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Lecture 8-Harmonic Drive)

Harmonic drives use three basic parts - a wave generator, flexspline, and circular spline - to achieve precise motion control with benefits like zero backlash, high torque, and a compact size. The flexspline and circular spline engage teeth to reduce the speed of the flexspline relative to the wave generator's input. Reduction ratios are determined by the number of teeth and can range from 30:1 to 320:1 in a small volume. Harmonic drives provide advantages such as no backlash, light weight, configurable gear ratios, and high torque capability.

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Kshatriya Kumar
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141 views9 pages

Lecture 8-Harmonic Drive)

Harmonic drives use three basic parts - a wave generator, flexspline, and circular spline - to achieve precise motion control with benefits like zero backlash, high torque, and a compact size. The flexspline and circular spline engage teeth to reduce the speed of the flexspline relative to the wave generator's input. Reduction ratios are determined by the number of teeth and can range from 30:1 to 320:1 in a small volume. Harmonic drives provide advantages such as no backlash, light weight, configurable gear ratios, and high torque capability.

Uploaded by

Kshatriya Kumar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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15MH301-Fundamentals of Robotics

Day-2,Hr-1,2

RANJITH PILLAI R
Assistant Professor
Department of Mechatronics Engineering
SRM Institute of Science and Technology
ranjithpillai.r@ktr.srmuniv.ac.in
https://sites.google.com/site/ranjithpillaimechatronics/
Motion Analysis Lab
1 Department of Mechatronics Engg. 02/07/2019
Contents
} Harmonic Drives
} Use

} Parts

} Working

} Reduction Ratio

} Advantage
Harmonic drives
} Principle based upon the elastic mechanics of metals
} Benefits- zero backlash ,characteristics and the weight
and space savings compared to other gears.
} Only 3 basic parts for precise motion control- Wave
Generator, Flexspline and Circular Spline
} Zero backlash, high torque, compact size, excellent
positional accuracy and repeatability with high reduction
ratio

3 Department of Mechatronics Engg. 26/09/2018


Three components of harmonic drives

4 Department of Mechatronics Engg. 26/09/2018


Wave generator
} Comprises of a specially designed thin raced ball bearing
that is fitted onto an elliptical hub

} Torque converter

} Input of the gear and connected

to input of motor shaft

5 Department of Mechatronics Engg. 26/09/2018


Flex spline
} Thin cylindrical cup made from

alloy steel with external teeth on

the open end of the cup

} Radially compliant

} When the Wave Generator in inserted into the Flexspline


the gear takes on its elliptical shape

} Output and is connected to the output flange.

6 Department of Mechatronics Engg. 26/09/2018


Circular Spline
} The Circular Spline is a rigid ring with internal teeth

} When assembled it engages the teeth

of the Flexspline across the major axis

of the Wave Generator ellipse.

} The Circular Spline has two more teeth than the


Flexspline and is fixed to the gear housing

7 Department of Mechatronics Engg. 26/09/2018


} if there are 202 teeth on the circular spline and 200 on the flex
spline, the reduction ratio is (200 − 202)/200 = −0.01
} Thus the flex spline spins at 1/100 the speed of the wave generator
plug and in the opposite direction. Different reduction ratios are set
by changing the number of teeth. This can either be achieved by
changing the mechanism's diameter or by changing the size of the
individual teeth and thereby preserving its size and weight

8 Department of Mechatronics Engg. 26/09/2018


} The advantages include: no backlash, high compactness and
light weight, high gear ratios, reconfigurable ratios within a
standard housing, good resolution and excellent repeatability
(linear representation) when repositioning inertial loads,high
torque capability, and coaxial input and output shafts.

} High gear reduction ratios are possible in a small volume (a


ratio from 30:1 up to 320:1 is possible in the same space in
which planetary gears typically only produce a 10:1 ratio).

9 Department of Mechatronics Engg. 26/09/2018

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