Position Servo Theory

The position servo is implemented as a simple extension, as shown in the following figure.

To reach a given position:

  1. The position error is used to calculate the velocity that is necessary to correct it.
  2. The velocity is fed into the velocity servo, which continues to operate as described in the previous sections.

The elevation position servo works over the complete 360° interval from -90 ... +270°.

Servo motion is always directed over the top when the antenna moves from one position to another. For example if the antenna is at +200°, and a request is made to move to -30°, then the antenna traverses the 230° sector passing through 90°. This is different from the azimuth axis, where the shorter 130° path would be taken.

Figure 1. Digital Position Servo