LSIS Master-K K200S - D Control; Pseudo Code of PID Control

Chapter 15 The PID function of K200S MASTER-K
15-14
15.3.3 D control
The continuous formula of derivative term is as following;
dt
dy
KTdDD
dt
d
N
Td
−=+×
N : high frequency noise depression ration
y : the object to be controlled (PV)
The digitized formula is as following (Use Tustin approximation method)
[ ] )1()(
2
2
)1(
2
2
)( −−
+
−−
+
−
= nyny
hN
Td
KTdN
nD
hN
Td
hNTd
nD
15.3.4 Pseudo code of PID control
The pseudo code of PID control is as following;
Step 1 : Get constants that are used for PID operation
Ti
h
KBi ×= : integral gain
)2(
)2(
hNTd
hNTd
Ad
×+×
×
−
×
=
: derivation gain
)2(
)2(
hNTd
TdNK
Bd
×+×
×
×
×
=
Tt
h
A =0 : anti-windup gain
Step 2 : Read SV and PV value
PV = adin(ch1)
Step 3: Calculate the proportional term.
P = K × (b × SV – PV)
Step 4 : Update the derivative term. (initial value of D = 0)
D = As × D – Bd × (PV – PV_old)
Step 5 : Calculate the MV. (initial value of I = 0)
MV = P + I + D
Step 6 : Check the actuator is saturated or not.
U = sat(MV, U_low, U_high)
Step 7 : Output the MV value to the D/A module
Step 8 : Update the integral term.
I = I + bi × (SV – PV) + A0 × (U – MV)
Step 9 : Update the PV_old value.
PV_old = PV