70
1018856
08/2018 V04
Torsional stiffness
(Harmonic Drive® Gears) K
1
, K
2
, K
3
[Nm/rad]
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
1
, K
2
and K
3
are determined by linearization of the curve.
K
1
: low torque region
0 ~ T
1
K
2
: middle torque region T
1
~ T
2
K
3
: high torque region
> T
3
The values given for the torsional stiffness K
1
, K
2
and K
3
are
average values that have been determined during numerous
tests. The limit torques T
1
and T
2
and an calculation example
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
3
[Nm/rad]
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 catalog is the net weight without packing and only applies to standard versions.
K
1
K
2
K
3
0
T
2
Torsion
φ
φ
2
φ
1
T
1
Torque T
K
1
, K
2
, K
3
= Torsional stiffness, w = Output angle
φ
1 = Torsion angle, with output torque T
1
φ
2 = Torsion angle, with output torque T
2
T
N
= Rated torque
φ
= Output angle
A
ccur
ac
y
Tr
ansmission
accur
ac
y
360° Output
angle
