ROS联合webots实战案例(三)在webots中使用ROS控制小机器人1

302
0
2021年1月20日 09时04分

在webots中使用ROS控制小机器人

 

注意:

 

  • 再学习本系列教程时,应该已经安装过ROS了并且需要有一些ROS的基本知识,本章节代码过长

 

webots版本:2020b rev1
ros版本:melodic

 

1.从官方案例入手了解基本结构

我们找一篇篇幅较短的代码,比如官方提供的 keyboard_teleop.cpp
我们先跑一下这个例程看看:

 

$ roslaunch webots_ros keyboard_teleop.launch

 

分别按方向键可以实现机器人的移动,运行后的效果:

ROS联合webots实战案例(三)在webots中使用ROS控制小机器人1插图

 

肯定会有同学会好奇,webots中的传感器或者电机是怎么通过ros获取或者控制的呢?

我们需要注意到webots在机器人控制上可以使用5种语言来控制,分别为c、c++、java、python和matlab
通过向导->新机器人控制器可以查看,打开后点击下一步界面如下:

ROS联合webots实战案例(三)在webots中使用ROS控制小机器人1插图(1)

 

但是如果使用ROS控制的话,我们不需要创建,因为官方帮我们写好了底层的控制器代码,我们直接使用就行。

 

在案例弹出的webots软件场景树中,可以看到如下:

 

ROS联合webots实战案例(三)在webots中使用ROS控制小机器人1插图(2)

 

其中有两个关键的参数:

controller:选择控制器

ROS联合webots实战案例(三)在webots中使用ROS控制小机器人1插图(3)

 

controllerArgs:控制器参数属性,如果在同一个场景中有多台使用ros控制器的机器人,配置这个参数进行区分

 

配置完后重新运行可以看到webots已经成功连接上了ros:

 

ROS联合webots实战案例(三)在webots中使用ROS控制小机器人1插图(4)

 

在终端分别运行rostopic list rosservice list可以看到所有关于传感器的函数都已经发布了

ROS联合webots实战案例(三)在webots中使用ROS控制小机器人1插图(5)

看到这里其实大家都已经知道webots和ros是怎么运行的了。

 

大家也可以通过ros的一些基本命令对topic或service进行查看

 

2.从官方案例入手了解基本源码

 

接下来看一下官方给的keyboard_teleop.cpp代码:

 

在下面的代码中我会进行注释,如遇到关键点我会标明序号,到代码下面找到对应序号查看
“` c++

 

include “ros/ros.h”

 

// webots_ros的一些数据服务[1]

 

include <webots_ros/Int32Stamped.h>

 

include <webots_ros/set_float.h>

 

include <webots_ros/set_int.h>

 

include <webots_ros/robot_get_device_list.h>

 

include <std_msgs/String.h>

 

include

 

include

 

define TIME_STEP 32

 

// 连接控制器所需的变量
static int controllerCount;
static std::vector controllerList;
static std::string controllerName;
// 机器人左右轮位置传感器
static double lposition = 0;
static double rposition = 0;
// 左轮服务客户端
ros::ServiceClient leftWheelClient;
webots_ros::set_float leftWheelSrv;
// 右轮服务客户端
ros::ServiceClient rightWheelClient;
webots_ros::set_float rightWheelSrv;
// 时限服务客户端
ros::ServiceClient timeStepClient;
webots_ros::set_int timeStepSrv;
// 键盘服务客户端
ros::ServiceClient enableKeyboardClient;
webots_ros::set_int enableKeyboardSrv;

 

// 获取在ROS网络中可获得的控制器的名称
void controllerNameCallback(const std_msgs::String::ConstPtr &name) {
controllerCount++;
controllerList.push_back(name->data);
ROS_INFO(“Controller #%d: %s.”, controllerCount, controllerList.back().c_str());
}

 

