KINEMATIC COMPENSATION OF REPETITIVE ERRORS FOR NONCIRCULAR LASER SHAPING

This paper presents an approach for kinematic compensation of the lase r shaping process which is capable of achieving improved dimensional a ccuracy for non-circular profiles. In this approach, a plug-in repetit ive controller is added into the existing position servo loop to impro ve tracking of the desired sinusoidal trajectory and subsequently redu ce tracking errors. The effect of tracking errors on different dimensi onal error modes in the non-circular shaping process is identified. Si mulation models are developed for testing the performance of the repet itive controller in shaping various non-circular profiles with differe nt operating parameters such as oscillating amplitudes and sampling ti me. Simulation results show that better tracking performance can be ob tained with the addition of the repetitive controller. Experimental re sults include fabrication of single-harmonic-term profiles such as tri angular, square, hexagonal and octagonal profiles and multiple-harmoni c-term profiles such as diamond-shaped profiles in polymethyl methacry late with both control algorithms. The non-circular profiles are measu red through optical CMM to determine the dimensional accuracy in edge straightness, angularity, parallelism and feature size.