Research On Nutrient Solution Measurement And Control System Of Plant Growth

In control environment plant production system, the parameters of nutrient solution were characterized by the nonlinearity, multivariate, time-delay, and serious nondeterminacy. It was difficult for the conventional control method to get satisfied effect because of the complicacy in building mathematic model, what results in the straggling actuality of control automatization in this field. Fuzzy control could satisfy the requirements of the complicated, nonlinear system specially, and has gotten satisfied effect in this area. Contraposing the problem of nutrient solution control, an intelligent control method based on the fuzzy-neural network control theory for nutrient solution control was proposed in this paper on the basis of in-depth analysis of forthgoers' returns. A master-slave model control system was developed for nutrient solution controlling.For the sake of achieving intelligent control of nutrient solution, this paper focused on the application research of fuzzy-neural network control algorithm in nutrient solution control system. A fuzzy-neural network controller based on ANFIS (Adaptive Neural Fuzzy Inference System) was designed. This controller could get satisfied control effect on the concentration of dissolved oxygen, components of nutrient solution, electronic conductance, pH, and so on. The system could keep these parameters at setting values that can satisfy the plant growth requirements. The simulation research of control system was carried out in MATLAB. The simulation experiment results verified the validity and feasibility of fuzzy-neural network controller designed in nutrient solution control system.The hardware platform of nutrient solution control system consists of slave computer and master computer. A data acquisition and processing system which was composed with sensors, signal amplifying circuit, sample and hold and analog/digital conversion circuit, MCS-51 MCU and serial communications interface circuit was developed to fulfill data acquisition, A/D and filtering process and the information transmission between slave computer and master computer, etc. An output controlsystem which includes solid state relay, drive circuit, electromagnetically operated valve, etc, was designed. It could receive control signals sent from master computer that generates by fuzzy-neural network control algorithm, and operate actuator by pulsewidth modulation control mode, in order to control parameters of nutrient solution by intelligent control method. The host computer, display equipment, Iput/Output equipment and other devices make up of master computer system. It could implement the function of real time supervisory control and system parameters setting.For the sake of obtaining higher reliability, expansibility and antijamming capability, the structuring and modularized design approach was introduced during the designing process of software platform of nutrient solution control system. The software of slave computer was developed by using assembly language and C51 language. Subprograms of data acquisition and process, digital temperature measure, serial communication and outgoing control, was programmed. It is good for exerting the capability of software and hardware sufficiently to programme using the two languages. At same time, the universality and maintainability of the system was enhanced. The software of supervisory control system was developed by Visual Basic. The function of real time display, storage, query of data information received, and monitoring of the parameter change of nutrient solution can be obtained by this software. The software system of master computer consists of many modules, including: fuzzy-neural network control module, serial communication module, real time monitoring module, data base module? help module and so on. These modules are independent mutually as well as interrelated with each other, and realize the intelligent supervisory control of nutrient solution system under the control of main routine.The ion selective electrode is one of important signal acquisition component of nutrient solution regulate and control system. Its performance has a notable influence on the run of the control system. Veracious acquaintance of the ion selective electrode selected has been obtained by testing experiments of response time and stability. In the working process of slave computer application system, the single-chip microcomputer will be affected by both the internal interference and externalinterference, which results in system exception occurred. In order to guaranteeing the running of the slave computer application system running efficaciously, steadily and reliably, both software and hardware antijamming measures including photoelectricity separation, deploying decoupling capacitor, intercalating self check program and software trap, and digital filtering were adopted.