Hello, I’m Humphrey Yang from Carnegie Mellon.
I’m here to talk about ReCompFig
a method for designing reconfigurable kinematic devices
using compliant mechanisms and tensioning cables.
In this work, we are using
compliant mechanisms to create mechanically simple structures
that are easy to design and make
and add tensioning cables to adjust
a device’s kinematic affordances in real time.
Compliant mechanisms afford kinematics through structural deformation
thus eliminating the need for moving parts
like hinges and joints to simplify the design.
They are typically made of two types of elements.
One is rigid stages. They are undeformable solid blocks
that does not affect the device’s kinematics
but they can take any shape to provide different functions.
The other is flexures, in this case rods
that have a slender aspect ratio
that makes them quite easy to deform in certain ways.
The flexures will bend to allow motion
and the enabled motion depends on the rods’ layout.
But compliant mechanisms are still not reconfigurable.
That’s why we’re adding cables as an additional element.
Cables are identical to the rods
but have an even more extreme aspect ratio.
So when we loosen the cables, the device will become free to move.
And when we tighten the cables using, say, motors
device becomes immobile.
This allows us to change its kinematics on the fly.
So, taking advantage of this feature,
we can design a multimodal kinematic device
by first creating a compliant mechanism
that enables all kinematic freedoms we want,
and with multiple groups of cables,
we can selectively tighten or loosen them
to disable the undesired kinematic freedoms
while keeping the ones we want.
This way, the device will be able to provide
distinct kinematic affordances for different situations.
We also add stretchable sensors to allow detecting interactions.
The sensor’s stretchability provides no kinematic constraints
but their resistivity changes when stretched
so we can use it to detect how the device is being deformed and interacted.
We provide a design tool to support users
create the desired functions, modes, and devices.
These devices can be easily fabricated
using a desktop 3D printer and an Arduino controller.
We used the design tool to create several application demos.
This video shows a multimodal input device.
In one mode, the device is free to translate
along a single direction to simulate a slider.
The signals were used to adjust the color of the background screen.
When we adjust the cables, the slider now becomes a twisting knob
that we can use to control a dial on screen.
The reconfiguration takes no more than half a second.
Finally, the device can be configured into a joystick
to control objects on screen.
A device like this can change its functions
depending on the interaction context
thus making physical input devices more versatile and adaptive.
Compliant mechanisms are also miniaturizable.
We leverage this feature to create tangible pixels
and arrange them in an array to form a kinematic display.
Depending on how the cables are tightened and loosened
the pixels may provide the affordance of different surfaces.
If the cables are loosened, the pixels are quite deformable
simulating the hand feel of touching a soft, deformable surface like mud.
Yet, when we tighten the cables
the pixels becomes rather rigid and undeformable
creating the sensation of rigid surfaces
like dried earth when you touch them.
We also design a haptic proxy using our method.
In this case, the device can be worn on a user’s hand
and depending on how the cables are configured
the weight attached to the device may shift in different ways
to provide the hand feel of holding different objects.
When both cable pairs are loosened, the weight is free to move
when the user shakes their hand, thus feels like holding a cup of water.
When one cable pair is tightened, the weight is free to move in one direction but not the other
thus simulating the hand feel of a thin object, like a ruler.
Finally, when both cable pairs are tightened, the weight is no longer mobile
and the hand feel will become stiff and firm
simulating that of an aluminum bar.
There’s also an opportunity to connect the device with
artificial reality contents to provide on-demand tangible feedback
like changing the hand feel depending on
what a player is holding in a VR game.