Help: PID tuning for electric actuators
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The actuator flow rate is used as the control condition, but the flow rate varies significantly, resulting in unstable PID regulation (as shown in the figure). By sending a pulse signal to the control valve manually, the instantaneous flow rate of the flow meter increased by four cubic meters of water; under normal conditions it would increase by only one cubic meter. Both the flow meter and the control valve have been replaced – what could be the reason for this? Is there something wrong with the settings of the flow meter?
The trend chart in the lower right corner represents the flow meter with unstable PID control
The PID parameters aren’t tuned well; adjust them gradually
Oscillations are occurring; the proportional or integral action is too strong. Try reducing the proportionality or integration value gradually.
It might be a problem with the flow characteristics of the valve; perhaps the selection wasn’t done properly during the design phase.
First, ensure that when in manual mode, the opening is fixed and the flow rate remains relatively stable; if the flow rate fluctuates greatly, or there is a problem with the actuator’s travel range, automatic mode cannot be activated. Both sensitivity and integration time have a stronger effect the smaller they are; be careful when making adjustments. Integration provides lead control but results in significant lag; adding differentiation helps, as is the case with temperature.
Everything you’ve adjusted is causing oscillation; fortunately it’s an oscillation of constant amplitude. Try reducing the value of P and observe what happens!