Virtual Robot Experimentation Platform
Tutorial #1- BubbleRob
Version 3.0.5
Landstown High School Governor’s STEM & Technology Academy
Robotics Pathway
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V-REP is the Swiss army knife among robot simulators: you won't find a simulator with more
functions, features, or more elaborate APIs.
The robot simulator V-REP, with integrated development environment, is
based on a distributed control architecture: each object/model can be
individually controlled via an embedded script, a plugin, a ROS node, a
remote API client, or a custom solution. This makes V-REP very versatile
and ideal for multi-robot applications. Controllers can be written in C/C++,
Python, Java, Lua, Matlab or Urbi.
Following are just a few of V-REP's applications:
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Simulation of factory automation systems
Remote monitoring
Hardware control
Fast prototyping and verification
Safety monitoring
Fast algorithm development
Robotics related education
Product presentation
V-REP can be used as a stand-alone application or can easily be
embedded into a main client application: its small footprint and elaborate
API makes V-REP an ideal candidate to embed into higher-level
applications. An integrated Lua script interpreter makes V-REP an
extremely versatile application, leaving the freedom to the user to
combine the low/high-level functionalities to obtain new high-level
functionalities.
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BubbleRob tutorial
This tutorial will try to introduce quite many V-REP functionalities while
designing the simple mobile robot BubbleRob. The V-REP scene file
related to this tutorial is located in V-REP's installation folder's
"tutorials\BubbleRob" folder. Following figure illustrates the simulation
scene that we will design:

First of all, freshly start V-REP. The simulator displays a default
scene.

We will start by designing BubbleRob's eyes first. Instead of
importing shapes, we will directly create them as primitives.

Right click in the scene and quickly release the button: a popup
menu appears. Select [Popup menu --> Add --> Primitive shape -> Sphere] (alternatively you can also select [Menu bar --> Add -->
Primitive shape --> Sphere]),

deselect Create pure shape, then enter following values:
3

Click ok.

Move closer to the newly added shape by using the mouse wheel.

Clicking with the left button allows you to shift the camera you are
currently looking through along the clicked point.

Right click the newly added shape and move the mouse while
keeping the right mouse button down: this allows you to rotate the
camera about the clicked point.
Note: If you deselected the newly added shape, select it again by simply
clicking it with the left mouse button.

Now enter the triangle edit mode. The shape is now in triangle edit
mode:
4

Switch to page 6 with the appropriate toolbar button:

We now see the scene from above, and in orthographic projection
mode.

Move closer to the shape. Keeping the shift button down, select
several triangles at a time until you selected all triangles except for
a ring as displayed in following sequence:
Note: Remember that a shift selection will select all triangles within the
selection square, also those that are located on the other side and not
directly visible.

Try double-clicking the floating view to swap its content with the
main view. Make sure that only desired triangles are selected.

If you want to deselect a triangle, hold down the ctrl key and left
click the triangle you want to deselect.

Now, with the triangles selected, click Extract shape in the
triangle edit mode dialog. This just generated another shape with
the selected triangles.
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
Press the delete key to remove the selected triangles. The added
shape now becomes visible.

Leave the edit mode by closing the shape edit mode dialog. Switch
back to page 1.

Select the outside ring shape. All objects in the scene are also
visible in the scene hierarchy. The ring shape appears there too
and is highlighted (since selected).

Double click its icon to open the shape properties dialog. In the
dialog that just opened, click Adjust outside color.

Another dialog will open and then select Adjust ambient
component. This allows you to adjust the ambient color
component of the ring shape.

Once done, select the inner shape (the one you extracted in the
edit mode) and adjust its color in the same way as you did with the
ring shape. This is what you should have by now:
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
Next we will add another spheroid with following dimensions:
(0.02,0.02,0.015):

add a primitive sphere and in the dialog, enter 0.02 for the X and
Y-sizes, and 0.015 for the Z-size.
o Here also make sure you deselect the Create pure shape
option beforehand.

Adjust the color of the newly added shape by selecting it, then
selecting the ring shape (hold the ctrl-key down to select more
than one object),

and in the shape dialog click the Apply to selection button in the
colors section.

