ece nith
OBSTACLE AVOIDING ROBOT USING ULTRASONIC SENSOR
Dependencies: HCSR04 Motordriver Servo TextLCD mbed
Diff: main.cpp
- Revision:
- 0:a87600bebf7b
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Sat May 18 04:39:55 2013 +0000
@@ -0,0 +1,229 @@
+/* Megha Sharma, Rishabh Sehgal, Ragheshwar Singh Ranawat ,E.C.E.D NIT Hamirpur
+
+ OBSTACLE AVOIDING ROBOT USING ULTRASONIC SENSOR HCSR04
+
+In this project LPC 1768 embed board along with NGX Expresso baseboard are successfuly used to make an obstacle avoiding/
+self navigating robot which makes use of Ultrasonic Sensor HCSR04 for obstacle detection and Ranging. The maximum range of
+Ultrasonic sensor is about 3-4 meters. A program called "ping" sends a serial trigger pulse of 10 nS to the Trigger pin of
+HCSR04 and on receiving the trigger HCSR04 beams out an 8 cycle Sonic burst. Then Echo pulse is received by the Ultrasonic sensor
+upto 25ms. On receiving the Echo pulse distance is calculated. The HCSR04 is mounted Axially on a servo motor. Initially the HCSR04
+is kept in a straight direction. Motors make bot move in forward direction and continuosly calculating the distance of the
+nearest obstacle in the forward direction. After seeing a distance at less than a "Constraint Value" (i.e. 10 cm here),
+the robot goes in a scan mode. It first moves the Servo Motor to the Right, waits for 2 seconds and stores the value of
+Distance in right direction in "rightscanval" variable.Then it comes back to centre position. Now it moves towards the
+Left direction, waits for 2 seconds and stores the value of Distance in "leftscanval" variable. Then it comes back to the
+centre position. Now it does the comparison of the two variables to determine in which direction it should move. It
+successfully turns towards the direction with the farthest distance of obstacle.
+
+Again the Servo motor is in forward direction keeping the sensor straight and the Robot also moves towards Forward direction all
+the while calculating the distance of obstacle in forward direction. The loop continues.....
+
+*/
+#include "mbed.h"
+#include "hcsr04.h"
+#include "motordriver.h"
+#include "TextLCD.h"
+#include "Servo.h"
+int ping ();
+void scan();
+void right (void);
+void stop (void );
+void straight (void);
+void left (void);
+Motor A(p22, p6, p5, 1); // pwm, fwd, rev, can brake
+Motor B(p21, p7, p8, 1);
+HCSR04 usensor(p13,p14);
+TextLCD lcd(p24, p26, p27, p28, p29, p30); // rs, e, d4-d7
+PwmOut servo(p23); // Servo pin 21
+
+
+unsigned int dist;
+DigitalOut myled(LED1);
+DigitalOut myled1(LED2);
+DigitalOut myled2(LED3);
+int count = 0;
+
+int main ()
+ {
+
+ while (1) // continuos loop to perform the scanning function of HCSR04 ..
+ //a trigger pulse of Ultrasonic waves having duration 10 nS is sent through the echo pin
+ {
+
+ servo.period(0.020);
+ int distance = ping(); // ping function
+ straight(); // use the ping() function to see if anything is ahead.
+
+
+ if (distance < 10) // the condition for stopping the Obstacle Avoider...
+ // ...whenever the defined proximity to obstacle is reached.
+ {
+ stop();
+ scan();
+
+
+ /*switch (a) // switch case for initial testing of the Obstacle detection by sensor and
+ // Corresponding L.E.D. of the best direction will glow.
+
+ {
+ case 'r':
+ myled=1;
+ break;
+ case 'l':
+ myled1=1;
+ break;
+ case 'f':
+ myled2=1;
+ break;
+ }*/
+
+ }
+ }
+ }
+
+ // A functon to perform the continuos pinging function of HCSR04 ..
