why would the code bellow yield this error?????? thanks
from sympy import *
import numpy as np
init_printing(use_unicode=False, wrap_line=True, no_global=True)
#flat earth, rigid ,symatric , body axis
theta,phi,psi=var('theta,phi,psi')
p,q,r=var('p,q,r')
u,v,w=var('u,v,w')
Xe,Ye,Ze=var('Xe,Ye,Ze')
deltAileron,deltRudder=var('deltAileron,deltRudder')
deltFlap,deltElevator,dotAlpha=var('deltFlap,deltElevator,dotAlpha')
####################################
#g=var('g')
g=9.81#m/s**2
H_I2B=Matrix([[cos(theta)*cos(psi),cos(theta)*sin(psi),-sin(theta)],
[(-cos(theta)*sin(psi)+sin(phi)*sin(theta)*cos(psi)),(cos(phi)*cos(psi)+sin(phi)*sin(theta)*cos(psi)),sin(phi)*cos(theta)],
[(sin(phi)*sin(psi)+cos(phi)*sin(theta)*cos(psi)),(-sin(phi)*cos(psi)+cos(phi)*sin(theta)*sin(psi)),cos(phi)*cos(theta)]])
gx,gy,gz=H_I2B*Matrix(3,1,[0,0,g])#gravity in body frame
#b,c,S=var('b,c,S')
#wing span
b=2.8956# m
#mean aerodynamics chord
c=0.189941 # %
#wing area
S=0.55# m**2
#m=var('m')
m=13.5# kg
#e,AR=var('e,AR')
#Oswald's coefficient
e=0.75
AR=b**2/S
#CL_0,CL_alpha,CL_deltFlap,CL_deltElevator,CL_dotAlpha,CL_q,CL_Mach=var('CL_0,CL_alpha,CL_deltFlap,CL_deltElevator,CL_dotAlpha,CL_q,CL_Mach')
####Lift coefficient######
#Zero-alpha lift
CL_0=0.23
CL_alpha=5.6106
CL_deltFlap=0.74
CL_deltElevator=0.13
CL_dotAlpha=1.9724
CL_q=7.9543
CL_Mach=0
#CD_0,CL_minD,CD_deltFlap,CD_deltElevator,CD_deltAileron,CD_deltRudder,CD_Mach=var('CD_0,CL_minD,CD_deltFlap,CD_deltElevator,CD_deltAileron,CD_deltRudder,CD_Mach')
CD_0=0.0434
CL_minD=0.0434
CD_deltFlap=0.1467
CD_deltElevator=0.0135
CD_deltAileron=0.0302
CD_deltRudder=0.0303
CD_Mach=0
#CY_beta,CY_deltAileron,CY_deltRudder,CY_p,CY_r=var('CY_beta,CY_deltAileron,CY_deltRudder,CY_p,CY_r')
CY_beta=-0.83
CY_deltAileron=-0.075
CY_deltRudder=0.1914
CY_p=0
CY_r=0
#Cm_0,Cm_alpha,Cm_deltFlap,Cm_deltElevator,Cm_dotAlpha,Cm_q,Cm_Mach=var('Cm_0,Cm_alpha,Cm_deltFlap,Cm_deltElevator,Cm_dotAlpha,Cm_q,Cm_Mach')
Cm_0=0.135
Cm_alpha=-2.7397
Cm_deltFlap=0.0467
Cm_deltElevator=-0.9918
Cm_dotAlpha=-10.3796
Cm_q=-38.2067
Cm_Mach=0
#Cl_beta,Cl_deltAileron,Cl_deltRudder,Cl_p,Cl_r=var('Cl_beta,Cl_deltAileron,Cl_deltRudder,Cl_p,Cl_r')
Cl_beta=-0.13
Cl_deltAileron=-0.1695
Cl_deltRudder=0.0024
Cl_p=-0.5051
Cl_r=0.2519
#Cn_beta,Cn_deltAileron,Cn_deltRudder,Cn_p,Cn_r=var('Cn_beta,Cn_deltAileron,Cn_deltRudder,Cn_p,Cn_r')
Cn_beta=0.0726
Cn_deltAileron=0.0108
Cn_deltRudder=0.-0.0693
Cn_p=-0.069
Cn_r=-0.0946
################ISA for Troposhere #############
T0=288.15 # sea level tempreture ,k (15 centigree)
P_atm0=101325# N/m**2
R=287.04 #Characteristic gas constant (J/Kg/K)
gamma=1.4 #Ratio of specific heats
h=1000
T=T0-6.5*h/1000
P_atm=P_atm0*(1-0.0065*h/T0)**5.2561
rho=P_atm/(R*T)
speedofsound=(T*R*gamma)**0.5
####################################33
#uw,vw,ww=var('uw,vw,ww')#wind speed
uw=0
vw=0
ww=0
ua,va,wa=Matrix(3,1,[u,v,w])-H_I2B*Matrix(3,1,[uw,vw,ww])
#alpha,beta,Va,Mach=var('alpha,beta,Va,Mach')
