Modeling a feed axis of a Computer Numerical Controlled (CNC) machine is a challenging problem due to its time-varying dynamics and parametric uncertainties. A simple but practical system identification method was proposed in this thesis and combined with the H∞ technique to design a robust controller for a high-precision CNC milling machine. The ballscrew driven worktable of a Southwestern Industries 2OP Mill was modeled by means of a standard frequency response test. The model was linearized around the first axial resonance, and then used to synthesize an H∞ controller based on the linear matrix inequality approach. The simulated closed-loop system was subjected to disturbances and to a reference tool path to test its disturbance rejection and command following capabilities. Another simulated closed-loop system based on the machine’s actual Proportional-Integral-Derivative (PID) controller was created and subjected to the same tests in order to compare the performance of the two controllers. In all simulations, the H∞ controller displayed better performance than the PID controller.
|Commitee:||Gao, Qingbin, Marayong, Panadda|
|School:||California State University, Long Beach|
|Department:||Mechanical and Aerospace Engineering|
|School Location:||United States -- California|
|Source:||MAI 55/02M(E), Masters Abstracts International|
|Keywords:||Computer numerical control, Linear matrix inequality, Robust control|
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