Mitsubishi Electric FR-A700 Instruction Manual page 318

Position control by vector control
Examples Setting example 1:
The travel per pulse is Δl = 0.01 mm in a drive system where the ballscrew pitch PB = 10
(mm) and the reduction ratio 1/n = 1 and the electronic gear ratio is Δs = 10 (mm) when the
number of feedback pulses Pf = 4000 (pulse/rev).
According to the following expression,
Δl
=
Pr. 420
------------------ -
Pr. 421
Therefore, set "4" in Pr. 420 and "1" in Pr. 421 .
Setting example 2:
Find the internal command pulse frequency of the dedicated motor rated speed.
Note that the command pulse scaling factor Pr. 420/Pr. 421 = 1.
Assuming that the number of encoder pulses is 2048 (pulses/rev) (feedback pulse Pf = 2048
× 4),
fo
=
=
Therefore, the internal command pulse frequency is 204800 (pps).
Relationship between position resolution Δl and overall accuracy
Since overall accuracy (positioning accuracy of machine) is the sum of electrical error and
mechanical error, normally take measures to prevent the electrical system error from affecting
the overall error. As a guideline, refer to the following relationship.
1
(
Δl <
-- - to
5
Δε: positioning accuracy
6 - 138
Δs
Pr. 420
×
------ - ------------------ -
Pf Pr. 421
Pf
Δl ×
------ -
=
Δs
4000
×
------------ -
= 0.01
10
4
= -- -
1
No Pr. 421
× × ×
2048 4 ------ - ------------------ -
60 Pr. 420
204800
1
)
× Δε
----- -
10
Parameter