Omnidirectional Walking Using ZMP and Preview Control for the NAO Humanoid Robot

Fast-paced dynamic environments like robot soccer require highly responsive and dynamic locomotion. We present an implementation of an omnidirectional ZMP-based walk engine for the Nao robot. Using a simple inverted pendulum model, a preview controller generates dynamically balanced center of mass trajectories. To enable path planning, we introduce a system of global and egocentric coordinate frames to define step placement. These coordinate frames allow translation of the CoM trajectory, given by the preview controller, into leg actions. Walk direction can be changed quickly to suit a dynamic environment by adjusting the future step pattern.