Ultrasound: we see the cargo

The sensor sends out a short ultrasonic click and listens for the echo. The further away the object, the longer the sound travels back and forth.

1. Write the calculation in the journal.
2. Explain why time needs to be multiplied by two.

The sensor sends out a short ultrasonic click and listens for the echo. The distance is calculated by flight time.

1. Sound travels 1 cm in approximately 29 µs. Derive a formula for the distance in centimeters from the echo duration in microseconds.
2. The speed of sound depends on temperature. At 0 °C, sound travels 1 cm in approximately 30 µs. The load is 50 cm away. What distance will the sensor report in a cold corridor in winter if the program assumes 29 µs per centimeter? Does this error matter when stopping 5 cm away?

1. Look at the TRIG and ECHO contact numbers on the robot's card. There is no card - trace the wires from the TRIG and ECHO pins of the sensor to the board and read the numbers at the sockets. Write it down in a journal.
2. Create a sketch L51_Distance according to the template and enter the contact numbers instead -1.
3. Write the function readDistanceCm() myself. Printing in the Serial Monitor is now ready. Until the function is written, the monitor prints "no echo".

// Шаблон среднего уровня. Напиши код в разделе «Твоя часть» по целям в комментариях. // Контакты ультразвукового датчика: впиши номера из таблицы проводки своего робота.const int TRIG_PIN = -1;const int ECHO_PIN = -1; // ===== Твоя часть: напиши сам ===== int readDistanceCm() {  // Щёлкнуть датчиком и вернуть расстояние до груза в сантиметрах.  // Если эхо не вернулось за 25 000 мкс, вернуть -1.  return -1;} // ===== Готовое: настройка датчика и печать — не меняй ===== void setupSonar() {  // Без контактов датчика программа дальше не пойдёт.  if (TRIG_PIN < 0 || ECHO_PIN < 0) {    while (true) {    }  }  pinMode(TRIG_PIN, OUTPUT);  pinMode(ECHO_PIN, INPUT);} void setup() {  Serial.begin(9600);  setupSonar();} void loop() {  int distance = readDistanceCm();  if (distance < 0) {    Serial.println("нет эха");  } else {    Serial.print(distance);    Serial.println(" см");  }  delay(200);}

4. Upload, open the Serial Monitor. Place the weight at 5, 10, 20 and 30 cm along the ruler. Record the readings.

1. Look at the TRIG and ECHO contact numbers on the robot's card. There is no card - trace the wires from the TRIG and ECHO pins of the sensor to the board and read the numbers at the sockets. Write it down in a journal.

Requirement 1. Function readDistanceCm() returns the distance in centimeters, or −1 if there is no echo. How the sensor works:

• a HIGH pulse with a length of 10 µs is sent to TRIG (preceded by a short LOW);
• the sensor keeps ECHO at HIGH for as many microseconds as the sound travels back and forth;
• sound travels 1 cm in approximately 29 μs;
• no need to wait for echo longer than 25,000 µs: command pulseIn(pin, HIGH, timeoutUs) will return 0.

Without pin numbers, the program should not work with the sensor: let it stop. Write a sketch L51_Distance, which prints the distance or "no echo".

Acceptance. Ruled table and answers in the journal.

2. What is the largest distance the function can measure when waiting 25,000 µs?
3. Does the error increase with distance? How do you explain this?

1. Check the sensor in three positions and write down what the monitor prints:

2. Write down the correct stopping condition.

Find the limits beyond which the sensor cannot be trusted.

1. Place the weight 20 cm and turn it sideways towards the sensor. From what angle does the echo disappear?
2. Move the weight towards the sensor. At what distance do the readings stop matching the ruler?
3. Point the sensor at soft tissue. What does the monitor print?

4. Write down which of the boundaries found are dangerous for delivery and how the program should behave in each case.

1. Create a sketch L51_Stop_At_Can according to the template. Transfer measurements kp, baseSpeed, sensor contacts and replace readDistanceCm by its function.
2. Write the movement in setup() himself: the robot drives along the line and stops in front of the load. Remember the step “No echo - not nearby.”

