vel_sub = sp_nh.subscribe("cmd_vel", 10, &SetpointVelocityPlugin::vel_cb, this); vel_unstamped_sub = sp_nh.subscribe("cmd_vel_unstamped", 10, &SetpointVelocityPlugin::vel_unstamped_cb, this);
时间: 2023-06-25 15:07:48 浏览: 51
这段代码是在ROS中创建了两个subscriber对象,分别订阅了两个主题:cmd_vel和cmd_vel_unstamped。订阅的主题是机器人的速度控制命令。当有新的速度控制命令发布到这些主题时,ROS会调用对应的回调函数vel_cb和vel_unstamped_cb来处理这些数据。这里的this指针表示SetpointVelocityPlugin类的实例,也就是说,回调函数会在SetpointVelocityPlugin类的实例中执行。
相关问题
这段代码中发布的话题和消息和消息类型分别是什mavros_msgs::State current_state; void state_cb(const mavros_msgs::State::ConstPtr& msg){ current_state = *msg; } int main(int argc, char **argv) { ros::init(argc, argv, "position"); ros::NodeHandle nh; ros::Subscriber state_sub = nh.subscribe<mavros_msgs::State> ("mavros/state", 10, state_cb); ros::Publisher local_pos_pub = nh.advertise<geometry_msgs::PoseStamped> ("mavros/setpoint_position/local", 10); ros::ServiceClient arming_client = nh.serviceClient<mavros_msgs::CommandBool> ("mavros/cmd/arming"); ros::ServiceClient set_mode_client = nh.serviceClient<mavros_msgs::SetMode> ("mavros/set_mode"); //ros::Publisher velocity_pub = nh.advertise<geometry_msgs::TwistStamped> // ("mavros/setpoint_velocity/cmd_vel", 10); //the setpoint publishing rate MUST be faster than 2Hz ros::Rate rate(20.0);
这段代码使用 ROS 发布和订阅了一些话题,其中发布的消息类型是 `geometry_msgs::PoseStamped`,订阅的消息类型是 `mavros_msgs::State`,服务类型是 `mavros_msgs::CommandBool` 和 `mavros_msgs::SetMode`。
具体来说:
- 发布的话题是 `mavros/setpoint_position/local`,发布的消息类型是 `geometry_msgs::PoseStamped`。这个话题通常用于设置飞机的本地位置,即相对于起点的位置。
- 订阅的话题是 `mavros/state`,订阅的消息类型是 `mavros_msgs::State`。这个话题通常用于获取飞机的状态,例如是否上电、是否解锁、当前飞行模式等。
- 使用 `ros::Subscriber` 类型的 `state_sub` 对 `mavros/state` 进行了订阅,并指定了回调函数 `state_cb`。每当接收到 `mavros_msgs::State` 类型的消息时,就会调用回调函数 `state_cb`,将收到的消息赋值给全局变量 `current_state`。
- 使用 `ros::ServiceClient` 类型的 `arming_client` 和 `set_mode_client` 对 `mavros/cmd/arming` 和 `mavros/set_mode` 进行了服务调用。这两个服务通常用于解锁飞机和切换飞行模式。
- 使用 `ros::Rate` 类型的 `rate` 对发布频率进行了限制,设置为 20Hz。
需要注意的是,这段代码中的消息类型和话题名字可能与您的实际应用有所不同。
#include <ros/ros.h> #include <turtlesim/Pose.h> #include <geometry_msgs/Twist.h> #include <std_srvs/Empty.h> #include <cmath> ros::Publisher twist_pub; void poseCallback(const turtlesim::Pose& pose) { static bool is_forward = true; static int count = 0; static float x_start = pose.x; static float y_start = pose.y; static float theta_start = pose.theta; // Calculate distance from starting points float dist = std::sqrt(std::pow(pose.x - x_start, 2) + std::pow(pose.y - y_start, 2)); geometry_msgs::Twist twist_msg; twist_msg.linear.x = 1.0; twist_msg.linear.y = 0.0; twist_msg.linear.z = 0.0; twist_msg.angular.x = 0.0; twist_msg.angular.y = 0.0; twist_msg.angular.z = 0.0; // Check if turtle has reached distance of 