Red-lion PCU Manuel d'utilisateur télécharger pdf (Page 85)

CLOSED LOOP CYCLING METHOD

Analternativetoauto-tuningismanualtuning.Thistuningmethodinduces

oscillations into the process in the same way as the controller’s auto-tune

function. If oscillations are not acceptable, the open-loop tuning method can

be used.

The following is a manual tuning procedure for determination of the PID

control constants.

1. Connect a chart recorder to log process value and set the paper speed

appropriate for the process.

2. Set the controller to automatic (auto) control mode.

3. Set proportional band to 999.9%. (maximum setting)

4. Set integral time and derivative time to 0 seconds.

5. Decrease proportional band (increase controller gain) by factors of two

until process just begins to oscillate and the oscillations are sustained.

Make a small change in setpoint to provide a stimulus for oscillations.

Allow adequate time for the process to respond. If oscillations appear to

grow, increase proportional band. Adjust the proportional band until

steady oscillations appear.

6. Note the peak-to-peak amplitude of the cycle (a) in degrees and the period

of oscillation (t) in seconds.

Parameter Fast Response

Damped

Response

Slow

Response

Proportional Band (%) 200a/range 400a/range 600a/range

Integral Time (sec) 1t 2t 3t

Derivative Time (sec) 0.2t 0.25t 0.25t

Output Power

Dampening (sec)

t/40 t/30 t/20

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Figure 42, Closed Loop Tuning

1 2 ... 80 81 82 83 84 85 86 87 88 89 90 ... 95 96

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Red-lion PCU Manuel d'utilisateur Page 85