Harmonic Drive FHA Mini Series, Manual

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Chapter 1 Overview of the FHA-C mini series
FHA-C mini
14
Incremental encoder
Model
Item
FHA-8C
FHA-11C
FHA-14C
-30 -50 -100
Encoder resolution
2,000 (8,000 pulse/rev: quadruplicate)
Reduction ratio
30 50 100
Detector resolution
(quadruplicate)
Pulse/rev
240,000 400,000 800,000
Resolvable angle per
pulse (approximate
value)
Sec.
5.40 3.24 1.62
Absolute encoder
Model
Item
FHA-8C
FHA-11C
FHA-14C
-30 -50 -100
Encoder resolution
2
17
(131,072 pulse/rev)
Reduction ratio
30 50 100
Detector resolution
(quadruplicate)
Pulse/rev
3,932,160 6,553,600 13,107,200
Resolvable angle per
pulse (approximate
value)
Sec.
Approx. 0.33 Approx. 0.2 Approx. 0.1
1-7 One-way positioning accuracy
The one-way positioning accuracy is defined as the maximum
positional difference between thecommanded position and the
actual stop position when a series of positioning moves are per-
formed inthe same rotation direction. (Refer to JIS B-6201-1987).
The FHA mini actuator incorporates a Harmonic Drive gear which
inherently has high rotational position accuracy. Because of the
gearing's high ratio, any rotational error at the input (i.e. motor shaft
position error or motor feedback error) is reduced by a factor of the
ratio (1/ratio) and typically becomes negligibleat the output.
Therefore most of the error is represented by the transmission error
of the Harmonic Drive gear itself.
The one-way positioning accuracy is shown in the table below:
Model
Item
FHA-8C FHA-11C FHA-14C
-30 -50 -100 -30 -50 -100 -30 -50 -100
One-way positioning
accuracy
arc second 150
120
120 120 90 90 120 90 90
●
Angle offset function for a horizontally installed actuator
The drivers for FHA-C mini series actuators (FHA-8C/11C/14C) provide an angle offset function to
improve angular positioning accuracy of a horizontally installed actuator. The function offsets against a
position error by a pre-analyzed positioning error of the Harmonic Drive
®
components to improve a one-
way positioning accuracy by around 30% better than an accuracy without the angle offset function. For
fluctuant load, test and examine whether the function is effective before applying it.
Refer to the driver manual.
1-8 Encoder resolution
The motors of FHA-C mini actuators are equipped with an incremental encoder of 2000 resolutions.
Because the motor rotation is reduced to 30:1 or 50:1 or 100:1 by the Harmonic Drive® component, the
resolution of the output flange is 30 or 50 or 100 times the encoder revolution. Additionally, the
incremental encoder signal is used in quadrature.
The following high resolutions are obtained: