Mupaderror. What should i do ?

I am simulating any devicce.

If i delete the symbolic which are l_u V_20 A E r J_2 b l_r Jeq lnf_r, the message of error using mupadmex be seen.

Error using mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.

If the input expression contains a symbolic variable, use the VPA function instead.

Error in sym/double (line 702)
        Xstr = mupadmex('symobj::double', S.s, 0);

Error in the_constant_reduced_orders_dancer (line 41)
G_1=double(G_1)
t=0:0.01:20;

%the constant of transfer function of A

l_1=2.2; % upstream spaln length 

l_2=3.2; % downstream span length 

A= 1; % m^2 cross-direction area

E=2.75*10^9;   % elastic of modulus

Jeq=1.004;   % inertia of moment

J_1=5.4 ;J_2 = 4.66; % inertia of rod, inertia of arm

r=0.163;   % roll radius

b= 1;   % bearing friction 

Kp=0.08; % k gain

Tn= 1000;   %

%V=5 % reference of dancer position(voltage)

Inf_r=0.163 ;% diameter of infeeding roller

inf_c=0.5121; % circumference of infeeding roller

pri_C=0.66; % circumference of printing roller

N = 100; % operating tension 

V_10=4.9;

l_u=0.15; % rol length to cylinder

l_r=0.3;  % rod length to roll

V= 5; % operation velocity m/min

V_20=5; % operation veloctiy of upstream

V_30=5.1; % operation velocity of downstream 

width=1; % m , width of substrate

thickness= 12 *10^-6; % thickness of substrate micrometer
syms s l_u V_20 A E r J_2 b l_r Jeq lnf_r

A(s)=s*l_u+V_20+(2*A*E*r^2)/(s*J_2+b); %%transfer function of A

B(s)=(-A*E*r^2)/(s*J_2+b)*l_2*(Jeq*s^2+s*b+24/0.078*l_u^2)+A*E*s*l_r; % transfer function of B

C(s)=s*l_2+V_20+V_30+(2*A*E*r^2)/(s*J_2+b); % transfer function C

D(s)=-1/l_r*(Jeq*s^2+s*b+24/0.078*l_u^2)*(s*lnf_r+V_30+(A*E*r^2)/(s*J_2+b)-A*E*s*l_r); % transfer function of D

E(s)=-1/l_r*(Jeq*s^2+s*b+24/0.078*l_u^2)*(V_10+(A*E*r^2)/(s*J_2+b)+A*E*s*l_r); % transfer function of E

G_1= -A*E*C(s)/(D(s)*A(s)-B(s)*C(s)); % transfer function of (1)

G_2= -A*E*E(s)/(D(s)*A(s)-B(s)*C(s)); % transfer function of (2)

G_1=double(G_1)

sys=tf(G_1);

step(sys)

What should i do to simulate in the script?