343 In developing the automated 1300 blooming mills (the fastest such mills in the world), G.L. Khimich of OAO Uralmash proposed an original system for ingot transfer from the heating pits to the intake conveyer of the reduction mill: ingot transfer by self-propelled trolleys (ingot cars) along a closed circular track (circular transportation). Currently, this system is used at practically all 1150‐1300 blooming mills, with various track configurations and positions in the heating-pit department; it ensures rhythmic ingot supply at practically any mill speed. Because the rate of ingot supply is independent of the position of the discharge system and the front of the heating pits, rational organization of their operation is possible, with improvement in the operating conditions of the heating-pit cranes [3]. Thanks to stability of ingot supply and the use of simple and relatively reliable ingot cars, stable automatic ingot supply has been ensured at all the blooming mills designed and reconstructed by OAO Uralmash for more than four decades. Moreover, the circular supply system may also be used for cyclic transportation in assembly and adjustment operations, especially with a high density of equipment in the shop; such designs have been developed at OAO Uralmash. Of course, the introduction of continuous casting for a wide range of steel sheet, bar, and sections rules out the construction of new blooming mills in the near future, but we may expect that existing equipment will remain in operations for decades to come, in view of the slow growth of the Russian economy, its unchanging raw-materials orientation, and the very low rates of technological replacement. Therefore, given that reconstruction of reduction and other billet mills is feasible, with improvement in their reliability and longevity, the present work is devoted to computer research aimed at improving design methods for closed circular systems of billet and rolled-strip transportation (in particular, circular ingot supply) and refining their optimal parameters [1]. On the basis of optimal control theory and the Pontryagin maximum principle, a computer method is developed for simultaneous determination of the optimal gear ratio j of the gear system and the rated torque M rat of the electric motor driving the wheel pairs of the ingot car, with subsequent selection (for specified rate of ingot supply and specified frequency and duration of stopping) of the necessary number K of ingot cars, taking account of the permissible motor heating, as well as the maximum speed of the ingot car on linear ( v max ) and curved ( v R ) sections of the track. The optimal gear ratio may be selected on the basis of various criteria: maximum speed, which reduces the number of ingot cars; minimum load, which increases the working life of the equipment; and minimum heating, with specified time of car motion on the working or idling branches of the circular track, determined by the rolling cycle. The flywheel masses of the gear system and the motor, which are nonlinear functions of the gear ratio and the rated torque, respectively, are introduced in the method in the form of regression equations approximating the actual parameters of the OAO Uralmash two-stage gear system and the parameters of the D12‐D818 dc motors. The search for optimal parameters j and M rat is based on the random-perturbation method.
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