Mitsubishi Electronics FR-A700 Manuel D’Utilisation
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4.6.4
Setting of the electronic gear (Pr. 420, Pr. 421, Pr. 424)
(1) Calculation of the gear ratio (Pr. 420, Pr. 421)
⋅ The position resolution (travel per pulse Δ [mm]) is determined by the travel per motor revolution Δs [mm] and the
feedback pulses Pf [pulse/rev] of the detector, and is represented by the following expression.
Using the parameters, the travel per command pulse can be set separately to set the travel per command pulse
without a fraction.
without a fraction.
In addition, the relationship between the motor speed and internal command pulse frequency is as follows:
Set the ratio of the machine side gear and the motor side gear.
Parameter
Number
Name
Initial Value
Setting
Range
Description
420
Command pulse scaling
factor numerator
factor numerator
1
0 to 32767 *
Set the electric gear.
Pr. 420 is a numerator and Pr. 421 is a denominator.
Pr. 420 is a numerator and Pr. 421 is a denominator.
421
Command pulse scaling
factor denominator
factor denominator
1
0 to 32767 *
424
Position command
acceleration/deceleration
time constant
acceleration/deceleration
time constant
0s
0 to 50s
Used when rotation has become unsmooth at a
large electronic gear ratio (about 10 times or more)
and low speed.
large electronic gear ratio (about 10 times or more)
and low speed.
The above parameters can be set when the FR-A7AP/FR-A7AL (option) is mounted.
*
*
When the operation panel (FR-DU07) is used, the maximum setting is 9999. When a parameter unit is used, up to the maximum value within
the setting range can be set.
the setting range can be set.
Δ :travel per pulse [mm]
Δs: travel per motor rotation [mm]
Pf: number of feedback pulses [pulse/rev] (number of pulses after multiplying the number of
Δs: travel per motor rotation [mm]
Pf: number of feedback pulses [pulse/rev] (number of pulses after multiplying the number of
encoder pulses by four)
Δ
=
Δs
Pf
Δ
=
Δs
×
Pr. 420
Pf
Pr. 421
fo
×
Pr. 420
= Pf
×
No
fo : Internal command pulse frequency [pps]
Motor speed [r/min]
Pr. 421
60
No :
CAUTION
Set the electronic gear in the range of 1/50 to 20.
Note that too small a value will decrease the speed command and too large a value will increase the speed ripples.
Note that too small a value will decrease the speed command and too large a value will increase the speed ripples.
[Setting example 1]
The electronic gear ratio is
The electronic gear ratio is
Δs = 10 (mm) when the travel per pulse Δ = 0.01 (mm) and the number of feedback
pulses Pf = 4000 (pulse/rev) in a drive system where the ballscrew pitch PB = 10 (mm) and the reduction ratio 1/n = 1.
According to the following expression,
According to the following expression,
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
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),
Therefore, the internal command pulse frequency is 204800 (pps).
Vector
Vector
Vector
Δ
=
Δs
×
Pr. 420
Pf
Pr. 421
Pr. 420
= Δ
×
Pf
Pr. 421
Δs
= 0.01
×
4000
=
4
10
1
fo
= 2048
×
4
(multiplication)
×
No
×
Pr. 421
60
Pr. 420
= 204800