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Robust control

 

Closed-loop control is a core area of system automation. It's based on a negative feedback loop architecture. Current development of the theory of closed-loop control dictates new guidelines, wich are based on sophisticated mathematical aproaches of analisys and design. Very impotrant area of the development of closed-loop control is modern robust theory, wich covers several aspects of the control problems such as robustness to external disturbances, flexibility, reliability, non-linearity. The goal of robust control is to ensure the stable operation of the system and to ensure the desired performance despite uncertainties of the controlled object and the impact of external interferences and input or output noise.

The development of robust control theory was strongly influenced by tecnological progress especially in the field of aviation, space technology and automotive technology where the reliability and robustness are of major importance.

Due to the pragmatic of the theory and in-depth analysis and synthesys, the use of closed-loop systems is wide in allmost all areas that require optimal operation, reliability and robustness of the system.

An important segment of the evaluation of the closed-loop system robustness is to determine the mathematical model and its deviations wich has important influence on the result of the synthesis, wich must ensure the robustness, as well as the dynamic properties of the closed-loop control.

Deviations of the model can be divided into structural and non-structural, wich differ in the formulation of the derogation.

According to the treatment of the robustness some generalized synthesis methods have developed such as H, H2, μ-synthesis. They can be used as independent method of synthesis or as an additional tool in the context of classical design tools. Despite the same starting point of robustness evaluation, different methods are giving different results. The H∞ optimized extremes of frequency characteristics, while H2 optimize the overall frequency characteristic and is often used as aproach for energy optimizing closed-loop systems. μ-synthesis technique operates with the singular values of closed-loop characteristics and is based on D-K iteration.

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Our research area of robust control based on development of optimal robust methodologies and advanced closed-loop structures on the basis of the H∞ and H2 evaluation norms. Methods will serve as a tool for the synthesis or analysis of the system. The focus will be on developing od control algorithms for special industrial control problems, autonomous robotic systems, electric vehicles and remote closed-loop control (remote system control, teleoperation over communication networks).

For the industrial control problems solving we will focus on the synthesis of classical structures (P, PI, PID and compensators) by optimizing the robustness criteria. This will ensure the possibility of upgrading controllers in systems where it is not possible to change the structure.

For special systems such as autonomous robotic systems, electric vehicles and distibuted systems, we will develop dedicated control structures in order to achieve optimal operation, elimination of external interferences, sensor noise, non-linearity, optimal energy consumption, robust stability of inbond and outbond latency of the system etc.



Design and control of  three-axis CNC machine

 In the context of diploma work and traineeships in industry, the three-axis CNC machine in demo size was designed. The mechanical construction includes various types of drive gears (trapezoidal, spherical, sliding). The drive train was implemented with stepper motors, according to the requirements of accuracy they can operate in different modes. To achieve better accuracy the reduction of the motor axis with belt drives was carried out.

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CNC machine

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Control unit

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User interface for control and operate of the machine

The MACH3 software is used, wich allow user to control and operate the machine trough user interface

 


Design and control of inverted pendulum

In the context of diploma work the complete realization of design of the inverted pendulum on a cart was carried out.

The operating part of the system is a DC servo motor, wich drives the wheels of the cart.

The pendulum represents a steel rod with the weight, fitted on the top. The pendulum in clamped to the cart through ball bearings. The hall probe is used for measuring the angle of the pendulum.

For the control system design the mathematical model of the system is the starting point. As one of the relevant implementing regulator the LQRcontroller has been chosen. The entire control system was installed in microcontroller development platform. At the same time it was also implemented wireless communication with a PC over a serial bus.

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Concept model

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Physical description of the Inverted pendulum

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Control realization and data acquisition to the computer

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