Base Functions - Mitsubishi Electric MDS-D-SPJ3 Specification Manual

MITSUBISHI CNC
3 Function Specifications

3-1 Base functions

3-1-1 Full closed loop control
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 of the machine side is directly detected with a
linear scale, high-accuracy position control which is not affected by backlash or pitch error is possible.
Position
command
NC
+
-
Position FB
3-1-2 Position command synchronous control
This is one of the controls which enable two servo motors to drive the same axis. This is also called "Position
tandem control"
The same position command is issued to the 2-axis servo control, and the control is carried out according to
each axis' position and speed feedbacks.
<Features>
(1) The position commands in which machine's mechanical errors (pitch error, backlash, etc.) have
been compensated, can be output to each axis.
(2) Each axis conducts independent position control, therefore the machine posture can be kept
constant.
(3) Deviation between the two axes is always monitored, and if excessive, the alarm is detected.
Program
Same position command
3 - 4
Position Current
command command
PGN VGN
+
+
-
-
Current FB
Speed FB
Full closed loop control
CNC
+
Compen
-sation
-
Compen
-sation
+
-
Voltage
command
Servo
IG
motor
ENC
+
Speed Current
Position
control control
control
-
S
+
Position
Speed Current
control
control control
-
S
Table
Linear scale
The ball screw side
detector is also applied.
Primary axis
M
Detector
Secondary axis
M
Detector