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# Printer heater support
#
# Copyright (C) 2016 Kevin O'Connor <kevin@koconnor.net>
#
# This file may be distributed under the terms of the GNU GPLv3 license.
import math, logging, threading
# Mapping from name to Steinhart-Hart coefficients
Thermistors = {
"EPCOS 100K B57560G104F": (
0.000722136308968056, 0.000216766566488498, 8.92935804531095e-08)
}
SAMPLE_TIME = 0.001
SAMPLE_COUNT = 8
REPORT_TIME = 0.300
KELVIN_TO_CELCIUS = -273.15
MAX_HEAT_TIME = 5.0
AMBIENT_TEMP = 25.
PWM_MAX = 255
class PrinterHeater:
def __init__(self, printer, config):
self.printer = printer
self.config = config
self.mcu_pwm = self.mcu_adc = None
self.thermistor_c = Thermistors.get(config.get('thermistor_type'))
self.pullup_r = config.getfloat('pullup_resistor', 4700.)
self.lock = threading.Lock()
self.last_temp = 0.
self.last_temp_clock = 0
self.target_temp = 0.
self.report_clock = 0
self.control = None
# pwm caching
self.next_pwm_clock = 0
self.last_pwm_value = 0
self.resend_clock = 0
self.pwm_offset_clock = 0
def build_config(self):
heater_pin = self.config.get('heater_pin')
thermistor_pin = self.config.get('thermistor_pin')
self.mcu_pwm = self.printer.mcu.create_pwm(heater_pin, 0, MAX_HEAT_TIME)
self.mcu_adc = self.printer.mcu.create_adc(thermistor_pin)
min_adc = self.calc_adc(self.config.getfloat('max_temp'))
max_adc = self.calc_adc(self.config.getfloat('min_temp'))
freq = self.printer.mcu.get_mcu_freq()
sample_clock = int(SAMPLE_TIME*freq)
self.mcu_adc.set_minmax(
sample_clock, SAMPLE_COUNT, minval=min_adc, maxval=max_adc)
self.mcu_adc.set_adc_callback(self.adc_callback)
self.report_clock = int(REPORT_TIME*freq)
control_algo = self.config.get('control', 'watermark')
algos = {'watermark': ControlBangBang, 'pid': ControlPID}
self.control = algos[control_algo](self, self.config)
self.next_pwm_clock = 0
self.last_pwm_value = 0
self.resend_clock = int(MAX_HEAT_TIME * freq * 3. / 4.)
self.pwm_offset_clock = sample_clock*SAMPLE_COUNT + self.report_clock
def run(self):
self.mcu_adc.query_analog_in(self.report_clock)
def set_pwm(self, read_clock, value):
if value:
if self.target_temp <= 0.:
return
if (read_clock < self.next_pwm_clock
and abs(value - self.last_pwm_value) < 15):
return
elif not self.last_pwm_value:
return
pwm_clock = read_clock + self.pwm_offset_clock
self.next_pwm_clock = pwm_clock + self.resend_clock
self.last_pwm_value = value
logging.debug("pwm=%d@%d (%d)" % (value, read_clock, pwm_clock))
self.mcu_pwm.set_pwm(pwm_clock, value)
# Temperature calculation
def calc_temp(self, adc):
r = self.pullup_r * adc / (1.0 - adc)
ln_r = math.log(r)
c1, c2, c3 = self.thermistor_c
temp_inv = c1 + c2*ln_r + c3*math.pow(ln_r, 3)
return 1.0/temp_inv + KELVIN_TO_CELCIUS
def calc_adc(self, temp):
if temp is None:
return None
c1, c2, c3 = self.thermistor_c
temp -= KELVIN_TO_CELCIUS
temp_inv = 1./temp
y = (c1 - temp_inv) / (2*c3)
x = math.sqrt(math.pow(c2 / (3.*c3), 3.) + math.pow(y, 2.))
r = math.exp(math.pow(x-y, 1./3.) - math.pow(x+y, 1./3.))
return r / (self.pullup_r + r)
def adc_callback(self, read_clock, read_value):
temp = self.calc_temp(float(read_value))
with self.lock:
self.last_temp = temp
self.last_temp_clock = read_clock
self.control.adc_callback(read_clock, temp)
#logging.debug("temp: %d(%d) %f = %f" % (
# read_clock, read_clock & 0xffffffff, read_value, temp))
# External commands
def set_temp(self, print_time, degrees):
with self.lock:
self.target_temp = degrees
def get_temp(self):
with self.lock:
return self.last_temp, self.target_temp
def check_busy(self, eventtime):
with self.lock:
return self.control.check_busy(eventtime)
def start_auto_tune(self, temp):
with self.lock:
self.control = ControlAutoTune(self, self.control, temp)
######################################################################
# Bang-bang control algo
######################################################################
class ControlBangBang:
def __init__(self, heater, config):
self.heater = heater
self.max_delta = config.getfloat('max_delta', 2.0)
self.heating = False
def adc_callback(self, read_clock, 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_clock, PWM_MAX)
else:
self.heater.set_pwm(read_clock, 0)
def check_busy(self, eventtime):
return self.heater.last_temp < self.heater.target_temp-self.max_delta
######################################################################
# Proportional Integral Derivative (PID) control algo
######################################################################
class ControlPID:
def __init__(self, heater, config):
self.heater = heater
self.Kp = config.getfloat('pid_Kp')
self.Ki = config.getfloat('pid_Ki')
self.Kd = config.getfloat('pid_Kd')
self.min_deriv_time = config.getfloat('pid_deriv_time', 2.)
