Behind all the excitement and happy faces surrounding the thrill rides and stage shows at theme parks is the very serious business of keeping people safe. And that’s no easy task in an environment where those people are often surrounded by tons of moving metal and other potential hazards.
“It’s a great time to be a control engineer in the entertainment industry,” says Mike Miller, global business development manager for safety, Rockwell Automation. “This industry really embraces automation and the latest control technologies. You’re always being challenged to take the technology another step. What we’re doing today could only be dreamed of 10 or 15 years ago.”
It’s a mindset that most control engineers working in factory automation can only envy. While they use many of the same tools—from controllers, drives and sensors to Ethernet networks and wireless communications—engineers in manufacturing industries often find their companies reluctant to get anywhere near technology’s cutting edge. Not so with the theme park industry, where continually delighting customers with thrilling new visual and physical experiences spells increased traffic and profits. And it’s at this edge of technology where the capabilities of control systems are truly put to the test.
Beyond the sheer spectacle of what these engineers have been able to accomplish at theme parks around the world, their experience also offers useful lessons for the industrial world.
“In designing control systems for the entertainment industry,” says Miller, “we try to use the latest technology. You need that level of sophistication to elevate the entertainment wow factor while making sure there’s always a very high degree of safety, predictability and reliability. Technology gives designers a lot more flexibility to push the envelope.”
Miller points to the widespread use of safety PLCs in rides as one example where the entertainment industry is far ahead of factory automation. “The advanced diagnostics let you react to failure faster and take the needed corrective steps. There’s also greater predictability because you can be confident it will fail safe, which simplifies control system design. In the factory, safety is too often an afterthought,” he says.
Miller says technological advances in three component categories have been critical to achieving the sophisticated control system designs needed by the entertainment industry: greater flexibility and processing power of controllers, advanced motion control systems, and interconnectivity and real-time access to information achieved through Ethernet and wireless networks.
Artistry in motion
In addition to theme park ride development, the integration of these technologies made possible the modernization of the moveable stage used in the Cirque du Soleil production at the MGM Grand in Las Vegas. Four 70 foot tall hydraulic cylinders extend down through the roof of the hotel to pull the 70 ton, 1,400 square foot stage upward. Four additional hydraulic rams provide a 100-degree tilt range. The stage can also rotate 360 degrees.
The new motion control system designed by Siemens adds failsafe redundancy, cost efficiency and real-time HMI monitoring to the production, reducing the potential for a single-point failure that could bring the stage and an entire performance to a sudden stop.
The redesign’s central challenge was to transition the massive live theater production from a system based on pressure management to one based on openly dynamic positioning and control. It was achieved using safety controllers to govern paired, redundant master-and-slave motion controllers. All encoder-based motion applications have as many as four encoder backups, each controlled by a “voting” system that instantly detects and “votes out” a failed encoder to automatically bring the next encoder online.
The interplay involved between human performers and the stage made this application unique. Instantaneous redundancy regulates the hydraulic energy in a way that brings stability and confidence to the actors and makes the whole production work more smoothly. The high level of redundancy also extends to bus-level communications, with the integration of both Profibus and Ethernet connectivity.
“The production crew can now manage a lot of data,” says Kimberly Cornwell, one of two Siemens application engineers on the project. “The redundancy in the communications was complex, with over a thousand possible ways to flow data back and forth from one network to another, from the main power controllers to the backup main controller and between the redundant motion controllers. We programmed for interlocking, keeping pumps running, turning pumps on so we have pressure, opening and closing valves, and providing for different shutdown scenarios.”
Dozens of HMI stations around the complex allow operators to bring up more than 200 different screen views. The system’s real-time responsiveness lets the show’s director issue a cue that interfaces with the controllers and selected monitors, explains application engineer Barry Hawley. “In the event the actors are not in position, cues can change according to the live action. The flexibility of this motion control system makes for a very flexible production.”
A hybrid approach
While the nuts and bolts involved in controlling rides are the same as those used in a factory, the environment is very different. Controllers, sensors and I/O are often mounted on the ride vehicles themselves and so have to act reliably outdoors, no matter the heat, humidity, rain, wind or dust. There are also other conditions not experienced in a factory, such as birds flying in front of sensors and the bodies of people absorbing or blocking the energy from RF signals.
The control of thrill rides is a hybrid between process and factory automation, says Kevin Smith, consulting sales application engineer, who is part of a large network of Siemens engineers involved in technically advanced programming at Walt Disney Theme Parks and Resorts in Florida and California, as well as their other entertainment venues such as cruise ships.
“You need continuous operation, as in process automation, and fast response times, as in industrial automation,” explains Smith. “You also have to be as close to perfect as possible because of all the people who interact physically with the attractions.”
