ROS Gazebo（四）：ROS Control

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如何设置模拟控制器来驱动机器人关节？

必须预先安装 ros_control, ros_controllers。

一、RSO Control

这里写图片描述

ros_control 功能包以关节驱动器上的编码器或者输入值为关节状态的输入，通过闭环反馈（如PID）控制来控制输出（如力矩）。并通过transmissions来完成物理系统到关节位置、力矩等的映射。

1、控制器

控制器插件如下：

effort_controllers
–joint_effort_controller
–joint_position_controller
–joint_velocity_controller
joint_state_controller
–joint_state_controller
position_controllers
–joint_position_controller
velocity_controllers
–joint_velocity_controller

还可以创建自己的控制器

2、硬件接口

硬件接口如下：

Joint Command Interfaces
–Effort Joint Interface
–Velocity Joint Interface
–Position Joint Interface
Joint State Interfaces
Actuator State Interfaces
Actuator Command Interfaces
–Effort Actuator Interface
–Velocity Actuator Interface
–Position Actuator Interface
Force-torque sensor Interface
IMU sensor Interface

还可以创建自己的硬件接口

二、gazebo

1、ros_control 和 Gazebo 的数据流图

包括仿真、硬件、控制器和变换。

这里写图片描述

2、添加 `transmission` 组件

 <transmission name="tran1">    <type>transmission_interface/SimpleTransmission</type>    <joint name="joint1">      <hardwareInterface>EffortJointInterface</hardwareInterface>    </joint>    <actuator name="motor1">      <hardwareInterface>EffortJointInterface</hardwareInterface>      <mechanicalReduction>1</mechanicalReduction>    </actuator>  </transmission>  <transmission name="tran2">    <type>transmission_interface/SimpleTransmission</type>    <joint name="joint2">      <hardwareInterface>EffortJointInterface</hardwareInterface>    </joint>    <actuator name="motor2">      <hardwareInterface>EffortJointInterface</hardwareInterface>      <mechanicalReduction>1</mechanicalReduction>    </actuator>  </transmission>

<joint name="">: URDF中关节的名称。

<type>: 变换类型。

<hardwareInterface>: 在标签<actuator> 和 <joint> 内。加载的硬件接口类型。

3、添加`gazebo_ros_control`组件

<gazebo>  <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">    <robotNamespace>/MYROBOT</robotNamespace>    <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>  </plugin></gazebo>

<robotNamespace>：当前插件的名称空间，默认为机器人所在空间。

<controlPeriod>：控制器更新的时间，默认为Gazebo时间

<robotParam>：参数服务器中机器人的描述，默认为/robot_description

<robotSimType>：机器人模拟接口的插件名字，默认为'DefaultRobotHWSim'

控制插件默认的行为包括：

hardware_interface::JointStateInterface
hardware_interface::EffortJointInterface
hardware_interface::VelocityJointInterface

3、`RRBot` 例子

1、编写材料文件

<!--materials.xacro--><?xml version="1.0"?><robot>  <material name="red">    <color rgba="0.8 0.0 0.0 1.0"/>  </material>  <material name="brown">    <color rgba="${222/255} ${207/255} ${195/255} 1.0"/>  </material></robot>

2、编写插件文件

<?xml version="1.0"?><robot>  <!-- ros_control plugin -->  <gazebo>    <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">      <robotNamespace>/rrbot</robotNamespace>      <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>    </plugin>  </gazebo>  <!-- hokuyo -->  <gazebo reference="hokuyo_link">    <sensor type="gpu_ray" name="head_hokuyo_sensor">      <pose>0 0 0 0 0 0</pose>      <visualize>false</visualize>      <update_rate>40</update_rate>      <ray>        <scan>          <horizontal>            <samples>720</samples>            <resolution>1</resolution>            <min_angle>-1.570796</min_angle>            <max_angle>1.570796</max_angle>          </horizontal>        </scan>        <range>          <min>0.10</min>          <max>30.0</max>          <resolution>0.01</resolution>        </range>        <noise>          <type>gaussian</type>          <!-- Noise parameters based on published spec for Hokuyo laser               achieving "+-30mm" accuracy at range < 10m.  A mean of 0.0m and               stddev of 0.01m will put 99.7% of samples within 0.03m of the true               reading. -->          <mean>0.0</mean>          <stddev>0.01</stddev>        </noise>      </ray>      <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_gpu_laser.so">        <topicName>/rrbot/laser/scan</topicName>        <frameName>hokuyo_link</frameName>      </plugin>    </sensor>  </gazebo>  <!-- camera -->  <gazebo reference="camera_link">    <sensor type="camera" name="camera1">      <update_rate>30.0</update_rate>      <camera name="head">        <horizontal_fov>1.3962634</horizontal_fov>        <image>          <width>800</width>          <height>800</height>          <format>R8G8B8</format>        </image>        <clip>          <near>0.02</near>          <far>300</far>        </clip>        <noise>          <type>gaussian</type>          <!-- Noise is sampled independently per pixel on each frame.                 That pixel's noise value is added to each of its color               channels, which at that point lie in the range [0,1]. -->          <mean>0.0</mean>          <stddev>0.007</stddev>        </noise>      </camera>      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">        <alwaysOn>true</alwaysOn>        <updateRate>0.0</updateRate>        <cameraName>rrbot/camera1</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>  </robot>

