CMAC based modeling and closed loop control of HPDD laser welding system

The development of a CMAC (Cerebellar Model articulation Controller) based modeling method and closed loop control system are presented to estimate and control the weld fusion specified by the topside and backside bead widths of the weld pool using HPDD (High Power Direct Diode) laser as heat source. Because of the Inconvenience of using backside sensor, a topside vision sensor is applied to measure the topside and estimate the backside widths respectively by on-line image processing. The laser driver current and welding speed are selected as the control variables. Basis function CMAC based steady-state models, easier to be obtained than dynamic ones, of the nonlinear controlled process can predict the control variables in a satisfactory accuracy to shorten output response transient time, and two simple PT controllers are included in the control system to adjust the control variables to maintain outputs at the desired levels. The results of real time closed-loop control experiments of laser welding process demonstrate that the control performance can be guaranteed when fluctuations or variations in welding conditions which lead to the changing parameters of the nonlinear model.