Temperature regulation oscillation
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With manual temperature adjustment, neither the temperature nor the valve experiences any fluctuations! With automatic adjustment, both the temperature and the valve behavior start to fluctuate! Is that how it is?
This post was last edited by ylb913 on 2016-5-1 06:53. The ratio should be set higher, so as to prevent the valve from moving too much. Temperature regulation has the greatest lag: when the valve is adjusted a little, the temperature remains unchanged; adjusting it further still doesn’t change the temperature. Only once the temperature at one end starts to change does the temperature easily rise excessively. It also includes increasing the integral value and the differential value.
If the PID parameters are not set properly, re-tune them by first reducing the effect of the proportional or integral terms to observe the trend, and then make adjustments based on those changes. Observe and adjust a few more times...
There’s not much to say about this – it’s a matter of PID tuning; the value of D, which refers to the derivative term, needs to be adjusted. Otherwise, excessive hysteresis can lead to oscillations
From personal experience, if there is a large temperature lag, adjusting only the PID parameters seems ineffective; feedforward control must be used instead
As for what kind of regulation, it’s not certain that it must be PID control. Thermostatic control valve. Give priority to having the process develop a reasonable process plan. Then prescribe the right treatment. There is a reason for the temperature change; what causes it to change? Simple single-loop control is difficult to manage well.
Pay attention to the valve: valves with equal percentage flow characteristics tend to experience smaller temperature fluctuations, while those with linear flow characteristics experience larger fluctuations