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import time
from qolab.hardware.basic import BasicInstrument
class PID(BasicInstrument):
"""Proportional–integral–derivative controller.
Calculates feedback based on gains, time, and previous error signal measurements.
"""
def __init__(self, Gp=0, Gi=0, Gd=0, sign=1, enable=True, *args, **kwds):
super().__init__(*args, **kwds)
self.config["Device model"] = "Generic Software PID loop"
self.config["Device type"] = "PID loop"
self.config["FnamePrefix"] = "pid"
self.deviceProperties.update({"Gp", "Gi", "Gd", "Sign", "Enable"})
self.setGp(Gp)
self.setGi(Gi)
self.setGd(Gd)
self.setSign(sign)
self.setEnable(enable)
self.reset()
def __repr__(self):
s = ""
s += f"{self.__class__.__name__}("
s += f"Gp={self.Gp}"
s += f", Gi={self.Gi}"
s += f", Gd={self.Gd}"
s += f", sign={self.enable}"
if self.config["DeviceNickname"] is not None:
s += ", device_nickname='"
s += f"{self.config['DeviceNickname']}"
s += "'"
s += ")"
return s
@BasicInstrument.tsdb_append
def getGp(self):
return self.Gp
@BasicInstrument.tsdb_append
def setGp(self, val):
self.Gp = val
@BasicInstrument.tsdb_append
def getGi(self):
return self.Gi
@BasicInstrument.tsdb_append
def setGi(self, val):
self.Gi = val
@BasicInstrument.tsdb_append
def getGd(self):
return self.Gd
@BasicInstrument.tsdb_append
def setGd(self, val):
self.Gd = val
@BasicInstrument.tsdb_append
def getSign(self):
return self.sign
@BasicInstrument.tsdb_append
def setSign(self, val):
self.sign = val
@BasicInstrument.tsdb_append
def getEnable(self):
return self.enable
@BasicInstrument.tsdb_append
def setEnable(self, val):
self.enable = val
def reset(self):
self.err_1dt_back = 0
self.err_2dt_back = 0
self.err_now = 0
self.last_update = time.time()
def feedback(self, err):
# PID feedback
# see https://en.wikipedia.org/wiki/PID_controller#Pseudocode
self.err_2dt_back = self.err_1dt_back
self.err_1dt_back = self.err_now
self.err_now = err
tnow = time.time()
dt = tnow - self.last_update
self.last_update = tnow
A0 = self.Gp + self.Gi * dt + self.Gd / dt
A1 = -self.Gp - 2 * self.Gd / dt
A2 = self.Gd / dt
u = A0 * self.err_now + A1 * self.err_1dt_back + A2 * self.err_2dt_back
u *= self.sign
if not self.enable:
return 0
return u
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