Harmonic Drive SHG Series Manual page 67

Torsional stiffness
(Harmonic Drive® Gears) K
The amount of elastic rotation at the output for a given
torque with the Wave Generator blocked. The torsional stiff-
ness may be evaluated by dividing the torque-torsion curve
into three regions. The torsional stiffness values K
are determined by linearization of the curve.
K : low torque region
1
K : middle torque region
2
K : high torque region
3
The values given for the torsional stiffness K
average values that have been determined during numerous
tests. The limit torques T and T
1
for the torsional angle can be found in chapter "torsional
stiffness" and "calculation of the torsion angle" of this
documentation.
Torsional stiffness
(Harmonic Planetary Gears) K
The amount of elastic rotation at the output for a given
torque and blocked input shaft. The torsional rigidity of the
Harmonic Planetary Gear describes the rotation of the gear
above a reference torque of 15 % of the rated torque. In this
area the torsional stiffness is almost linear.
Transmission accuracy [arcmin]
The transmission accuracy of the gear represents the linear-
ity error between input and output angle. The transmission
accuracy is measured for one complete output revolution
using a high resolution measurement system. The measure-
ments are carried out without direction reversal. The trans-
mission accuracy is defined as the sum of the maximum
positive and negative differences between the theoretical
and actual output rotation angles.
Weight m [kg]
The weight specified in the catalogue is the net weight without packing and only applies to standard versions.
1021387 12/2018 V02
, K , K [Nm/rad]
1 2 3
, K and K
1 2
0 ~ T
1
T ~ T
1 2
> T
3
, K and K
1 2 3
and an calculation example
2
[Nm/rad]
3
Torsion
φ
φ2
3
K
φ1
0
K , K , K = Torsional stiffness, w = Output angle
1 2 3
φ1 = Torsion angle, with output torque T
φ2 = Torsion angle, with output torque T
are
K
3
K
2
1
Torque T
T T
2
1
1
2
T = Rated torque
N
φ = Output angle
360° Output
angle
67