Equations to Matlab code

Question

Maria 2014-11-18

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回答： Warren Dennis 2020-2-17

hi

I want to convert the two equations below into Matlab code , I wrote the function below for that and I don't know if that is correct or not , specially the integral form ? any help ?

    function [VI,Vw]= Modelfun(TL,TR)
    dt=0.01; %sampling time
    r=0.052;
    L=0.306;
    M=9;
    I=5;
    VI=(TL+TR)/ M * r;
    VI=VI*dt/2; %first integral
    Vw=(L*(TL-TR)) / 2 * r * I;
    Vw=Vw*dt/2; %first integral
    Vw=Vw*dt/2; %second integral
    end

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Answer 1

Torsten 2014-11-20

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It is not possible simply to output (VI,Vw) given (TL,TR).

As input you need (VIold,Vwold,Vwdotold,dt,TL,TR).

The output VI,Vw and Vwdot is then calculated according to

VI=VIold+dt*(TL+TR)/(M*r)

Vw=Vwold+dt*Vwdotold

Vwdot=Vwdotold+dt*L*(TL-TR)/(2*r*I).

This would mean that your function "Modelfun" advances VI and Vw from their values at time t to time t+dt.

Best wishes

Torsten.

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Answer 2

Torsten 2014-11-18

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If the right-hand sides of your equations does not depend on t, the solution to your differential equations is explicitely given by

VI=VI0+(TL+TR)/(M*r)*t

Vw=Vw0+Vw0dot*t+0.5*L*(TL-TR)/(2*r*I)*t^2

where

VI0=VI at time t=0

Vw0=Vw at time t=0

Vw0dot = d/dt(Vw) at time t=0.

Best wishes

Torsten.

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Maria 2014-11-19

thanks a lot Torsten

Actually , I am not so good with Matlab and from my little bit understanding I built this function and I don't know if that right but generally what I want to do is to write the equations above in code form inside "Embedded MATLAB Function " block with two inputs(TL,TR) and two outputs (VI,Vw) as in figure above.

thanks

Maria 2014-11-20