The two companies have been allied since 2005, allowing Walt Disney Parks and Resorts to apply engineering advances to contribute to the guest experience while providing a platform for Siemens to showcase its technologies.
Siemens industrial systems are found behind the scenes in many Walt Disney World Resort venues, including some of the more recently introduced rides such as the Seven Dwarfs Mine Train, Dumbo the Flying Elephant and Under the Sea—Journey of the Little Mermaid. Siemens equipment also delivers real-time information to Disney’s attraction operators for improved safety, efficiency and communication.
Along with robustness, security is a critical part of control system design for Walt Disney theme parks, says Smith. In Cars Land, for example, a recent attraction based on the hit movie “Cars,” engineers had to install radio equipment underneath the cars used in the ride, away from guests. “We didn’t want people to be able to access the system from their smartphones.”
The use of wireless communications is growing rapidly in thrill rides. In the Cars Land attraction, for example, a hardened, proprietary PC-based Siemens system provides point-to-point coordination and real-time deterministic communications, which is not natively part of Wi-Fi certification, says Smith. “This enables fast response to every vehicle on the wireless link, allowing controllers, safety systems, drives and I/O to respond in fractions of a second.”
Smith says Siemens engineers expect to encounter similar challenging wireless situations in industrial applications in the future. “The probability is very high that we’ll encounter similar problems in a factory at some point and we’ll be able to share with customers what we’ve learned in the Disney applications.” To make sure that happens, Siemens engineers worldwide log their solutions with the company’s hotline and its development group in Germany.
It doesn’t take a big theme park like Walt Disney World to take advantage of advanced automation technology. Two examples from Europe, a “waterdoor” at the World of Water exhibit in the Swiss town of Flims and a rider-controlled “flying” tower in Germany, both illustrate how safety can be incorporated into equipment designs from the start.
Renamed “Sinfonia d’aua,” the water exhibit was created after an underground lake was accidentally tapped during the construction of a tunnel. The water supply is now used as drinking water, to cover nearby ski slopes with artificial snow, and for power generation. The attraction utilizes technology to show visitors the ecological relationship between the mountainous region’s water sources and humans.
The project was engineered by AS Systems, long active in international light, sound and stage projects, including complex water displays. The interactive exhibit features a rail containing hundreds of water jets mounted over a door lintel. A Beckhoff embedded PC and EtherCAT relay terminals provide control for the jet assembly.
Each of the digital I/O terminals has eight switches that function like relay contacts for AC/DC voltages, and each switch connects to transistors that assure low startup resistance to prevent high voltage peaks and electromagnetic interference.
When the door radar detects a visitor approaching, the water curtain opens from the center, similar to a theater curtain, and then closes after the visitor walks through. The LED rail also illuminates the water drops by refracting light, allowing images and messages to be created.
The compact PC controls a total of 144 data points, regulating water levels and flow speeds, as well as valve settings. Water tank safety is controlled using Beckhoff TwinSAFE I/O terminals that differentiate between rising water levels caused by the curtain being open beyond a certain period of time or because of drainage problems.
On the “flying” tower project in Germany, human interaction was an even bigger focus because riders actually control the ride’s movements. Built by Gebr. Heege GmbH, a family-run business in Laubach, Germany, the 9 meter tower is equipped with four double seats, each with its own motor-supported drive, allowing passengers to select the height and speed of the ride.
A cable attached to the seat controls the ascent speed. The more strongly the rider pulls on the cable, the faster the ascent. When the cable is released, the passengers descend at a gradually slowing rate.
To continuously monitor the descent and allow a supervisor to intervene in the event of a mechanical failure, the company used sin/cos encoders and a stand-alone, safety-relevant speed monitor from Phoenix Contact. The 45 mm module monitors the speed of the rotating parts in machines and systems. Its software allows engineers to vary the setpoint for the standstill signal and over-speed thresholds based on application requirements.
The combination of measured value sensing (sensors), monitoring (logic) and a magnetically operated switch with braking unit (actuator) ensures that if an over-speed condition is detected, the double seats come to a standstill in less than a second.
After the start command at the frequency converter, the higher-level control system expects a motion signal that is fed back from the two-channel standstill contacts of the speed monitor. If a positive feedback signal is not received within one second, the control system immediately initiates an emergency shutdown of the drive.
In addition to setting safety parameters, a space-saving design and high system availability were important to the ride manufacturer. “The parameterization of the standstill and speed monitor turned out to be simple, and the tower’s complete safety system has proved to be stable and reliable,” says Walter Dörksen, design engineer.
Redundancy, instantaneous feedback and strict attention to human safety are integral to engineering an entertaining ride—or an efficient production line. As Rockwell’s Mike Miller emphasizes, “If something fails, you don’t want to have to turn the lights on and spoil the magic.”