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Work of the Master is devoted to control system research of flying shears for application in metallurgical manufacture.
The urgency of this work consists in research of modernization possibilities of technological processes in existing industrial lines of an iron and steel industry, particularly introduction of continuous cut systems for flying shears that will allow raising a performance.
The scientific importance of work consists in research of control methods for system of the electric drive for knifes of flying shears as drive with speed and position control, and introduction of setpoint generators for systems of regulation, that will allow to realize a efficient control of technological process. Researches include theory of automatic control, control systems of the electric drive and mathematical modeling of electromechanical systems.
Practical use of work consists in possibility of application of the received results for introduction on technological lines of metallurgical and other branches of industry for the purpose of productions efficiency.
All kinds of flying shears are a part of equipment applied in modular lines, intended for processing and furnish of a sheet material in rolling manufacture of factories black and nonferrous metallurgy or at the enterprises processing a rolled strip in sheet production. Various kinds of flying shears are intended for concrete sort of the operations connected with division of a material of a moving strip on a part on the move. The principle of work of flying scissors is shown on fig. 1. Prior to the beginning of cut knifes stay is in some initial position. The strip of hire approaches to knifes and at signal reception knifes begin to speed up, up to a speed higher than a speed of a strip on 5-10 %. Thus knifes move along a trajectory which is defined by mechanism kinematics - type of shears. Knifes converge up to contact and cut, and then knifes disperse and revert to the original state.
Figure 1 – Operation of flying shears
Researches of flying shears as a problem of the electric drive allow raising efficiency and quality, for lower energy usage of installations or expenses for repair, adjustment and change-over for new type of production. Usually, researches refer to a design and parameters of concrete installation of any metallurgical corporation on purpose to raise efficiency of installation or to modernize production. Researches study this problem both from the point of view of a mechanical part and materials technology, and from the point of view of systems construction of the electric drive (main drives) or installation introduction to global automation system.
As a basis for this work methods of the classical theory of control and particularly construction of control systems of position, which also were repeatedly studied on chair of electro technical faculty, are used.
Review of researches on a theme in Ukraine and in the world
Universities which have a chair of automatics or electric drive as a rule prosecute subjects of automation of metallurgical manufacture of the nearby regions. The subjects of works are directed on modernization of control systems and examined, as a rule for application on a concrete technological line of any factory.
In the given Master’s thesis work of a control system of a drive in a mode "start-stop" and in a mode of continuous rotation is investigated. For work in these modes presence of system of automatic control of position for the electric motor is necessary. Differences between modes consist in formation of an setpoint signal and operating of the executive mechanism in pauses between cuts. In a mode "start-stop" knifes stay in some initial condition. After beginning of cutting a current control loop and a speed control loop are active, knifes speed up till forward speed higher than speed of hire on 5-10%. Knifes come nearer to a strip, there is a cutting after which activates the external position control loop, which moves knifes in an initial condition. The example of such system of automatic control is resulted on fig. 2.
Figure 2 – Structure of a control system in “start-stop” mode
In terms of features of position control, the type of a regulator of position does not influence quality of cutting of strip by sufficient synchronization between knifes (it is possible only mechanical), however processes of reregulation and slow positioning can lead to raised usage of energy. Lacks of the given method are necessity of mechanical synchronization of the top both bottom knife, and constant processes of speed up and braking, even in the presence of possibility of return of energy in a network during braking it will lead to overestimated energy losses.
Alternative to the examined mode is the mode of continuous rotation, the system of automatic control for which is resulted on fig. 3. In this case the position control loop is not disconnected, and constantly is active and receives constantly changing task from generator of setpoint intensity. Thus, all logic of control is reduced to formation of a specific signal of the setpoint. The drive operates in a mode of position control and synchronization of knifes by means of the theory of automatic control is possible. Knifes constantly move with a speed exceeding speed of strip on 5-10 %. By the beginning of cut the setpoint is formed so, that knifes will be synchronized with a strip. At frequent repetition of cut such mode is more preferable in comparison with the first.
Figure 3 – Structure of a control system in continuous rotation mode
Carried out master’s thesis is continuation of some results of studies, directed on the productions of the metallurgical factories directed on modernization, particularly on modernization of work of the main drive of flying scissors. The received results will allow to pass from an operating mode "start-stop" to a mode of continuous rotation which in case of frequent cuts is more effective, because of lower power expenses and lower expenses for repair and service of the equipment.