[123doc.vn] Lap Trinh Robot Tu Dong Don Gian Voi Vdk Pic16f877a

Lp Trnh RoBot T ng n Gin Vi VK PIC16F877A

Tm tt

Ti liu hng dn lp trnh cho robot t ng d ng theo vch trng v iu khin cc c cu (nng h, gp nh qu) mt cch c bn

nht.Vi iu khin c s dng trong ti liu l PIC16F877A ca Microchip.Lp trnh bng ngn ng C vi trnh bin dch CCS.

1 TM TT V THIT K ROBOT T NG

Robot t ng trong cc cuc thi Robocon gm 3 thnh phn chnh: C kh, Mch in t, Lp trnh.

1.1 C kh

Mt robot n gin gm 2 ng c truyn ng cho 2 bnh xe bn tri v bn phi gip robot di chuyn. Pha trc c th l 1 hoc 2 bnh t do

(bnh t la, omni, mt tru,). thc hin c cc cng vic nh nng h trc, gp nh y qu, robot c trang b thm cc ng c khc

truyn ng cho cc c cu ny.

Tt c cc b phn trn c b tr trn mt khung bng nhm, st,

Phn hng dn chi tit v thit k c kh s c trnh by trong mt ti liu khc. Ti liu ny ch tp trung vo phn lp trnh.

M hnh robot d dng n gin

1.2 Mch in t

S hot ng ca robot t ng

1.2.1 Mch ng vo (cm bin, nt n, cng tc hnh trnh)

Vi robot n gin, ng vo thng l mc logic ly t cm bin quang (quang tr, quang diode), nt n hoc cng tc hnh trnh. T mch

vi iu khin x l cc tn hiu ny xut ng ra (thng l ng c DC) choph hp.

Cm bin quang phi c che chn cn thn hn ch nh hng t ccngun nh sng bn ngoi.

Mch cm bin, nt n v cng tc hnh trnh

1.2.2 Mch vi iu khin

Mch s dng vi iu khin PIC16F877A ca Microchip. Mch nhn tn hiu t ng vo, x l v xut ng ra qua mt mch cch ly bng opto

ra mch cng sut.

Mch vi iu khin

1.2.3 Mch cng sut iu khin ng c DC

Mt s mch thng dng:

Mch cng sut s dng 1 FET v 1 relay

Mch cu H iu khin ng c vi Half Bridge Driver IR2184

1.3 Lp trnh

y l phn chnh ca ti liu ny. Ngn ng lp trnh c s dng l C, vi trnh bin dch CCS cho vi iu khin PIC ca Microchip.

Kin thc ban u: Lp trnh C cn bn

Cc ti liu tham kho:

Ti liu CCS ting Vit.

y l cc ti liu cn c qua trc khi vo lp trnh cho PIC c th bit cc hm nhn tn hiu ng vo, xut tn hiu ng ra, ngt, timer,

counter, PWM,

Cc hm quan trng s c nhc li phn 2.

2 LP TRNH CHO ROBOT T NG D NG N GIN

Chng trnh gip robot chy theo vch trng trn nn mu sm.

2.1 Phn cng

8 cm bin quang d ng

Mch cng sut iu khin 2 ng c

Mch vi iu khin:

o PORTD: ni vi tn hiu ra ca 8 cm bin

o ng c tri:

Chn C0: iu khin chiu (DIR_LEFT)

Chn C1: iu khin cho php chy (EN_LEFT)

o ng c phi:

Chn C3: iu khin chiu (DIR_RIGHT)

Chn C2: iu khin cho php chy (EN_RIGHT)

(Cc ng vo v ng ra c th ni vi bt c PORT v chn no ca vi iu khin)

2.2 Nguyn tc iu khin

2.2.1 iu khin ng c

Tng t i vi cc ng c iu khin cc c cu.

2.2.2 Hng di chuyn ca robot

2.2.3 X l tn hiu cm bin (xem hnh v)

Mc ch ca vic d ng l hng cho robot i theo 1 vch thng mu trng trn mt nn mu m (en, xanh,)

Cm bin c t gia robot.

o Khi cm bin s 3,4 nm trn vch trng (mc 1): robot chy thng

o Khi robot lch sang tri: quay phi iu chnh robot v ng vch

o Khi robot lch sang phi: quay tri iu chnh robot v ng vch

Cc mc lch ra khi vch trng ca robot

2.3 Chng trnh iu khin

#include

#include

#fuses HS,NOWDT,NOPROTECT,NOLVP

#use delay(clock=20000000)

/* NH NGHA CC CHN V PORT */

#define DIR_LEFT RC0

#define EN_LEFT RC1

#define DIR_RIGHT RC3

#define EN_RIGHT RC2

#define SENSOR PORTD

/* KHAI BO CC CHNG TRNH CON */

void motor_left_forward();

void motor_left_reverse();

void motor_left_stop();

void motor_right_forward();

void motor_right_reverse();

void motor_right_stop();

void forward();

void reverse();

void stop();

void turn_left();

void turn_right();

/* CC CHNG TRNH CON */

// ng c tri chy thun

void motor_left_forward()

{

DIR_LEFT=1; // chiu thun

EN_LEFT=1; // cho php chy

}

// ng c tri chy ngc

void motor_left_reverse()

{

DIR_LEFT=0; // chiu ngc

EN_LEFT=1; // cho php chy

}

// ng c tri dng

void motor_left_stop()

{

EN_LEFT=0; // khng cho php chy

}

// ng c phi chy thun

void motor_right_forward()

{

DIR_RIGHT=1;// chiu thun

EN_RIGHT=1; // cho php chy

}

// ng c phi chy ngc

void motor_right_reverse()

{

DIR_RIGHT=0;// chiu ngc

EN_RIGHT=1; // cho php chy

}

// ng c phi dng

void motor_right_stop()

{

EN_RIGHT=0; // khng cho php chy

}

// Chy thng

void forward()

{

motor_left_forward();

motor_right_forward();

}

// Chy li

void reverse()

{motor_left_reverse();

motor_right_reverse();

}

// Dng

void stop()

{

motor_left_stop();

motor_right_stop();

}

// Quay tri

void turn_left()

{

motor_left_forward();

motor_right_reverse(); // hoc motor_right_stop();

}

// Quay phi

void turn_right()

{

motor_left_reverse(); // hoc motor_left_stop();

motor_right_forward();

}

/* CHNG TRNH CHNH */

void main ()

{

TRISC=0x00; // PORTC l ng ra ( ng c)

TRISD=0x00; // PORTD l ng vo (cm bin quang)

PORTC=0x00; // Khi to gi tr ban u 0x00 cho PORTC

while(1)

{

switch (SENSOR)

{

case 0b00011000: forward(); break;

case 0b00001100: turn_left(); break;




case 0b00110000: turn_right(); break;




}

}

}

3 CI TIN CHNG TRNH D NG

3.1 iu khin tc ng c vi cc trng thi lch khi vch trng

3.1.1 Nguyn l

i vi chng trnh d ng n gin, khi robot lch tri hoc lch phi, robot s quay phi hoc quay tri iu chnh cho d lch t hay

lch nhiu. Nh vy, trong qu trnh di chuyn, robot s lc lin tc v phi quay tri, quay phi lin tc. Do , vi cc mc lch ra khi vch

trng khc nhau, ta iu chnh tc 2 bnh tri, phi cho ph hp qu trnh di chuyn theo vch ca robot c nhuyn v mt hn.

Bng gi tr tham kho tc ng c tri v ng c phi tng ng vi cc trng thi lch khi vch trng ca robot:

3.1.2 iu khin tc ng c DC bng phng php PWM

i vi iu khin tc ng c DC trong robot, phng php c s dng ph bin nht l iu ch rng xung (Pulse Width

Modulation) hay c gi tt l iu xung, bm xung hoc PWM.

Nguyn l ca phng php ny l bt tt nhanh ngun in cp vo ng c to ra mt tn hiu xung. Khi vic bt tt tn s ln (thng s

dng t 1kHz n 20kHz), ng c s chy vi 1 tc n nh nh moment quay.

