文章目录

  • 前言 
    一、创建编译功能包 
    二、xacro文件 
    1、更新robot_base.xacro文件 
    三、启动模型 
    四、键盘控制 
    五、总结 

前言

所谓滑移转向，对机器人机身两侧轮子分别进行驱动，通过不同的转速，完成机器人的转向。

一、创建编译功能包

切换到catkin_ws/src目录下，如下：

catkin_create_pkg mbot_sim_gazebo_move urdf xacro

切换到catkin_ws目录下，编译该功能包，如下：

catkin_make mbot_sim_gazebo_move

在该功能包下创建include、src、launch、urdf文件夹，在urdf文件下创建urdf文件夹和xacro文件夹。

二、xacro文件

1、更新robot_base.xacro文件

切换到xacro文件下，更新robot_base文件，文件内容如下：

<?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="0.16"/>

    <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"/>

    <!-- 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">
        <joint name="${prefix}_wheel_joint" type="continuous">
            <origin xyz="0 ${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>

    <!-- Macro for robot caster -->
    <xacro:macro name="caster" params="prefix reflect">
        <joint name="${prefix}_caster_joint" type="continuous">
            <origin xyz="${reflect*caster_joint_x} 0 ${-(base_length/2 + caster_radius)}" rpy="0 0 0"/>
            <parent link="base_link"/>
            <child link="${prefix}_caster_link"/>
            <axis xyz="0 1 0"/>
        </joint>

        <link name="${prefix}_caster_link">
            <visual>
                <origin xyz="0 0 0" rpy="0 0 0"/>
                <geometry>
                    <sphere radius="${caster_radius}" />
                </geometry>
                <material name="black" />
            </visual>
            <collision>
                <origin xyz="0 0 0" rpy="0 0 0"/>
                <geometry>
                    <sphere radius="${caster_radius}" />
                </geometry>
            </collision>      
            <sphere_inertial_matrix  m="${caster_mass}" r="${caster_radius}" />
        </link>

        <gazebo reference="${prefix}_caster_link">
            <material>Gazebo/Black</material>
        </gazebo>
    </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>
                    <cylinder length="${base_length}" radius="${base_radius}"/>
                </geometry>
                <material name="yellow" />
            </visual>
            <collision>
                <origin xyz=" 0 0 0" rpy="0 0 0" />
                <geometry>
                    <cylinder length="${base_length}" radius="${base_radius}"/>
                </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="left"  reflect="-1"/>
        <wheel prefix="right" reflect="1"/>

        <caster prefix="front" reflect="-1"/>
        <caster prefix="back"  reflect="1"/>

        <!-- controller -->
        <gazebo>
            <plugin name="differential_drive_controller" 
                    filename="libgazebo_ros_diff_drive.so">
                <rosDebugLevel>Debug</rosDebugLevel>
                <publishWheelTF>true</publishWheelTF>
                <robotNamespace>/</robotNamespace>
                <publishTf>1</publishTf>
                <publishWheelJointState>true</publishWheelJointState>
                <alwaysOn>true</alwaysOn>
                <updateRate>100.0</updateRate>
                <legacyMode>true</legacyMode>
                <leftJoint>left_wheel_joint</leftJoint>
                <rightJoint>right_wheel_joint</rightJoint>
                <wheelSeparation>${wheel_joint_y*2}</wheelSeparation>
                <wheelDiameter>${2*wheel_radius}</wheelDiameter>
                <broadcastTF>1</broadcastTF>
                <wheelTorque>30</wheelTorque>
                <wheelAcceleration>1.8</wheelAcceleration>
                <commandTopic>cmd_vel</commandTopic>
                <odometryFrame>odom</odometryFrame> 
                <odometryTopic>odom</odometryTopic> 
                <robotBaseFrame>base_footprint</robotBaseFrame>
            </plugin>
        </gazebo> 
    </xacro:macro>
</robot>

三、启动模型

此时的模型带有滑移转向控制器和地图，通过如下命令启动：

roslaunch mbot_sim_gazebo_move robot_gazebo_wg.launch

四、键盘控制

该节点在teleop_twist_keyboard功能包中，需要通过如下命令安装：

sudo apt-get install ros-melodic-teleop-twist-keyboard
rosstack profile
rospack profile

然后通过如下命令，运行该节点：

rosrun teleop_twist_keyboard teleop_twist_keyboard.py

效果如下：

可以看到出现一个带有命令提示的命令行窗口，可以使用u，i，o，j，k，l，m，“<”，“>””等按键移动机器人并设置速度。

各个按键及其功能如下：
U I O
J K L
M < >
K—停止
I、J、<、L—前、左转、后、右转
q/z : 最大速度增加/减少10%
w/x : 仅线性速度增加10%
e/c : 仅角速度增加10%

五、总结

可以通过上述方法，驾驶机器人穿越整个房间，但是我怎么赶脚操控有点难度。。。至此，一个自定义移动机器人的建模与仿真基本结束，下一篇开始接触导航，加油啊。