What you learn today
- Compare hysteresis and PI controller
- Connect gas control and airlock
- Spot gaps
Month 6 taught you three ways of controlling, plus gases, heat and the airlock. Today you put them in order – and connect two of them in one chip.
Comparing hysteresis and PI controller
| Hysteresis | P controller | PI controller | |
|---|---|---|---|
| Actuator | only on/off (heater, valve) | stepless (pump, mixer) | stepless |
| Behaviour | swings in the band | gets close, stays slightly off | reaches the target exactly |
| Effort | 4 lines | 3–4 lines | plus integral and anti-windup |
| Trap | comparisons swapped | steady-state error | windup, NaN in the integral |
For most base tasks hysteresis is enough. A P term pays off where a device works steplessly and should arrive gently – such as a pump filling a chamber.
Connecting gas control and airlock
An airlock that fills from a supply tank has to answer two questions: may I fill? And how fast?
- May: the supply has enough pressure and breathable air (gas share as in week 22).
- How fast: P term as in week 23 – far from the target full pump, close to it slowly.
sub out FULL press
mul out out KP
clamp out out 0 PMAX
mul out out ok # 0 without releasemul with a 0/1 value is a release without a jump.
Spotting gaps
- Why does a pure P controller never quite reach the target? (day 155)
- What does anti-windup do, and why with
clamp? (day 156) - What happens to the air conditioner when its Setting is above the inlet temperature? (day 162)
- Which door may open at 50 kPa in the chamber? (none, week 25)
- When is “keep running” the safe direction? (day 151)
clamp with NaN returns NaN. If the chamber sensor fails, the pump's Setting would be NaN – hence the snan and select after the clamp. Comparisons catch NaN by themselves, calculations do not.
Read KP from the span: if the pump should run fully at 50 kPa distance (Setting 10), KP = 10 / 50 = 0.2.
Exercise
Task
The volume pump “Fuellpumpe” fills the airlock (sensor “Schleuse”) from the supply (analyzer “Vorrat”).
- Release only with at least 300 kPa and at least 18 % oxygen in the supply, otherwise flashing light “Vorrat” on
- Setting = 0.2 · (100 kPa − chamber pressure), limited to 0 … 10, 0 without release
Ononly while the Setting is above 0- Chamber sensor gone: pump off
Hints
Hint 1
Release: two sge and one and.
Hint 2
Output: sub, mul with KP, clamp to 0 … PMAX, then replace NaN with 0 and multiply by ok.
Hint 3
On = sgtz of the output.
Quiz
4 questions. You pass from 60 % – the server does the grading.
Complete the day
- Passed the simulator exercise
- Passed the quiz with at least 60 %
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