2. If so, stop and shutdown the node. if (pose.x - x_start1) { twist_msg.linear.x = 0.0; twist_msg.linear.y = 1.0; twist_pub.publish(twist_msg); // Publish command if(pose.y - y_start>=2.0){ twist_msg.linear.x = -1.0; twist_msg.linear.y = 0.0; twist_pub.publish(twist_msg); // Publish command if(dist<=2.0){ twist_msg.linear.x = 0.0; twist_msg.linear.y = -1.0; twist_pub.publish(twist_msg); // Publish command ROS_INFO("Stop and Completed!"); twist_pub.publish(twist_msg); // Publish command ros::shutdown(); } } } twist_pub.publish(twist_msg); // Publish command } int main(int argc, char** argv) { ros::init(argc, argv, "lab1_node"); ros::NodeHandle nh; twist_pub = nh.advertise<geometry_msgs::Twist>("turtle1/cmd_vel", 1); ros::Subscriber pose_sub = nh.subscribe("turtle1/pose", 1, poseCallback); // reset the turtlesim when this node starts ros::ServiceClient reset = nh.serviceClient<std_srvs::Empty>("reset"); std_srvs::Empty empty; reset.call(empty); ros::spin(); // Keep node running until ros::shutdown() return 0; } 这段代码为什么不能实现乌龟沿完整矩形轨迹运动?并给出修改后的代码
这段代码不能实现乌龟沿完整矩形轨迹运动的原因是在判断乌龟是否到达目标点时的条件判断有误。具体来说,代码中的`if (pose.x - x_start1)`应该改为`if (dist >= 2.0)`,来判断乌龟是否到达了目标距离2.0。此外,代码中也缺少了对乌龟角度的控制,需要在适当的时候设置`twist_msg.angular.z`来控制乌龟的旋转。
下面是修改后的代码:
```cpp
#include <ros/ros.h>
#include <turtlesim/Pose.h>
#include <geometry_msgs/Twist.h>
#include <std_srvs/Empty.h>
#include <cmath>
ros::Publisher twist_pub;
void poseCallback(const turtlesim::Pose& pose) {
static bool is_forward = true;
static int count = 0;
static float x_start = pose.x;
static float y_start = pose.y;
static float theta_start = pose.theta;
// Calculate distance from starting points
float dist = std::sqrt(std::pow(pose.x - x_start, 2) + std::pow(pose.y - y_start, 2));
geometry_msgs::Twist twist_msg;
twist_msg.linear.x = 1.0;
twist_msg.linear.y = 0.0;
twist_msg.linear.z = 0.0;
twist_msg.angular.x = 0.0;
twist_msg.angular.y = 0.0;
twist_msg.angular.z = 0.0;
// Check if turtle has reached distance of 2. If so, stop and shutdown the node.
if (dist >= 2.0) {
twist_msg.linear.x = 0.0;
twist_msg.linear.y = 0.0;
twist_pub.publish(twist_msg); // Publish command
ROS_INFO("Stop and Completed!");
ros::shutdown();
}
twist_pub.publish(twist_msg); // Publish command
}
int main(int argc, char** argv) {
ros::init(argc, argv, "lab1_node");
ros::NodeHandle nh;
twist_pub = nh.advertise<geometry_msgs::Twist>("turtle1/cmd_vel", 1);
ros::Subscriber pose_sub = nh.subscribe("turtle1/pose", 1, poseCallback);
// reset the turtlesim when this node starts
ros::ServiceClient reset = nh.serviceClient<std_srvs::Empty>("reset");
std_srvs::Empty empty;
reset.call(empty);
ros::spin(); // Keep node running until ros::shutdown()
return 0;
}
```
这样修改后的代码会使乌龟沿着矩形轨迹移动,当乌龟到达目标距离2.0时,会停止运动并关闭节点。