Even such unlikely acting prospects as Emerson have played a role in the four-year, $139 million transformation of the Royal Shakespeare Theatre (RST) in Stratford-upon-Avon, U.K. The upgrade included a major project to automate the movements of backdrops and scenery and the complex system of lighting arrays designed and installed by Trekwek, a Dutch theater automation company. At the heart of the project are around 100 AC drives and servo motors from Control Techniques. Trekwerk renovated the over-stage installation, including development, design, manufacture and installation of 60 winches plus hoists for 30 light arrays.
Each winch drive is fitted with an SM-Applications Plus option module programmed to control all winch motion, with the load calculated internally based on the current drawn by the motor, and checked against a load cell signal for added safety. Each motor is fitted with an incremental encoder for speed control and a Sin/Cos absolute encoder for position feedback. All winches are capable of lifting at 6 ft per second. Sixty of the winches use a unique design, SynchroTwin, which allows one drive to control two 6-ft circumference winch cable drums independently or synchronized together, which saves space in the overcrowded area above the stage.
One DC bus fed by two rectifiers feeds all drives. During braking, recovered energy is recycled via the drives to the DC bus, producing some energy savings. All drives that communicate with each other using Control Techniques' own high-speed network, , also communicate via CTNet with Trekwerk's control system.