mu-Synthesis Based, Robust Controller Design for AMB Machining Spindles

Due to high sUrface speed and active control capabilities, active magnetic bearings (AMB's) have found a niche in high speed machining spindle applications. This paper presents a formulation of the l1-synthesis based robust controller design problem for AMB machining spindles which uses specifications based upon cutting performances such as profiling, surface finishing and rough cutting accuracy. A new method for casting the machining chatter rejection tendency in terms of Ji based performance specification is presented. With this tool, controllers can be designed such that this tendency can be minimized. The formulation also includes uncertainty representing a range of cutting tools for the spindle and the AMB's. Synthesis results indicate that this formulation is effective in achieving robust cutting and chatter rejection performance.