Layer-to-Layer Height Control for Laser Metal Deposition Process

A laser metal deposition height control methodology is presented in this paper. The height controller utilizes a particle swarm optimization (PSO) algorithm to estimate model parameters between layers using measured temperature and track height profiles. Using the estimated model, the powder flow rate reference profile, which will produce the desired layer height reference, is then generated using iterative learning control (ILC). The model parameter estimation performance using PSO is evaluated using a four-layer single track deposition, and the powder flow rate reference generation performance using ILC is tested using simulation. The results show that PSO and ILC perform well in estimating model parameters and generating powder flow rate references, respectively. The proposed height control methodology is then tested experimentally for tracking a constant height reference with constant traverse speed and constant laser power. The experimental results indicate that the controller performs well in tracking constant height references in comparison with the widely used fixed process parameter strategy. The application of layer-to-layer height control produces more consistent layer height increment and a more precise track height, which saves machining time and increases powder efficiency.