3、编写transation文件

见上文

4、编写xacro文件

<?xml version="1.0"?><!-- Revolute-Revolute Manipulator --><robot name="rrbot" xmlns:xacro="http://www.ros.org/wiki/xacro">  ...  <!-- Import all Gazebo-customization elements, including Gazebo colors -->  <xacro:include filename="$(find rrbot_description)/urdf/rrbot.gazebo" />  <!-- Import Rviz colors -->  <xacro:include filename="$(find rrbot_description)/urdf/materials.xacro" /> <xacro:include filename="$(find rrbot_description)/urdf/rrbot.transmission.xacro" />  <!-- Used for fixing robot to Gazebo 'base_link' -->  <link name="world"/>  <joint name="fixed" type="fixed">    <parent link="world"/>    <child link="link1"/>  </joint>  <!-- Base Link -->  <link name="link1">    <collision>      <origin xyz="0 0 ${height1/2}" rpy="0 0 0"/>      <geometry>    <box size="${width} ${width} ${height1}"/>      </geometry>    </collision>    <visual>      <origin xyz="0 0 ${height1/2}" rpy="0 0 0"/>      <geometry>    <box size="${width} ${width} ${height1}"/>      </geometry>      <material name="orange"/>    </visual>    <inertial>      <origin xyz="0 0 ${height1/2}" rpy="0 0 0"/>      <mass value="${mass}"/>      <inertia      ixx="${mass / 12.0 * (width*width + height1*height1)}" ixy="0.0" ixz="0.0"      iyy="${mass / 12.0 * (height1*height1 + width*width)}" iyz="0.0"      izz="${mass / 12.0 * (width*width + width*width)}"/>    </inertial>  </link>  <joint name="joint1" type="continuous">    <parent link="link1"/>    <child link="link2"/>    <origin xyz="0 ${width} ${height1 - axel_offset}" rpy="0 0 0"/>    <axis xyz="0 1 0"/>    <dynamics damping="0.7"/>  </joint>  <!-- Middle Link -->  ...  <joint name="hokuyo_joint" type="fixed">    <axis xyz="0 1 0" />    <origin xyz="0 0 ${height3 - axel_offset/2}" rpy="0 0 0"/>    <parent link="link3"/>    <child link="hokuyo_link"/>  </joint>  <!-- Hokuyo Laser -->  <link name="hokuyo_link">    <collision>      <origin xyz="0 0 0" rpy="0 0 0"/>      <geometry>    <box size="0.1 0.1 0.1"/>      </geometry>    </collision>    <visual>      <origin xyz="0 0 0" rpy="0 0 0"/>      <geometry>        <mesh filename="package://rrbot_description/meshes/hokuyo.dae"/>      </geometry>    </visual>    <inertial>      <mass value="1e-5" />      <origin xyz="0 0 0" rpy="0 0 0"/>      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />    </inertial>  </link>  <joint name="camera_joint" type="fixed">    <axis xyz="0 1 0" />    <origin xyz="${camera_link} 0 ${height3 - axel_offset*2}" rpy="0 0 0"/>    <parent link="link3"/>    <child link="camera_link"/>  </joint>  <!-- Camera -->  ...

5、

参考：

http://wiki.ros.org/ros_control
http://gazebosim.org/tutorials?tut=ros_control&cat=connect_ros
https://github.com/ros-simulation/gazebo_ros_demos
http://wiki.ros.org/rqt_graph
http://wiki.ros.org/rqt
http://wiki.ros.org/urdf/XML/Transmission

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