Self-balancing robot with two ultrasonic proximity sensors and nRF24 communication + remote.
Things used in this project
Hardware components
Arduino Nano R3 ×2
SparkFun Transceiver Breakout - nRF24L01+ ×1
SparkFun Transceiver Breakout - nRF24L01+ (RP-SMA) ×1
SparkFun Dual H-Bridge motor drivers L298 ×1
ElectroPeak 0.96" OLED 64x128 Display Module ×1
Software apps and online services
Story
It's my final year university project. It's an inverted pendulum, controlled with PID.
And it can be controlled with an Arduino remote.
Custom parts and enclosures
Schematics
Arduino NRF24 remote Download
Code
Self balancing robot (Arduino) Download
#include <PID_v1.h> //PID
#include <LMotorController.h> //Motor driver L298N
#include "I2Cdev.h" //I2C communication
#include "MPU6050_6Axis_MotionApps20.h" //Gyroscope
#include <SPI.h> //SPI communication for NRF24
#include <nRF24L01.h> //NRF24
#include <RF24.h> //NRF24
#include <Ultrasonic.h> //Ultrasonic sensor
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
#include "Wire.h"
#endif
# define MIN_ABS_SPEED 30 //Minimum motor speed (PWM)
//Motor driver pins
int ENA = 5;
int IN1 = 6;
int IN2 = 7;
int IN3 = 8;
int IN4 = 9;
int ENB = 10;
MPU6050 mpu;
// MPU control/status
bool dmpReady = false; // set true if DMP init was successful
uint8_t mpuIntStatus; // holds actual interrupt status byte from MPU
uint8_t devStatus; // return status after each device operation (0 = success, !0 = error)
uint16_t packetSize; // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount; // count of all bytes currently in FIFO
uint8_t fifoBuffer[64]; // FIFO storage buffer
// orientation/motion
Quaternion q; // [w, x, y, z] quaternion container
VectorFloat gravity; // [x, y, z] gravity vector
float ypr[3]; // [yaw, pitch, roll] yaw/pitch/roll container and gravity vector
//PID parameters
double originalSetpoint = 181.80;
double setpoint = originalSetpoint;
double movingAngleOffset = 0.1;
double input, output;
//
double Kp = 60;
double Kd = 2.2;
double Ki = 270;
PID pid( & input, & output, & setpoint, Kp, Ki, Kd, DIRECT);
//To equalize differences between motors
double motorSpeedFactorLeft = 0.65;
double motorSpeedFactorRight = 0.50;
double OriginalmotorSpeedFactorLeft = 0.65;
double OriginalmotorSpeedFactorRight = 0.50;
LMotorController motorController(ENA, IN1, IN2, ENB, IN3, IN4, motorSpeedFactorLeft, motorSpeedFactorRight);
volatile bool mpuInterrupt = false; // indicates whether MPU interrupt pin has gone high
RF24 radio(3, 4); // CE, CSN
const byte address[6] = "06720"; //NRF adress
unsigned long lastRecvTime = 0; //Used to check for delays
//Structure of received data by radio
struct data {
double left;
double right;
double dir;
double inputValue;
boolean modify;
short inputMode;
boolean ultrasonicSensorOn;
};
data receive_data;
Ultrasonic ultraleft(A2, A3); // (Trig PIN,Echo PIN)
Ultrasonic ultraright(A0, A1); // (Trig PIN,Echo PIN)
int distanceCm;
int distanceCm2;;
int loopNumber = 0;
void dmpDataReady() {
mpuInterrupt = true;
}
//Reset values in case of radio signal loss
void reset_the_Data()
{
receive_data.left = 0;
receive_data.right = 0;
receive_data.dir = 0;
receive_data.ultrasonicSensorOn = true;
}
//Read data received by radio
void receive_the_data()
{
while (radio.available()) {
radio.read( & receive_data, sizeof(data));
lastRecvTime = millis();
}
}
//Select PID parameter that changes
void setInputValue(double inpVal, short inpMode) {
switch (inpMode) {
case 0:
originalSetpoint = inpVal;
break;
case 1:
Kp = inpVal;
break;
case 2:
Kd = inpVal;
break;
case 3:
Ki = inpVal;
break;
}
}
void setup() {
Serial.begin(9600); // open the serial port at 9600 bps:
// join I2C bus (I2Cdev library doesn't do this automatically)
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
Wire.begin();
TWBR = 24; // 400kHz I2C clock (200kHz if CPU is 8MHz)
#elif I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_FASTWIRE
Fastwire::setup(400, true);
#endif
mpu.initialize();
devStatus = mpu.dmpInitialize();
// supply your own gyro offsets here, scaled for min sensitivity
mpu.setXGyroOffset(220);
mpu.setYGyroOffset(76);
mpu.setZGyroOffset(-85);
mpu.setZAccelOffset(1788);
// make sure it worked (returns 0 if so)
if (devStatus == 0) {
// turn on the DMP, now that it's ready
mpu.setDMPEnabled(true);
// enable Arduino interrupt detection
attachInterrupt(0, dmpDataReady, RISING);
mpuIntStatus = mpu.getIntStatus();
// set our DMP Ready flag so the main loop() function knows it's okay to use it
dmpReady = true;
// get expected DMP packet size for later comparison
packetSize = mpu.dmpGetFIFOPacketSize();
//setup PID
pid.SetMode(AUTOMATIC);
pid.SetSampleTime(10);
pid.SetOutputLimits(-255, 255);
} else {
// ERROR!
