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# Printer heater support
#
# Copyright (C) 2016-2018 Kevin O'Connor <kevin@koconnor.net>
#
# This file may be distributed under the terms of the GNU GPLv3 license.
import logging, threading
######################################################################
# Heater
######################################################################
KELVIN_TO_CELCIUS = -273.15
MAX_HEAT_TIME = 5.0
AMBIENT_TEMP = 25.
PID_PARAM_BASE = 255.
class error(Exception):
pass
class Heater:
error = error
def __init__(self, config, sensor):
self.sensor = sensor
self.name = config.get_name()
printer = config.get_printer()
self.min_temp = config.getfloat('min_temp', minval=KELVIN_TO_CELCIUS)
self.max_temp = config.getfloat('max_temp', above=self.min_temp)
self.sensor.setup_minmax(self.min_temp, self.max_temp)
self.sensor.setup_callback(self.temperature_callback)
self.pwm_delay = self.sensor.get_report_time_delta()
self.min_extrude_temp = config.getfloat(
'min_extrude_temp', 170., minval=self.min_temp, maxval=self.max_temp)
self.max_power = config.getfloat('max_power', 1., above=0., maxval=1.)
self.lock = threading.Lock()
self.last_temp = 0.
self.last_temp_time = 0.
self.target_temp = 0.
algos = {'watermark': ControlBangBang, 'pid': ControlPID}
algo = config.getchoice('control', algos)
heater_pin = config.get('heater_pin')
ppins = printer.lookup_object('pins')
if algo is ControlBangBang and self.max_power == 1.:
self.mcu_pwm = ppins.setup_pin('digital_out', heater_pin)
else:
self.mcu_pwm = ppins.setup_pin('pwm', heater_pin)
pwm_cycle_time = config.getfloat(
'pwm_cycle_time', 0.100, above=0., maxval=self.pwm_delay)
self.mcu_pwm.setup_cycle_time(pwm_cycle_time)
self.mcu_pwm.setup_max_duration(MAX_HEAT_TIME)
is_fileoutput = self.mcu_pwm.get_mcu().is_fileoutput()
self.can_extrude = self.min_extrude_temp <= 0. or is_fileoutput
self.control = algo(self, config)
# pwm caching
self.next_pwm_time = 0.
self.last_pwm_value = 0.
# Load additional modules
printer.try_load_module(config, "verify_heater %s" % (self.name,))
printer.try_load_module(config, "pid_calibrate")
def set_pwm(self, read_time, value):
if self.target_temp <= 0.:
value = 0.
if ((read_time < self.next_pwm_time or not self.last_pwm_value)
and abs(value - self.last_pwm_value) < 0.05):
# No significant change in value - can suppress update
return
pwm_time = read_time + self.pwm_delay
self.next_pwm_time = pwm_time + 0.75 * MAX_HEAT_TIME
self.last_pwm_value = value
logging.debug("%s: pwm=%.3f@%.3f (from %.3f@%.3f [%.3f])",
self.name, value, pwm_time,
self.last_temp, self.last_temp_time, self.target_temp)
self.mcu_pwm.set_pwm(pwm_time, value)
def temperature_callback(self, read_time, temp):
with self.lock:
self.last_temp = temp
self.last_temp_time = read_time
self.can_extrude = (temp >= self.min_extrude_temp)
self.control.temperature_callback(read_time, temp)
#logging.debug("temp: %.3f %f = %f", read_time, temp)
# External commands
def set_temp(self, print_time, degrees):
if degrees and (degrees < self.min_temp or degrees > self.max_temp):
raise error("Requested temperature (%.1f) out of range (%.1f:%.1f)"
% (degrees, self.min_temp, self.max_temp))
with self.lock:
self.target_temp = degrees
def get_temp(self, eventtime):
print_time = self.mcu_pwm.get_mcu().estimated_print_time(eventtime) - 5.
with self.lock:
if self.last_temp_time < print_time:
return 0., self.target_temp
return self.last_temp, self.target_temp
def check_busy(self, eventtime):
with self.lock:
return self.control.check_busy(eventtime)
def set_control(self, control):
with self.lock:
old_control = self.control
self.control = control
self.target_temp = 0.
return old_control
def stats(self, eventtime):
with self.lock:
target_temp = self.target_temp
last_temp = self.last_temp
last_pwm_value = self.last_pwm_value
is_active = target_temp or last_temp > 50.