Thi gian cp ngun cho ng c l T-on, thi gian tt ngun ng c l T-off. Vic thay i thi gian T-on v T-off lm thay i in p hiu

dng cp cho ng c. i vi ng c DC, tc ng c tng i t l thun vi in p cp cho ng c. V vy, bng cch thay i rng

ca xung, ta thay i c tc ca ng c DC.

i lng biu din mi quan h gia T-on v T-off c gi l duty cycle:

duty_cycle = Ton / ( Ton + Toff )

V d: Ta cp ngun ng c trong 0.8ms, sau tt 0.2ms.

Nh vy: T-on = 0.8ms; T-off = 1ms. Tn s PWM l:

f = 1 / ( Ton + Toff ) = 1 / ( 0.8ms + 0.2ms ) = 1/1ms = 1KHz

duty_cycle = Ton / ( Ton + Toff ) = 0.8 / ( 0.8 + 0.2 ) = 0.8 = 80%

V tc ng c DC t l vi duty cycle nn tc ng c t tng ng 80% tc ti a.

Tnh ton duty cycle iu khin tc ng c DC

3.1.3 iu xung PWM dng vi iu khin

iu xung PWM bng phn mm:

iu xung PWM mt cch n gin l a 1 chn no ca vi iu khin ln mc 1, sau a xung mc 0. Cng vic ny c lp i lp li

lin tc s to ra xung, v tc ca ng c s tng ng vi duty cycle.

V d: iu xung trn chn A0 :

Code

RA0=1;

Delay_ms(Ton);

RA0=0;

Delay_ms(Toff);

Tuy nhin, nu thc hin bng cch ny th vi iu khin s lun dnh thi gian cho vic iu xung PWM. Do , cc cng vic khc nh nhn

tn hiu t cm bin, iu khin cc c cu s b nh hng.

iu xung PWM bng phn cng

gii quyt vn vic iu xung PWM bng phn mm chim phn ln thi gian hot ng ca vi iu khin, PIC16F877A c h tr 2 knh

iu xung bng phn cng 2 chn C1 (CCP2) v C2(CCP1) s dng TIMER2. Ngha l, khi ta khai bo iu xung PWM mt tn s v

duty cycle no th vi iu khin s thc hin cng vic xut xung mt cch lin tc v t ng cho n khi ta thay i cc gi tr khai bo.

Khi , ta c th lm cc cng vic khc mt cch d dng m khng phi mt thi gian cho vic duy tr xung PWM.

Cc hm h tr vic iu xung bng phn cng ca CCS:

Ghi ch: Ch cp n cc i s ca cc hm c phc v cho vic iu xung PWM.

o setup_timer_2 (mode, period, postscale)

mode: T2_DIV_BY_1, T2_DIV_BY_4, T2_DIV_BY_16

period: 0-255

postscale: 1

Tn s iu xung PWM:

f = fosc / [ 4*mode*(period+1) ]

o setup_ccp1(mode) v setup_ccp2(mode)

mode:

CCP_PWM: chn ch PWM.

CCP_OFF: tt ch PWM.

o set_pwm1_duty(value) v set_pwm2_duty(value)

Nu value l gi tr kiu int 8bit:

duty_cycle = value / ( period+1 )

Nu value l gi tr long int 16bit:

duty_cycle = value&1023 / [4*( period+1 )]

Nu khng cn iu xung qu mn th nn iu xung gi tr value 8bit cho n gin.

V d: Ta mun iu xung PWM vi tn s 10kHz vi tn s thch anh (fosc) s dng l 20MHz (value 8bit).

f=fosc/[4*mode*(period+1)] 10000 =20000000/[ 4*mode*(period+1) ] mode(period+1) = 500

Vi mode = [1,4,16] v period = 0-255 ta c th chn:

o mode = 4; period = 124

o mode = 16; period = 32

cho vic iu xung c mn (chn c nhiu gi tr duty cycle) ta chn mode = 4 v period = 124.

