Procedure for identifying a delayed process with compensation and setting up a mechanism to regulate such a process

摘要

Commencing from a first steady state, the control variable (y) of the first controller (33) is set to a first constant value (80%) and that of the second (34) is cut off. Following determination of a turning point in the curve of control variable (x), a first IT1 model of the control processing system (32) is identified. The process is controlled as a function of the first IT1 model, at least close to a second steady state (170 degrees C) differing from the first. From the tangent (wh) at the first turning point, the value of the variable (y) and the control variable (x) from the first and second steady states, a VZ2 model is identified. Commencing from a first steady state, the control variable (y) of the first controller (33) is set to a first constant value (80%) and that of the second (34) is cut off. Following determination of a turning point in the curve of control variable (x), a first IT1 model of the control processing system (32) is identified. The process is controlled as a function of the first IT1 model, at least close to a second steady state (170 degrees C) differing from the first. From the tangent (wh) at the first turning point, the value of the variable (y) and the control variable (x) from the first and second steady states, a VZ2 model is identified. The VZ2 model describes the kinetics of the process (32) and the amplification coefficient for the first controller (33). From the second steady state on, the first controller (33) is switched off and the control variable of the second (34) is set to a second constant value (20%). Once a second turning point in the curve of the control magnitude (x) has been determined, an amplification coefficient for the second actuator (34) is determined, in accordance with the formula: kik = (dxwk/dt + Kih . yinfinity)/(YLLMTUM). In this equation : dxwk/dt is the gradient of the tangent at the second turning point and (kik) is the process amplification coefficient of the identified first IT1 model. yinfinity is the value of the magnitude (y) in the second steady state. YLLMTUM is the second constant value of the control variable. An Independent claim is included for equipment based on the method, used e.g. to control a plastic extruder. There are controllers heating, and others cooling, operating at different intensities. Preferred features: Salient features include the 170 degrees C typical working point of a steady state, following heating. The control process is further elaborated mathematically, including formulae in the form of approximations, polynomial series expansions, up to fifth order with respect to the process path time constants ratio. Quantified empirical constants are also provided.