Tech Briefs Magazine - June 2021 - MD-18

that are driven by a neural response
from the spine rather than the brain.
The team was inspired by neural circuits
found in animals, called central pattern
generators, made of very simple elements
that can generate rhythmic patterns
to control motions like walking
and running. To mimic the generators'
functions, the team built a system of
valves that act as oscillators, controlling
the order in which pressurized air enters
air-powered muscles in the robot's four
limbs. The researchers built a component
that coordinates the robot's gait by
delaying the injection of air into the
robot's legs. The robot's gait was
inspired by sideneck turtles.
The robot is also equipped with simple
mechanical sensors - little soft bubbles
filled with fluid placed at the end of
booms protruding from the robot's
body. When the bubbles are depressed,
the fluid flips a valve in the robot that
causes it to reverse direction. The robot
is equipped with three valves acting as
inverters that cause a high-pressure state
to spread around the air-powered circuit,
with a delay at each inverter.
Each of the robot's four legs has three
degrees of freedom powered by three
muscles. The legs are angled downward at
45 degrees and composed of three parallel,
connected pneumatic cylindrical
chambers with bellows. When a chamber
is pressurized, the limb bends in the
opposite direction. As a result, the three
The robot's walking process is driven by a series of valves.
chambers of each limb provide multi-axis
bending required for walking. The re -
searchers paired chambers from each leg
diagonally across from one another, simplifying
the control problem.
A soft valve switches the direction of
rotation of the limbs between counterclockwise
and clockwise. That valve acts as
what's known as a latching double pole,
double throw switch - a switch with two
inputs and four outputs, so each input
has two corresponding outputs it is connected
to. That mechanism is a little like
taking two nerves and swapping their
connections in the brain.
The researchers want to improve the
robot's gait so it can walk on natural terrain
and uneven surfaces, allowing it to
navigate over a variety of obstacles. This
would require a more sophisticated network
of sensors and a more complex
pneumatic system. The team will also look
at how the technology could be used to
create robots that are in part controlled
by pneumatic circuits for some functions
such as walking, while traditional electronic
circuits handle higher functions.
For more information, contact Ioana
Patringenaru at ipatrin@ucsd.edu; 858-8220899.
Soft
Tactile Sensor with Skin-Comparable
Characteristics for Robots
The design could contribute to various applications in the robotics field such as smart
prosthetics and human-robot interaction.
City University of Hong Kong
Aresearch team developed a soft tactile
sensor with skin-comparable characteristics.
A robotic gripper with the sensor
mounted at the fingertip could accomplish
challenging tasks such as stably grasping
fragile objects and threading a needle.
A main characteristic of human skin is
its ability to sense shear force - the force
that makes two objects slip or slide over
each other when coming into contact. By
sensing the magnitude, direction, and
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ToC
the subtle change of shear force, human
skin can act as feedback and allow us to
adjust how to hold an object stably with
our hands and fingers or how tightly we
should grasp it.
To mimic this feature of human skin,
the soft tactile sensor is integrated into a
multi-layered structure like human skin
and includes a flexible and specially
magnetized film of about 0.5 mm thin as
the top layer. When an external force is
exerted on it, it can detect the change of
the magnetic field due to the film's de -
formation. More importantly, it can de -
couple or decompose the external force
automatically into two components: normal
force (the force applied perpendicularly
to the object) and shear force,
providing the accurate measurement of
these two forces, respectively.
Moreover, the sensor possesses another
human skin-like characteristic: the tacMotion
Design, June 2021
http://www.abpi.net/ntbpdfclicks/l.php?202106TBNAV
Tech Briefs Magazine - June 2021

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