Mitsubishi Electric MELSEC iQ-F Series FX5 User Manual page 222

Movement amount per pulse
[Pr.2] No. of pulses per rotation (Ap), [Pr.3] Movement amount per rotation (Al), and [Pr.4] Unit magnification (Am) are the
items for determining how many rotations (equivalent to how many pulses) a motor should operate to move a machine for the
movement amount set in the program.
The drive unit controls the positioning to a motor with the number of pulses.
The following shows the control details of the positioning module.
Positioning module
Command
CPU module,
GX Works3 value
*1 For a drive unit without the electronic gear function, or when the electronic gear function is not used, this value is 1.
Consider a system with a motor connected to a ball screw as shown in the figure above. The electronic gear of the drive unit
is 1.
The movement amount of the machine is in units of mm or inches. Set the command value in units of mm or inches to the
positioning module for the CPU module program.
The motor is controlled by the drive unit in units of pulses. Therefore, since the command value in units of mm or inches is
converted in units of pulses, set Ap, Al, and Am so that the following relational expression is satisfied.
Item
Number of pulses per rotation of motor
Movement amount per rotation of motor
In this case, the machine movement amount for the command 1 pulse output from the positioning module is calculated by the
following calculation formula.
Movement per pulse (A) =
The command frequency from the positioning module is limited. If the command frequency exceeds the upper
limit, increase Movement amount per pulse (A) greater (N times) to decrease the command frequency.
In this case, the electronic gear on the drive unit must be increased by N times as well.
The command pulse from the positioning module is changes to 1/N times. Therefore, multiply it by N on the
drive unit side to keep the number of rotations of the motor.
Because Movement amount per pulse (A) is increased, the position accuracy (command resolution) for the
command 1 pulse from the positioning module decreases.
Consider to decrease the command speed when the position accuracy is required.
12 CONTROL SUB FUNCTION
220
12.3 Function to Compensate Control
Drive unit
Command
pulses
Ap
Al×Am
Rotates the motor in accordance
with the number of pulses
Al × Am
Ap
Electronic
gear
Motor
*1
Reduction gear
Lead
Machinery
Ball screw
Symbol
Ap
Al × Am