// Шаблон среднего уровня. Напиши код в разделе «Твоя часть» по целям в комментариях.// Функцию readDistanceCm ниже замени своей из L51_Distance. const int LEFT_SENSOR_PIN = A4;const int RIGHT_SENSOR_PIN = A5;const int LEFT_DIR_PIN = 7;const int LEFT_SPEED_PIN = 6;const int RIGHT_DIR_PIN = 4;const int RIGHT_SPEED_PIN = 5;const int FORWARD = HIGH;const int BACKWARD = (FORWARD == HIGH) ? LOW : HIGH; // Измерения и настройки из журнала (уроки 3.1 и 3.2).const int LEFT_WHITE = 0;const int LEFT_BLACK = 0;const int RIGHT_WHITE = 0;const int RIGHT_BLACK = 0;float kp = 0.5;int baseSpeed = 100;int leftLevel = 100;int rightLevel = 100; // Контакты ультразвукового датчика: впиши номера из таблицы проводки своего робота.const int TRIG_PIN = -1;const int ECHO_PIN = -1;const int STOP_CM = 5; // на каком расстоянии от груза остановиться // ===== Твоя часть: напиши сам ===== void setup() {  setupSonar();  setupRobot();   // Ехать по линии и остановиться, когда груз не дальше STOP_CM.  // «Нет эха» — не «груз рядом»: тогда робот едет дальше.} // ===== Готовое из уроков 3.2 и 5.1 — не меняй ===== int level(int value, int white, int black) {  long result = (long)(value - black) * 100 / (white - black);  return constrain(result, 0, 100);} void readSensors() {  leftLevel = level(analogRead(LEFT_SENSOR_PIN), LEFT_WHITE, LEFT_BLACK);  rightLevel = level(analogRead(RIGHT_SENSOR_PIN), RIGHT_WHITE, RIGHT_BLACK);} void drive(int leftDir, int leftSpeed, int rightDir, int rightSpeed) {  digitalWrite(LEFT_DIR_PIN, leftDir);  digitalWrite(RIGHT_DIR_PIN, rightDir);  analogWrite(LEFT_SPEED_PIN, leftSpeed);  analogWrite(RIGHT_SPEED_PIN, rightSpeed);} void stopMotors() {  analogWrite(LEFT_SPEED_PIN, 0);  analogWrite(RIGHT_SPEED_PIN, 0);} void followLineStep() {  int error = leftLevel - rightLevel;  int correction = kp * error;  drive(FORWARD, constrain(baseSpeed + correction, 0, 255),        FORWARD, constrain(baseSpeed - correction, 0, 255));} void setupRobot() {  pinMode(LEFT_DIR_PIN, OUTPUT);  pinMode(LEFT_SPEED_PIN, OUTPUT);  pinMode(RIGHT_DIR_PIN, OUTPUT);  pinMode(RIGHT_SPEED_PIN, OUTPUT);  stopMotors();  // Без измерений робот не поедет.  if (LEFT_WHITE == LEFT_BLACK || RIGHT_WHITE == RIGHT_BLACK) {    while (true) {    }  }  delay(2000);} // Расстояние в сантиметрах или -1, если эхо не вернулось.int readDistanceCm() {  digitalWrite(TRIG_PIN, LOW);  delayMicroseconds(2);  digitalWrite(TRIG_PIN, HIGH);  delayMicroseconds(10);  digitalWrite(TRIG_PIN, LOW);  unsigned long echoUs = pulseIn(ECHO_PIN, HIGH, 25000);  if (echoUs == 0) {    return -1;  }  return echoUs / 58;} void setupSonar() {  // Без контактов датчика программа дальше не пойдёт.  if (TRIG_PIN < 0 || ECHO_PIN < 0) {    while (true) {    }  }  pinMode(TRIG_PIN, OUTPUT);  pinMode(ECHO_PIN, INPUT);} void loop() {}

3. Place the weight at the end of the line. Launch the robot from the other end.

Requirement 2. Continue with your program L42_Turn_At_Crossing and save as L51_Stop_At_Can. Function followLineToCan(stopCm) guides the robot along the line and stops it when the load is no further stopCm:

• "no echo" is never considered "cargo nearby";
• after stopping, the motors are turned off;
• the line and intersection functions from previous lessons do not change.

Acceptance. Load at the end of the line - the robot stops without touching the load. There is no load - the robot reaches the end of the line without stopping in the middle of the road (be prepared to turn off the power).

Pick up STOP_CM and baseSpeed so that the robot stops where it is convenient to grab. Change one number at a time.

1. Decide how far away from the load the robot should stand. If the gripper is already in place, measure it; if not, choose the distance at which the robot does not touch the load, and clarify it in lesson 5.2. Write it down.
2. Start it, measure with a ruler where the robot stopped. Write it down in a table and decide what to change.

3. When it works, repeat three times.

Get it to stop at the right distance ±1 cm three times out of three at its operating speed - the one at which the robot passes the line.

1. Measure the run-out: at baseSpeed 80, 120 and set your worker STOP_CM = 15 and measure how many centimeters the robot rolled after the stop command.
2. Choose a method for precise stopping and justify it with a table: correct STOP_CM coast or drive slower in the last centimeters before the load.
3. Triple check.