// 当用户在控制台中按下ctrl+c 返回的函数
void quit(int sig) {
enableKeyboardSrv.request.value = 0;
enableKeyboardClient.call(enableKeyboardSrv);
timeStepSrv.request.value = 0;
timeStepClient.call(timeStepSrv);
ROS_INFO(“User stopped the ‘keyboard_teleop’ node.”);
ros::shutdown();
exit(0);
}
// 键盘返回函数
void keyboardCallback(const webots_ros::Int32Stamped::ConstPtr &value) {
int key = value->data;
int send = 0;

 

switch (key) {
//方向键左键
case 314:
lposition += -0.2;
rposition += 0.2;
send = 1;
break;
//方向键右键
case 316:
lposition += 0.2;
rposition += -0.2;
send = 1;
break;
//方向键上键
case 315:
lposition += 0.2;
rposition += 0.2;
send = 1;
break;
//方向键下键
case 317:
lposition += -0.2;
rposition += -0.2;
send = 1;
break;
case 312:
ROS_INFO(“END.”);
quit(-1);
break;
default:
send = 0;
break;
}

 

leftWheelSrv.request.value = lposition;
rightWheelSrv.request.value = rposition;
if (send) {
// 判断service服务是否成功发送
if (!leftWheelClient.call(leftWheelSrv) || !rightWheelClient.call(rightWheelSrv) || !leftWheelSrv.response.success ||
!rightWheelSrv.response.success)
ROS_ERROR(“Failed to send new position commands to the robot.”);
}
return;
}

 

int main(int argc, char **argv) {

 

// 在ROS网络上创建一个名称为‘keyboard_teleop’节点
ros::init(argc, argv, “keyboard_teleop”, ros::init_options::AnonymousName);
ros::NodeHandle n;
// SIGNAL 具体可参考unix下信号[2]
signal(SIGINT, quit);

 

// 订阅model_name话题获取可用控制器的列表
ros::Subscriber nameSub = n.subscribe(“model_name”, 100, controllerNameCallback);
while (controllerCount == 0 || controllerCount < nameSub.getNumPublishers()) {
ros::spinOnce();
ros::Duration(0.5).sleep();
}
ros::spinOnce();

 

// 如果存在大于一个控制器,需要让用户选择控制器
if (controllerCount == 1)
controllerName = controllerList[0];
else {
int wantedController = 0;
std::cout << “Choose the # of the controller you want to use:\n”;
std::cin >> wantedController;
if (1 <= wantedController && wantedController <= controllerCount)
controllerName = controllerList[wantedController – 1];
else {
ROS_ERROR(“Invalid number for controller choice.”);
return 1;
}
}
nameSub.shutdown();
// 服务设置
leftWheelClient = n.serviceClient(controllerName + “/left_wheel/set_position”);
rightWheelClient = n.serviceClient(controllerName + “/right_wheel/set_position”);
timeStepClient = n.serviceClient(controllerName + “/robot/time_step”);
timeStepSrv.request.value = TIME_STEP;

 

enableKeyboardClient = n.serviceClient(controllerName + “/keyboard/enable”);
enableKeyboardSrv.request.value = TIME_STEP;
// 判断是否成功发送数据
if (enableKeyboardClient.call(enableKeyboardSrv) && enableKeyboardSrv.response.success) {
ros::Subscriber sub_keyboard;
sub_keyboard = n.subscribe(controllerName + “/keyboard/key”, 1, keyboardCallback);
while (sub_keyboard.getNumPublishers() == 0) {
}
ROS_INFO(“Keyboard enabled.”);
ROS_INFO(“Use the arrows in Webots window to move the robot.”);
ROS_INFO(“Press the End key to stop the node.”);

// main loop
while (ros::ok()) {
ros::spinOnce();
if (!timeStepClient.call(timeStepSrv) || !timeStepSrv.response.success)
ROS_ERROR(“Failed to call service time_step for next step.”);
}

 

} else
ROS_ERROR(“Could not enable keyboard, success = %d.”, enableKeyboardSrv.response.success);