Now select/left click all 3 shapes in the scene and click [menu bar -> Edit --> Grouping/Merging --> Group selected shapes].
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o You can notice that all 3 shapes are now grouped and
appear as a single object in the scene hierarchy (the icon
looks like it is composed by several items). The simulator
also sees and handles the 3 shapes as a single object from
now on (as a grouped shape).
What we now have is an eye:

Next we will add the body of BubbleRob.

Add two primitive spheres of diameter 0.2 (in the dialog, enter 0.2
for the X, Y and Z-sizes on the first sphere).

When adding the second sphere, make sure the Create pure
shape option stays selected, and enter 0.2 into the X size.
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
You will notice in the scene hierarchy that the pure shape is
represented with a different icon (a cube).
o Pure shapes perform much better during dynamics
calculations (i.e. faster and more stable), they however
cannot be very complex or look very detailed. For that
reason, it is often preferable to have the underlying dynamic
content of a scene invisible. This is what we will do next:

send the pure shape into the visibility layer 9 (disabled by default).
For that, select the pure sphere you just added (select it in the
scene hierarchy), then open the object common properties dialog
box.

While the pure shape is selected, activate the 9th layer and
deactivate the first layer in the Visibility layers section.
o Optional: The pure shape is now not visible anymore, since
V-REP displays by default the first 8 layers and hides the last
8. Scene layers can be turned on/off in the layers dialog
[Menu bar --> Tools --> Layers] or by clicking the
appropriate toolbar button:

In the object common properties dialog box notice how the pure
shape has all object special properties disabled by default.

Now select the non-pure sphere and notice in the same dialog how
most object special properties are enabled by default.

In the shape dynamics properties dialog (go to the shape
properties dialog, then click Show dynamic properties dialog),
notice also how the pure sphere has the Static option unchecked
and the Respondable option checked.

The non-pure shape on the other hand has the Static option
checked and the Respondable option unchecked by default.

Now open the position and translation dialog,
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
select the two spheres representing BubbleRob's body, and in the
dialog's section 3, enter -0.1 for Along Z.

Make sure the Relative to-item is set to World.

Then click Translate selection.
o This translates all selected objects by -0.1 along the absolute
Z-axis.
o Now you can also change the color of the visible sphere (the
non-pure sphere).

Deselect all the objects (either by pressing the esc-key, or by
clicking no specific object in the scene).

Select the grouped shape in the scene hierarchy (the eye actually),
then in the same dialog but in section 2 this time, enter 0.1 for Zcoordinate (make sure the Relative to item is set to World).
o This will change the absolute Z-coordinate of all selected
objects to 0.1. The eye of BubbleRob appears at the top of
the sphere.

In the orientation and rotation dialog, in section 3, enter 60 for
Around Y, then click Rotate selection.

Now copy the eye with [Popup menu --> Edit --> Copy selected
objects]. You can also copy it with the ctrl-c key combination.

Paste the copy with [Popup menu --> Edit --> Paste buffer] (for
that operation you could also use the ctrl-v key combination).

Select one of the two superposed eyes (it doesn't matter which one
you pick)

then in the orientation and rotation dialog, in section 3, enter 30
for around Z,

clear the previously entered 60 for around Y (enter zero), then
click Rotate selection.

Select the other visible eye, enter -30 for around Z,

then click Rotate selection.
o The eyes are in place now. This is what you should have:
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Just as a side-note: in above figures you can notice that the underlying
dynamic model does not take into account the eyes.

Next we will add a proximity sensor so that BubbleRob knows when
it is approaching obstacles:

click [Menu bar --> Add --> Proximity sensor --> Cone type].

In the orientation and rotation dialog, in section 3, enter 90 for
Around Y and for Around Z,

then click Rotate selection.

In the position and translation dialog, in section 2, enter 0.1 for Xcoordinate.
o The proximity sensor is now correctly positioned relative to
BubbleRob's body.

Double-click the proximity sensor's icon in the scene hierarchy to
open its properties dialog.