Va=(ua**2+va**2+wa**2)**0.5
alpha=atan(wa/ua)
beta=asin(va/ua)
Mach=Va/speedofsound
q_bar=rho*Va**2/2
#CL,CD,CY_w,Cm,Cl,Cn=var('CL,CD,CY,Cm,Cl,Cn')
CL=CL_0+CL_alpha*alpha+CL_deltFlap*deltFlap+CL_deltElevator*deltElevator+(CL_dotAlpha*dotAlpha+CL_q*q)*c/(2*Va)+CL_Mach*Mach
#CD=CD_0+(CL-CL_minD)**2/(pi*e*AR)+CD_deltFlap*Abs(deltFlap)+CD_deltElevator*Abs(deltElevator)+CD_deltAileron*Abs(deltAileron)+CD_deltRudder*Abs(deltRudder)+CD_Mach*Mach
CD=CD_0+(CL-CL_minD)**2/(pi*e*AR)+CD_deltFlap*(deltFlap)+CD_deltElevator*(deltElevator)+CD_deltAileron*(deltAileron)+CD_deltRudder*(deltRudder)+CD_Mach*Mach
CY_w=CY_beta*beta+CY_deltAileron*deltAileron+CY_deltRudder*deltRudder+(CY_p*p+CY_r*r)*b/(2*Va)
Cm=Cm_0+Cm_alpha*alpha+Cm_deltFlap*deltFlap+Cm_deltElevator*deltElevator+(Cm_dotAlpha*dotAlpha+Cm_q*q)*c/(2*Va)+Cm_Mach*Mach
Cl=Cl_beta*beta+Cl_deltAileron*deltAileron+Cl_deltRudder*deltRudder+(Cl_p*p+Cl_r*r)*b/(2*Va)
Cn=Cn_beta*beta+Cn_deltAileron*deltAileron+Cn_deltRudder*deltRudder+(Cn_p*p+Cn_r*r)*b/(2*Va)
H_b2w=Matrix([[cos(alpha)*cos(beta),sin(beta),sin(alpha)*cos(beta)],
[-cos(alpha)*sin(beta),cos(beta),-sin(alpha)*sin(beta)],
[-sin(alpha),0,cos(alpha)]])
#CX,CY,CZ=var('CX,CY,CZ')
CX,CY,CZ=H_b2w*Matrix(3,1,[-CD,CY_w,-CL])
##############Fixed-pitch propeller##############333
#Jar,CT,CP=var('Jar,CT,CP')
omega=var('omega')
#propeller radius
R_prop=0.254# m
Jar=pi*Va/(omega*R_prop)
#coefficient of thrust (CT) and power (CP)
#the fomular is got after curve fitting using quadratic polynomial
CT=-0.02162763*Jar**2-0.03491274*Jar+0.03787723
CP=-0.01860428*Jar**2-0.01512463*Jar+0.02509024
F_prop=4*rho*R_prop**4*omega**2*CT/pi**2
M_prop=-4*rho*R_prop**5*omega**2*CP
##################Piston engine###################
thr=var('thr')
MAPmin=60;
MAP=thr*(P_atm/1000-MAPmin)+MAPmin
RPM=omega*30/pi
#the fomulas of fuel flow and power of piston are got using polynomial surface fitiing in Matlab
Fuelflow=-3189+0.2615*RPM+119.6*MAP-0.00001329*RPM**2-0.005922*RPM*MAP-1.843*MAP**2+3.257/10**10*RPM**3+1.377/10**7*RPM**2*MAP+0.00003562*RPM*MAP**2+0.006149*MAP**3
Power_P=-10600+1.38*RPM+367.1*MAP-0.0000768*RPM**2-0.03094*RPM*MAP-4.202*MAP**2+3.727/10**9*RPM**3+3.917/10**7*RPM**2*MAP+0.0002021*RPM*MAP**2+0.01572*MAP**3
#Power_P=432.4-0.3574*RPM-4.54*MAP+0.000005236*RPM**2+0.004861*RPM*MAP
#Fuelflow,Power_P=var('Fuelflow,Power_P')
#Power_P=var('Power_P')
power_corrected=(T0/T)**0.5*Power_P
M_eng=power_corrected/omega
###### engine total force and moment#########
J_eng=0.001# engine shaft moment of inertia
J_prop=0.002# propeller moment of inertia
MomentofInertiaofEngAndProp=(M_eng+M_prop)/(J_eng+J_prop)
#omega=integrate(MomentofInertiaofEngAndProp,omega)
#omega2=integrate(MomentofInertiaofEngAndProp,omega)
#without consider the moment caused by proleller force
Tx=F_prop
Ty=0
Tz=0
M_Tx=-M_eng
M_Ty=0
M_Tz=0
#############equations of motion################
#Ixx,Iyy,Izz,Ixz=var('Ixx,Iyy,Izz,Ixz')
