“…The same happens when the methodology described in Sections 4.1 and 4.2 is applied. In these cases, adopting a correct interpretation of the Principle of Relaxation of Constraints, active forces due to control inputs can be interpreted as constraint forces and vice versa, once their primary function is to enforce the system to follow an specific trajectory in the state space, constraining the the system to it (UDWADIA, 2006). Such an analogy allows the development of an approach, based on Theorem 4.3, that leads to expressions to compute some of the constraint forces acting in a multibody system when convenient.…”