Click Show volume parameter dialog to open the proximity
sensor volume dialog.

Set Angle to 30 and Range to 0.15.

Then, in the proximity sensor properties, click Adjust detection
parameters.
o This opens the proximity sensor detection parameter dialog.
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
Uncheck Don't allow detections if distance smaller than, and
check the Limited angle detection item.
o By doing so you inform the simulator that the sensor will
only detect surfaces whose angle between their normal
vector and detection ray is smaller than the indicated value
(typically, ultrasonic sensors will behave like this).

Uncheck Occlusion check.

Close that dialog.

In the scene hierarchy, double-click the proximity sensor's name,
so that you can edit its name.

Enter "sensingNose" and press enter.

Rename the invisible body sphere to "bubbleRob"
o (invisible objects' names appear in grey instead of black in
the scene hierarchy).

Group the eyes with the visible body sphere, and

rename the new grouped shape to "body".

Select [Menu bar --> Edit --> Reorient Bounding box --> Align
selected shape's coordinate “with reference frame of world”].
o This can only be done with non-pure shapes and will align
the bounding box for the shape with the world (by default,
the bounding boxes are always automatically chosen so that
their volume are smallest).

Select "body" and open the Scene Object Properties dialog box,
then click on the “Show dynamic properties dialog” button. Notice
how the Static item is checked and the “body is Respondable”
item is unchecked. This indicates that the dynamics engine will
ignore this shape; indeed, we only want the dynamics engine to
simulate the shapes that we put to layer 9, not the other ones.
Close this dialog box and then Open the object “common”
properties dialog, and while "body" is still selected notice how the
Collidable, Measurable, Renderable and Detectable items are
checked. This indicates that "body" is enabled for collision
detection, distance calculation, and is visible to vision sensors as
well as proximity sensors.
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
Select "body", "sensingNose" then "bubbleRob" and click [Menu bar
--> Edit --> Make last selected object parent].
o This attaches "body" and "sensing nose" to "bubbleRob"
(have a look at the scene hierarchy). The same operation
can directly be performed in the scene hierarchy by dragging
"body" onto "bubbleRobb", then dragging "sensingNose"
onto "bubbleRob". Select "bubbleRob" and translate it by
0.12 along the world's Z axis (use the Coordinates and
transformations dialog).

This is what you should have by now:
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
Next we will take care of BubbleRob's wheels. Create a new scene
with [Menu bar --> File --> New scene].
o We will use the second scene in order not to be disturbed by
the already existing objects in the first scene. Individual
scenes in V-REP are fully independent, however they share a
same copy buffer.

Add a pure primitive cylinder with dimensions (0.08,0.08,0.02).

With the cylinder selected, activate its 9th layer (but this time keep
the first layer also activated: the cylinder will now be visible in layer
1 and layer 9).

In the shape dialog, adjust the wheels's color.
o In the object common properties dialog, check the
Collidable, Measurable, Renderable and Detectable
items.

Set the cylinder's absolute “position” to (0.05,0.1,0.04) and its
absolute “orientation” to (-90,0,0) (you can do this in the
Coordinates and transformations dialog).

Change the name to "leftRespondableWheel".

Copy and paste the wheel, and set the absolute Y coordinate of the
copy to -0.1.

Rename the copy to "rightRespondableWheel".

Select the two wheels, copy them,

then switch back to scene 1.

Paste the wheels.

We now need to add joints (or motors) for the wheels. Click [Menu
bar --> Add --> Joint --> Revolute] to add a revolute joint to the
scene.
o Most of the time, when adding a new object to the scene,
the object will appear at the origin of the world.

Keep the joint selected and also select "leftRespondableWheel".

In the position and translation dialog, in section 2, click the Apply
to selection button at the bottom of that section,

then in the orientation and rotation dialog, in section 2 also, do the
same.
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o This sets the joint to the exact same position and orientation
as "leftRespondableWheel".

Rename the joint to "leftMotor".

Double-click the joint's icon in the scene hierarchy to open the joint
properties dialog.

