Surface and collision properties

Surface and collision properties

The simulation objects can include collision properties such as friction, bounce and contact parameters set to an individual link.

from pcg_gazebo.simulation import create_object

# If there is a Gazebo instance running, you can spawn the box into the simulation
from pcg_gazebo.task_manager import Server
# First create a simulation server
server = Server()
# Create a simulation manager named default
server.create_simulation('friction')
simulation = server.get_simulation('friction')
# Run an instance of the empty.world scenario
# This is equivalent to run
#      roslaunch gazebo_ros empty_world.launch
# with all default parameters
simulation.create_gazebo_empty_world_task()
# A task named 'gazebo' the added to the tasks list
print(simulation.get_task_list())
# But it is still not running
print('Is Gazebo running: {}'.format(simulation.is_task_running('gazebo')))
# Run Gazebo
simulation.run_all_tasks()

['gazebo']
Is Gazebo running: False

from pcg_gazebo.generators import WorldGenerator
import random
# Create a Gazebo proxy
gazebo_proxy = simulation.get_gazebo_proxy()

# Use the generator to spawn the model to the Gazebo instance running at the moment
generator = WorldGenerator(gazebo_proxy=gazebo_proxy)

Friction

obj = create_object('box')
# By changing the size, collision, visual and inertial 
# properties are already going to be updated
obj.size = [0.8, 0.7, 0.9]
obj.add_inertial(30)

# Print the initial state of a box in the model option
print(obj.to_sdf('model'))

<model name="box">
  <link name="box">
    <inertial>
      <inertia>
        <izz>2.825</izz>
        <iyz>0.0</iyz>
        <iyy>3.6250000000000004</iyy>
        <ixx>3.25</ixx>
        <ixy>0.0</ixy>
        <ixz>0.0</ixz>
      </inertia>
      <mass>30.0</mass>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </inertial>
    <visual name="visual">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <transparency>0.0</transparency>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
      <cast_shadows>1</cast_shadows>
    </visual>
    <collision name="collision">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <max_contacts>10</max_contacts>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </collision>
  </link>
  <allow_auto_disable>0</allow_auto_disable>
  <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
  <static>0</static>
</model>

# Set default friction parameters
obj.collision.enable_property('friction')
print(obj.to_sdf('model'))

<model name="box">
  <link name="box">
    <inertial>
      <inertia>
        <izz>2.825</izz>
        <iyz>0.0</iyz>
        <iyy>3.6250000000000004</iyy>
        <ixx>3.25</ixx>
        <ixy>0.0</ixy>
        <ixz>0.0</ixz>
      </inertia>
      <mass>30.0</mass>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </inertial>
    <visual name="visual">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <transparency>0.0</transparency>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
      <cast_shadows>1</cast_shadows>
    </visual>
    <collision name="collision">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <max_contacts>10</max_contacts>
      <surface>
        <friction>
          <torsional>
            <use_patch_radius>1</use_patch_radius>
            <ode>
              <slip>0</slip>
            </ode>
            <surface_radius>0</surface_radius>
            <patch_radius>0</patch_radius>
            <coefficient>1</coefficient>
          </torsional>
          <ode>
            <fdir1>0 0 0</fdir1>
            <mu>1</mu>
            <slip2>0</slip2>
            <mu2>1</mu2>
            <slip1>0</slip1>
          </ode>
          <bullet>
            <rolling_friction>1</rolling_friction>
            <friction>1</friction>
            <fdir1>0 0 0</fdir1>
            <friction2>1</friction2>
          </bullet>
        </friction>
      </surface>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </collision>
  </link>
  <allow_auto_disable>0</allow_auto_disable>
  <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
  <static>0</static>
</model>

obj.collision.set_ode_friction_params(
    mu=0.9,
    mu2=0.5,
    slip1=0.3, 
    slip2=0.5,
    fdir1=[0, 0, 0]
)
print(obj.to_sdf('model'))

<model name="box">
  <link name="box">
    <inertial>
      <inertia>
        <izz>2.825</izz>
        <iyz>0.0</iyz>
        <iyy>3.6250000000000004</iyy>
        <ixx>3.25</ixx>
        <ixy>0.0</ixy>
        <ixz>0.0</ixz>
      </inertia>
      <mass>30.0</mass>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </inertial>
    <visual name="visual">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <transparency>0.0</transparency>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
      <cast_shadows>1</cast_shadows>
    </visual>
    <collision name="collision">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <max_contacts>10</max_contacts>
      <surface>
        <friction>
          <torsional>
            <use_patch_radius>1</use_patch_radius>
            <ode>
              <slip>0</slip>
            </ode>
            <surface_radius>0</surface_radius>
            <patch_radius>0</patch_radius>
            <coefficient>1</coefficient>
          </torsional>
          <ode>
            <slip1>0.3</slip1>
            <mu>0.9</mu>
            <slip2>0.5</slip2>
            <mu2>0.5</mu2>
            <fdir1>0 0 0</fdir1>
          </ode>
          <bullet>
            <rolling_friction>1</rolling_friction>
            <friction>1</friction>
            <fdir1>0 0 0</fdir1>
            <friction2>1</friction2>
          </bullet>
        </friction>
      </surface>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </collision>
  </link>
  <allow_auto_disable>0</allow_auto_disable>
  <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
  <static>0</static>
</model>

obj.collision.set_bullet_friction_params(
    friction=0.8, 
    friction2=0.9, 
    fdir1=[0, 0, 0], 
    rolling_friction=1
)
print(obj.to_sdf('model'))

