Drives enable reconfigurable sports stadium

Using technology never before applied to an Australian sporting venue, the former Olympic Stadium in Sydney has been reconfigured to meet a variety of sporting needs.

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.

And crucial to the success of the project has been a control network of drives and motors, designed, built and installed by Control Techniques Australia - a contract worth some $1 million to the company.

The design for Stadium Australia's Stage 2 post olympic configuration maximises the stadium's value to the community and offsets costs associated with the Sydney 2000 Olympic Games.

The new stadium has moveable stand sections to allow the whole stadium to be reshaped to make it suitable for Australian football (AFL), cricket, rugby union or league, soccer, concerts or racing.

Two stand sections are constructed on wheels that allow them to move in and out on rails, the rails being located in trenches under the playing surface to accommodate the AFL oval field.

In AFL games, these trenches are turfed to allow the full field to be used.

This remarkable design uses a unique arrangement of moving tiers, with post-tensioned cast in-situ concrete on steel and concrete columns.

This means that the inclined deck, which acts a stiff diaphragm during moves, remains uncracked during repeated movements - and the whole structure has a design life of 10,000 repetitions.

All of which adds up to an extraordinarily demanding specification for the movement of the stands, with a fixed time frame to meet deadlines for sporting events already booked.

When faced with the enormity of the task, the mechanical and electrical contractors weighed up the risks and withdrew, leaving the main contractor Multiplex with a big problem.

Multiplex handed the project over to civil contractor Structural Systems to complete the task.

That company approached Eilbeck Cranes, a long-standing Control Techniques Australia client to provide the mechanical movement of the tiers.

Ananda Sebastian, Managing Director at Control Techniques Australia was asked to look at the control requirements.

"On sight of the specifications, we had to give an immediate answer as to whether we would undertake the task", he says.

"We then had just two days to quote and received the order in November 2001 just 10 weeks from the completion deadline.

The key factor in our success was that our solution was simple and elegant compared to 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 (universal AC drives) with plug-in coprocessors, CT-Net communications, SYPT easy-to-use drive programming, CT 32 Scada, 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 moveable stands mounted on 14 bogies per side.

A centrally mounted 1.1kW braked motor and gearbox combination (785:1) on each bogie drives a 20-tooth pinion against the wheel gears.

The load ranges from 1000 to 1260kN.

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 has 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 communications linking the whole system.

A plug-in coprocessor on each drive gives the CT-Net networking and allows local programming to enable each drive to work in precise synchronism with all of the others.

A remote radio control operates each stand with ramped acceleration/deceleration to a maximum speed of 1m/min.

The control system for the project carries out two main tasks.

These are to control the synchronisation of all 14 drive bogies to ensure the exact relative positioning and to interlock so that movement cannot take place until all relevant checks have taken place and certain components are in a parked or locked position.

A great deal of data is processed prior to the system driving to ensure a failsafe system.

There is basically 14 times redundancy, in that any alarm can trip the system to ensure that no harm is possible.

The Control Techniques Unidrive system uses motor driven encoders giving 1024 pulses per revolution, with counts between bogies being compared, adjusting speeds to give a precisely parallel movement with no crabbing.

Additional data from sin/cos encoders mounted on the bogies, magnetic flags and limit switches give additional safeguards.

Accuracies of less than 1mm difference across the full 100m stand width and between adjacent bogies are achieved.

When the AFL mode is selected, the front nine rows of seats also drop down and retract beneath the seating deck to achieve the required oval shape.

Integral, moveable pedestrian bridges fill the gaps created between the reconfigured seating levels.

"Control Techniques Australia has an excellent track record of providing successful solutions to many industrial problems, and the end customer had good feedback on our ability to provide simple and reliable solutions", concludes Sebastian.

"This was a factor in our favour as was our technical back-up and 24x7 after-sales support.

Everyone was very pleased with the commitment of CT Australia in the execution of this task".

Stadium Australia (now renamed Telstra Stadium) was the largest Olympic stadium in history, with the capacity to host 115,000 during the Olympic Games.

Its new design, which has moved some 54% of seats in the stadium around 15m closer to the pitch, allows the stadium to be reconfigured to allow rugby union to be played one day and Australian football the next.

It takes just 15 minutes to change from oval to rectangular mode, making Stadium Australia arguably the first and only venue in the world that will do this on a regular basis - thanks to the drive power of Control Techniques.

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