- I'm going to present strut modeling.
Strut modeling is a project done
in collaboration with University of Hasselblad,
with Raf Ramakers, who's also here,
and Kris Luyten.
So strut modeling is a low fidelity construction kit
that consists out of struts and hubs.
What the user can do is they can just simply connect
a strut to a hub and build in the physical space.
In the background, you can see that the struts are tracked
in real time in a virtual environment.
When user builds a 3D object in a physical space
he does not need any 3D modeling skills.
In the next couple of slides I'm going to talk about
how we design a laptop stand
with our strut modeling techniques.
What the user does is he starts by connecting struts to hubs
and by building in the physical space
he can adjust the struts to fit
around the laptop in this case.
He can adjust the width, the height.
He can also build 3D geometries as you see it right there.
And he can test them during the design phase.
So once he's roughly satisfied with the model,
he can test the model next to an external monitor
and he can see for himself if the laptop stand
is at the right eye height
in comparison to the external monitor.
So he positions the laptop on top.
If it's not the case,
if the height or the angle is not right,
he can adjust the struts by turning
the thumb wheel on the strut.
Once he's satisfied with his model,
we have this virtual rendering environment
where our object is automatically tracked
and what he do, is he has different post processing steps.
In this case, we choose a reinforced wire frame model
of our strut model.
After this is done, he can export this as an SDL file
that's ready for 3D printing.
Once this model is 3D printed, he can
check the angle and the height that was already tested
in the design phase, and we have in this case,
an ergonomically sound laptop sound from the first 3D print.
So in short, strut modeling uses struts and hubs
to build a physical object.
The hubs are magnetic.
And the struts are actively communicating
to the central hub.
Users can adjust the struts length to model
around physical objects, so you can build in physical space
and use the struts to
do it just according to the physical models that you have.
Every strut is set to real time
and is being rendered in a virtual environment.
In contrast to other construction kits.
A lot of research has been done
in digitizing physical objects.
For example, what you can see here is Maker's Mark
uses clay to sculpt in 3D models
and then it's digitized by 3D scanning.
The downside of using clay is that it
requires a lot of crafting skills.
To resolve this, other researchers have explored
construction kits.
We have two general types of construction kits.
First, we have the struts and hubs.
And on the right side for you guys, we have the brick kits.
I'm gonna go into a little bit more detail.
The struts and hub kits,
like the work of Jacobsen, at your left,
and then the work of Weller with Spossy on your right,
uses struts that snap to mechanical hubs
and they make skeletons of their struts
and animate 3D figures in a virtual environment with this.
The benefit of this is that you can
animate them by hand.
The downside of using these struts is that
they have a fixed number of struts that can connect
to a central hub.
With our strut modeling technique,
we can connect an arbitrary
number of struts to a single hub,
because we use a magnetic hub.
The second type of construction kit are brick kits.
For example, on the left we have DuploTrack.
And on the right we have the work from Anderson et al.
Both of these kits have a Lego-like or Duplo-like brick kit.
They destruct and recreate
these bricks in a virtual environment.
When using these brick kits, for example,
if you want to model a rooftop, like you see on your left,
if you want to change the angle, you have to deconstruct
all the bricks to adjust the angle.
So, in general strut modeling
contributes a minimalistic kit,
consisting of only one strut and hub design.
This is (mumbles) puzzling, with many types of pieces,
often experienced in existing construction kits.
Now, how do we do this?
We have a central note that is connected
to a computer that runs a virtual environment
and then all struts are actively
communicating to the central hub
and the magnetic hubs are completely passive.
Our single struts exist out of base and an extension.
The base is here.
The base is 93 millimeters and extension is 77 millimeters.
We can extend the strut by turning the thumb wheel.
This is fast, speed up this video.
We can turn up, because we are a very fine picture
in our strut.
We measure this with a rotary encoder
at the back of our strut mechanism.
We count the pulses of every revolution
with this rotary encoder.
At the end of every strut, we have a metal connector
that attracts the magnetic ball,
so we can build physical models that provides
the mechanical strength.
And they also are used to detect adjacent struts.
