How rearfoot length influences the dynamics of flat-footed passive walking robots?

Flat-footed passive walking robots have recently attracted increasing attention due to their ability to generate humanoid gait patterns. As a typical nonlinear system, subtle variations in structural parameters, particularly rearfoot length, can substantially affect gait characteristics. This paper examines the effect of rearfoot length on traditional gait parameters, such as step length and cycle time, as well as on the strike posture of the biped robot. Notably, cusp catastrophe phenomena are observed in gait dynamics, revealing new passive gait evolution routes and enriching the diversity of achievable gait patterns. Furthermore, novel self-organized structures, including quint points and non-quantum chirality structures, are identified in the flat-footed passive walking robot, resembling behavior observed in the double pendulum model. Finally, the effects of rearfoot length on the robot’s gait parameters are further validated through experiments on the Qualisys trajectory tracking platform. A deeper understanding of rearfoot length’s influences on passive dynamic walking provides new insights into human locomotion and lays a foundation for the development of efficient control strategies.