 

enableKeyboardSrv.request.value = 0;
if (!enableKeyboardClient.call(enableKeyboardSrv) || !enableKeyboardSrv.response.success)
ROS_ERROR(“Could not disable keyboard, success = %d.”, enableKeyboardSrv.response.success);
timeStepSrv.request.value = 0;
timeStepClient.call(timeStepSrv);
ros::shutdown();
return (0);
}

 


[1]
这个表格描述了ROS和Webots设备之间的服务
service name|service definition
------------|------------
get_bool|bool ask <br>---<br>bool value
get_float|bool ask<br>---<br>float64 value
get_float_array|bool ask<br>---<br>float64[] values
get_int|bool ask<br>---<br>int32 value
get_string|bool ask<br>---<br>string value
get_uint64|bool ask<br>---<br>uint64 value
set_bool|bool value<br>---<br>bool success
set_float|float64 value<br>---<br>bool success
set_float_array|float64[] values<br>---<br>bool success
set_int|int32 value<br>---<br>bool success
set_string|string value<br>---<br>bool success

[2]
因为这个不是我们具体的内容,想了解的同学可以看:
[Unix信号详解(Signal的信号说明)](https://blog.csdn.net/github_33873969/article/details/77744382)

## 3.控制前配置
1. 创建功能包
``` shell
$ cd ~/.catkin_ws/src
$ catkin_create_pkg webots_demo std_msgs rospy roscpp sensor_msgs
  1. 编译功能包
    $ cd ~/.catkin_ws
    $ catkin_make
    
  2. 移植webots_ros的srv和msg文件夹
    进入/usr/local/webots/projects/default/controllers/ros/include/文件夹下面的srvmsg文件夹复制刚刚创建的webots_demo功能包内
  3. 配置CMakeList.txt文件
    “` CMake
    cmake_minimum_required(VERSION 2.8.3)
    project(webots_demo)

 

find_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs sensor_msgs message_generation)

#

Declare ROS messages and services

 

#

Generate messages in the ‘msg’ folder

 

add_message_files(
FILES
BoolStamped.msg
Float64Stamped.msg
Int32Stamped.msg
Int8Stamped.msg
RadarTarget.msg
RecognitionObject.msg
StringStamped.msg
)

 

Generate services in the ‘srv’ folder

 

add_service_files(
FILES
camera_get_focus_info.srv
camera_get_info.srv
camera_get_zoom_info.srv
display_draw_line.srv
display_draw_oval.srv
display_draw_pixel.srv
display_draw_polygon.srv
display_draw_rectangle.srv
display_draw_text.srv
display_get_info.srv
display_image_copy.srv
display_image_delete.srv
display_image_load.srv
display_image_new.srv
display_image_paste.srv
display_image_save.srv
display_set_font.srv
field_get_bool.srv
field_get_color.srv
field_get_count.srv
field_get_float.srv
field_get_int32.srv
field_get_node.srv
field_get_rotation.srv
field_get_string.srv
field_get_type.srv
field_get_type_name.srv
field_get_vec2f.srv
field_get_vec3f.srv
field_import_node.srv
field_import_node_from_string.srv
field_remove_node.srv
field_remove.srv
field_set_bool.srv
field_set_color.srv
field_set_float.srv
field_set_int32.srv
field_set_rotation.srv
field_set_string.srv
field_set_vec2f.srv
field_set_vec3f.srv
get_bool.srv
get_float_array.srv
get_float.srv
get_int.srv
get_string.srv
get_uint64.srv
get_urdf.srv
gps_decimal_degrees_to_degrees_minutes_seconds.srv
lidar_get_frequency_info.srv
lidar_get_info.srv
lidar_get_layer_point_cloud.srv
lidar_get_layer_range_image.srv
motor_set_control_pid.srv
mouse_get_state.srv
node_add_force_or_torque.srv
node_add_force_with_offset.srv
node_get_center_of_mass.srv
node_get_contact_point.srv
node_get_field.srv
node_get_id.srv
node_get_number_of_contact_points.srv
node_get_name.srv
node_get_orientation.srv
node_get_parent_node.srv
node_get_position.srv
node_get_static_balance.srv
node_get_status.srv
node_get_type.srv
node_get_velocity.srv
node_remove.srv
node_reset_functions.srv
node_move_viewpoint.srv
node_set_visibility.srv
node_set_velocity.srv
pen_set_ink_color.srv
range_finder_get_info.srv
receiver_get_emitter_direction.srv
robot_get_device_list.srv
robot_set_mode.srv
robot_wait_for_user_input_event.srv
save_image.srv
set_bool.srv
set_float.srv
set_float_array.srv
set_int.srv
set_string.srv
skin_get_bone_name.srv
skin_get_bone_orientation.srv
skin_get_bone_position.srv
skin_set_bone_orientation.srv
skin_set_bone_position.srv
speaker_is_sound_playing.srv
speaker_speak.srv
speaker_play_sound.srv
supervisor_get_from_def.srv
supervisor_get_from_id.srv
supervisor_movie_start_recording.srv
supervisor_set_label.srv
supervisor_virtual_reality_headset_get_orientation.srv
supervisor_virtual_reality_headset_get_position.srv
)

 

Generate added messages and services with any dependencies listed here

 

generate_messages(
DEPENDENCIES
std_msgs
sensor_msgs
)

 

#

catkin specific configuration

 

#

catkin_package(
CATKIN_DEPENDS roscpp rospy std_msgs sensor_msgs message_runtime
)

 

#

Build

 

#

include_directories(
${catkin_INCLUDE_DIRS}
)

 

Instructions for keyboard_teleop node

 

#

Install

 

#
5. 配置`package.xml`文件,添加:
``` xml
<build_depend>message_generation</build_depend>
<exec_depend>message_runtime</exec_depend>
  1. webots_demo功能包内创建worlds文件夹,并且将第二章创建的机器人地图放在worlds文件夹中,方便我们直接调用。
  2. 修改webots中机器人控制器:
    6
  3. webots_demo功能包内创建launch文件夹,并且创建一个名为webots.launch的launch文件,代码如下
    (因为笔者之前在单独开启webots后,即使成功连接上了ros网络,但是依旧无法控制,使用launch文件可以解决这个问题)

