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Advanced Lift-60 truck Technology International 2019
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CURTISS-WRIGHT
THE RIGHT SENSORS CAN HELP MACHINERY TO OPERATE SMOOTHLY AND
SAFELY, EVEN WHEN TILTING OR ELEVATING
Curtiss-Wright Industrial designs and
manufactures components and sub-systems
for mobile elevating work platforms, variable lifts
and access equipment – including vertical mast
lifts, indoor scissor-lifts, outdoor rough-terrain
scissor-lifts, articulating and telescopic booms.
The new ANSI A92.20 standard applies to
access equipment and implications for the fitting
of additional or alternative sensors to mobile
elevating work platforms (MEWPs), including
scissor- and boom-lifts.
High standards
The new ANSI A92.20 standard covers design aspects
of access equipment and replaces two existing
standards: the A92.5 and the A92.6 for boom- and
scissor-lifts respectively. Additionally, A92.20 defines
the term mobile elevating work platform (MEWP)
to replace aerial work platform (AWP),
and then further defines by type.
Much of the content of ANSI A92.20 harmonizes with
EN 280:2013+A1:2015, which itself refers to EN ISO
13849-1:2008 for guidance on the implementation of
safety functions. With regards to safety function
implementation, the new ANSI standard also references
EN ISO 13849-1.
From a fitment of additional or alternative sensor
perspective, there are two elements of ANSI A92.20
that should be referenced – chassis inclination and
load sensing system.
Chassis inclination
ANSI A92.20 requires every MEWP to be fitted with a
means of detecting that the chassis is not tilted beyond
safe working limits and, if it is detected, then further
operation of the MEWP must be prevented. A similar
requirement existed in both A92.5 and A92.6, but this
only required a warning to be issued, rather than
prevention of operation.
As machine operation now has to be prevented, it is
likely that higher-performing tilt sensors will be
required; sensors that can measure both tilt and
vibration can filter out unwanted effects at the source,
therefore leading to a quicker response of actual tilt
angle, regardless of whether vibration is present. This
performance can be provided by inertial measure unit
(IMU) based sensors.
Curtiss-Wright’s VTS2021 dual-axis, vibrationtolerant
tilt sensor uses the latest IMU technology
and fast-acting software algorithms to filter out
disturbances caused by vibration and vehicle motion.
This provides output stability without the measurement
delays usually associated with heavily-damped,
traditional sensing methods.
The VTS2021 feeds output data over CANbus using
the SAE J1939 protocol, with each measurement axis
having two sensing elements that are constantly
compared to ensure correct operation. If an error is
detected, its condition is communicated to the host
electronics to ensure a safe operating situation is
assumed. Additionally, each output signal is calibrated
to account for thermal drift, ensuring accuracy over
the operating temperature range.
Load sensing
This requirement relates to MEWP operation and the
amount of physical load (or weight) on the platform.
Essentially, the maximum permissible platform load will
vary and depend on platform position. Sensors that
detect both position and load are therefore required.
Curtiss-Wright’s NRH27x series of non-contact
rotary position sensors offer an optimal combination of
performance, safety and cost for MEWP OEMs designing
vehicles and control systems.
Specifically, the NRH27C, a non-contact rotary
position sensor offering a CANbus J1939 output, is ideal
for OEMs of on- and off-highway vehicles destined for
challenging environments; and as a cost-effective
solution for medium volume applications where a wide
range of options or degree of customization is required.
The NRH27C’s two, physically-independent,
Hall-effect sensing signals are sent separately with
the CAN message, allowing for error checking of
positional data and meaning that high-performing,
safety-critical applications can be addressed. An
on-board diagnostic function means predefined error
messages can be sent to define the present state of
the sensor. The versatile, factory-programmable
electronics can also be set to different baud, node
ID and frame rates. ALT
Author: Christian Howe, marketing manager,
Curtiss-Wright
Safety at all levels
The VTS2021 is a
dual-axis, vibration-tolerant
tilt sensor offering optimal
performance and safety
/pivt