Shivank Rao
Published © LGPL

Command Controlled Rover

A simple way t control a terrain-based rover, from your laptop using Robotics Operating System (ROS2).

IntermediateShowcase (no instructions)5 hours294
Command Controlled Rover

Things used in this project

Hardware components

Arduino UNO
Arduino UNO
×1
Raspberry Pi 4 Model B
Raspberry Pi 4 Model B
×1
Jumper wires (generic)
Jumper wires (generic)
×1
TT Motors GMP36-TEC3650
×1
Battery 12/24V
×1

Software apps and online services

Robot Operating System
ROS Robot Operating System
Arduino IDE
Arduino IDE
Thonny

Story

Read more

Custom parts and enclosures

The CAD Model

This is the CAD model of the rover body.

Schematics

Arduino to motors interfacing

Arduino <-> Raspberry Pi

Just connect your Pi board and UNO with the serial cable

Code

Arduino Code

C/C++
This is the code to control the motors used.
#define DIR_PIN1 3       // Direction control (CW/CCW) for Motor 1
#define PWM_PIN1 9       // PWM signal for speed control for Motor 1
#define BRAKE_PIN1 8     // Brake control for Motor 1
#define DIR_PIN2 4       // Direction control (CW/CCW) for Motor 2
#define PWM_PIN2 10      // PWM signal for speed control for Motor 2
#define BRAKE_PIN2 7     // Brake control for Motor 2
#define DIR_PIN3 5       // Direction control (CW/CCW) for Motor 3
#define PWM_PIN3 11      // PWM signal for speed control for Motor 3
#define BRAKE_PIN3 13     // Brake control for Motor 3
#define DIR_PIN4 2       // Direction control (CW/CCW) for Motor 4
#define PWM_PIN4 6       // PWM signal for speed control for Motor 4
#define BRAKE_PIN4 12    // Brake control for Motor 4
#define FEEDBACK_PIN1 A0 // Feedback for Motor 1
#define FEEDBACK_PIN2 A1 // Feedback for Motor 2
#define FEEDBACK_PIN3 A2 // Feedback for Motor 3
#define FEEDBACK_PIN4 A3 // Feedback for Motor 4

int motorSpeed = 200;

void setup(){
  Serial.begin(9600);
  pinMode(DIR_PIN1, OUTPUT);
  pinMode(PWM_PIN1, OUTPUT);
  pinMode(BRAKE_PIN1, OUTPUT);
  // pinMode(FEEDBACK_PIN1, INPUT);
  pinMode(DIR_PIN2, OUTPUT);
  pinMode(PWM_PIN2, OUTPUT);
  pinMode(BRAKE_PIN2, OUTPUT);
  // pinMode(FEEDBACK_PIN2, INPUT);
  pinMode(DIR_PIN3, OUTPUT);
  pinMode(PWM_PIN3, OUTPUT);
  pinMode(BRAKE_PIN3, OUTPUT);
  // pinMode(FEEDBACK_PIN3, INPUT);
  pinMode(DIR_PIN4, OUTPUT);
  pinMode(PWM_PIN4, OUTPUT);
  pinMode(BRAKE_PIN4, OUTPUT);
  // pinMode(FEEDBACK_PIN4, INPUT);
  initial_state();
}

void loop(){
  if (Serial.available()>0){
    char command = Serial.read();