+ //a trigger pulse of Ultrasonic waves having duration 10 nS is sent through the echo pin
+
+ int ping() // ultrasonic sensor is started and data collected is displayed on the LCD
+ // ping function returns an int value of distance scanned
+ {
+ usensor.start();
+ wait_ms(200);
+ dist=usensor.get_dist_cm();
+ lcd.cls();
+ lcd.locate(0,0);
+ if (dist <50)
+ lcd.printf("cm:%ld",dist );
+ else
+ lcd.printf("no object");
+ return (dist);
+
+ }
+
+
+ void scan ()
+ {
+
+ int leftscanval, rightscanval; // variables for storing distance scan values...
+ //... of nearest obstacle in the left and right direction
+
+
+ // Scanning RIGHT side; turning the servo attached to HCSR04 right to check for obstacle distance
+
+ // 0.0016 corresponds to the neutral position of servo motor
+ // 0.0027 corresponds to the rightmost position of the servo motor
+ // 0.0009 corresponds to the leftmost position of the servomotor
+
+ for(float offset=0.0016; offset<=0.0027; offset+=0.0001) // turning RIGHT
+
+ {
+ servo.pulsewidth(offset); // servo position determined by a pulsewidth between 1-2ms
+ wait(0.10);
+ }
+ wait (2); // stopping at RIGHTMOST position for 2 seconds
+ rightscanval = ping(); // putting the distance of right direction's obstacle in ''rightscanval variable''
+
+
+
+ for(float offset=0.0027; offset>=0.0016; offset+=-0.0001) // turning back to the CENTER position
+
+ {
+ servo.pulsewidth(offset); // servo position determined by a pulsewidth between 1-2ms
+ wait(0.10);
+ }
+ wait(2); // stopping at CENTERMOST position for 2 seconds
+
+
+ // Scanning LEFT side; turning the servo attached to HCSR04 right to check for obstacle distance
+
+
+ for(float offset=0.0016; offset>=0.0009; offset-=0.0001) // Turning towards LEFT
+
+ {
+ servo.pulsewidth(offset); // servo position determined by a pulsewidth between 1-2ms
+ wait(0.10);
+ }
+ wait(2); // stopping at LEFTMOST position for 2 seconds
+ leftscanval = ping(); // putting the distance of right direction's obstacle in ''leftscanval variable''
+
+
+ for(float offset=0.0009; offset<=0.0016; offset+=0.0001)
+
+ {
+ servo.pulsewidth(offset); // servo position determined by a pulsewidth between 1-2ms
+ wait(0.10);
+ }
+ /*center scan servo (for changing the default position of Servo to the Centre Position ) This method didnt work
+ though. There is a library of Servo
+ */
+ //servo.pulsewidth(0.00017);
+
+
+ /* Comparisons to choose the most appropiate direction for the turning of Robot. Based on the distances stored in variables "leftscanvalue" and "rightscanvalue" */
+
+ if (leftscanval>rightscanval )
+
+ {
+ left();
+ }
+
+ else if (rightscanval>leftscanval )
+
+ {
+ right();
+ }
+
+ else
+ {
+ left();
+ }
+
+ //return choice;
+ }
+
+ void stop () // function for stopping the DC motors
+
+ {
+ A.speed(0);
+ B.speed(0);
+ }
+
+
+ void left() // function for moving the RIGHT motor in FORWARD direction and LEFT motor in REVERSE direction so...
+ // ..that the robot turns to the LEFT
+
+ {
+ for (float s= -1.0; s < 0.0 ; s += 0.01)
+ {
+ A.speed(-1);
+ B.speed(-1);
+ wait(0.02);
+ }
+ }
+
+
+ void right () // function for moving the RIGHT motor in REVERSE direction and LEFT motor in FORWARD direction so...
+ // ..that the robot turns to the LEFT
+
+ {
+ for (float s= -1.0; s < 0.0 ; s += 0.01)
+ {
+ A.speed(1);
+ B.speed(1);
+ wait(0.02);
+ }
+ }
+
+
+ void straight () // function for moving the RIGHT motor in FORWARD direction and LEFT motor in REVERSE direction so...
+ // ..that the robot turns to the LEFT
+
+ {
+ //for (float s= -1.0; s < -0.7 ; s += 0.01)
+ {
+ A.speed(-1);
+ B.speed(1);
+ wait(0.02);
+ }
+
+ }
\ No newline at end of file