Flying humanoid robots walk on ceilings with smoother thrust control
Anti-Gravity Walking by a Flying Humanoid Robot via Thrust-Rate Input Whole-Body Model Predictive Control
Robotics
Summary
Flying robots that look like humans usually either fly or walk on the ground. This work helps these robots walk on ceilings or upside-down surfaces by improving how their controls handle forces. The researchers designed a control system that changes the force output smoothly even when the robot's feet switch contact points, avoiding sudden spikes that could cause problems. They also added special constraints to mimic support forces when the robot walks upside down. They tested these ideas with simulations and an actual robot, showing it can walk in anti-gravity conditions.
What this means in practice
- •For robotics engineers: Implement robust anti-gravity walking controllers for flying humanoids to enable movement in complex 3D environments.
- •For drone developers: Develop transformable flying robots capable of stable movement on surfaces beyond traditional flight and ground walking.
Authors
Kazuki Sugihara, Kei Okada
Abstract
Flying humanoids are expected to perform tasks in diverse environments, while their existing locomotion is mainly limited to aerial flight and ground walking. The capability to move in complex three-dimensional space can greatly expand their application range. For such walking motion on ceilings and similar anti-gravity environments, whole-body MPC is effective. However, the discontinuous changes in dynamic structure accompanying contact switching during walking can induce thrust spikes, resulting in control instability. Therefore, in this work, we propose and implement a real-time whole-body MPC framework for anti-gravity bipedal walking. First, we formulate whole-body MPC using the time derivative of thrust, namely thrust-rate, as the control input. This formulation guarantees continuity of the thrust trajectory during contact switching while preserving the sparse structure of the optimal control problem for fast computation. Second, we address the lack of natural support forces in anti-gravity environments. We introduce lower bounds on the foot-normal component of the contact force, and smoothly transfer them during the doublesupport phase. Finally, we implement the proposed framework and demonstrate anti-gravity walking by a flying humanoid through simulation and a hardware experiment. To the best of our knowledge, this is the first demonstration of multi-contact whole-body MPC for a transformable aerial robot and walking by a flying humanoid beyond the ground.