A tale of three actuators: How mechanics, business models and position sensing affect different mechatronic servo problems

Students studying control problems often learn a lot of wondrous algorithms that impart near mythical properties to the systems that they are applied to. At least this is how it works in theory and simulation. In practice, however, a thorough understanding of the system, the use model, and the market is often far more important than the differences between any two optimization algorithms. Knowing when and where a particular algorithm is useful is typically at the heart of real control problems. This paper will focus on three servo systems with which the author has had considerable experience: hard disks, optical disks, and atomic force microscopes. By examining how the particulars of these three systems affect the use of control algorithms, the author will try to extract some general lessons.