208 lines
5.1 KiB
C
208 lines
5.1 KiB
C
/* Copyright (C) 2013 Riccardo Greco rigreco.grc@gmail.com.
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*
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* This project is based on 1999-2000 Thesis work of Greco Riccardo.
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* It implement an Runge Kutta 4(5)^ order integration numerical method of differential equations set
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* by use of double precision floating point operation in Aztec C65 language.
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* It allow to simulate different mathematical models such as:
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* Resistance Capacitor electrical circuit, Direct Current electric motor,
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* Alternative Current three phase induction motor.
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*
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* Thanks to Bill Buckels for his invaluable support:
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* Aztec C compilers http://www.aztecmuseum.ca/compilers.htm
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*/
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/* PROCESS MODULE */
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#include <math.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <errno.h>
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#define chk 1 /* set chk to 1 charge */
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#define rk4r 5.0e-3 /* RK4 max resolution h<rk4r */
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/* GENERAL GLOBAL */
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extern double sur,r,c,tau,h,time,time2,yinit,keep;
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extern char fbuf[80];
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extern int cnt,fd;
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extern struct data {
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char v[20];
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char i[20];
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char ideal[20];
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};
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/* LOCAL GLOBAL */
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char *outr[4]={"t="," vc(t)="," vcerr(t)="," i(t)="};
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char *FILE_NAME="rcrk";
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double swi;
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/* Functions sets */
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int funrk(x,y,frk)
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double x,y,*frk;
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{
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frk[0] = (double)(((sur*swi)-y)/tau); /* RC Circuit Voltage frk[0]=vc'(t) Charge differential equation */
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} /* vc'(t)=(1/RC)*(E-vc(t)) charge*/
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/* vc'(t)=(1/RC)*(-vc(t)) discharge */
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double current(v)
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double(v);
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{
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return(((sur*swi)-v)/r); /* i(t)=(E-vc(t))/R charge*/
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} /* i(t)=(-vc(t))/R discharge */
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double exact(x)
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double(x);
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{
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return (((yinit-sur)*exp(-x/tau))+sur); /* Exact solution charge vc(t)=(vc(0)-E)*exp(-t/RC)+E */
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}
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double exact2(x)
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double (x);
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{
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return (keep*exp(-x/tau)); /* Exact solution discharge vc(t)=(vc(td))*exp(-t/RC) */
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}
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/*RK4 Module */
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int runge_kutta(x,y,h,y3)
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double x,y,h,*y3;
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{
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double r1,r2,r3,r4,r5,h1,err,y3err,y3div,frk,frkerr;
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/* RK inizialization */
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y3[0] = (double)0.0;
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y3err = (double)2.0;
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y3div = (double)6.0;
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frk = (double)0.0;
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frkerr = (double)0.5;
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err=(double)0.0;
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do
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{
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h1=(double)0.5*h;
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funrk(x,y,&frk); /* 1^ order */
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r1=h*frk;
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funrk(x+h1,(double)y+frkerr*r1,&frk); /* 2^ order */
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r2=h*frk;
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funrk(x+h1,(double)y+frkerr+r2,&frk); /* 3^ order */
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r3=h*frk;
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funrk(x+h,(double)y+r3,&frk); /* 4^ order */
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r4=h*frk;
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funrk(x+h,(double)y+r4,&frk); /* 5^ order */
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r5=h*frk;
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err=fabs(r4-r5); /* etimate the error */
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h=h/2;
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}
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while (err>rk4r); /* RK4 max resolution */
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/* y3 plus weighted average of operators 4^ order */
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y3[0] = (double)(y+(r1+y3err*r2+y3err*r3+r4)/y3div);
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}
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ovmain()
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{
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char buf[20],rev;/*conv[4]*/
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double atof(); /* DON'T FORGET THIS */
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double x,x2,nc,y3,y,errtx,cur,exa;
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struct data rk;
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/* inizialization */
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cnt=(int)0.0; /* Reset counter */
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y3 = (double)0.0;
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x=(double)0.0; /* time simulation */
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x2=(double)0.0; /* time discharge */
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keep=(double)0.0;
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swi=(double)1.0; /* switch set to 1 = charge */
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y=yinit; /* set initial condition parameter vc(o) */
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/* Start simulation */
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scr_clear();
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scr_curs(0,0);
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puts("Pocessing...");
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/* open and write header data to file */
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open(FILE_NAME,O_WRONLY|O_APPEND,0xC3);
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write(fd,fbuf,80);
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buf[0]='\0'; /* buffers reset */
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fbuf[0]='\0';
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/* RK main Cycle */
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while (x<time) {
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runge_kutta(x,y,h,&y3);
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cur=current(y3);
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if (x <= time2)
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{
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exa=(double)exact(x);
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errtx=(double)fabs(y3-exa); /* exact solution in charge */
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}
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if (x > time2)
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{
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if (chk)
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{
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swi=(double)0.0; /* switch set to 0 = discharge */
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keep=(double)y3; /* keep the value of vc(td) in the istant of discharge */
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!chk; /* NOT chk */
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}
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exa=(double)exact2(x2);
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errtx=(double)fabs(y3-exa); /* exact solution in discharge */
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x2=x2+h;
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}
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/* store output in buffer */
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ftoa(x,buf,6,2);
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strcat(fbuf,outr[0]);
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strcat(fbuf,buf); /* store time (x) */
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ftoa(y3,buf,6,2);
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strcat(fbuf,outr[1]);
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strcat(fbuf,buf); /* store voltage vc(t) (y3) */
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ftoa(errtx,buf,6,2);
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strcat(fbuf,outr[2]);
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strcat(fbuf,buf); /* store voltage error vcerr(t) (errtx) */
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ftoa(cur,buf,6,2);
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strcat(fbuf,outr[3]);
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strcat(fbuf,buf); /* store current i(t) (cur) */
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/* converting using max floating resolution */
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ftoa(y3,rk.v,14,1); /* vc(t) */
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ftoa(cur,rk.i,14,1); /* i(t) */
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ftoa(exa,rk.ideal,14,1); /* vc(t) exact solution */
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puts(fbuf); /* output to screen */
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/* write data result to file */
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write(fd,rk.v,20); /* write vc(t) */
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write(fd,rk.i,20); /* write i(t) */
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write(fd,rk.ideal,20); /* write vc(t) exact solution */
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fbuf[0]='\0'; /* reset buffer */
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y=y3;
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x=x+h;
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cnt++; /* renew counter */
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}
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close(fd); /* close the data file */
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/*printf("Cycles number= %d",(cnt-1)); /* NOT YET itoa ? */
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puts("Press any key to start plotting...");
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getch();
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return 0;
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}
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