A Unified Motion Generation Approach for Quadruped L-S Walk and Trot Gaits Based on Linear Model Predictive Control

Abstract

The goal of this paper is to develop a unified online motion generation scheme for quadruped lateral-sequence walk and trot gaits based on a linear model predictive control formulation. Specifically, the dynamics of the linear pendulum model is formulated over a predictive horizon by dimensional analysis. Through gait pattern conversion, the lateral-sequence walk and trot gaits of the quadruped can be regarded as unified biped gaits, allowing the dynamics of the linear inverted pendulum model to serve quadruped motion generation. In addition, a simple linearization of the center of pressure constraints for these quadruped gaits is developed for linear model predictive control problem. Furthermore, the motion generation problem can be solved online by quadratic programming with foothold adaptation. It is demonstrated that the proposed unified scheme can generate stable locomotion online for quadruped lateral-sequence walk and trot gaits, both in simulation and on hardware. The results show significant performance improvements compared to previous work. Moreover, the results also suggest the linearly simplified scheme has the ability to robustness against unexpected disturbances.