MarkerNodeCoordinates

A node-Marker attached to all ODE2 coordinates of a node. IN CONTRAST to MarkerNodeCoordinate, the marker coordinates INCLUDE the reference values! For ODE1 coordinates use MarkerNodeODE1Coordinates.

Interface

Provides: Coordinates
Connectors, constraints and loads that can use it: ObjectConnectorCoordinateVector

Parameters

The parameters of the item; in a dictionary, its type is ‘NodeCoordinates’:

name	type	default	description
name	String	‘’	marker’s unique name
nodeNumber	NodeIndex	invalid (-1)	node number to which marker is attached to
visualization	VMarkerNodeCoordinates		parameters for visualization of item

Visualization parameters

VMarkerNodeCoordinates has no parameters.

Drawing

The item draws nothing.

Detailed description

Marker quantities

quantity	symbol	as computed
coordinates	\(\cv = \qv\cRef + \qv\)	all ODE2 coordinates of the node, including their reference values
their velocities	\(\dot\cv = \dot\qv\)	the time derivatives

Unlike MarkerNodeCoordinate, the values include the reference values.

Jacobians

The unit matrix of the size of the node’s coordinates: a vector of forces acts on the coordinates one by one. On a node without ODE2 coordinates the values and the Jacobian are empty.

Mini example

#all coordinates of two nodes, tied by a coordinate vector constraint X1 qB - X0 qA = offset; the
#coordinates INCLUDE the reference values, so qB - qA = [1,0,0] keeps the two points where they are
nA = mbs.AddNode(NodePoint(referenceCoordinates=[0,0,0]))
nB = mbs.AddNode(NodePoint(referenceCoordinates=[1,0,0]))
mbs.AddObject(ObjectMassPoint(nodeNumber=nA, mass=1))
mbs.AddObject(ObjectMassPoint(nodeNumber=nB, mass=1))
mA = mbs.AddMarker(MarkerNodeCoordinates(nodeNumber=nA))
mB = mbs.AddMarker(MarkerNodeCoordinates(nodeNumber=nB))
mbs.AddObject(ObjectConnectorCoordinateVector(markerNumbers=[mA, mB], scalingMarker0=np.eye(3),
                                             scalingMarker1=np.eye(3), offset=[1,0,0]))
mbs.AddLoad(LoadForceVector(markerNumber=mbs.AddMarker(MarkerNodePosition(nodeNumber=nA)), loadVector=[2,0,0]))

mbs.Assemble()
mbs.SolveDynamic()

#both masses move together: a = F/(2m) = 1, x = a/2*t^2 at t=1
exu.sys['testResult'] = mbs.GetNodeOutput(nB, exu.OutputVariableType.Displacement)[0] #0.5

Relevant Examples (Ex) and TestModels (TM) with weblink to github: coordinateVectorConstraint.py (TM), coordinateVectorConstraintGenericODE2.py (TM), rigidBodyAsUserFunctionTest.py (TM)