Drives play major part with Royal Shakespeare Company
14th May 2012
The four-year, £112 million transformation of the Royal Shakespeare Theatre in Stratford-upon-Avon, which includes automation of back-drop and scenery movements, as well as lighting arrays, involved installing 100 ac drives and servo motors.
Dutch theatre automation company Trekwerk was responsible for renovating the over-stage installation, covering 60 winches plus the hoists for 30 light arrays – all of which are based on Control Techniques drives.
"The winch system is very advanced and gives us much greater flexibility in set design and operation," copmments RSC's head of automation Adam Harvey.
"Safety is paramount, of course, and this is inherent in the whole project. It is very important to maintain the theatrical illusion, and the reliability of the many winches involved in each production is crucial. We haven't had a single drive fail, which is a great result."
All of the winches have been fitted with Control Techniques 15kW Unidrive SP ac drives, operating in servo mode and twinned with Unimotor 190 fm servo motors, fitted with double encoders for precise positioning and speed control.
A total of 46 drives were fitted to 60 winches, with at least half of these being positioned above the thrust stage. Any of them can be configured for different duties, from lifting scenery to controlling the flying of actors.
Sixteen of these winches are positioned in the 'slot area' specifically for stage reconfiguring and 14 Trekwerk SynchroDisc winches give silent five-line lifting of 'flybars' for rapid changeover of scenery during productions.
Each winch drive has been fitted with an SM-Applications Plus module programmed to control all of the winch motions, with the load being calculated internally, based on current drawn by the motor and checked against a load cell for safety.
Further, each motor was fitted with both an incremental encoder for speed control and a Sin/Cos absolute encoder for position feedback. All winches are capable of lifting at 2 m/s, and 60 of them are of Trekwerk's SynchroTwin design – meaning that one drive can control two 2m circumference winch cable drums either independently or synchronised together.
Author: Brian Tinham
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