49.5 Thursday, Jan. 5 Describing gait transitions and the role of symmetry in control WILSHIN, S.D.*; HAYNES, G.C.; PORTEOUS, J.; SPENCE, A. J.; Royal Veterinary College; University of Pennsylvannia; Royal Veterinary College; Royal Veterinary College email@example.com
Gait transitions represent a natural perturbation away from steady state behaviour. As such they provide insight into how control emerges during a complex locomotor task. Here we explore the form of gait transitions and investigate the structure of the controller necessary to achieve them. We tracked the motion of five dogs (average body mass 23.5 kg, range 10.5 kg to 32 kg, average age 5.4 years, range 2 to 7.5 years, various breeds) moving on a treadmill. The dogs were ramped up through speed inducing transitions from walk to trot and trot to walk. Limb and body positions were used to compute limb phases prior to, during, and after the transition. Transition times (walk-trot: 0.17 ± 0.11 s; trot-walk 0.21 ± 0.20 s; mean ± s.d.), were estimated by fitting a logistic function and the transitions were found to be highly stereotyped (variation in relative limb phasing at mid transition walk-trot: 0.74 ± 0.27 rad; trot-walk: 0.87 ± 0.34 rad). The stereotyped nature of the transition suggests there may be an underlying mechanical or neural mechanism or constraint which locks relative phase during the transition. The underlying symmetry of the system will be used to infer the minimal control architecture sufficient achieve this transition and compared to more complex control systems. This work has a natural extension incorporating duty factor with applications in bipedal locomotion.