This paper presents a technique for the automatic tuning of industrial proportional-integral-derivative (PID) regulators, based on a classifier that selects an appropriate model structure for the system to be controlled starting from a simplified and normalized representation of its unit step response. The PID tuning is then performed within the well-established framework of the internal model control approach, showing that structural information is particularly beneficial for model-based synthesis. Both simulations and a physical application, based on a laboratory thermal process, are reported