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56
scripts/libraries/pid.py
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56
scripts/libraries/pid.py
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'''
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Example:
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from pid import PID
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pid1 = PID(p=0.07, i=0, imax=90)
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while(True):
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error = 50 #error should be caculated, target - mesure
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output=pid1.get_pid(error,1)
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#control value with output
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'''
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from pyb import millis
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from math import pi, isnan
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class PID:
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_kp = _ki = _kd = _integrator = _imax = 0
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_last_error = _last_derivative = _last_t = 0
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_RC = 1/(2 * pi * 20)
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def __init__(self, p=0, i=0, d=0, imax=0):
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self._kp = float(p)
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self._ki = float(i)
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self._kd = float(d)
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self._imax = abs(imax)
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self._last_derivative = float('nan')
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def get_pid(self, error, scaler):
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tnow = millis()
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dt = tnow - self._last_t
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output = 0
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if self._last_t == 0 or dt > 1000:
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dt = 0
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self.reset_I()
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self._last_t = tnow
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delta_time = float(dt) / float(1000)
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output += error * self._kp
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if abs(self._kd) > 0 and dt > 0:
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if isnan(self._last_derivative):
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derivative = 0
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self._last_derivative = 0
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else:
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derivative = (error - self._last_error) / delta_time
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derivative = self._last_derivative + \
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((delta_time / (self._RC + delta_time)) * \
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(derivative - self._last_derivative))
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self._last_error = error
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self._last_derivative = derivative
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output += self._kd * derivative
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output *= scaler
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if abs(self._ki) > 0 and dt > 0:
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self._integrator += (error * self._ki) * scaler * delta_time
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if self._integrator < -self._imax: self._integrator = -self._imax
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elif self._integrator > self._imax: self._integrator = self._imax
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output += self._integrator
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return output
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def reset_I(self):
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self._integrator = 0
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self._last_derivative = float('nan')
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