Solving state space equation using matlab function block in simulink

Hi, Im trying to model a synchronous machine. My present situation is, i know the A, B, C, D values and my input signal is coming from other blocks which are voltages, speed etc. State variable in my case is flux. I need to find this flux value so as to find derive current, torque etc. So how to solve this state space equation to get the state variable. I tried to read many examples but im not able to find the one I need. Any help is appreciable

Answer 1

[Sebastian Castro]

If you already know the A, B, C, D matrices, why not use a State-Space Simulink block, then?

- Sebastian

[leonn alexander]

But i don't know how to use that block. And one more thing i forgot to say is, i have the equation xdot= Ax + Bu only with me. Im not concerned about y. So, i can give an input which will act as "u" in the equation, but i have to get "x", the state variable, as output. So can I use y=x as the second equation which will give me C=1 and D=0 and is that the way to do it?

[Sebastian Castro]

That block takes in the A, B, C, D matrices as MATLAB matrices -- not much to it!

Also yes, if y = x, then your C and D matrices are 1 and 0 respectively, as you said. For example, if your A matrix is 4x4, your C matrix is the 4-dimension identity matrix: In MATLAB, eye(4).

[Mahmoud Aly]

If the state space matrix are function of variable which is varying, what is the best way to solve the state?

[Sam Chak]

Hi @Mahmoud Aly

For single-variable systems such as , you can use the Fcn block to apply the nonlinear function to its input (state variable x and input signal u). After that, connect the Fcn block to an Integrator block, which implies the output . Before clicking the Run button, specify the initial value in the Integrator block.

For multivariate systems, , with the state vector and input vector , you can use n sets of Fcn and Integrator pairs, or one MATLAB Function block and an Integrator block.

[Paul]

Check out Varying State Space as well.