System philosophy
HARDWARE REFERENCE MANUAL
22
Revision 5.0
F. Speed control.
G. Motor.
H. Encoder.
I.
Measured speed.
J. Measured position.
2.3.3
Position loop algorithm in the CPU
The servo system controls the motor by continuously adjusting the speed
reference to the Servo Drive. The speed reference is calculated by the
motion control algorithm of the TJ2-MC__, which is explained in this section.
fig. 16
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
p
creates an output
O
p
that is proportional to the
Following Error E.
O
p
= K
p
· E
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
i
creates an output
O
i
that is proportional to the sum
of the Following Errors that have occurred during the system operation.
O
i
= K
i
·
Ó
E
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
d
produces an output
O
d
that is proportional to the
change in the Following Error
E
and speeds up the response to changes
in error while maintaining the same relative stability.
A
B
C
D
å
å
K
p
K
i
K
d
K
vff
K
ov
Δ
Δ
