Omron trajexia CJ1W-MCH72 Operation Manual page 25

Servo system principles
1-4-3 Motion control algorithm
14
The servo system controls the motor by continuously adjusting the speed
reference to the Servo Driver. The speed reference is calculated by the motion
control algorithm of the CJ1W-MCH72, which is explained in this section.
A
The motion control algorithm uses the demand position (A), the measured
position (D) and the Following Error (B) to determine the speed reference. The
Following Error is the difference between the demanded and measured
position. The demand position, the measured position and the Following Error
are represented by the axis parameters MPOS, DPOS and FE. Five gain
values have been implemented for the user to be able to configure the correct
control operation for each application.
C is the output signal.
• Proportional gain
The proportional gain K
Following Error E.
O = K · E
p p
All practical systems use proportional gain. For many just using this gain
parameter alone is sufficient. The proportional gain axis parameter is called
P_GAIN.
• Integral gain
The integral gain K
the Following Errors that have occurred during the system operation.
O = K · ΣE
i i
Integral gain can cause overshoot and so is usually used only on systems
working at constant speed or with slow accelerations. The integral gain axis
parameter is called I_GAIN.
• Derivative gain
The derivative gain K
change in the Following Error E and speeds up the response to changes in
error while maintaining the same relative stability.
O = K · ∆E
d d
Derivative gain may create a smoother response. High values may lead to
oscillation. The derivative gain axis parameter is called D_GAIN.
• Output speed gain
The output speed gain K
the change in the measured position P
O = K · ∆P
ov ov m
K
p
B
∑
K
i
∆
K
d
creates an output O
p
creates an output O
i i
produces an output O
d
produces an output O
ov
and increases system damping.
m
Section 1-4
∑
K
vff
C
∆
K
ov
D
that is proportional to the
p
that is proportional to the sum of
that is proportional to the
d
that is proportional to
ov