High Country Tek DRF Series - Manual (Page 13)

021-DRF Rev A DRF User Manual 13
Copyright © High Country Tek, Inc. – 2013
DRF
Closed-loop Valve Controller
PID Algorithm
The controller uses a digital, velocity PID algorithm as shown:
O(t) = O(t-1) + P*(e(t)-e(t-1)) + I*T*e(t) + D/T*(e(t) + e(t-2) – 2*e(t-1))
Where:
O = output
P = proportional gain term
I = integral gain term
D = derivative gain term
e(t) = error at time t
T = PID loop time
Setup Procedure
1. Select the operating frequency.
2. Set the Minimum and Maximum Outputs according to the valve specs.
3. Set the Dither Frequency according to the valve specs. Higher dither frequencies can improve frequency
response.
4. Start with Proportional only to achieve a stable system.
5. Add Integral.
6. Add Derivative to improve system response and/or stability.