Using technology never before applied to an Australian sporting venue,
the Olympic Stadium in Sydney has been reconfigured to meet a variety of
sporting needs. At the heart of this project is a network of drives and
motors that can be deployed to move 100m long stands to millimetre
accuracy
Stadium Australia's Stage 2 Post Olympic Configuration has movable stand
sections that allow the whole stadium to be re-shaped to make it suitable
for Australian football (AFL), cricket, rugby union of league, soccer,
concerts or racing. Two stand sections are constructed on wheels that
allow them to move in and out on rails, located in trenches under the
playing surface, to accommodate the AFL oval field. For AFL games, these
trenches are turfed to allow the full field to be used. Additionally, in
AFL mode, the front nine rows of seats drop down and retract beneath the
seating deck to achieve the required oval shape, with integral movable
pedestrian bridges filling the gaps created between the reconfigured
seating levels
The civil engineering element involved the construction of moving tiers,
with post tensioned cast in-situ concrete on steel and concrete columns.
This ensures that the inclined deck - which acts as a stiff diaphragm
during moves - is not fractured during repeated moves. The whole
structure has a design life of 10,000 repetitions. However, when it came
to the mechanical and electrical elements of the project, the time
constraints and the enormity of the task ahead of them, forced the
original M&E contractors to withdraw, leaving main contractor, Multiplex,
with a crisis. In the end, the project was handed over to Structural
Systems to complete the works, who subcontracted Eilbeck Cranes to
provide the mechanical movement of the tiers. Eilbeck is a longstanding
Control Techniques Australia (CTA) client and the latter was duly called
in to review the electrical control requirements. CTA managing director,
Ananda Sebastian takes up the story.
On sight of the specifications, we had to give an immediate answer as to
whether we would undertake the task. We then had just two days to quote,
finally receiving the order just ten weeks from the completion deadline.
The key factor in our success was that our solution was simple and
elegant compared with previous attempts, and had the added advantage that
it was easy and low cost to install. The solution involved a wide range
of Control Techniques products, including 28 2.2kW Unidrives with plug-in
co-processors, CT-Net communications, Sypt drive programming software, a
CT32 SCADA system, Sin/Cos and optical encoders, additional plug-in I/O
units as well as two front end touch screen computer operating stations.
The stadium has two fixed stands and two movable stands mounted on 14
bogies per side. A centrally mounted 1.1kW braked motor and gearbox
combination (785:1 ratio) on each bogie, drives a 20-tooth pinion against
the wheel gears. The load ranges from 1,000kN to 1,260kN. On each side,
the central two bays are fixed between the column and bogie to prevent
drift, all other bogies are fitted with bushes to allow a maximum drift
of +/-10mm, although this was found to be unnecessary in practise because
of the accuracy of the Unidrives. Central earthquake bracing shoes lock
into sockets at the front and rear positions, and the whole structure is
locked into place before occupation.
The control computer for each stand uses one 2.2kW Unidrive per bogie,
with CT-Net linking the whole system. A plug-in co-processor provides the
networking capability and allows local programming to synchronise all the
drives. A remote radio control operates each stand with ramped
acceleration/deceleration, and a maximum speed on one metre per minute.
The control system carries out two main tasks: to control the
synchronisation of all 14 bogie drives, and to interlock so that movement
cannot take place un