<model name="box">
  <link name="box">
    <inertial>
      <inertia>
        <izz>2.825</izz>
        <iyz>0.0</iyz>
        <iyy>3.6250000000000004</iyy>
        <ixx>3.25</ixx>
        <ixy>0.0</ixy>
        <ixz>0.0</ixz>
      </inertia>
      <mass>30.0</mass>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </inertial>
    <visual name="visual">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <transparency>0.0</transparency>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
      <cast_shadows>1</cast_shadows>
    </visual>
    <collision name="collision">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <max_contacts>10</max_contacts>
      <surface>
        <friction>
          <torsional>
            <use_patch_radius>1</use_patch_radius>
            <ode>
              <slip>0</slip>
            </ode>
            <surface_radius>0</surface_radius>
            <patch_radius>0</patch_radius>
            <coefficient>1</coefficient>
          </torsional>
          <ode>
            <slip1>0.3</slip1>
            <mu>0.9</mu>
            <slip2>0.5</slip2>
            <mu2>0.5</mu2>
            <fdir1>0 0 0</fdir1>
          </ode>
          <bullet>
            <rolling_friction>1.0</rolling_friction>
            <friction>0.8</friction>
            <fdir1>0 0 0</fdir1>
            <friction2>0.9</friction2>
          </bullet>
        </friction>
      </surface>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </collision>
  </link>
  <allow_auto_disable>0</allow_auto_disable>
  <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
  <static>0</static>
</model>

# Set default bounce parameters
obj.collision.enable_property('bounce')
print(obj.to_sdf('model'))

<model name="box">
  <link name="box">
    <inertial>
      <inertia>
        <izz>2.825</izz>
        <iyz>0.0</iyz>
        <iyy>3.6250000000000004</iyy>
        <ixx>3.25</ixx>
        <ixy>0.0</ixy>
        <ixz>0.0</ixz>
      </inertia>
      <mass>30.0</mass>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </inertial>
    <visual name="visual">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <transparency>0.0</transparency>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
      <cast_shadows>1</cast_shadows>
    </visual>
    <collision name="collision">
      <geometry>
        <box>
          <size>0.8 0.7 0.9</size>
        </box>
      </geometry>
      <max_contacts>10</max_contacts>
      <surface>
        <friction>
          <torsional>
            <use_patch_radius>1</use_patch_radius>
            <ode>
              <slip>0</slip>
            </ode>
            <surface_radius>0</surface_radius>
            <patch_radius>0</patch_radius>
            <coefficient>1</coefficient>
          </torsional>
          <ode>
            <slip1>0.3</slip1>
            <mu>0.9</mu>
            <slip2>0.5</slip2>
            <mu2>0.5</mu2>
            <fdir1>0 0 0</fdir1>
          </ode>
          <bullet>
            <rolling_friction>1.0</rolling_friction>
            <friction>0.8</friction>
            <fdir1>0 0 0</fdir1>
            <friction2>0.9</friction2>
          </bullet>
        </friction>
        <bounce>
          <restitution_coefficient>0</restitution_coefficient>
          <threshold>100000</threshold>
        </bounce>
      </surface>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
    </collision>
  </link>
  <allow_auto_disable>0</allow_auto_disable>
  <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
  <static>0</static>
</model>

mu = [0.1, 0.3, 0.5, 0.7, 1.0] 
for i in range(len(mu)):
    obj.collision.set_ode_friction_params(
        mu=mu[i],
        mu2=mu[i])

    generator.spawn_model(
        model=obj, 
        robot_namespace='box_mu_{}'.format(mu[i]),
        pos=[0, i, 2])

from time import sleep
sleep(2)

for i in range(len(mu)):
    gazebo_proxy.apply_body_wrench(
        model_name='box_mu_{}'.format(mu[i]),
        link_name='box',
        force=[300, 0, 0],
        torque=[0, 0, 0],
        start_time=0,
        duration=2
        )

# End the simulation by killing the Gazebo task
sleep(5)
simulation.kill_all_tasks()

The cuboids are created with different friction parameters and therefore will travel different distances when subjected to a horizontal force applied on their center of mass.