Study For Environment Optimal Control System In Greenhouse Via Vegetable Growth Parameter

With equipment agriculture's transiting towards "Factory Agriculture"gradually, greenhouse industry which as a underpinning industry of "FactoryAgriculture"has developed into a new industry which related to multiplicatemodern technology, and has taken a more important role in process of actualizingmodernization of agriculture in our country. Greenhouse industry's criticaltechnique, such as environment control technique, make a crucial effect to speedof development of our greenhouse industry. Accordingly, it is necessary toimprove the level of environment control technique in greenhouse, and especiallyto attach importance to software design.This article divided environment control system in greenhouse into threeaspect which is system frame, model for control, and arithmetic of control bytheory of autocontrol, and introduced their respective development in detailoverseas and at home. Then this article linked to actual state of greenhouse in ourcountry, and make a study for economical environment optimal Control System inGreenhouse by means of selecting a reasonable system frame, model, arithmeticand essential executive machine.The system adopts a structure of concentrate control, and it has a merit ofbriefness of composing. As controlled object is a single greenhouse, not a group ofgreenhouse, layout would not be too complicated. At present, general PC hashigher performance and lower price, making a backup system in different mannermay make for disadvantage of centralized risk of concentrate control.Study for combining of greenhouse environment factor and crop growthmodeling is a new current research aspect of environment control in greenhouse,which has highly applied value. So we could select vegetable growth parameter asmodel of environment control system in greenhouse, and the parameter can reflectdirectly function relation of photosynthesis intensity and key environment factor,as photosynthesis intensity may effect yield of crop.For synthesis control of environment multi-factor in greenhouse, it isnecessary to optimize synthesis control to reach goal of energy saving andproduction increasing, i.e. optimal control. From level of environment controlsystem in greenhouse, it could be classed into optimization of limited value and ofoptimal value in limited scope; from goal of control, it could be classed intooptimization of yield of crop and of economic requirement. The system makesoptimization of optimal value in limited scope and optimization of yield of crop.In system, illumination intensity and temperature is single direction control whichnot use supplementary light and increasing of temperature, otherwise, thickness ofcarbon dioxide is double direction control which either increase or decreasethickness. Moreover account for characteristic of long time of postponement ingreenhouse, it is supposed to define a reasonable control step, and a group ofcontrol command that based on the step would be outputted. In this case, validityof control action could be ensured, and consume of energy which caused byfrequent action of executive machine could be avoided. As a control algorithm, it regards a growth parameter as objective functionand variety of limited value of illumination intensity, temperature, and thickness ofcarbon dioxide as restrictive condition. By optimizing the objective function andcomparing theoretic optimal value of environment factor and mean value get in acontrol step, system could give a real-time reasonable control command. Duringvariety of environment in greenhouse, different environment factor could act as adifferent role in a different period. According to economical rule and energysaving, priority of environment factor for control could be determined by whichsystem could make control of illumination intensity, temperature, and thickness ofcarbon dioxide in turn. At home, general control of environment in greenhouse iseither a control of environment factor in a scope or a feedback control viaobjective value by experience, or a control via nerve net and fuzzy theory. It is nota good many to make real-time control via variety of environment factor ingreenhouse,such that optimal algorithm in the article is a worthy trial in realm ofenvironment control in greenhouse. Hardware of System is consisted of sensor, data acquirement card, general PC,relay, and essential executive machine, and they are general, so they are of obviouspracticability. System of software is consisted of three module which are allprogrammed with MATLAB. With module of user interface (UI), we could see thestate of control step, lower limit and upper limit value of environment factor,present value of environment factor, and state of executive machine. Module ofdata acquirement fulfills data acquiring of variety of environment factor, andtransfer of control command. Module of data analysis management is kernel ofcontrol system, it give a group control command every a control step by optimizedcontrol algorithm to carry out dynamic optimal control of executive machine.MATLAB has powerful function of numerical value calculation, sufficient andspecial toolbox, and applied control system emulation, so it is in favor of goingdeep into research on control algorithm in the future. It is not a good many to takedirect control with data acquirement card in MATLAB. In general, dataacquirement is taken in other software, such as LABVIEW. So the system acts as acase of integrated application of MATLAB, as well as it provide a referenceproject of establishing an economical environment optimal control in greenhouse.