imax = config.getint('pid_integral_max', PWM_MAX)
self.temp_integ_max = imax / self.Ki
self.prev_temp = AMBIENT_TEMP
self.prev_temp_clock = 0
self.prev_temp_deriv = 0.
self.prev_temp_integ = 0.
self.inv_mcu_freq = 1. / self.heater.printer.mcu.get_mcu_freq()
def adc_callback(self, read_clock, temp):
time_diff = (read_clock - self.prev_temp_clock) * self.inv_mcu_freq
# 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 = int(self.Kp*temp_err + self.Ki*temp_integ - self.Kd*temp_deriv)
#logging.debug("pid: %f@%d -> diff=%f deriv=%f err=%f integ=%f co=%d" % (
# temp, read_clock, temp_diff, temp_deriv, temp_err, temp_integ, co))
bounded_co = max(0, min(PWM_MAX, co))
self.heater.set_pwm(read_clock, bounded_co)
# Store state for next measurement
self.prev_temp = temp
self.prev_temp_clock = read_clock
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) > 1. or abs(self.prev_temp_deriv) > 0.1
######################################################################
# Ziegler-Nichols PID autotuning
######################################################################
TUNE_PID_DELTA = 5.0
class ControlAutoTune:
def __init__(self, heater, old_control, target_temp):
self.heater = heater
self.old_control = old_control
self.target_temp = target_temp
self.heating = False
self.peaks = []
self.peak = 0.
self.peak_clock = 0
def adc_callback(self, read_clock, temp):
if self.heating and temp >= self.target_temp:
self.heating = False
self.check_peaks()
elif not self.heating and temp <= self.target_temp - TUNE_PID_DELTA:
self.heating = True
self.check_peaks()
if self.heating:
self.heater.set_pwm(read_clock, PWM_MAX)
if temp < self.peak:
self.peak = temp
self.peak_clock = read_clock
else:
self.heater.set_pwm(read_clock, 0)
if temp > self.peak:
self.peak = temp
self.peak_clock = read_clock
def check_peaks(self):
self.peaks.append((self.peak, self.peak_clock))
if self.heating:
self.peak = 9999999.
else:
self.peak = -9999999.
if len(self.peaks) < 4:
return
temp_diff = self.peaks[-1][0] - self.peaks[-2][0]
clock_diff = self.peaks[-1][1] - self.peaks[-3][1]
pwm_diff = PWM_MAX - 0
Ku = 4. * (2. * pwm_diff) / (abs(temp_diff) * math.pi)
Tu = clock_diff / self.heater.printer.mcu.get_mcu_freq()
Kp = 0.6 * Ku
Ti = 0.5 * Tu
Td = 0.125 * Tu
Ki = Kp / Ti
Kd = Kp * Td
logging.info("Autotune: raw=%f/%d/%d Ku=%f Tu=%f Kp=%f Ki=%f Kd=%f" % (
temp_diff, clock_diff, pwm_diff, Ku, Tu, Kp, Ki, Kd))
def check_busy(self, eventtime):
if self.heating or len(self.peaks) < 12:
return True
self.heater.control = self.old_control
return False
######################################################################
# Tuning information test
######################################################################
class ControlBumpTest:
def __init__(self, heater, old_control, target_temp):
self.heater = heater
self.old_control = old_control
self.target_temp = target_temp
self.temp_samples = {}
self.pwm_samples = {}
self.state = 0
def set_pwm(self, read_clock, value):
self.pwm_samples[read_clock + 2*self.heater.report_clock] = value
self.heater.set_pwm(read_clock, value)
def adc_callback(self, read_clock, temp):
self.temp_samples[read_clock] = temp
if not self.state:
self.set_pwm(read_clock, 0)
if len(self.temp_samples) >= 20:
self.state += 1
elif self.state == 1:
if temp < self.target_temp:
self.set_pwm(read_clock, PWM_MAX)
return
self.set_pwm(read_clock, 0)
self.state += 1
elif self.state == 2:
self.set_pwm(read_clock, 0)
if temp <= (self.target_temp + AMBIENT_TEMP) / 2.:
self.dump_stats()
self.state += 1
def dump_stats(self):
out = ["%d %.1f %d" % (clock, temp, self.pwm_samples.get(clock, -1))
for clock, temp in sorted(self.temp_samples.items())]
f = open("/tmp/heattest.txt", "wb")
f.write('\n'.join(out))
f.close()
def check_busy(self, eventtime):
if self.state < 3:
return True
self.heater.control = self.old_control
return False
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