(Dr. Thomas R. Kurfess, advisor)
"Implementation of a Fast Tool Servo with Repetitive Control for a Diamond Turning Machine"
Diamond Turning machines have been used for achieving high quality surface finishes with applications that have ranged from the manufacturing of detonators for nuclear weapons to hard drive platters to the generation of precision optics. With improved computer processing performance, the ability to incorporate Fast Tool Servo's (FTS) with diamond turning machines has opened up the areas of disturbance rejection, generation of micro-structures, and non-aspherically symmetric surfaces - applications once difficult due to the inertia's and positioning precision involved.
The goal of this research is to implement a Fast Tool Servo for facing operations on a Diamond Turning Machine. Polynomial control design is used to develop a disturbance rejection controller for the FTS. Also, a repetitive controller is implemented to better compensate for periodic disturbances at the spindle frequency and its harmonics by monitoring the spindle face. The FTS consists of a cross-roller bearing slide under a pre-load with a piezoelectric stack being used for actuation. A strain gauge is used for position feedback and an eddy current probe is used to provide the desired tool position based on spindle face deflection. An analysis of the resulting surface finish quality is performed to determine the effectiveness of the mechanism and controllers with respect to surface roughness and waviness (parallelism).