3 ms·

Have you practiced control theory in an actual process plant? PID is not simple to tune it at all, well PI, nobody uses the derivative part. Countless studies

Have you practiced control theory in an actual process plant? PID is not simple to tune it at all, well PI, nobody uses the derivative part. Countless studies published in the industry show that up to 30% of the PID control loops in operation are set to MANUAL by the operators and from the rest more than half have wrong parameters.Even then +90% of the controllers are PID, because despite all their problems they work better than the more sophisticated alternatives, they are more reliable, maintainable and cheaper to license. > PID will basically have you experience either large overshoots (which you will experience as overcorrecting to changes in demand) or slow adaptation to changes. Such a blanket statement is meaningless without a description of the system you are controlling, those kind of overshoot can be attributed to wrong parameters, to badly sized elements of control or even to bad measuring devices, the PID algorithm has zero to do with those cases. > I have implemented a controller for espresso machine boiler water temperature. Replacing PID with moving horizon estimator allowed me to cut time from startup until stable temperature by at least half and eliminate any measurable over or undershoots. Did you try a "bang-bang" controller,I would no be surprised if you'd get the same results with 1% of the complexity.

lmilcin 5y ago
The problem with espresso machine startup is that there is 1.5kg piece of metal (grouphead) through which flows around 60ml of water from the boiler. What do you think is the relation between boiler water temperature and the water that actually reaches coffee? When the machine starts, the grouphead is cold. If you want to get good brewing temperature you need to, either a) Wait for 40 minutes until grouphead heats up slowly and everything stabilizes b) Heat up water for 10 minutes and then pump a lot of water through the grouphead to get it hot from the water and pray everything works well c) Build a model that will predict correct setting of water in the boiler given predicted temperature of the grouphead so that when you push water through the grouphead it cools just the right amount. Unfortunately, the correct brew temperature is 92C so you only have couple of degrees to work with. But, still, heating the water to higher temperature causes grouphead to heat up faster and you don't need to heat it as much because it will receive hotter water. Commercial machines do not have this problem because they are started in the morning and only turned off for the night and they have huge tanks of brewing water in them so inflowing water does not affect the temperature so much.

lmilcin 5y ago

The problem with espresso machine startup is that there is 1.5kg piece of metal (grouphead) through which flows around 60ml of water from the boiler. What do you think is the relation between boiler water temperature and the water that actually reaches coffee? When the machine starts, the grouphead is cold. If you want to get good brewing temperature you need to, either a) Wait for 40 minutes until grouphead heats up slowly and everything stabilizes b) Heat up water for 10 minutes and then pump a lot of water through the grouphead to get it hot from the water and pray everything works well c) Build a model that will predict correct setting of water in the boiler given predicted temperature of the grouphead so that when you push water through the grouphead it cools just the right amount. Unfortunately, the correct brew temperature is 92C so you only have couple of degrees to work with. But, still, heating the water to higher temperature causes grouphead to heat up faster and you don't need to heat it as much because it will receive hotter water. Commercial machines do not have this problem because they are started in the morning and only turned off for the night and they have huge tanks of brewing water in them so inflowing water does not affect the temperature so much.