers to all external non-genetic factors affecting the pigs, including building design and pigliving space; indoor air temperature and humidity; concentrations of harmful gases, dusts and bacteria; lighting and ventilation, etc. Due to the non-linear, time-varying, and multi-variable characteristicsamong different environmental factors within abuilding, assessment and control of pig housing environmental face many challenges, especially for intelligent and precise control of these environmental factors. Therefore, assessment and control of pig housing environment has great research value for solving the conflict between economic benefits and energy consumption in pig production.Based on a review of domestic and foreign environmental assessment and control methods related to pig housing and using fuzzy theory, this thesis studied methods for evaluating multiple environmental factors, modeling indoor microclimate, and controllingpig building environment. A fuzzy comprehensive model for multiple environmental factors, which include ambient temperature, humidity, and ammonia(NH3) concentration, was developedfor pig building evaluation and control. The model consists of several submodels that are the building environment heat exchange submodel, moisture content submodel, ventilation submodel, NH3 concentration prediction submodel, and temperature and ventilation control submodel. This thesiscontributed the following to the research on pig building environmental modeling and control based on measurement data from the Swine Environmental Research Building, Animal Research and Education Center, Purdue University, USA:(1) Determinedthe major environmental monitoring variables based on the characteristics of the pig building. Fiveessential variables for environmental assessment and control were identified and selected usingthe monitoring data and the standardsfor pig building environmental control.(2) Developed a fuzzy comprehensive evaluation model for swine building multiple environmental factors using the monitoring data, fuzzy set theory, environmental control standards, and membership functions of temperature, humidity, and NH3 and carbon dioxide(CO2) concentrations inside the building. A weight vector of fuzzy evaluation was given based on the analytic hierarchy process. A fuzzy transformation was applied to the membership relationships between various environmental factors. The principle of maximum membership degree was used to decide the comprehensive evaluation of the swine building environmental suitability.(3) Established climate models that included an ambient thermal exchange model, a moisture content model, and a ventilation model based on energy balance and mass balance. Additionally, a mechanistic model and a statistical model of NH3 release were presented, and a prediction model for NH3 concentration inside the building was provide based on fuzzy adaptive neural network(ANFIS) in different seasons. The relationship between various environmental factors were analyzed to determine input factors for ANFIS model in different seasons.(4) Simulated and verifiedthe swine building climate. The ambient thermal exchange model, moisture content model, and ventilation model were programed in Simulink.Temperatures, humidity, NH3 concentrations and ventilation rates inside the buildingwere simulated. The simulation results were verified by using the actual environmental monitoring data from pig building as inputs.(5) Proposed the structure of a swine building environment control system, which includs a temperature control subsystem and a ventilation control subsystem, based on the fuzzy control theory and building environmental characteristics. Temperature control was treated as the most important factor, followed by the ventilation control, to reduce harmful gas concentration and humidity.(6) Established fuzzy control rules in different seasonsbased on seasonal temperature variations and ventilation control standards. A fuzzy temperature controller and a fuzzy ventilation controller were developed according to the environmental control standards and the results of environmental suitability evaluation. Inputs and outputs of fuzzy control system were determined and fuzzification and defuzzification were processed.(7) Determined a compensation coefficient D between the fuzzy temperature control and fuzzy ventilation control. The relationship between heating and temperature under the heating mode, and the effects of ventilation on temperature change were used to determine the compensation coefficient D tobalance between ventilation control and temperature control in cold winter.Compared with the single-factor evaluation model, the establihed model for the environmental suitability assement of pig building based on the FSE method can make a comprehensive assessment. The simulation and verification of microclimate environment model for the pig building was showed that the difference of indoor air temperature and measured one was less than 1oC, the minimum error of ammonia concentration is 0.0858. So, the environment model can accurately simulate pig building microclimate and used as a basic model for the environmental control. The control model of temperature and ventilation with the compensation coefficient D, compared with the meaured data, the maximum temperature deviation was 0.61 oC, the temperaute was controled stablely inside the building, and it was very close to the setting temperature. The maximum relative humidity deviation was 11.4% that does not exceed the normal range(± 25%), and it can meet the pig building relative humidity control requirements. The changment of ammonia concentration was between 0.9ppm and 1.6ppm, which was far less than the setting value 12 ppm, and it also satisfied with the ammonia concentration control requirements.Therefore, the pig building environmental suitability evaluation method, the barn environment microclimate model and control model that established in this study based on the fuzzy theory can provide a viable reference for the pig building environmental control. |
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