On-line process control appears today as a potential way to improve thermal spray coating quality and reliability. In order to reach that goal, several requirements are needed. Firstly, reliable sensors have to be developed to accurately diagnose in-flight particle characteristics but also some other parameters, such as coating surface temperature during spraying. Secondly, a robust command, linked to a model, is required to insure the stability of the control system. Finally, an extensive and representative database is required as reference. Several methodologies can be implemented to define such a structure. Artificial Neural Networks (ANNs) and neuromimetic models, based for example on fuzzy logic, appear as an interesting way with a large potential of improvement to control non-linear systems, such as the thermal spray processes.