Inovance H3U Series - Page 311

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4
4 Instructions4.12.1 PID Calculation
2) Principle of position-type PID calculation
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PID calculation formula:
u(k) = Kp x e(k) + Ki x T x ∑e(i) + (Kd/T) x [Pv(k) – Pv(k-1)]
u(k)
Current output
value
Pv(k-1)
Feedback value
at the last time
point
e(k) Current deviation T Sampling time
∑e(i)
Current
cumulative
integral
Kp Proportional gain
Sv(k) Current value Ki Integral gain
Pv(k)
Current feedback
value
Kd Differential gain
Forward direction: e(k) = Sv(k) – Pv(k)
Reverse direction: e(k) = Pv(k) – Sv(k)
3) Principle of parameter switching (proportional gain Kp used an as example)
Kp
E
0
Kp1
Kp2
E1
E2
Kp1 (S3 + 2)
Kp2 (S3 + 13)
E1 (S3 + 17)
E2 (S3 + 18)
E Switching reference
When E ≤ E1, Kp = Kp1.
When E1 < E < E2, Kp = (Kp2 – Kp1) x E/(E2 – E1).
When E ≥ E2, Kp = Kp2.
S3 + 16
0 No switching
1 E = |Sv – Pv|
2 E = S3 + 19