Stability Analysis and Design of Momentum-based Controllers for Humanoid Robots
This addresses the challenge of robust balancing and walking control for humanoid robots, which is critical for applications but remains an incremental improvement in control design.
The paper tackled the instability of momentum-based controllers for humanoid robots by showing that state-of-the-art strategies can lead to unstable zero dynamics, and proposed modifications to avoid these instabilities, achieving asymptotic stability validated through simulations and experiments on the iCub robot.
Envisioned applications for humanoid robots call for the design of balancing and walking controllers. While promising results have been recently achieved, robust and reliable controllers are still a challenge for the control community dealing with humanoid robotics. Momentum-based strategies have proven their effectiveness for controlling humanoids balancing, but the stability analysis of these controllers is still missing. The contribution of this paper is twofold. First, we numerically show that the application of state-of-the-art momentum-based control strategies may lead to unstable zero dynamics. Secondly, we propose simple modifications to the control architecture that avoid instabilities at the zero-dynamics level. Asymptotic stability of the closed loop system is shown by means of a Lyapunov analysis on the linearized system's joint space. The theoretical results are validated with both simulations and experiments on the iCub humanoid robot.