## 2 Control and Management Systems for Technical Systems  
The functioning of technical systems is largely determined by changes in the environment. Their stochastic nature requires the development and implementation of control and management systems to ensure their uninterrupted operation and avoid the occurrence of critical situations [16].  
Design, implementation and improvement of control and management systems at enterprises, as a rule, are carried out by technologists with the participation of involved specialists--electrical engineers, mechanics, programmers and economists. At the same time, the solution of several important tasks is achieved [17]:  
* reducing of production costs;
* ensuring the safety of life;
* improving labor productivity;
* improving the quality of finished products;
* ensuring production flexibility.  
A wide range of automatic and automated systems are used in various areas of production to control and manage technical systems [18].  
The controls in an automated system can be either closed-loop or open-loop [19]. A **closed-loop control system**, also known as a _feedback control system_, is one in which the output variable is compared with an input parameter, and any difference between the two is used to drive the output into an agreement with the input. As shown in Figure 1, a closed-loop control system consists of six basic elements: (1) input parameter, (2) process, (3) output variable, (4) feedback sensor, (5) controller, and (6) actuator.  
A typical example of such an advanced control system with a feedback loop are controllers for positioning the servo drive axis. These devices use encoders to constantly measure and control the rotation position of the servo motor rotor. Thanks to this kind of feedback, it is possible to calculate and control the rotor speed in real-time.  
The SINAMICS control unit from SIEMENS, which can control the positioning of several servo drives, is a typical example of the use of a feedback loop system in practice (Figure 2). The entire actuator control device consists of multiple modules. The SINAMICS control unit is connected to the LM module, which converts the AC supply voltage 380 V to the DC supply voltage 500 V. The converted supply voltage is further adjusted in the motor modules from where it is further fed directly to specific actuators.  
This actuator control unit communicates with the ET200-SP PLC system via a communication protocol called PROFINET by exchanging SW blocks called Telegram or via Technology Objects. This device is superior to the SINAMICS control unit and sends the required positions to which all the axes need to be positioned. In the figure below you can see PLC which sends the required positions to the SINAMICS Control unit and acts as a master device.  
In Figure 3 there is a given hardware configuration of the control unit SINAMICS CU320-2 for controlling 4 servo drives.  
Figure 1: A feedback control system.  
Figure 3: Example of control system with feedback loop—SINAMICS control unit for controlling multiple servo axes.  
Figure 2: Programmable logic controller Siemens ET 200 SP.  
In contrast to a closed-loop control system, an **open-loop control system** operates without the feedback loop, as in Figure 4. In this case, the controls operate without measuring the output variable, so no comparison is made between the actual value of the output and the desired input parameter. With an open-loop system, there is always the risk that the actuator will not have the intended effect on the process, and that is the disadvantage of an open-loop system. Its advantage is that it is generally simpler and less expensive than a closed-loop system.  
Within the framework of this research, closed-loop control systems and their constituent elements are of the greatest interest.