D435i标定IMU与相机实战指南

D435i 标定 IMU 与相机以复现 VINS-Fusion

硬件与软件准备

确保设备为 Intel RealSense D435i，包含 RGB 相机和内置 IMU。安装 RealSense SDK 2.0 和 ROS Wrapper，用于数据采集。安装标定工具如 Kalibr（多传感器标定）和 IMU_Utils（IMU 内参标定）。

IMU 内参标定

IMU 内参包括噪声密度和随机游走参数。使用 IMU_Utils 工具包采集静态数据，时长建议 2 小时以上。将设备静止放置于水平表面，避免振动。运行以下命令采集数据：

rosbag record /camera/imu -O imu_calibration.bag

使用 imu_utils 处理数据生成 imu_params.yaml，包含关键参数：

accelerometer_noise_density
gyroscope_noise_density
accelerometer_random_walk
gyroscope_random_walk

相机内参标定

使用 Kalibr 标定相机内参。打印棋盘格标定板（建议 6x8 方格，边长 30mm），录制包含多角度运动的 ROS 数据包：

rosbag record /camera/infra1/image_rect_raw /camera/infra2/image_rect_raw -O camera_calibration.bag

运行标定命令：

kalibr_calibrate_cameras --target checkerboard.yaml --bag camera_calibration.bag --models pinhole-radtan pinhole-radtan --topics /camera/infra1/image_rect_raw /camera/infra2/image_rect_raw

输出文件包含相机内参矩阵和畸变系数。

IMU 与相机外参标定

使用 Kalibr 标定相机与 IMU 之间的时空参数。录制同时包含相机图像和 IMU 数据的 ROS 数据包，设备需进行充分激励运动（旋转和平移）。运行标定命令：

kalibr_calibrate_imu_camera --target checkerboard.yaml --bag dynamic_calibration.bag --cam camchain.yaml --imu imu_params.yaml --topics /camera/infra1/image_rect_raw

输出文件包含：

T_cam_imu：相机到 IMU 的变换矩阵
time_offset：时间同步偏移量

配置 VINS-Fusion

修改 VINS-Fusion 配置文件（如 realsense_stereo_imu_config.yaml）以匹配标定结果：

imu:
  imu_params: [imu_noise_density, imu_random_walk]
  extrinsic_rotation: [r11, r12, r13, r21, r22, r23, r31, r32, r33]
  extrinsic_translation: [t1, t2, t3]

确保相机内参与外参正确写入配置文件。

验证与复现

运行 VINS-Fusion 节点：

roslaunch vins vins_rviz.launch config_path:=/path/to/config.yaml

检查轨迹输出是否平滑，与真实运动一致。若出现漂移，需重新验证标定数据或调整时间同步参数。

常见问题处理

标定失败：确保运动激励充分，避免纯旋转或纯平移。
时间不同步：检查 ROS 时间戳同步，或使用 approx_sync 参数调整。
精度不足：延长标定数据采集时间，优化环境光照与标定板清晰度。

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