Study Of Climate Chamber Control Based On Fuzzy Sliding Mode Variable Structure

Climate chamber method can simulate actual indoor environment, evaluate formaldehyderelease of artificial board and its products. The testing results has a high credibility since theyreflects the actual situation of formaldehyde release indoor.Due to high cost of climate chamber equipment and a longer testing cycle, themeasurement of formaldehyde release cost a lot, which results in climate chamber method cannot be widely used in domestic. In addition, climate chamber temperature and relative humidityare nonlinear controll objects with the properties of strong coupling and large lag. Therefore, itis hard to to obtain good control using the conventional PID control. In order to solve abovetwo problems, this study is aiming at developing a30m3formaldehyde test climate chamberwith the core of microprocessor. Fuzzy sliding mode variable structure arithmetic is applied toclimate chamber control. Through theoretical derivation, simulation experiment and actualmotion, the control effectiveness of fuzzy sliding mode variable structure on control of climatechamber are assessed. The specific conclusions are given as follows:(1) A new climate chamber equipment has been developed to simulate a livingenvironment with a volume of30m3. It can be used to examine the formaldehyde release ofwood-based panels and wood products. ATmega2560microprocessor is applied as the core ofcontrol system. The main features of system programs are single function and clear structure,which lead to easily compile, maintain, modify, and easy to transplant the syste, accordinglyspeed up software development. In comparison to the cost of PLC system, the cost ofmicroprocessor control system is reduced by one third.(2) Mathematical models between temperature and relative humidity of climate chamberhas been established. The mathematical models are simplified based on local linearization andfeedforward decoupling. Meanwhile, the double input and double output system is decomposedinto two single input single output system, in order to slove this model easily. (3) Control effect of fuzzy control and sliding mode control on system model of climatechamber are studied respectively in this research. In order to combine the advantages of twodifferent control strategies, a fuzzy sliding mode controller has been designed. In this newcontroller, switch function S is used as fuzzy input variable and improved exponential reachinglaw coefficient k and ε as fuzzy output variable. In this way, the approach process is optimizedand chattering phenomenon is alleviated. Simulations results show that fuzzy sliding modecontroller has a good control on climate chamber nonlinear system. Compared to PID control,it has faster response speed and smaller overshoot, et.al advantages.(4) For the first time, fuzzy sliding mode control algorithm was applied to temperatureand relative humidity control of the formaldehyde test climate chamber. The test results showthat when outdoor environment temperature is9℃, it takes about7h to reach steady statebetween climate chamber temperature and relative humidity. It also shows that the accuracyfor temperature and relative humidity can achieve±0.3℃and±1%respectively, with a slightovershoot.(5) Fuzzy sliding mode variable structure control makes constraint technology ofgenerating saturated moist air in dynamic environment come true. There is no fog and dewgenerated through whole detecting process, which ensures the accuracy of the inspectionprocess.