Then click Show dynamic parameters to open the joint
dynamics properties dialog.

Click Motor enabled.

Copy and paste the joint and rename the copy to "rightMotor".

Set the right motor to the same position as
"rightRespondableWheel" (in the same way as you did with the left
motor).

Select "leftRespondableWheel"

then "leftMotor" and click [Menu bar --> Edit --> Make last selected
object parent].

Do the same with "rightrespondableWheel" and "rightMotor".

Now make "bubbleRob" parent of the left and right motors.
Next we will add a small slider (or caster) for the third contact point to the
ground.

Create a new scene (scene 3) and add a pure primitive sphere with
diameter 0.05.

Keep the layer 1 activated for the sphere, but in addition activate
also layer 9.

Make the shape collidable, measurable, renderable and detectable
as you did for the two wheels earlier.

Adjust its color, and set the Friction parameters to 0 (you can do
this in the shape dynamics dialog, by clicking show dynamic
properties” and then selecting “noFrictionMaterial” in the Material
dropdown box.
o Remember that there are distinct properties for the Bullet,
ODE or Vortex physics engines).

Rename the shape to "respondableCaster".
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
Add a force sensor object with [Menu bar --> Add --> Force
sensor].

Rename it to "bodyCasterLink" go to the “position” dialog box and
shift it up by 0.05.

Make "bodyCasterLink" parent of "respondableCaster".

Copy both objects, switch back to scene 1 and paste the objects.

Select "bodyCasterLink" go to the “postion” dialog box and set its
absolute x coordinate to -0.07.

Make "bubbleRob" parent of "bodyCasterLink".

Deactivate all layers except layer 12 for "bodyCasterLink".
o If you now carefully observe "respondableCaster" and
"bubbleRob" you will notice that they slightly interfere. To
avoid strange effects during dynamics simulation, we have
to inform V-REP that both objects do not mutually collide,
and we do this in following way:

Double click on the icon for “respondableCaster” and in the shape
dynamics dialog, for "respondableCaster" set the local
respondable mask to 00001111,

and for "bubbleRob" set the local respondable mask to
11110000.

This is what you should have now:
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
Run the simulation with [Menu bar --> Simulation --> Start
simulation].
o Notice how BubbleRob slightly moves.

Stop the simulation with [Menu bar --> Simulation --> Stop
simulation].
o Alternatively you can also start/pause/stop simulations with
the corresponding toolbar buttons:
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
Stability of dynamic simulations is tightly linked to masses and
inertias of the involved non-static shapes (e.g. masses should not
differ too much from each other, etc.).

Select "leftRespondableWheel", "rightRespondableWheel" and
"respondableCaster",


and click the show dynamics property button
click the “M=M*2 for all selected shapes” button three times
o The effect is that all selected shapes will have their masses
multiplied by 8.

Run the simulation and notice how stability has improved.

Stop the simulation.

Click on “Scene Objects Properties” and then click on the “Show
dynamic properties” button.

In the joint dynamics properties dialog, set Target velocity to 50
for both motors.

Run the simulation (If BubbleRob turns in a circle, then one of the
motors needs to be reset to 50).

BubbleRob now moves forward and eventually falls off the floor.

Stop the simulation and reset the Target velocity item to zero for
both motors.
Note: The object "bubbleRob" is at the base of all objects that will later
form the BubbleRob model. We will define the model a little bit later. In
the mean time, we want to define a collection of objects that represent
BubbleRob. For that we define a collection object.

Click [Menu bar --> Tools --> Collections] to open the collection
dialog.
o Alternatively you can also open the dialog by clicking the
appropriate toolbar button:
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
In the collection dialog, click Add new collection.
o A new collection object appears in the list just below. For
now the newly added collection is still empty (not defined).

While the new collection item is selected in the list, select
"bubbleRob" in the scene hierarchy,

and then click Add in the collection dialog.
o Our collection is now defined as containing all objects of the
hierarchy tree starting at the "bubbleRob" object (the
collection's composition is displayed in the Composing
elements and attributes section).

To edit the collection name, double-click it.

