Universal Testing Machines or those of similar type are equipped with a feedback control mechanism for motion control. These systems have the following components:

1- Motor turn
2- Servo (or DC) motor gearbox
3- Complete shaft rotation
4- Ball screw lead
5- Quadrature encoder lines
6- Vertical displacement of cross bars

In 3000 words total give a comprehensive explanation of how such (motion control) systems operate? Your research should start with a brief explanation of above terms followed a clear and complete description of how those terms relate to each other and play role in the whole mechanism of motion control. Your writing should include in-text citation and end of list referencing. Websites without author and publication date are not accepted as a source of reference. You might find following sources useful to start research:

1- Pages 10 to 15 (inclusive) of http://www.national.com/an/AN/AN-693.pdf

2- http://www.youtube.com/watch?v=aEdvuc2Qxyw