Abstract
The research is conducted due to the need to modernize automated control systems of continuous industrial processes, improve their accuracy and quality. The approach to the design of precise control system is developed. The approach is based on a set of models. Based on the known analytical relationships, the mathematical model of the dynamics of a nonlinear control object is developed. Its feature is a full accounting of the kinetics and thermodynamics of the first-order chemical reaction. The model for direct determination of the hydraulic friction coefficient, based on the approximation of the Colebrook-White nomogram is developed. The model of the valve hydrodynamics, depending on the opening rate and flow velocity is developed. The models of automation hardware, considering characteristics, errors and dynamics are developed. The optimal multivariable controller on the basis of the theory of analytical design of controllers is designed. The proportional - integral action of the controller is formed by the extension of the object model. A full measurement of the object states made it possible to abandon the use of a state observer. The precise automated control system of the vitamin B 6 synthesis reactor is developed. The transients resulting from the automated control system modeling demonstrate deviations of the controlled plant parameters from the nominal value: concentration – no more than 5 %, temperature – no more than 2.5 %, and level – within 2 % under significant disturbances in feedstock consumption rates at the reactor input (20–30 %). Due to small deviations of transients under the action of disturbances, the proposed precise automated control system ensures the high quality of the product and the process safety in the reactor. The developed approach is recommended for use in the design of precise control systems, and the designed precise automated control system of the vitamin B 6 production reactor – in the pharmaceutical industry.
Highlights
The design quality criterion is formed as a result of accurate modeling of the developed control system, which involved all the models obtained by accomplishing the objectives 1–5
The concentration meter model has the following characteristics: – the reduced measurement error is 2.5 %; – the dynamics are represented by a lag element with a time constant of 0.5 s; – the input signal is added to an evenly distributed stationary noise, the amplitude of which is equal to the absolute error
The temperature transducer model has the following characteristics: – the absolute error (0.15+0.002∙t) °C; – the dynamics are represented by a lag element with a time constant of 7.8 s; – the input signal is added to an evenly distributed non-stationary noise, the amplitude of which is equal to the absolute error
Summary
A prerequisite for the research is the potential for the design of high-precision automated control systems (ACS) of almost any complexity using advanced digital equipment. The urgency of the design of a precise ACS of a vitamin B6 synthesis reactor is caused by the fact that vitamin B6 is a valuable substance for the pharmaceutical, food and agricultural industries. The literature review [1] shows that, despite a possibility of designing ACS of any complexity and quality, simple systems based on PID controllers prevail (up to 90 %) in the world industrial automation. For the design of high-precision ACS, modeling of the reactor is performed in the class of nonlinear lumped-parameter systems. Such modeling has been considered, for example, in the fundamental paper [6]. Development of an approach to the synthesis and modeling of precise ACS, in particular, of the vitamin B6 synthesis reactor, is a challenge
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