// 1 = initial memory load failed
// 2 = DMP configuration updates failed
// (if it's going to break, usually the code will be 1)
//Serial.print(F("DMP Initialization failed (code "));
//Serial.print(devStatus);
//Serial.println(F(")"));
}
radio.begin();
radio.setAutoAck(false);
radio.openReadingPipe(0, address);
radio.setPALevel(RF24_PA_MIN);
radio.setDataRate(RF24_250KBPS);
radio.startListening();
}
void loop() {
// if programming failed, don't try to do anything
if (!dmpReady) return;
// wait for MPU interrupt or extra packet(s) available
while (!mpuInterrupt && fifoCount < packetSize) {
//no mpu data - performing PID calculations and output to motors
pid.Compute();
motorController.move(output, MIN_ABS_SPEED);
}
// reset interrupt flag and get INT_STATUS byte
mpuInterrupt = false;
mpuIntStatus = mpu.getIntStatus();
// get current FIFO count
fifoCount = mpu.getFIFOCount();
// check for overflow (this should never happen unless our code is too inefficient)
if ((mpuIntStatus & 0x10) || fifoCount == 1024) {
// reset so we can continue cleanly
mpu.resetFIFO();
//Serial.println(F("FIFO overflow!"));
// otherwise, check for DMP data ready interrupt (this should happen frequently)
} else if (mpuIntStatus & 0x02) {
// wait for correct available data length, should be a VERY short wait
while (fifoCount < packetSize) fifoCount = mpu.getFIFOCount();
// read a packet from FIFO
mpu.getFIFOBytes(fifoBuffer, packetSize);
// track FIFO count here in case there is > 1 packet available
// (this lets us immediately read more without waiting for an interrupt)
fifoCount -= packetSize;
mpu.dmpGetQuaternion( &q, fifoBuffer);
mpu.dmpGetGravity( &gravity, &q);
mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);
input = ypr[1] * 180 / M_PI + 180;
}
receive_the_data();
unsigned long now = millis();
if (now - lastRecvTime > 1000) { //If the delay is greater, reset the data
reset_the_Data();
}
//Direction control with data from remote control
setpoint = originalSetpoint + receive_data.dir;
motorSpeedFactorRight = OriginalmotorSpeedFactorRight + receive_data.right;
motorSpeedFactorLeft = OriginalmotorSpeedFactorLeft + receive_data.left;
if (receive_data.modify) {
setInputValue(receive_data.inputValue, receive_data.inputMode);
PID pid2( & input, & output, & setpoint, Kp, Ki, Kd, DIRECT);
pid2.SetMode(AUTOMATIC);
pid2.SetSampleTime(10);
pid2.SetOutputLimits(-255, 255);
pid = pid2;
}
if (input < 150 || input > 210) {
digitalWrite(ENA, LOW);
digitalWrite(ENB, LOW);
}
//Robot handling with ultrasonic sensors (Setpoint)
if (loopNumber == 2) {
if (receive_data.ultrasonicSensorOn && ultraleft.Ranging(CM) < 30 && ultraleft.Ranging(CM) != 0) {
setpoint = originalSetpoint - 4;
} else {
if (receive_data.ultrasonicSensorOn && ultraright.Ranging(CM) < 30 && ultraright.Ranging(CM) != 0) {
setpoint = originalSetpoint + 4;
}
}
loopNumber = 0;
}
loopNumber++;
}
Arduino NRF24 remote (Arduino) Download
//Remote Transmitter
#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
//LED Display
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
# define L_AXIS A0 // Left Y Axis Port DIR
# define R_AXIS A3 // Right Y Axis Port
# define VALUE A7 // Left Y Axis Port DIR
# define MODIFY 9 // Right Y Axis Port
# define MODE1 2 // Right Y Axis Port
# define MODE2 3 // Right Y Axis Port
# define US_ON 6 // Ultrasonic sensor Port
//LED Display
//Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, & Wire, -1);
float value;
float voltage;
double Os = 182.15;
double Kp = 60.0;
double Kd = 2.2;
double Ki = 270;
