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一. ros_control和Gazebo的数据流向 在Gazebo中模拟机器人的控制器是可以通过使用ros_control和一个简单的Gazebo插件适配器来完成。下面是仿真,硬件,控制器和传动之间关系的概览: 一些可用的硬件接口: Joint Command Interface - Hardware interface to support commanding an array of joints. Note that these commands can have any semantic meaning as long as they each can be represented by a single double, they are not necessarily effort commands. To specify a meaning to this command, see the derived classes: Effort Joint Interface - for commanding effort-based joints. Velocity Joint Interface - for commanding velocity-based joints. Position Joint Interface - for commanding position-based joints.Joint State Interfaces - Hardware interface to support reading the state of an array of named joints, each of which has some position, velocity, and effort (force or torque).Actuator State Interfaces - Hardware interface to support reading the state of an array of named actuators, each of which has some position, velocity, and effort (force or torque).Actuator Command Interfaces: Effort Actuator Interface Velocity Actuator Interface Position Actuator InterfaceForce-torque sensor InterfaceIMU sensor Interface(2)添加gazebo_ros_control插件 除了transmission标签,也需要向你的URDF中添加Gazebo插件,它会自动解析transmission标签,装载合适的硬件接口和controller manager。一般默认的gazebo_ros_control插件是很简单的,但是它也是可以通过插件架构在ros_control和gazebo之间来扩展自定义的机器人硬件接口。 一般添加到URDF的默认插件形如: /MYROBOT这个 gazebo_ros_control的< plugin>标签有如下可选的子标签: < robotNamespace>: 插件实例所使用的ROS命名空间,默认为URDF中robot的name< controlPeriod>: 控制器的更新时钟,默认为gazebo的时钟< robotParam>: 参数服务器中robot_description的位置,默认为’/robot_description’< robotSimType>:所使用自定义机器人仿真接口的插件名字,默认为’DefaultRobotHWSim’自定义gazebo_ros_control仿真插件: 这个gazebo_ros_controlGazebo插件为仿真更加复杂机理提供了基于插件的接口来实现自定义Gazebo和ros_control之间的接口。这些插件必须继承gazebo_ros_control::RobotHWSim,它实现一个模拟的ros_control的hardware_interface::RobotHW。RobotHWSim为对Gazebo仿真器的读取和控制关节属性提供API级别的访问。 相应的RobotHWSim子类在URDF模型中指定,并且在机器人模型装载时装载。例如,下面的XML会装载默认插件: /MYROBOT gazebo_ros_control/DefaultRobotHWSim三. 例子 (1)首先在rrbot.xacro中添加< transmission>标签,同时< hardwareInterface>必须包含在< joint>和< actuator>标签中,内容如下: transmission_interface/SimpleTransmission EffortJointInterface EffortJointInterface 1 transmission_interface/SimpleTransmission EffortJointInterface EffortJointInterface 1(2)在rrbot.gazebo中添加ros_control插件 内容如下: /rrbot gazebo_ros_control/DefaultRobotHWSim(3)创建.yaml配置文件 cd ~/catkin_ws/src catkin_create_pkg rrbot_control controller_manager joint_state_controller robot_state_publisher cd rrbot_control mkdir config mkdir launch在config文件下创建一个文件rrbot_control.yaml,内容如下: rrbot: # Publish all joint states ----------------------------------- joint_state_controller: type: joint_state_controller/JointStateController publish_rate: 50 # Position Controllers --------------------------------------- joint1_position_controller: type: effort_controllers/JointPositionController joint: joint1 pid: {p: 100.0, i: 0.01, d: 10.0} joint2_position_controller: type: effort_controllers/JointPositionController joint: joint2 pid: {p: 100.0, i: 0.01, d: 10.0}保存在yaml的PID增益和控制器设置可以通过launch文件加载到参数服务器中,因此在launch文件夹创建一个rrbot_control.launch文件,内容如下: < rosparam>加载控制器配置文件到参数服务器中;节点controller_spawner通过运行一个python脚本为rrbot启动两个关节位置控制器,这个python脚本会向ros_control控制器管理者(controller manager)请求服务调用,这个服务调用会告诉controller manager你想要的是哪个控制器。同时,这个节点也加载了第三个控制器joint_state_controller,用来发布所有关节的关节状态,相应话题为“/joint_states“。 最后是启动robot_state_publisher节点,接收来自joint_state_controller的话题是"/joint_states",发布的话题是“/tf"。 (4)使用roslaunch启动控制器 首先启动rrbot仿真: roslaunch rrbot_gazebo rrbot_world.launch然后给两个关节加载控制器: roslaunch rrbot_control rrbot_control.launch 手动给控制器发布命令 rostopic pub -1 /rrbot/joint1_position_controller/command std_msgs/Float64 "data: 1.5" rostopic pub -1 /rrbot/joint2_position_controller/command std_msgs/Float64 "data: 1.0" 使用RQT发送命令 rosrun rqt_gui rqt_gui在RQT的菜单栏中“Plugins”中点击"Topics->Message Publisher"插件,然后从Topic的下拉框中选择你想要给控制器发布的话题,比如/rrbot/joint1_position_controller/command,设置结果如下(其中i是RQT的时间变量): 刚打开rviz时会报错,如下图: |
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