    <?xml version="1.0"?>
    <launch>
    <!-- 启动webots -->
    <arg name="no-gui" default="false," doc="Start Webots with minimal GUI"/>
    <include file="$(find webots_ros)/launch/webots.launch">
     <arg name="mode" value="realtime"/>
     <arg name="no-gui" value="$(arg no-gui)"/>
     <arg name="world" value="$(find webots_demo)/worlds/webots_map.wbt"/>
    </include>
    </launch>
    

    4.编写键盘控制机器人的程序

    “` c++

    include

    include <std_msgs/String.h>

    include “ros/ros.h”

include <webots_ros/set_float.h>

include <webots_ros/set_int.h>

include <webots_ros/Int32Stamped.h>

using namespace std;

define TIME_STEP 32 //时钟

define NMOTORS 2 //电机数量

define MAX_SPEED 2.0 //电机最大速度

ros::NodeHandle *n;

static int controllerCount;
static vector controllerList;

ros::ServiceClient timeStepClient; //时钟通讯客户端
webots_ros::set_int timeStepSrv; //时钟服务数据

ros::ServiceClient set_velocity_client; //速度设置客户端
webots_ros::set_float set_velocity_srv; //速度设置数据

ros::ServiceClient set_position_client; //位置设置客户端
webots_ros::set_float set_position_srv; //位置设置数据

double speeds[NMOTORS]={0.0,0.0}; //电机速度值 0~100

// 匹配电机名
static const char _motorNames[NMOTORS] ={“left_motor”, “right_motor”};
/**_