#gross moment of inertia
Ixx=0.8244# kg*m**2
Iyy=1.135# kg*m**2
Izz=1.759# kg*m**2
Ixz=0.1204# kg*m**2
X=CX*q_bar*S+Tx
Y=CY*q_bar*S+Ty
Z=CZ*q_bar*S+Tz
L=Cl*q_bar*S*b+M_Tx
M=Cm*q_bar*S*c+M_Ty
N=Cn*q_bar*S*b+M_Tz
u_dot=X/m+gx+r*v-q*w
v_dot=Y/m+gy-r*u+p*w
w_dot=Z/m+gz+q*u-p*v
p_dot=(Izz*L+Ixz*N-(Ixz*(Iyy-Ixx-Izz)*p+(Ixx**2+Izz*(Izz-Iyy))*r)*q)/(Ixx*Izz-Izz**2)
q_dot=(M-(Ixx-Izz)*p*r-Ixz*(p**2-r**2))/Iyy
r_dot=(Ixz*L+Ixx*N+(Ixz*(Iyy-Ixx-Izz)*r+(Ixz**2+Ixx*(Ixx-Iyy)*p)*q))/(Ixx*Izz-Ixz**2)
x_I_dot=cos(theta)*cos(psi)*u+(-cos(phi)*sin(psi)+sin(phi)*sin(theta)*cos(psi))*v+(sin(phi)*sin(psi)+cos(phi)*sin(theta)*cos(psi))*w
y_I_dot=cos(theta)*sin(psi)*u+(cos(phi)*cos(psi)+sin(phi)*sin(theta)*sin(psi))*v+(-sin(phi)*cos(psi)+cos(phi)*sin(theta)*sin(psi))*w
z_I_dot=-sin(theta)*u+sin(phi)*cos(theta)*v+cos(phi)*cos(theta)*w
phi_dot=p+(q*sin(phi)+r*cos(phi))*tan(theta)
theta_dot=q*cos(phi)-r*sin(phi)
psi_dot=(q*sin(phi)+r*cos(phi))*sec(theta)
############# Trim for straight and level flight ############
###the aircraft is trimmed at
Va25=Va-25
#deltFlap=0
#deltAlpha=0
#straight level fight means
#phi=0
#p=0
#r=0
###Initial seed value for solver
#q=0
#deltElevator=0
#deltAileron=0
#deltRudder=0
#thr=0.5
#u=25
#v=0
#w=0
#omega=5236
#theta=0
#psi=0
###solve
u_dot_=u_dot.subs({deltElevator:0,deltAileron:0,deltRudder:0,deltFlap:0,dotAlpha:0,omega:545.4,thr:0.07063})
v_dot_=v_dot.subs({deltElevator:0,deltAileron:0,deltRudder:0,deltFlap:0,dotAlpha:0,omega:545.4,thr:0.07063})
w_dot_=w_dot.subs({deltElevator:0,deltAileron:0,deltRudder:0,deltFlap:0,dotAlpha:0,omega:545.4,thr:0.07063})
p_dot_=p_dot.subs({deltElevator:0,deltAileron:0,deltRudder:0,deltFlap:0,dotAlpha:0,omega:545.4,thr:0.07063})
q_dot_=q_dot.subs({deltElevator:0,deltAileron:0,deltRudder:0,deltFlap:0,dotAlpha:0,omega:545.4,thr:0.07063})
r_dot_=r_dot.subs({deltElevator:0,deltAileron:0,deltRudder:0,deltFlap:0,dotAlpha:0,omega:545.4,thr:0.07063})
phi_dot_=phi_dot.subs({deltElevator:0,deltAileron:0,deltRudder:0,deltFlap:0,dotAlpha:0,omega:545.4,thr:0.07063})
theta_dot_=theta_dot.subs({deltElevator:0,deltAileron:0,deltRudder:0,deltFlap:0,dotAlpha:0,omega:545.4,thr:0.07063})
psi_dot_=psi_dot.subs({deltElevator:0,deltAileron:0,deltRudder:0,deltFlap:0,dotAlpha:0,omega:545.4,thr:0.07063})
#omega_=omega.subs([p,r,phi,deltFlap,deltAlpha],[0,0,0,0,0])
#result=nsolve([Va25,u_dot,v_dot,w_dot,p_dot,q_dot,r_dot,phi_dot,theta_dot,psi_dot,omega],
# [q,deltElevator,deltAileron,deltRudder,thr,u,v,w,omega,theta,psi],
# [0,0,0,0,0.5,25,0,0,5236,0,0])
#result=nsolve([u_dot_,v_dot_,w_dot_,p_dot_,q_dot_,r_dot_,phi_dot_,theta_dot_,psi_dot_],
# [q,deltElevator,deltAileron,deltRudder,u,v,w,theta,psi],
# [0.000,0.0000,0.00000,0.0000,25.0,0.0000,0.00000,0.00000,0.00000])
result=nsolve([u_dot_,v_dot_,w_dot_,p_dot_,q_dot_,r_dot_,phi_dot_,theta_dot_,psi_dot_],
[q,r,p,phi,u,v,w,theta,psi],
[0.000,0.0000,0.00000,0.0000,2.0,0.0000,0.00000,0.00000,0.00000])