396 lines
16 KiB
Python
396 lines
16 KiB
Python
# Printer heater support
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#
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# Copyright (C) 2016-2018 Kevin O'Connor <kevin@koconnor.net>
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#
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# This file may be distributed under the terms of the GNU GPLv3 license.
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import math, logging, threading
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import pins
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######################################################################
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# Sensors
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######################################################################
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KELVIN_TO_CELCIUS = -273.15
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# Thermistor calibrated with three temp measurements
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class Thermistor:
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def __init__(self, config, params):
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self.pullup = config.getfloat('pullup_resistor', 4700., above=0.)
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# Calculate Steinhart-Hart coefficents from temp measurements
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inv_t1 = 1. / (params['t1'] - KELVIN_TO_CELCIUS)
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inv_t2 = 1. / (params['t2'] - KELVIN_TO_CELCIUS)
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inv_t3 = 1. / (params['t3'] - KELVIN_TO_CELCIUS)
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ln_r1 = math.log(params['r1'])
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ln_r2 = math.log(params['r2'])
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ln_r3 = math.log(params['r3'])
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ln3_r1, ln3_r2, ln3_r3 = ln_r1**3, ln_r2**3, ln_r3**3
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inv_t12, inv_t13 = inv_t1 - inv_t2, inv_t1 - inv_t3
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ln_r12, ln_r13 = ln_r1 - ln_r2, ln_r1 - ln_r3
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ln3_r12, ln3_r13 = ln3_r1 - ln3_r2, ln3_r1 - ln3_r3
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self.c3 = ((inv_t12 - inv_t13 * ln_r12 / ln_r13)
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/ (ln3_r12 - ln3_r13 * ln_r12 / ln_r13))
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self.c2 = (inv_t12 - self.c3 * ln3_r12) / ln_r12
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self.c1 = inv_t1 - self.c2 * ln_r1 - self.c3 * ln3_r1
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def calc_temp(self, adc):
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adc = max(.00001, min(.99999, adc))
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r = self.pullup * adc / (1.0 - adc)
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ln_r = math.log(r)
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inv_t = self.c1 + self.c2 * ln_r + self.c3 * ln_r**3
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return 1.0/inv_t + KELVIN_TO_CELCIUS
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def calc_adc(self, temp):
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inv_t = 1. / (temp - KELVIN_TO_CELCIUS)
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if self.c3:
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y = (self.c1 - inv_t) / (2. * self.c3)
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x = math.sqrt((self.c2 / (3. * self.c3))**3 + y**2)
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ln_r = math.pow(x - y, 1./3.) - math.pow(x + y, 1./3.)
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else:
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ln_r = (inv_t - self.c1) / self.c2
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r = math.exp(ln_r)
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return r / (self.pullup + r)
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# Thermistor calibrated from one temp measurement and its beta
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class ThermistorBeta(Thermistor):
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def __init__(self, config, params):
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self.pullup = config.getfloat('pullup_resistor', 4700., above=0.)
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# Calculate Steinhart-Hart coefficents from beta
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inv_t1 = 1. / (params['t1'] - KELVIN_TO_CELCIUS)
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ln_r1 = math.log(params['r1'])
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self.c3 = 0.
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self.c2 = 1. / params['beta']
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self.c1 = inv_t1 - self.c2 * ln_r1
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# Linear style conversion chips calibrated with two temp measurements
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class Linear:
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def __init__(self, config, params):
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adc_voltage = config.getfloat('adc_voltage', 5., above=0.)
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slope = (params['t2'] - params['t1']) / (params['v2'] - params['v1'])
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self.gain = adc_voltage * slope
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self.offset = params['t1'] - params['v1'] * slope
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def calc_temp(self, adc):
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return adc * self.gain + self.offset
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def calc_adc(self, temp):
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return (temp - self.offset) / self.gain
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# Available sensors
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Sensors = {
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"EPCOS 100K B57560G104F": {
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'class': Thermistor, 't1': 25., 'r1': 100000.,
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't2': 150., 'r2': 1641.9, 't3': 250., 'r3': 226.15 },
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"ATC Semitec 104GT-2": {
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'class': Thermistor, 't1': 20., 'r1': 126800.,
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't2': 150., 'r2': 1360., 't3': 300., 'r3': 80.65 },
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"NTC 100K beta 3950": {
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'class': ThermistorBeta, 't1': 25., 'r1': 100000., 'beta': 3950. },
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"AD595": { 'class': Linear, 't1': 25., 'v1': .25, 't2': 300., 'v2': 3.022 },
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}
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######################################################################
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# Heater
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######################################################################
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SAMPLE_TIME = 0.001
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SAMPLE_COUNT = 8
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REPORT_TIME = 0.300
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MAX_HEAT_TIME = 5.0
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AMBIENT_TEMP = 25.
