In an indication of just how seriously North American engineers are taking integrated safety in applications where life and limb are on the line, Walt Disney Imagineering and Siemens Energy & Automation have together been working on a PLC-based safety system for busbar powered rides.
For the past 30 years or so, Disney has entrusted some safety tasks on these rides to a custom Power Bus Controller of its own design. According to Jody Gerstner, Imagineering's executive director of show and ride controls, the controller provides a “redundant, testable” way to remove power to all or part of a ride in the event of a safety fault.
Literally a black box is located in a ride's control cabinet, the controller communicates with various sensors — such as pressure mats — located on and around a ride's moving parts. Gerstner describes the controller as “hierarchical based on the severity of the fault.” Minor faults might disconnect power locally while major faults can quickly remove power from the entire ride.
Currently in its third generation, the system has been used on Disney's Toy Story Midway Mania, a newly opened attraction at Disney's California Adventure (read the full story at http://rbi.ims.ca/5719-541). Yet, Disney is now looking at ways to integrate the bus controller's safety functionality into ride control PLCs. “I believe there are opportunities to simplify our safety systems using integrated safety. It's something we're definitely looking at for the future,” Gerstner says.
And that future may not be very distant at all. Siemens, one of Disney's corporate technology partners, has already integrated Disney's Power Bus Controller functionality into a SIMATIC S7 319 PLC using ProfiSafe safety communication technology. According to Olaf Scheel, a Siemens engineer who worked on Midway Mania's design team, the new safety system is essentially a software implementation of Disney's unique safety requirements. “We replicated what Disney has been doing in standard hardware,” he says, adding that the integrated safety system saves the cost of manufacturing and installing the custom safety hardware.
Scheel says the Integrated Power Bus Controller remains in the prototype stage for now, though Siemens did develop it for an older ride that's undergoing a controls upgrade right now.