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DiffWBC replaces deterministic humanoid tracking policies with a one-step diffusion controller, and steers it online without retraining

AspireAI community · arXiv (cs.RO)
General humanoid motion trackers use deterministic policies that cannot adapt online without brittle reference editing or costly retraining. DiffWBC moves whole-body control to a generative paradigm with a one-step diffusion model that models distributions over future trajectories, unifying general tracking, test-time steering and simulation-free failure discovery in one controller. It needs a single forward pass per 50 Hz control step, can be distilled from an RL teacher or trained from scratch via model-based RL, and reports the lowest local tracking error among six general trackers on held-out benchmarks at 20.1 mm on BONES, with deployment on a physical Unitree G1. Zero-shot test-time steering uses differentiable cost gradients and body-group masks to modulate the frozen controller, beating kinematic reference editing at 0.84 clean pass versus 0.10 under a 1.25 m ceiling, and generalizing to hurdles, spatial reaching, actuator faults and tray balancing. Planning dispersion across generation noise identifies physical tracking failures with 91 percent precision in the top 2 percent without physics simulation, and targeted fine-tuning on flagged clips resolves 50 percent of failure cases.
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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.
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