Biped Stabilization by Linear Feedback of the Variable-Height Inverted Pendulum Model
This work addresses bipedal robot stability, particularly for humanoid robots, by proposing an incremental improvement through a new balancing strategy.
The authors tackled bipedal robot stabilization by introducing a variable-height inverted pendulum (VHIP) model that uses height variations for balancing, in addition to ankle strategies, and implemented a linear feedback stabilizer that matches state-of-the-art performance for small perturbations and recovers from larger ones, as tested on the HRP-4 humanoid robot.
The variable-height inverted pendulum (VHIP) model enables a new balancing strategy by height variations of the center of mass, in addition to the well-known ankle strategy. We propose a biped stabilizer based on linear feedback of the VHIP that is simple to implement, coincides with the state-of-the-art for small perturbations and is able to recover from larger perturbations thanks to this new strategy. This solution is based on "best-effort" pole placement of a 4D divergent component of motion for the VHIP under input feasibility and state viability constraints. We complement it with a suitable whole-body admittance control law and test the resulting stabilizer on the HRP-4 humanoid robot.