№70-13

Modified algorithm of automatic temperature control in an electric resistance furnace for metal heat treatment

A. Bublikov¹, M. Isakova¹, V. Nadtochyi¹, D. Zybalov¹, Yu. Halchenko¹, M. Khoroshailov¹

¹ Dnipro University of Technology,Dnipro, Ukraine

Coll.res.pap.nat.min.univ. 2022, 70:134-145

https://doi.org/10.33271/crpnmu/70.134

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ABSTRACT

The purpose. The purposeis to improve the quality of heat treatment of metal in electric resistance furnaces byimproving automatic temperature control in the furnace. The main quality criteria of the automatic control system is the minimization of the metal heating time without exceeding the permissible over-regulation of the transient process at the output of the control system.

Research methodology. Provided that the research tasks are solved, the method of computational experiments using specialized computer programs for modeling transient processes in automatic control systems is taken as a basis. When calculating the temperature regulator in the furnace, methods of modern automatic control theory were used. The requirements for the controlprocess and the specificsof the operation of the controlobject are taken into account. Theoretical research methods (systemsanalysis and synthesis) were used to study the automatic control system. The research was conducted on the basis of computational experiments using analytical and computerized methods of synthesis of automatic control systems. Evaluation of the effectiveness of the automatic control process was carried out using the methods of mathematical statistics.

Research results. A simulated model of the automatic temperature control system in an electric resistance furnace for heat treatment of metal was created. The method of synthesis of the automatic control system was justified taking into account the requirements for the control process and the features of the control object, and based on it, the calculation of the temperature regulator in the furnace was carried out. Studies of the dependence of the parameters of the transient process at the output of the control system on the parameters of the regulator have been carried out, based on which the regulator settings are determined, which provide rational values of the quality criteria of the control system.

Scientific novelty. For the first time, it was established that an automatic control system with a computerized method configured for maximum speed by a PID regulator and a shaper of a linearly changing temperature set point in the furnace successfully works out the given parameters of the transient process at its output, but only on the condition that the time for heating the metal significantly(more than 1.5 times) exceeds the time of the transient process of the furnace as a control object. Otherwise, an unacceptable temperature overshoot occurs in the furnace. It was determined that the dependencebetween the maximum level of the control signal at the first switching interval of the speed-optimal regulator and the duration of the transientprocess at the system output is inverse and exponential in nature. At the same time, this dependence is approximated with high accuracy (the maximum relative error does not exceed 2.5%) by a power of eighth order polynomial. It was found that the accuracy of the proposed modified regulator, optimal in terms of speed, is a variable value in different sections of the graph of the control signal level dependence on the duration of the transientprocess.

Practical value. The method of synthesis of the automatic temperature control system in the resistance electric furnace for heat treatment of metal is proposed. At the same time, the parameters of the optimal control algorithm are substantiated according to the criterion of minimizing the metal heating time without exceeding the permissible over-regulation of the transient process at the output of the control system.

Keywords: control system synthesis, temperature, resistance electric furnace for metal heat treatment.

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