Rename the collection to "bubbleRobCollection".

Close the collection dialog.
Note: At this stage we want to be able to track the minimum distance
between BubbleRob and any other object. For that,

open the distance dialog with [Menu bar --> Tools --> Calculation
module properties].

Alternatively you can also open the calculation module
properties dialog with the appropriate toolbar button:

Click the “distance calc” button.

In the distance dialog, click Add new distance object and select
a distance pair: "[collection] bubbleRobCollection" - "all other
measurable objects in the scene".

This just added a distance object that will measure the
smallest distance between collection "bubbleRobCollection"
(i.e. any measurable object in that collection) and any other
measurable object in the scene.
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
Rename the distance object to "bubbleRobDistance" (double-click
the distance object).

Close the distance dialog.

When you now run the simulation, you won't see any
difference, since the distance object will try to measure (and
display) the smallest distance segment between "BubbleRob"
and any other measurable object in the scene.

The problem is that at this stage there is no other
measurable object in the scene (the shape defining the floor
has its measurable property turned off by default). At a later
stage in this tutorial, we will add obstacles to our scene.

Next we are going to add a graph object to BubbleRob in order to
display above smallest distance, but also BubbleRob's trajectory
over time. Click [Menu bar --> Add --> Graph]

and rename it to "bubbleRobGraph".

Make the graph child of "bubbleRob", and set the graph's absolute
coordinates to (0,0,0.005).

Now open the graph properties dialog by double-clicking its icon in
the scene hierarchy.

Uncheck Display XYZ-planes.

Click Add new data stream to record

and select "Object: absolute x-position" for the Data stream type,
and "bubbleRobGraph" for the Object / item to record.

An item has appeared in the Data stream recording list.
That item is a data stream of "bubbleRobGraph"'s absolute
x-coordinate (i.e. the "bubbleRobGraph"'s object absolute x
position will be recorded).

Now we also want to record the y and z positions: add those
data streams in a similar way as above. We now have 3 data
streams that represent BubbleRob's x-, y- and z-trajectories.

We are going to add one more data stream so that we are
able to track the minimum distance between our robot and
its environment.
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
Click Add new data stream to record and scroll down and select
"Distance: segment length" for the Data stream type, and
"bubbleRobDistance" for the Object / item to record.

In the Data stream recording list, rename "Data" to
"bubbleRob_x_pos", "Data0" to "bubbleRob_y_pos", "Data1" to
"bubbleRob_z_pos", "Data2" to "bubbleRob_obstacle_dist".

Select "bubbleRob_x_pos" in the Data Stream recording list and
in the Time graph properties section, uncheck Visible.

Do the same for "bubbleRob_y_pos" and
"bubbleRob_z_pos". By doing so, only the
"bubbleRob_obstacle_dist" data stream will be visible in a
time graph. Following is what you should have:
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
Next we will set-up a 3D curve that displays BubbleRob's trajectory:

click Edit 3D curves to open the XY graph and 3D curve dialog.

Click Add new curve.
o In the dialog that pops open, select "bubbleRob_x_pos" for
the X-value item, "bubbleRob_y_pos" for the Y-value item
and "bubbleRob_z_pos" for the Z-value item.

Rename the newly added curve from "Curve" to "bubbleRobPath".
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
Finally, check the Relative to world item and set Curve width to
4:

Close all dialogs related to graphs.

Now set one motor target velocity to 50,

run the simulation,
o and you will see BubbleRob's trajectory displayed in the
scene.

Stop the simulation and reset the motor target velocity to zero.
Next, let's add a visualization window for the minimum distance data
stream.

In the scene, click [Popup menu --> Add --> Floating view].

Select "bubbleRobGraph" then in the floating view right-click
[Popup menu --> View -->
o Associate view with selected graph]. Running the simulation
will not yet display anything in the graph window, since
there are still no objects (i.e. obstacles) to measure against.
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Let's now add some obstacles!

Add a pure primitive cylinder with following dimensions: (0.1, 0.1,
0.2).

