311 lines
12 KiB
Python
311 lines
12 KiB
Python
# Printer heater support
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#
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# Copyright (C) 2016 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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# Available sensors
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Sensors = {
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# Common thermistors and their Steinhart-Hart coefficients
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"EPCOS 100K B57560G104F": (
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"thermistor",
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0.000722136308968056, 0.000216766566488498, 8.92935804531095e-08),
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"ATC Semitec 104GT-2": (
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"thermistor",
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0.000809651054275124, 0.000211636030735685, 7.07420883993973e-08),
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# Linear style conversion chips and their gain/offset
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"AD595": ("linear", 300.0 / 3.022, 0.),
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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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PWM_CYCLE_TIME = 0.100
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KELVIN_TO_CELCIUS = -273.15
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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.name = config.section
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sensor_params = config.getchoice('sensor_type', Sensors)
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self.is_linear_sensor = (sensor_params[0] == 'linear')
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if self.is_linear_sensor:
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adc_voltage = config.getfloat('adc_voltage', 5., above=0.)
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self.sensor_coef = sensor_params[1] * adc_voltage, sensor_params[2]
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else:
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pullup = config.getfloat('pullup_resistor', 4700., above=0.)
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self.sensor_coef = sensor_params[1:] + (pullup,)
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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.can_extrude = (self.min_extrude_temp <= 0.
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or printer.mcu.is_fileoutput())
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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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sensor_pin = config.get('sensor_pin')
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if algo is ControlBangBang and self.max_power == 1.:
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self.mcu_pwm = printer.mcu.create_digital_out(
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heater_pin, MAX_HEAT_TIME)
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else:
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self.mcu_pwm = printer.mcu.create_pwm(
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heater_pin, PWM_CYCLE_TIME, 0, MAX_HEAT_TIME)
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self.mcu_adc = printer.mcu.create_adc(sensor_pin)
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adc_range = [self.calc_adc(self.min_temp), self.calc_adc(self.max_temp)]
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self.mcu_adc.set_minmax(SAMPLE_TIME, SAMPLE_COUNT,
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minval=min(adc_range), maxval=max(adc_range))
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self.mcu_adc.set_adc_callback(REPORT_TIME, self.adc_callback)
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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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# Temperature calculation
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def calc_temp(self, adc):
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if self.is_linear_sensor:
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gain, offset = self.sensor_coef
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return adc * gain + offset
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c1, c2, c3, pullup = self.sensor_coef
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r = pullup * adc / (1.0 - adc)
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ln_r = math.log(r)
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temp_inv = c1 + c2*ln_r + c3*math.pow(ln_r, 3)
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return 1.0/temp_inv + KELVIN_TO_CELCIUS
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def calc_adc(self, temp):
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if temp is None:
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return None
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if self.is_linear_sensor:
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gain, offset = self.sensor_coef
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return (temp - offset) / gain
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c1, c2, c3, pullup = self.sensor_coef
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temp -= KELVIN_TO_CELCIUS
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temp_inv = 1./temp
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y = (c1 - temp_inv) / (2*c3)
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x = math.sqrt(math.pow(c2 / (3.*c3), 3.) + math.pow(y, 2.))
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r = math.exp(math.pow(x-y, 1./3.) - math.pow(x+y, 1./3.))
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return r / (pullup + r)
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def adc_callback(self, read_time, read_value):
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temp = self.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):
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with self.lock:
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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, temp):
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with self.lock:
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self.control = ControlAutoTune(self, self.control, temp)
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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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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) > 1. or abs(self.prev_temp_deriv) > 0.1
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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, target_temp):
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self.heater = heater
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self.old_control = old_control
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self.target_temp = target_temp
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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.target_temp:
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self.heating = False
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self.check_peaks()
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elif not self.heating and temp <= self.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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temp_diff = self.peaks[-1][0] - self.peaks[-2][0]
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time_diff = self.peaks[-1][1] - self.peaks[-3][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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Kp = 0.6 * Ku
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Ti = 0.5 * Tu
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Td = 0.125 * Tu
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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,
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Kp * PID_PARAM_BASE, Ki * PID_PARAM_BASE, Kd * PID_PARAM_BASE))
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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.heater.control = 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, target_temp):
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self.heater = heater
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self.old_control = old_control
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self.target_temp = target_temp
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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.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.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.control = self.old_control
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return False
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