This is the same Ib-reflex model as the 3D circuit — a saturating, Hill-type tension–firing law feeding a gated feedback term — but rendered as three mathematical views instead of an animated nerve pathway:
FR(F) = FR_max · F^p / (F^p + F_h^p)
drive(F) = clamp( load + gate · gain · (FR(F)/FR_max) · 45, 0, 100 )
dF/dt = ( drive(F) - F ) / τ
- Top-left — Hill curve. GTO firing rate vs. tendon force; the dot is the current operating point.
- Top-right — phase-line diagram. Plots
drive(F) (solid) against the identity line y=F (dashed). Where they cross is a fixed point (dF/dt=0); arrows on the axis show whether force is being pushed up or down at each point, which is exactly the stability argument for why the stance-phase positive-feedback loop settles instead of running away.
- Bottom — strip chart. Force, drive and scaled firing rate scrolling over the last 12 s, so you can watch the system relax toward the equilibrium marked in the phase-line panel.
Quiet standing: gate = −1, so rising force reflexively cuts drive (inhibitory) and the fixed point sits below the load demand. Stance phase: gate = +1, rising force reflexively adds drive (positive feedback), pushing the fixed point above the load demand — but the Hill curve's saturation keeps the slope of drive(F) below 1 near the crossing, so the loop is still locally stable. Swing: gate = 0, force simply relaxes toward the load demand.