IEEE Robotics & Automation Magazine - September 2021 - 51

human operators even if it may cause high workloads [6]
and adopting automated solutions. Finally, e-commerce
has impacted both business-to-consumer (B2C) and business-to-business
(B2B) markets. The market size of B2B
e-commerce is more than 10 times that of B2C [7], allowing
businesses to present an unprecedented variety of
products to customers. This has brought undeniable
advantages in terms of sales [7], but it has also increased
the flexibility requirements with which the intralogistics
system must comply.
Order picking-the process of retrieving products from
storage (or buffer areas) in response to a specific customer
request-is responsible for 50-75% of the total cost for a
conventional warehouse [8]. Hence, order picking is considered
one of the highest priority areas for improvement to
maximize warehouse productivity. However, despite the
crucial importance of picking operations, warehouses still
mostly rely on human workers [9].
The major challenge preventing the full automation of
picking is represented by the high variability among
objects to be handled in terms of, e.g., their shapes or
object configurations and the presence of inaccessible or
even absent surfaces and also of flexible or pierced surfaces.
Regarding object shapes, cuboids constitute the vast
majority of items stored in warehouses [10]. According to
[11], among shipped packages, the shapes that occur most
often are cuboids and, in a lower percentage, cylinders.
Thus, strategies to manipulate cuboids and cylinders in different
configurations account for a considerably large part
of the intralogistics processes for handling goods.
Several components contribute to the realization of a
flexible picking solution:
●
a robot design able to execute the picking operations in a
warehouse environment physically
● a vision system able to detect objects and constraints
●
●
a perception system able to identify desired and undesired
contacts
a planning method able to generate a trajectory accomplishing
the task while satisfying the constraints and
adapt that trajectory based on the perception outcomes
● a control strategy able to track the desired trajectory.
The present article focuses on the realization of a flexible,
autonomous picking solution, leaving for the future integration
with the vision system.
Some of the most challenging and common situations
an autonomous pick-and-place system might encounter
include
●
●
a restricted portion of the external surface of the object
being available for gripper contact due to other goods,
especially when they are tightly packed together
●
●
deformability of the object, meaning that the shape of
the grasped object changes under external forces
porosity of the object, which prevents the employment of
simple and nimble suction grippers.
Figure 1. The WRAPP-up: a dual-arm robot composed of two
anthropomorphic 7-DoF manipulators, a Pisa/IIT SoftHand, and
a velvet tray. WRAPP-up is illustrated picking a box that does not
have a top surface.
SEPTEMBER 2021 * IEEE ROBOTICS & AUTOMATION MAGAZINE *
51
reduced, collision-free end-effector poses due to other
goods or containers
Despite great effort in the development of picking solutions,
as far as we know, no currently existing automatic
solution is flexible enough to cope with such challenges,
many of which may occur simultaneously.
The main contributions of this article are the design,
realization, and testing of WRAPP-up, a novel humaninspired
dual-arm robot for intralogistics. The development
of WRAPP-up relied
upon observing the techniques
adopted by human
pickers at work in warehouses.
Indeed, by observing
expert operators, we identified
four main maneuvers
they commonly adopt; these
are detailed in the section
" Human Picking Skills. "
Based on these findings,
we designed a dual-arm
robot (see the section " The
WRAPP-up Design " for more details) composed of two
7-degrees of freedom (7-DoF) manipulators and two different
end effectors: a) an adaptive end effector able to both
grasp a large variety of objects and stably interact with different
shapes and b) a tray with an actuated belt. Moreover,
Order picking is considered
one of the highest priority
areas for improvement
to maximize warehouse
productivity.
IEEE Robotics & Automation Magazine - September 2021

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