SensorKinematicTree

A sensor attached to a link \(n_l\) of an ObjectKinematicTree at a local position \(\pLocB\) in the frame of the link, which measures one of the output variables of the kinematic tree at that point.

Parameters

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

name	type	size	default	description
name	String		‘’	sensor’s unique name
objectNumber	ObjectIndex		invalid (-1)	object number of KinematicTree to which sensor is attached to
linkNumber	UInt		invalid (-1)	(symbol: \(n_l\)) number of link in KinematicTree to measure quantities; must be given: the default is only a placeholder
localPosition	Vector3D	3	[0.,0.,0.]	(symbol: \(\LU{l}{\bv}\)) local (link-fixed) position of sensor, defined in link (\(n_l\)) coordinate system
writeToFile	Bool		True	True: write sensor output to file; flag is ignored (interpreted as False), if fileName=’’
fileName	String		‘’	directory and file name for sensor file output; empty: no file is written; a relative name is placed in exudyn.config.outputDirectory if that is set; the directory is created if it does not exist
outputVariableType	OutputVariableType		OutputVariableType::_None	OutputVariableType for sensor
storeInternal	Bool		False	true: store sensor data in memory (faster, but may consume large amounts of memory); false: internal storage not available
visualization	VSensorKinematicTree			parameters for visualization of item

Visualization parameters

The parameters of VSensorKinematicTree, given as visualization:

name	type	size	default	description
show	Bool		True	set true, if item is shown in visualization and false if it is not shown

Drawing

Drawn as all sensors.

Detailed description

Attached to

The ObjectKinematicTree objectNumber, at its link linkNumber \(n_l\) and the point localPosition \(\LU{l}{\bv}\), given in the frame of that link.

Measures

outputVariableType is one of the output variables the kinematic tree provides for a link, as its page lists them under the output variables of SensorKinematicTree - e.g. the position, velocity or rotation of that point of the link.

Mini example

#a point of a link of a kinematic tree: one prismatic link along x, pulled by a force
nTree = mbs.AddNode(NodeGenericODE2(referenceCoordinates=[0.], initialCoordinates=[0.],
                                    initialCoordinates_t=[0.], numberOfODE2Coordinates=1))
oTree = mbs.AddObject(ObjectKinematicTree(nodeNumber=nTree, jointTypes=[exu.JointType.PrismaticX], linkParents=[-1],
                                          jointTransformations=exu.Matrix3DList([np.eye(3)]),
                                          jointOffsets=exu.Vector3DList([[0,0,0]]),
                                          linkInertiasCOM=exu.Matrix3DList([np.eye(3)]),
                                          linkCOMs=exu.Vector3DList([[0,0,0]]), linkMasses=[2.]))
mLink = mbs.AddMarker(MarkerKinematicTreeRigid(objectNumber=oTree, linkNumber=0, localPosition=[0,0,0]))
mbs.AddLoad(LoadForceVector(markerNumber=mLink, loadVector=[1,0,0]))
sLink = mbs.AddSensor(SensorKinematicTree(objectNumber=oTree, linkNumber=0, localPosition=[0.5,0,0],
                                          outputVariableType=exu.OutputVariableType.Position,
                                          storeInternal=True, writeToFile=False))

mbs.Assemble()
mbs.SolveDynamic()

#local position 0.5 plus the joint coordinate F/(2m)*t^2 at t=1
exu.sys['testResult'] = mbs.GetSensorValues(sLink)[0] #0.75

Examples (Ex) and TestModels (TM) that show this item, with weblink to github: kinematicTreeConstraintTest.py (TM)