I am implementing a H2/LQG controller to get the optimum force. In simulink I am using Matlab function block. The error in this block I am getting is

function y = fcn(u1,u2) coder.extrinsic('Controlle'); y=0; y=Controlle(u1,u2) end

The code for controlle is as given below:- function OCF=Controlle(M,t) syms s M=M.*(1/s); k=10^5*[12 -6.84 0;-6.84 13.7 -6.84;0 -6.84 6.84]; m=[98.3 0 0;0 98.3 0;0 0 98.3]; c=[175 -50 0;-50 100 -50;0 -50 50]; Ga=50; Gc=[-1;0;0]; Lc=[1;1;1]; Ec=-[0;0;0;Lc]; Ac=[zeros(3,3) eye(3);-inv(m)*k -inv(m)*c]; Bc=[0;0;0;inv(m)*Gc]; Cc=[-inv(m)*k -inv(m)*c;1 0 0 0 0 0]; Dc=[inv(m)*Gc;0]; Qc=[0 0 0 0;0 0 0 0;0 0 1 0;0 0 0 0 ]; r1=1e-17; [P]=care(Ac,Bc,Cc'*Qc*Cc,r1); K=(Bc'*P)/r1; [S]=care(Ac,Cc',Ga*Ec*Ec'); Lr=(Cc*S)'; fc=ilaplace((K*inv(s*eye(6,6)-(Ac-Lr*Cc))*([Lr (Bc-Lr*Dc)])*M),s,t); OCF=vpa(fc,3); end

ERROR:- MATLAB Function Interface Error: MATLAB expression 'Controlle' is not numeric. Block Controller/MATLAB Function1 (#22) While executing: none

[Ryan Livingston]

Please see the tutorial on how to format code in questions:

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

Answer 1

[Ryan Livingston]

In fcn the output variable is declared to be a real double scalar in:

y=0;

However, the output of the function Controlle is from the vpa function which returns a symbolic value:

>> f = vpa(10)

f =

10.0

>> class(f)

ans =

sym

The data type, size, and complexity in the assignment y=0 needs to match the value returned by the extrinsic function being called ( Controlle in this case).

You can use Symbolic and vpa computations in the function being called extrinsically but:

1. If pre-assigning to y, as in y=0, y must be a data type supported for code generation. See data definition doc for more info.
2. If y is left without the pre-assignment, y=0, you will be able to pass y to other extrinsic functions but will not be able to return it from the MATLAB Function Block or do many other things with it.

The choice depends upon what you want to do with the output of Controlle.

Lastly, there is more documentation on extrinsic functions that cover what I've said in much more detail.

[siddharth]

Dear Ryan Livingston,

Thank you for the reply.

How can I then implement the code. Part of my project is in Simulink, and some part is in matlab.

The problem is I am not able to calculate Laplace and Laplace inverse in simulink.

The output of the Controlle function is to be used in the simulink model.

Its output should be of double format and not symbolic.

Can I convert my simulink mode in to matlab code?

[Ryan Livingston]

You could just make sure that the output of Controlle is a double. For example, you could change the last line to:

OCFvpa = vpa(fc,3);
OCF = double(fc);

Then in the MATLAB Function Block use:

function y = fcn(u1,u2)
coder.extrinsic('Controlle');
y=zeros(M,N);
y=Controlle(u1,u2)

where M and N describe the size of the array you expect Controlle to return.