ABSTRACT
Having discussed individual components of industrial servo drives from an operation point of view and a mathematical descriptive point of view, the next step is to combine these components into a block diagram for the complete servo drive. The block diagram is a powerful method of system analysis. In the block diagram each component in a servo system can be described by the ratio of its output to input. Thus the output of one component is the input to the next component. To satisfy an accuracy requirement some form of feedback is required. For a velocity servo drive the output is speed. Without velocity feedback, the speed will vary greatly with changes in load. By providing negative feedback with the use of a tachometer, the feedback voltage is compared with a reference command voltage input by means of a summing junction. The difference in the two voltages (command and feedback) is the error voltage. For a velocity servo drive the error is finite. As load increases the drive slows down, the feedback voltage gets smaller, and the error increases, causing the speed regulator to speed up and maintain the required velocity.
