Dynamic Locomotion of Quadrupedal Robots over Rough Terrain

Abstract: Previous works have enabled locomotion of quadrupedal robots usingthe ZMP-based motion optimization framework on flat terrain withvarious gait patterns. Locomotion over rough terrain brings in newchallenges such as planning safe footholds for the robot, ensuring kinematicstability during locomotion and avoiding foot slippage over roughterrain etc. In this work, terrain perception is integrated into the ZMPbasedmotion optimization framework to enable robots to perform dynamiclocomotion over rough terrain.In a first step, we extend the foothold optimization framework touse processed terrain information to avoid planning unsafe footholdpositions while traversing over rugged terrain. Further, to avoid kinematicviolations during locomotion over rugged terrain, we presentadditional constraints to the ZMP-based motion optimization frameworkto solve for kinematically feasible motion plans in real-time. Weadd nonlinear kinematic constraints to existing nonlinear ZMP motionoptimization framework and solve a Sequential Quadratic Programming(SQP) problem to obtain feasible motion plans. Lastly, to avoidfoot contact slippage, we drop the approximated terrain normal anduse measured terrain normal at foot contact position to compute thefriction polygon constraints.The proposed algorithms are tested in simulation and on hardwarewith dynamic gaits to validate the effectiveness of this approach toenable quadrupedal robots to traverse rugged terrain safely. The computationaltime and performance of the proposed algorithms were analyzedunder various scenarios and presented as part of this thesis.