This is true for the most part. The majority of loops out there are still PID. Most mechanical systems are fast, simple and linearizable, and PID is robust and

This is true for the most part. The majority of loops out there are still PID. Most mechanical systems are fast, simple and linearizable, and PID is robust and simple to implement. The control law is simple. Advanced Control techniques like MPC are generally applied on complex plants such as chemical plants. In chemical plants, systems are slow but complex (highly multivariate with many interactions), so more complex optimal control techniques like MPC have a larger payoff. MPC has to solve an numerical optimization problem at every iteration, and requires more computational horsepower (not to mention prior mathematical modeling from step test data). But even in chemical plants, the local loops are PID (actually, PI... D is rarely used). The MPC layer optimizes an objective function and sends setpoints to local PI loops to carry out control.