    if (command == 'F'){
      digitalWrite(DIR_PIN1, LOW);
      digitalWrite(DIR_PIN2, LOW);
      digitalWrite(DIR_PIN3, LOW);
      digitalWrite(DIR_PIN4, LOW);
      digitalWrite(BRAKE_PIN1, HIGH);
      digitalWrite(BRAKE_PIN2, HIGH);
      digitalWrite(BRAKE_PIN3, HIGH);
      digitalWrite(BRAKE_PIN4, HIGH);
      analogWrite(PWM_PIN1, motorSpeed);
      analogWrite(PWM_PIN2, motorSpeed);
      analogWrite(PWM_PIN3, motorSpeed);
      analogWrite(PWM_PIN4, motorSpeed);
    }
    else if (command == 'B'){
      digitalWrite(DIR_PIN1, HIGH);
      digitalWrite(DIR_PIN2, HIGH);
      digitalWrite(DIR_PIN3, HIGH);
      digitalWrite(DIR_PIN4, HIGH);
      digitalWrite(BRAKE_PIN1, HIGH);
      digitalWrite(BRAKE_PIN2, HIGH);
      digitalWrite(BRAKE_PIN3, HIGH);
      digitalWrite(BRAKE_PIN4, HIGH);
      analogWrite(PWM_PIN1, motorSpeed);
      analogWrite(PWM_PIN2, motorSpeed);
      analogWrite(PWM_PIN3, motorSpeed);
      analogWrite(PWM_PIN4, motorSpeed);
    }
    else if (command == 'S'){
      initial_state();
    }
    else if (command == 'L') {
      digitalWrite(DIR_PIN1, LOW);
      digitalWrite(DIR_PIN2, HIGH);
      digitalWrite(DIR_PIN3, LOW);
      digitalWrite(DIR_PIN4, HIGH);
      digitalWrite(BRAKE_PIN1, HIGH);
      digitalWrite(BRAKE_PIN2, HIGH);
      digitalWrite(BRAKE_PIN3, HIGH);
      digitalWrite(BRAKE_PIN4, HIGH);
      analogWrite(PWM_PIN1, motorSpeed);
      analogWrite(PWM_PIN2, motorSpeed);
      analogWrite(PWM_PIN3, motorSpeed);
      analogWrite(PWM_PIN4, motorSpeed);
    }
  else if (command == 'R'){
      digitalWrite(DIR_PIN1, HIGH);
      digitalWrite(DIR_PIN2, LOW);
      digitalWrite(DIR_PIN3, HIGH);
      digitalWrite(DIR_PIN4, LOW);
      digitalWrite(BRAKE_PIN1, HIGH);
      digitalWrite(BRAKE_PIN2, HIGH);
      digitalWrite(BRAKE_PIN3, HIGH);
      digitalWrite(BRAKE_PIN4, HIGH);
      analogWrite(PWM_PIN1, motorSpeed);
      analogWrite(PWM_PIN2, motorSpeed);
      analogWrite(PWM_PIN3, motorSpeed);
      analogWrite(PWM_PIN4, motorSpeed);
    }
  }
}
void initial_state(){
  analogWrite(PWM_PIN1, 255);
  analogWrite(PWM_PIN2, 255);
  analogWrite(PWM_PIN3, 255);
  analogWrite(PWM_PIN4, 255);
}

Python code

Python
This is the code to send commands from the main server (laptop) to the slave or the subscriber.
import rclpy
from rclpy.node import Node
from geometry_msgs.msg import Twist
import serial

class TeleopToArduino(Node):
    def __init__(self):  # <-- Corrected method name (was: init)
        super().__init__('teleop_to_arduino')

        # Serial communication with Arduino
        try:
            self.serial_port = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
            self.get_logger().info("Serial port opened successfully.")
        except serial.SerialException as e:
            self.get_logger().error(f"Failed to open serial port: {e}")
            self.serial_port = None

        # Subscribe to the /cmd_vel topic
        self.subscription = self.create_subscription(
            Twist,
            '/cmd_vel',
            self.cmd_vel_callback,
            10
        )

    def cmd_vel_callback(self, msg):
        linear = msg.linear.x
        angular = msg.angular.z

        # Determine direction and send command
        if linear > 0:
            self.send_command('F')  # Forward
        elif linear < 0:
            self.send_command('B')  # Backward
        elif angular > 0:
            self.send_command('L')  # Turn Left
        elif angular < 0:
            self.send_command('R')  # Turn Right
        else:
            self.send_command('S')  # Stop

    def send_command(self, command):
        if self.serial_port and self.serial_port.is_open:
            self.serial_port.write(command.encode())
            self.get_logger().info(f"Sent command: {command}")
        else:
            self.get_logger().warn("Serial port not open. Command not sent.")

