/mavros/setpoint_velocity/cmd_vel 不起飞

/mavros/setpoint_velocity/cmd_vel 是一个 ROS 话题，用于发送无人机的速度控制指令，但是它仅仅是一个话题，不会直接导致无人机起飞。

要让无人机起飞，需要提供一系列的指令，例如设置起飞模式、解锁无人机、设置目标高度和姿态等等。具体实现方式取决于你使用的飞控和控制方式。

在使用/mavros/setpoint_velocity/cmd_vel前，你需要确保你的无人机处于解锁状态，并且你已经正确地设置了起飞模式和控制方式。同时，你需要发送合适的速度指令，才能让无人机实现起飞。

如果你遇到了无法起飞的问题，你可以检查是否满足上述要求，并且查看控制台输出和日志文件，以便找到问题所在。

相关问题

kcf无人机跟踪小车ros代码,要求订阅/iris/usb_cam/image_raw话题，发布mavros/setpoint_position/local和/mavros/setpoint_velocity/cmd_vel_unstamped

以下是一个简单的ROS节点示例，用于使用KCF算法跟踪小车并发布位置和速度指令到MAVROS。

#!/usr/bin/env python

import rospy
from sensor_msgs.msg import Image
from cv_bridge import CvBridge
import cv2
import numpy as np
from pyimagesearch.centroidtracker import CentroidTracker
from pyimagesearch.trackableobject import TrackableObject
from geometry_msgs.msg import PoseStamped, Twist

class KCFTrackerNode:
    def __init__(self):
        rospy.init_node('kcf_tracker_node', anonymous=True)

        self.bridge = CvBridge()
        self.ct = CentroidTracker()
        self.trackers = []
        self.trackable_objects = {}

        self.image_sub = rospy.Subscriber('/iris/usb_cam/image_raw', Image, self.image_callback)
        self.position_pub = rospy.Publisher('/mavros/setpoint_position/local', PoseStamped, queue_size=1)
        self.velocity_pub = rospy.Publisher('/mavros/setpoint_velocity/cmd_vel_unstamped', Twist, queue_size=1)

        self.image_width = 640
        self.image_height = 480
        self.focal_length = 600
        self.real_width = 0.5
        self.target_width = 0.1

    def image_callback(self, data):
        cv_image = self.bridge.imgmsg_to_cv2(data, 'bgr8')

        if len(self.trackers) == 0:
            # initialize trackers
            objects = self.ct.update([(0, 0, self.image_width, self.image_height)])
            for (object_id, centroid) in objects.items():
                tracker = cv2.TrackerKCF_create()
                tracker.init(cv_image, (centroid[0], centroid[1], self.target_width * self.focal_length, self.target_width * self.focal_length))
                self.trackers.append(tracker)
                self.trackable_objects[object_id] = TrackableObject(object_id, centroid)

        else:
            # update trackers
            for tracker in self.trackers:
                success, box = tracker.update(cv_image)
                if success:
                    (x, y, w, h) = [int(v) for v in box]
                    centroid = (x + w / 2, y + h / 2)
                    object_id = self.ct.register(centroid)
                    to = self.trackable_objects.get(object_id, None)
                    if to is None:
                        to = TrackableObject(object_id, centroid)
                        self.trackable_objects[object_id] = to
                    else:
                        to.centroids.append(centroid)

        # filter out small objects
        self.trackable_objects = {k: v for k, v in self.trackable_objects.items() if len(v.centroids) > 5 and v.width() > self.image_width * 0.1}

        # update position and velocity commands
        for object_id, to in self.trackable_objects.items():
            x = (to.centroids[-1][0] - self.image_width / 2) * self.real_width / self.focal_length
            y = (to.centroids[-1][1] - self.image_height / 2) * self.real_width / self.focal_length
            z = 2.0

            pose_msg = PoseStamped()
            pose_msg.header.stamp = rospy.Time.now()
            pose_msg.pose.position.x = x
            pose_msg.pose.position.y = y
            pose_msg.pose.position.z = z
            self.position_pub.publish(pose_msg)

            vx = (to.centroids[-1][0] - to.centroids[-2][0]) * self.real_width / self.focal_length
            vy = (to.centroids[-1][1] - to.centroids[-2][1]) * self.real_width / self.focal_length
            vz = 0.0

            vel_msg = Twist()
            vel_msg.linear.x = vx
            vel_msg.linear.y = vy
            vel_msg.linear.z = vz
            self.velocity_pub.publish(vel_msg)

if __name__ == '__main__':
    try:
        node = KCFTrackerNode()
        rospy.spin()
    except rospy.ROSInterruptException:
        pass

请注意，此节点使用了pyimagesearch库中的CentroidTracker和TrackableObject类，您需要先安装此库：

pip install imutils

此外，这里的代码将图像中间作为目标点，将图像宽度的10％用作最小目标宽度，将真实世界中的实际宽度设置为0.5米。您可能需要根据您的具体应用程序进行一些修改。

ros::Publisher vel_pub = nh->advertise<geometry_msgs::TwistStamped>("/iris_0/mavros/setpoint_velocity/cmd_vel", 10);

这段代码是用于在ROS系统中创建一个Publisher对象，用于发布飞行器速度控制指令。其中，"/iris_0/mavros/setpoint_velocity/cmd_vel"是话题的名称，10是发布队列的大小，geometry_msgs::TwistStamped是消息类型，表示一个带有时间戳的Twist消息，包含线速度和角速度的信息。在发布速度控制指令时，需要将速度信息填充到TwistStamped消息中，并调用Publisher对象的publish方法来发布消息。