Mitsubishi Electronics IB-1500193(ENG)-D ユーザーズマニュアル

4 - 40

The servo control is all closed loop control using the detector's feedback. "Full closed loop control" is the 

system that directly detects the machine position using a linear scale, whereas the general "semi-closed 

loop" is the one that detects the motor position.

In a machine that drives a table with a ball screw, the following factors exist between the motor and 

table end:

[1] Coupling or ball screw table bracket's backlash

[2] Ball screw pitch error

These can adversely affect the accuracy. If the table position is directly detected with a linear scale, 

high-accuracy position control which is not affected by backlash or pitch error is possible. However, with 

the full closed loop system, the machine system is also directly included in the position loop control. 

Thus, if the machine's rigidity is not high, the gain cannot be increased, and the required high accuracy 

cannot be attained.

The procedures for adjusting the servo with the full closed loop system are the same as the semi-closed 

loop system. Vibration or overshooting will occur easily, so the position loop gain is generally lower than 

the semi-closed loop.

With the full closed system, the position feedback (FB) detected with the linear scale is used for the 

position control. However, the motor position FB is detected at the same time, and the error of both FB 

is observed. If this FB error exceeds the servo parameter SV054 setting value, alarm 43 will be detected 

and the system will stop to prevent overrunning due to a scale FB error from occurring.

【#2254】   SV054   ORE   Overrun detection width in closed loop control

Set the overrun detection width in the full-closed loop control. 
When the gap between the motor side detector and the linear scale (machine side detector) exceeds 
the value set by this parameter, it will be judged as overrun and "Alarm 43" will be detected. 
When "-1" is set, the alarm detection will not be performed. 
When "0" is set, overrun will be detected with a 2mm width. 
 
For linear servo/DDM system 
    Not used. Set to "0". 

-1 to 32767 (mm) 

Position 

command 

PGN 

+

-

FB error  

Position droop  

Servo- 

motor  

ENC  

Linear scale  

Table  

Speed command 

Position FB  

Position FB  

+

-