Hi, my name is Robert Kovacs from Hasso Plattner Institute, and this time I’m presenting Trusscillator, on behalf of all my co-authors.
In this short teaser, two designers are using Trusscilaltor to create a somewhat uncommon-looking playground swing.
As you can see, the key design element here is a SPRING.
Trusscillator allows designers to tune the dynamic behavior of the swing
and also helps to physically build the device from welded steel.
But let's start from the beginning...
In my research agenda, I have been focusing on the question of how to create large-scale objects.
Starting from static structures, such as the pavilion that we built using TrussFab.
and more recently, in TrussFormer, we have been creating mechanisms that produce a specific movement path, such as this animatronic t_rex.
Based on this, I was now wondering how to make machines that could be operated by human power?
Because, if we look more closely, Trussformer is powered by a 2000W compressor,
that is comparable to the power of 15 grown-ups...
Pretty much on par with the related work by Coros et al., that generates mesmerizing mechanisms,
but also uses a surprisingly large motor to power even smaller installations.
If we look closer at the cheetah's anatomy, we see that there are elastic tendons connecting the muscles to the bones.
These tendons serve as mechanical energy storing devices, or SPRINGS.
This enables the cheetah to recycle large part of the energy during the motion, therefore to run extremely efficiently.
With Trusscillator our objective was to create, human-scale human-powered machines, such as the playgroup equipment I showed you earlier.
However, it quickly became clear to us that the kinematic approach won't be sufficient, but we need to take the energy into account.
Trusscillator assists this process in three aspects:
Let me quickly walk you through Trusscillator’s workflow.
These two designers were tasked to design a swing for a dinosaur-themed exhibition.
They start their design by creating the shape which will be made of welded steel truss.
After they are satisfied with the rough shape, they enable motion by exchanging certain edges with coil springs.
Trusscillator highlights when a moving part was created.
After defining the kinematic function they indicate the child’s seating position.
Trusscillator responds by running its simulation engine and returns this three-layer curved path above the user’s head, indicating the amplitude of the movement.
They replay the animation by clicking on this motion path.
They are concerned that the dinosaur head would reach down far enough to hit someone,
so they decide to reduce the amplitude by grabbing the handle attached to the motion bar and drag it inwards.
Trusscillator, in turn, runs its optimization engine and returns a stiffer set of springs.
Our designers are now satisfied with the new amplitude, however, they find the motion might be too fast, as the tempo widget also indicates.
They cycle through to the three offered options to make the ride more comfortable.
As a result, Trusscillator just added an additional weight to the top of the head in order to lower the eigenfrequency of the device.
Happy with the new tempo, now they sadly notice that the effort widget turned to hard,
meaning that it might take too long to set the device in full swing, and children might lose interest.
This time our designers decide to add twist to the mechanism by adding a second seat for another child.
This, as a result, reduces the effort to swing, and they’ll be also challenged by having to synchronize their motion in order to hit resonance.
Finally, the designers happy with the results, hit the fabricate button and head over to the workshop.
Let me explain now how Trusscillator assists the fabrication process.
As you see here, Trusscillator generates a set of custom stencils that are produced using a laser cutter.
These stencils are used to mark the incidence points on the node spheres where the tubes will connect.
To hold the structure in place for welding, we have designed these temporary connector pieces.
They hook into the holes, while their other side acts as a strong cantilever spring that sticks into the tubes holding them together firmly for welding.
This is all in a nutshell what Trusscillator enables us to do, but let me also briefly explain how the computation is happening in the background.
So, just to recap, let’s look at this simple bobbing rider as an example.
The user only interacts with the high-level experience attributes, the amplitude, tempo, and effort.
While, Trusscillator tunes mechanical properties, the mass of the device, the spring stiffness, while the damping remains constant.
The model is being created using Trusscillator’s Sketchup plugin.
This model is then being transferred a JSON file to Trusscillator’s simulation server.
The server translates the model into a system of differential equations and solves them with a range of parameters in parallel worker processes.
When a suitable spring configuration is found, the server returns the simulated sequence to our frontend.
To find the best combination of springs and masses, Trusscillator samples the nonlinear parameter space by first varying the stiffness of the springs.
After finding the approximate spring constant, it runs another batch of simulations, now varying the mass of the device to optimize the eigenfrequency.
It repeats this process for every spring in the mechanism and returns the best matching solution to the front end.
This process is repeating every time in the background whenever the user changes any of the high-level motion attributes, for example, the amplitude.
To validate if our simulation is returning realistic results, we have mounted three accelerometers onto our physically built dinosaur swing prototype.
We recorded the frequency response the structure was giving to a push and pull impulse.
We have plotted the results in the frequency domain.
The green line here represents the measured data, while the orange line indicates the simulated results.
We can see that the simulation is resembling the measurements closely, therefore we can exclude systematic errors in our simulation.
This workflow enabled us designing a series of spring-based equipment, not only for playgrounds but also sports equipment, or artistic installations with dynamic movement.
To conclude this talk, I’d like to show the path how we arrived to this research project and where could it potentially lead.
I just told you about Trusscillator…
a system that considers forces and motion
this is the last out of the four projects of my PhD on large scale fabrication
...which started with Protopiper: a device that allowed users to create large-scale mockups
Then, with Trussfab we included forces to the equation to allow users to build not only large but also load-bearing structures,
such as the pavilion, that you might have seen at CHI
Then I switched to exploring movement. TrussFormer supported users in build large kinetic structures.
—but at the expense of the aforementioned ginormous compressor...
And now Trusscilator, brings it all together in a system that allows building devices that consider motion and forces at the same time.
All in all, I think about this line of work as “democratizing engineering” by embedding domain knowledge into software systems
that enable building larger objects than pure intuition would naturally allow for.
Thank you for your attention and happy to take your questions.