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import serial
import queue
import threading
import numpy as np
from scipy.signal import blackmanharris
class InductionHeater:
"""Interface to the MHS5200A function generator driving the LC tank"""
def __init__(self, port, induction_min, induction_max):
self.port = port
self.induction_min = induction_min
self.induction_max = induction_max
self.queue = queue.Queue(1)
def start(self):
self.serial = serial.Serial(self.port, 57600)
self.thread = threading.Thread(target=self.thread_target)
self.thread.start()
def thread_target(self):
while True:
amount = self.queue.get()
if amount is None:
break
amount = max(min(amount, 0.5), -0.5)
freq = ((self.induction_min + self.induction_max)/2
+ amount*(self.induction_max - self.induction_min))
command = ":s1f{:010d}\n".format(int(freq*1e2))
self.serial.write(command.encode())
self.serial.readline()
def set(self, amount):
self.queue.put(amount, block=False)
def stop(self):
self.queue.put(None, block=True)
self.thread.join()
self.serial.close()
# https://gist.github.com/endolith/255291
def parabolic(f, x):
xv = 1/2. * (f[x-1] - f[x+1]) / (f[x-1] - 2 * f[x] + f[x+1]) + x
yv = f[x] - 1/4. * (f[x-1] - f[x+1]) * (xv - x)
return (xv, yv)
class Stabilizer:
def __init__(self, freq_sample, amp_threshold, freq_target, k, tuner):
self.freq_sample = freq_sample
self.amp_threshold = amp_threshold
self.freq_target = freq_target
self.k = k
self.tuner = tuner
def input(self, samples):
spectrum = np.abs(np.fft.fft(samples*blackmanharris(len(samples)))[0:len(samples)//2])
for i in range(len(spectrum)//100):
spectrum[i] = 0
spectrum[-i] = 0
i = np.argmax(spectrum)
true_i, amplitude = parabolic(spectrum, i)
freq = 0.5 * self.freq_sample * true_i / len(spectrum)
if amplitude > threshold:
tuning = (freq - target_freq)*k
else:
tuning = 0.0
self.tuner.set(tuning)
def continuous_unwrap(last_phase, last_phase_unwrapped, p):
# note: np.unwrap always preserves first element of array
p = np.unwrap(p)
glue = np.array([last_phase_unwrapped, last_phase_unwrapped + (p[0] - last_phase)])
new_p0 = np.unwrap(glue)[1]
return new_p0 + p - p[0]
class PositionTracker:
def __init__(self, leakage_avg):
self.last_phase = 0.0
self.last_position = 0.0
self.leakage = np.zeros(leakage_avg)
self.leakage_ptr = 0
def input(self, ref, meas):
demod = np.conjugate(ref)*meas
self.leakage[self.leakage_ptr] = np.real(np.sum(demod)/len(demod))
self.leakage_ptr = (self.leakage_ptr + 1) % len(self.leakage)
leakage = np.sum(self.leakage)/len(self.leakage)
phase = np.angle(demod - leakage)
position = continuous_unwrap(self.last_phase, self.last_position, phase)/(2.0*np.pi)
self.last_phase = phase[-1]
self.last_position = position[-1]
return position, leakage