Design of adaptive feedforward control under input constraints for a benchmark CSTR based on a BVP solver

The transition between multiple stationary setpoints of a benchmark CSTR model with different minimum-phase characteristics is solved by an adaptive feedforward control scheme. The feedforward control design treats the transition problem as a two-point boundary value problem in the coordinates of the input–output normal form, which is numerically solved with a standard Matlab function. The feedforward trajectories are calculated offline over the specified range of the inlet concentration to account for its strong influence on the system dynamics. The nominal trajectories are stored in lookup tables and an extended Kalman filter is used to adapt the feedforward control to the current inlet concentration. It is shown that the adaptation of the feedforward control acts as an integral feedback and leads to a zero steady state offset. Simulation results for a changing inlet concentration and model uncertainties show the performance and robustness of the adaptive feedforward control scheme.