Tuning Servomotors

Chuck Lewin, President & CEO of Performance Motion Devices (download as PDF)

Introduction

To paraphrase an adage, there are two types of motion control engineers, those that are comfortable tuning a servo loop, and those that aren’t. And if you are one of those engineers that aren’t comfortable, you in turn, have two options. The first is to use a non-servo device such as a step motor, and the second is to get comfortable!

Whether you are a relative novice, or an experienced hand with servo tuning, this article will help. It provides an overview of PID (proportional, integral, derivative) based servo loops, and introduces two standard manual tuning methods that work well for a large variety of systems. It will also provide an introduction to the increasingly popular technique of auto-tuning, which, despite the name, isn’t necessarily as automatic is it may seem. Finally, we will look at advanced servo techniques such as feedforward and frequency domain bi-quad filtering.