User guide

➃ Servo Tuning 21
C H A P T E R ➃
Servo Tuning
In a Hurry?
We strongly recommend tuning the 6250 before attempting to execute any motion functions.
If you must execute motion quickly (e.g., for testing purposes), you should at least complete
the Tuning Setup Procedure and Drive and Controller Tuning Procedures (see pages 29 - 38)
until you have found a proportional feedback gain that can give a stable response for your
system. Then you can proceed to execute your motion functions. Later on, you should read
through this entire Servo Tuning chapter and follow its procedures to ensure your system is
properly tuned.
Servo System Terminology
This section gives you with an overall understanding of the principles and the terminology
used in tuning the Compumotor 6250 Servo Controller.
Servo Tuning Terminology
The 6250 uses a digital control algorithm to control and maintain the position and velocity.
The digital control algorithm consists of a set of numerical equations used to periodically
(once every servo sampling period) calculate the value of the control signal output.
The numerical terms of the equations consist of the current commanded and actual position
values (plus a few from the past sampling period) and a set of control parameters. Each
control parameter, commonly called a gain, has a specific function (see Servo Control
Techniques later in this chapter). Tuning is the process of selecting and adjusting these gains
to achieve optimal servo performance.
When this control algorithm is used, the whole servo system is a closed loop system (see
diagram below). It is called closed loop because the control algorithm accounts for both the
command (position, velocity, tension, etc.) and the feedback data (from the encoder);
therefore, it forms a closed loop of information flow.