Study On Particieboard Hot-Pressing Heat Transfer And Thermal System Control Method

Particleboard has become one of the most important wood products because of its established production and low-cost processing technology. Its production and application are significant in making better use of forest resources, alleviating the shortage of domestic raw materials for woodworking, and facilitating the sustainable development of the ecological environment. An increasing emphasis is being placed on research related to its production technology because of the rapid development of processes that utilize wood and wood composite materials. Hot repressing, the most important stage of the entire technical process, largely determines the physical performance and market recognition of particleboards. Hot repressing is also the determining process in improving the production technology of particleboard in our country. This present investigation combined with a study by the Heilongjiang Science Fund Program for Youth entitled "Research on visual simulation of particleboard multi-layer hot-pressing heat and mass transfer process" aimed to comprehensively analyze the key problems involving heat and mass transfer processes in the particleboard hot-pressing system and the position servo system tracking control. Innovative achievements have been attained.Based on the conservation equation of classical mechanics theory, we established a heat transfer mathematical model for the particleboard hot-pressing process by using the separation of variables method under the precondition that polycondensation heat is released because of adhesive curing during this process. We aimed to analyze the changes in mat core layer temperature with increasing time. Such changes were affected by contact heat transfer of hot platen and by the transfer of polycondensation heat released from adhesive curing. We aimed to compare the current model with the traditional model. Different particleboard hot-pressing experiments have been conducted using different hot-pressing technical parameters. Data derived from these experiments have been compared with the heat transfer model, which sets a solid foundation for parameter control of the particleboard hot-pressing process.By considering the vertical radiation effect on the particleboard mat by the thermal field during the particleboard hot-pressing process, a coupled heat transfer mathematical model for both contact heat transfer and thermal field radiative heat transfer was established. We conducted a simulation analysis of the model. Complicated characteristics for the particleboard hot platen thermal field were established. We aimed to offer a feasible and effective idea for building a heat transfer model for the heat radiation formed by the thermal field by introducing the inverse design method. We elaborated on the mechanical composition of the hot-pressing system, as well as the composition and working principle of the control system. We also presented a proposal for a back-stepping tracking control method for the hot-pressing position servo system. The asymptotic convergence of tracking error to zero was guaranteed by adopting Lyapunov’s stability theory. The findings of the current study indicated that by using the back-stepping method, the controller design enables tracking of the position swiftly and accurately by the system. The features of the controller included high convergence speed, high tracking accuracy, and minimal tracking error.For the particleboard hot-pressing position servo system with uncertain model and external disturbances, we proposed a neural network-based, self-adaptive back-stepping sliding-mode control scheme and used the RBF network uncertainty model for approximation. This scheme was combined with sliding-mode control to inhibit external disturbances effectively. Moreover, this scheme offered evidence for asymptotic stability of the system and for the asymptotic convergence of tracking error. Finally, the system’s robustness against parameter uncertainty and external disturbances was enhanced. A certain reference value was reached in the study of particleboard hot-pressing control.