Pozor na chybu v Application Note AVR221 (Discrete PID controller) od Atmelu

[Jakub Ladman]

Doporucuji odeslat toto upozorneni a reseni panum do atmelu.
verim ze radi provedou opravu primo v appnote.
Pomuze to tak asi nejvice lidem.

Jakub Ladman

Dne Monday 02 of June 2008 13:02:37 Richard Kaliciak napsal(a):
> Dobry den,
>
> pri hladani vhodnych PID parametrov som narazil na zvlastne spravanie
> regulatora. K_I a K_D som nastavil na nulu, aby som mohol odhadnut
> vhodne K_P. Vsetko pekne fungovalo, ale po urcitej dobe vybehla
> riadiacia hodnota na maximum.
>
> Tymto chcem upozornit na chybu v programe pid.c z AVR221, ktora sa
> prejavi pri K_I=0. V povodnom texte je:
> ---------- begin ----------
>    // Calculate Iterm and limit integral runaway
>    temp = pid_st->sumError + error;
>    if(temp > pid_st->maxSumError){
>      i_term = MAX_I_TERM;
>      pid_st->sumError = pid_st->maxSumError;
>    }
>    else if(temp < -pid_st->maxSumError){
>      i_term = -MAX_I_TERM;
>      pid_st->sumError = -pid_st->maxSumError;
>    }
>    else{
>      pid_st->sumError = temp;
>      i_term = pid_st->I_Factor * pid_st->sumError;
>    }
> ---------- end ----------
>
> Po istej dobe naakumulovana chyba prekroci maxSumError a i_term sa
> nastavi na MAX_I_TERM, aj ked je I_Factor = 0. Po zmene programu na:
> ---------- begin ----------
>    // Calculate Iterm and limit integral runaway
>    temp = pid_st->sumError + error;
>    if(temp > pid_st->maxSumError){
>      i_term = MAX_I_TERM;
>      pid_st->sumError = pid_st->maxSumError;
>    }
>    else if(temp < -pid_st->maxSumError){
>      i_term = MIN_I_TERM;
>      pid_st->sumError = -pid_st->maxSumError;
>    }
>    else{
>      pid_st->sumError = temp;
>    }
>    i_term = pid_st->I_Factor * pid_st->sumError;
> ---------- end ----------
>
> to uz funguje ako sa patri.
>
> Richard Kaliciak
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