Following its widely publicised £214m refit, the backstage area of the
Royal Opera House could now be described as poetry in motion. The
backdrops, light bridges, scenery wagons and even the proscenium arch are
nearly all moved under the control of ac drives - more than 300 of them!
With this number of drives, the design team needed to control the overall
complexity of the scheme so it decided to go the ‘preferred supplier’
route
Stage set changes at the Royal Opera House (ROH) are now considerably
faster thanks to a £20m plus investment in automation and motion systems
- ‘quiet’ ac drives and electric motors, hoists, gantry crane and
associated mechanical equipment such as gearboxes and hydraulic systems.
Early on in the project, ac drives quickly became one of the main focus
areas for standardisation as they are found in virtually all areas of the
theatre.
Control Techniques (CT) was appointed principal drives supplier because
it already had theatre automation experience with its Unidrive product,
and was also able to provide advice on the subject of harmonics - an
important issue for this central London location when anything up to 40
drives could be operating at any one time.- and suggest practical
solutions, such as active harmonic filtering The company worked closely
with three major contractor groups: Krupp/Stage Technologies on the
hoists; Telestage Associates on the proscenium arch, lighting bridge and
various elevators, and Clarke Chapman on the movable scenery wagons,
which make up the stage area.
Unidrives are used in flux vector mode to control the proscenium arch,
with four digitally locked motors providing the required synchronisation.
The lighting bridge is similarly controlled, but with two digitally
locked motors. These Unidrives are equipped with CT’s UD70 32-bit RISC
applications module and are connected via the CT Net fieldbus to the
ROH’s central control system (the ‘Nomad 3d’) at data rates as fast as
5Mbit/s. The UD70 module is used across all Unidrives applications
throughout the theatre to standardise programming procedures and achieve
the highest level of integration.
Situated near the rear of the stage, the pallet hoist can lift as much as
nine tonnes over 22m, yet it is required to stop within a tolerance of
just 1mm. Such specifications would normally be met by servo control, but
Telestage was able to achieve this result using a Unidrive operating in
closed loop vector control mode, thus avoiding the cost and complexity of
the servo system. The ac motor’s output is also more suited to the loads
imposed on it in this application. Some 37m above the stage floor are
quantities of fixed and point hoists, linked into the Nomad control
system via Unidrive ‘LFT’ lift drives, which operate at high motor
switching frequencies to minimise motor noise - even the cooling fans
‘whisper’.
The varied nature of the ROH’s productions means that there are a
staggering number of backdrops to choose from, all stored away in the
roof and inched down when required to a gantry crane that delivers them
to the fly tower. this crane is controlled by a Unidrive equipped with a
joystick interface to provide a ‘creep’ mode of operation. This
arrangement also provides an ‘analogue’ method of programming by allowing
the crane to be advanced to set positions under manual control. An
local UD70 module and this is ‘learned’ by the drive, enabling the same
positions to be achieved under fully automatic control.
“The reopening of the Royal Opera House on December 1 1999, after being
closed for nearly two and a half years, was the culmination of a project
that moved it into the first division of theatre automation in the 21st
century,” ROH project manager Jeff Phillips proudly boasts. “The
achievement of the project engineers and contractors in integrating so
many aspects of theatre technology under the auspices of a single control
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