boolean ultrasonicSensorOn = true;
int prevButtonState = LOW;
int buttonState = LOW;
struct data {
double left;
double right;
double dir;
double value;
boolean modify;
short mode;
boolean ultrasonicSensorOn;
};
data send_data;
RF24 radio(7, 8); // CE, CSN
const byte address[6] = "06720"; //NRF Address
void setup() {
Serial.begin(9600);
pinMode(MODE1, INPUT_PULLUP);
pinMode(MODE2, INPUT_PULLUP);
pinMode(VALUE, INPUT);
pinMode(MODIFY, INPUT);
pinMode(US_ON, INPUT);
Wire.begin();
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
radio.begin();
radio.setAutoAck(false);
radio.openWritingPipe(address);
radio.setPALevel(RF24_PA_HIGH);
radio.setDataRate(RF24_250KBPS);
radio.stopListening();
}
float mapFloat(float x, float in_min, float in_max, float out_min, float out_max) {
return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}
int getMode(int mode1, int mode2) {
if (mode1 == HIGH && mode2 == HIGH)
return 0;
if (mode1 == HIGH && mode2 == LOW)
return 1;
if (mode1 == LOW && mode2 == HIGH)
return 2;
if (mode1 == LOW && mode2 == LOW)
return 3;
}
char * getModeName(int mode) {
switch (mode) {
case 0:
return "Os";
case 1:
return "Kp";
case 2:
return "Kd";
case 3:
return "Ki";
}
}
float getValue(int mode, int value) {
switch (mode) {
case 0:
return mapFloat(value, 1023, 0, 170.0, 190.0);
case 1:
return mapFloat(value, 1023, 0, 0.0, 100.0);
case 2:
return mapFloat(value, 1023, 0, 0.0, 5.0);
case 3:
return mapFloat(value, 1023, 0, 0.0, 500.0);
}
}
void setOriginalValue(int mode, double value) {
switch (mode) {
case 0:
Os = value;
break;
case 1:
Kp = value;
break;
case 2:
Kd = value;
break;
case 3:
Ki = value;
break;
}
}
void loop() {
int readLaxis = analogRead(L_AXIS);
int readRaxis = analogRead(R_AXIS);
int readValue = analogRead(VALUE);
int readModify = digitalRead(MODIFY);
int mode1 = digitalRead(MODE1);
int mode2 = digitalRead(MODE2);
buttonState = digitalRead(US_ON);
send_data.dir = readLaxis > 497 && readLaxis < 517 ? 0 : mapFloat(readLaxis, 0, 1023, -2.00, 2.00); //A ?0: (ternary valami roviditett if
send_data.right = readRaxis > 492 && readRaxis < 512 ? 0 : mapFloat(readRaxis, 0, 1023, -0.50, 0.50);
send_data.left = readRaxis > 492 && readRaxis < 512 ? 0 : mapFloat(readRaxis, 0, 1023, 0.50, -0.50);
send_data.value = getValue(getMode(mode1, mode2), readValue);
send_data.modify = readModify == HIGH;
send_data.mode = getMode(mode1, mode2);
// Serial.print(send_data.right);
// Serial.print(" ");
// Serial.println(send_data.left);
// Serial.println(digitalRead(MODIFY));
// Serial.println(digitalRead(US_ON));
if (send_data.modify) {
setOriginalValue(send_data.mode, send_data.value);
}
if (prevButtonState != buttonState) {
if (buttonState == HIGH) {
ultrasonicSensorOn = !ultrasonicSensorOn;
send_data.ultrasonicSensorOn = ultrasonicSensorOn;
}
}
prevButtonState = buttonState;
radio.write( & send_data, sizeof(data));
value = analogRead(A6);
voltage = ((5 * value) / 1023) * 4.103354632587859;
display.clearDisplay();
display.setTextColor(WHITE);
display.setTextSize(1);
display.setCursor(0, 0);
display.print("Dir: ");
display.println(send_data.dir);
display.print("Os: ");
display.print(Os);
display.print(" Kp: ");
display.print(Kp);
display.print(" Kd: ");
display.print(Kd);
display.print(" Ki: ");
display.println(Ki);
display.print("\n");
display.print(getModeName(send_data.mode));
display.print(": ");
display.println(send_data.value);
display.println(ultrasonicSensorOn);
display.print("\n");
display.print("Voltage: ");
display.print(voltage);
display.print("V");
display.display();
}