return is_active, '%s: target=%.0f temp=%.1f pwm=%.3f' % (
self.name, target_temp, last_temp, last_pwm_value)
def get_status(self, eventtime):
with self.lock:
target_temp = self.target_temp
last_temp = self.last_temp
return {'temperature': last_temp, 'target': target_temp}
######################################################################
# Bang-bang control algo
######################################################################
class ControlBangBang:
def __init__(self, heater, config):
self.heater = heater
self.max_delta = config.getfloat('max_delta', 2.0, above=0.)
self.heating = False
def temperature_callback(self, read_time, temp):
if self.heating and temp >= self.heater.target_temp+self.max_delta:
self.heating = False
elif not self.heating and temp <= self.heater.target_temp-self.max_delta:
self.heating = True
if self.heating:
self.heater.set_pwm(read_time, self.heater.max_power)
else:
self.heater.set_pwm(read_time, 0.)
def check_busy(self, eventtime):
return self.heater.last_temp < self.heater.target_temp-self.max_delta
######################################################################
# Proportional Integral Derivative (PID) control algo
######################################################################
PID_SETTLE_DELTA = 1.
PID_SETTLE_SLOPE = .1
class ControlPID:
def __init__(self, heater, config):
self.heater = heater
self.Kp = config.getfloat('pid_Kp') / PID_PARAM_BASE
self.Ki = config.getfloat('pid_Ki') / PID_PARAM_BASE
self.Kd = config.getfloat('pid_Kd') / PID_PARAM_BASE
self.min_deriv_time = config.getfloat('pid_deriv_time', 2., above=0.)
imax = config.getfloat('pid_integral_max', heater.max_power, minval=0.)
self.temp_integ_max = imax / self.Ki
self.prev_temp = AMBIENT_TEMP
self.prev_temp_time = 0.
self.prev_temp_deriv = 0.
self.prev_temp_integ = 0.
def temperature_callback(self, read_time, temp):
time_diff = read_time - self.prev_temp_time
# Calculate change of temperature
temp_diff = temp - self.prev_temp
if time_diff >= self.min_deriv_time:
temp_deriv = temp_diff / time_diff
else:
temp_deriv = (self.prev_temp_deriv * (self.min_deriv_time-time_diff)
+ temp_diff) / self.min_deriv_time
# Calculate accumulated temperature "error"
temp_err = self.heater.target_temp - temp
temp_integ = self.prev_temp_integ + temp_err * time_diff
temp_integ = max(0., min(self.temp_integ_max, temp_integ))
# Calculate output
co = self.Kp*temp_err + self.Ki*temp_integ - self.Kd*temp_deriv
#logging.debug("pid: %f@%.3f -> diff=%f deriv=%f err=%f integ=%f co=%d",
# temp, read_time, temp_diff, temp_deriv, temp_err, temp_integ, co)
bounded_co = max(0., min(self.heater.max_power, co))
self.heater.set_pwm(read_time, bounded_co)
# Store state for next measurement
self.prev_temp = temp
self.prev_temp_time = read_time
self.prev_temp_deriv = temp_deriv
if co == bounded_co:
self.prev_temp_integ = temp_integ
def check_busy(self, eventtime):
temp_diff = self.heater.target_temp - self.heater.last_temp
return (abs(temp_diff) > PID_SETTLE_DELTA
or abs(self.prev_temp_deriv) > PID_SETTLE_SLOPE)
######################################################################
# Sensor and heater lookup
######################################################################
class PrinterHeaters:
def __init__(self, printer, config):
self.printer = printer
self.sensors = {}
self.heaters = {}
def add_sensor(self, sensor_type, sensor_factory):
self.sensors[sensor_type] = sensor_factory
def setup_heater(self, config):
heater_name = config.get_name()
if heater_name == 'extruder':
heater_name = 'extruder0'
if heater_name in self.heaters:
raise config.error("Heater %s already registered" % (heater_name,))
# Setup sensor
sensor = self.setup_sensor(config)
# Create heater
self.heaters[heater_name] = heater = Heater(config, sensor)
return heater
def lookup_heater(self, heater_name):
if heater_name == 'extruder':
heater_name = 'extruder0'
if heater_name not in self.heaters:
raise self.printer.config_error(
"Unknown heater '%s'" % (heater_name,))
return self.heaters[heater_name]
def setup_sensor(self, config):
self.printer.try_load_module(config, "thermistor")
self.printer.try_load_module(config, "adc_temperature")
sensor_type = config.get('sensor_type')
if sensor_type not in self.sensors:
raise self.printer.config_error("Unknown temperature sensor '%s'" % (
sensor_type,))
return self.sensors[sensor_type](config)
def add_printer_objects(printer, config):
printer.add_object('heater', PrinterHeaters(printer, config))
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