LoadCoordinate

Load with scalar value, which is attached to a coordinate-based marker; the load can be used e.g. to apply a force to a single axis of a body, a nodal coordinate of a finite element or a torque to the rotatory DOF of a rigid body.

Interface

Markers it acts on: those providing Coordinate: MarkerNodeCoordinate, MarkerNodeODE1Coordinate, MarkerNodeRotationCoordinate, MarkerBodiesRelativeTranslationCoordinate, MarkerBodiesRelativeRotationCoordinate, MarkerBodyCable2DShape, MarkerBodyCable2DCoordinates

Parameters

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

name	type	default	description
name	String	‘’	load’s unique name
markerNumber	MarkerIndex	invalid (-1)	marker’s number to which load is applied
load	Real	0.	(symbol: \(f\)) scalar load [SI:N]; in case of a user function, this value is ignored
loadUserFunction	LoadCoordinateLoadUserFunction	0	(symbol: \(\mathrm{UF} \in \Rcal\)) A Python function which defines the time-dependent load and replaces the load; see description below; see also notes on loadFactor and drawing in LoadForceVector!
visualization	VLoadCoordinate		parameters for visualization of item

Visualization parameters

VLoadCoordinate has no parameters.

Drawing

The item draws nothing.

Detailed description

Load and its frame

The scalar \(f\) = load, or the return value of loadUserFunction, acts on one coordinate: the one the coordinate marker selects, e.g. MarkerNodeCoordinate. It has no frame of its own: it is a generalized force in the direction of the coordinate, which is a force for a displacement coordinate and a torque-like quantity for a rotation parameter - for Euler parameters or a slope, not a torque in the physical sense, so take care what the coordinate means.

Generalized forces

\[ Q_i = f \]

for the marked coordinate \(i\), and zero for all others. The load factor applies as for a force.

Userfunction: loadUserFunction(mbs, t, load) A user function, which computes the scalar load depending on time and the object’s load parameter.

arguments / return	type or size	description
`mbs`	MainSystem	provides MainSystem mbs to which load belongs
`t`	Real	current time in mbs
`load`	Real	\(\bv\) copied from object; WARNING: this parameter does not work in combination with static computation, as it is changed by the solver over step time
return value	Real	computed load

Example:

from math import sin, cos, pi
#this example uses the object's stored parameter load to compute a time-dependent load
def UFload(mbs, t, load):
    return load*sin(10*(2*pi)*t)

n0=mbs.AddNode(Point())
nodeMarker = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=n0,coordinate=0))
mbs.AddLoad(LoadCoordinate(markerNumber = markerCoordinate,
                           load = 10,
                           loadUserFunction = UFload))

Mini example

#a load on one coordinate, growing in time through its user function
node = mbs.AddNode(Node1D(referenceCoordinates=[0]))
mbs.AddObject(ObjectMass1D(nodeNumber=node, mass=1))
mCoord = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=node, coordinate=0))
def UFload(mbs, t, load):
    return load*t
mbs.AddLoad(LoadCoordinate(markerNumber=mCoord, load=1, loadUserFunction=UFload))

mbs.Assemble()
mbs.SolveDynamic()

#q = t^3/6 at t=1
exu.sys['testResult'] = mbs.GetNodeOutput(node, exu.OutputVariableType.Coordinates) #0.1667

Examples (Ex) and TestModels (TM) that show this item, with weblink to github: tutorialSpringDamper.py (Ex), coordinateSpringDamper.py (Ex), plotSensorExamples.py (Ex), slidercrankWithMassSpring.py (Ex), CoordinateSpringDamperTest.py (TM)