131 lines
3.8 KiB
Python
131 lines
3.8 KiB
Python
import numpy as np
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#based on https://en.wikipedia.org/wiki/PID_controller#Discrete_implementation
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def trap_int(vec,timestep):
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l = np.size(vec)
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int = 0
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for i in range(l-1):
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int = int + (vec[i]+vec[i+1])/2*timestep
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return int
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def ISE_fun(error_history,timestep):
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# calcuate the integral of square error
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e = np.array(error_history)
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dt = timestep
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ise = trap_int(e**2,dt)
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return ise
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def IAE_fun(error_history,timestep):
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# calcuate the integral of absolute error
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e = np.array(error_history)
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dt = timestep
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iae = trap_int(np.abs(e),dt)
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return iae
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def ITSE_fun(error_history,timestep):
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# calcuate the integral of time multiply square error
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e = np.array(error_history)
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dt = timestep
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n = np.size(e)
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t = np.arange(0,n)*dt
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itse = trap_int(t*e**2,dt)
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return itse
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def ITAE_fun(error_history,timestep):
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# calcuate the integral of time multiply absolute error
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e = np.array(error_history)
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dt = timestep
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n = np.size(e)
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t = np.arange(0,n)*dt
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itae = trap_int(np.abs(e),dt)
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return itae
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class P_controller_class:
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def __init__(self,setpoint,proportionality_constant):
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self.SP = setpoint
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self.Kp = proportionality_constant
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self.error_history = []
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self.control_variable = 0.1
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self.lower_limit = -0.1 # default
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self.upper_limit = +0.1 # default
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def set_control_variable_limits(self,lower_limit,upper_limit):
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self.lower_limit = lower_limit
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self.upper_limit = upper_limit
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def calculate_error(self,process_variable):
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self.error = self.SP-process_variable
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self.error_history.append(self.error)
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def get_control_variable(self):
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new_control = self.control_variable+self.Kp*(self.error_history[-1]-self.error_history[-2])
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if new_control < self.lower_limit:
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new_control = self.lower_limit
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if new_control > self.upper_limit:
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new_control = self.upper_limit
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self.control_variable = new_control
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# print(new_control)
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return new_control
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class PI_controller_class:
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def __init__(self,setpoint,proportionality_constant,Ti, timestep):
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self.SP = setpoint
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self.Kp = proportionality_constant
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self.Ti = Ti
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self.dt = timestep
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self.error_history = [0,0]
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self.control_variable = 0.0
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self.lower_limit = -1.3 # default
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self.upper_limit = +1.3 # default
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def set_control_variable_limits(self,lower_limit,upper_limit):
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self.lower_limit = lower_limit
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self.upper_limit = upper_limit
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def calculate_error(self,process_variable):
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self.error = self.SP-process_variable
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self.error_history.append(self.error)
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def get_control_variable(self):
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cv = self.control_variable
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Kp = self.Kp
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Ti = self.Ti
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dt = self.dt
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e0 = self.error_history[-1]
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e1 = self.error_history[-2]
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new_control = cv+Kp*(e0-e1)+dt/Ti*e0
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if new_control < self.lower_limit:
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new_control = self.lower_limit
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if new_control > self.upper_limit:
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new_control = self.upper_limit
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self.control_variable = new_control
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# print(new_control)
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return new_control
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def get_performance_indicators(self,ISE=True,IAE=True,ITSE=True,ITAE=True):
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ise = np.nan
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iae = np.nan
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itse = np.nan
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itae = np.nan
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if ISE == True:
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ise = ISE_fun(self.error_history[2:],self.dt)
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if IAE == True:
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iae = IAE_fun(self.error_history[2:],self.dt)
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if ITSE == True:
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itse = ITSE_fun(self.error_history[2:],self.dt)
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if ITAE == True:
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itae = ITAE_fun(self.error_history[2:],self.dt)
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return ise,iae,itse,itae
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