ItR Mini Project 2: Escaping Robot
Final Result
Building Procedure
The building of this robot is based on the last one. If you are interested in the main body-building procedure, you can see this post for greater details.
The majority of change that we’ve made was the addition of the Light Dependent Resistors. At the very beginning, I discussed the amount and the position of the Light Dependent Resistors with my partner. We’ve discussed 3 plans:
1. Only 2 LDRs at the front of the robot.
2. 4 LDRs. 2 at the front, 2 at the back.
3. 4 LDRs. 1 at each side of the robot.
After a short discussion, we’ve chosen the 3rd plan. The 1st & 2nd plan has too many restrictions. The front LDRs cannot work properly if the robot has crushed onto the wall. In addition, the LDRs cannot detect the light from their side if all the sensors are toward the front and the back.
Then we started to build the circuits. Firstly, we need to put the sensors properly. The positions of each LDR are far away from each other. In this case, we cannot just plug them on the breadboard. So we soldered the LDRs with the jump cables and wrap them with tape in order to ensure their structural strength.
Then we connect the circuits following the instructions by 4.
To test if all the sensors are working properly, I use the following code to test the output index of each LDRs.
void setup() { // initialize serial communication at 9600 bits per second: Serial.begin(9600);}void loop() { int sensorValue = analogRead(A0); Serial.print(sensorValue); // print out the value you read: Serial.println(); delay(1); //adding up to 10ms in the loop is harmless to our moving robot}Then I found that the initial values of the LDRs are quite different. The smallest is 10-20 while the largest is around 900. If we map these values directly, the measuring accuracy(range) will be influenced since the measuring range of the Arduino is 0-1023. In this case, I modify the circuit. If the returned value is too small, we can know that the voltage on the LDR is too low. This means the resistor in the circuit is too large. So I change a smaller resistor into the circuit. If the value is too big, means that the resistor is too small. We can change a bigger resistor or paralleling another resistor.
After the modification, all the initial values are around 500-600. Then I map the initial value to the value that I need.
int sensorValueL = analogRead(A0); //left default 600 int sensorValueR = analogRead(A1); //right default 670 int sensorValueF = analogRead(A3); //front d 500 int sensorValueB = analogRead(A4); //back d 640 int realL = map(sensorValueL, 400, 800, 255, 0); int realR = map(sensorValueR, 420, 820, 255, 0); int realF = map(sensorValueF, 0, 500, 0, 500); int realB = map(sensorValueB, 0, 640, 0, 500);As for the motion codes, the logic is quite simple:
If the value of the front LDR is bigger than the back, the robot will go forward. Otherwise, it will go backward. When the robot is going forward, if any LDR value on one side is bigger than another side, then the robot will make a turn in the brighter direction.
if(realB > realF){ carBack(realL, realR); delay(100); }else{ if(realL > realR && realL - realR > 10){ carTurnLeft(realL, realR); delay(100); }else if(realR > realL && realR - realL > 10){ carTurnRight(realL, realR); delay(100); }else{ carAdvance(200, 200); delay(100); } }After a simple test under the classroom light, we found that the accuracy can’t meet our needs.
When the whole environment is dark enough, the accuracy is acceptable.
So when designing the cover of the robot, we made a few changes. We make a roof-like cover that can cover the LDRs under its shadow. We’ve tried our best to reduce the influence of the light in the room. (Although the effect is not quite obvious)
Finally, we are almost done. Here’s the complete code.
// Global variable declarationint speedPin_M1 = 5; //M1 Speed Controlint speedPin_M2 = 6; //M2 Speed Controlint directionPin_M1 = 4; //M1 Direction Controlint directionPin_M2 = 7; //M1 Direction Control// the setup routine runs once when you press reset:void setup() { // initialize the outputs that the motor drivers need int i; for (i = 4; i <= 7; i++) pinMode(i, OUTPUT); // initialize serial communication at 9600 bits per second: Serial.begin(9600);}// the loop routine runs over and over again forever:void loop() { // read all the sensors here int sensorValueL = analogRead(A0); //left default 600 int sensorValueR = analogRead(A1); //right default 670 int sensorValueF = analogRead(A3); //front d 500 int sensorValueB = analogRead(A4); //back d 640 int realL = map(sensorValueL, 400, 800, 255, 0); int realR = map(sensorValueR, 420, 820, 255, 0); int realF = map(sensorValueF, 0, 500, 0, 500); int realB = map(sensorValueB, 0, 640, 0, 500); // if (-100 <= realB - realF <= 100) { // carStop(); // }else if(realB > realF){ carBack(realL, realR); delay(100); }else{ if(realL > realR && realL - realR > 10){ carTurnLeft(realL, realR); delay(100); }else if(realR > realL && realR - realL > 10){ carTurnRight(realL, realR); delay(100); }else{ carAdvance(200, 200); delay(100); } } // decide how to control the actions here // if ( sensorValue0 <= 500 ) { // int speedM1 = map(sensorValue0, 30, 500, 255, 100); // Serial.print(" is the sensor0 value, I calculate speed "); // Serial.print(speedM1); // carAdvance(speedM1, speedM1); // //delay(500); //do not use long delays within loop, unless necessary // } else { // if ( sensorValue0 <= 500 ) { // int speedM1 = map(sensorValue0, 30, 500, 255, 100); // Serial.print(" is the sensor0 value, I calculate speed "); // Serial.print(speedM1); // carAdvance(speedM1, speedM1); // carStop(); // } delay(1); //adding up to 10ms in the loop is harmless to our moving robot}// Auxiliary functions to move the robotvoid carStop(){ // Motor Stop digitalWrite(speedPin_M2,0); digitalWrite(directionPin_M1,LOW); digitalWrite(speedPin_M1,0); digitalWrite(directionPin_M2,LOW);}void carTurnLeft(int leftSpeed,int rightSpeed){ //Move backward analogWrite (speedPin_M2,leftSpeed); //PWM Speed Control digitalWrite(directionPin_M1,HIGH); analogWrite (speedPin_M1,rightSpeed); digitalWrite(directionPin_M2,HIGH);}void carTurnRight(int leftSpeed,int rightSpeed){ //Move forward analogWrite (speedPin_M2,leftSpeed); digitalWrite(directionPin_M1,LOW); analogWrite (speedPin_M1,rightSpeed); digitalWrite(directionPin_M2,LOW);}void carBack(int leftSpeed,int rightSpeed){ //Turn Left analogWrite (speedPin_M2,leftSpeed); digitalWrite(directionPin_M1,LOW); analogWrite (speedPin_M1,rightSpeed); digitalWrite(directionPin_M2,HIGH);}void carAdvance(int leftSpeed,int rightSpeed){ //Turn Right analogWrite (speedPin_M2,leftSpeed); digitalWrite(directionPin_M1,HIGH); analogWrite (speedPin_M1,rightSpeed); digitalWrite(directionPin_M2,LOW);}