FEATURE LINEAR MOTION
THE POETRY OF MOTION: WHERE ART MEETS
AUTOMATION
A complete solution of mechanical components and automation has enabled Only Breath, a mesmerising kinetic sculpture installed in The Science Museum, to move in a smooth motion, giving visitors the impression that the sculpture is breathing. Here, HepcoMotion explains how it met the complex challenges of this unusual application
L
ocated in London’s Science Museum, Only Breath is a mesmerising kinetic sculpture that seamlessly blends art and engineering. As the centrepiece of new Energy Revolution Gallery, this features spiral petal frames that move in a smooth, rhythmic motion, so it appears as though the sculpture is breathing or blooming. When fully open, the sculpture expands to nearly 5m in diameter. But how was this motion achieved?
THE CHALLENGES The sculpture was designed by artists Alexandra Carr and Colin Rennie from Torus Torus Studios who decided gentle and precise motion was necessary to create the life-like effect. The sculpture required a sinusoidal movement path, characterised by a smooth, wave-like oscillation, rather than a conventional linear or circular motion. The movement needed to be so smooth and subtle that it initially appears almost imperceptible, leaving viewers questioning whether the motion is their own or the sculpture’s. The transition from stillness must be gentle and seamless, allowing the sculpture to unfold gracefully and elegantly as a flower blooming in a time-lapse. Not an easy task. The complexity of the shape and dynamic
movements present numerous challenges. Ensuring ultra-smooth motion without abrupt transitions or deviations demands a motion control system with high-quality feedback mechanisms and precisely tuned motion control parameters. Sinusoidal motion also presents challenges due to the forces generated by the continuous changes in acceleration and deceleration, potentially leading to dynamic stresses on mechanical components. The system must be designed to endure these stresses
38 DESIGN SOLUTIONS FEBRUARY 2025
to meet the application’s unique requirements. At the core of the mechanism, two Hepco ZIMM screw jacks, operating in sync with a connecting shaft and powered by a single motor, move the petal frames vertically over a 500mm stroke with a sinusoidal speed profile. The inward and outward motion is guided by 27 Hepco round linear bushings and shafts connected to a frame that follows the cell structures of the petal frames. Two Hepco telescopic slides provide enhanced guidance and safety, essential for a sculpture displayed in a public setting. The sinusoidal motion was
achieved by designing a virtual CAM cycle that defines the motion profile. The servo drive follows this cycle, controlling
while ensuring smooth and reliable operation. It turned out that companies could provide either the motion control system or the mechanical components, but not both. Some even declined due to the complexity of the project. HepcoMotion, however, was up to the challenge. The company offered the combination of a complete service, from the design of the ZIMM system, supply of linear rails and bushings, to the design and programming of the full servo control system and dedicated HMI.
THE SOLUTION HepcoMotion supplied both the mechanical components and, through HepcoAutomation, the motion control system. The sculpture consists of 23 moving stainless
steel frames containing 92 windblown native timber panels, with each frame meticulously controlled by Hepco’s advanced motion control systems. HepcoAutomation provided a complete turnkey solution, including the control and safety systems, manual overrides, motion profile settings, and HMI interface positioning
the motor’s position, speed and acceleration to generate the smooth, oscillating movement. To prevent damage during sinusoidal motion, a reference torque curve was created to represent expected torque values. The system continuously compares the actual torque to this curve, stopping operation and alerting the operator if deviations suggest potential mechanical issues.
RELIABILITY The system offers three cycle selections – daily, event, and showcase – each with varying speeds for the sculpture’s opening and closing. The sculpture has a required lifespan of 15
years, with very few maintenance requirements – with the Science Museum open 362 days a year, the sculpture must remain reliably operational for visitors, making unplanned downtime highly undesirable. The ZIMM screwjacks are fitted with lubricators, requiring only a precautionary check every three months.
HepcoMotion
www.hepcomotion.com
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