Nh vy, duty_cycle t 0% n 100% ta cho value t 0 n 125.

o value = 30 => duty_cycle = 30 / ( 124+1 ) = 0.32 = 32%

o value = 63 => duty_cycle = 63 / ( 124+1 ) = 0.504 = 50.4%

o value = 113 => duty_cycle = 113 / ( 124+1 ) = 0.904 = 90.4%

Code:

setup_timer_2(T2_DIV_BY_4,124,1);

setup_ccp1(CCP_PWM);

set_pwm1_duty(30);

S dng CCP1 v CCP2 cho ng c tri v ng c phi, ta c th iu khin c tc ca 2 ng c ph hp trng thi lch khi vch

trng ca robot.

Cc chng trnh con tham kho:

vic lp trnh c d dng, ta nn to cc chng trnh con x l tc . Sau y l chng trnh tham kho ca hm speed.

o Speed (tc ng c tri, tc ng c phi)

Tc : -100 n 100 (chy ngc 100% n chy thun 100%)

V d: speed(80,60) => ng c tri chy 80%, phi 60%

// Cc hm h tr

void left_motor_forward(int value)

{

MOTOR_LEFT_DIR=0;

setup_timer_2(T2_DIV_BY_4,124,1); // Dieu xung 10kHz


set_pwm2_duty(value);

}

void right_motor_forward(int value)

{

MOTOR_RIGHT_DIR=0;




}

void left_motor_reverse(int value)

{

MOTOR_LEFT_DIR=1;




}

void right_motor_reverse(int value)

{

MOTOR_RIGHT_DIR=1;




}

void left_motor_stop()

{

setup_ccp1(CCP_OFF);

}

void right_motor_stop()

{

setup_ccp1(CCP_OFF);

}

// Chng trnh x l tc 2 ng c

// 0:Stop,100:FORWARD 100%,-100:Reverse 100%

void speed (signed int left_motor_speed, signed int right_motor_speed)

{

int left_pwm_value=0,right_pwm_value=0;

/* Left motor */

if( left_motor_speed >= 0 )

{

left_pwm_value = 1.25*left_motor_speed; // (125*left_motor_speed/100)

left_motor_forward(left_pwm_value);

}

else

{

left_motor_speed = -left_motor_speed;

left_pwm_value = 1.25*left_motor_speed; // (125*left_motor_speed/100)

left_motor_reverse(left_pwm_value);

}

/* Right motor */

if( right_motor_speed >= 0 )

{

right_pwm_value = 1.25*right_motor_speed; // (125*left_motor_speed/100)

right_motor_forward(right_pwm_value);

}

else

{

right_motor_speed = -right_motor_speed;

right_pwm_value = 1.25*right_motor_speed; // (125*left_motor_speed/100)

right_motor_reverse(right_pwm_value);

}

}

3.2 Nhn bit vch ngang

Trong qu trnh di chuyn ca robot, s c cc vch ngang mu trng. Nh cc vch ngang ny, robot bit c mnh ang i n u v s thc

hin cng vic g tip theo (quay tri, quay phi, nng h trc, gp nh qu,)

Mt cch n gin, khi robot n vch trng, tt c 8 cm bin s ln mc 1 ng vi gi tr c c ca cm bin l 0b11111111 hay 0xFF. Ta

dng mt bin m bit th t ca vch ngang ang gp v thc hin cng vic mong mun.

Code:

int n // t n l s vch ngang nhn

if (SENSOR==0xFF)

{

n++; // tng gi tr n ln 1 khi gp vch ngang

switch (n)

{

case 1: (cng vic 1) break;

case 2: (cng vic 2) break;

.

case n: (cng vic n) break;

}

}

else (chng trnh d ng)

Tuy nhin, v nhiu l do khc nhau (nhiu do nh sng bn ngoi, cc cm bin c nhy khng u nhau hoc robot tip cn vi vch ngang

khng theo phng vung gc), mt vi cm bin khi tip xc vi mu trng nhng khng nhn bit (vn gi trng thi mc 0 mu sm). iu

ny gy kh khn cho vic nhn bit vch ngang. V vy, khi 4/8 cm bin mc 1, ta nhn l mt vch ngang khc phc cc nh

hng ny.

