构建机器人仿真平台

一、URDF模型改写为xacro文件

将之前的机器人URDF模型，改写成xacro文件，创建仿真环境，将机器人模型加载到Gazebo仿真环境中，完成运动控制的仿真。

在./mbot_description/urdf文件夹中创建mbot_base_gazebo_automobile.xacro文件，代码如下：

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

    <!-- PROPERTY LIST -->
    <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="0.40"/>
    <xacro:property name="base_width" value="0.20"/>
    <xacro:property name="base_height" 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_x" value="0.1"/>
    <xacro:property name="wheel_joint_y" value="0.1"/>
    <xacro:property name="wheel_joint_z" value="0.08"/>

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

    <xacro:property name="update_rate" value="100.0"/> <!-- controller-->


    <!-- 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>
    
    <!-- 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>

    <!-- Macro for robot wheel -->
    <xacro:macro name="wheel" params="prefix reflect orientation">
        <joint name="${prefix}_wheel_joint" type="continuous">
            <origin xyz="${orientation*wheel_joint_x} ${reflect*wheel_joint_y} ${-wheel_joint_z}" rpy="0 0 0"/>
            <parent link="base_link"/>
            <child link="${prefix}_wheel_link"/>
            <axis xyz="0 1 0"/>
        </joint>

        <link name="${prefix}_wheel_link">
            <visual>
                <origin xyz="0 0 0" rpy="${M_PI/2} 0 0" />
                <geometry>
                    <cylinder radius="${wheel_radius}" length = "${wheel_length}"/>
                </geometry>
                <material name="gray" />
            </visual>
            <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>

        <gazebo reference="${prefix}_wheel_link">
            <material>Gazebo/Gray</material>
        </gazebo>

        <!-- Transmission is important to link the joints and the controller -->
        <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>
    </xacro:macro>


    <xacro:macro name="mbot_base_gazebo">
        <link name="base_footprint">
            <visual>
                <origin xyz="0 0 0" rpy="0 0 0" />
                <geometry>
                    <box size="0.001 0.001 0.001" />
                </geometry>
            </visual>
        </link>
        <gazebo reference="base_footprint">
            <turnGravityOff>false</turnGravityOff>
        </gazebo>

        <joint name="base_footprint_joint" type="fixed">
            <origin xyz="0 0 ${base_length/2 + caster_radius*2}" rpy="0 0 0" />        
            <parent link="base_footprint"/>
            <child link="base_link" />
        </joint>

        <link name="base_link">
            <visual>
                <origin xyz=" 0 0 0" rpy="0 0 0" />
                <geometry>
                    <box size="${base_length} ${base_width} ${base_height}"/>
                </geometry>
                <material name="yellow" />
            </visual>
            <collision>
                <origin xyz=" 0 0 0" rpy="0 0 0" />
                <geometry>
                    <box size="${base_length} ${base_width} ${base_height}"/>
                </geometry>
            </collision>   
            <cylinder_inertial_matrix  m="${base_mass}" r="${base_radius}" h="${base_length}" />
        </link>

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

        <wheel prefix="back_left"  reflect="-1" orientation="-1"/>
        <wheel prefix="back_right" reflect="1"  orientation="-1"/>
        <wheel prefix="front_left"  reflect="-1" orientation="1"/>
        <wheel prefix="front_right" reflect="1"  orientation="1" />

        <!-- controller -->
        <gazebo>
            <plugin name="skid_steer_drive_controller" 
                    filename="libgazebo_ros_skid_steer_drive.so">
                <rosDebugLevel>Debug</rosDebugLevel>
                <publishWheelTF>true</publishWheelTF>
                <robotNamespace>/</robotNamespace>
                <publishTf>1</publishTf>
                <publishWheelJointState>true</publishWheelJointState>
                <alwaysOn>true</alwaysOn>
                <updateRate>${update_rate}</updateRate>
                <legacyMode>true</legacyMode>

                <leftFrontJoint>front_left_wheel_joint</leftFrontJoint>
                <rightFrontJoint>front_right_wheel_joint</rightFrontJoint>
                <leftRearJoint>back_left_wheel_joint</leftRearJoint>
                <rightRearJoint>back_right_wheel_joint</rightRearJoint>

                <covariance_x>0.000100</covariance_x>
                <covariance_y>0.000100</covariance_y>
                <covariance_yaw>0.010000</covariance_yaw>

                <wheelSeparation>${wheel_joint_y*2}</wheelSeparation>
                <wheelDiameter>${2*wheel_radius}</wheelDiameter>
                <broadcastTF>true</broadcastTF>          <!--need turn on-->
                <torque>30</torque>                       <!--\'wheelTorque\' is renamed \'torque\'-->
                <wheelAcceleration>1.8</wheelAcceleration>
                <commandTopic>cmd_vel</commandTopic>                <!--topicName-->
                <odometryFrame>odom</odometryFrame> 
                <odometryTopic>odom</odometryTopic> 
                <robotBaseFrame>base_footprint</robotBaseFrame>
            </plugin>
        </gazebo> 
    </xacro:macro>

</robot>

运动控制的仿真效果如下：

二、小车模型上添加摄像头和激光雷达

2.1 模型加载到Gazebo，进行仿真

在./mbot_description/urdf文件夹中创建mbot_with_sensor_gazebo_automobile.xacro文件，代码如下：

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

    <xacro:include filename="$(find mbot_description)/urdf/mbot_base_gazebo_automobile.xacro" />
    <xacro:include filename="$(find mbot_description)/urdf/sensors/camera_gazebo.xacro" />
    <xacro:include filename="$(find mbot_description)/urdf/sensors/lidar_gazebo.xacro" />

