Precise positioning of an AMB spindle using 2-DOF controller

This paper describes the design of a high performance 2-DOF controller for an electromechanical system consisting of a rotary flexible spindle hovered by Active Magnetic Bearings (AMB). The purpose of such a controller is to achieve the better positioning possible of the spindle by mean of a good stabilization mechanism and by counteracting the vibrations generated naturally by the rotation. The implementation of this controller is based on three main blocks, a stabilization block, a vibration minimization block and, if needed, a dynamics decoupler block between the two mentioned blocks. Two different stabilization blocks (PID and ℋ_∞), designed utilizing a MIMO decoupling technique, are presented and an adaptive feedforward controller block is in charge of the vibration minimization. In order to do not feedback the vibration and, therefore, to decouple the controllers dynamics the implementation of a variable Notch filter is discussed.