# fsolve problem with syms var

2 views (last 30 days)
shahin hashemi on 23 Dec 2017
Commented: shahin hashemi on 24 Dec 2017
dear all
i write cod that i want to solve it with fsolve commend
at the end, my equations just contain double parameters but in the middle of my function i must consider some symbolic parameters that i remove them after some calculations
but when i run my function i got error : FSOLVE requires all values returned by functions to be of data type double and point the line i define my symbolic variable but i mention again that my final equation doesnt contain any of those symbolic var
is there any way to my problem
shahin hashemi on 23 Dec 2017
my final F is 3*1 matrix that only contain x1 x2 x3

Walter Roberson on 23 Dec 2017
Edited: Walter Roberson on 23 Dec 2017
It is not possible to do what you are asking to do.
I already told you what you need to do to solve this: you need to run your code symbolically, and then use matlabFunction to convert the resulting symbolic expressions to function handles.
shahin hashemi on 24 Dec 2017
thank you mr walter finaly my problem solved with your help
happy new year with best wishes

Matt J on 24 Dec 2017
Edited: Matt J on 24 Dec 2017
but i mention again that my final equation doesnt contain any of those symbolic var
But your final F is generated from calculations with these variables, so they inherit their symbolic type. At no point in your code, do you do anything to convert from symbolic to double. When I run your function on some sample input, I obtain
>> class(consnt7([1,1,1]))
ans =
'sym'
So, as you can see, your output is still of type sym.
but i remove them after some calculations with "collect" and "coeffs" commend
Nope. The output of these commands are still of type sym. I explained to you here (and you thanked me emphatically) that the commmand double() was the way to convert from sym to double.
shahin hashemi on 24 Dec 2017
and i should say i do what you say befor and i can run cod for N=1
function F = consnt4(x)
m=1.669e-3;
jx=5.743e-14;
E=2.1e11;
O=12.5e-3;
jz=1.149e-13;
G=8e10;
L=3e-3;
g=9.81;
N=3;
T1=2;
T2=1;
T3=0.5;
r1=[1*O;0;0;];
r2=[(-1/2)*O;(sqrt(3))*O/2;0];
r3=[(-1/2)*O;-(sqrt(3))*O/2;0];
pl=L*[(cos(x(1))*(1-cos(x(2))))/x(2) (sin(x(1))*(1-cos(x(2))))/x(2) sin(x(2))/x(2)]';
wk=[0 -sin(x(1)) cos(x(1))*sin(x(2));0 cos(x(1)) sin(x(1))*sin(x(2));1 0 cos(x(2))];
vk=L*[-sin(x(1))*((1-cos(x(2)))/x(2)) (cos(x(1))/x(2)^2)*(sin(x(2))*x(2)-(1-cos(x(2)))) 0;cos(x(1))*((1-cos(x(2)))/x(2)) (sin(x(1))/(x(2)^2))*((sin(x(2))*x(2))-(1-cos(x(1)))) 0;0 (cos(x(2))*x(2)-sin(x(2)))/(x(2)^2) 0];
R=[cos(x(1))*cos(x(2))*cos(x(3))-sin(x(1))*sin(x(3)) -cos(x(1))*cos(x(2))*sin(x(3))-sin(x(1))*cos(x(3)) cos(x(1))*sin(x(2));sin(x(1))*cos(x(2))*cos(x(3))+cos(x(1))*sin(x(3)) -sin(x(1))*cos(x(2))*sin(x(3))+cos(x(1))*cos(x(3)) sin(x(1))*sin(x(2));-sin(x(2))*cos(x(3)) sin(x(2))*sin(x(3)) cos(x(2))];
Mb=E*jx*((x(2))/L)*[1 0 0;0 1 0;0 0 1]*[-sin(x(1));cos(x(1));0];
Mt=-G*jz*(x(1)+x(3))*R(:,3)/L;
Me=Mb+Mt;
Fg=-m*g*[1;0;0];
ph(:,1)=[pl+R*r1-r1];
ph(:,2)=[pl+R*r2-r2];
ph(:,3)=[pl+R*r3-r3];
ap=[sqrt(ph(1,1)^2+ph(2,1)^2+ph(3,1)^2);sqrt(ph(1,2)^2+ph(2,2)^2+ph(3,2)^2);sqrt(ph(1,3)^2+ph(2,3)^2+ph(3,3)^2)];
f=[ph(:,1)/ap(1,1) ph(:,2)/ap(2,1) ph(:,3)/ap(3,1)];
Fc=[-T1*f(:,1) -T2*f(:,2) -T3*f(:,3)];
fa=Fc(:,1)+Fc(:,2)+Fc(:,3);
Ma=cross(r1,Fc(:,1))+cross(r2,Fc(:,2))+cross(r3,Fc(:,3));
feq=fa +Fg;
Meq=Ma+ Me;
F(1,:)= [dot(Meq,wk(:,1))+dot(feq,vk(:,1))];
F(2,:)= [dot(Meq,wk(:,2))+dot(feq,vk(:,2))];
F(3,:)= [dot(Meq,wk(:,3))+dot(feq,vk(:,3))];
and for fsolve :
x0=[0;0.1;0];
options = optimoptions('fsolve','Display','iter');
[x,fval] = fsolve(@consnt4,x0,options)
and now i try for N>1 that cause to appear xd
and now when i try your solution i mean using double(sub()) again i face with same error and i think i cant use syms in my main function that call by f solve and i should do it in smth like sub functions ?

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