Abstract: The goal of this paper is to develop a unifed online motion generation scheme for quadruped lateral-sequence walk and trot gaits based on a linear model predictive control formulation. Specifcally, 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 unifed 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 unifed scheme can generate stable locomotion online for quadruped lateral-sequence walk and trot gaits, both in simulation and on hardware. The results show signifcant performance improvements compared to previous work. Moreover, the results also suggest the linearly simplifed scheme has the ability to robustness against unexpected disturbances.

Key words: Motion generation , · Gait pattern conversion , · Model predictive control , · Quadruped locomotion