Electronic Gear Settings - Mitsubishi Electric 800 Series Instruction Manual (Function

7.5

Electronic gear settings

Vector Vector Vector
Set the gear ratio between the machine gear and motor gear.
Pr. Name
Command pulse scaling factor
420
numerator (electronic gear
B001
numerator)
Command pulse multiplication
421
denominator (electronic gear
B002
denominator)
 Gear ratio calculation (Pr.420, Pr.421)
The position resolution (travel distance per pulse Δ [mm]) is the travel distance per motor rotation Δs [mm] and the feedback
pulse Pf [pulses/rev] of the detector.
Δ : Travel distance per pulse [mm]
Δs
Δ Δs: Travel distance in one motor rotation [mm]
＝
Pf
pf: Number of feedback pulses [pulse/rev] (the number of pulses after the number encoder
pulses is quadruplicated)
The travel distance in 1 command pulse can be separately specified with a parameter and so an integer can be set as the travel
distance in 1 command pulse.
The following formula shows the relationship between the motor speed and internal command pulse frequency.
fo ×
NOTE
• The setting of 1/900 or lower is limited at 1/900, and 900 or higher at 900.
Setting example
To set the travel distance per pulse to 0.01 mm in a machine with ?s
= 10 mm while a motor with a 1024 pulse encoder is used.
Δ
=
Pr.420
Δ ×
=
Pr.421
= 0.01 ×
Thus, set the parameters as follows: Pr.420 = "512", Pr.421 = "125".
 Relationship between the position resolution and system accuracy
The system accuracy (the positioning accuracy of the machine) is the sum of electric deviation and mechanical deviation.
Normally try to prevent the total deviation from being affected by the electronic deviation. Refer to the following relationship as
a reference.
Δ
Initial value
1
1
＝
Δ
Pr.420 No
= Pf ×
Pr.421 60
Δs
Pr.420
×
Pf Pr.421
Pf
Δs
4000 4
=
10 1
1 1
) × Δε
< ( to
5 10
Setting
range
1 to 32767
Set the electronic gear. The gear ratio range is from 1/900 to
900.
Pr.420 is the numerator and Pr.421 is the denominator.
1 to 32767
Δs Pr.420
×
Pf Pr.421
fo: internal command pulse frequency [pulses/s]
No: motor rotation speed [r/min]
Δε: positioning accuracy
Description
7. Position Control
7.5 Electronic gear settings
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