Proprioception

Proprioception is a robot's internal awareness of its own body state — joint angles, velocities, accelerations, and applied torques — measured via encoders, IMUs, and torque sensors rather than external observation. Distinct from exteroception (cameras, LIDAR, depth sensors), which reads the world rather than the robot.

Proprioceptive state estimation is the foundation of whole-body control. A humanoid walking blindfolded can still maintain balance if its proprioception is reliable; one with bad encoders or noisy IMUs can't even stand still. The quality of state-estimation algorithms — typically extended-Kalman or unscented-Kalman filters fusing IMU and encoder data — directly determines locomotion robustness. Most failures in humanoid demos that look like "balance failures" are actually state-estimation failures.