    <xacro:property name="camera_offset_x" value="0.17" />
    <xacro:property name="camera_offset_y" value="-0.05" />
    <xacro:property name="camera_offset_z" value="0.10" />

    <xacro:property name="lidar_offset_x" value="0" />
    <xacro:property name="lidar_offset_y" value="0" />
    <xacro:property name="lidar_offset_z" value="0.105" />

    <!-- Camera -->
    <joint name="left_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="left_camera_link"/>
    </joint>

    <joint name="right_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="right_camera_link"/>
    </joint>

    <xacro:usb_camera prefix="left_camera"/>
    <xacro:usb_camera prefix="right_camera"/>

    <!-- Lidar-->
    <joint name="lidar_joint" type="fixed">
        <origin xyz="${lidar_offset_x} ${lidar_offset_y} ${lidar_offset_z}" rpy="0 0 0" />
        <parent link="base_link"/>
        <child link="laser_link"/>
    </joint>

    <xacro:rplidar prefix="laser"/>

    <mbot_base_gazebo/>

</robot>

运行效果如下：

2.2 激光雷达

激光雷达的参数文件为./mbot_description/urdf/sensors/lidar_gazebo.xacro，内容如下：

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

    <xacro:macro name="rplidar" params="prefix:=laser">
        <!-- Create laser reference frame -->
        <link name="${prefix}_link">
            <inertial>
                <mass value="0.1" />
                <origin xyz="0 0 0" />
                <inertia ixx="0.01" ixy="0.0" ixz="0.0"
                         iyy="0.01" iyz="0.0"
                         izz="0.01" />
            </inertial>

            <visual>
                <origin xyz=" 0 0 0 " rpy="0 0 0" />
                <geometry>
                    <cylinder length="0.05" radius="0.05"/>
                </geometry>
                <material name="black"/>
            </visual>

            <collision>
                <origin xyz="0.0 0.0 0.0" rpy="0 0 0" />
                <geometry>
                    <cylinder length="0.06" radius="0.05"/>
                </geometry>
            </collision>
        </link>
        <gazebo reference="${prefix}_link">
            <material>Gazebo/Black</material>
        </gazebo>

        <gazebo reference="${prefix}_link">
            <sensor type="ray" name="rplidar">
                <pose>0 0 0 0 0 0</pose>
                <visualize>false</visualize>
                <update_rate>5.5</update_rate>
                <ray>
                    <scan>
                      <horizontal>
                        <samples>360</samples>
                        <resolution>1</resolution>
                        <min_angle>-3</min_angle>
                        <max_angle>3</max_angle>
                      </horizontal>
                    </scan>
                    <range>
                      <min>0.10</min>
                      <max>6.0</max>
                      <resolution>0.01</resolution>
                    </range>
                    <noise>
                      <type>gaussian</type>
                      <mean>0.0</mean>
                      <stddev>0.01</stddev>
                    </noise>
                </ray>
                <plugin name="gazebo_rplidar" filename="libgazebo_ros_laser.so">
                    <topicName>/scan</topicName>
                    <frameName>laser_link</frameName>
                </plugin>
            </sensor>
        </gazebo>

    </xacro:macro>
</robot>

2.3 相机

相机的参数文件为./mbot_description/urdf/sensors/camera_gazebo.xacro，内容如下：

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

    <xacro:macro name="usb_camera" params="prefix:=camera">
        <!-- Create laser reference frame -->
        <link name="${prefix}_link">
            <inertial>
                <mass value="0.1" />
                <origin xyz="0 0 0" />
                <inertia ixx="0.01" ixy="0.0" ixz="0.0"
                         iyy="0.01" iyz="0.0"
                         izz="0.01" />
            </inertial>

            <visual>
                <origin xyz=" 0 0 0 " rpy="0 0 0" />
                <geometry>
                    <box size="0.01 0.04 0.04" />
                </geometry>
                <material name="black"/>
            </visual>

            <collision>
                <origin xyz="0.0 0.0 0.0" rpy="0 0 0" />
                <geometry>
                    <box size="0.01 0.04 0.04" />
                </geometry>
            </collision>
        </link>
        <gazebo reference="${prefix}_link">
            <material>Gazebo/Black</material>
        </gazebo>

        <gazebo reference="${prefix}_link">
            <sensor type="camera" name="camera_node">
                <update_rate>30.0</update_rate>
                <camera name="head">
                    <horizontal_fov>1.3962634</horizontal_fov>
                    <image>
                        <width>1280</width>
                        <height>720</height>
                        <format>R8G8B8</format>
                    </image>
                    <clip>
                        <near>0.02</near>
                        <far>300</far>
                    </clip>
                    <noise>
                        <type>gaussian</type>
                        <mean>0.0</mean>
                        <stddev>0.007</stddev>
                    </noise>
                </camera>
                <plugin name="gazebo_camera" filename="libgazebo_ros_camera.so">
                    <alwaysOn>true</alwaysOn>
                    <updateRate>0.0</updateRate>
                    <cameraName>${prefix}/camera</cameraName>
                    <imageTopicName>image_raw</imageTopicName>
                    <cameraInfoTopicName>camera_info</cameraInfoTopicName>
                    <frameName>camera_link</frameName>
                    <hackBaseline>0.07</hackBaseline>
                    <distortionK1>0.0</distortionK1>
                    <distortionK2>0.0</distortionK2>
                    <distortionK3>0.0</distortionK3>
                    <distortionT1>0.0</distortionT1>
                    <distortionT2>0.0</distortionT2>
                </plugin>
            </sensor>
        </gazebo>

    </xacro:macro>
</robot>

2.4 Rviz中显示相机和激光雷达的数据