Thank you for coming to our presentation. We present a computational approach to haptic
design embedded in everyday tangible interaction with digital fabrication.
Our motivation is to achieve haptic design using magnetic forces embedded in tangible interaction.
We can imagine that the magnetic force can perform a simple and robust mechanism
for haptics when embedded in tangible objects.
We call this mechanism Magneto-Haptics. There are several advantages
when utilizing it with digital fabrication, such as compactness and non-abrasion.
However, it is difficult to manually design how magnets should be embedded in the objects.
Because the relationship between the magnetic force
and arrangement of the magnet is non-intuitive.
In our previous work, Magneto-Haptics, we established the forward design of this problem
by simulating the magnetic force from the complicated magnet arrangement.
However, it is extremely difficult to create a desired magnetic force feedback with this forward
approach, since we don't know what is the best magnet arrangement to achieve the desired haptics.
In our study, we solved the inverse design of this problem.
The optimization process contributes to finding the best magnet arrangement
to fulfill the curve of haptic potential.
In the following, we show some optimization sequences with the visualization.
We prepared three models of tangible interface and six different curves to
create six types of haptic feedback. After getting the best arrangement,
we created an actual tangible interface by the 3D printer to verify the result.
Now, we describe the technical part of this study.
Again, in this paper, we propose a computational approach to haptic design using magnets.
We solve an inverse design problem to search for an optimal magnet arrangement
that replicates the user-specified haptics. The process is divided into four sections.
First, we have to prepare four input data. The curve is the haptic sensation of the
moving container, which can be input by hand or line shape tool.
Here, the Y-axis is the haptic potential, H (t), that we originally defined for this study.
We also have to set the geometry of containers,
the trajectory of the moving container, and the geometry of magnets for each container.
Here, the number of containers is limited up to two in our model.
Let's move next.
In the magnetic simulator, we have three contributions.
The first one is the formal definition of Haptic potential.
This is defined as the potential field of the magnetic force distributed on the trajectory.
Also, we re-defined them with formal discussion in physics, assuming that the motion occurs
in a quasi-static manner. Those perspective were not
provided in the previous work. Please check them on the paper.
Second, we improved the magnetic simulator to reduce the computation time.
It was necessary for iterative calculation in the optimization process.
We applied adaptive meshing to the Taylor expansion of magnetic force calculation.
And, we also applied interpolation on the magnetic force for the accurate result.
Next, we formulated an optimization problem to optimize the parameter of magnets.
The objective is to minimize the distance between the user-specified
haptics and the simulated haptics. The search parameter is 6N dimensional,
where N is the number of magnets. This is because each magnet has the 3D position
and 3D rotation as the degrees of freedom. When performing the optimization, our method
considers two additional constraints to ensure that the found solution is valid.
This is handled by the penalty method, and see the paper for detail.
Finally, as the result, we got the optimal magnet arrangement which is estimated to
fulfill the haptic potential curve. In the video material, you can find
whole videos of optimization and visualization for six applications.
In conclusion, we proposed a computational approach to haptic design using magnets.
As Discussions, frictions are a limitation but we think it is possible to utilize
them for haptic feedback. Please find discussions on
the accuracy and limitation of the solvers. As Future works, we are going to design all
haptics by the magnetic force, and focus on the magnetic mechanism for tangible interaction.
It is the end of our presentation. Thank you for listening.