On the use of a computed-torque control law for the terminal region of an NMPC scheme

This work addresses the advantages of using a CTC (Computed-Torque Control) law within a NMPC (Nonlinear Model Predictive Control) scheme. More precisely, the CTC law leads to stable linear closed-loop dynamics after the end of the prediction horizon. By choosing appropriate control gains, a positive invariant ellipsoidal set in which the input constraints are satisfied is determined. Using this set as terminal region in the NMPC problem, together with additional assumptions provides recursive feasibility and asymptotic stability guarantees. This proposed approach can be applied for any robotic manipulators admitting a CTC law, as a particular example. To prove its benefits some simulation results and comparisons with quasi-infinite horizon NMPC over the classical inverted pendulum dynamics are presented.