1-8 One-Way Positional accuracy
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1-8
One-Way Positional accuracy
The one-way positioning accuracy is defined as the maximum positional difference between the
commanded position and the actual stop position when a series of positioning moves are performed
in the same rotation direction. (Refer to JIS B-6201-1987).
The SHA 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 negligible at the output.
Therefore most of the error is represented by the transmission error of the Harmonic Drive gear itself.
The one-way positional accuracy is shown in the table below:
SG/HP
（
Unit: arc-sec
）
Size
Reduction ratio
SHA20A
SHA 25A
SHA32A
SHA40A
SHA58A
SHA65A
11:1
－
120
120
－
－
－
51:1
60
50
50
50
－
－
81:1 or more
50
40
40
40
40
40
CG
(Unit: arc-sec)
Size
Reduction ratio
SHA20A
SHA25A
SHA32A
SHA40A
50:1
60
50
40
40
80:1 or more
50
40
30
30
