bots IN BRIEF
SERVO 08.2015 13
WE BE JAMMIN’
Soft actuators are appealing for robotics because they’re cheap (made out of plastics or polymers and
air), inherently compliant, and relatively safe for humans to
interact with. Plus, they are able to adapt themselves to
grip a wide range of objects. Being soft is fine and dandy,
unless you need an actuator with some stiffness. So, what
do you do?
Well, researchers at Technische Universitat Berlin led
by Professor Oliver Brock have combined soft pneumatic
actuators with a jamming system that results in a variable-stiffness actuator that’s soft when you want or hard when
you want. They call it Pneuflex.
The researchers tested three different jamming
systems, including the traditional coffee grounds, as well as
two other designs based on scales and interleaved layers.
They eventually settled on the interleaved layers for the final design because it requires far less
pressure to jam — although it’s more complex to manufacture.
In principle, it works in a similar manner: When the interleaved layers have air between them,
they can slide against each other, allowing the actuator to flex. When the air is pumped out, the
layers compress against each other, and the actuator is stiffened. You can do this by hand with a
syringe, or using a pump or autonomous operation.
The three jamming systems tested included: granular jamming; layer jamming with overlapping
fish-scale-like layers; and layer jamming with stacks of interleaved layers.
Overall, the jammed actuator exhibited a stiffness increase of 8x, resulting in an application of
force increase of 2.3x — which is pretty significant.
Incidentally, you can make these actuators yourself for free. Instructions are available at
Photo: Evan Ackerman
GOOGLE’S DRIVING RECORD
Arecent report shed some light on the number of accidents Google's elf-driving cars have been involved in.
Google says its group of 20 autonomous cars have been involved in 11
accidents since hitting the roads in 2009. All the accidents — which were
minor and did not cause injury — were actually caused by humans driving
other cars. Google stated that none of the accidents were caused by its
Here’s a breakdown of the accidents:
• Seven accidents involved Google cars being rear-ended
• Two were side-swipes
• One accident involved a car rolling through a stop sign
• Eight of the accidents occurred on city streets