Coronal Plane Control of Biped Robots Using Nonlinear Model Predictive Control for Realizing Quasi-Limit Cycle Walking

To perform three-dimensional simulations for bipedal robots, it is necessary to consider control strategies for both the coronal and sagittal planes. In our previous work on sagittal plane control, we implemented limit-cycle walking using nonlinear model predictive control (NMPC) and confirmed its effectiveness. This paper presents our approach for controlling the coronal plane. In coronal plane control, we aimed to prevent the robot from tipping over by employing a stepping-in-place strategy that keeps the Zero Moment Point (ZMP) within the foot sole. To achieve this motion, we compared the conventional method of output-zeroing control based on input-output linearization with our proposed NMPC approach, validating the effectiveness of NMPC for maintaining stability in the coronal plane.