Advanced Real-Time Iterations and Short-Horizon Predictor for Fast Nonlinear Model Predictive Control

Nonlinear Model Predictive Control (NMPC) is a powerful and versatile controller scheme, whose computational demands often lead to control delays that are unaccounted for in analysis. Fast NMPC schemes such as Advanced Step NMPC (asNMPC) and Real-Time Iterations (RTI) attempt to compensate by respectively removing control delay and minimizing sampling time. This paper introduces Advanced Real-Time Iterations (aRTI), combining concepts from asNMPC and RTI in order to take advantage of both of their strengths. In this way, aRTI can achieve very small control delays, while attaining very fast control rates. Additionally, we propose the Short-Horizon predictor (SH-predictor) to lower the computational demands of preparing a tangential predictor. Simulations of a perturbed ‘pendulum on cart’ system demonstrate the effectiveness of aRTI and SH-predictor in achieving high control performance, reducing computational loads, and minimizing control delay.