The wobbly however exact high-torque Harmonic Drive gear

The Harmonic Drive is a key a part of numerous robotic purposes. Extremely easy but fairly odd to look at, this gear system is extraordinarily exact with a formidable torque-to-weight ratio, even when it does wobble. So how does it work?

The seemingly weird Harmonic Drive gear is definitely moderately genius in the way it features – its flexible-ellipse-within-a-circle setup creates a wobbling movement because it turns, and locations solely a few third of its two predominant gears’ tooth in touch with one another at any given level – however the result’s a remarkably compact and lightwight little drive gear able to delivering wonderful torque with absolute precision, and nil drive lash or free play.

It was first conceived in 1957 by Pennsylvania’s C. Walton Musser, a splendidly artistic inventor with patents on all the things from energy steering techniques, recoilless rifles and pneumatic life jacket inflators, by to many key concepts underpinning jet plane ejection seats. The Harmonic Drive was first commercialized by the early Sixties. It is fabricated from three key parts:

Harmonic Drive

• The wave generator: A barely elliptical enter hub with a ball bearing race round its periphery.
• The flexspline: A versatile, cup-shaped element with tooth on its outer perimeter. It deforms radially however retains torsional rigidity when the rectangular wave generator is inserted.
• The round spline: A totally inflexible ring with inner tooth, just like a planetary ring gear, and with two extra tooth than the flexspline.

When the wave generator spins, about 30% of the flexspline’s tooth on both finish make contact with the round spline’s tooth at any given time, forming an advancing wave sample. This causes the flexspline to rotate inside the round spline, however in the other way of the enter. Test it out:

A part of this method’s genius is its zero backlash – there isn’t any play between the gears, making it very best for exact, high quality motor management. Its compact, light-weight design can be good for purposes with restricted house. And with few transferring elements, the Harmonic Drive is extremely dependable and sturdy.

At this time, Harmonic Drives are in all places on and off planet. Industrial robots like these from Fanuc and Common Robots use them for duties reminiscent of welding and meeting, the place repeatable, exact movement is crucial.

The da Vinci surgical robotic, designed for minimally invasive procedures, depends on Harmonic Drives in its arms, giving it delicate micro-movements with zero backlash for the utmost precision whereas performing minimally invasive operations on folks.

Harmonic Drive

Boston Dynamics’ Atlas humanoid and Spot Quadruped robots use them of their legs and arms, amongst different locations, to realize easy, managed movement whereas nonetheless being sturdy.

Even NASA’s Mars rovers, Curiosity and Perseverance, function Harmonic Drives of their robotic arms and wheels. Sending rovers to a different planet with no hope of upkeep or restore stops is a testomony to the reliability and sturdiness of this design.

Whereas Musser by no means lived to see his invention attain Mars, he did at the very least witness it go to house. The Harmonic Drive was widespread element within the House Shuttle’s standard-issue Distant Manipulator System – aka “Canadarm” – used on shuttles like Columbia and Challenger to deal with payloads and deploy cargo.

Practically 70 years after its creation, this outstanding invention, with its distinctive but purposeful “wobble,” continues to be discovered throughout various fields. From exact surgical actions to the exploration of distant planets, the Harmonic Drive’s genius lies in its simplicity, reliability, and precision.

Supply: Harmonic Drive