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pid.py
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#############
### There are some things that I missed in the in the comments of the video.
### THESE SHOULD BE NOTED IF THIS CODE IS USED ELSEWHERE.
#############
# more efficient, but less robust and modified to work for the application
class PID_Modified:
def __init__(self,kp, ki, kd, sampletime):
# gains
self.kp = kp
self.ki = ki
self.kd = kd
# low pass filt
self.tau = 3
# print("tau is zero here")
# output and output limits
self.out = 0
self.lim_min = 0
self.lim_max = 0
# sample time, delta t
self.T = sampletime
# controller state
self.integrator = 0
self.differen= 0
self.prev_verror = 0
self.prev_vmeas = 0
self.prev_derror = 0
self.prev_dmeas = 0
def set_kp(self, val):
self.kp = val
def set_ki(self, val):
self.ki = val
def set_kd(self, val):
self.kd = val
def set_limits(self, min, max):
self.lim_min = min
self.lim_max = max
def update(self, target_dis, measurement_dis, target_vel, measurement_vel):
# error signal
derror = target_dis - measurement_dis
verror = target_vel - measurement_vel
# proportional term
proportional = self.kp * derror
# integral term
self.integrator = self.integrator + 0.5* self.ki * self.T * (verror + self.prev_verror)
# determine integrator limits (dynamic integrator clamping)
limMaxInt = limMinInt = 0
if self.lim_max > proportional:
limMaxInt = self.lim_max - proportional
else:
limMaxInt = 0
if self.lim_min < proportional:
limMinInt = self.lim_min - proportional
else:
limMinInt = 0
# actually clamp the integrator
if self.integrator > limMaxInt:
self.integrator = limMaxInt
elif self.integrator < limMinInt:
self.integrator = limMinInt
# derivate term (band limited differentiator )
self.differen = (2*self.kd*(measurement_vel - self.prev_vmeas)) \
+ (2*self.tau - self.T * self.differen) \
/ (2*self.tau + self.T)
self.out = proportional + self.integrator + self.differen
if self.out > self.lim_max:
self.out = self.lim_max
elif self.out < self.lim_min:
self.out = self.lim_min
self.prev_verror = verror
self.prev_derror = derror
self.prev_vmeas = measurement_vel
self.prev_dmeas = measurement_dis
return self.out
def reset(self):
self.integrator = 0
self.differen= 0
self.prev_verror = 0
self.prev_vmeas = 0
self.prev_derror = 0
self.prev_dmeas = 0
#################
### UNUSED
#################
class PID:
def __init__(self,kp, ki, kd, sampletime):
# gains
self.kp = kp
self.ki = ki
self.kd = kd
# low pass filt
self.tau = 0
print("tau is zero here")
# output and output limits
self.out = 0
self.lim_min = 0
self.lim_max = 0
# sample time, delta t
self.T = sampletime
# controller state
self.integrator = 0
self.differen= 0
self.prevError = 0
self.prevMeasurement = 0
def set_kp(self, val):
self.kp = val
def set_ki(self, val):
self.ki = val
def set_kd(self, val):
self.kd = val
def update(self, target, measurement):
# error signal
e = target - measurement
# proportional term
proportional = self.kp * e
# integral term
self.integrator = self.integrator + 0.5* self.ki * self.T * (e + self.prevError)
# determine integrator limits (dynamic integrator clamping)
limMaxInt = limMinInt = 0
if self.lim_max > proportional:
limMaxInt = self.lim_max - proportional
else:
limMaxInt = 0
if self.lim_min < proportional:
limMinInt = self.lim_min - proportional
else:
limMinInt = 0
# actually clamp the integrator
if self.integrator > limMaxInt:
self.integrator = limMaxInt
elif self.integrator < limMinInt:
self.integrator = limMinInt
# derivate term (band limited differentiator )
self.differen = (2*self.kd*(measurement - self.prevMeasurement)) \
+ (2*self.tau - self.T * self.differen) \
/ (2*self.tau + self.T)
self.out = proportional + self.integrator + self.differen
if self.out > self.lim_max:
self.out = self.lim_max
elif self.out < self.lim_min:
self.out = self.lim_min
self.prevError = e
self.prevMeasurement = measurement
return self.out
def set_limits(self, min, max):
self.lim_min = min
self.lim_max = max