ELECTRONICS CONEXPO
WANDFLUH
82
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iVTInternational.com February 2020
MARCH 10-14, 2020
LAS VEGAS
South Hall 3 – S80259
A NEW GENERATION OF CONTROL DEVICES ALLOWS ELECTRONIC
MODULES TO EASILY COMMUNICATE
For large and complex machines, a higher-level
PLC often coordinates the processes and controls
the respective assemblies. Hydraulic functions, such as
the position control of a hydraulic axis or the pressure
control of a holding, clamping or pressing function, are
also regulated by the PLC by controlling the
corresponding electronic cards.
The requirements for mobile machines are usually
somewhat more complex. The individual electronic
boxes not only control the valves but also perform
coordination, measurement and control tasks within the
overall system. Thus, a large-scale project usually results
in smaller sub-projects that are delimited by clearly
defined communication and sensor interfaces. This
requires a rethinking of the design of a mobile machine
and needs close cooperation between system, hydraulic
and electronic engineering.
The solution
The latest generation of Wandfluh control devices
simplifies this interaction by allowing modular, freely
programmable electronic modules to communicate with
each other via a CAN bus interface and perform their
tasks exactly where they are needed.
These PME electronic modules are extremely widely
applicable due to their variety. The range includes amplifier
and control modules in different sizes, operating elements
and freely programmable graphic displays on which
selected machine data can be displayed in different views.
Besides flexible programming, a major advantage is
the extensibility of such modular structures. In addition,
the devices are equipped with a telemetry interface that
allows remote access via GSM or Wifi to remotely control
the machines, perform remote diagnostics or ensure
worldwide GPS tracking of the vehicle.
Testing the concept
As a first prototype, Wandfluh realised a PME control
system on a trailer for forestry operations in 2016 in
order to be able to test the concept and technology in
an impassable environment and under the influence of
snow, rain and vibrations. The trailer is controlled from
the towing vehicle via a single cable and has a hydraulic
drive support as well as a hydraulic brake. This allows
safe manoeuvring with a relatively small towing vehicle
in narrow and sometimes steep forest areas without the
risk of getting stuck.
In addition, the hydraulic brake can cope with long
and steep descents without overheating the brakes of
RIGHT: Online
diagnosis via Wandfluh
PME device
BOTTOM LEFT:
Electronically controlled
hydraulic drive and brake
support
BOTTOM RIGHT right:
Built-in solenoid spool
valves WDMFA
the towing vehicle, as the engine brake cannot hold the
weight of a fully loaded trailer alone.
In practice
The decentralised input/output modules for the sensors
and electronic cards of the hydraulic valves have been
connected via a CAN bus. The proportional pressure relief
valves that regulate the additional force of the trailer are
set on a display in the towing vehicle. The cardan shaft of
the towing vehicle drives two independent hydraulic
pumps that provide the necessary oil pressure for the
drive support uphill. Downhill, the axles of the trailer are
hydraulically braked by the same valves indirectly
limiting the speed of the axles.
A large part of the braking energy is converted into
heat that heats the hydraulic oil. This energy is released
into the ambient air with a conventional fan. The
separate control of the right and left axle allows the
simulation of a differential lock that can be very easily
unlocked at higher speeds on solid ground by opening
the valves. The additional sensors on the cardan shaft
and on the gears enable software-supported monitoring
of the system and also pass on important information to
the driver while the vehicle is in motion.
Other machines
Similar solutions can be found in construction
machinery, special machinery or, for example, in straddle
carriers (large container lifting trucks in the port area)
whose eight axles can be controlled synchronously at
high speeds and switched to asynchronous control for
manoeuvring in the tightest of spaces. They usually
travel around the port without a driver, receive orders
from an operator and carry them out independently. iVT
Author: Adrian Feuz, head of electronics, Wandfluh AG
Modern hydraulics in
digital networks
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/iVTInternational.com