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Collision avoidance on the radar
Positioning system specialist Symeo has
successfully tested a collision avoidance
system at a major straddle carrier terminal
Collision avoidance is on the radar of
several terminal operators looking to
improve safety. Tracking equipment using
GPS to optimise travel paths and
record container moves is relatively
common, but Germany’s Symeo is now
working on a system that uses its Local
Position Radar (LPR) technology to
track equipment for the main purpose
of collision avoidance.
The system design goes beyond establishing
safety zones around equipment
and generating alerts when proximity
is breached. Symeo is focusing
on more comprehensive anti-collision
functionality that uses different sensors
and software-based rules to allow
equipment to operate in close proximity
at slow speeds without generating
unnecessary alarms, while at the same
time raising an alert when a real risk is
imminent.
Lessons from steel mills
Symeo has installed a collision avoidance
system in the hot slab storage area at a
steel mill operated by Voestalpine Stahl
GmbH. It covers cranes, straddle carriers
and other vehicles that operate in a
75,000 m 2 area.
The positioning system consists of
LPR transponders mounted around
the facility as reference points and LPR
radar units on vehicles and cranes. The
position information is used by a Collision
Warning System (CWS), a central
controller similar to the TCAS system
used for airplanes. Machines can determine
any potential collision risks locally
using data from its own position
and from the other equipment.
The vehicles transmit position, speed,
travel direction and their own shape
to other vehicles. The information is
used to calculate a dynamic safety zone
around each vehicle that controls the
warning signals. Drivers have a six-inch
display that shows their vehicle position
and surrounding obstacles and gives
visual and acoustic warnings when
there is a collision danger.
Symeo general manager Christoph
Rommel explained that the system
took some time to configure. It was
initially set up (according to the customer’s
specifications) to provide warnings
based on proximity alone, but this
proved too indiscriminate and generated
too many alarms.
Together with Voestalpine, Symeo
went back and developed specific
warning rules to allow two vehicles to
pass at low speed, and gantry cranes to
work in the same area in tandem without
generating alarms. It is only by taking
this approach, believes Rommel,
that a workable system can be designed
for a complicated environment with
lots of moving equipment like a container
terminal.
Container applications
For a container terminal, said Rommel,
a CWS needs intelligence to identify
parameters including speed and
direction of travel at the vehicle level
and report only those events that constitute
a risk to the central software.
It also needs to integrate information
from quay cranes including trolley
position, spreader height and portal
beam height.
Rather than set up alarms based
solely on proximity events, the system
designer needs to work methodically
through all the instances where equipment
comes into close proximity and
define rules around what is safe and
what is not.
A straddle carrier could, for example,
enter the proximity zone of a
crane spreader but not pose a risk if the
spreader is being hoisted.
All terminal traffic patterns have to
be analysed and every fixed obstacle,
including light towers and hatch covers,
must be identified and mapped. The
hardware and software also need to be
configured for different vehicle types,
such as three- and four-high straddle
carriers, that require different safety
rules.
Decentralised system
Symeo does not believe the best way to
design a system is to have a large fleet
of vehicles reporting position and status
constantly to a central application. The
CWS at the steel mill is designed with a
decentralised architecture. “Data is sent
to a server only for replay analysis of
near misses – all collision avoidance decisions
are made locally on the vehicles
and cranes; this minimises the amount
of data that needs to be sent from
equipment to the central software,” said
Rommel.
Each vehicle has a collision zone and
a defined proximity radius. An onboard
collision calculator monitors for obstacles
in the proximity radius, but ignores
other equipment unless their proximity
radii overlap. When that occurs, position
information is sent to the CWS
software on the local machine, which
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triggers an alarm if the operational
rules are breached.
All communication is via triple redundant
ZigBee at 2.4GHz using the
Symeo data protocol. This means, explained
Rommel, that there are no
interference issues with the terminal’s
WiFi network. The system has now
been successfully tested at a container
terminal, it fulfils the customer’s requirements
and implementation is
planned for 2014, said Rommel.
The LPR system can also be leveraged
to provide container position information
and vehicle telematics if required.
GPS has been preferred for this application,
to date, particularly for straddle
carriers, but Rommel believes this
will change. Terminal operators want
one PDS technology that can work
Symeo has installed its system in a German
steel mill and is looking to apply the technology
to container terminals
across the whole terminal, and GPS systems
continually struggle because they
lose signal underneath the quay cranes,
he added.
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