Table 1.

Key parameters of the model

TrottingGalloping
Mass (kg)Leg length (m)Forelimb stiffness (kN m-1)Hindlimb stiffness (kN m-1)Speed (m s-1)Forelimb target speed (rad m s-1)Hindlimb target speed (rad m s-1)Neck stiffness (kN m rad-1)Back stiffness (kN m rad-1)Speed (m s-1)Forelimb target speed (rad m s-1)Hindlimb target speed (rad m s-1)Neck stiffness (kN m rad-1)Back stiffness (kN m rad-1)
Chipmunk0.1150.0480.0970.0771.20.91.10.0010.0021.81.51.90.0010.002
Dog 15.090.201.91.21.91.51.80.030.0132.82.53.10.0050.025
Dog 223.90.502.91.92.92.43.20.150.014.03.54.50.200.10
Goat25.20.484.92.72.82.33.10.190.0153.22.83.60.200.10
Horse 11340.75189.12.72.33.01.01.75.24.36.11.01.7
Horse 26761.537223.93.24.611.08.05.84.86.79.017
  • Masses and leg lengths are based on published data (Fedak et al., 1982; Farley et al., 1993).

  • Comparisons among species are made at physiologically similar running speeds (Alexander, 1988; Heglund and Taylor, 1988).

  • The basic control methods are invariant with size. Mechanical and control parameters are constrained to satisfy smooth, periodic running dynamics and biologically realistic leg stiffness. The parameters listed determine the dynamics of each ground-contact phase and are critical to the constraints.

  • The values of limb-joint stiffnesses are used for both trotting and galloping, whereas back and neck stiffnesses are gait-specific.

  • Limb target speeds are the desired tangential velocities of the feet (relative to the hip and shoulder) during stance.