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ExBody2

UC San Diego·UC Berkeley·MIT · 2024-12

VAHumanoid whole-body controllersNot disclosedRL policy

Automatically filters training motions with a tracking-error threshold τ* = 0.150 to track expressive whole-body motions.

View architecture diagram in the galleryPaper ↗

Paper

ExBody2: Advanced Expressive Humanoid Whole-Body ControlarXiv 2412.13196

Overview

Category
Humanoid whole-body controllers
Type
VA
Released
2024-12
Organization
UC San Diego·UC Berkeley·MIT
Open weights
Unverified
Parameters
Not disclosed (student MLP [1024, 1024, 512])

Architecture

Backbone LLM
None
Vision encoder
—
Action head
Joint PD targets (RL policy)
Chunk
Not disclosed
Control rate
50 Hz (low-level 500 Hz)
Architecture (original summary)
MLP: teacher actor·value [512, 256, 128], student [1024, 1024, 512], proprioceptive history 10; motion targets + proprioception → joint PD targets, policy 50 Hz·low-level 500 Hz

Training

Pretraining accelerators
Not disclosed (IsaacGym)
Pretraining duration
Not disclosed
Pretraining steps & batch
Not disclosed (env count Not disclosed)
GPU/TPU-hours
Not disclosed
Fine-tuning
N/A
Data type
Motion capture
Data scale
CMU motion capture 1,919 sequences (before filtering); size after filtering not disclosed
Main datasets
CMU motion capture
Tasks & evaluation
MPKPE·MPJPE tracking error compared against 4 baselines
Robot
Unitree G1(23 DoF)

Inference

Inference device & speed
Policy 50 Hz, low-level 500 Hz, communication latency 18–30 ms; onboard Jetson Orin NX
Inference memory
Not disclosed
Weights bf16 (calc.)
Not disclosed
Where it runs
Onboard (Jetson Orin NX)

Reinforcement learning & base

Reinforcement learning
Used (RL controller training) · RL teacher (privileged information, actor-critic) → student distillation
Base control
Humanoid legged (RL policy drives joints directly) · Tracks whole-body keypoint and root velocity goals, outputting 23-dim joint PD targets including legs (walking, crouching, dancing)

Notes

Key features
Automatically filters training motions with a tracking-error threshold τ* = 0.150 to track expressive whole-body motions. Runs onboard on Jetson Orin NX.
Notes
Selection error e(s) = 0.1·E_key + 0.9·E_dof (extraction). Not covered by the verification file.
Verification
Not verified

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