For the cylinder also activate layer 9 (but keep layer 1 activated).
o We want this cylinder to be static (i.e. not influenced by
gravity or collisions) but still exerting some collision
responses on non-static respondable shapes.

For this, in the shape dynamics dialog, keep Respondable
checked but also check Static.
o In addition we want the cylinder to be detectable by
proximity sensors, measurable, collidable and renderable
too: check the appropriate items in the object common
properties dialog.

Now while the cylinder is still selected, click the object translation
toolbar button (alternatively, a click on the mouse wheel alternates
between the camera pan, the object translate and the object rotate
mode):

Now click and drag any point in the scene: the cylinder will follow
the movement while always being constrained to keep the same Zcoordinate.

Then copy the cylinder and paste it a few times into the scene and
move them to positions around BubbleRob (it is most convenient to
perform that while looking at the scene as displayed on page 6:
from the top).
o During object shifting, holding down the shift key allows to
perform smaller shift steps. Holding down the ctrl key allows
to move in an orthogonal direction to the "regular"
direction(s).
o When done, select the camera pan toolbar button:
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
Set a target velocity of 50 to the left motor and run the simulation:
o the graph view now displays the distance to the closest
obstacle and the distance segment is visible in the scene
too.

Stop the simulation and reset the target velocity to zero.
Let us now finish BubbleRob as a model definition.

For the left and right joints, deactivate layer 2 and activate layer
10.
o Joints are now hidden in layer 10.
o Instead of making an object invisible, try simply moving it to
a layer 8 levels above, so that at any time the whole scene
content can easily be inspected by activating/deactivation
scene layers.

Select "bubbleRob",

and then check the Object is model base item in the object
common properties dialog.
o An object with that item enabled will have a stippled
bounding box that encompasses all objects built on its
hierarchy. Additionally, when such an object is copied, all its
tree hierarchy is also automatically copied. This makes
handling of BubbleRob very easy and similar to handling a
single object (try to copy only the "bubbleRob" object, and
to paste it into another scene: all attached objects are also
pasted!).

Next, for each object in the "bubbleRob" tree, except for
"bubbleRob", check the Select base of model instead item in
the object common properties dialog.

Now try selecting any BubbleRob object in the scene:
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o whatever you click on BubbleRob, only its base gets
selected! BubbleRob now appears to us as a single object
(individual objects however still can be selected through the
scene hierarchy, or by holding the shift and ctrl keys down
while clicking the object).

Finally, for both joints, check the Don't show as inside model
selection checkbox.


This is what you should have by now:
Next we will add a vision sensor, at the same position and orientation
as BubbleRob's proximity sensor: click [Menu bar --> Add --> Vision
sensor --> Perspective type].

Make the vision sensor child of "sensingNose", and set the local
position and orientation of the vision sensor to (0,0,0).
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
Select the vision sensor and open its properties dialog.

Set the Far clipping plane item to 1,

and the Resolution x and Resolution y items to 256 and 256.

Open the vision sensor filter dialog by clicking Show filter dialog.

Select the filter component "Edge detection on work image" and click
Add filter.

Position the newly added filter in second position (one position up,
using the up button).

Double-click the newly added filter component and adjust its
Threshold item to 0.2,

then click OK.

Open the object common properties dialog and check the Select base
of model instead and Don't show as inside model selection
items.

At this stage you can also check the Don't show as inside model
selection item for the two joints so as to have the model bounding
box only encompass visible objects.

Move the vision sensor to layer 12.

Add a floating view to the scene, and over the newly added floating
view, right-click [Popup menu --> View --> Associate view with
selected vision sensor].

To be able to see the vision sensor's image, start the simulation.

Stop it again.
Next, we want to be able to modulate BubbleRob's velocity with a
customized user interface.

For that we will use a custom user interface: click [Menu bar -->
Tools --> Custom user interfaces] to open the custom user
interface dialog.
o Alternatively you can also access it by clicking the
appropriate toolbar button:
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
Click Add new user interface.

Enter 2 for the Client y-size item,

keep the rest unchanged and then click OK.
o A new custom user interface was added to the scene (in the
middle of the page).