def main(args=None):
    rclpy.init(args=args)
    node = TeleopToArduino()
    try:
        rclpy.spin(node)
    except KeyboardInterrupt:
        node.get_logger().info('Node stopped cleanly')
    except Exception as e:
        node.get_logger().error(f'Exception: {e}')
    finally:
        if node.serial_port and node.serial_port.is_open:
            node.serial_port.close()
        node.destroy_node()
        rclpy.shutdown()

if __name__ == "__main__":
    main()

The XML Code

XML
Use this code for simulation
<robot name="rover">
  <!-- Chassis -->
  <link name="base_link">
    <visual>
      <geometry>
        <box size="0.42 0.301 0.2"/>
      </geometry>
      <origin xyz="0 0 0.1"/>
      <material name="yellow"/>
    </visual>
    <collision>
      <geometry>
        <box size="0.42 0.301 0.2"/>
      </geometry>
      <origin xyz="0 0 0.1"/>
    </collision>
  </link>

  <!-- Wheels -->
  <!-- Left Front Wheel -->
  <link name="left_front_wheel">
    <visual>
      <geometry>
        <cylinder length="0.05" radius="0.076"/>
      </geometry>
      <origin xyz="0.15 0.178 0.076" rpy="0 1.5708 0"/>
      <material name="red"/>
    </visual>
  </link>

  <!-- Right Front Wheel -->
  <link name="right_front_wheel">
    <visual>
      <geometry>
        <cylinder length="0.05" radius="0.076"/>
      </geometry>
      <origin xyz="0.15 -0.178 0.076" rpy="0 1.5708 0"/>
      <material name="red"/>
    </visual>
  </link>

  <!-- Left Rear Wheel -->
  <link name="left_rear_wheel">
    <visual>
      <geometry>
        <cylinder length="0.05" radius="0.076"/>
      </geometry>
      <origin xyz="-0.15 0.178 0.076" rpy="0 1.5708 0"/>
      <material name="red"/>
    </visual>
  </link>

  <!-- Right Rear Wheel -->
  <link name="right_rear_wheel">
    <visual>
      <geometry>
        <cylinder length="0.05" radius="0.076"/>
      </geometry>
      <origin xyz="-0.15 -0.178 0.076" rpy="0 1.5708 0"/>
      <material name="red"/>
    </visual>
  </link>

  <!-- Joints -->
  <!-- Front Left -->
  <joint name="joint_left_front" type="continuous">
    <parent link="base_link"/>
    <child link="left_front_wheel"/>
    <origin xyz="0.15 0.178 0"/>
    <axis xyz="0 1 0"/>
  </joint>

  <!-- Front Right -->
  <joint name="joint_right_front" type="continuous">
    <parent link="base_link"/>
    <child link="right_front_wheel"/>
    <origin xyz="0.15 -0.178 0"/>
    <axis xyz="0 1 0"/>
  </joint>

  <!-- Rear Left -->
  <joint name="joint_left_rear" type="continuous">
    <parent link="base_link"/>
    <child link="left_rear_wheel"/>
    <origin xyz="-0.15 0.178 0"/>
    <axis xyz="0 1 0"/>
  </joint>

  <!-- Rear Right -->
  <joint name="joint_right_rear" type="continuous">
    <parent link="base_link"/>
    <child link="right_rear_wheel"/>
    <origin xyz="-0.15 -0.178 0"/>
    <axis xyz="0 1 0"/>
  </joint>
</robot>

Credits

Shivank Rao
2 projects • 0 followers
ECE grad with hands-on embedded systems, firmware, RT comms; HAL avionics exposure, system-level dev & optimization enthusiast.

Comments

Related channels and tags
  • Arduino
  • Raspberry Pi
  • Robotics
  • Robotics
  • ROS