In research on passive dynamic walking, the aim is to study and design robots that walk naturally, i.e., with little or no control effort. McGeer [1] and others (e.g. [2, 3]) have shown that, indeed, robots can walk down a shallow slope with no actuation, only powered by gravity.\ud
In this work, we derive mathematical models of walking ro- bots to better understand the dynamics that determine the walking behavior, and to design controllers that e.g. in- crease robustness against changing environments. We use the port-Hamiltonian framework, as it has the advantage of explicitly showing energy-flows inside and into the system. Thus, it allows a direct efficiency study as well as the possi- bility to connect external elements in a ‘physical’ way using ports, instead of using just torque/force signals