Switch to page 8, and click [Popup menu --> Remove page] in
order to see the custom user interface more clearly.

In the custom user interface dialog rename it to "bubbleCtrl":

In the page view, shift-select all free cells of the custom user
interface,
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
and click Insert merged button in the custom user interface
dialog (the custom user interface dialog is context sensitive).
o The selected cells were replaced by a single button. Notice
the Button handle item when the new button is selected:
3. This number can be used at a later stage to
programmatically access that button.

Select "Slider" as type.
o The button changed to a slider.

Deselect all cells,

then select "bubbleRob" under UI is associated with select
"bubbleRob".
o This is important so that the custom user interface is also
automatically copied if "bubbleRob" is copied, or also
automatically saved if "bubbleRob" is saved as a model.

Finally, check the UI is visible only during simulation item.
Leave the custom user interface edit mode by closing its dialog.

Switch back to page 1.
The last thing what we need for our scene is a small child script that will
control BubbleRob's behavior.

Select "bubbleRob" and click [Menu bar --> Add --> Associated
child script --> Non threaded].
o This just added a non-threaded child script to the scene, and
associated it with "bubbleRob". You can also add, remove or
modify child scripts (or the main script) through the script
dialog which can be opened with [Menu bar --> Tools -->
Scripts] or through the appropriate toolbar button:
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
Double-click the little script icon that appeared next to
"bubbleRob"'s dummy icon in the scene hierarchy: this opens the
child script that we just added.

Copy and paste following code into the script editor, then close it:
if (simGetScriptExecutionCount()==0) then
-- This is executed exactly once, the first time
this script is executed
bubbleRobBase=simGetObjectAssociatedWithScript(sim_handl
e_self) -- this is bubbleRob's handle
-- following is the handle of bubbleRob's associated
UI (user interface):
ctrl=simGetUIHandle("bubbleCtrl")
-- Set the title of the user interface:
simSetUIButtonLabel(ctrl,0,simGetObjectName(bubbleRobBas
e).." speed")
leftMotor=simGetObjectHandle("leftMotor") -- Handle
of the left motor
rightMotor=simGetObjectHandle("rightMotor") -Handle of the right motor
noseSensor=simGetObjectHandle("sensingNose") -Handle of the proximity sensor
minMaxSpeed={50*math.pi/180,300*math.pi/180} -- Min
and max speeds for each motor
backUntilTime=-1 -- Tells whether bubbleRob is in
forward or backward mode
end
-- if any child script is attached to the bubbleRob
tree, this command will execute it/them:
simHandleChildScript(sim_handle_all_except_explicit)
-- Retrieve the desired speed from the user interface:
speed=minMaxSpeed[1]+(minMaxSpeed[2]minMaxSpeed[1])*simGetUISlider(ctrl,3)/1000
result=simReadProximitySensor(noseSensor) -- Read the
proximity sensor
-- If we detected something, we set the backward mode:
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if (result>0) then
backUntilTime=simGetSimulationTime()+4 end
if (backUntilTime<simGetSimulationTime()) then
-- When in forward mode, we simply move forward at
the desired speed
simSetJointTargetVelocity(leftMotor,speed)
simSetJointTargetVelocity(rightMotor,speed)
else
-- When in backward mode, we simply backup in a
curve at reduced speed
simSetJointTargetVelocity(leftMotor,-speed/2)
simSetJointTargetVelocity(rightMotor,-speed/8)
end

Run the simulation.
o BubbleRob now moves forward while trying to avoid
obstacles (in a very basic fashion).

While the simulation is still running, change BubbleRob's velocity,
and copy/paste it a few times. Also try to scale a few of them while
the simulation is still running. Be aware that the minimum distance
calculation functionality might be heavily slowing down the
simulation.

You can turn that functionality on and off in the distance dialog, by
checking / unchecking the Enable all distance calculations
item.
Using a script to control a robot or model is only one way of doing. V-REP
offers many different ways (also combined), have a look at the external
controller tutorial, or the plugin tutorial.
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