Flying humanoid robots learn to walk upside down using new control methods
Anti-Gravity Walking by a Flying Humanoid Robot via Thrust-Rate Input Whole-Body Model Predictive Control
Robotics
Summary
Walking on ceilings or walls is tricky because robots need to control how they push off surfaces without sudden jerks that make them unstable. The researchers created a new way to control a flying humanoid robot’s movements by smoothly changing the thrust it uses to stick and walk in these upside-down or anti-gravity places. They tested this method in both computer simulations and real robot experiments, showing the robot can now walk in three-dimensional spaces beyond just flying and ground walking. This work opens up new possibilities for robots to move in complex environments.
flying humanoid robotanti-gravity walkingwhole-body model predictive controlthrust-rate inputcontact switchingmulti-contact locomotionforce constraintsbipedal walkingrobot dynamicshardware experiment
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.