How to implement a integral in c source code

Question

I want to implement the flux observer from matlab ( https://de.mathworks.com/help/mcb/ref/fluxobserver.html ) in c code (for an stm32). In order to do so, I need to calculate the integral for flux calculation. However, since Im a hobbyist, i dont know how to implement this in source code (neither how to calculate it by hand).

ψα= ∫(Vα−IαR)dt− (Ls⋅Iα)

This is the term I am talking about. Any help about this topic is highly recommended.

Thanks

EDIT: Thats what i tried:

    if(TimerFlag)
    {
        TimerFlag = 0;

        ClarkTransformation(&ialpha, &ibeta, cur_c, cur_b);
        ClarkTransformation(&valpha, &vbeta, vol_c, vol_b);

        dt = TimeElapsedS - TimeElapsedSOld;
        TimeElapsedSOld = TimeElapsedS;

        fluxalpha += ((valpha-ialpha*R)*dt - (Ls*ialpha));
        fluxbeta += ((vbeta-ibeta*R)*dt - (Ls*ibeta));

        fluxrotor = sqrtf((fluxalpha*fluxalpha) + (fluxbeta*fluxbeta));
        torquemotor = (3.0f / 2.0f) * PoleNumber * (fluxalpha*ibeta - fluxbeta*ialpha);
        anglemotor = arctan(fluxbeta/fluxalpha);
    }

I'm afraid this is too broad. Do you know how to calculate I(t) and V(t)? Do you know what an integral is and how to calculate it numerically? — Bob__
– Bob__, Commented Sep 30, 2022 at 10:52
i tried summing it up in every loop (10kHz). But this made my flux variable just go off in negative direction... what do you mean by I(t) and V(t)? If you mean voltage and current at given times, yes I do have these variables correctly in my code. — Christoph Madl
– Christoph Madl, Commented Sep 30, 2022 at 10:58
Can you please add a minimal reproducible example of your attempt? — Bob__
– Bob__, Commented Sep 30, 2022 at 11:00

Spektre · Accepted Answer · 2022-09-30 16:45:49Z

1

discrete integral is just summation (rectangular rule) so you just add up the stuff for each sample like you did however You have also constant term which must not be added more than once... I see it like this:

// some globals and or init
float fluxalpha= -Ls*ialpha;
float fluxbeta = -Ls*ibeta;

// this is in your timer ISR or whatever
void some_timer_event()
 {
 float dt = elapsed_time();
 fluxalpha += (valpha-ialpha*R)*dt; 
 fluxbeta  += (vbeta-ibeta*R)*dt;
 }

answered Sep 30, 2022 at 16:45

Spektre

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