aspireai.
PUBLIC EDITION

An open-weights whole-body motion tracker for a small humanoid, trained from scratch on one GPU

AspireAI community · arXiv
SONIC-K1 adapts the SONIC motion-tracking framework to the Booster K1 humanoid, which the authors describe as the first open-weights whole-body motion tracker for that platform, and trains the policy from scratch on a single shared GPU using a small fraction of the compute reported for SONIC. In MuJoCo simulation it tracks nearly all held-out motion clips and performs well on external benchmarks under SONIC's success criterion. On the real K1 robot it tracks upper-body and slow motions reliably, while stepping and turning remain less reliable, and simulation experiments show sensitivity to action latency. The authors name quantitative hardware evaluation as the main next step. Code, policy weights and evaluation tools are published.
Read the story and explore more from the AspireAI community.
Discover more stories
Stay curious.
THE BIG PICTURE
A FRESH PERSPECTIVE
Research
One distance function matched sparse-autoencoder features across layers and compressed feature circuits into supernodes
Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.
Swipe into something new
01 / 1729
The conversation continues
Explore Builds — projects by Kiran Adimatyam ↗
A fresh perspective changes everything.
ASPIREAI — STAY CURIOUS.