Code:

//KIEM TRA VACH NGANG: 1: co vach, 0:khong co vach

int check_cross_line()

{

int temp_sensor=0,led_in_line=0,i=0;

temp_sensor=SENSOR;

for (i=0;i>1;

}

if (led_in_line==4)

return 1;

else

return 0;

}

Do chng trnh nhn vch ngang c gi lin tc kim tra c vch ngang xut hin hay khng nn s dn n tnh trng khi robot n

vch ngang, bin m s vch tng thm 1. Sau , khi robot cha kp chy qua vch ngang m hm kim tra c gi dn n vic bin m

tng lin tc.

Vic ny khin cho robot thc hin sai cng vic.

Hng gii quyt tnh hung ny nh sau:

o Khi robot gp vch ngang: chy thng

o Khi ht vch ngang: bin m s vch tng thm 1

o Thc hin cng vic tng ng

Code:

while (check_cross_line() == 1) // gp vch ngang

{

speed(100,100); // chy thng

}

number_cross_line++; // tng bin m s vch ngang thm 1

3.3 X l khi robot lch hon ton khi vch

Trng hp robot lch ra khi vch (quay qu mnh hoc b va chm), gi tr cm bin c c l 0x00, nh vy robot s b mt phng hng.

gii quyt trng hp ny, ta t mt bin trng thi l bin ton cc.

Gi bin ny l line_status:

o Line_status=0: gia vch;

o Line_status=1: lch tri;

o Line_status=2: lch phi;

Khi c gi tr cm bin d ng , ta gn lun gi tr cho bin ny. Nh vy khi robot lch hn ra khi vch, ta vn bit c trng thi trc

bit quay tri hoc quay phi hng robot di chuyn v

pha line.

Code

switch (SENSOR)

{

case 0b00000000: // lch ra hn khi vch

{

if (line_status==1) // trng thi c l lch tri

turn_right(); break; // quay phi di chuyn v pha vch

if (line_status==2) // trng thi c l lch phi

turn_left(); break; // quay tri di chuyn v pha vch

}

// Trng thi lch thng thng

case 0b00011000: forward(); line_status=0; break;

case 0b00001100: turn_left(); line_status=1; break;




case 0b00110000: turn_right(); line_status=2 ;break;




}

3.4 ng dng encoder

3.4.1 Kin thc c bn v encoder

Trong Robot, ta thng s dng incremental encoder (encoder tng i) hay cn gi l rotary encoder. Mc ch ca vic s dng encoder

trong robot l m s vng quay tnh s vng quay ca ng c (bnh xe), t suy ra qung ng di chuyn v tc ca robot.

Encoder thng c s dng trong Robot

3.4.2 S dng PIC nhn v m xung t encoder

nhn xung t encoder, ta c th s dng ngt ngoi, ngt timer hoc n gin l tham d mc logic ca cc chn vi iu khin mt cch lin

tc. Phn sau y gii thiu cch nhn v m xung ca PIC16F877A dng ngt ngoi B0 (ni vi knh A ca encoder) v chn B1 (ni vi knh

B ca encoder). Ta c th lm tng t i vi cc cch nhn xung khc.

Khi to ngt ngoi theo cnh ln ti chn B0:

Code:

ext_int_edge(0,L_TO_H); // Ngt cnh ln ti RB0

enable_interrupts(INT_EXT); // Cho php ngt ngoi

enable_interrupts(GLOBAL); // Cho php ngt ton cc

Chng trnh con phc v ngt:

Code:

#int_EXT

void EXT_isr(void) //Chng trnh c gi khi c tc ng cnh ln ti chn B0

{

if (RB1==1) pulse++; // Nu knh B mc cao th tng gi tr xung thm 1

else pulse--; // Nu knh B mc cao th gim gi tr xung xung 1

}

T gi tr xung tnh c ti cc thi im ta c th tnh ra cc thng s mong mun.

(Ngun: Cao Hong Long, EM-BOT Robot Team)

Lp Trnh RoBot T ng n Gin Vi VK PIC16F877A

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[123doc.vn] Lap Trinh Robot Tu Dong Don Gian Voi Vdk Pic16f877a