Safety solutions for intelligent human-robot collaboration

Safety
solutions for intelligent human-robot collaboration

Human-robot collaboration
(HRC) describes an environment where humans and automated machines share and
work in the same workspace at the same time. Driven by Industry 4.0, this model
of collaboration promises highly flexible workflows, economic efficiency, maximum
system throughput and productivity. However, ensuring that HRC is actually able to live up to this promise
requires precise safety technology for the application in question
.

One
of the major issues associated with Industry 4.0 is making work processes
flexible and safe. For example, manufacturing products in batch size 1 under industrial mass-production conditions involves
manufacturing unique items on one conveyor
belt. In this type of smart factory, where products and production processes
are one with state-of-the-art information and communication technology, requires
machines that are increasingly intelligent, and as a result increasingly
autonomous. In addition to this, the interaction
between humans and machines is also set to increase in industrial
manufacturing. This is because combining
the abilities of humans with those of robots results in production solutions that
are characterised by optimised work cycles, improved quality, and greater
cost-efficiency. At the same time, machines that are autonomous but primarily
interact with humans require new safety concepts that provide effective support
for making production processes more flexible.

Human-robot interaction: a question of space and time

Industry 4.0 is not the first
time that industrial automation has focused on interaction
between humans and machines. To date, two interaction processes of coexistence
and cooperation have dominated, accounting for around 90 percent of cases.
Space and time are crucial interaction parameters in these processes.
Coexistence describes cases in which humans and machines stay in neighbouring
areas at the same time while they interact. A typical example of this is an
insertion station with a rotating table on a robot cell. Humans and machines
work in neighbouring workspaces at the same time, with the area between the two
being monitored by a deTec4 Prime safety light curtain, for example.
Cooperation, on the other hand, is when humans and machines work in a shared
workspace but at different times. An example of this type of work situation is
a transfer station for assembly robots. A worker inserts a work-piece and, at
the same time, a S3000 safety laser
scanner with multiple simultaneous protective fields that detect the worker
ensures that the robot speed is reduced
or that the robot is brought to a
safety-monitored stop.

Industry 4.0 is seeing a third
form of interactions shifting increasingly into the spotlight: this process is known as collaboration. This involves both humans and robots sharing
the same workspace at the same time. An example of this is a mobile platform
with a robot that takes parts from a belt or a pallet and transports them to a
workspace, where they are presented and given to the worker stationed there. In
collaborative scenarios such as this, the conventional safe detection solutions
used for coexistence or cooperation are no longer sufficient. As the forces,
speeds, and travel paths of robots now need be to monitored, restricted, and
stopped where necessary, depending on the actual level of danger. The distance
between humans and robots is, therefore, becoming a key safety-relevant parameter.

The risk assessment is always the first step – even for “cobots”

No two examples of human-robot
collaboration are the same. This means
that an individual risk assessment for the HRC application is required even if
the robot concerned has been developed specifically to interact with humans.
“Cobots” like this, therefore, have many
features of inherently safe construction,
starting from their basic design. At the same time, the collaboration space
also has to meet fundamental requirements such as minimum distances to adjacent
areas with crushing or pinching hazards. General standards such as IEC 61508,
IEC 62061, and ISO 13849-1/-2 are one way in which the foundations for the
functional safety of HRC applications are laid.
It is also important to give particular consideration to ISO 10218-1/-2, which
concerns the safety of industrial robots, and ISO TS 15066, which relates to
robots for collaborative operation. Developers and integrators of robot systems
not only have to perform thorough checks on the structural safety measures
taken by robot manufacturers, with regard to
their functions and compliance with the aforementioned
standards. They are also required
to consider any hazards or risks that may remain. This means carrying out a risk assessment in accordance with EN ISO 12100 for the robot system, its motion
sequences, and its planned collaboration area in
order to determine which safety measures are appropriate – such as
implementing suitable types of collaboration as defined in ISO/TS 15066.

Safety-related operating modes of collaborative robot systems

These technical specifications
can be used to discern four types of collaborative operation. The
“safety-related monitored stop” prevents robots from interacting with humans,
while “hand guiding” ensures safe HRC by guiding the robot manually at an
appropriately reduced speed. The third type of collaboration, “power and force
limiting”, achieves the required safety by reducing the power, force, and speed
of the robot – through safety controller limiting functions. For example, to a biomechanical load capacity
at which no hazards or injuries are to be
expected. This takes place regardless
of whether there is unintentional or intentional physical contact between
robots and humans.

The “speed and separation
monitoring” type of collaboration is completely in keeping with the concept of
highly flexible work environments – and therefore with the principles of
Industry 4.0 and production processes in smart factories. It is based on the
speed and travel paths of the robot being monitoring and adjusted according to
the working speed of the operator in the protected collaboration area. Safety distances
are permanently monitored,and the robot
is slowed down, stopped, or diverted when necessary. If the distance between
the operator and the machine becomes greater than the minimum distance again,
the robot system can continue moving at typical speeds and along typical travel
paths automatically. This immediately
restores robot productivity.

Functional safety for HRC: expertise, portfolio, and implementation from
a single source

Of the different types of ISO/TS
15066 collaboration, speed and distance monitoring in HRC applications offer the greatest potential as we move into
the future. When considered in relation to
these, and given the interaction processes
of coexistence and cooperation that have dominated up to this point, it is
clear that safety-related sensor and control technology is facing new
challenges to ensure that HRC can
continue operating unimpeded. It is also worth noting that the more the
requirements imposed on the safety of shared workspaces increase, the more
collaborative future work situations will become. As a manufacturer of sensor, control, and system solutions for
functional safety and a supplier of comprehensive safety services that range
from risk assessment and safety concepts through to system solution
implementation, SICK has extensive expertise in designing safe robot
applications. What’s more, SICK offers a range of sensors and controllers that
has developed along with the requirements of safe robot applications over the
decades. Safety solutions based on various technologies are becoming more and
more intelligent and are constantly making new HRC applications possible
because they canfulfil requirements that
are becoming increasingly
demanding.

As things stand, HRC only
accounts for a small share of all applications involving human-robot
interaction. Innovative solutions for functional safety in robot applications,
like those developed and implemented at SICK, can help to increase this share
significantly in the foreseeable future.

Written by: Fanny Platbrood, Product Manager for
Industrial Safety Systems, SICK AG, Waldkirch

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