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PID_PARAM_BASE = 255.
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class error(Exception):
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pass
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class PrinterHeater:
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error = error
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def __init__(self, printer, config):
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self.printer = printer
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self.name = config.get_name()
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sensor_params = config.getchoice('sensor_type', Sensors)
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self.sensor = sensor_params['class'](config, sensor_params)
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self.min_temp = config.getfloat('min_temp', minval=0.)
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self.max_temp = config.getfloat('max_temp', above=self.min_temp)
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self.min_extrude_temp = config.getfloat(
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'min_extrude_temp', 170., minval=self.min_temp, maxval=self.max_temp)
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self.max_power = config.getfloat('max_power', 1., above=0., maxval=1.)
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self.lock = threading.Lock()
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self.last_temp = 0.
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self.last_temp_time = 0.
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self.target_temp = 0.
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algos = {'watermark': ControlBangBang, 'pid': ControlPID}
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algo = config.getchoice('control', algos)
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heater_pin = config.get('heater_pin')
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if algo is ControlBangBang and self.max_power == 1.:
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self.mcu_pwm = pins.setup_pin(printer, 'digital_out', heater_pin)
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else:
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self.mcu_pwm = pins.setup_pin(printer, 'pwm', heater_pin)
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pwm_cycle_time = config.getfloat(
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'pwm_cycle_time', 0.100, above=0., maxval=REPORT_TIME)
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self.mcu_pwm.setup_cycle_time(pwm_cycle_time)
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self.mcu_pwm.setup_max_duration(MAX_HEAT_TIME)
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self.mcu_adc = pins.setup_pin(printer, 'adc', config.get('sensor_pin'))
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adc_range = [self.sensor.calc_adc(self.min_temp),
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self.sensor.calc_adc(self.max_temp)]
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self.mcu_adc.setup_minmax(SAMPLE_TIME, SAMPLE_COUNT,
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minval=min(adc_range), maxval=max(adc_range))
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self.mcu_adc.setup_adc_callback(REPORT_TIME, self.adc_callback)
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is_fileoutput = self.mcu_adc.get_mcu().is_fileoutput()
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self.can_extrude = self.min_extrude_temp <= 0. or is_fileoutput
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self.control = algo(self, config)
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# pwm caching
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self.next_pwm_time = 0.
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self.last_pwm_value = 0.
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def set_pwm(self, read_time, value):
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if self.target_temp <= 0.:
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value = 0.
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if ((read_time < self.next_pwm_time or not self.last_pwm_value)
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and abs(value - self.last_pwm_value) < 0.05):
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# No significant change in value - can suppress update
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return
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pwm_time = read_time + REPORT_TIME + SAMPLE_TIME*SAMPLE_COUNT
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self.next_pwm_time = pwm_time + 0.75 * MAX_HEAT_TIME
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self.last_pwm_value = value
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logging.debug("%s: pwm=%.3f@%.3f (from %.3f@%.3f [%.3f])",
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self.name, value, pwm_time,
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self.last_temp, self.last_temp_time, self.target_temp)
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self.mcu_pwm.set_pwm(pwm_time, value)
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def adc_callback(self, read_time, read_value):
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temp = self.sensor.calc_temp(read_value)
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with self.lock:
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self.last_temp = temp
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self.last_temp_time = read_time
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self.can_extrude = (temp >= self.min_extrude_temp)
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self.control.adc_callback(read_time, temp)
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#logging.debug("temp: %.3f %f = %f", read_time, read_value, temp)
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# External commands
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def set_temp(self, print_time, degrees):
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if degrees and (degrees < self.min_temp or degrees > self.max_temp):
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raise error("Requested temperature (%.1f) out of range (%.1f:%.1f)"
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% (degrees, self.min_temp, self.max_temp))
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with self.lock:
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self.target_temp = degrees
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def get_temp(self, eventtime):
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print_time = self.mcu_adc.get_mcu().estimated_print_time(eventtime) - 5.
