4.
Parameters
4-67
(2)
Electronic Gear Ratio [P4-01] ~ [P4-08]
The electronic gear ratio is the numerator/denominator form of the relation between the
position command input pulse and the motor encoder pulse. It is important to set the ratio so
that there is no error during position operation. The following describes how to set it:
* Electronic gear ratio = transmission per input pulse x number of pulses per motor rotation /
transmission per motor rotation
e.g.) If deceleration ratio is 1/2, ball screw lead is 10 [
㎜
], and encoder pulse is 3000 in the
unit of commands that control each pulse in 1 [
㎛
].
1.
Transmission per input pulse = 1 × 10 - 3 = 0.001 [
㎜
]
2.
Number of pulses per motor rotation = number of encoder pulses × 4 = 3000 × 4 = 12000
3.
Transmission per motor rotation = 10 × 1/2 = 5 [
㎜
]
4.
Electronic gear ratio = 12000 × 10 - 3/5 = 12/5
Therefore, the numerator and denominator of electronic gear ratio are 12 and 5 respectively.
NOTE 1)
There are 12,000 pulses per rotation for a 3,000-pulse encoder because the servo drive controls
pulses by multiplying them by four in quadrature type encoder signals.
In this case, motor speed ([RPM]) is calculated as follows:
Motor speed = 60 × electronic gear ratio × input pulse frequency / number of pulses per
motor rotation
The following is how to calculate error pulse [St-05], the difference between command pulse and tracking
pulse during operation. Error pulse = command pulse frequency × electronic gear ratio × {1 -
(0.01 × [P1-05])} / [P1-01]
In the case of serial type encoder, It is 523288 pulses per 1 rotation without X4.
(3)
Backlash Compensation [P4-13]
Sets backlash compensation by converting the amount of backlashes into the number of
pulses if the position changes because of backlashes caused by position operation. If the
travel range per rotation is changed because of abrasion of machine. You can use is by
adjusting off-set variation volume caused by abrasion
(4)
Electronic Gear Ratio Offset Adjustment: For reasons of wear
and tear on the machine during position pulse command
operation
If the operation distance per rotation changes, you can adjust the change caused by wear
and tear with offset.
Electronic gear ratio setting mode [P4-09]
0: Use electronic gear ratio 1~4.
1: Use electronic gear ratio 1. Override the value on the electronic gear ratio numerator.
Electronic gear ratio numerator offset setting
In the above example, if you enter 12,000 for the numerator and 5,000 for the denominator and turn
on the EGEAR1 contact point, the numerator increases by one. If you turn on the EGEAR2 contact,
the numerator decreases by one. The change is saved in the [P4-10] parameter.