Give a robot the sense to feel its own limits.
Proprioception for Physical AI
The Physics of Distribution Shift
Learned policies and vision-language-action models optimize for task completion across a training distribution. They operate in the semantic layer, predicting trajectories from visual tokens without a deterministic model of momentum, braking distance, or recovery reachability.
Physical deployments inevitably encounter structural distribution shift. When the workspace presents an unmapped obstacle, a shifted payload, or an unexpected human movement, the policy defaults to its statistical mean. The agent executes this generated trajectory directly into the physical infrastructure, translating a probabilistic error into a kinetic collision.
Hardware interlocks only trip after a physical boundary is breached. Between the learned policy and the safety PLC, the hardware attempts to execute a software hallucination at full mechanical torque.