Each limb follows a phase-shifted oscillator; the fraction of the cycle a limb spends touching the ground is the duty factor β. Stability depends on always having enough limbs in stance to keep the center of mass over the support polygon (e.g. alternating tripod gait in insects).
x_foot(t) = A · f(φ(t) + Δφ_leg)
φ(t) = 2π · freq · t
Fr = v² / (g·L) (dynamic similarity of gait)
- Gait mode — switches the limb layout: 6-leg insect tripod, 4-leg mammal trot/gallop, or undulating aquatic fin.
- Stride frequency — cycles per second of the limb oscillator; raises cadence.
- Stride amplitude — how far each limb swings, controlling stride length.
- Duty factor — fraction of cycle each limb is in ground contact; low values push toward running/flight phases.
- Body speed — forward travel speed of the whole body along its track.
Roboticists use these same phase-oscillator (central pattern generator) models to design stable hexapod and quadruped robot controllers.