  • Function name :updateSpeed
  • Description :将速度请求以set_float的形式发送给set_velocity_srv
  • Parameter :无
  • Return :无
    **/
    void updateSpeed() {
    for (int i = 0; i < NMOTORS; ++i) {

      // 更新速度
      set_velocity_client = n->serviceClient<webots_ros::set_float>(string("/robot/") + string(motorNames[i]) + string("/set_velocity"));   
      set_velocity_srv.request.value = -speeds[i];
      set_velocity_client.call(set_velocity_srv);
    

    }
    }

/_*_

  • Function name :controllerNameCallback
  • Description :控制器名回调函数,获取当前ROS存在的机器人控制器
  • Parameter :
      @name   控制器名
    
  • Return :无
    **/
    void controllerNameCallback(const std_msgs::String::ConstPtr &name) {
    controllerCount++;
    controllerList.push_back(name->data);//将控制器名加入到列表中
    ROS_INFO(“Controller #%d: %s.”, controllerCount, controllerList.back().c_str());

}
/_*_

  • Function name :quit
  • Description :退出函数
  • Parameter :
      @sig   信号
    
  • Return :无
    **/
    void quit(int sig) {
    ROS_INFO(“User stopped the ‘/robot’ node.”);
    timeStepSrv.request.value = 0;
    timeStepClient.call(timeStepSrv);
    ros::shutdown();
    exit(0);
    }
    /_*_
  • Function name :键盘返回函数
  • Description :当键盘动作,就会进入此函数内
  • Parameter :
      @value   返回的值
    
  • Return :无
    **/
    void keyboardDataCallback(const webots_ros::Int32Stamped::ConstPtr &value)
    {
    // 发送控制变量
    int send =0;
    //ROS_INFO(“sub keyboard value = %d”,value->data);
    switch (value->data)
    {

      // 左转
      case 314:
          speeds[0] = 5.0;
          speeds[1] = -5.0;
          send=1;
          break;
      // 前进
      case 315:
          speeds[0] = 5.0;
          speeds[1] = 5.0;
          send=1;
          break;
      // 右转
      case 316:
          speeds[0] = -5.0;
          speeds[1] = 5.0;
          send=1;
          break;
      // 后退
      case 317:
          speeds[0] = -5.0;
          speeds[1] = -5.0;
          send=1;
          break;
      // 停止
      case 32:
          speeds[0] = 0;
          speeds[1] = 0;
          send=1;
          break;
      default:
          send=0; 
          break;
    

    }
    //当接收到信息时才会更新速度值
    if (send)
    {

      updateSpeed();
      send=0;
    

    }
    }

int main(int argc, char **argv) {
setlocale(LC_ALL, “”); // 用于显示中文字符
string controllerName;
// 在ROS网络中创建一个名为robot_init的节点
ros::init(argc, argv, “robot_init”, ros::init_options::AnonymousName);
n = new ros::NodeHandle;
// 截取退出信号
signal(SIGINT, quit);

// 订阅webots中所有可用的model_name
ros::Subscriber nameSub = n->subscribe("model_name", 100, controllerNameCallback);
while (controllerCount == 0 || controllerCount < nameSub.getNumPublishers()) {
    ros::spinOnce();
    ros::spinOnce();
    ros::spinOnce();
}
ros::spinOnce();
// 服务订阅time_step和webots保持同步
timeStepClient = n->serviceClient<webots_ros::set_int>("robot/robot/time_step");
timeStepSrv.request.value = TIME_STEP;

// 如果在webots中有多个控制器的话,需要让用户选择一个控制器
if (controllerCount == 1)
    controllerName = controllerList[0];
else {
    int wantedController = 0;
    cout << "Choose the # of the controller you want to use:\n";
    cin >> wantedController;
    if (1 <= wantedController && wantedController <= controllerCount)
    controllerName = controllerList[wantedController - 1];
    else {
    ROS_ERROR("Invalid number for controller choice.");
    return 1;
    }
}
ROS_INFO("Using controller: '%s'", controllerName.c_str());
// 退出主题,因为已经不重要了
nameSub.shutdown();