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with self.lock:
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if self.last_temp_time < print_time:
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return 0., self.target_temp
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return self.last_temp, self.target_temp
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def check_busy(self, eventtime):
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with self.lock:
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return self.control.check_busy(eventtime)
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def start_auto_tune(self, degrees):
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if degrees and (degrees < self.min_temp or degrees > self.max_temp):
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raise error("Requested temperature (%.1f) out of range (%.1f:%.1f)"
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% (degrees, self.min_temp, self.max_temp))
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with self.lock:
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self.control = ControlAutoTune(self, self.control)
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self.target_temp = degrees
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def finish_auto_tune(self, old_control):
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self.control = old_control
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self.target_temp = 0
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def stats(self, eventtime):
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with self.lock:
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target_temp = self.target_temp
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last_temp = self.last_temp
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last_pwm_value = self.last_pwm_value
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return '%s: target=%.0f temp=%.0f pwm=%.3f' % (
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self.name, target_temp, last_temp, last_pwm_value)
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######################################################################
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# Bang-bang control algo
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######################################################################
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class ControlBangBang:
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def __init__(self, heater, config):
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self.heater = heater
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self.max_delta = config.getfloat('max_delta', 2.0, above=0.)
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self.heating = False
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def adc_callback(self, read_time, temp):
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if self.heating and temp >= self.heater.target_temp+self.max_delta:
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self.heating = False
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elif not self.heating and temp <= self.heater.target_temp-self.max_delta:
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self.heating = True
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if self.heating:
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self.heater.set_pwm(read_time, self.heater.max_power)
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else:
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self.heater.set_pwm(read_time, 0.)
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def check_busy(self, eventtime):
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return self.heater.last_temp < self.heater.target_temp-self.max_delta
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######################################################################
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# Proportional Integral Derivative (PID) control algo
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######################################################################
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PID_SETTLE_DELTA = 1.
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PID_SETTLE_SLOPE = .1
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class ControlPID:
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def __init__(self, heater, config):
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self.heater = heater
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self.Kp = config.getfloat('pid_Kp') / PID_PARAM_BASE
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self.Ki = config.getfloat('pid_Ki') / PID_PARAM_BASE
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self.Kd = config.getfloat('pid_Kd') / PID_PARAM_BASE
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self.min_deriv_time = config.getfloat('pid_deriv_time', 2., above=0.)
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imax = config.getfloat('pid_integral_max', heater.max_power, minval=0.)
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self.temp_integ_max = imax / self.Ki
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self.prev_temp = AMBIENT_TEMP
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self.prev_temp_time = 0.
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self.prev_temp_deriv = 0.
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self.prev_temp_integ = 0.
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def adc_callback(self, read_time, temp):
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time_diff = read_time - self.prev_temp_time
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# Calculate change of temperature
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temp_diff = temp - self.prev_temp
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if time_diff >= self.min_deriv_time:
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temp_deriv = temp_diff / time_diff
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else:
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temp_deriv = (self.prev_temp_deriv * (self.min_deriv_time-time_diff)
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+ temp_diff) / self.min_deriv_time
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# Calculate accumulated temperature "error"
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temp_err = self.heater.target_temp - temp
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temp_integ = self.prev_temp_integ + temp_err * time_diff
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temp_integ = max(0., min(self.temp_integ_max, temp_integ))
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# Calculate output
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co = self.Kp*temp_err + self.Ki*temp_integ - self.Kd*temp_deriv
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#logging.debug("pid: %f@%.3f -> diff=%f deriv=%f err=%f integ=%f co=%d",
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# temp, read_time, temp_diff, temp_deriv, temp_err, temp_integ, co)
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bounded_co = max(0., min(self.heater.max_power, co))
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self.heater.set_pwm(read_time, bounded_co)
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# Store state for next measurement
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self.prev_temp = temp
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self.prev_temp_time = read_time
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self.prev_temp_deriv = temp_deriv
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if co == bounded_co:
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self.prev_temp_integ = temp_integ
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def check_busy(self, eventtime):
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temp_diff = self.heater.target_temp - self.heater.last_temp
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return (abs(temp_diff) > PID_SETTLE_DELTA
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or abs(self.prev_temp_deriv) > PID_SETTLE_SLOPE)
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######################################################################
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# Ziegler-Nichols PID autotuning
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######################################################################
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TUNE_PID_DELTA = 5.0
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class ControlAutoTune:
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def __init__(self, heater, old_control):
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self.heater = heater
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self.old_control = old_control
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self.heating = False
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self.peaks = []
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self.peak = 0.
