Multi-objective optimization of hybrid laser cleaning process parameters for carbon deposits based on bayesian-SVR and NSGA-II

Hybrid laser cleaning combines continuous-wave (CW) laser preheating with pulsed laser ablation to remove piston crown carbon deposits, but conventional tuning cannot simultaneously minimize surface roughness (Sa) and carbon residue rate (RC). Four machine learning models—Support Vector Regression (SVR), XGBoost, Random Forest (RF), and Backpropagation Neural Network (BPNN)—are compared. SVR achieves optimal Sa prediction (Test R2 = 0.9874, bootstrap R2 = 0.985–0.998). For RC, Bayesian optimization improves SVR from R2 = 0.5658 to R2 = 0.8965 (58.45% increase). Feature analysis reveals divergent sensitivities: Sa responds equally to all parameters, while RC is dominated by frequency and CW laser power. NSGA-II generates 66 Pareto-optimal solutions within narrow parameter windows, identifying three operational regimes: low-Sa (0.894μm, RC = 4.3%), balanced (0.958μm, RC = 3%), and low-RC (RC = 1.9%, Sa = 1.209μm). Comprehensive validation—bootstrap resampling, cross-validation, SHAP analysis, and sensitivity testing—confirms model reliability despite limited data. This framework enables intelligent laser cleaning optimization, reducing trial-and-error costs while providing insights into laser–material interactions.