Files
brewpi/components/pid/temp_controller_smith.py
T
jensandClaude Sonnet 4.6 d981c36194 Fix bogus first-tick heatrate from hardcoded last_theta_ist=20
last_theta_ist was hardcoded to 20 in __init__, used to compute the very
first process() tick's heatrate as (theta_ist - 20)/dt*60 - a wildly bogus
spike whenever the real starting temperature wasn't actually 20 (e.g.
1200 deg/min for a 40-degree start). The exponentially-smoothed
heatrate_ist (alpha=0.1) takes several ticks to recover from that, during
which it distorts the PID's rate-error term and visibly throws off the
heating trajectory.

This was invisible everywhere this assumption was implicitly tested,
since ambient (and every start_theta used) was always exactly 20. It
surfaced once SudForecastEstimator.estimate() started being called with a
real, non-20 start_theta: it builds a fresh TempController on every call,
so its first tick always hits this bug fresh - unlike the real controller,
which only ever goes through this once near server startup and has long
since self-corrected (last_theta_ist = theta_ist runs every tick) by the
time any forecast comparison matters. That's exactly what showed up as a
forecast-vs-actual gap during the initial ramp.

last_theta_ist now starts None; process() treats the first tick's
heatrate as 0 (no real history yet) instead of computing it against a
hardcoded, usually-wrong baseline.

Verified: ambient=20 (the only case ever exercised before) is byte-
identical to before the fix. ambient=40/start=40 - reproducing the old
hardcoded-20 behavior side by side - shows the old version visibly lagging
~12 minutes behind the fixed one during the initial ramp before they
converge, matching the reported gap exactly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DkkuG48uHFCGKe6dPSERFk
2026-06-22 22:41:14 +02:00

87 lines
3.3 KiB
Python
Executable File

from components.plant.pot import Pot
from components.pid.temp_controller_base import TempControllerBase, States
class TempController(TempControllerBase):
def __init__(self, dt):
TempControllerBase.__init__(self, dt)
self.dt = dt
# None until the first process() tick - rather than hardcoding a
# starting point (e.g. 20), which would make that very first
# tick's heatrate come out as a bogus spike whenever the real
# starting temperature isn't actually 20 (see
# components/sud_forecast.py's SudForecastEstimator, which builds
# a fresh TempController on every call - unlike the real one,
# which only ever goes through this exactly once, it has no
# earlier ticks to have already settled past that spike by).
self.last_theta_ist = None
self.heatrate_ist = 0
# Fast model: same plant model but with zero transport delay, used
# to predict the current temperature without the dead time.
self.model = Pot(dt)
# Delayed model: keeps the plant's assumed transport delay, so it
# can be compared like-for-like against the real (delayed) measurement.
self.model_delay = Pot(dt)
self.theta_ist_plant = 0
self.theta_ist_model = 0
self.theta_ist_model_delay = 0
def set_model_plant_params(self, model_params):
self.model.set_plant_params({**model_params, 'Td': 0})
self.model_delay.set_plant_params(model_params)
def set_model_power(self, power):
self.model.set_power(power)
self.model_delay.set_power(power)
def set_ambient_temperature(self, theta_amb):
self.model.set_ambient_temperature(theta_amb)
self.model_delay.set_ambient_temperature(theta_amb)
def is_configured(self):
return super().is_configured() and self.model.is_configured() and self.model_delay.is_configured()
def on_state_entered(self, state):
if state in (States.HEAT, States.COOL):
self.model.initial(self.theta_ist)
self.model_delay.initial(self.theta_ist)
def post_pid(self):
self.model.process()
self.model_delay.process()
def process(self):
self._require_params()
if not (self.model.is_configured() and self.model_delay.is_configured()):
raise RuntimeError(
"{}.process(): model plant params and/or ambient temperature not set - "
"call set_model_plant_params() and set_ambient_temperature() first".format(type(self).__name__))
self.theta_ist_plant = self.theta_ist_set
self.theta_ist_model = self.model.get_temperature()
self.theta_ist_model_delay = self.model_delay.get_temperature()
# Smith predictor: use the fast model's prediction, corrected by the
# mismatch between the real (delayed) plant and the delayed model,
# so the dead time drops out of the feedback path.
self.theta_ist = self.theta_ist_model + (self.theta_ist_plant - self.theta_ist_model_delay)
heatrate = 0 if self.last_theta_ist is None else (self.theta_ist - self.last_theta_ist)/self.dt*60
alpha = 0.1
self.heatrate_ist = (1-alpha) * self.heatrate_ist + alpha*heatrate
self.last_theta_ist = self.theta_ist
# Compensate for max heat rate to reduce overshoot
hold_scale = 1.0/self.heatrate_soll_set if self.heatrate_soll_set > 0 else 1.0
self.heatrate_soll = self.heatrate_soll_set * self.pid_hold.get_y()
theta_err = self.theta_soll_set - self.theta_ist
heatrate_err = self.heatrate_soll - self.heatrate_ist
diff = self.theta_soll_set - self.theta_ist
self.process_fsm(diff)
self.process_pid(theta_err, heatrate_err, hold_scale)