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Physics Simulation with Gazebo

🌍 Introduction to Gazebo​

Gazebo is a powerful 3D robot simulator that provides accurate physics simulation, realistic sensor feedback, and integration with ROS 2.

🏗️ Creating a Gazebo World​

<?xml version="1.0"?>
<sdf version="1.6">
  <world name="humanoid_world">
    <include>
      <uri>model://sun</uri>
    </include>
    <include>
      <uri>model://ground_plane</uri>
    </include>
    
    <!-- Add obstacles -->
    <model name="box_obstacle">
      <pose>2 0 0.5 0 0 0</pose>
      <link name="link">
        <collision name="collision">
          <geometry>
            <box><size>1 1 1</size></box>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <box><size>1 1 1</size></box>
          </geometry>
        </visual>
      </link>
    </model>
  </world>
</sdf>

⚙️ Physics Engines​

Gazebo supports multiple physics engines:

  • ODE (default): Fast, good for most applications
  • Bullet: Better collision detection
  • DART: Advanced dynamics
  • Simbody: Biomechanical simulations

🤖 Spawning Robots​

import rclpy
from rclpy.node import Node
from gazebo_msgs.srv import SpawnEntity
import os

class RobotSpawner(Node):
    def __init__(self):
        super().__init__('robot_spawner')
        self.client = self.create_client(SpawnEntity, '/spawn_entity')
        
        while not self.client.wait_for_service(timeout_sec=1.0):
            self.get_logger().info('Waiting for spawn service...')
        
        self.spawn_robot()
    
    def spawn_robot(self):
        request = SpawnEntity.Request()
        request.name = 'my_humanoid'
        request.xml = open('path/to/robot.urdf', 'r').read()
        request.initial_pose.position.z = 1.0
        
        future = self.client.call_async(request)
        rclpy.spin_until_future_complete(self, future)
        
        if future.result() is not None:
            self.get_logger().info('Robot spawned successfully!')

🎯 Key Takeaways​

  • Gazebo provides realistic physics simulation
  • Supports multiple physics engines
  • Integrates seamlessly with ROS 2
  • Essential for testing before hardware deployment

Next: Unity Rendering →