# 吊舱操作

**注意：本教程仅适用于配备吊舱的Kerloud 600无人机。**

![](/files/iwSTOvG4qRAIcbRFbawC)

吊舱是无人机在航空测绘、视频/图像监控、视觉跟踪和定位应用场景下的常见设备。我们为用户提供简化视频监控、处理的高级选项， [Kerloud 600 Pro-Cam Pod](https://cloudkerneltech.gitbook.io/kerlouduav/userguide/hardwareoptions/kerloud600_options#option-3-kerloud-600-pro-cam-pod), 该款型可用作室外监控应用开发的基点。借助已有软件环境，用户可以轻松构建自己的应用程序，例如视频传输以及使用深度学习神经网络的实时视觉识别。本教程中我们将说明如何访问机载视觉，以及如何在 ROS 环境中操作吊舱。

## 视频和图像采集

Kerloud 600 Pro-Cam Pod 中的默认相机单元支持 1080P 60fps 视频流和 10 倍光学变焦。该参数使无人机能够识别1000米内的汽车，如下图所示：

![](/files/G2mlbpMl2m9kWvKBLGZu)

我们已准备好软件环境供用户获取板载视频流和图像。要从吊舱查看实时视频，请运行以下命令：

```
    cd ~/src/catkinws_periph
    bash view_campod_video.sh
```

视频将显示如下：

![](/files/F7fsgZX861z7DIJ9bwnj)

要在ROS环境下发布在线镜像，运行命令：

```
    cd ~/src/catkinws_periph
    bash pub_campod_image.sh
```

图像主题可通过 rqt\_image\_view 命令查看：

![](/files/caVvWttoVlmwSa8slqyY)

## 吊舱动作指令

### 服务详情

默认吊舱支持的用户操作包含相机姿态命令、缩放、聚焦、视频捕获和照片拍摄。这些操作是通过路径**\~/src/catkinws\_periph/src/campod\_driver**下提供的ROS 驱动程序的服务来实现的。 下面列出了服务的详细信息，在此强烈建议用户参考驱动程序包中的 README 文件以保持最新版本。

```
    # command to turn on/off the motors
    uint8 SET_MOTOR_ON_OFF              = 0   # params[0]: 0 for turn off, 1 for turn on

    # command to set camera attitude
    uint8 SET_CAMPOD_ATTITUE            = 1   # params[0-2]: set 1 to enable roll, pitch, yaw channels in order;
                                              # params[3-5]: desired attitude angle in degrees

    # command to set camera attitude rates
    uint8 SET_CAMPOD_ATTITUDE_RATE      = 2  # params[0-2]: set 1 to enable roll, pitch, yaw channels in order;
                                              # params[3-5]: desired attitude rate in degrees

    # command to request camera attitude angles
    uint8 GET_ANGLES_EXT                = 3     # content[0-2]: responded IMU roll, pitch, yaw angles in degrees
                                             # content[3-5]: responded target roll, pitch, yaw angles in degrees
                                             # content[6-8]: responded stator rotor angles in degrees

    # request commands
    uint8 REQUEST_RETURN_HEAD           = 4
    uint8 REQUEST_CENTER_YAW            = 5
    uint8 REQUEST_LOOK_DOWN             = 6
    uint8 REQUEST_FOLLOW_YAW_DISABLE    = 7
    uint8 REQUEST_FOLLOW_YAW_ENABLE     = 8

    # camera control commands
    uint8 REQUEST_ZOOM_OUT              = 9
    uint8 REQUEST_ZOOM_IN               = 10
    uint8 REQUEST_STOP_ZOOM             = 11
    uint8 REQUEST_FOCUS_IN              = 12
    uint8 REQUEST_FOCUS_OUT             = 13
    uint8 REQUEST_STOP_FOCUS            = 14
    uint8 REQUEST_ZOOM_DIRECT_POSITION  = 15    # params[0]: zoom value within range [MIN_ZOOM_VALUE, MAX_ZOOM_VALUE]
    uint8 REQUEST_VIDEO_PHOTO_ACTION    = 16    # params[0]: 1: take a picture; 2: start recording; 3: stop recording; 4: reverse capture status;
                                                # 05: switch to video or photo mode

    uint8 cmd_id
    float32[] params
    ---
    bool success
    float32[] content
```

### 命令行中的服务调用

该服务可以通过命令行形式调用。用户必须先启动驱动程序：

```
    cd ~/src/catkinws_periph
    bash run_campod.sh
```

然后用户可以启动一个新的终端，并获取catkinws\_periph的环境：

```
    source ~/src/catkinws_periph/devel/setup.bash

    # request to set yaw target as 90 deg for the camera pod
    rosservice call /camera_pod_command "cmd_id: 1
    params: [0.0, 0.0, 1.0, 0.0, 0.0, 90.0]"
```

建议用户在终端使用 tab 键自动填写服务命令。若服务调用成功会返回成功信息，如下图：

![](/files/vREXQy3BbA8SSlv6N8EJ)

### ROS包中的服务调用

若要在另一个 ros 包中使用该服务，用户可将 campod\_driver 包复制到同一工作区，或者在为应用程序构建新工作区之前获取 catkinws\_periph 工作区。在新的 ROS 包中必须指定包依赖性，且应包含服务头。

由于吊舱驱动中提供了服务服务器，用户可以简单的按照 [ROS官方教程](http://wiki.ros.org/ROS/Tutorials/WritingServiceClient\(c%2B%2B\)) 写一个客户端，形式如下：

```
    ros::NodeHandle n;
    ros::ServiceClient client = n.serviceClient<camera_pod::Campodcmd>("camera_pod_command");
    camera_pod::Campodcmd srv;
    srv.request.cmd_id = 1;
    srv.request.params = [0.0, 0.0, 1.0, 0.0, 0.0, 90.0];

    client.call(srv);
```


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