Revolute

Description

Joint where frame_b rotates around axis n which is fixed in frame_a.The two frames coincide when the rotation angle "phi = 0".

Optionally, two additional 1-dimensional mechanical flanges(flange "axis" represents the driving flange andflange "support" represents the bearing) can be enabled viaparameter useAxisFlange. The enabled axis flange can bedriven with elements of theModelica.Mechanics.Rotationallibrary.

In the "Advanced" menu it can be defined via parameter stateSelectthat the rotation angle "phi" and its derivative shall be definitelyused as states by setting stateSelect=StateSelect.always.Default is StateSelect.prefer to use the joint angle and itsderivative as preferred states. The states are usually selected automatically.In certain situations, especially when closed kinematic loops are present,it might be slightly more efficient, when using the StateSelect.always setting.

If a planar loop is present, e.g., consisting of 4 revolute jointswhere the joint axes are all parallel to each other, then there is nolonger a unique mathematical solution and the symbolic algorithms willfail. Usually, an error message will be printed pointing out thissituation. In this case, one revolute joint of the loop has to be replacedby a Joints.RevolutePlanarLoopConstraint joint. Theeffect is that from the 5 constraints of a usual revolute joint,3 constraints are removed and replaced by appropriate knownvariables (e.g., the force in the direction of the axis of rotation istreated as known with value equal to zero; for standard revolute joints,this force is an unknown quantity).

In the following figure the animation of a revolutejoint is shown. The light blue coordinate system isframe_a and the dark blue coordinate system isframe_b of the joint. The black arrow is parametervector "n" defining the translation axis(here: n = {0,0,1}, phi.start = 45^o).