Application · Human Motion System
Treat the human body as a robot, and the slope as a disturbing environment. Every movement in snowboarding is a sophisticated sensor-compute-execute closed-loop system.
System Perspective
Automatic Control Theory describes not just machines, but all systems capable of 'sensing—reasoning—acting' including your body.
The human body on a slope is a 'closed-loop control system' continuously fighting gravity. The brain acts as the controller, vestibular system and foot pressure are sensors, muscle tension is the output adjustment.
During aerial rotation (540°, 720°...), angular momentum is conserved. Tuck arms→moment of inertia decreases→angular velocity increases; extend body→slow down to align for landing—perfectly follows L = Iω.
Inner ear (gyroscope) + Eyes (vision) + Joint proprioception (IMU) → Brain uses a mechanism similar to Kalman Filter to merge multi-source sensor data and estimate 3D body posture.
Bumpy ice, powder, hard pack are all external disturbances to the system. Advanced snowboarding = improving system robustness, minimizing deviation correction time to steady state.
Closed-Loop Control
Sense
Vestibular system measures acceleration and rotational velocity; feet sense ground pressure distribution
Process
Cerebellum integrates multi-source signals, predicts next-moment posture error (Predictive Model)
Execute
Brain commands core muscles, quadriceps, calves to output corrective torque
Feedback
New posture becomes next time step input, forming closed-loop
System Maturity
System 'gain' is too low, sluggish error response. Stiff body = feedback delay. Learning goal: reduce response delay, increase sensor sensitivity.
Moderate gain, handles routine disturbances. Starting to show 'feedforward control' - predict based on terrain, adjust center of gravity before error occurs.
System has complete 'internal model'. Brain accurately simulates physics, predicts action results, achieving near-zero-error stable control.
Physics Model
Angular Momentum Conservation
L = I · ω = 常數
In air rotation: tuck body→I decreases→ω increases
Newton's Second Law (Rotation)
τ = I · α
Torque = Moment of Inertia × Angular Acceleration
Friction (Snow Surface)
f = μ · N · cos θ
μ is snow condition coefficient, θ is board cutting angle
In 'Natural Science and Artificial Intelligence' course, all these physics models have corresponding program simulations and interactive experiments.
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