WOLFRAM SYSTEM MODELER

TowingRope

Model for towing rope

Wolfram Language

In[1]:=
SystemModel["Aircraft.Examples.GliderTow.TowingRope"]
Out[1]:=

Information

This model represents a towing rope that can be used to connect a tug aircraft to another aircraft that is being towed. This model is modified from the Modelica Standard Library SpringDamperParallel model and thus works as line force with a linear spring and linear damper in parallel with the given spring constant (c) and damping constant (d) parameters. However, the force acting on the tugAircraft frame is constrained to ≤ 0, whereas the force acting on the towedAircraft frame is constrained to ≥ 0, i.e. the rope slackens and no force is applied when the distance between the frames is less than the unstretched length (sUnstretched), albeit the slackening of the rope is not visualized in the animation.

The other modification includes adding a condition for the releasing of the rope. The rope is released, meaning that no forces are any longer applied, after the input Boolean signal for the release condition (uDetach) rises from false to true for the first time. The release condition may rise and fall multiple times, for example, when it is set to a certain flight altitude as in the GliderTow example, but obviously the rope will not get reattached any longer after the first rise of uDetach. This model also outputs a Boolean signal referring to the detachment status of the rope (yDetach) and  real signal referring to the time passed from start of the simulation until the rope release (yDetachTime).

 

Parameters (8)

animation

Value: true

Type: Boolean

Description: = true, if animation shall be enabled

sUnstretched

Value: 0

Type: Length (m)

Description: Unstretched spring length

c

Value: 0

Type: TranslationalSpringConstant (N/m)

Description: Spring constant

d

Value: 0

Type: TranslationalDampingConstant (N⋅s/m)

Description: Damping constant

s_small

Value: 1e-10

Type: Distance (m)

Description: Prevent zero-division if distance between tugAircraft and towedAircraft is zero

fixedRotationAtFrame_a

Value: false

Type: Boolean

Description: =true, if rotation tugAircraft.R is fixed (to directly connect line forces)

fixedRotationAtFrame_b

Value: false

Type: Boolean

Description: =true, if rotation towedAircraft.R is fixed (to directly connect line forces)

numberOfWindings

Value: integer(ceil(sUnstretched))

Type: Integer

Description: Number of spring windings

Inputs (6)

dRope

Default Value: 0.08

Type: Diameter (m)

Description: Rope diameter

colorRope

Default Value: {0, 0, 200}

Type: Color

Description: Color of rope cylinder

specularCoefficient

Default Value: world.defaultSpecularCoefficient

Type: SpecularCoefficient

Description: Reflection of ambient light (= 0: light is completely absorbed)

dSpring

Default Value: dRope

Type: Distance (m)

Description: Spring diameter

dCoil

Default Value: dSpring / 5

Type: Distance (m)

Description: Spring coil diameter

colorSpring

Default Value: {255, 255, 0}

Type: Color

Description: Color of rope spring

Connectors (5)

tugAircraft

Type: Frame_a

Description: Frame connected to the tug aircraft

towedAircraft

Type: Frame_b

Description: Frame connected to the aircraft to be towed

uDetach

Type: BooleanInput

Description: Boolean signal for rope detachment (=true when rope is detached)

yDetach

Type: BooleanOutput

Description: Boolean output for the detachment status (=always true after detachment condition has been fulfilled once)

yDetachTime

Type: RealOutput

Description: Time passed until the rope release

Components (3)

world

Type: World

Description: World coordinate system + gravity field + default animation definition

shape_b

Type: Shape

Description: Visualizing an elementary object with variable size; all data have to be set as modifiers (see info layer)

shape

Type: Shape

Description: Visualizing an elementary object with variable size; all data have to be set as modifiers (see info layer)

Used in Examples (1)

GliderTow

Aircraft.Examples

Example of towing a glider up to cruise altitude by an electric aircraft