Decoupled Whole-Body Control

A humanoid setup where the lower body uses reinforcement learning to walk and balance, and the upper body uses inverse kinematics to control the arms.

This is an engineering-pragmatic approach to humanoid whole-body control that splits the robot into two separate controllers. The lower body runs a walking policy trained with reinforcement learning in simulation, taking commands like forward speed, turning, and body height, and handling walking, crouching, and balance — trained with randomized upper-body poses so it learns to treat arm motion as a disturbance it can absorb. The upper body is controlled directly by inverse kinematics (IK, computing joint angles from a desired hand pose) or by a teleoperation device's joint mapping. The benefit is a clean division of labor and accurate arm positioning, convenient for teleoperated data collection and for hooking up a VLA model; the cost is that the two halves aren't coordinated, so motions requiring the whole body to work together — bending down to reach the floor, leaning forward to extend reach, exerting full-body force to move something heavy — don't come out well. NVIDIA's GR00T N1.5 and N1.6 use exactly this controller (RL lower body, IK upper body) on the Unitree G1, though its official VLA pipeline switched starting in 2026 to work with a unified whole-body controller, SONIC, instead.

ExampleHOMIE (Shanghai AI Lab et al., 2025): the operator uses foot pedals to send walk/turn/crouch commands to the lower-body RL policy, while the arms are controlled by a joint-matched isomorphic exoskeleton and the hands by motion-capture gloves — letting a single person teleoperate the humanoid to walk and manipulate at the same time while collecting training data.

Also called

Decoupled WBC, Upper/Lower Body Split Control, Upper-Body IK + Lower-Body RL

Related

Whole-Body Control · Learning-Based Whole-Body Control · Inverse Kinematics (IK) · RL-based Locomotion Control · Loco-manipulation · SONIC

Sources

NVlabs/GR00T-WholeBodyControl（Decoupled WBC: RL for lower body, IK for upper body）
HOMIE: Humanoid Loco-Manipulation with Isomorphic Exoskeleton Cockpit (arXiv:2502.13013)

As of

2026-05