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self.peak_time = 0.
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def adc_callback(self, read_time, temp):
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if self.heating and temp >= self.heater.target_temp:
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self.heating = False
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self.check_peaks()
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elif (not self.heating
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and temp <= self.heater.target_temp - TUNE_PID_DELTA):
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self.heating = True
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self.check_peaks()
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if self.heating:
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self.heater.set_pwm(read_time, self.heater.max_power)
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if temp < self.peak:
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self.peak = temp
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self.peak_time = read_time
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else:
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self.heater.set_pwm(read_time, 0.)
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if temp > self.peak:
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self.peak = temp
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self.peak_time = read_time
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def check_peaks(self):
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self.peaks.append((self.peak, self.peak_time))
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if self.heating:
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self.peak = 9999999.
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else:
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self.peak = -9999999.
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if len(self.peaks) < 4:
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return
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self.calc_pid(len(self.peaks)-1)
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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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max_power = self.heater.max_power
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Ku = 4. * (2. * max_power) / (abs(temp_diff) * math.pi)
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Tu = time_diff
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Ti = 0.5 * Tu
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Td = 0.125 * Tu
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Kp = 0.6 * Ku * PID_PARAM_BASE
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Ki = Kp / Ti
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Kd = Kp * Td
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logging.info("Autotune: raw=%f/%f Ku=%f Tu=%f Kp=%f Ki=%f Kd=%f",
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temp_diff, max_power, Ku, Tu, Kp, Ki, Kd)
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return Kp, Ki, Kd
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def final_calc(self):
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cycle_times = [(self.peaks[pos][1] - self.peaks[pos-2][1], pos)
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for pos in range(4, len(self.peaks))]
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midpoint_pos = sorted(cycle_times)[len(cycle_times)/2][1]
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Kp, Ki, Kd = self.calc_pid(midpoint_pos)
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logging.info("Autotune: final: Kp=%f Ki=%f Kd=%f", Kp, Ki, Kd)
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gcode = self.heater.printer.lookup_object('gcode')
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gcode.respond_info(
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"PID parameters: pid_Kp=%.3f pid_Ki=%.3f pid_Kd=%.3f\n"
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"To use these parameters, update the printer config file with\n"
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"the above and then issue a RESTART command" % (Kp, Ki, Kd))
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def check_busy(self, eventtime):
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if self.heating or len(self.peaks) < 12:
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return True
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self.final_calc()
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self.heater.finish_auto_tune(self.old_control)
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return False
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######################################################################
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# Tuning information test
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######################################################################
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class ControlBumpTest:
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def __init__(self, heater, old_control):
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self.heater = heater
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self.old_control = old_control
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self.temp_samples = {}
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self.pwm_samples = {}
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self.state = 0
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def set_pwm(self, read_time, value):
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self.pwm_samples[read_time + 2*REPORT_TIME] = value
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self.heater.set_pwm(read_time, value)
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def adc_callback(self, read_time, temp):
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self.temp_samples[read_time] = temp
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if not self.state:
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self.set_pwm(read_time, 0.)
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if len(self.temp_samples) >= 20:
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self.state += 1
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elif self.state == 1:
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if temp < self.heater.target_temp:
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self.set_pwm(read_time, self.heater.max_power)
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return
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self.set_pwm(read_time, 0.)
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self.state += 1
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elif self.state == 2:
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self.set_pwm(read_time, 0.)
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if temp <= (self.heater.target_temp + AMBIENT_TEMP) / 2.:
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self.dump_stats()
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self.state += 1
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def dump_stats(self):
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out = ["%.3f %.1f %d" % (time, temp, self.pwm_samples.get(time, -1.))
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for time, temp in sorted(self.temp_samples.items())]
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f = open("/tmp/heattest.txt", "wb")
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f.write('\n'.join(out))
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f.close()
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def check_busy(self, eventtime):
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if self.state < 3:
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return True
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self.heater.finish_auto_tune(self.old_control)
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return False
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def add_printer_objects(printer, config):
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if config.has_section('heater_bed'):
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printer.add_object('heater_bed', PrinterHeater(
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printer, config.getsection('heater_bed')))
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