SensorBody

A sensor attached to a body at a local position \(\pLocB\), which measures one of the output variables of the body at that point.

Parameters

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

name	type	size	default	description
name	String		‘’	sensor’s unique name
bodyNumber	ObjectIndex		invalid (-1)	body (=object) number to which sensor is attached to
localPosition	Vector3D	3	[0.,0.,0.]	(symbol: \(\pLocB\)) local (body-fixed) body position of sensor
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	VSensorBody			parameters for visualization of item

Visualization parameters

The parameters of VSensorBody, 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 body bodyNumber, at the point localPosition \(\pLocB\). The local position is given in the body frame and measured from the reference point of the body - the position of its node, which is referencePosition in CreateRigidBody. The center of mass of an ObjectRigidBody lies at centerOfMass from it, so a sensor at the center of mass has that local position.

Measures

outputVariableType is one of the output variables of the body, evaluated at \(\pLocB\), as its page lists them under Output variables - e.g. Position, Velocity, Displacement, AngularVelocity; for a flexible body also strains or forces along its axis.

Mini example

#a point of a body given by its local position: a planar rigid body spinning about its center
node = mbs.AddNode(NodeRigidBody2D(referenceCoordinates=[0.5,0.2,0], initialVelocities=[0,0,0.5*np.pi]))
body = mbs.AddObject(ObjectRigidBody2D(nodeNumber=node, mass=1, inertia=0.1))
sPoint = mbs.AddSensor(SensorBody(bodyNumber=body, localPosition=[0.5,0,0],
                                  outputVariableType=exu.OutputVariableType.Position,
                                  storeInternal=True, writeToFile=False))

mbs.Assemble()
mbs.SolveDynamic()

#after a quarter turn the point [0.5,0,0] of the body at [0.5,0.2] is at [0.5,0.7,0]
exu.sys['testResult'] = mbs.GetSensorValues(sPoint)[1] #0.7

Examples (Ex) and TestModels (TM) that show this item, with weblink to github: tutorialSpringDamperCreate.py (Ex), tutorialRigidBody.py (Ex), tutorialRigidBodyCreate.py (Ex), fourBarMechanism3D.py (Ex)