How to solve Differential Equations in Simulink level 2 s function

equations:

dx/dt=V*cos(theta)*cos(psi)

dy/dt=V*sin(theta)

dz/dt=-V*cos(theta)*sin(psi)

According to the s function demo--- msfcndemo_limintm.mdl.

I wrote my s function code

...........

%%Setup Dwork
block.NumContStates = 3;

.........

function InitConditions(block)

%%Initialize Dwork
block.ContStates(1).Data = 0;
block.ContStates(2).Data = 0;
block.ContStates(3).Data = 0;
.......................

function Output(block)

block.OutputPort(1).Data = block.ContStates(1).Data;
block.OutputPort(2).Data = block.ContStates(2).Data;
block.OutputPort(3).Data = block.ContStates(3).Data;

%endfunction

function Derivative(block)

..................

block.Derivatives(1).Data =V*cos(theta)*cos(psi)
block.Derivatives(2).Data =V*sin(theta)
block.Derivatives(3).Data =-V*cos(theta)*sin(psi)

..................

when we run this model, the Error is: no ContStates method;

Answer 1

[Kaustubha Govind]

Change your InitConditions callback to:

function InitConditions(block)

%%Initialize Dwork
block.ContStates.Data(1) = 0;
block.ContStates.Data(2) = 0;
block.ContStates.Data(3) = 0;

Everything else looks good.

[knight]

Thanks

[majid taheri]

How should be define, if one state has more than one dimension?

[Juan Camilo Vega Nieto]

Thanks; It is possible to solve a differencial ecuation of order two in a Matlab level 2 S-function? thank you very much.

Answer 2

[knight]

Thanks Kaustubha Govind, Change the Initconditions callback and Derivatives callback to:

......................

function InitConditions(block)

%% Initialize Dwork

block.ContStates.Data(1) = 0;

block.ContStates.Data(2) = 0;

block.ContStates.Data(3) = 0;

function Derivative(block)

..................

block.Derivatives.Data(1) =V*cos(theta)*cos(psi)

block.Derivatives.Data(2) =V*sin(theta)

block.Derivatives.Data(3)=-V*cos(theta)*sin(psi)

..................

It's ok.