Wc = gram(sys,'c')

Wo = gram(sys,'o')

"""

#Check for ss system object, need a utility for this?

#TODO: Check for continous or discrete, only continuous supported right now

# if isCont():

# dico = 'C'

# elif isDisc():

# dico = 'D'

# else:

dico = 'C'

#TODO: Check system is stable, perhaps a utility in ctrlutil.py

# or a method of the StateSpace class?

D,V = np.linalg.eig(sys.A)

for e in D:

if e.real >= 0:

raise ValueError, "Oops, the system is unstable!"

if type=='c':

print "controllable"

trana = 'T'

C = -sys.B*sys.B.transpose()

elif type=='o':

print "observable"

else:

trana = 'N'

C = -sys.C.transpose()*sys.C

else:

raise ValueError, "Oops, neither observable, nor controllable!"

gram = 0.

#Compute Gramian by the Slycot routine sb03md

#make sure Slycot is installed

try:

from slycot import sb03md

except ImportError:

raise ControlSlycot("can't find slycot module 'sb03md'")

n = sys.states

U = np.zeros((n,n))

out = sb03md(n, C, sys.A, U, dico, 'X', 'N', trana)

gram = out[0]

return gram