Issue following find_eqpt documentation · python-control/python-control

Issue following find_eqpt documentation · python-control/python-control · Discussion #1053

I'm trying to use find_eqpt in order to trim an aircraft. I need to solve for the trim throttle input and the angle of attack.

There are a couple of ways that I can't figure out how to use find_eqpt, commented below. How do I specify that d/dt of only some of the states (u, w, theta, and q) matters in this calculation, given that other states are specified as fixed?

Also, it doesn't seem like find_eqpt handles bounds or constraints, such that you can constrain a quaternion to norm 1 (this example just uses Euler angles).

# Fix output at:
Vinf = 30
beta = 0
gamma = 0

# Find this output:
alpha = 0 # guess

# Find this input:
throttle = 0.5 # guess

# State guess
x = 0
y = 0
z = 0
u = Vinf
v = 0
w = 0
phi = 0    # Roll angle
theta = 0
psi = 0    # Yaw angle
p = 0
q = 0
r = 0

x0 = np.array([x, y, z, u, v, w, phi, theta, psi, p, q, r])
u0 = np.array([throttle])

trim_state, trim_input, yeq, result = ct.find_eqpt(
  aircraft_6dof_model, 
   x0, 
   u0=u0, 
   y0=[Vinf, alpha, beta, gamma],
   iy=[0, 2, 3],           			# Constrain Vinf, beta, gamma
   ix=[4, 6, 8, 9, 10, 11],   			# Constrain v, phi, psi, p, q, r
   # dx0=[0,0,0,0,0,0,0,0,0,0,0,0],	# How to specify that xdot, ydot, and zdot don't matter?
   idx=[3, 5, 7, 10], 			        # Only care about d/dt of u, w, theta, and q	
   return_y = True,
   return_result = True
)

Depending on how I formulate the arguments, I get an input/output mismatch error, or the find_eqpt function runs infinitely.