使用xacro模块化建模

定义常量:

    <xacro:property name="M_PI" value="3.1415926"/>
    <xacro:property name="base_mass"   value="20" /> 
    <xacro:property name="base_radius" value="0.20"/>
    <xacro:property name="base_length" value="0.16"/>

    <xacro:property name="wheel_mass"   value="2" />
    <xacro:property name="wheel_radius" value="0.06"/>
    <xacro:property name="wheel_length" value="0.025"/>
    <xacro:property name="wheel_joint_y" value="0.19"/>
    <xacro:property name="wheel_joint_z" value="0.05"/>

    <xacro:property name="caster_mass"    value="0.5" /> 
    <xacro:property name="caster_radius"  value="0.015"/> <!-- wheel_radius - ( base_length/2 - wheel_joint_z) -->
    <xacro:property name="caster_joint_x" value="0.18"/>

定义颜色:

    <!-- Defining the colors used in this robot -->
    <material name="yellow">
        <color rgba="1 0.4 0 1"/>
    </material>
    <material name="black">
        <color rgba="0 0 0 0.95"/>
    </material>
    <material name="gray">
        <color rgba="0.75 0.75 0.75 1"/>
    </material>

宏定义:

<xacro:macro name="sphere_inertial_matrix" params="m r">

   <!-- Macro for robot wheel -->
    <xacro:macro name="wheel" params="prefix1 prefix2 reflect1 reflect2">
        <joint name="${prefix1}_${prefix2}_wheel_joint" type="continuous">
            <axis xyz="0 0 1"/>  
            <origin xyz="${reflect1}  ${reflect2} -0.05" rpy="0 1.57075 0"/>
            <parent link="base_link"/>
            <child link="${prefix1}_${prefix2}_wheel_link"/>
        </joint>

        <link name="${prefix1}_${prefix2}_wheel_link">
            <visual>
                <geometry>
                    <cylinder radius="${wheel_radius}" length = "${wheel_length}"/>
                </geometry>
                <material name="gray" />
            </visual>
            <collision>
                <geometry>
                    <cylinder radius="${wheel_radius}" length = "${wheel_length}"/>
                </geometry>
            </collision>
            <cylinder_inertial_matrix  m="${wheel_mass}" r="${wheel_radius}" h="${wheel_length}" />
        </link>

        <gazebo reference="${prefix1}_${prefix2}_wheel_link">
            <material>Gazebo/Gray</material>
        </gazebo>

   <!-- Macro for inertia matrix -->
    <xacro:macro name="sphere_inertial_matrix" params="m r">
        <inertial>
            <mass value="${m}" />
            <inertia ixx="${2*m*r*r/5}" ixy="0" ixz="0"
                iyy="${2*m*r*r/5}" iyz="0" 
                izz="${2*m*r*r/5}" />
        </inertial>
    </xacro:macro>

    <xacro:macro name="cylinder_inertial_matrix" params="m r h">
        <inertial>
            <mass value="${m}" />
            <inertia ixx="${m*(3*r*r+h*h)/12}" ixy = "0" ixz = "0"
                iyy="${m*(3*r*r+h*h)/12}" iyz = "0"
                izz="${m*r*r/2}" /> 
        </inertial>
    </xacro:macro>

宏调用

<cylinder_inertial_matrix  m="${wheel_mass}" r="${wheel_radius}" h="${wheel_length}" />
<wheel prefix1="front"  prefix2="left" reflect1="-0.15" reflect2="0.15"/>
<wheel prefix1="front"  prefix2="right" reflect1="0.15" reflect2="0.15"/>
<wheel prefix1="back"  prefix2="left" reflect1="-0.15" reflect2="-0.15"/>
<wheel prefix1="back"  prefix2="right" reflect1="0.15" reflect2="-0.15"/>

文件包含

调用其他已定义好的模型, 可以实现模块化建模

<xacro:include filename="$(find mbot_description)/urdf/mbot_base_gazebo.xacro" />

优化物理模型

为了实现物理仿真，需要对模型添加惯性参数和碰撞属性

            <collision>
                <origin xyz="0 0 0" rpy="${M_PI/2} 0 0" />
                <geometry>
                    <cylinder radius="${wheel_radius}" length = "${wheel_length}"/>
                </geometry>
            </collision>
            <cylinder_inertial_matrix  m="${wheel_mass}" r="${wheel_radius}" h="${wheel_length}" />
        </link>

碰撞属性一般是指其碰撞的面积，为了便于计算，可以将其简化为规则形状

为link添加gazebo标签

gazebo中标签无颜色，需在此设置

        <gazebo reference="base_link">
            <material>Gazebo/Blue</material>
        </gazebo>

为jiont添加传动装置 （相当于电机）

        <transmission name="${prefix}_wheel_joint_trans">
            <type>transmission_interface/SimpleTransmission</type>
            <joint name="${prefix}_wheel_joint" >
                <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
            </joint>
            <actuator name="${prefix}_wheel_joint_motor">
                <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
                <mechanicalReduction>1</mechanicalReduction>
            </actuator>
        </transmission>

