Gait control by foot placement for humanoid robots

Humanoid robots are used as a research tool to understand bipedal locomotion. When pushed, a humanoid robot must be able to avoid falling and return to a balanced configuration. This is called push recovery and can be achieved using proper foot placement. Depending on the freedom of movement, one or multiple steps are taken to accomplish this goal. It is expected that foot placement can also be used to achieve controlled bipedal walking: gait control. Current foot placement strategies are limited to push recovery or restricted to bipeds with linear dynamics. The purpose of the present study is to achieve gait control by foot placement, for both a 2D biped and a 3D biped model with nonlinear dynamics. For the 2D biped model, the biped velocity at the upright standing configuration is controlled using an extension of the foot placement strategy FPE, which is normally used for 1-step push recovery. Simulations shows that desired reference velocities are obtained for various numbers of steps. For the 3D biped model, gait control is achieved using a new foot placement strategy, called FPP. This strategy is also verified in simulation, showing that gait control can be achieved for multiple reference paths. The findings are beneficial for dynamical analysis, simulation and gait control of bipedal robots.