1-9 Rigidity
1-12
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11
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2
3
4
5
6
7
8
9
10
11
Ou
tlin
es
Rotation direction torsional stiffness
If a torque is applied to the output shaft of the actuator with the servo locked, the output shaft
generates a torsional stress roughly in proportion to the torque.
The upper right figure shows the torsional angle of the
output shaft when a torque starting from zero and
increased to positive side [+T
0
] and negative side [–T
0
] is
applied to the output shaft. This is called [torque vs.
torsional angle] diagram, which typically follows a loop
0→A→B→A'→B'→A. The torsional rigidity of the FHA-C
mini series actuator is expressed by the slope of this
[torque vs. torsional angle] diagram representing a spring
constant (unit: N·m/rad).
As shown by lower right figure, this [torque vs. torsional
angle] diagram is divided into 3 regions and the spring
constants in these regions are expressed by K
1
, K
2
, and
K
3
, respectively.
K
1
: Spring constant for torque region 0 to T
1
K
2
: Spring constant for torque region T
1
to T
2
K
3
: Spring constant for torque region over T
2
The torsional angle for each region
is expressed as follows:
Range where torque T is T1 or below:
Range where torque T is T1 to T2:
Range where torque T is T2 or above:
The table below shows the average value of each actuator.
Model
Item
FHA-8C
FHA-11C
FHA-14C
-30
-50
-100
-30
-50
-100
-30
-50
-100
T
1
N·m
0.29
0.29
0.29
0.80
0.80
0.80
2.0
2.0
2.0
kgf·m
0.030
0.030
0.030
0.082
0.082
0.082
0.20
0.20
0.2
K
1
x10
4
N·m/rad
0.034
0.044
0.091
0.084
0.22
0.27
0.19
0.34
0.47
kgf·m/arc min
0.010
0.013
0.027
0.025
0.066
0.080
0.056
0.10
0.14
θ
1
x10
-4
rad
8.5
6.6
3.2
9.5
3.6
3.0
10.5
5.8
4.1
arc min
3.0
2.3
1.1
3.3
1.2
1.0
3.6
2.0
1.4
T
2
N·m
0.75
0.75
0.75
2.0
2.0
2.0
6.9
6.9
6.9
kgf·m
0.077
0.077
0.077
0.20
0.20
0.20
0.70
0.70
0.7
K
2
x10
4
N·m/rad
0.044
0.067
0.10
0.13
0.30
0.34
0.24
0.47
0.61
kgf·m/arc min
0.013
0.020
0.031
0.037
0.090
0.10
0.07
0.14
0.18
θ
2
x10
-4
rad
19
13
8
19
8
6
31
16
12
arc min
6.6
4.7
2.6
6.5
2.6
2.2
10.7
5.6
4.2
K
3
x10
4
N·m/rad
0.054
0.084
0.12
0.16
0.32
0.44
0.34
0.57
0.71
kgf·m/arc min
0.016
0.025
0.036
0.047
0.096
0.13
0.10
0.17
0.21
The table below shows reference torque values calculated for different torsional angles.
(Unit: N·m)
Model
Torsional
angle (arc min)
FHA-8C
FHA-11C
FHA-14C
-30
-50
-100
-30
-50
-100
-30
-50
-100
2
0.20
0.25
0.56
0.49
1.3
1.8
1.1
2.0
3.0
4
0.42
0.63
1.2
1.1
3.3
4.2
2.3
4.7
6.5
6
0.68
1.1
1.9
1.8
5.2
6.8
3.6
7.6
11
3
2
2
K
T
T
−
+
θ
=
ϕ
2
1
1
K
T
T
−
+
θ
=
ϕ
1
K
T
=
ϕ
angle
Torsional
:
*φ
Tor
si
onal
an
gl
e
Hysteresis loss
Torque
0
B’
B
A
+T
0
-T
0
A’
Tor
si
onal
an
gl
e
K
3
K
2
K
1
T
1
T
2
Torque
0
θ
1
θ
2
