Conceptual models for real-world locomotion

During human and animal locomotion, the dynamics of the body can be represented with the help of simplified biomechanical models, such as the spring-mass model (often described as spring-loaded inverted pendulum, SLIP model). In this model, it is assumed that the force generated by each limb resembles that of a linear spring. Furthermore, it is assumed that force generated by the leg mainly acts in leg axis, e.g. the connecting line between contact point (foot) and body (center of mass). Finally, the contact point at the ground is considered fixed during ground contact. Although all of these assumptions are considerable simplifications compared to most biological and artificial legged systems, this gait model provides a useful template for developing more detailed gait models taking leg segmentation (thigh, shank, foot), non-elastic leg properties (e.g. damping, variable leg spring properties), upper body (trunk), neuro-muscular properties (e.g. reflexes) and multiple legs (e.g. bipedal configuration) into account.