Hi and welcome to my presentation on
Omni.
We present a method for volumetric
sensing and actuation of passive
magnets
especially for haptic feedback systems.
Virtual and augmented reality are
gaining more momentum due to their
promise for immersive experiences.
However, to increase the immersion into a
carefully crafted
artificial world it's necessary to
also support the sense of touch.
A lot of prior work exists on this
ranging from complex mechanical designs
to fibro tactile stimuli to larger
electromagnetic surfaces.
The main challenge of closely related
work such as NormalTouch
by Benko and colleagues and butterfly
haptics by Berkelman and colleagues
is that they require external tracking
or are desk-sized.
This gives rise to the question how we
can leverage electromagnetism
to simultaneously exert haptic feedback
as well as track
an input device. To this end we have
three contributions in our paper.
First of all, we have a hardware
contribution. Secondly,
we suggest a method of position
reconstruction, and finally,
we activate at the same time.
Lt's first discuss the hardware. Our
system consists of a permanent magnet
embedded in a tool. The main actuator
consists
of a spherical electromagnet, this is
constructed around an iron core
and consists out of three orthogonal
coils.
Below that is a PCB with eight three
axis hall sensors,
which enable tracking. The whole system
is cooled by a single fan. Now that you
have an overview of the hardware
let's dive into details on the tracking.
To understand our method let's starts with
the inputs. The first step
is to measure a hall sensor, this
provides you with a magnetic field
at a certain location. This magnetic
field
is influenced by a permanent magnet in a
tool.
However, it is possible to approximate
this influence with a dipole-dipole
model
denoted in blue. This influence
depends on the pen position relatively
to the sensor.
We can use a similar model to
approximate the influence
of the spherical electromagnet. So, now
our hall sensor measures the tool,
the actuator, and noise. The measurement
can be approximated by the sum of the
models; since the magnetic field
forms a superposition. By minimizing the
squared difference between our model and
a measurement
you can estimate the pen position p.
Which is a solution to this problem.
Here you can see the tracking as
observed through a mixed reality headset.
Since the method uses gradient descent
under real-time optimization
it takes approximately 50 milliseconds
to converge.
We now have an actuator that can track
our tool, but how do you actually provide
force.
The force in three directions can be
changed by altering the current,
thereby delivering forces that are
perceived in different directions
and strengths. During experiments we have
measured forces up to 2 newtons for 30
seconds,
lower forces can be sustained
indefinitely. This is enough to launch
the pen or lift an apple.
With ferromagnetic fluid we showed that
you can change the direction of the
magnetic field.
And here we use a permanent magnet found
in our tool
to illustrate that you can supply both
the tangential as
well as radial forces.
Let's take a look at how accurate we can
track.
For this we use the 10 camera optitrack
we measured the tracking with and
without activation.
Without actuating we found that we had a
tracking error of 4.9 millimeters
in euclidean distance. This increases to
6.9 millimeters
with actuation. However, overall
the error per axis stays well below 5
millimeters.
Let's see what kind of use cases our
system enables.
Here a designer is extruding material
from a shape.
An attractive force is felt during
extrusion.
Our system can also be used to explore
non-rigid bodies.
Here an tangential force is felt
whenever the dragon is touched.
Finally, it can be used in gaming. Here in
a joystick like fashion.
a heavy attractive force is felt when
the user bumps into the wall.
To summarize we made three distinct
contributions in our paper.
We have introduced new hardware, a tracking
algorithm,
and actuation at the same time. Omni's
capabilities allow spatial interactions
systems to integrate 3D tracking and
activation of untethered free-range
tools
simply by embedding a small permanent
magnet.
Thank you.