Speed measurement

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Dr. Számel László
Department of Electric Power Engineering

In the most of the cases, the control of the electric drives is solved by closed loop, with negative feedback. Almost every cases the feedback is considered as an ideal feedback.

In the reality ideal feedback does not exist. The sensors are never ideal, and in the modern digital control we also have to consider the „imperfection” of the signal processing. That is why I take up the question of the effect of the quality measuring, in speed control.

In the thesis after a short prelude, the tools of the measuring for electric drives will be introduced, especially the high resolution position measurers, which ones gives us position only, but the with digital signal processing we could create speed signal.

The next part is dealing with this. How to create speed signal with the todays most frequently used incremental position encoders, and its faults. In this part two methods will be introduced.

The third part describes generally the speed control of DC drives with underling current control, using the classical serial compensators. The tools of analogue and digital compensationing will be revealed. I must admit that nowadays not only serial compensationing is the only option of speed controling.

The subsequent part is about the simulations of the earlier presented, two measuring methods, and the attached speed control block, in MATLAB-SIMULINK. The results of the simulation reveal the measure and because of that the control faults and weaknesses.

The last part presents a possible amelioration of the measurement. A high accuracy measurement will be introduced, which is better beacuse of the signal processing is executed by a good software algorithm, and the different kind of position encoders (sinewave). With that kind of measuring more accuracy could be achived in position measuring, and with more accurate positon values, better speed signal could be created.


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