Control & Automation
RS Components brings
the Internet of Things to
automation and control
RS Components (RS) is a worldleading distributor of automation and
process control (A&C) components
from market-leading brands including
Siemens, Phoenix Contact, Honeywell,
Mitsubishi Electric Automation
Systems, Omron and Schneider
Electric among many others. The
company’s extremely wide A&C
portfolio ranges from control gear to
sensors, contactors to pneumatics,
and PLCs to motor controllers, as well
as an extensive selection of machine
guarding equipment to make working
environments safer. Now, RS is
expanding its automation and control
offering with innovative new products
that will enable the remote monitoring
and control of machines to meet the
growing needs of managing industrial
applications in the fast emerging
paradigm that is the ‘Internet of
Things’ (IoT), which is connecting
literally billions of devices to the
Internet in countless applications.
A core component in the IoT is
advanced connectivity technologies,
especially Ethernet but also wireless for
many new services and applications.
The IoT can offer significant benefits
for manufacturing companies such as
lowering costs, boosting productivity
and streamlining system complexity. A
new breed of increasingly standardized
Internet-based network architectures
are making it possible to connect up
plants or factory floors to the smart
processing capabilities of enterprise
computing via Industrial Ethernet and
many different wireless networking
solutions.
But key to the industrialization of the
IoT is the ability to deliver industryhardened products that are robust and
reliable and guaranteed to handle high
signal speed and quality. For example,
RS has a wide range of robust sensors
for remote monitoring and wirelesscapable devices that cover multiple
protocols, such as wireless LAN
Ethernet port adaptors and access
points, which open up conventional
A&C networks to wireless capabilities
including cellular technologies.
RS has the portfolio and the expertise
to make the Internet of Things really
work for A&C companies of all sizes.
uk.rs-online.com
Positioning control:
Not where you
should be? Torsion
and elasticity could
be to blame.
w
hen we think of a gearhead,
we tend to assume that it
is incompressible and rigid,
the truth is it still bends,
compresses and has elastic properties.
This has an effect on the difference
between the perceived motion (encoder
counts) and the actual motion of a
drive system –we are not where we are
supposed to be!
torsion. This is the actual elements of
the mechanical system twisting under
load. The more the gearhead is loaded
the more it twists, the more it twists the
more energy stored and the larger the
displacement error.
When measuring anything we need to
keep in mind how the instrumentation
works and what are its limitations, to
interpret the data we receive from it
correctly and in the right context. An
encoder will change its output status as
the shaft rotates at that measured point.
Should the drive chain twist under load,
the end with the encoder (normally on
the back of the motor) may be static
in comparison to the actual motion
occurring at the end of the gearbox.
This is usually accounted for by play or
“backlash” in the system, but there is a
more hidden element; the drive chain
The drive chain torsion begins with the
motor shaft twisting, then the gearhead
twisting and so forth through the drive
chain. Normally the twist of the motor
shaft is considered negligible as loads
are comparatively low, it is usually
when large gearing is involved (hence
larger loads) that this twisting affect and
backlash is more pronounced. Energy
is stored in twisted drive chain like a
twisted rubber band, so when the system
is disabled this elastic energy is released,
turning the motor backwards. Above are
real measurements of a maxon motor
fitted with a gearhead showing the
44
PECM Issue 14
release of this energy as it back drives
the motor.
In this case the motor rotated over 4
times when the drive was disabled. If
this motion is not accounted for it may
result in poor position accuracy. To hold
a position under load we would always
recommend a holding brake, especially
if the load exceeds motor continuous
torque specifications.
The maxon EPOS controllers have an
automatic brake control which controls
a brake as the motor is enabled and
disabled (timing of brake is adjustable by
the user).
By Mark Gibbons
Technical Engineer, maxon motor uk ltd
www.maxonmotor.co.uk