添加gazebo控制器插件

        <!-- Drive controller -->
    <gazebo>
    <plugin name="skid_steer_drive_controller" filename="libgazebo_ros_skid_steer_drive.so">
        <updateRate>100.0</updateRate>
        <robotNamespace>/</robotNamespace>
        <leftFrontJoint>front_left_wheel_joint</leftFrontJoint>
        <rightFrontJoint>front_right_wheel_joint</rightFrontJoint>
        <leftRearJoint>back_left_wheel_joint</leftRearJoint>
        <rightRearJoint>back_right_wheel_joint</rightRearJoint>
        <wheelSeparation>4</wheelSeparation>
        <wheelDiameter>0.1</wheelDiameter>
        <robotBaseFrame>base_link</robotBaseFrame>
        <torque>1</torque>
        <topicName>cmd_vel</topicName>
        <broadcastTF>0</broadcastTF>
    </plugin>
    </gazebo>

具体参数设置: http://gazebosim.org/tutorials?tut=ros_gzplugins#DifferentialDrive

也可以采用Ackermann转向驱动。

添加传感器仿真

可以使用gazebo的传感器模型，然后在主模型文件中添加该模型到base_link上

其他模型详见:Plugins available in gazebo_plugins

http://gazebosim.org/tutorials?tut=ros_gzplugins#OpenniKinect

<?xml version="1.0"?>
<robot name="my_car" xmlns:xacro="http://www.ros.org/wiki/xacro">

    <xacro:include filename="$(find my_car)/urdf/my_car_base.xacro" />
    <xacro:include filename="$(find my_car)/urdf/sensors/kinect_gazebo.xacro" />
    <xacro:include filename="$(find my_car)/urdf/sensors/camera_gazebo.xacro" />

    <xacro:property name="kinect_offset_x" value="0" />
    <xacro:property name="kinect_offset_y" value="0.2" />
    <xacro:property name="kinect_offset_z" value="0.11" />

    <!-- kinect -->
    <joint name="kinect_joint" type="fixed">
        <origin xyz="${kinect_offset_x} ${kinect_offset_y} ${kinect_offset_z}" rpy="0 0 1.57" />
        <parent link="base_link"/>
        <child link="kinect_link"/>
    </joint>


    <!-- Camera -->
    <xacro:kinect_camera prefix="kinect"/>
    <xacro:property name="camera_offset_x" value="0.17" />
    <xacro:property name="camera_offset_y" value="0" />
    <xacro:property name="camera_offset_z" value="0.10" />


    <joint name="camera_joint" type="fixed">
        <origin xyz="${camera_offset_x} ${camera_offset_y} ${camera_offset_z}" rpy="0 0 0" />
        <parent link="base_link"/>
        <child link="camera_link"/>
    </joint>

    <xacro:usb_camera prefix="camera"/>

    <my_car_base/>

</robot>

启动文件

<launch>
    <!-- 设置launch文件的参数 -->
    <arg name="world_name" value="$(find my_car)/worlds/playground.world"/>
    <arg name="paused" default="false"/>
    <arg name="use_sim_time" default="true"/>
    <arg name="gui" default="true"/>
    <arg name="headless" default="false"/>
    <arg name="debug" default="false"/>

    <!-- 运行gazebo仿真环境 -->
    <include file="$(find gazebo_ros)/launch/empty_world.launch">
        <arg name="world_name" value="$(arg world_name)" />
        <arg name="debug" value="$(arg debug)" />
        <arg name="gui" value="$(arg gui)" />
        <arg name="paused" value="$(arg paused)"/>
        <arg name="use_sim_time" value="$(arg use_sim_time)"/>
        <arg name="headless" value="$(arg headless)"/>
    </include>

    <!-- 加载机器人模型描述参数 -->
    <param name="robot_description" command="$(find xacro)/xacro --inorder '$(find my_car)/urdf/my_car_base_with_rgbd.xacro'" />

      <!-- run node joint-state-pub，publish joint_state  -->
    <node name="joint_state_publisher_gui" pkg = "joint_state_publisher_gui" type = "joint_state_publisher_gui" />

     <!--run node robot_state_publisher, publish tf-->
    <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher"  output="screen" >
        <param name="publish_frequency" type="double" value="50.0" />
    </node>

    <!-- 在gazebo中加载机器人模型-->
    <node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model" respawn="false" output="screen"
          args="-urdf -model my_car -param robot_description"/> 

      <!--run rviz-->
     <node name="rviz" pkg = "rviz" type = "rviz" args = "-d $(find my_car)/config/my_car_with_rgbd.rviz" />   
</launch>

： 中只需要修改path. ：同上，只需修改path ：同上 ：同上（但可以不添加）

其他可以不用修改，下次直接使用

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