Step Response Method - Mitsubishi Electric MELSEC iQ-F FX5 User Manual

Step Response Method

For acquiring satisfactory control results during PID control, it is necessary to obtain the optimal value of each constant
(parameter) suitable for the control target. This paragraph explains the step response method to obtain three constants in the
PID control (proportional gain (KP), integral time (TI) and differential time (TD)).
In this method, by giving stepped output from 0 to 100 % to the control system, three constants in the PID control are obtained
from the operation characteristics (maximum ramp (R) and dead time (L)) and the input value variation. The stepped output
may be obtained from 0 to 75% or from 0 to 50 %.
How to obtain three constants in PID control (Reference)
■Operation characteristics and three constants
Control type
Only proportional control (P
operation)
PI control (PI operation)
PID control (PID operation)
■Operation characteristics
100 %
Output value (MV)
0 %
Input value variation
Parameters set in step response method
The parameters specified in the step response method are shown below.
Parameter
Operation setting (ACT)
Proportional gain (KP)
Integral time (TI)
Differential time (TD)
Proportional gain (KP) [%]
Output value
1
× ×100
(MV)
RL
Output value
0.9
× ×100
(MV)
RL
Output value
1.2
× ×100
RL (MV)
Output value (MV)
Maximum ramp (R)
1 (s)
Dead time (L) [s]
Integral time (TI) [ 100 ms]

33L
20L
Time
Time (s)
Setting position
(s3)+1: b0 (operation direction)
(s3)+3
(s3)+4
(s3)+6
Differential time (TD) [ 10 ms]


50L
9 PID CONTROL FUNCTION
9.7 Auto-Tuning
9
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