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National University of Singapore
Industrial crane operators typically
manipulate the independent
motions of trolley, hoisting and
traverse when they are moving
payloads. This, however, can result
in an uncontrolled swaying motion,
which slows down the construction
process because extra time is
required to let the swaying motion
come to a stop. Uncontrolled
swaying is also a safety issue that
can result in serious injury.
Led by associate professor Ong
Chong Jin, researchers at the National
University of Singapore’s Mechanical
Engineering Department have developed
a highly effective solution to
the control of payload sway
in industrial crane and cranelike
structures. The “Anti-
Sway Control of a Crane
under Operator’s Command”
technology was developed
in 2000.
In response to the operator’s
command for trolley, hoist and traverse
motions, this software program utilizes
a family of differential equations
to calculate the precise counteradjustments
necessary for canceling
out sway. The differential equations
are solved in real time, using sensory
measurement of the cable length and its
time derivative.
The program also responds
immediately to the operator’s commands
under simultaneous trolley/hoisting and
traverse/hoisting motions. The software takes into account the acceleration,
velocity, and span limits of the drive
system of the crane to ensure the anti-sway control is not compromised
when these limits are reached. The use of this technology on construction sites
improves safety; labor costs are also
reduced because operators spend
less time waiting for swaying motions
to cease.
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