DEVELOPMENT OF A DISTRIBUTED CONTROL SYSTEM OF THERMAL PROCESSES IN A HYDRAULIC PRESS

Abstract

The necessity of regulating the temperature of the coolant in hydraulic presses, providing hot gluing of plywood, regulating the pressure in the press channels and maintaining technological parameters at a given level, is considered. A column hydraulic press P-714-B for hot gluing of plywood, installed at the Ust-Izhora plywood mill, is considered as a control object. The article provides a description of the column hydraulic press. To monitor the parameters of the presented installation of plywood production, it is proposed to consider the heating press plates and plywood packages as an object with distributed parameters. To develop a mathematical model of the control object, a functional diagram of this device with the main equipment and technological flows of the coolant was considered. A technique has been developed for modeling objects of this class as objects with distributed parameters. Consideration of the processes occurring in the channels of the heating plates made it possible to formulate differential equations of motion that describe the flow of the working medium in the system of channels. The developed method of mathematical modeling of heat propagation in the heating plates of the press and plywood packages made it possible to draw up a mathematical model for the object under consideration. This mathematical model turned out to be quite complex, and it is not possible to solve the resulting system of partial differential equations analytically (to isolate the transfer function). For a numerical analysis of the considered control object, a discrete model of equations and a computational algorithm were compiled. In the process of compiling discrete models, the problems of “joining” the boundary conditions were solved, the stability of the computational scheme was ensured, and the steps of discretization with respect to spatial variables were selected. Software was specially developed for computer modeling. With its help, the temperature values at the control points were calculated. The presented mathematical model made it possible to carry out a numerical experiment, as a result of which the frequency characteristics of the object under study were obtained. These characteristics were used in the synthesis of a distributed high-precision controller.