Thermal regulation applied to CO2 laser surface treatments

Abstract

Real-time control of multikilowatt CO2 laser surface treatments increases reproducibility, simplifies application to workpieces of complex geometry, and provides a means to deal with varying process parameters. In order to perform a control analysis the system must be put in block diagram form. The system plant is defined as the workpiece, whose surface is illuminated by a laser beam. The system state is defined as the temperature cycling of every point within the workpiece volume. This temperature history determines the final metallurgical results. The actual output (observed) variables are temperatures in the laser reference frame. Inputs to the system include laser power, laser intensity profile, scanning velocity, and geometric or optical perturbations. Among the many control methods available, a classical control strategy was chosen for its effectiveness. The experimental application of real-time control to laser self-quenching is detailed.