1 #!/usr/bin/python

     2 # 10.9

     3 import os, sys

     4 sys.path += [os.getcwdu() + os.sep + ".." + os.sep + "python"]

     5 

     6 import scipy as sp

     7 from imcsplit import imcsplit

     8 from polyfuncs import poladd

     9 from zpowk import zpowk

    10 

    11 def imc_stable(B, A, k, alpha):

    12     """ Designs Discrete Internal Model Controller

    13     for transfer function z^{-k}B(z^{-1})/A(z^{-1})

    14     Numerator and Denominator of IMC HQ are outputs

    15     Controller is also given in R,S form. """

    16     Kp, d, Bg, Bnmp, Bm = imcsplit(B, 1)

    17     Bg = Kp * Bg

    18     Bnmpr = Bnmp[::-1]

    19     Bms = sum(Bm)

    20     HiN = A

    21     HiD = Bms * sp.convolve(Bg, Bnmpr)

    22     k = k+d

    23 

    24     zk, dzk = zpowk(k)

    25     zk = sp.squeeze(zk)

    26     Bf = 1-alpha

    27     Af = sp.array([1, -alpha])

    28     S = sp.convolve(Bf, A)

    29     R1 = sp.convolve(Af, sp.convolve(Bnmpr, Bms))

    30     R2 = sp.convolve(zk, sp.convolve(Bf, sp.convolve(Bnmp, Bm)))

    31 

    32     R, dR = poladd(R1, len(R1)-1, -R2, len(R2)-1)

    33     R = sp.squeeze(R)

    34     R = sp.convolve(Bg, R)

    35 

    36     return k, HiN, HiD, R, S