Actuator Dynamics-Aware Model Predictive Control of a Wheeled Inverted Pendulum with a Fan

Abstract

Wheeled Inverted Pendulum (WIP) systems offer agile mobility but are challenging to control due to their unstable and underactuated dynamics. To address these limitations, we develop a Wheeled Inverted Pendulum with a Fan (WIPF), which incorporates a fan-generated bidirectional thrust force as an additional control input. This makes the system fully actuated and enhances stability; however, the limited bandwidth of the fan thrust introduces control challenges. In this letter, we propose a Frequency-Shaped Model Predictive Control (FSMPC) design framework that accounts for actuator dynamics in the optimization process, and is expandable to other systems with different actuator dynamics. The proposed FSMPC can provide improved stability by penalizing high-frequency input using the frequency response of the fan. The nonlinear solver enables control input updates at rates exceeding 1 kHz, meeting real-time control requirements. The performance of FSMPC with the proposed design framework is compared through simulations and experiments against a Linear Quadratic Regulator (LQR), a standard Model Predictive Controller (MPC), and a Frequency-Shaped LQR (FSLQR) that does not consider fan dynamics or the input constraint. The results demonstrate that FSMPC achieves improved stability and robustness compared to other controllers.