PLC control for AV and stage integration

Intro: Having previously worked for Madame Tussauds we were asked to help in the refurbishment of the Animatronic figures at Rock Circus. That bit was easy, but the remit soon expanded to include what turned out to be a complete reverse engineering the entire show ride and stage machinery system.

The Challenge: During the refurbishment it was discovered that the control system had become obsolete and was no longer supported by the manufacturer, furthermore the original stage machinery company had also gone out of business and finally there were no drawings for either system.

The show: Consisted of a revolving theatre on a 20 ton turntable, split into three segments each seating 110 people. The stages were around the outside edge of the turntable and had stage sets and Animatronic figures lifted from stage pits to the audience level, this was synchronised to music, video and lighting. Movement from one theatre to the next took less than 30 seconds and needed to be synchronised with both the show and safety interlocks for the entry and exit of audiences.

The solution: With no original paperwork and no manufacturer support we had no choice but to completely reverse engineer this system. The key to our success was understanding how the show and the various elements worked together if even the precise details of what connected to what was unknown. So for example there was a relay box colloquially known as Arthur’s box after the guy who had originally built it. Sadly Arthur had passed away some years before the company had gone out of business so no clues or help there. However we did know that Arthur’s box was an interface between the extra low voltage control system and the three phase stage machinery, all we had to do was decode the relay logic and test each circuit safely. Once we had completed this and understood what Arthur’s box did and how, we could start to design a replacement control system to bridge between the existing AV control and the mechanical control. To help us understand this we created a flow diagram to show the logically interactions between the AV show control, the mechanical control and the safety control. This diagram screamed PLC us, all the input and outputs triggers to the various systems were all relay/contact closure based and the if then else logic for the control was easily accommodated by a PLC. The PLC also allowed for offline simulation testing and easy on site modification to the system.

Customer Benefit:

We retained >90% of the original system and as such saved Madame Tussauds a huge cost to re-engineer and replace the whole system without which the exhibition may not have been commercially viable to continue.

We improved the safety of the entire system.

We completed this work with no delay to the program and the our system worked until the exhibition was finally closed some years later.