Study On Measurement And Control Technology For Bamboo Plywood Production Process

The industrial utlization and yield of bamboo in China stands on theleading level internationally, however, fundermental research onmeasurement and control technology for production process is still veryweak. The common characteristics of simple detection method, lowautomation level, serious environment pollution lead to poor productquality. Hot pressing technology adopted in bamboo plywood productionprocess plays a key role on improving bamboo plywood quality, shorteningthe processing period and reducing energy comsuption The establishmentof hot pressing process has a close relation with the thermodynamicsparameters of bamboo, so the measurement of the parameters and theresearch on their distribution rule is of great significance for amendingbamboo plywood forming process and improving the product quality:This dissertation presents some achievements of our systematicresearch on measurement and control technology for the typical links ofbamboo plywood production process. The main achievements go asfollows:1. Measurement and analysis of distribution rules of thethermodynamics parameters of bamboo.This is a pioneer research internationally. By using Flash Method andCompare Method respectively, the thermodynamics parameters of bamboo,i.e. thermal diffusivity a andthe specific heat C_p, were measured. Heatconductivityλwas then calculated. Research results illustrate that thethermodynamics parameters of bamboo have little to do with its position,height, growth direction and growth height; In the temperature range of7℃～140℃, the temperature distributions of thermal diffusivityα, thespecific heat C_p and conductivityλfollow normal distribution and reach their maximum values at about 70℃. The maximum to minimum ratio ofαis about 1.4 times, and the ratio ofλis about 2. This gives importantinstruction for heat treating process of bamboo2. Study on the influence of hot pressing processs on the surfaceroughness and smoothness of bamboo plywood.Although bamoo plywood's surface roughness and smoothness isimportant parameters for establishing quality standard, there are fewresearch results about the measurement technique and influencingmechanism of them. We conducted a domestic pioneer research on theinfluence of different hot pressing process on the surface roughness ofbamboo product. Combined with the main thermodynamics parameterss'distribution rule of bamboo obtained before, we gave explanation for theinfluencing principle. Compared with "hotin-hot-out" process,"cold-in-cold-out" process reach thermal balance faster due to uniformheating, thus has better surface quality.3. A novel "warm-in-warm-out" hot pressing process.Based on the temperature distribution of bamboo's thermodynamicsparameters, a novel "warm-in-warm-out" hot pressing process waspres-ented in this dissertation. The novel process intergrates the"hot-in-hot-out" process's advantages of short processing period arid lowresource cost, with the "cold-in-cold-out" process's advantages of producthigh smothness and low surface roughness, thus greatly improve theproduct quality.4. Modeling of adhesive production process.No plywood without adhesive, adhesive is the key raw material forproducing bamboo plywood. Adhesive production process is critical in thewhole production process of bamboo plywood. How to improve theadhesive quality has been a hot point in bambooacademia and industry.This dissertation presents the mathematical model of adhesive production process. With the characteristics of large time delay, thermalinertia, nonlinearity and selfheating, the process model is very difficult tobuilt based on mechanism. In this dissertation, the model structure wasdecided by taking the two-order inertial links with pure delays as the modelclass. Then, based on the original data from manual control practice of thepractical adhesive production process, the systemparameters of the modelclass were identified. For simplicity, the parameters of the controller canalso be chosen according to the model of oneorder inertial link with puredelays. Attenuation result shows that, except the acute selfheating periodof 60℃-70℃, the tracking accuracy to follow the process temperaturecurve reaches 2-3℃, which generally satisfy the requirement of theproduction process.5. Study on temperature control strategy and development oftemperature control system for adhesive production process.In China, adhesive production process is now on a manual controllevel. This leads to the instability of adhesive quality, which directlyinflences the quality of bamboo plywood. Especially, the imprecise controlof process temperature causes exceeding poisonous content which isharmful to human health and environment.We developed a temperature control system based on fuzzy adaptivePID control strategy, solved the problem that mathematical model isdifficult to build during the selfheating period. Fuzzy adaptive PID controlintegrates the advantages of traditional PID controll in simple algorithmstructure, easy on-line implementation, good steady state performance, withthe advantages of fuzzy control in robustness, dynamic state respnse. Testresults shows that the temperature control precision reaches±2℃duringthe whole reaction process, thus proves the effectivity of the algorithm inself heating period.