Temperature control, inertia.

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Temperature control, inertia.

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eliezeroc
Contributor III

Hello everyone. I'm working on a temperature control project that prescisa to be very stable. I'm having trouble with inertia.

Does anyone know of any control algorithm to help me?

I'm working with PT60. I tried to implement a PID control but could not.

Thanks.

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kef2
Senior Contributor IV

PID is right way to go. "Trouble with inertia" sounds like anti-windup is not implemented. What happens without anti-windup:

Real world actuator always has limited range, for example PWM duty settings from 0 to 100. But I-term of PID, due to slow rise/fall of temperature, may quickly accumulate and make PID asking actuator  to throttle to 1000, 10000 or 1E10 for example, instead of available only 100... After temperature crosses target temperature value, I-term starts falling, but it will take quite long until it falls to negative I-term values. And T keeps rising, temperature oscillates wildly...

What you can do to fix problem? For example, when PID gives out of range actuator value, set I-integral to value, which would make PID formula pointing to margin actuator value.

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kef2
Senior Contributor IV

PID is right way to go. "Trouble with inertia" sounds like anti-windup is not implemented. What happens without anti-windup:

Real world actuator always has limited range, for example PWM duty settings from 0 to 100. But I-term of PID, due to slow rise/fall of temperature, may quickly accumulate and make PID asking actuator  to throttle to 1000, 10000 or 1E10 for example, instead of available only 100... After temperature crosses target temperature value, I-term starts falling, but it will take quite long until it falls to negative I-term values. And T keeps rising, temperature oscillates wildly...

What you can do to fix problem? For example, when PID gives out of range actuator value, set I-integral to value, which would make PID formula pointing to margin actuator value.

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