I'm gonna talk about this more later in the slides.
What we've developed is a custom PCB
and it contains
a microcontroller
and the main parts for the tracking is done by
the IMU, the sixth access IMU.
Alright, every strut also is equipped
with a wireless communication module
that communicates with the central note.
Every strut is also equipped with a LiPo battery.
The LiPo battery powers the strut.
That is 130 million per hour powers battery.
We also developed a little battery management,
BCP to provide the necessary power to our strut.
This hardware implementation we will realize real time
relative position tracking of our struts.
This is done by combining relative orientation data
with topology information to get relative positioning.
First of all, we have the relative orientation.
We do this.
We calculate the relative orientation
with the sixth access IMU.
We combine the accelerometer data and the gyroscope data
and we continuously stream this data of every strut
to a central note.
Once we have this relative orientation,
we need the topology information.
And when we combine the topology information
and the relative orientation, we get
a relative positioning.
So to get this information, the system continuously goes
through the full length procedure.
Here we have a couple of struts, where the central note
sends a message to one of the struts and it tells it
to apply a voltage on one or the other side of its strut.
In this case, it applies it on the left side of the strut.
Once this voltage is applied,
it starts a signal,
it sends a signal
to all other struts to start reading
if they can find any signal on their magnetic hub.
Once they detected a signal,
that there's a voltage present at one or the other end
of each strut, it will report back to the central note.
Then the cycle repeats
and it will apply a voltage.
The central note says apply voltage on the right side
of your note
and the central note says start reading on all struts.
By doing this, we can build up our topology information.
This cycle repeats constantly.
We can scan the full topology information
from about 20 struts, I think, in less than a second.
When we combine the topology information
and relative orientation information of every strut,
we get the relative positioning.
And this is sent to the virtual environment
where the 3D model is rendered in time.
In this rendering environment, we can choose three different
post processing steps for the digital fabrication processes.
I'm gonna try to explain these post processing steps
with this cookie jar as an example.
We built this cookie jar with our strut modeling technique.
And once you build it, you have a virtual representation
that's on your left in the rendering environment.
The first option is to export it
as reinforced wire frame model.
The position of all struts are rendered as cylinders,
and are combined in the smooting operation.
This will result in a 3D model that can be exported
as an SDL file or after, you can 3D print it.
What if you want an enclosed 3D model?
We have a second option, we can do a convex whole operation
on the strut models.
Or we can take in the object
or export it as a single shell model for 3D printing.
The last option is,
in the last option we project the vertices
of the convex whole onto a 3D plane.
We can export this as an SVG file.
This then can be used for laser cutting or CNC milling.
So with this technology, novices can easily produce
a wide variety of artifacts.
To demonstrate these possibilities,
we produced a laptop stand, a cookie jar,
a photo stand, and some assistive tools.
Alternatively, strut modeling can also be used
to measure angles or lengths.
For example, to repair the top lid of this trash can,
we can measure the angle or length
that can be automatically applied
to a barometric model of the top lid.
So to conclude, in this paper we presented
a universal hubs and struts system
where arbitrary number of struts
can be connected to one hub
and where the length can be adjusted.
With strut modeling, the user can build object
in physical space without a need of 3D modeling skills.
And the users can build around existing objects
allowing them to adapt and test objects
in the design phase.
Once satisfied, the model can be exported and produced
by digital fabrication and printed out,
or a laser cut model can be immediately used
as it was already tested in the design phase.
Alright.
I wanna thank you for your attention.
And if there are any questions, you may ask them.
(clapping)
- [Si] Hey, great project.
I'm Si from Carnagie Mellon University.
One of the question I had was,
struts are typically used for resisting compression.
I mean, they are typically used in (mumbles)
and outter frames and so on,
I was wondering if you considered doing
any kind of compression testing
on your final fabricated object?
Or giving feedback to the user
as they're building these tresses?
- Yeah, so we didn't implement that
in our software or our hardware.
That's for sure a possibility to implement that
in the future, I think that is very useful.
- Alright, let's thank Denny
and all the other speakers in the session again.