Does Pymanoid include a forward dynamics simulator?

[stephane-caron]

Forward dynamics need a reaction-force model, which is a deep question in rigid body dynamics (still the subject of active research). This stems from an essential "contradiction" of the model: physically, reaction forces depend on local deformations between bodies in contact, while the main assumption of rigid body dynamics is that bodies are not deformable. To overcome this, two main approaches have been explored: regularized reaction-force models (a.k.a. "jedi" physics) and non-smooth approaches. Both have pros and cons in terms of realism and numerical integration. For more details, check out the Wikipedia page on contact dynamics.

Pymanoid does not provide forward dynamics. The stability that is checked in simulations is a feasibility criterion called contact stability, namely, that at each timestep there exists feasible contact forces that support the robot motion. This check is performed by the find_supporting_wrenches() function of a ContactSet.