mirror of https://github.com/Desuuuu/klipper.git
pid_calibrate: Add some comments on the calibration methodology
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
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@ -75,6 +75,8 @@ class ControlAutoTune:
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self.heater.set_pwm(read_time, value)
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def temperature_update(self, read_time, temp, target_temp):
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self.temp_samples.append((read_time, temp))
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# Check if the temperature has crossed the target and
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# enable/disable the heater if so.
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if self.heating and temp >= target_temp:
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self.heating = False
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self.check_peaks()
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@ -83,6 +85,7 @@ class ControlAutoTune:
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self.heating = True
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self.check_peaks()
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self.heater.alter_target(self.calibrate_temp)
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# Check if this temperature is a peak and record it if so
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if self.heating:
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self.set_pwm(read_time, self.heater_max_power)
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if temp < self.peak:
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@ -110,9 +113,11 @@ class ControlAutoTune:
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def calc_pid(self, pos):
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temp_diff = self.peaks[pos][0] - self.peaks[pos-1][0]
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time_diff = self.peaks[pos][1] - self.peaks[pos-2][1]
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Ku = 4. * (2. * self.heater_max_power) / (abs(temp_diff) * math.pi)
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# Use Astrom-Hagglund method to estimate Ku and Tu
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amplitude = .5 * abs(temp_diff)
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Ku = 4. * self.heater_max_power / (math.pi * amplitude)
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Tu = time_diff
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# Use Ziegler-Nichols method to generate PID parameters
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Ti = 0.5 * Tu
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Td = 0.125 * Tu
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Kp = 0.6 * Ku * heater.PID_PARAM_BASE
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