Hitachi SJ Series, User Manual

Page: 258 / 786

12-10-3
Chapter 12 Inverter Functions
PID operation
• This section explains of a situation when PID target
value is constant and feedback (FB) value is
changed by using an example.
[1] P operation: P gain Kp
• This is an operation that an operation amount of
PID command value is proportional to the deviation
between PID target value and current feedback
(FB) value.
[2] I operation: I gain Ki (=Ti/Kp)
• This is an operation that an operation amount of
PID command value is proportional to the time
integral value of the deviation between PID target
value and current feedback (FB) value.
• Command operation amount can be adjusted by I
gain.
• Integral value can be cleared by the PIDC terminal
function.
[3] D operation: D gain Kd (=Kp × Td)
• This is an operation that an operation amount of
PID command value is proportional to the change
of the deviation between PID target value and
current feedback (FB) value.
• PI operation is an operation with [1] and [2]
combined.
• PD operation is an operation with [1] and [3]
combined.
• PID operation is an operation with [1], [2] and [3]
combined.
• Command operation amount can be adjusted by P
gain.
• Deviation becomes (PID target value - FB value).
• Because output change becomes smaller as PID
target value and FB value come closer based on an
operation amount and it takes time to reach the
target value in P operation, it is compensated with I
operation.
• Command operation amount can be adjusted by D
gain.
• D operation has an effect to compensate the
responsiveness of P operation and I operation.
When target value changed to above the step When target value changed to above the ramp
When target value changed to above the step When target value changed to above the ramp
When target value changed to above the step When target value changed to above the ramp
PID target value
Operation amount
Large
D gain
Small
FB value
PID target value
Operation amount
Large
Sm
all
FB value
D gain
PID target value
Operation amount
Large
P gain
Sm
FB value
PID target
value
Operation amount
Large
Sm
FB value
P gain
PID target value
Operation amount
Large
I gain
Small
FB value
PID target value
Operation amount
Larg
Small
FB value
I gain