//初始化电机
for (int i = 0; i < NMOTORS; ++i) {
    // position速度控制时设置为缺省值INFINITY   
    set_position_client = n->serviceClient<webots_ros::set_float>(string("/robot/") + string(motorNames[i]) + string("/set_position"));   
    set_position_srv.request.value = INFINITY;
    if (set_position_client.call(set_position_srv) && set_position_srv.response.success)     
        ROS_INFO("Position set to INFINITY for motor %s.", motorNames[i]);   
    else     
        ROS_ERROR("Failed to call service set_position on motor %s.", motorNames[i]);
    // velocity初始速度设置为0   
    set_velocity_client = n->serviceClient<webots_ros::set_float>(string("/robot/") + string(motorNames[i]) + string("/set_velocity"));   
    set_velocity_srv.request.value = 0.0;   
    if (set_velocity_client.call(set_velocity_srv) && set_velocity_srv.response.success == 1)     
        ROS_INFO("Velocity set to 0.0 for motor %s.", motorNames[i]);   
    else     
        ROS_ERROR("Failed to call service set_velocity on motor %s.", motorNames[i]);
}   


// 服务订阅键盘
ros::ServiceClient keyboardEnableClient;
webots_ros::set_int keyboardEnablesrv;

keyboardEnableClient = n->serviceClient<webots_ros::set_int>("/robot/keyboard/enable");
keyboardEnablesrv.request.value = TIME_STEP;
if (keyboardEnableClient.call(keyboardEnablesrv) && keyboardEnablesrv.response.success)
{
    ros::Subscriber keyboardSub;
    keyboardSub = n->subscribe("/robot/keyboard/key",1,keyboardDataCallback);
    while (keyboardSub.getNumPublishers() == 0) {}
    ROS_INFO("Keyboard enabled.");
    ROS_INFO("control directions:");
    ROS_INFO("  ↑  ");
    ROS_INFO("← ↓ →");
    ROS_INFO("stop:space");
    ROS_INFO("Use the arrows in Webots window to move the robot.");
    ROS_INFO("Press the End key to stop the node.");
    while (ros::ok()) {   
        ros::spinOnce();
        if (!timeStepClient.call(timeStepSrv) || !timeStepSrv.response.success)
        {  
            ROS_ERROR("Failed to call service time_step for next step.");     
            break;   
        }   
        ros::spinOnce();
    } 
}
else
ROS_ERROR("Could not enable keyboard, success = %d.", keyboardEnablesrv.response.success);
//退出时时钟清零
timeStepSrv.request.value = 0;
timeStepClient.call(timeStepSrv);
ros::shutdown(); 
return 0;

}



## 5.最后
1. 配置`CMakeList.txt`,在最下面添加:
``` CMake
add_executable(velocity_keyboard src/velocity_keyboard.cpp)
add_dependencies(velocity_keyboard webots_ros_generate_messages_cpp)
target_link_libraries(velocity_keyboard    ${catkin_LIBRARIES})
  1. 编译功能包
    $ cd ~/.catkin_ws
    $ catkin_make
    
  2. 运行launch文件,可能不会那么快可以TAB出来,打进去一样可以运行
    $ roslaunch webots_demo webots.launch
    
  3. 运行编写好的代码
    $ rosrun webots_demo velocity_keyboard
    
  4. 效果
    ROS联合webots实战案例(三)在webots中使用ROS控制小机器人1插图(7)

结语

本文也是基于笔者的学习和使用经验总结的,主观性较强,如果有哪些不对的地方或者不明白的地方,欢迎评论区留言交流~
用手柄控制机器人的操作会单独写个文档发出来哦~~
下一节加入雷达试试吧。

Bye

发表评论

后才能评论