Creating history: Motion control, industrial communications challenge

With more than 1.65 million annual visitors and an extensive collection of artifacts and scientific specimens, Chicago’s Field Museum of Natural History has among its wonders the technology that supports its exhibits. That includes variable speed motion controls that move live hanging garden “clouds” (up to 19,000 pounds), with variable speed in acceleration and deceleration using a wireless pendant. It’s believed to be the first freeform 3D printed garden.

A team from Chicago Flyhouse designed a system to suspend a live hanging garden, called Nature Clouds, to showcase plants living from the prehistoric era. Four “clouds” range in weight from 5,000 to 19,000 pounds, each suspended above the museum floor. The clouds’ needs are supported via an energy chain flexible cable tray that includes cables that provide water, power and fiber optics to the living sculptures suspended by high capacity hoists.

“We have done many projects of this scale and larger,” said David Millard, project manager for the Flyhouse. “We specialize in the unique and difficult. This fits the criteria of a unique and difficult project that required immense attention to detail and aesthetics.”

Motion control project included prototype rigging

For the museum’s 125th anniversary, architects and engineers from The Dobbins Group asked for insight into the feasibility of suspending four clouds. The Flyhouse created a full-scale prototype of the rigging.

To suspend and move the clouds, Flyhouse designed two large and one medium capacity hoists. The clouds have a travel speed of 16 feet per minute with variable speed in acceleration and deceleration. They travel to three pre-set positions using a wireless pendant on the main floor.

The clouds are the world’s first freeform 3D printed garden. Designed by Branch Technology, the clouds have 279 printed parts and include more than 12,000 pounds of vegetation and support equipment weight, 9,650 pounds of steel and almost 4,000 pounds of printed component weight.

They are comprised of correction vegetation of the Cretaceous period, hydroponics, lighting, theatrical fog and sound equipment.

“The project is about bringing the missing vegetal dimension into the Field Hall,” Daniel Pouzet said in an article published by the Chicago Tribune, “Hanging ‘plant clouds,’ pterosaurs to join crowd in Field Museum’s Stanley Field Hall makeover.” Pouzet, a French architect, designed the clouds with Field design director Alvaro Amat. “The clouds are meant to be a bridge between the extremely rich but inanimate matter of the museum and the ever-evolving living elements.”

Compact motion control challenge

Millard said the primary challenges involved designing high-capacity hoists that could move the clouds quickly and small enough to fit within limited spacing. They also faced multiple mechanical obstructions as they set up the rigging system in the small confines of the attic at the Field Museum.

The Flyhouse team designed, engineered, fabricated and installed three hoists between the museum’s lay lights and skylights. Each hoist was designed as a double helix zero fleet line shaft hoist with redundant braking and cable management system.

“We did all the rigging during regular hours while no part of the museum was closed to visitors,” Millard said. “This required us to develop a custom-suspended floor structure that was capable of supporting 28 tons over a 1,250 square foot surface that acted as a hoist and a protective layer between our work and the general public 75 feet below us.”

Long-travel energy chain for motion control applications

To assist with the movement of the clouds, the Flyhouse team used a 75-foot energy chain. They designed the system in which a pulley allowed them to pull the chain at the bend of the chain, instead of the typical pushing or pulling at the end.

“We tied the movement of this pulley directly into the hoist,” Millard said. “We created a series of mechanical advantage systems to allow the pulley for the chain to travel at exactly one half the rate of the suspended clouds. Since we are moving the middle of the chain, the chain moves at twice the speed of the pulley at the bend in the chain, thereby making it sync exactly with the moving cloud.”

Project uniqueness revolved around the center support of the energy chain. It allowed the Flyhouse team to control its movement from the middle, instead of one of the ends.

“The customer service allowed us to get the information we needed about the product to allow us to confidently and safely use it in an unconventional way,” Millard said. “They were able to provide us the load data necessary to design this solution and were active and interested in working on a non-conventional solution for the product.”

Critical data cables: fiber optics, power, water

The energy chain also carries cables from the motion plastics specialist that provide water, power and fiber optic to the sculptures. Four of the flexible cables, such as those for fiber optics and air line for water, are 100-feet long. There is also a 300-foot cable, which is typically used in heavy duty indoor applications and in high bay warehouses, packaging machines and indoor cranes. The cables have a long service life and require little maintenance.

“It has been our experience that cable reels are unreliable in the long term and we needed a solution that was going to mechanically move the cable and hoses in sync with the hoists,” Millard said. “The key was to prevent the system from adding complexity, such as synchronized motors.”

The energy chain needed to be wide enough to accommodate all of the various cables, which helped with the movement of the clouds.

The flexible cable design used dimensions of the fill package by Chicago Flyhouse, including spare space for possible new cables.

Lessons learned in motion-control prototype modified final design

The exhibit is now a museum favorite. There are more than 1,000 individual plants spread across the four suspended structures, including one that is 35 feet across. It is the world’s largest 3D printed garden. The Flyhouse team spent more than a year developing the feasibility of the overall design before determining how they would lift and move the clouds. “We spent time setting up factory mockups of the clouds and worked actively with the engineering firm that designed the 3D printed structure and skeletal frame of the cloud,” Millard said. “We provided active feedback from the lessons learned in the mockup and helped them modify the design to work well as a suspended object to make sure it fits all of our criteria for safety of lifting overhead, including the ability to handle an abrupt stop and the resulting shock load in the event of an emergency stop or secondary brake lock.”

The engineering involved in creating Nature Clouds helped to create a breathtaking and wondrous museum exhibit.

“These gardens are the first of their kind, and we worked to find plants that will thrive and were inspired by plants living during the time of the dinosaurs: ferns, cycads, and arum plants,” senior exhibitions project manager Hilary Hansen said in an article, “Flying reptiles and hanging gardens to join largest dinosaur ever discovered at Field Museum,” published by Chicago Curbed. “The plants make the hall come alive — they look beautiful and underscore our mission to study and preserve the natural world. They’ll break up the imposing scale of Stanley Field Hall and soften its hard materials, making it a welcoming place to sit and enjoy nature.”

Dan Thompson is the energy chain product manager for igus. Edited by Mark T. Hoske, content manager, Control Engineering, CFE Media, mhoske@cfemedia.com.

KEYWORDS: Motion control, flexible industrial conduit, industrial cableCONSIDER THIS 

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Watch a YouTube motion control application video from igus above one of the garden clouds at Chicago’s Field Museum of Natural History.

Learn more about the Field Museum of Natural History.

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