Mitsubishi Electric Melsec FX Series Beginners Manual page 20

The Basics of Positioning Control
● The moving part continues by a coasting distance until it completely stops, after the stop
command is given. The coasting distance is not controlled and it is represented as the shaded
part in the figure below.
Speed
● Dispersion in the stop distance changes as shown below. Dispersion is affected by the speed of
the workpiece when the stop command is given and the speed reduction time delay after stop.
Speed
● If the required stop precision is not satisfactory when stopping from the normal operation speed,
the most effective method to improve the stop precision is to reduce the operation speed.
However, if the operation speed is simply reduced, the machine efficiency may also be reduced.
Therefore, in actual operation, the motor speed can be reduced from a high speed to a low speed
before the motor is stopped, as shown below.
Speed
Fig. 1-12: Positioning pattern
1 - 8
Stop command
Speed recuction start
Time delay
Stop
Stop
Stop
command
Time delay
High speed
Poor stop
precision
Stop
Stop
command
Fig. 1-10: Positioning pattern
Coasting
distance
Time
Stop
Fig. 1-11: Positioning pattern
Dispersion in
stop
Time
Speed
High speed
Time
Speed reduction
command
Positioning method type
1200b0da.eps
1200c0da.eps
Improved stop
Low
precision
speed
Time
Stop
Stop command
1200d0da.eps
MITSUBISHI ELECTRIC