Fast Trajectory Optimization for Legged Robots using Vertex-based ZMP Constraints
This addresses the challenge of fast and versatile motion planning for legged robots, offering a unified method for various gaits and transitions, though it appears incremental by building on existing ZMP and optimization techniques.
The paper tackles the problem of generating diverse and physically feasible motions for legged robots by combining Zero-Moment-Point approaches with trajectory optimization, introducing a vertex-based constraint representation that enables motions like walking, trotting, and push-recovery in less than a second, with feasibility demonstrated on a real quadruped robot.
This paper combines the fast Zero-Moment-Point (ZMP) approaches that work well in practice with the broader range of capabilities of a Trajectory Optimization formulation, by optimizing over body motion, footholds and Center of Pressure simultaneously. We introduce a vertex-based representation of the support-area constraint, which can treat arbitrarily oriented point-, line-, and area-contacts uniformly. This generalization allows us to create motions such quadrupedal walking, trotting, bounding, pacing, combinations and transitions between these, limping, bipedal walking and push-recovery all with the same approach. This formulation constitutes a minimal representation of the physical laws (unilateral contact forces) and kinematic restrictions (range of motion) in legged locomotion, which allows us to generate various motion in less than a second. We demonstrate the feasibility of the generated motions on a real quadruped robot.